Polymer Flooding for Enhanced Oil Recovery: History and Advancements

This report investigates and evaluates polymer flooding as a chemical injection technique for enhanced oil recovery. It covers the mechanism, plan, and parameters to consider before implementation. It also explores alternative technologies, polymer manufacture and characteristics, core flooding, and design and implementation. The report analyzes the pros, cons, and applications of polymer flooding.

APPLICATION OF POLYMER FLOODING FOR ENHANCED OIL
RECOVERY
(History and Advancements in the Polymer Flooding Technique for Enhanced
Oil Recovery)
[Author Name(s), First M. Last, Omit Titles and Degrees]
Date:
Author Note
[Include any grant/funding information and a complete correspondence address.]
i

DISCLAIMER
I am aware of plagiarism and its penalty and hereby declare that this is my work unless otherwise
referenced as per the APA guides.
ii

ACKNOWLEDGEMENT
I am grateful to my lecturers for their steadfast guidance, time, encouragement and insight
throughout this research. To my friends and family, am greatly indebted to you for your
unwavering support. Without you, this project would be a pipe dream.
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TABLE OF CONTENTS
DISCLAIMER.....................................................................................................................ii
ACKNOWLEDGEMENT..................................................................................................iii
TABLE OF CONTENTS....................................................................................................iv
LIST OF FIGURES............................................................................................................ix
LIST OF TABLES...............................................................................................................x
ABSTRACT.......................................................................................................................xi
CHAPTER ONE..................................................................................................................1
1.1 Motivation......................................................................................................................1
1.2 Proposal.........................................................................................................................1
1.3 Research and Developments..........................................................................................4
CHAPTER TWO.................................................................................................................5
POLYMER FLOODING MECHANISM............................................................................5
2.1 Mechanism of the Polymer Flooding............................................................................5
2.2 Effecting Polymer Flooding Technique.........................................................................6
2.3 Oil Recovery Improvement by Polymer Flooding........................................................7
2.4 Polymer Flooding Plan..................................................................................................8
2.4.1 Polymer Injection....................................................................................................8
2.4.2 Timing.....................................................................................................................9
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2.4.3 Screening Criteria for Polymer Application.........................................................10
2.4.4 Parameters to Consider before the Implementation of Polymer Flooding...........13
CHAPTER THREE...........................................................................................................14
RESEARCH METHODOLOGY......................................................................................14
Introduction........................................................................................................................14
Research Approach........................................................................................................14
Data collection...............................................................................................................17
CHAPTER FOUR.............................................................................................................18
ALTERNATIVE TECHNOLOGIES.................................................................................18
4.1 Surfactant-Polymer (SP) and Alkali-surfactant polymer (ASP)..................................18
4.2 Gels and Derivatives....................................................................................................18
4.3 Types of polymers........................................................................................................20
4.3.1 Biopolymers..........................................................................................................20
4.3.1.1 Xanthan gum..................................................................................................20
Juices: Made from 5 to 13% dynamic substance in a watery arrangement that
comprise of biocide................................................................................................................21
Powder: dry type of dynamic substance more noteworthy than 90%.......................21
4.3.1.2 Schizopyllan..................................................................................................21
4.3.2 Synthetic Polymers...............................................................................................22
4.3.2.1 Partially Hydrolyzed Polyacrylamide............................................................22
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CHAPTER FIVE...............................................................................................................23
POLYMER MANUFACTURE AND CHARACTERISTICS...........................................23
5.1 Chemical Paths Used to Manufacture the Polymers....................................................23
5.2 Polymer Characteristics...............................................................................................25
5.2.1 Viscosity................................................................................................................25
5.2.2 Rheology...............................................................................................................27
5.2.3 Stability Test.........................................................................................................28
5.2.4 Solubility...............................................................................................................28
CHAPTER SIX..................................................................................................................30
CORE FLOODING AND POLYMER DEGRADATION................................................30
6.1 Core flooding...............................................................................................................30
6.1.1 Objectives of Polymer Core Flooding Testing.....................................................30
6.2 Polymer Degradation...................................................................................................32
6.2.1 Chemical Degradation..........................................................................................33
6.2.1.1 Oxygen...........................................................................................................34
6.2.1.2 Iron.................................................................................................................34
6.2.2 Mechanical Degradation.......................................................................................34
6.2.3 Thermal Degradation............................................................................................35
CHAPTER SEVEN...........................................................................................................37
DESIGN AND IMPLEMENTATION...............................................................................37
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7.1 Polymer Flooding: Design and Implementation..........................................................37
7.2 Tracer Test....................................................................................................................38
7.3 Importance of Water Quality........................................................................................39
7.4 Pilot Injection Monitoring...........................................................................................40
7.5 Considerations Made During Pilot Polymer Flooding Implementation and
Monitoring.........................................................................................................................40
7.6 Injectivity.....................................................................................................................41
7.7 Numerical Modelling and Simulation.........................................................................43
7.8 Quality Control............................................................................................................43
7.9 Back Produced Polymer..............................................................................................44
7.10 Models that can be used in Polymer Flooding Simulation........................................46
STARS (CMG) Software...............................................................................................46
Mathematical Model......................................................................................................47
MATLAB Reservoir Simulation Toolbox (MRST) Model............................................47
7.11 Comparison of the effects of the various viscosity ratios on polymer flooding........48
CHAPTER 8......................................................................................................................51
CONCLUSION..................................................................................................................51
BIBLIOGRAPHY..............................................................................................................52
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viii

LIST OF FIGURES
Figure 1: Fingering effect prompted by the unfavorable mobility ratio .........................................3
Figure 2: Mechanism of polymer flooding technique.....................................................................6
Figure 3: Water breakthrough can be delayed and sweep efficiency...............................................7
Figure 4: Production profiles for water flood and polymer flood showing the economic limit......8
Figure 5: Comparison between polymer flood and gel systems....................................................16
Figure 6: Molecular structure of Xanthan gum.............................................................................17
Figure 7: Chemical Structure of glucan.........................................................................................18
Figure 8: Inverse emulsion system................................................................................................19
Figure 9: Overview of copolymerization process..........................................................................20
Figure 10: Overview of the post hydrolysis process.....................................................................21
Figure 11: Example of acrylamide and sodium acrylate copolymer..............................................22
Figure 12: Example of acrylamide. ATBS copolymer...................................................................22
Figure 13: Viscosity of several polymers as a function of concentration......................................23
Figure 14. Viscosity versus temperature for several polymers......................................................24
Figure 15: Types of fluids and their characteristics.......................................................................25
Figure 16: Viscosity profile for a non-typical non-Newtonian polyacrylamide fluid...................25
Figure 17: Typical glove box set-up to perform tests in anaerobic conditions..............................26
Figure 18: Mechanisms of polymer retention................................................................................30
Figure 19: Polymer degradation in presence of oxygen and iron 2 in 7.086g/L TDS brine..........31
Figure 20: Shear degradation and percentage of viscosity loss for polymers...............................33
Figure 21: Hydrolysis of acrylamide moieties along the polymer backbone................................34
Figure 22: Salt tolerance of different polymers.............................................................................34
Figure 23: Typical set-up used to perform filter ratio tests with vessel and graduated cylinders..43
Figure 24: Mechanical degradation of polymer solutions at different concentrations..................45
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LIST OF TABLES
Table 1: Screening criteria for polymer flooding according to Chang..........................................11
Table 2: Screening criteria for polymer flooding according to Sorbie..........................................12
Table 3: Current screening criteria for polymer flooding application...........................................13
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ABSTRACT
The modern day world is run by oil as a basic production commodity. The oil demand is high as
many technological processes require a fuel source and oil provides cheap and efficient fuel
enough to sustain the operations. In addition, due to the increase in population, there has been
need to increase the production of oil to cater for the deficit. As a result, several methods have
been invented to increase oil extraction. Upgraded oil recuperation includes techniques that are
utilized to help the amount of unrefined petroleum that is extricated from a given oil field. Three
noteworthy methods have been verified to function with the end goal to upgrade the oil
recuperation. They are concoction infusion, gas infusion alongside warm recuperation. In
comparison with the primary and secondary recovery methods which increase oil extraction by
20 to 40 percent, the enhanced oil recovery method has proven to be more effective since it
increases the oil extracted by about 30 and 60 percent. Chemical injection involves the use of
chemical substances that increase the weight of water and subsequently increase the pressure in
the oil fields hence facilitating increased oil extraction. Long chain polymers are mostly used in
the chemical injection enabling the oil recovery process. This report thesis therefore seeks to
investigate and evaluate polymer flooding as a chemical injection technique. In brief, polymer
flooding involves mixing of infused water using long chain polymer atoms that builds the
thickness of the water. This strategy progresses proficiency of areal as well as vertical breadth
that comes because of an improved proportion of water-oil portability. Due to the surface tension
that exists between the water and oil, surfactants may be used together with the polymers. This
aids in lowering the surface tension as well as saturation of residual oil besides in boosting the
macroscopic efficiency of the whole process. To boost the formulation’s stability, primary
surfactants with activity boosters and co-solvents are added to the mix. Polymer flooding is a
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successful oil recovery technique. This report therefore seeks to analyze the process of polymer
flooding while evaluating its pros, cons and applications.
Keywords: enhanced oil recovery, polymer flooding, chemical injection, surfactants.
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CHAPTER ONE
1.1 Motivation
Oil is the leading source of energy in the world whose significance cannot be
underestimated. It is a hydrocarbon fuel that is used in many processes from basic home living to
the running of large industrial plant processes. Due to the high demand of oil, it is approximated
that 101 billion barrels, 16 trillion litres, of oil are consumed daily all around the world and
hence, this means that increased amounts of oil have to be drilled to sustain this demand
(Zerkalov, 2015). According to Floeger, it is approximated that 2.0 ×1012 barrels of crude oil and
5.0 ×1012 barrels of heavy oil all around the world used to remain in reservoirs of oil after
conventional recovery methods are applied on the oil fields, which attest to their inefficiency.
(SNF Floeger, 2014)
1.2 Proposal
In a bid to cope with the increasing demand for hydrocarbon energy as a result of
increase in population and technological advancements, there is need to extract the untapped
barrels of oil that remain in the reservoirs. A number of techniques have been implemented to
extract this oil and quench the demand for the hydrocarbon fuel. Secondary methods such as
water or gas injection have been developed and used. This method works by maintaining the
reservoir pressure in order to ensure constant flow of crude oil to the production well. However,
with this secondary technique, about 40% of oil originally in place (OOIP) still remains in the
reservoirs. This therefore implies that there is still a huge percentage of untapped oil from the oil
reservoirs in the field despite this recovery technique usage. As a result of the flaw, it triggered
research from scientists in a bid to comprehend why the method was not as effective as they had
anticipated it would be. The research showed that the water-oil mobility ratio was unfavourable
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due to the fact that the technique did not sweep oil completely from the reservoir. Thus, not
enough oil is pushed to the production wells and hence, a huge percentage still remains
untapped.
According to Zerkalov “Mobility ratio is the ratio of mobility of the displacing fluid
(water) to the mobility of the displaced fluid (oil); where mobility is permeability divided by
viscosity” (Zerkalov, 2015)
M= λ Water / λ Oil = (K water / μ water) / (K oil / μ oil)
A reciprocal relation linking the volumetric sweep efficiency with of water-oil mobility
ratio is observed from the formula. Zerkalov discusses a phenomenon known as viscous
fingering effect which comes about when value of mobility (M) is greater than the unity. Viscous
fingering effect is therefore the instability in the displacement process that comes about due to
the unfavourable imbalance in the mobility and unity. A significant difference in viscosity
between the displacing water using reduced viscosity with that of displaced oil with higher
viscosity results in poor recovery. Poor recovery comes about when the mobility ratio is more
than one (Zerkalov, 2015). The fingering effect is undoubtedly unwanted as it decreases the
production significantly as soon as the finger gets to the production well. A solution to the poor
recovery would therefore be to reduce the mobility ratio to less than one by introducing a long
chain polymer that increases the viscosity of the displacing fluid. This in turns distributes the
displacing fluid in a stable invariable fashion thus decreasing the chances of fingering outcome
thus boosting the oil recovery process.
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Figure 1: Fingering effect prompted by the adverse water-oil mobility ratio (Top) and good oil recovery
made possible by using polymer loading (Bottom).Available from:
http://large.stanford.edu/courses/2015/ph240/zerkalov1/
1.3 Research and Developments.
A series of researches by scientists and oil experts led to the discovery of the tertiary oil
recovery methods that proved to boost the oil extraction process by 60% from the reservoir (SNF
Floeger, 2014). This percentage was excellent as it would be able to keep up with the increasing
demand for the oil by the growing population. Polymer flooding which is a type of chemical
recovery technique under tertiary methods has been used for over four decades in commercial
application. In the early 80’s, the US government issued tax incentives to companies that would
apply the polymer flooding technique to enhance oil recovery. Many companies therefore picked
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up the technique and began to implement it in the oil extraction which boosted oil extraction
from the oil fields.
However, due to the lack of comprehensive reservoir studies prior to the technique
implementation, it resulted to an epic failure and a subsequent abandonment of this oil recovery
method. In the 90`s however, China displayed an interest in reviving the polymer flooding
technique with the Daqing oil field (SNF Floeger, 2014). In 1992, SNF constructed the then
world`s largest polyacrylamide manufacturing plant in Daqing for the National Oil Company of
China. As a precautionary measure, research had to be carried out to first understand what led to
the initial failure which could then be used to make decisions on how to go forth with it. The
drillers got comprehensive reports after the research after which the actual polymer flooding
started in 1996 with more than 3000 oil wells in China adopting the polymer flooding technique.
As a result, there was a 12% OOIP increment in oil recovery that lured other companies to re-
embrace the technique. Since then, many research studies have been done and the method has
been improving making it an excellent tertiary recovery method.
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CHAPTER TWO
POLYMER FLOODING MECHANISM
2.1 Mechanism of the Polymer Flooding
According to Zerkalov, polymer flooding involves adding polymers to water, increasing
the viscosity and reducing water permeability, thus reducing the polymers ability to move. This
process aims at reducing the surface tension between oil as well as moisture which is achieved
by mixing the water pumped with surfactants. This also varies the reservoir rock wettability
which In turn improves its recovery. The long chain polymer is then removed with water and is
thereafter administered continuously for an elongated period of time (usually months) on the oil
reservoir field. When about 30% to 50% of the oil field has been injected with the long chain
polymer, the inclusion of the polymer seizes and thereafter, the drive water is pumped into the
injection well. This water under high pressure is the one that drives both the polymer slug
together with the oil bank in front of it towards the oil production well and huge amounts of oil
can be obtained from the oil wells (Zerkalov, 2015).
Figure 2: Mechanism of polymer flooding technique. Available from: https://2.bp.blogspot.com/-
rqBiF8H0fr4/Vuwla0iBUGI/AAAAAAAAALs/aKykRACXwKsVShjrthK8yAnps9uB1wpmw/s1600/
enhancedoil.pn
2.2 Effecting Polymer Flooding Technique
Trapping of oil by capillary forces or bypassing of the oil results in lots of oil left trapped
in a water flood technique (Sorbie, 1991). Polymer flooding therefore decreases the bypassing
5

effect by decreasing the mobility ration to below one. According to (Willhite & Green, 1998) the
polymer flooding is effected in two scenarios:
 During the process of water surge when the portability proportion wind up troublesome,
it presents that the polymer constantly improves the proficiency of oil clear in the
repository.
 When the reservoir shows signs of heterogeneity between the water and oil despite an
excellent water-oil mobility ratio, polymer flooding can help in the minimization of the
water mobility in the highly permeable layers that support the replacement of the oil from
the bottom permeable layers (Leonhardt et al., 2011).
Figure 3: Polyacrylamide increases the offered fluid viscosity, thereby increasing the sweep
efficiency and decelerating water breakthrough. Available from:
https://www.intechopen.com/books/chemical-enhanced-oil-recovery-ceor-a-practical-
overview/polymer-flooding
In the first diagram, an inefficient macroscopic displacement is seen. This advances
premature headway of water proceeded by a two phase production period using improving water
cuts. The second figure shows that besides the mobility ratio being equivalent or less than 1, the
availability of great pervious pipes or extensive layering of scale of supply as well as
heterogeneities can antagonistically obliterate the effectiveness of vertical as well as areal
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breadth amid water organization. Presence of highly permeable coat also leads to forward water
breakthrough. To enhance the viscosity of injected water, polymers are adopted in such
situations, thus resulting in great improvements of the layers. For this reason, the nature and
traits of the reservoir should be considered while choosing the perfect polymer for injection
purposes.
2.3 Oil Recovery Improvement by Polymer Flooding
Improving the oil recovery to huge amounts is an important parameter in polymer
flooding as compared to water flooding. Two approaches can be applied for this purpose. In the
first approach, polymer flooding creates the movable oil but does not alter the residual saturation.
Therefore, the final recovered oil in this approach is expected to be equal between a water and
polymer flood. However, the time taken in undertaking the procedures differs in the two
methods. Nonetheless, this strategy colossally depends on particular repository qualities as the
presence of particular heterogeneities would profoundly confine water from experiencing
mobility over the entire supply thus some oil would be deserted behind. Polymers may have
various effects on the residual oil saturation according to studies done by (Wang et al., 2011;
Delshad et al., 2008).
Figure 4: Water flood production profiles alongside polymer flood showing the economy limits. Available
from: https://www.intechopen.com/books/chemical-enhanced-oil-recovery-ceor-a-practical-
overview/polymer-flooding
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Polymers may cause a decrease in the remaining oil saturation hence, recovering more oil
in excess of what a simple water flood might have produced regardless of the time taken a
phenomenon called visco-elasticity.
2.4 Polymer Flooding Plan.
2.4.1 Polymer Injection.
It is not defined in researches how much of the polymer needs to be introduced into a
reservoir. The amount used is experience based and it is approximated to be at least 30% of the
reservoir capacity. This results in results as follows:
 Viscosity incline till analyze reaction of repository besides its conceivable increment in
the weight toward the start. Infusion of bigger pore volume improves the productivity
amid as well as after polymer infusion. After infusion of 1 PV it came to greatest
productivity.
 With expanded pore volume thickness lessens by 5%, that diminishes the distinction in
consistency between water pursue as well as polymer slug.
Pursuant injection of polymer slugs with high viscosity so as to upgrade the conformation and
redistribution of the movement within the storage through reducing the movement in the zones of
higher permeability (Wang et al., 2012). In Thomas’ opinion, a large portion of the polymer
surges prompt centralizations of dynamic polymer somewhere in range of 1000 and 2000
sections for every million (ppm), that does not rely upon the supply highlights alongside oil
thickness. These numbers don't contain any logical foundation.
Generally, when the oil is quite high or the heterogeneities of the repository are essential, in any
event for the pilot arrange a higher consistency should be considered with the end goal to
examine the breaking points of worthy supply weight; in any case, the last polymer arrangement
8

thickness that will be infused is regularly shown by the oil costs and the financial matters amid
the season of endorsement of the undertaking (Thomas, 2016). Polymer injections result in about
10% increment of the oil originally in place (OOIP). The average oil recovery increment from
polymer injections is about 0.1 of the OOIP. Several fields in the world that have applied the
method have recorded increment in oil extraction in different bounds with the Courtenay field in
France with a range of between 5% and 30%, Daqing at 12% and Marmul at 10%.
2.4.2 Timing
However, the execution of the enhanced oil recovery techniques from the primary
recovery to the beginning of the drilling is faced by various setbacks. These challenges include
unavailability of information on the geometry of the green field, distribution of liquid, pressure
alterations due to the injection of a viscous fluid, ideal well placement and zone connectivity. In
addition to that, the jargon of how to quantify the enhanced oil recovery process and increasing
oil without the researched data for analysis also contributes to the reason why. The of secondary
enhanced oil recovery method is better economically than immediate implementation of tertiary
enhanced techniques of oil recovery due to the high water treatment and disposal costs. This is
because the polymer flooding causes oil production profile to move forward delaying the water
breakthrough. Nonetheless, implementation of the technology in watered out reservoirs often
with regard to heavy oil wells is still realizable (Seright, 2010).
2.4.3 Screening Criteria for Polymer Application
For a long period of time, sandstones have been preferred over carbonates. A look into
projects done in the US between 1971 and 1990 reveals that they were done on sandstones for
the polymer injection. Around 57 out of 320 pilot projects were carried out on carbonate
9

reservoirs. The preference could be expounded through the fact that negatively charged ionic
polymers present various merits:
 They contain a high gluing power.
 They have a huge molecular weight.
 They are cost effective to produce in comparison to synthetic positively charges
ionic polymers which are costly to create, high tear ability, are responsive and
display low molecular weight on average.
The injection of anionic macromolecules to sandstone and reservoirs with clay coated
edges, which are negatively charged, is preferred to so as to inhibit reaction of ions. Reports
published in the early 1960`s, 1970`s and 1980`s show that polymers for enhanced oil recovery
were limited to a shallow gradation of oil field states. A review on polymer field applications
indicates that 90 degrees Celsius was the maximum reservoir temperature, the unpurified oil
stickiness must be under 200cP while the water injected had not to be surpass a given quantity of
diatomic ions (300-500ppm).
Table 1: Polymer flooding screening criteria according to Chang. Available from
https://www.intechopen.com/books/chemical-enhanced-oil-recovery-ceor-a-practical-overview/
polymer-flooding
10

In 1991, the ranges of the temperature, viscosity and reservoir permeability were
modified by Sorbie to: temperature being equal to 95 degrees Celsius, viscosity less than 70 cP
and permeability above 20mD
.
Table 2. Polymer flooding screening criteria according to Sorbie. Available from:
https://www.intechopen.com/books/chemical-enhanced-oil-recovery-ceor-a-practical-overview/
polymer-flooding
Seright observes that several accounts for this screening basis were proposed at that time
in view of the technology present; whereby 150cP was viewed as the high viscosity oil polymers
could recover and oil viscosities above 150cP achieved a favourable mobility but they decreased
injectivity (Seright, 2010). Research has led to numerous improvements that have broadened the
range of polymer applicability in enhanced oil recovery. Availability of better information on the
flow of polymers through the rocks and a better understanding of the dynamics and geology of
the reservoirs have allowed chemists to manufacture polymers have enhanced stability due to
high temperatures, high concentrations and high tolerance to extreme salinity. Also, the polymers
11

are shear resistant and hence protective additives have also been added to these polymers to
increase their chemical stability.
New technology has been applied through the invention of new equipment that have
been tailored in such a way to increase the efficiency of injection of polymer solutions so as to
decrease the chances of degradation before going into the reservoir. The stability of ter polymers
based on N-vinyl pyrrolidone is 12 months at 120 degrees Celsius in 180g/l TDS brine
(Vermolen et al., 2011). Gaillard evaluated how effective preservative additives were on salinity
as well as polymers that are proof to temperature (Gaillard et al., 2010). The use of polymers in a
500cP field of oil is elaborated by Seright (Seright et al., 2010). Kulawardana showed the
effective N-vinyl pyrrolidone ter polymers propagation in 50mD cores at 100 degree Celsius.
(Kulawardana et al., 2012)
Table 3. Polymer flooding application screening criteria. Available from:
https://www.intechopen.com/books/chemical-enhanced-oil-recovery-ceor-a-practical-overview/
polymer-flooding
2.4.4 Parameters to Consider before the Implementation of Polymer Flooding.
Since different reservoirs and oil fields have different conditions, there are important parameters
to take note of prior to the application of polymer flooding. They include:
 Ideal water injectivity to guarantee suitable polymer injectivity.
12

 Clays should be present in small amounts since a high percentage of clays may
affect polymer propagation negatively due to clay`s retention and adsorption.
 To circumvent away from dilution and chemical issues, injection should be done in
presence of aquifers.
13

CHAPTER THREE
RESEARCH METHODOLOGY
Introduction
Research methodology is featured as a the voluntary approach that would give the
researcher an opportunity and surety to put in place the required data or come to terms with the
evaluation that is linked to the subject through the use of an avalanche of strategies of research.
This research project aims at studying the application of polymer flooding for increased recovery
of oil. The main objectives of the task were put in place to aid in the achievement of the main
study aims. Owing to such a scenario, it is of importance to conduct an overview of the very
topic of study.
A comprehension of the key characteristics of the research topic is very fundamental in
this study and on one aspect; qualitative research method approval would be used alongside
review of the various works of literature as well as quantative approaches were adopted in the
study. This approach of research methodology is ideal in performing this research since the
literature reviews provide information which are of the required depth regarding the application
of polymer flooding for increased recovery of oil. The research methodology gives a summary of
the preceding strategies which have been performed in the field as well as offering brief
description of the application of polymer flooding for increased recovery of oil. In a nutshell, the
gap in the knowledge was established through the aid of the works of literature by preceding
experts.
Research Approach
For evaluation the application of polymer flooding for increased recovery of oil, the
mixed methodology approach has been selected to be ideal in carrying out this study. By mixed
14

methodology it means the incorporation of both the qualitative as well as the quantative methods
of research in a bid to attain the objectives as well as main aims of a research project. Going by
the previous mentioned objectives and aims of the study, the research plan would be made in
such a way that is it tilted and geared towards the attainment of an in-depth and elaborate
analysis of the application of polymer flooding for increased recovery of oil.
For this reason, there would thus be need to explore the different modalities of oil
recovery, elaborating at length the various techniques that have been used before, the types of
polymers as well as hitting at the point where the technology under study finds its way into the
research. A fundamental part of this research methodology is to ascertain that as numerous
findings as possible are produced to assist in the demonstration of the different possible results
depending in the different situations which would in effect provide a solid basis for which
justifications or conclusions regarding the research may be carried out.
Going by the nature of the research at hand, the aims and objective will be met
sufficiently and successfully through the use of two kept research methodology approaches. The
nature of this research is such it tends to be more tilted towards being exploratory which means
by the completion of the study, it is to the expectations part of the aims that the research would
be endowed with in-depth and extensive as well consistent comprehension of the application of
polymer flooding for increased recovery of oil.
For the qualitative aspect of the research, an elaboration on the different parts of the
concept of improved oil recovery as well as the concept of polymer flooding would be dominant.
It is thus through qualitative research that elaborations would be made on how polymer flooding
is applicable in improving the recovery of oil. On the other hand is quantative approach which is
mainly about quantative data that are very necessary in the conducting of comparison in the
15

different study scenarios that are deemed useful to this research. Through the various quantative
comparisons, basis of justification are established that are then used in coming up with
substantial conclusions that even offer opportunities for future studies should there need be.
The qualitative aspect of the research would be affected using the four phases which
include conceptual, empirical, data analysis and finally interoperation phases in that order. The
conceptual phase is the first phase of qualitative research and encompasses the deployment of the
various skulls including deductive reasoning as well as creativity alongside firm grounding to
establish the research basis. This phase encompasses getting a background of the study and the
research aimed via conceptualization, theorization alongside a read and review of the proposals
made by preceding experts. Coming in the second position in the design and planning phase. For
the purposes of this study, this stage would adopt the use of interviews aimed at addressing the
research questions from the point of view of other stakeholders.
The empirical phase comes immediately after the design and planning phase, in the third
slot. This phase goes hand in hand or entails the collection of data and preparing them in
readiness for analysis that would be carried out in the subsequent phase. Using the provided and
selected data analysis methods, the required data would which is on the application of polymer
flooding for increased recovery of oil would be collected and safely kept for use in the data
analysis stage.
The safety of the gathered data may be guaranteed by storing the data in the forms of files
in computers or in coded forms that would ensure that the data is protected from possible loss,
manipulation or even destruction. The last phase of the qualitative aspect of this research
involves analysis and creating sense out of the gathered data. The data analyses techniques and
approaches are greatly influenced and determined by the nature of the data that would be
16

collected in the preceding phase. The use of computers in this stage may aid in improving the
process of analyses of the data especially in cases where the analysis involves statistical data.
Data collection
Data extracted from secondary sources will be accumulated from the scholastic diaries,
sites, and also sources from a special industry. Different criteria will be established to guarantee
that the most exact and pertinent optional information is gathered for the motivations behind
investigation. The main foundation is picking on those articles and diary that are about the
exploration theme of the investigation which is generation frameworks. Arranging arranged by
most pertinence makes it simple to gather and gathering those that talk about a similar theme
together. This pertinence is too comprehensive of those that talk about the subtopics of the
principle point. Dialogs on the subtopics tend to offer an inside and out examination of the
equivalent and henceforth helping in increasing better understanding.
Yet another criterion would be that secondary wellsprings of information utilized for
collection of data should peer-checked on articles and diaries as it were. By companion assessed
it implies the records are composed by specialists or researchers and afterward inspected or
cross-checked by various specialists in a similar field to guarantee that there are no irregularities
or blunders with their substance before they are distributed. This guarantees the data contained in
those reports is most exact and are those that are accepted to be contained the most up and
coming data. The following foundation would be as far as the age of the article or diary picked.
The auxiliary information sources will just settle on those associate audited diaries and articles
that were distributed not later than five years i.e. from 2013 onwards. Much the same as some
other regions or things, the field of scholastics encounters huge and fast changes inferable from
the overall changes that happen in human life.
17

CHAPTER FOUR
ALTERNATIVE TECHNOLOGIES
4.1 Surfactant-Polymer (SP) and Alkali-surfactant polymer (ASP)
Massive quantities of oil in efficiently-swept areas of water flooded oil reservoirs are
bypassed by capillary forces. Surfactants can minimize the surface tension between the water and
oil consequently releasing the trapped oil. Higher surfactants dosages need to be incorporated so
as to keep their adsorption balance on the rock surface (Lake, 1989). Adding of a base to the
resultant solution offsets the effect the alkali would adsorb into the big stones hence reducing
surfactant adsorption. The alkali will also increase the acidity and create in-situ soaps. Costly
water treatment equipment merged with the use of surfactants is needed in the process in order to
hinder the breaking of the produced emulsion. In Leonhardt’s opinion, polymer and alkali
surfactants need a mindful conceptualization that ought to be continuously maintained.
(Leonhardt et al., 2011)
4.2 Gels and Derivatives
Customary gels are utilized for conformance control where they obstruct the stream
capacity of roads with high porousness, without wrecking the hydrocarbon which is less
penetrable to high yielding zones. Consequently, it is imperative to limit the passage of gelants to
less porous zones as they are able to close off any additionally regulated liquids from dislodging
and entering oil from these beneficial zones. On another hand, polymer surges are made in such
an approach to specifically dislodge oil from zones of low penetrability. Viscous polymers
should penetrate to the maximum towards these low permeability zones with a view to displacing
oil from these regions of poor swept.
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Figure 5: Polymer flood & gel system comparison. Available from:
https://www.intechopen.com/books/chemical-enhanced-oil-recovery-ceor-a-practical-overview/
polymer-flooding
Colloidal scattering of gels-low polymer focus using a decidedly charged metallic ionic
cross linker are perceived more powerful as well as moderate as contrast with standard polymer
surges. Matter of reality, from the field execution of given innovation significant great results
have been accomplished. Nonetheless, extra oil recovery has been attributed to some underlying
factors:
 Enhancement in the water consistency from 1 Cp to 2 Cp that results in the versatility
proportion of water alongside oil to part by 2. This is realized via the expansion of
polymer inside the gel definition of colloidal scattering, even the expansion of the
polymer with low fixations.
 Polymer mechanical maintenance, adsorption as well as the gel development in every
aspect of the supply, with an alternative impact on the oil recuperation causes a decline in
the relative water permeability. More studies involving core flooding with main plugs of
extended reservoir may need to be conducted to ascertain the whole assemblage produces
via the main plug before to implementing it in real practice.
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4.3 Types of polymers
Polymers are merely chemical substances which are composed of monomers held
together by covalent bonds. Polymers are branched into two: synthetic and biopolymers. Both
types of polymers are considered when increasing water viscosity in a bid to boost the sweep
efficiency of the oil reservoir. Besides this, synthetic polymers are most preferred due to their
easy availability and affordable cost as compared to biopolymers.
4.3.1 Biopolymers.
The main biopolymers considered by the oil industry are xanthan gum and schizopyllan.
Figure 6. Molecular structure of Xanthan gum. Available from:
https://www.intechopen.com/books/chemical-enhanced-oil-recovery-ceor-a-practical-overview/
polymer-flooding
4.3.1.1 Xanthan gum
Xanthan gum is characterized as the result of aging that is delivered from a Xanthamonas
campestris mutant. It is a polysaccharide which is manufactured using various monosaccharide
units, for example, D-mannose, D-glucose and D-glucaronic corrosive. This biopolymer contains
spine like cellulose that is made out of rehashing units of β-D-(1-4) glucose with the side chains
of mannose and glucaronic corrosive. The acetyl and pyruvate ketone bunches have adjusted the
mannose halfway. As compared to polysaccharides, Xanthan gum has a rigid structure that
provides good deformation and soaks tolerance. Its drawbacks are that it is very costly and not
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easily available. Also biocides easily attack the xanthan gum yet biopolymers need to be
protected from biocides.
Forms of Xanthan gum
Juices: Made from 5 to 13% dynamic substance in a watery arrangement that comprise of
biocide.
Powder: dry type of dynamic substance more noteworthy than 90%.
4.3.1.2 Schizopyllan
It is characterized as a homo-glucan with 2 to 3 million Dalton normal atomic weight. It is
delivered by a parasite via an aging procedure from a carbon source. It is composed of direct
structure with no charged utilitarian gatherings that yields intemperate stickiness and in addition
salt continuance. The temperature as well as mechanical sound qualities happens because of the
unbending nature of structure (Leonhardt et al., 2011).
Figure 7. Chemical Structure of glucan. Available from: https://www.intechopen.com/books/chemical-
enhanced-oil-recovery-ceor-a-practical-overview/polymer-flooding
The most important step in the advancement of the biopolymer was the bioengineering
procedure needed to isolate from the biopolymer the fungus and therefore be able to make it
viable at large scales.
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4.3.2 Synthetic Polymers.
4.3.2.1 Partially Hydrolyzed Polyacrylamide.
Partially hydrolyzed polyacrylamides are the most common synthetic polymers utilized in
polymer flooding. They are synthetic dynamic linear acrylamide monomers chains. They are
made with a 30% hydrolysis extent, but it can be either increased or decreased. This polymer can
be delivered either as a powder with greater than 90% dynamic substance or like an oil emulsion
with water in with 30% dynamic substance that has to be well reciprocated to relinquish polymer.
Figure 8. System of inverse emulsion. Available from: https://www.intechopen.com/books/chemical-
enhanced-oil-recovery-ceor-a-practical-overview/polymer-flooding
22

CHAPTER FIVE
POLYMER MANUFACTURE AND CHARACTERISTICS
5.1 Chemical Paths Used to Manufacture the Polymers.
Different chemical paths can be used to manufacture these polymers. Some of the paths
are:
1. Sodium acrylate alongside acrylamide copolymerization (and/or sodium acrylamide-
tertiary-butyl sulfonate)
Figure 9. Overview of copolymerization process. Available from:
https://www.intechopen.com/books/chemical-enhanced-oil-recovery-ceor-a-practical-overview/
polymer-flooding
2. Polyacrylamide of cohydrolysis or post hydrolysis.
Figure 10. Overview of the post hydrolysis process. Available from:
https://www.intechopen.com/books/chemical-enhanced-oil-recovery-ceor-a-practical-overview/
polymer-flooding
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3. Acrylamide copolymerization or terpolymerization of with other basic monomers
which are ionic or not ionic in nature. They may help the continuance to saltiness as
well as temperature. (Thomas et al., 2013). A precedent is that of N-vinylpyrrolidone
for improved saltiness alongside warm obstruction.
The diffusion of the anionic charges along the polymer chains differs according to the
manufacturing process because; during as well as upon hydration it produces different physical
features. Post hydrolyzed polyacrylamides are comprises of huge variation of negatively charges
connections, some of them being excessively electrified while the rest are poorly electrified.
Sodium acrylate and acrylamide copolymerization of produces a polymer that is equitably
charged along the spine. Such features are vital for attributes of polymers in sedimentary
arrangements, most fundamentally within the sight of bivalent decidedly charged particles like
calcium as well as magnesium (Leonhardt et al., 2011).
Anionic polyacrylamides can be characterized according to their molecular weight and
their polydisperity index. Their molecular weight ranges from 4 to 30 million g/mol; it is
normally gauged using necessary estimation of consistency. Polydisperity file gauges isn't
conceivable to quantify as neither low polydisperity standard record nor gel pervasion
chromatography strategies exist for this high atomic weights. In any case, an enormous scope of
atomic weights exists in one chose item. Also, the organization of copolymers is simpler to direct
than the atoms that are post hydrolyzed. The figures underneath demonstrate some structure of
regular polymers.
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Figure 11. Sodium acrylate & acrylamide copolymer example. Available from:
https://www.intechopen.com/books/chemical-enhanced-oil-recovery-ceor-a-practical-overview/
polymer-flooding
Figure 12. Example of acrylamide. ATBS copolymer. Available from:
https://www.intechopen.com/books/chemical-enhanced-oil-recovery-ceor-a-practical-overview/
polymer-flooding
5.2 Polymer Characteristics
5.2.1 Viscosity.
The limit of contrarily charged polyacrylamides in expanding consistency is related with
the level of association of the macromolecules with high atomic weight besides furthermore with
the shocks among intramolecular alongside intermolecular electrostatic polymer loops. A
reduction in thickness is analyzed when polyelectrons are broken down in saline arrangement.
This is attributed to the protecting impact of charges that prompts the decrease in electrostatic
repugnance and subsequently causes least engendering of the polymer curls in watery
arrangement (Borthakur et al., 1995). It results in lower thickness besides a lower hydrodynamic
volume (Ellwanger et al., 1980). Aside from dependence on salt, there are some different
elements that effect on thickness of the incompletely hydrolyzed polyacrylamide arrangements.
These elements incorporate the dissolvable quality, tridimensional structure, level of hydrolysis
arrangement temperature and atomic weight also (Sukpisan et al., 1998).
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Figure 13: The diagram illustrates viscosity of various polymers with regard to molarity. The mean
weight of the molecules improves from Flopaam 3130S to 3630S. Available from:
https://www.intechopen.com/books/chemical-enhanced-oil-recovery-ceor-a-practical-overview/
polymer-flooding
Relying on the chemistry and the components of the aqueous solvent, polyelectrolytes are
most likely to behave differently at iso-molecular weight and at iso-concentration conditions. An
example is if the polymer is harmonious with injection, the polymer molecule would unwind
enabling interchain relations. Be that as it may, should the polymer be contrary with the infusion,
the polymer will curl up, and that could prompt intramolecular affiliations. Intramolecular
connection might be permitted if a hydrophilic atom is joined with hydrophobic moieties in the
polymer spine exclusively relying upon the sub-atomic weight of polymer. Just recently, thermo
sensitive polymers were developed.
Figure 14. The diagram illustrates temperature against viscosity graph for numerous polymers. Available
from: https://www.intechopen.com/books/chemical-enhanced-oil-recovery-ceor-a-practical-
overview/polymer-flooding
The thermo delicate thoughts are among them hydrophilic side chains or essential chains
with squares with lower basic temperature of the arrangement (Bokias et al., 1997). These
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thermo delicate polymers demonstrate thickness ascend as a component of saltiness as well as
heat variation. Extra benefits of such thermo delicate polymers might comprise of the profoundly
redesigned injective capacity inside the structures which bear oil as the thickness would develop
altogether with the expanded temperature and saltiness.
5.2.2 Rheology
Polyacrylamide liquids act as non-Newtonian fluids therefore viscosity depends on
adopted deformation stress.
Figure 15. Types of fluids and their characteristics. Available from:
https://www.intechopen.com/books/chemical-enhanced-oil-recovery-ceor-a-practical-overview/
polymer-flooding
They exhibit a pseudo-plastic behavior: viscosity drops with the increase in shear stress
as a result of a power law model.
Figure 16. Profile of viscosity for a non-typical non-Newtonian polyacrylamide liquid in terms of fitted
shear rate with a power law equation. Available from:
https://www.intechopen.com/books/chemical-enhanced-oil-recovery-ceor-a-practical-overview/
polymer-flooding
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The consistency is dependent on molarity as well as the polymer sub-atomic weight in
fluid arrangement. What's more, the rheological quality in permeable media is not quite the same
as the rheological conduct in mass if there should be an occurrence of engineered polymers.
5.2.3 Stability Test
Delay dependability tests ought to be done to discover that no corruption will happen for
the polymers between the season of infusion and landing in the oil creation wells. Anaerobic
condition is required with the end goal to set up the polymer arrangements. In this respects it is
required to have lacking oxygen inside a glove and put in particular ampoules that are planned
with treated steel put away in broilers at specific temperatures. Concentric cylinder Brookfield
rheometers are used to regularly check for viscosity.
Figure 17. Prototype glove box set up for conducting tests in anaerobic circumstances. Available from:
https://www.intechopen.com/books/chemical-enhanced-oil-recovery-ceor-a-practical-overview/
polymer-flooding
5.2.4 Solubility
Injection soak which is composed of dissolved electrolytes are utilized so as to solubilize
the polyacrylamides. Complete dissolution occurs when there is no swollen particle that remains
in the solution. This is done by a filtration test. High molecular weight polymers create
challenges if complete dissolution does not occur. Moreover, polymers may have low
concentrations of partly soluble species due to cross-linked chains formed at the production
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stage. Thus, it is important to make sure that the undissolved polymer groupings are not formed
during polymer dissolution procedure. This is to hinder possible setbacks to the formation during
polymer addition.
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CHAPTER SIX
CORE FLOODING AND POLYMER DEGRADATION
6.1 Core flooding
The proliferation of the macromolecules through core plugs from the reservoir is checked
by the injection of the polymer into porous medium. This is to prevent permanent damage to the
formation. It is important to be thoughtful that a core plug is not a representation of what would
occur in the field particularly in extreme circumstances which are available around the infusion
well bore. In this manner, building up a face plug and the spread of confirmation of correct
polymer moreover that is likewise essential. Additionally realizing that there will be no center
flooding testing that expedites data the viewpoints at view is critical.
Polymer center flooding testing provides not any generous data identified with the
injectivity that is particular to the polymer present in the field. Well bore effects on polymer
flooding examples are like completion along with the flow rates, the availability of micro-
fractures and formation of damage existing among others that cannot be evaluated while the core
flooding testing. Polymer conduct of the shear-thickening which is seen in the lab probably won't
happen in the handy field while the accessibility of small scale breaks is viewed as which is
shaped in the wake of completing the well or amid the water flooding stages. Polymer center
flooding testing isn't in charge of giving critical data on obvious polymer maintenance esteems.
6.1.1 Objectives of Polymer Core Flooding Testing.
To differentiate a few polymers in term of proliferation alongside the adjustment of weight drop.
To differentiate the maintenances of relativity of assortment polymers alongside the remaining
obstruction factors.
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To set up the viability of oil recuperation identified with the capacity of the kind of polymer and
the infused consistency.
To astutely get information from the models of reproduction for up-scaling (elements of
obstruction and maintenance).
Essential screening should be possible through the usage of simple center fittings preceding the
utilization of the current supply center attachments to get more viable portability decrease
besides maintenance esteems. The portability decrease or opposition factor alongside the
decrease of penetrability lingering is obstruction factor are assessed. The mobility factor is the
approximate relative viscosity of the solution of the polymer available during its flow coming
through the porous medium defined by:
FR = (∆P polymer solution / ∆P brine) α (μ polymer solution / μ brine)
Where ∆P Polymer solution is the pressure drop during polymer injection and brine while μ is
the thickness of thought about liquid. The porousness is the diminishing of multiplication
because of different instruments present like the polymer assimilation onto the surface of the
stone, along mechanical maintenance of polymers in choking influences of the pore that are little
in size when contrasted with the macromolecules of the polymer and diverse other situation that
keeps up the polymer that is available in the permeable media like polymer precipitation. This is
a direct result of cooperation with cations that are divalent and present in the repository brackish
waters. The residual resistance factor (FRR) is referred as per the diagram below:
FRR = (∆P post polymer / ∆P brine) α (k brine / k post polymer)
According to (Sorbie, 1991), the retention of the polymer will be better suited to the
wording as it is involved in the adsorption along with the hydrodynamic and the mechanical
entrapment.
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Figure 18. Mechanisms of polymer retention. Available from:
https://www.intechopen.com/books/chemical-enhanced-oil-recovery-ceor-a-practical-overview/
polymer-flooding
Retention is a very important aspect and can be determined by looking at their static or
dynamic conditions. Polymer retention is dependent on the rock lithology: the availability of soil,
type of the clay as well as the clay content, besides on the polymer traits like weight of the
molecule, science and hydrolysis amount. Maintenance of polymer in the permeable material
may be controlled by controlling the polymer science, the weight as well as by affixing operators
of penances which is preceding the supply condition before infusion of polymer (Shamsijazeyi et
al., 2013). On expansion of ATBS that is known to upgrade the spread for the polymer science
while bring down weight of atoms which implies lessened maintenance of hydrodynamics for the
sub-atomic weight.
6.2 Polymer Degradation.
Oil field applications highly depend on the stability and chemical reliability of polymers.
During enhanced oil recovery flooding operations polymers can go through chemical,
mechanical and thermal degradation. There lacks sufficient data on the degradation degree take
in by the polymer during the functioning of flooding. For field operations it is also necessary to
find out where degradation of polymer happens: at the offices of the surface, inside the store or
down gap of the infusion well. It is likewise essential to lessen any critical corruption to maintain
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a noteworthy consistency of the infused polymer arrangement while the time of the upgraded oil
recuperation flooding to enhance the recuperation of the additional oil.
6.2.1 Chemical Degradation.
Concoction corruption is associated with the free radicals arrangement that may frame a
response with the foundation of polymer spine. These outcomes in a decrease of atomic weight
and consistency misfortune (Wellington, 1983). As per Fenton, there is association of the redox
responses amid the development of free radicals. Nearness of oxygen and different contaminants
like iron add to the arrangement of such radicals. There are balancing out mixes that are added to
polymers of business review to defer wild happenings of substance debasement (Fenton, 1984).
Figure 19. Polymer degradation in oxygen availability alongside iron 2 in 7.086g/L TDS brine. Available
from: https://www.intechopen.com/books/chemical-enhanced-oil-recovery-ceor-a-practical-
overview/polymer-flooding
The figure shows how iron and oxygen concentration impacts the percentage of viscosity
loss of polymer solution. The viscosity loss may rise to the tune of 50% besides the extra of just
1ppm of iron besides 300 ppb of oxygen.
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6.2.1.1 Oxygen
For enhanced polyacrylamide stability, maintaining oxygen concentration below 5ppbA
guarantees good stability up to 120 degree Celsius for more than 200 days (Seright et al., 2010).
The additions of oxygen scavengers such as sodium sulfite as well as dithionite to the brine are
of advantage for the maintenance of the oxygen concentration which is free alongside at a low
level in comparison to the brine. Re-exposure of the brine to the oxygen will act to degrade the
chains of polymer regardless of the oxygen scavenger presence. Therefore, the oxygen content of
the brine in presence of the oxygen scavenger should be kept under control.
6.2.1.2 Iron.
Several complexing agents like ethylene diamine tetra acetic acid are added to limit of
polymer degradation that is because of iron traces which is injected to brine. However, using
chelating agents will make the iron complex lead to increased polymer degradation
(Kherandmand et al., 1990). Another option may be be to precipitation the partly attained iron in
the brine which is injected through increasing the pH of the solution with the sodium carbonate
(Levitt & Pope, 2008).
6.2.2 Mechanical Degradation
Mechanical degradation occurs when higher shear rate besides high flow rate as well as
drop in one pressure which are exposed to the backbone of the polymer. Chokes, values and
certain types of pumps and completion are significant points which must be evaluated along with
the facilities of injection (Maerker, 1975). Choosing on the appropriate polymer is important: the
molecular weight in average is directly proportional to shear of the sensitivity. High weight of
molecule polymer degradation may probably enhance the injectivity using a small reduction in
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stickiness. A setback to this technique can be the loss of visco-elasticity, which is primarily
shown by the molecular weight fraction of the polymer which is highest (Wang et al., 2000).
Figure 20. Degradation of shear besides viscosity loss percentage for polymers with similar chemistry but
various molecular weights. Available from: https://www.intechopen.com/books/chemical-
enhanced-oil-recovery-ceor-a-practical-overview/polymer-flooding
The figure depicts the effect of degradation of shear on polymers having various
molecular weights.
6.2.3 Thermal Degradation.
Warm debasement changes with the supply conditions and polymer compose. If there should be
an occurrence of a run of the mill HPAM polymer, an ascent of temperature will result in an
expansion in the hydrolysis of acrylamide moieties that therefore will produce a higher thickness
of charge of functionalities of anions along the foundation of the polymer.
Figure 21. Acrylamide moieties hydrolysis besides the polymer backbone. Available from:
https://www.intechopen.com/books/chemical-enhanced-oil-recovery-ceor-a-practical-overview/
polymer-flooding
A viscosity drop is observed when the brine has realizable amounts of divalent positively
charged ions for example calcium besides magnesium. This is attributed to links of ions that may
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finally results in the precipitation of the polymer (Moradi-Araghi & Doe, 1987). Tolerance to
calcium is improved by adding sulfonate monomer (ATBS) to the polymer backbone at high
temperatures. This however increases the cost of the polymer.
Figure 22. Salt tolerance of different polymers. Available from:
https://www.intechopen.com/books/chemical-enhanced-oil-recovery-ceor-a-practical-overview/
polymer-flooding
It is therefore vivid that the polymer`s chemical structure’s fine tuning like the molecular
weight and composition is important in order to elevate the solidness of polymer for execution at
the states of the particular repository. In the choice of the perfect store with the end goal of
polymer flooding, the accompanying supply qualities must be considered: temperature of
repository, arrangement of brackish water regarding saltiness alongside divalent cations, press,
disintegrated oxygen alongside hydrogen sulfide and the porousness. There may complete of
polymer solidness tests which can be brought out through a protracted timeframe to ensure the
loss of thickness isn't seen amid the way toward maturing while the contaminants are available
(Thomas, Gaillard & Favero, 2013). It is therefore necessary to conduct these experiments under
regulated amounts of oxygen conditions to estimate the level of degradation.
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CHAPTER SEVEN
DESIGN AND IMPLEMENTATION
7.1 Polymer Flooding: Design and Implementation
The best technology is required at an affordable cost to enhance oil recovery and hence
reservoir screening is often done. Various techniques can be used during the screening process.
However, some of the techniques may be difficult to employ. The two basic polymer flooding
rules are:
 Making a choice on supplies having poor water flooding proficiency that clear because of
nearness of raised consistency of oil as well as heterogeneity which is substantial scale.
 The in general audit of the state of store which is resolved whether the polymer is
executed by flooding or will settle the lessened effectiveness issues of settling.
In order to find out if polymer flooding would be a good option, specific parameters are
considered:
 Lithology – sandstone
 Temperature below 140 degrees Celsius
 Plorifility above 10mD
 Oil viscosities below 10000 cP
 Current oil saturation
Salinity of the injection water which should be less than 200g/l total salts that are dissolved
For the case of the salinity, a parameter known as R is recognized. The ions of cationic
divalent weight ratio divided by the ions cations number is in the provided equation:
R+ =
∑❑
❑
❑ Divalent Cations
∑❑
❑
❑Cations
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Of the elements the hugest is the immersion of oil as well as the oil buildup which is
comparing. Oil developments are by and large heterogeneous normally and consequently the in
site thickness of oil is an estimation which is auxiliary be it in situations where consistency of the
oil is decreased and the proportion of the portability of the uprooting procedure that is seen to be
ideal, and the arrangement of oil are for the most part heterogeneous in nature. In this way, it is
profoundly anticipated that even in such situations where there is portability proportion and the
effectiveness is sweeped which can be bettered by the utilization of a polymer flooding. To
achieve the objective consistency, the most fitting polymer science as well as the convergence of
polymer required is vital to be taken into account. Increase in the temperature and salinity leads
to the increase of polymer molarity required to obtain enough thickness to enhance the oil
retraction hence, the more the polymer flooding cost.
More studies of reservoir should be done prior to the implementation of a pilot scale test
and after the first selection. The concerned engineers should survey the reservoir rock structure
and composition, the target oil distribution, faults present and location, aquifers, shales and the
spread of clays. This assists in comprehension as well as cleaning the ongoing information
identified with the supply besides the conduct which is infused and the liquids delivered with the
end goal to repress scattering synthetic substances and polymer which misfortunes while the
polymer flooding.
7.2 Tracer Test
Tracer flooding test aids in bettering the depiction of store for improved decision utilizing
a scope of strategies. It gives upgrade data identified with correspondence between one oil well
as well as another and time of travel, substantial scale layering information, estimation of areal
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compass and depiction of in-layer. After the examination deliberately of the creation in a leap
forward of the brackish water that is delivered may provide useful data since there is a difference
in the composition of the produced brine, making it unnecessary to perform explicit tracer flood.
Nonetheless, it may be made complex by ion exchanges within the reservoir, specifically for
calcium ions. The polymer itself is however a good tracer as it detects production wells during
initial process using the kaolinite flocculation method
7.3 Importance of Water Quality.
 A superior water surge with great injectivity alongside clean water will prompt a well
polymer surge which is well performing. The suggested structure of clean water by oil
organizations is:
 Oil content less than 100 ppm to repository stopping limiting.
 Solid content under 20 ppm
 The sizes of strong molecule are under 5 micrometers to repository stopping limiting.
The presence of consistent salinity over the life of a project to minimize viscosity variations.
Oxygen content less than 20 ppb to polymer degradation to avoidance of Iron II or H2S present.
Except for the oxygen content, the composition of the water have not a major effect on
traits of polymer or presence of stability even though there is no influence the wholesome
performance of the facilities of the surface and the wells of the injection. The resistance of the
polymer solution is made in such a way to cause a decline in the overall water-oil mobility ratio
in the reservoir of the fluids. Aside from than lessening polymer debasement, it is very critical to
infuse the polymer ceaselessly at the thickness of target. This can be achieved by inline thickness
checking of infused polymer or with inspecting of occasional polymer. Since the nature of water
can change the objective polymer fixation, it isn't considered.
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7.4 Pilot Injection Monitoring
The purposes of a pilot polymer injection involves to:
 Monitor the effectiveness of polymer administration procedure.
Obtain data regarding how the reservoir will respond to the injection of polymers to it. This isn't
data is valuable to enhance the model of supply and to gauge the incremental recuperation of oil
that expected to ascertain the polymer flooding of the financial matters in a view that is
augmentation of full field.
7.5 Considerations Made During Pilot Polymer Flooding Implementation and Monitoring.
 In request to begin the polymer of stream into the repository, polymer infusion that ought
to be shot up over various days.
 Injection rate, well head pressure, aggregate infusion and base opening weight ought to
be kept in records all through the pilot.
 The thickness of polymer must be gauged by proper collection and choice of selection of
tests or usage of inline viscometers.
 There is suitable control of the separating working weight may be vital to enhance
injectivity and decrease polymer corruption by and large.
 The polymer flood sweep efficiency becomes better with enhancement in viscosity of the
polymer solution being injected.
 Step-rate tests ought to be conducted with the end goal to gather data on the ideal
execution infusion rates, alongside polymer thickness as well as weight.
 Good water quality is important to ensure a good polymer flooding process.
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An inline viscometer and periodic sampling at the well head can be used to achieve
continuous viscosity monitoring. This will ensure the resistance of flow of the injected solution
is the targeted one. In order to ensure that the viscosity measured is in tandem with the product
arrangement and debased polymer test, liquid examining procedure ought to be completed
painstakingly. Inspecting mistakenly may results in shearing or otherwise oxygen section into
example of the polymer that will start responses among oxygen and potential retarders like iron,
framing free radicals which synthetically which is debasing the polymers with a moment
decrease in the consistency of polymer.
7.6 Injectivity
Many of the polymer injection projects like Daqing, Suriname and Kazakhstan oil fields
have succeeded in injecting high polymer viscosities. However, minor cases of bad injectivity
have been reported during the polymer injection. These cases are connected to a disruption in
flooding outline which incorporates wrong frameworks of polymer disintegration as well as
projection polymer against concoction, warm besides mechanical debasement, issues with nature
of water, well fulfillment, polymer arrangement infusion that has low viscosities and poor
infusion which are out of objective zone. According to (Al-Saadi et al., 2012), various Oman
engineers have suggested reasons to justify the reason for noticed injectivity was way more
improved as compared with the predicted injectivity.
 Degradation of polymer which is during injection: However, this hypothesis is
dismissed at the point when the thickness of the polymer and fixations are checked in
the liquids of generation.
 Polymer rheology: The shear diminishing long with drag minimization impacts are
regularly that is not taken into consideration owing to infusion.
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 Reservoir heterogeneities which are not characterized.
 Dilution instrument in the aquifers that are encompassing.
 Linear against spiral stream: Through comprehension of the administrations of
stream, it is a requirement to think about the fulfillment of various well composes
(rock packs, cased and punctured, small scale breaks, vertical versus level wells as
well as the skin factors).
The introduction of a high viscosity polymer brings about enhanced stability in
displacement which later causes enlarged area of sweep and therefore, reduced pressure drop
for every linear meter. This means that should the surface of swept and hence, less pressure
drop per linear meter. This means that should the swept region is increased for the equal
amount of fluid, the fluid pressure decreases over some decrease in distance.
Almost all wells are injected that are under fracturing circumstances.
It is important to understand the kinds of fractures that have been adopted with regards to
fracture geometry as well as extension. Some of the suggestions are:
 Proper infiltrating and finish that will change the weight repartition around the well bore
and make perils that despite customary supply heterogeneities will set extraordinary
conditions for scaled down scale break creation as well as enlargement.
 There is far to go from the non-normal section of oil alongside gas age specifically from
the using water fueled breaking to make hydrocarbons from stores of low permeability,
particularly, as for break generation, elongation as well as presentation. Geomechanics
may be a significant instrument to comprehend advancement of split concerning
customary oil stores.
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 Prolonged store water flooding will empower the close well bore development harm. All
the more so while the infused water is absent at the temperature of store.
 Making use of normal storehouse watching strategies such as (advance rate tests,
impediment tests as well as Hall plots), along with regulating mixture extent as well as
strain to open up or close little scale splits can pass on generous change to the polymer
flooding field action.
7.7 Numerical Modelling and Simulation
Three dimensional modelling is essential in predicting the productivity of a polymer
flooding when the client has appropriate information of the polymer qualities and polymer
stream properties. Demonstrating the close well bore region to copy the outcomes saw amid the
field pilot infusion is the most pivotal issue. Polymer administrations, for example, shear
diminishing or features of shear thickening ought to be utilized warily along with a reasonable
comprehension of well fulfillment, arrangement harms besides supply cracks. Maintenance and
leftover factorization can be acquired from research facility tests. Low shear thickness data
gotten from regular rheometers for reproduction reasons can likewise be utilized. Polymer
corruption in the store is typically constrained since the science of the polymer is picked so that
there is soundness of the polymer amid polymer presentation and conveyance all through the
supply.
7.8 Quality Control
These strategies are available to keep the polymer to be infused at check. The
fundamental attributes of polymer quality control are:
 Dynamic polymer content: Active material of the strong powder.
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 Yield consistency which is characterized as the polymer sum required in the infusion
saline solution to achieve the objective stream hindrance level.
 UL consistency: Polymer arrangement viscosity at 0.1% dynamic in 1 mole NaCl.
 Polymer arrangement filterability: It is of essence to decide polymer disintegration
challenges, for example, the development of undissolved groups of polymer.
Figure 23. Prototype set-up for conducting filter ratio tests using vessel besides graduated cylinders
linked to a stopwatch. Available from: https://www.intechopen.com/books/chemical-enhanced-oil-
recovery-ceor-a-practical-overview/polymer-flooding
7.9 Back Produced Polymer
Data regarding the sum and nature of back-made polymer and also their impact on the ebb and
flow water treatment workplaces, is particularly conveyed by a pilot imbuement. For widened
field broadens, the made water and grungy isolation orchestrate and the conveyed water
treatment arrange must be considered as imperative parts of layout execution of polymer
flooding. The safe water may either be used again or gotten rid of. The basic purposes of
treatment of back conveyed polymers are:
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 Wasteful oil-water parcel may most likely happen when anionic polymers collaborate
with oil emulsion recepticle structures. Various associations pick the most efficient and
flawless oil-water breaker via a couple of tests among them bottle testing.
 Adversely charged polyacrylamide particles are for the most part used in water treatment
methods, for instance, flocculating administrators. Should the total suspended solids
(TSS) be really great in the fluid present, a couple of agglomerates can show up and
quickens can store on the process equipment surface (warming units). These leftovers
must be removed discontinuously.
 Back conveyed treatment of water equip is regularly estimated to work using water
thicknesses underneath 4cP. A decline in the capability of treating contraptions in
disengaging hydrocarbons as well as wetted suspended substances is seen with an
extension in water consistency. Mechanical, engineered and filtration procedures can be
used to decrease the thickness of the made discharge with a particular ultimate objective
to keep up the viability of the water treatment process (Al-Kabani et al., 2014).
 Mechanical defilement is a beneficial system for lessening the nuclear weight of the
polymer and consequently it reduces the thickness of the course of action. A shearing
pump is used to achieve the desired corruption and along these lines decrease the
thickness of the polymer course of action made. An abundance of shear can at any rate
settle oil in water emulsions.
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Figure 24. Degradation of solutions of polymer mechanically at various concentrations. Available from:
https://www.intechopen.com/books/chemical-enhanced-oil-recovery-ceor-a-practical-overview/
polymer-flooding
Polyacrylamides encounter mixture corruption inside seeing oxidizers which make free
radicals which react with the polymer spine chain realizing a decrease of nuclear weight and
thickness of the polymer plan. Sodium hypochlorite is a favored oxidizer. Regardless, should the
treated water ought to be used again to hydrate polymer force advance imbuement, equalization
of any staying wealth of the oxidizer must be done by use of a reducing pro with the end goal to
ruin any extra of the oxidizer from defiling the current group of separated polymer.
The procedure of precipitation of polymer may be carried out with salts of trivalent
metal like aluminum sulfate. This system at any rate includes distinctive damages, for instance,
Acidification of the water by reagents which must be corrected to balance disintegration of the
rigging. Regardless, recovery of any adsorbed oil on energizes using this technique is
exceptionally troublesome.
7.10 Models that can be used in Polymer Flooding Simulation
STARS (CMG) Software
This model involves keeping the concentration of surfactant .01 wt. % and the surfactant
slug injected upon the water cut hitting 95% during the process of water flooding. Modelling of
the sand pack cores is done using 10 blocks for every surfactant flooding hence the preparation
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of a Cartesian grid in the system of surfactant flooding. The first and the tenth blocks are made to
have the injection and production wells respectively and a porosity map being predicted in the
case of surfactant flooding.
The components are would then be added in the components section using their
respective features. The water flooding simulation is first conducted until the water cut hits 95%,
a process that takes about 15 minutes to proceed to completion. 60 ml of surfactant slug is then
introduced at this stage in the add ack. Upon the completion of the process of surfactant flooding,
chase water is added in the 20th minute and the simulation run for a period of about 35 minutes.
Meanwhile the rate of constraint of injection is maintained at 10 ml/min.
Mathematical Model
In this model, surfactant polymer flooding is modeled to turn out as an immiscible,
multicomponent and incompressible two phase flow via the porous media. In this approach, Ω is
let to be a finite domain that stands in place of the porous reservoir that has the boundary∂ Ω. The
non-wetting phase which is the oil and the wetting phase which is the water or the given aqueous
solution is denoted using the subscripts “o” and “a” in that order and sj is used in the denotation
of the saturation while pj denotes the pressure and vj denotes the velocity. The appropriate source
or the term of sink is denoted by qj whle uj denotes the viscosity. The absolute tensor for
permeability is denoted by K(x) among other various parameters that are deployed in the model.
MATLAB Reservoir Simulation Toolbox (MRST) Model
In this model, an assumption is made that the component of the polymer is only relocated
in the water phase as adoption occurs in the rock. It is as well assumed that the polymer does not
influence the hydrocarbon phase and are elaborated using the standard three phase equations of
black oil. The Todd-Long staff mixing model is used in the simulation of the impacts of the
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polymer explaining the adsorption, the effects of reduction in the permeability as well as the
inaccessibility of the pore spaces. Also included in the simulation are the effects of thickening or
shear thinning which rely on the rate of shear through the means of a different inner-Newton
process of iteration within the international nonlinear iteration. The adoption of the model is
pegged on the automatic differentiation frames that occurs in the MRST-AD as well as the
iterative liner solver hat has a preconditioned of a constrained pressure residual which is adopted
in the solution of the resultant linear systems in a more effective and efficient manner.
The essence of the MRST is a significantly slim core module, a must-core, which is
composed of a grid structure that is flexible and some of the routines of grid factory; the routines
are used for the purposes of observing the grids as well as representation of data on cell faces and
cells which is the main functionality for the representation of the petro physical features, source
terms, conditions of the boundaries as well as the wells. The core is also composed of the main
functionality that is used for the purposes of automatic differentiation as well as the different
utility routines of low levels. A group of add-ons modules form the second and generally the
greatest composition of the software which are used in the implementation of solvers as well as
discretization, routines for visualization, elongated grid formats as well as more sophisticated
structures of data; more enhanced automatic differentiation functionalities used in the building of
simulators, taking readings and processing of the input decks to the standards of the industry
alongside an avalanche of simulators, user interfaces for graphics besides tools for work flow.
7.11 Comparison of the effects of the various viscosity ratios on polymer flooding
As could be expected to some extent, the effects of the different viscosity ratios on
polymer flooding as applied in heavy oil refinery may illustrate significantly varied results or
nature of behaviors. A study conducted with regards to the same made comparison between the
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effects of unfavorable ratio of viscosity (960:1) on heavy oil refinery where a delay was observed
in the development of the viscos fingering at a rate of about 0.02 cm3/min since a huge initial
pressure was needed in displacing the initial oil volume in order to initiate the process of
fingering. For such as case, a stability region was not evident as was the case with the water
displacement of 153-mPa.s oil.
By the end of about 12 minutes of injection, there was experienced a strong entrance
effect in which there was formation of the dominant fingers instantly without having any
stabilized region. For the case of this heavy oil the process of displacement could be grouped
into three main regions. The initial region is the creation of predominant fingers that are in the
shape of a tree which took place immediately. Such a growth progressed for about 24 minutes
with no coalescence of the fingers being observed with relatively significant volumes of the oil
being retained bypassed. The second region is during the progress of the injection process.
At this stage, there is no more propagation experienced in the smaller finger and the
injection of the fluid resulted in the major development of the fingers; a situation that resulted in
a significant reduction in the efficiency of sweeping. The third and the final region is all over the
propagation of the main finger in which very sophisticated splitting as well as spreading conduct
is noticed where the dendritic shaper of the finger produces numerous branches which almost
span the breadth of the 2D model.
Finally, the dominant finger channel breaks through to the generation end of the model
and no more oil recovery or spreading is noticed. Rather, there is notice of a mass transfer that
occurs between the mixing zones of the fingers which is established precisely before the front of
the defined finger. This is probably typical of a displacement of heavy oil through water flooding
excluding in reality the behavior of the fingering could take place in three aspects in such a way
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that the efficiency of the sweeping may be made even worse in some of the areas of the reservoir.
Nonetheless, the test justifies the behavioral changes that occur from a medium to a displacement
of heavy oil.
A similar study was conducted using a viscosity ratio of 40:1. In this case, the inclusion
of a polymer to the displacing phase led to a relatively higher stable displacement front in
comparison with the water at the very rate of flow of 0.02 cm3/min. besides this, it was noticed
that there was significantly less occurrence of numerous finger formation all over the initial
stages of the development with only one main macro-finger found to be dominant of the
displacement process over the whole experimental session until the attainment of breakthrough.
The outline of the region invaded by the polymer could be characterized as a region
dispersed of lower concentration that form a dendritic network of fingers that are microscopic in
nature which are invasive and displacing the regions that are saturated with oil thereby
significantly enhancing the efficiency of sweeping. Numerous sideways scattering behaviors
were noticed inside the core area of the predominant finger and were noticed to be characterized
by heavily concentrated region especially at the 40th minute mark.
On making comparisons of the captions for polymer and waster displacing oil at the
instance of the breakthrough, it is observed that the water displacing led to no further spreading
and hence resulting in minimal recovery of oil upon the breakthrough at the mark of 50 minutes.
This was contrary to the case of polymer displacement test. The further sideways scattering
proceeded even beyond the breakthrough hence significantly enhancing the sweep as well as the
displacement of more oil off the model. Such a shooting effect explained for water displacement
is not available for the case of polymer displacement.
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CHAPTER 8
CONCLUSION
In conclusion, polymer flooding mechanism as a means of enhanced techniques for oil
recovery is a very useful method to employ in recovery of the oil. The technique involves a non-
complicated method of employing it in the oil fields whereby only a long polymer molecule is
mixed with water and injected into the field. The technique is also quite affordable for the oil
mining companies and hence favorable since profits can be realized by using this method. Lastly,
ample research has been done on polymer flooding and they have shown that indeed the
technique is very efficient in the recovery of oil in the oil fields.
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