Hydraulic Fracturing: Controversial Technique for Oil and Gas Extraction

This research paper provides an overview of hydraulic fracturing, a controversial technique for oil and gas extraction. It discusses the theory of hydraulic fracture, fracture propagation models, and characteristics of tight gas reservoirs. The paper also explores the potential environmental impacts of hydraulic fracturing, including water contamination, noise pollution, and public health hazards.

A RESEARCH PAPER ON HYDRAULIC FRACTURING BY:
Name of the Student
Name of the Professor
City/State
Date/Month/Year

OVERVIEW OF HYDRAULIC FRACTURE
Hydraulic fracturing is also known as hydro-fracturing or hydro-fracking. It refers to a well
modified and a stimulated technique whereby a rock is broken down using liquid under high
pressure (Bernabe, 2009, p. 78). This mechanism includes exertion of great pressure by the
pressurized fluid which can either be water , sand or in some cases a proppant suspended by a
thick agent inside a wellbore to assist in creating point which are weak during the formation of
deep rock through which free flow will be noticed in brine, natural gas, petroleum (Fink, 2013, p.
346). On the other hand, the removal of the good pressure, the hydraulic fracturing small grains
proppants, that is, the fracture is held open by either the sand or aluminum oxide holds (Gleeson,
2016, p. 452).
The hydraulic fracturing system is regarded as most of the controversial techniques in most
countries where its proponent's advocates for the economic remunerations of expansively
reachable hydrocarbons (Wu, 2018, p. 164). Some opposing powers argue that these measures
are overshadowed by prospective environmental impacts which range from the surface or
underground water contamination, noise pollution to public health-related consequential hazards
(Wu, 2018, p. 64). Another related problem of this process is the leakage of the methane gas to
the humanitarian environment and this was discovered in Pennsylvania, that is in the United
States by the Environmental Defense Fund's report. There was also an increase in the seismic
action due to hydraulic fracturing through the inactive faults that resulted due to deep- injection
disposal of the fracturing flow-backs leading to the formation of end products for both fractured
and non-fractured oil together with gas wells.
The pressure overwhelmed those rocks that fracture at large depth as a result of the weight of
rock layers lying on top and their formation cementation. This overpowering is normally

important in ‘tensile’ fractures which require the ramparts of the broken rock to go contrary to
this pressure. The occurrence of fracture takes place when operational stress is overwhelmed by
the fluid pressure inside the rock and the minimum principal stress becomes tensile thus
exceeding the tensile strength of the real materials (Chen, 2016, p. 421). The fractures formed in
this way are generally oriented in a plane perpendicular to the minimum principal stress and is
because of this reason that the fractures in the wellbores are used to determine the orientation of
stresses (Bucher, 2013, p. 98).
Most occurring mineral vein systems are as a result of repeated natural fracturing during the
periods of high pore fluid pressure. The action of this high pore fluid is normally evident in
crack-seal veins where the vein material is part of the chain of discrete fracturing events, and
extra vein material is deposited on each occasion.
The minor intrusions in the upper part of the earth’s crust such as dikes, exists in the form of
fluid-filled cracks and this fluid is referred to as magma, but in sedimentary rocks, fluid at
fracture tip will be in the form of steam.
Theory of Hydraulic Fracture
According to Walker (1949), the following arguments were made based on the assumptions such
as; the treatment pressures should be more compared to the overburden pressure for it to cause a
horizontal fracture. This means that fractures are consistently vertical. On the other hand, the
people who oppose this matter shall actually dispute that the cause of horizontal fractures
occurring horizontally takes place since the pressure is less than the average overstretch pressure,
simply because there is lack of even distribution of overburden pressure is not evenly distributed
hence shall be induced along paths of least overburden load (Spellman, 2012, p. 129). Another

prominent issue coming up when overburden pressure is not distributed evenly is used in
explaining the low treatment pressure. In some cases, unsatisfactory overburden distribution
might be important for the shallow depths (Shojaei, 2017, p. 2237).
It is also important to note that the objectivity of the opinion that horizontal fractures are in fact
produced with lower than the overburden treatment pressure will result to gamma-ray logs which
gives a high reading at a single spot in the hole after the injection of radioactive sand, thus
showing a horizontal fracture even though the resultant pressure was smaller than the
recommended average for the overburden pressure (Adwera, 2008, p. 43).
Again during formation of a crack, it is convincing to be certain that the fracturing fluid may at
times move in and open a plane fracture in regard to a normal plane which has minimal stress
along with no initial fractures. Sometimes it seems possible to check on the fracture as it is first
propagation comes from the wellbore by a locally transformed stress field (Tuman, 2011, p. 28).
Personally, I think that induction of fracture in un-wanting orientation but following a tortuous
route due to many oriented planes of weakness will have a slight selectivity in choice of path that
would otherwise orient the general path with time and this, therefore, makes fractures to be
extended only by the pressure which is much higher compared to the compressive stress which is
in the direction of fracture displacement. Water-flood is another well-illustrated example for
obtaining data during the study of pressure- parting phenomena.
Generally, it is evident that the concern measures for pressures during the production of vertical
fractures may differ with the existence of the resulting fluid pressure (Sharp, 2014, p. 56). The
sustained pressure exerted before the breakdown in a thin zone would be suitable to perform a
horizontal fracture whereas a short period of injection in a thick bed before a breakdown leads to
a vertical fracture. In summary of this theory, it is important for one to take into account that if a

horizontal fracture is realized, the hole at the bottom resulting to pressure should approximately
be equal to the calculated overburden pressure (Sanford, 2010, p. 98).
Vertical stress
The vertical stress in most cases equal to the to the weight of the overburden per square and the
vertical stress is quite variable at shallow depth. In the case of a vertical fracture is vertical, the
treatment pressure closely equal to the least horizontal stress which generally lies below the
overburden pressure (Shojaei, 2017, p. 43).
Horizontal stress
In shallow depth, the vertical stress may be the minimum stress resulting in horizontal fractures.
This takes place for highly overpressured formations and in most cases, the horizontal in-situ
stress is less as compared to the vertical stress. The horizontal stress originates from two sources;
 Tectonic forces; geologic forces corresponding to the local geologic structure.
 Reaction to the overburden such that the overburden weight compacts the formation and
the reaction to this creates horizontal stress
Fracture pressure
The fracture pressure is the pressure level above which drilling fluids are capable of inducing the
formation of rock fractures hydraulically. The consideration of these pressure is at hydraulic
fracturing which is a stimulating process that is carried out on the routine basis on oil wells. The
deformation of rock is caused by fracture pressure and also it etches the formation resulting into
fissures that are favorable for the passage of oil and gas. The measuring of this pressure can be
done in gradient or by the density of the fluid equivalent (Bucher, 2013, p. 216).

The fracture pressure is simply defined as the amount of pressure that is needed in disintegrating
the formation of rock. The measurement of pressure should be done since it will assist in
knowing whether the pressure available is enough to cause a fracture. In deep oil well, the
pressure of the fracture is increased due to the overburden pressure. Since the location of the
rock formation is at the deep end thus tough to fracture then the pressure needs to be set really
high to avoid rock resistance or problem of circulation (Bucher, 2013, p. 12).
The stress within a rock can be resolved into three principal stresses. A formation will fracture in
case the borehole pressure exceeds the least of the pressure of stresses within the structure of the
rock (Bucher, 2013, p. 76). The following tests are carried out in order to determine the pressure
at which the rock creation fractures after exposing it to the pressure at the borehole. They
include; leak-off test, limit test and creation breakdown test (Pointet, 2008, p. 54).
Fracture Propagation Models
The earliest fracture treatments were first put into the investigation by just pumping them to
notice if in case the formation of fracture can take place a fracture could be formed through
pumping of sand into a fracture (Mader, 2009, p. 123). This science was first published by
Howard and Fast whereby they assumed in their models that the fracture width was constant
everywhere thus make it easier for the engineers in finding a fracture area relying on the fluid of
the fracture which constitutes the features of the formation and the fracturing fluid. The
following are the well- known models for fracture propagation techniques:
(a) Two-dimensional fracture propagation model
A clear example of a two-dimensional model can be given by that of Howard and Fast where
they fixed one of the dimensions, usually the height of the fracture in calculating the fracture

length and breadth (Bucher, 2013, p. 678). In regard to understanding and precise sets of
information, the model is applied; supposing the design engineer is capable of estimating the
generated fracture height precisely (Fink, 2013, p. 568). If the fracture length is higher compared
to the height of the fracture the Perkins-Kern-Nordgren (PKN) geometry is usually applied. And
in case the fracture height is the one dominating the length then the Khristianovic-Geertsma-de
Klerk (KGD) geometry is needed, and when it comes to designing the hydraulic fractures than
the two mentioned models are successfully required (McBroom, 2013, p. 519). The actual results
with predictions from models calculations are compared by this model. (Fink, 2013, p. 216). The
use of exact fracture height in this type of model gives a sensible approximation of shaped
fracture length and width if other parameters like creation permeability coefficient are used
(Choquette, 2012, p. 68).
b) Three-dimensional fracture propagation model
Due to the invention of the high powered computers in the current world, most engineers have
developed the use of the pseudo-three-dimensional(P3D) models in the fracture propagation
techniques. These P3D models are considered to be the best alongside the 2D models because
they are capable of computing fracture heights, length, as well as breadth, spreading through the
information for pay zone together with entire layers of the rock beyond and underneath the holed
intermission (Bernabe, 2009, p. 129). Dimensions and geometry of the fracture are given by this
model in detailed which can result in better wells as well as designs (Bucher, 2013, p. 129). The
hydraulic fracture shape and dimensions are computed using this particular model (Chen, 2016,
p. 208). The key to any model, be it 3D or P3D model should pose a data which is detailed and
precise which pronounces the developer layer to be fracture preserved, together with the rock
found beyond or beneath the zone of interest (Howard, 2012, p. 32). In most occasions, the data

set should contain information ranging from 5 to 25 layers of rocks that could affect fracture
growth (Carroll, 2014, p. 219). During this programming, it is advisable for one to key the
information on as numerous times as possible to enhance the model to decide the fracture height
growth as a function of where the fracture is commenced in the model (Gleeson, 2016, p. 18). It
is also important for one to note that he/she can only decide the fracture shape by entering the
data into three to five layers of the rock rather than determining the fracture model.
Tight Gas Reservoir
The natural gas known as tight gas is acquired from reservoir rocks having low permeability.
Tight gas is an environmental source of natural gas.
Characteristics of reservoirs
 Are pore in structure
The main pore types are the primary pores and the secondary pores. Secondary pores are
intragranular while primary pores are intergranular and have micropores in the matrix
 Are porous and permeable
The porosity of Xujiahe formation is less than 6
Fracture porosity
This is a kind of secondary porosity by the tectonic fracturing of rocks. The fracture does not
typically have great volume themselves but through joining the pre-existing pores assist in
enhancing their permeability significantly. The granite which is non-reservoir rocks can turn into
reservoir rocks and separation of rough surfaces into two surfaces resulting to fracture porosity
takes place. This takes place when enough fracturing takes place. Every surface can be covered

by the infilling of minerals and the whole fracture can be filled by the minerals which later
convert the open fractures to healed or sealed fractures.
In a total volume of the rock, the fracture porosity is usually small since it is about 0.0001 and
0.001. The porosity related to fractures for example in granite or carbonated reservoir may
acquire larger values but in actual fractures, it is still very tinny. It can be obtained accurately
through processing the curves of formation micro-scanner for fracture apertures and intensity of
the fracture. The approach of normal porosity calculations, the porosity, and permeability
including those attributed to fracture can be found (Tuman, 2011, p. 453).
Permeability
The measuring of connectivity between the pores spaces and the ease with which the fluid flow
through the connecting pores spaces of a rock with naturally occurring fractures in the formation
is what is known as the fracture permeability (Bucher, 2013, p. 315). The measuring of fracture
permeability is necessary so that to know hydrocarbons recovery from a reservoir or what can be
produced by the reservoir. The permeability is measured traditionally in the laboratory since it is
difficult to determine directly and the permeability of the fracture relies on the size of the grain,
the formation type, the formation porosity and the formation kind of fluid or pressure (Beiyadi,
2016, p. 219).
Types of Drilling
Drilling is a process of cutting that involves the use of a bit which cuts a circular hole in the
cross-section of a solid material (McClure, 2013, p. 549). The exploration of oil and gas in deep
formations is majorly done by the vertical and directional drilling and they are also used in
exploiting geo-resources and deep thermal energy. The natural gas and crude oil contain a

mixture of hydrocarbons, non-hydrocarbons, and other trace elements and their storage is in
sedimentary rocks of deep formation (Nassar, 2009, p. 65). Numerous methods need to be
applied to remove the gas and oil outside the deep formation.
When rock drilling a bit is usually rotated but not making a circular cutting motion. Hammering
can either be from the outside the hole or within the hole (Mader, 2015, p. 129). Drifter drills are
commonly applied. Drilling form outside is the top – hammer drill and drilling within is the
down – the hole drill.
Characteristics of drilled holes.
 Helical feed marks in the inside part of the hole.
 Burs tend to be on the exit side if not removed.
 Sharp edge on the entrance side.
All these problems and faults can be avoided by;
 By ensuring that fluids commonly used in cooling the drill bit are cut down hence
increasing the lifespan of the tool, speed, surface finish as well as aiding ejecting chips.
This fluid can be applied by flooding the working area with a coolant or a lubricant or
applying a spray mist.
 Spot drilling.
 Centre drilling.
 Deep hole method.

Types of drilling.
Conventional Drilling
Conventional wells are normally drilled in a vertical manner that is straight to the ground. This is
the traditional example of drilling.
Horizontal Drilling
The mechanisms for example bits are driven at the bottom and drillers are able to make a sharp
turn as well as horizontal drilling along a thin pay zone. The drilling of two horizontal wellbores
is done above the other, about 3 meters apart (Adwera, 2008, p. 132). One usage of this is the
Steam Assisted Gravity Drainage where the injection of steam is carried out into the higher of
these horizontal holes and the oil is precipitated down into the lower hole by the heat, leading to
increment in heavy oil production. (Ahmed, 2016, p. 123).
Slant Drilling
This is the making of drills at a perpendicular angle (commonly 300 to 450). This method inhibits
surface environmental interference (Nelson, 2009, p. 76).
Vertical Drilling
This is an advancement from slant and horizontal drilling. Directional drilling is able to change
directions and depth several times in one wellbore. The mentioned drilling method remains
exclusively suitable to pay zones in the Lloydminster area which are often distributed like prairie
sloughs across the underground landscape (Bernabe, 2009, p. 123).

CMG Software
Computer Modelling Group is a software company dealing with the production of reservoir
simulation software for the oil and gas industry (McBroom, 2013, p. 32). A three reservoir
simulation is offered by this company which includes an advanced Equation-of-state, a
conventional black oil simulator which enhances the recovery of oil and advances process
simulator (Ahmed, 2016, p. 56). How CMG simulators are being used;
 Tight reservoir modelling features
 Tight reservoir modelling features
The Computer Modelling Group starts working by following the following processes;
Working principle
The Computer Modelling Group starts operating by;
 Formation of the grid for simulation.
 Allocating porosity and permeability to the model.
 Creation of PVT data
 Creation of relative permeability data.
 Creating the initial conditions.
 Integrating routes and gaps.
 Addition of historical data to the model.
 Creation of field production history for history match.
 Addition of aquifer.
 Revising the results obtained from the simulation.
 Using Historical Data file in prediction run.

The reservoir simulation models are used by the companies dealing with gas and oil. These
models are used also in areas where production forecast are needed to assist in making decisions
relating to investment. These models may assist in improved oil recovery by hydraulic fracturing
and the Computer Modelling software may be used in in hydraulic fracturing designing as well
as improvement in oil recovery with pressure maintenance through re-injection of the gas
produced or injection of water (Carroll, 2014, p. 193).
The lowering of oil viscosity is done in order to assist in improving oil recovery and the reservoir
simulation is applied widely to obtain opportunities to upsurge the production of oil. Simulators
such as black oil is not considering the changes in composition of hydrocarbons as the field is
produced and modelling of hydrocarbons in tight matrix blocks is done by natural fracture
simulation known as dual-permeability and dual porosity (Beiyadi, 2016, p. 563).

Bibliography
Adware, P., 2008. Hydraulic Fracturing Technology. s.l.: Woongjin ThinkBig.
Ahmed, U., 2016. Unconventional Oil and Gas Resources. s.l. Scholastic.
Biriyani, H., 2016. Hydraulic Fracturing in Unconventional Reservoirs. s.l. Haufe Gruppe.
Bernabe, S., 2009. Rock Physicaqls and Natural Hazards. s.l.:Simon & Schuster.
Bucher, K., 2013. Hydrogeology of Crystalline Rocks. s.l. Adventure Works Press.
Carroll, J., 2014. Fracture, Fatigue, Failure and Damage. s.l.:Chick Publications.
Chen, W., 2016. Electrohydraulic Fracturing of Rocks. s.l.: Wiley.
Choquette, R., 2012. Carbonate Petroleum Reservoirs. s.l.:Grupo Santilla.
Fink, J., 2013. Hydraulic Fracturing Chemicals and Fluids Technology. s.l. Gakken.
Gleeson, T., 2016. Crustal Permeability. s.l. Grupo Planeta.
Howard, G., 2012. Hydraulic Fracturing. s.l.:HarperCollins.
Mader, D., 2009. Hydraulic Proppant Fracturing and Gravel Packing. s.l.:Informa.
Mader, J., 2015. hydraulic Proppant Fracturing and Gravel Packing. s.l.:Informa.
McBroom, M., 2013. The Effects of Induced Hydraulic Fracturing on the Environment. s.l. Gakken.
McClure, M., 2013. Discrete Fracture Network Modeling Of Hydraulic Stimulation. s.l. Media
Participation.
Nassar, N., 2009. Hydraulic fracturing and geothermal energy. s.l. Cassava Republic Press.
Nelson, R., 2009. Geologic Analysis of Naturally Fractured Reservoirs. s.l. Grupo Planeta.
Pointet, T., 2008. Hard Rock Hydro systems. s.l.: McGraw-Hill Education.
Sanford, W., 2010. Groundwater in Geologic Processes. s.l. Chick Publications.
Sharp, J., 2014. Fractured Rock Hydrogeology. s.l. Casemate Publisher.
Shojaei, A., 2017. Porous Rock Fracture Mechanics. s.l. OLMA Media Group.
Spellman, F., 2012. Environmental Impacts of Hydraulic Fracturing. s.l. Adventure Works Press.
Tuman, J., 2011. Acoustic Emission in a Fluid Saturated Heterogeneous Porous. s.l. Carlton Books.
Wu, Y.-S., 2018. Hydraulic Fracture Modelling. s.l.: China Publishing Company.
Wu, Y.-S., 2018. Hydraulic Fracture Modelling. s.l. Carlton Books.