Composition and Method for Preparation of a Fracturing Fluid
Field of the invention
5 [OOOl] The present invention relates to a composition and
method for preparation of a fracturing fluid. In particular, the
present invention relates to a composition and method of
preparation of a fracturing fluid capable of withstanding high
temperatures and high pressures.
10
Background of the invention
[0002] Hydraulic fracturing is a common method for
extracting hydrocarbons from underground rock formations. The
15 rock formations are fractured using a hydraulically pressurized
liquid known as fracturing fluid which is pumped through a
wellbore. The fracturing fluid reaches the end of the wellbore
where the pressure causes nearby rock formations to crack and
create fissures through which hydrocarbons along with the
20 residual fracturing fluid flow back into the well. Sand particles
present in the fracturing fluid get deposited in the fissures
and keep them open after the fracturing fluid flows back into
the well.
25 [0003] Conventionally, various fracturing fluids are used
for hydraulic fracturing (hereinafter referred to as fracking).
For example, fracturing fluid comprising water, proppants such
as sand and chemicals are used for fracking. However, existing
fracturing fluids are difficult to use when reservoir
temperature is more than 120°C due to limitations of fracturing
fluid characteristics such as stability, viscosity, proppant
5 carrying capacity and breaking time. Further, even if the
fracturing fluid is capable of withstanding high temperatures,
it is often for a limited duration after which the fracturing
fluid loses its viscoelastic characteristics thereby rendering
it unsuitable for fracking purposes. Large amount of chemicals
10 are required for preparing stable fracturing fluids capable of
carrying enough proppant for fracking at high reservoir
temperatures. However, these fracturing fluids comprising high
amount of chemicals damage underground rock formations and
environment.
15
[0004] In light of the abovementioned disadvantages, there
is a need for a fracturing fluid capable of withstanding high
temperatures and high pressures during fracking. Further, there
is a need for a fracturing fluid that maintains its viscosity,
20 proppant carrying capacity and stability at high temperatures
and high pressures. Furthermore, there is a need for a fracturing
fluid that has a high breaking time and withstands high
temperatures without changing its characteristics for a longer
duration. In addition, there is a need for an environment
25 friendly fracturing fluid that does not damage underground rock
formations during fracking.
Summary of the invention
[0005] A composition and method for preparation of a
fracturing fluid is provided. The fracturing fluid composition
5 comprises water as a base fluid. The fracturing fluid composition
further comprises one or more salts as base chemicals, an organic
polymer as a gellant and an alcohol for dissolving the gellant.
Furthermore, the fracturing fluid composition comprises acetic
acid and sodium carbonate as pH controllers and sodium
10 thiosulphate as a thermal stabilizer. In addition, the
fracturing fluid composition comprises a silicon based
surfactant to reduce surface tension of the fracturing fluid.
Also, the fracturing fluid composition comprises a gellant
breaker, wherein particle size of the gellant breaker is between
15 500 microns to 2000 microns and a crosslinker for crosslinking
the organic polymer present in the fracturing fluid.
[0006] In an embodiment of the present invention, the silicon
based surfactant is trisiloxane ethoxylate. In an embodiment of
20 the present invention, the silicon based surfactant reduces the
surface tension of the fracturing fluid to less than 10mN/m
thereby facilitating easy flow back of the fracturing fluid. In
an embodiment of the present invention, 0.2% v/v silicon based
surfactant is added to the fracturing fluid.
2 5
[0007] In an embodiment of the present invention, the
gellant breaker facilitates in extending breaking time of the
cross-linked fracturing fluid at high temperatures due to large
particle size of the gellant breaker. In an embodiment of the
present invention, 0.01% w/v gellant breaker is added to the
fracturing fluid. In an embodiment of the present invention,
wherein the gellant breaker is magnesium peroxide.
5
[OOOS] The method for preparation of the fracturing fluid
comprises a step of dissolving an organic polymer in an alcohol
to obtain a first solution, wherein the organic polymer is added
as a gellant and further wherein the alcohol facilitates
10 dissolving the organic polymer. The method further comprises a
step of adding one or more salts to water along with acetic acid
and a silicon based surfactant to obtain a second solution,
wherein the added acetic acid maintains the pH of the solution
between 6 to 6.5. Furthermore, the method comprises a step of
15 mixing the obtained first solution with the obtained second
solution. In addition, the method comprises a step of adding
sodium carbonate to the mixed solution to increase the pH of the
mixed solution between 10 to 10.5. Also, the method comprises a
step of adding sodium thiosulphate and a gellant breaker to the
20 solution obtained after adding the sodium carbonate, wherein
particle size of the gellant breaker is between 500 microns to
2000 microns. Further, the method comprises a step of adding a
crosslinker, to the solution containing sodium thiosulphate and
the gellant breaker, for crosslinking the organic polymer.
2 5
[OOOS] In an embodiment of the present invention, the
obtained first solution is mixed with the obtained second
solution till viscosity of the mixed solution is 40-50cP.
Detailed description of the invention
[OOlO] A composition and method for preparation of a
fracturing fluid capable of withstanding high temperatures and
5 high pressures is described herein. The invention provides for
a fracturing fluid that maintains its viscosity, proppant
carrying capacity and stability at high temperatures and high
pressures. Further, the invention provides for a fracturing
fluid that has a high breaking time and withstands high
10 temperatures without changing its characteristics for a longer
duration. In addition, the invention provides for an
environment-friendly fracturing fluid that does not damage
underground rock formations during fracking.
15 [OOll] The following disclosure is provided in order to
enable a person having ordinary skill in the art to practice the
invention. Exemplary embodiments are provided only for
illustrative purposes and various modifications will be readily
apparent to persons skilled in the art. The general principles
20 defined herein may be applied to other embodiments and
applications without departing from the spirit and scope of the
invention. The terminology and phraseology used is for the
purpose of describing exemplary embodiments and should not be
considered limiting. Thus, the present invention is to be
25 accorded the widest scope encompassing numerous alternatives,
modifications and equivalents consistent with the principles and
features disclosed. For the purposes of clarity, details
relating to technical material that is known in the technical
fields related to the invention have not been described in detail
so as not to unnecessarily obscure the present invention.
[0012] The invention provides a composition and process of
5 preparation of a fracturing fluid capable of withstanding high
temperatures and pressures.
[0013] The fracturing fluid comprises mainly of water. In an
embodiment of the present invention, distilled water is used for
10 preparing the fracturing fluid. Further, one or more salts used
as base chemicals are dissolved in the water. In an embodiment
of the present invention, potassium chloride is used as a base
chemical. The base chemicals prevent swelling of clay. In an
embodiment of the present invention, clay is added as a proppant.
15 In an embodiment of the present invention, 2% potassium chloride
is dissolved in the water using a magnetic stirrer at room
temperature. In an embodiment of the present invention, any salt
or combination of salts may be used as a base chemical.
20 [0014] Once the one or more salts are dissolved in the water
(also referred to as brine), a solution comprising an organic
polymer dissolved in an alcohol is added to the brine. The
organic polymer acts as a gellant and alcohol is used to dissolve
the organic polymer prior to adding the organic polymer to the
25 brine. Further, the gellant helps in reducing friction when the
fracturing fluid is pumped into wellbore for fracking. In an
embodiment of the present invention, dry powder of gellant is
slowly added in the alcohol in predefined quantities to ensure
complete dissolution and avoiding fish eye formations in the
solution. Further, while adding the gellant, the solution is
5 stirred using a stirrer set at a speed of 1500 rpm. Furthermore,
stirring is continued for another 45 seconds and then the speed
of the stirrer is reduced until disappearance of vortex. The
dissolved gellant is then mixed with the brine. In an embodiment
of the present invention, CarboxyMethyl HydroxyPropyl Guar
10 (CMHPG) is used as the gellant. In an embodiment of the present
invention, 0.4 -0.6% (w/v) CMHPG dissolved in methanol is added
to the brine. Predefined quantity of acetic acid is also added
to the above solution to maintain its pH between 6 to 6.5. The
solution is then agitated for 45 minutes slowly by the stirrer
15 for complete hydration of the solution to form a linear gel. In
an embodiment of the present invention, a silicon based
surfactant is also added to the above solution. The silicon based
surfactant facilitates in reducing surface tension of the
fracturing fluid to less that 10mN/m. In an exemplary embodiment
20 of the present invention, the silicon based surfactant is
trisiloxane ethoxylate.
[0015] Once the linear gel is prepared, sodium carbonate
(soda ash) or caustic soda is added to the linear gel to raise
25 the pH to 9-10. In an embodiment of the present invention, 0.02%
soda ash is added to the linear gel. Sodium thiosulphate or
sodium gluconate is then added to the linear gel. In an
embodiment of the present invention, 0.10 to 0.15% sodium
thiosulphate is added. Sodium thiosulphate acts as a thermal
stabilizer to reduce oxidative degradation of the fracturing
fluid and maintains viscosity at higher temperatures during
fracking. The linear gel is then sheared using a blade stirrer.
5
[0016] After shearing, the linear gel is cross-linked by
adding a cross-linker. In an embodiment of the present invention,
zirconimun cross-linker is added for cross-linking polymer
chains of CMHPG in the linear gel. Crosslinking helps in gelation
10 at higher temperatures. A gellant breaker is then added. Further,
the particle size of the gellant breaker varies from 500 microns
to 2000 microns. Furthermore, large particle size extends the
breaking time of cross-linked fracturing fluid at high
temperatures. In an embodiment of the present invention,
15 magnesium peroxide is added as the gellant breaker along with
the cross-linker. In an embodiment of the present invention,
0.010% - 0.012% (w/v) magnesium peroxide is added. In an
embodiment of the present invention, magnesium peroxide particle
size varies from 500-2000 microns. In an embodiment of the
20 present invention, the solution is mixed using a stirrer at 1000
rpm for 1 minute till the beginning of vortex closure. Further,
vortex closure is an indication of cross-linking of the gel. The
cross-linked fracturing fluid gel thus obtained is capable of
withstanding high temperatures of upto 200 degrees celsius and
25 maintaining its viscosity for at least 120 minutes during
fracking in order to carry the fracturing fluid into deeper
wells. Further, the cross-linked fracturing fluid gel is
environment friendly due to small amounts of chemicals present
in it. Furthermore, the gel is easily breakable thereby
facilitating the gel to flow back even after three hours of
£racking.
5 [0017] In an exemplary embodiment of the present invention,
3 grams CMHPG (0.6%w/v) is mixed with 50ml (10%v/v) Methanol for
efficiently mixing CMHPG and preventing fish eye formations in
the solution. Further, 500 ml tap water is mixed with 15 grams
(3% W/V) potassium chloride, 0.05 ml (O.Ol%v/v) acetic acid and
10 1 ml (0.2%v/v) of a silicon based surfactant. The silicon based
surfactant of the present invention reduces the surface tension
of the fracturing fluid to less than 10mN/m thereby facilitating
easy flow back after breaking the fluid. In an embodiment of the
present invention, the silicon based surfactant is trisiloxane
15 ethoxylate. The solution containing gellant is added to the
second solution containing brine and is mixed till the viscosity
reaches around 40-50 cP. In an embodiment of the present
invention, the solution containing gellant is mixed with the
second solution containing brine for 2-3 hours. This solution
20 has a pH 6-6.5 due to presence of acetic acid added earlier.
After sufficient hydration, 0.1 grams (0.02%w/v) sodium
carbonate is added to the above solution to raise the pH to 10-
10.5. Thereafter, 0.7 grams (0.14% w/v) sodium thiosulphate and
0.05 grams (0.01% w/v) magnesium peroxide is added to the
25 solution. Proppant is added to the above solution in a hopper.
In an embodiment of the present invention, proppant is added to
the above solution based on the fracture design and requirement
of the proppant. Further, 0.1 ml (0.02% v/v) zirconium
crosslinker is then added to the above solution containing
proppant. In an embodiment of the present invention, the
crosslinker is added to solution containing proppant in the
pipeline after the centrifugal pump and before the high pressure
5 reciprocating pump.
[0018] In an exemplary embodiment of the present invention,
the table below provides viscosity values of the cross linked
fracturing fluid gel measured using Advanced Brookefield
10 viscometer.
S.No. Average Shear Rate Viscosity (cps) Time
Temperature (Minutes)
(degree
celsius)
1 49.8 100 per sec 630 3.12
2 172.4 100 per sec 104.3 6 0
3 174.6 100 per sec 100.5 9 0
4 179.1 103.20 per 33.9 120
sec
5 179.2 69.4 per sec 40 18 0
6 179.1 69.4 per sec 4 200
[0019] In an embodiment of the present invention, the crosslinked
fracturing fluid gel is prepared using an ageing cell, a
15 roller oven, a magnetic stirrer or a mechanical stirrer, high
temperature oil bath, pH meter or pH paper, high temperature and
high pressure viscometer and general laboratory equipment.
[0020] While the exemplary embodiments of the present
20 invention are described and illustrated herein, it will be
appreciated that they are merely illustrative. It will be
understood by those skilled in the art that various modifications
in form and detail may be made therein without departing from or
offending the spirit and scope of the invention as defined by
the appended claims.
We claim:
1. A fracturing fluid composition comprising:
water as a base fluid;
5 one or more salts as base chemicals;
an organic polymer as a gellant;
an alcohol for dissolving the gellant;
acetic acid and sodium carbonate as pH controllers;
sodium thiosulphate as a thermal stabiliser;
10 a silicon based surfactant to reduce surface tension of the
fracturing fluid;
a gellant breaker, wherein particle size of the gellant breaker
is between 500 microns to 2000 microns; and
a crosslinker for crosslinking the organic polymer present in
15 the fracturing fluid.
2. The fracturing fluid composition of claim 1, wherein the
silicon based surfactant is trisiloxane ethoxylate.
20 3. The fracturing fluid composition of claim 1, wherein the
silicon based surfactant reduces the surface tension of the
fracturing fluid to less than 10mN/m thereby facilitating easy
flow back of the fracturing fluid.
4. The fracturing fluid composition of claim 1, wherein 0.2% v/v
5 silicon based surfactant is added to the fracturing fluid.
5. The fracturing fluid composition of claim 1, wherein the
gellant breaker facilitates in extending breaking time of the
cross-linked fracturing fluid at high temperatures due to large
10 particle size of the gellant breaker.
6. The fracturing fluid composition of claim 1, wherein 0.01%
w/v gellant breaker is added to the fracturing fluid.
15 7. The fracturing fluid composition of claim 1, wherein the
gellant breaker is magnesium peroxide.
8. A method for preparation of a fracturing fluid, the method
comprising the steps of:
dissolving an organic polymer in an alcohol to obtain a first
solution, wherein the organic polymer is added as a gellant and
further wherein the alcohol facilitates dissolving the organic
polymer;
adding one or more salts to water along with acetic acid and a
5 silicon based surfactant to obtain a second solution, wherein
the added acetic acid maintains the pH of the solution between
6 to 6.5;
mixing the obtained first solution with the obtained second
10 solution;
adding sodium carbonate to the mixed solution to increase the pH
of the mixed solution between 10 to 10.5;
15 adding sodium thiosulphate and a gellant breaker to the solution
obtained after adding the sodium carbonate, wherein particle
size of the gellant breaker is between 500 microns to 2000
microns; and
20 adding a crosslinker, to the solution containing sodium
thiosulphate and the gellant breaker, for crosslinking the
organic polymer.
9. The method of claim 8, wherein the silicon based surfactant
is trisiloxane ethoxylate.
10. The method of claim 8, wherein the silicon based surfactant
5 reduces the surface tension of the fracturing fluid to less than
10mN/m thereby facilitating easy flow back of the fracturing
fluid.
11. The method of claim 8, wherein 0.2% v/v silicon based
10 surfactant is added to the fracturing fluid.
12. The method of claim 8, wherein the gellant breaker
facilitates in extending breaking time of the cross-linked
fracturing fluid at high temperatures due to large particle size
15 of the gellant breaker.
13. The method of claim 8, wherein 0.01% w/v gellant breaker is
added to the fracturing fluid.
20 14. The method of claim 8, wherein the gellant breaker, added to
the solution obtained after adding sodium carbonate, is
magnesium peroxide.
15. The method of claim 8, wherein the obtained first solution
is mixed with the obtained second solution till viscosity of the
mixed solution is 40-50cP.