Composition and Process for Preparation of a Fracturing Fluid
Field of the invention
[0001] The present invention relates to a composition and
process for preparation of a fracturing fluid. In particular,
the present invention relates to a composition and process for
preparation of a polymer-free fracturing fluid comprising
viscoelasti c surfactant.
Background of the invention
[0002] Hydraulic fracturing is a common method for
extracting hydrocarbons from underground rock formations. The
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
20 with the residual fracturing fluid flow back into the well.
25
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.
[0003] Conventionally, fracturing fluids comprise gellants,
cross linkers, pH adjusters, biocides, breakers, proppants and
friction reducers. Natural or synthetic polymers are used as
2
5
gellants for increasing viscosity, suspending proppant and
reducing friction. For example, natural polymer such as guar
gum is widely used in preparation of fracturing fluid.
However, the above-mentioned fracturing fluids suffer from
various disadvantages. Preparing the above-mentioned
fracturing fluids is time consuming and expensive as these
require large amounts of additives, extensive logistics and
equipment. Further, the above-mentioned fracturing fluids
damage underground rock formations and environment due to
10 presence of large amounts of additives. Furthermore, use of
these fracturing fluids leave residues in the well that form
cakes which clog the well. Therefore, using the abovementioned
fracturing fluids require extensive well cleanup.
Also, traces of polymers are left behind in the recovered
15 hydrocarbons that are expensive to remove.
20
25
[0004] In light of the abovementioned disadvantages, there
is a need for a polymer-free fracturing fluid. Further, there
is a need for a fracturing fluid that can be prepared at the
time of fracturing or batch wise prior to fracturing.
Furthermore, there is a need for an environment-friendly and
biodegradable fracturing fluid that does not require large
amounts of additives. In addition, there is a need for a
fracturing fluid that does not leave residues thereby
facilitating easy clean-up of the well. Also, there is a need
for a fracturing fluid that gels efficiently, has adequate
proppant carrying capacity, is not cumbersome to prepare,
3
5
retains permeability and does not require a gel breaker for
flowing back into the well.
Summary of the invention
[0005] A composition and process for preparation of a
fracturing fluid is provided. The process comprises a step of
adding one or more salts to water to obtain a brine. The
process further comprises a step of adding a viscoelastic
10 surfactant to the brine to obtain a solution. Furthermore, the
process comprises a step of adding zinc oxide nanoparticles to
the solution to obtain a fracturing fluid.
15
[0006] In an embodiment of the present invention, the one
or more salts comprise potassium chloride and calcium
chloride. In an embodiment of the present invention, the
viscoelastic surfactant is amidoamine oxide derived from N-(3-
(dimethylamino) propyl) tallow amide. In an embodiment of the
present invention, the viscoelastic surfactant is
20 biodegradable. In an embodiment of the present invention, the
viscoelastic surfactant is added in an amount ranging between
4% and 8% w/w. In an embodiment of the present invention, size
of the zinc oxide nanoparticles is 25 nanometres. In an
embodiment of the present invention, the zinc oxide
25 nanoparticles are added in an amount ranging between 0.08% and
1% w/w. In an embodiment of the present invention, the process
comprises a step of adding cellulose to the solution.
4
[0007] The fracturing fluid comprises water as a base
fluid. The fracturing fluid further comprises one or more
salts. Furthermore, the fracturing fluid comprises a
viscoelastic surfactant. Also, the fracturing fluid comprises
5 zinc oxide nanoparticles.
10
15
20
Brief Description of the accompanying drawings
[0008] FIG. 1 is a graph of viscosity values with respect
to temperature for a fracturing fluid comprising 4%
viscoelastic surfactant, 3% potassium chloride and 0.5%
hydroxyethyl cellulose, in accordance with an embodiment of
the present invention;
[0009] FIG. 2 is a graph of viscosity values with respect
to temperature for a fracturing fluid comprising 5%
viscoelastic surfactant, 3% potassium chloride and 0.5%
hydroxyethyl cellulose, in accordance with an embodiment of
the present invention;
[0010] FIG. 3 is a graph of viscosity values with respect
to temperature for a fracturing fluid comprising 4%
viscoelastic surfactant, 4% potassium chloride and 0.5%
hydroxyethyl cellulose, in accordance with an embodiment of
25 the present invention;
[0011] FIG. 4 is a graph of viscosity values with respect
to temperature for a fracturing fluid comprising 5%
5
5
10
viscoelastic surfactant, 4% potassium chloride and 0.5%
hydroxyethyl cellulose, in accordance with an embodiment of
the present invention;
[0012] FIG. 5 is a graph of viscosity values with respect
to temperature for a fracturing fluid comprising 6%
viscoelastic surfactant, 4% potassium chloride and 0. 5%
hydroxyethyl cellulose, in accordance with an embodiment of
the present invention;
[0013] FIG. 6 is a graph of viscosity values with respect
to temperature for a fracturing fluid comprising 3%
viscoelastic surfactant, 4% potassium chloride and 1%
hydroxyethyl cellulose, in accordance with an embodiment of
15 the present invention;
[0014] FIG. 7 is a graph of viscosity values with respect
to temperature for a
viscoelastic surfactant,
fracturing fluid comprising
4% potassium chloride and
4%
1%
20 hydroxyethyl cellulose, in accordance with an embodiment of
the present invention; and
25
[0015] FIG. 8 is a graph of viscosity values with respect
to temperature for a fracturing fluid comprising 5%
viscoelastic surfactant, 4% potassium chloride and 1%
hydroxyethyl cellulose, in accordance with an embodiment of
the present invention.
6
Detailed description of the invention
[0016] A composition and process of preparation of a
fracturing fluid is described herein. The invention provides
5 for a polymer-free fracturing fluid that can be prepared at
the time of fracturing or batch wise prior to fracturing.
Further, the invention provides for an environment-friendly
and biodegradable fracturing fluid that does not require large
amounts of additives. Furthermore, the invention provides for
10 a fracturing fluid that does not leave residues thereby
facilitating easy clean-up of the well. Also, the invention
provides for a fracturing fluid that gels efficiently, has
adequate proppant carrying capacity, is not cumbersome to
prepare, retains permeability and does not require a gel
15 breaker for flowing back into the well.
20
[0017] 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 defined herein may be applied to other embodiments
and applications without departing from the spirit and scope
of the invention. The terminology ~nd phraseology used is for
25 the purpose of describing exemplary embodiments and should not
be considered limiting. Thus, the present invention is to be
accorded the widest scope encompassing numerous alternatives,
modifications and equivalents consistent with the principles
7
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
5 invention.
[0018] The invention provides a composition and process of
preparation of a polymer free fracturing fluid capable of
withstanding high temperatures and pressures. The fracturing
10 fluid of the present invention is prepared using water as a
base fluid. In an embodiment of the present invention,
distilled water is used for preparing the fracturing fluid.
One or more salts are added to the water to obtain brine. In
an exemplary embodiment of the present invention, potassium
15 chloride is added to water in an amount ranging from 4% to 6%
w/w. In another exemplary embodiment of the present invention,
12% calcium chloride is added to water. Once the brine is
obtained, a viscoelastic surfactant is added to the brine to
obtain a solution. In an embodiment of the present invention,
20 the viscoelastic surfactant added to the brine is amidoamine
oxide derived from N-(3-(dimethylamino) propyl) tallow amide.
Further, the viscoelastic surfactant is biodegradable and does
not damage the rock formations and environment. In an
embodiment of the present invention, the viscoelastic
25 surfactant added to the brine is Aromox APA-T in an amount
ranging from 4% to 8% w/w.
8
[0019] After adding the viscoelastic surfactant, zinc oxide
nanoparticles are added to the solution to obtain a fracturing
fluid. In an embodiment of the present invention, the zinc
oxide nanoparticles are added to the fracturing fluid to
5 maintain the viscosity of the fracturing fluid at high
10
15
temperature and high pressure. Further, the zinc oxide
nanoparticles are added in an amount ranging from 0. 08% to
1. 0% w/w. In an embodiment of the present invention, size of
the zinc oxide nanoparticles is 25 nanometres.
[0020] In an embodiment of the present invention, cellulose
is added to the fracturing fluid to improve the viscosity of
the fracturing fluid. Further, the cellulose facilitates in
maintaining viscosity of the fracturing fluid over a wide
range of temperature. In an embodiment of the present
invention, Hydroxy Ethyl Cellulose (HEC) is added in an amount
ranging from 0. 25% to 1%. In an embodiment of the present
invention, the average molecular weight of HEC ranges from
0.75 X 106 to 2 x 106 • In a preferred embodiment of the present
20 invention, the average molecular weight of HEC ranges from 1.4
X 106 to 1. 6 X 106 •
[0021] The fracturing fluid prepared using the above-
25 mentioned process has high proppant carrying capacity and
settling rate. Further, gel breaker is not required as the
viscoelastic surfactant added to the fracturing fluid loses
its viscosity when it comes into contact with the
9
hydrocarbons. The HEC, if present, in the fracturing fluid
also loses its viscosity with due course of time and therefore
readily flows back thereby minimizing the damage to the rock
formations.
5
[0022] In a preferred embodiment of the present invention,
8% w/w viscoelastic surfactant is added to a brine comprising
12% w/w calci urn chloride and water. 0.08% zinc oxide
nanoparticles are then added to the above solution to obtain a
10 polymer free fracturing fluid.
[0023] The tables below provides experimental values of
viscosity of the fracturing fluids, prepared using the process
of the present invention, at a temperature ranging from 50 to
15 90 degree Celsius.
[0024] Table l illustrates rheology of the fracturing fluid
comprising 4% VES (Aromox), 3% KCl, 0.5% HEC and 0.8%-1% zinc
oxide nanoparticles in water.
20
Table 1
VES KCl in Temperature Viscosity Viscosity Viscosity
in w/w at shear at shear of at shear
w/w of 3 rpm 100 rpm of 300
rpm
4% 3% 50 200 30 20
4% 3% 60 100 21 15
4% 3% 70 100 15 10
4% 3% 80 100 15 7
4% 3% 90 100 12 6
10
[0025] FIG. 1 is a graph of viscosity values with respect
to temperature for a fracturing fluid comprising 4%
viscoelast i c surfactant, 3% potassium chloride and 0.5%
5 hydroxyethyl cellulose corresponding to table 1, in accordance
with an embodiment of the present invention.
[0026] Table 2 illustrates rheology of the fracturing fluid
comprising 5% VES (Aromox), 3% KCl, 0.5% HEC and 0.8% to 1%
10 zinc oxide nanoparticles in water.
Table 2
VES KCl in Temperature Viscosity Viscosity Viscosity
in w/w at shear at shear of at shear
w/w of 3 rpm 100 rpm of 300
rpm
5% 3% 50 300 48 31
5% 3% 60 300 39 24
5% 3% 70 100 27 19
5% 3% 80 100 18 13
5% 3% 90 100 12 8
[0027] FIG. 2 is a graph of viscosity values with respect
to temperature for a fracturing fluid comprising 5%
15 viscoelastic surfactant, 3% potassium chloride and 0.5%
hydroxyethyl cellulose corresponding to table 2, in accordance
with an embodiment of the present invention.
11
[0028] Table 3 illustrates rheology of the fracturing fluid
comprising 4% VES (Aromox), 4% KCl, 0.5% HEC and 0.8% to 1%
zinc oxide nanoparticles in water at low shear.
Table 3
VES KCl in Temperature Viscosity Viscosity Viscosity
in w/w at shear at shear of at shear
w/w of 3 rpm 100 rpm of 300
rpm
4% 4% 50 400 78 45
4% 4% 60 300 60 40
4% 4% 70 200 42 26
4% 4% 80 200 30 22
4% 4% 90 200 24 18
5 [0029] FIG. 3 is a graph of viscosity values with respect
to temperature for a fracturing fluid comprising 4%
viscoelastic surfactant, 4% potassium chloride and 0.5%
hydroxyethyl cellulose corresponding to table 3, in accordance
with an embodiment of the present invention.
10
[0030] Table 4 illustrates rheology of the fracturing fluid
comprising 5% VES (Aromox), 4% KCl, 0.5% HEC and 0.8% to 1%
zinc oxide nanoparticles in water ( 8 9. 5% to 8 9. 7%) at low
shear.
Table 4
VES KCl in Temperature Viscosity Viscosity Viscosity
in w/w at shear at shear of at shear
w/w of 3 rpm 100 rpm of 300
rpm
5% 4% 50 600 108 58
12
5% 4% 60 500 81 48
5% 4% 70 400 66 40
5% 4% 80 200 39 29
5% 4% 90 200 24 19
[0031] FIG. 4 is a graph of viscosity values with respect
to temperature for a fracturing fluid comprising 5%
viscoelastic surfactant, 4% potassium chloride and 0.5%
5 hydroxyethyl cellulose corresponding to table 4, in accordance
with an embodiment of the present invention.
[0032] Table 5 illustrates rheology of the fracturing fluid
comprising 6% VES (Aromox), 4% KCl, 0.5% HEC and 0.8% to 1%
10 zinc oxide nanoparticles in water at low shear.
Table 5
VES KCl in Temperature Viscosity Viscosity Viscosity
in w/w at shear at shear of at shear
w/w of 3 rpm 100 rpm of 300
rpm
6% 4% 50 900 144 70
6% 4% 60 500 120 66
6% 4% 70 400 105 59
6% 4% 80 200 57 40
6% 4% 90 300 30 25
[0033] FIG. 5 is a graph of viscosity values with respect
to temperature for a fracturing fluid comprising 6%
viscoelastic surfactant, 4% potassium chloride and 0. 5%
13
hydroxyethyl cellulose corresponding to table 5, in accordance
with an embodiment of the present invention.
(0034] Table 6 illustrates rheology of the fracturing fluid
5 comprising 3% VES (Aromox), 4% KCl, 1% HEC and 0.8% to 1% zinc
oxide nanoparticles in water at low shear.
Table 6
VES KCl in Temperature Viscosity Viscosity Viscosity
in w/w at shear at shear of at shear
w/w of 3 rpm 100 rpm of 300
rpm
3% 4% 50 600 150 85
3% 4% 60 300 105 67
3% 4% 70 200 115 52
3% 4% 80 200 71 37
3% 4% 90 100 30 20
(0035] FIG. 6 is a graph of viscosity values with respect
to temperature for a fracturing fluid comprising 3%
10 viscoelastic surfactant, 4% potassium chloride and 1%
hydroxyethyl cellulose corresponding to table 6, in accordance
with an embodiment of the present invention.
(0036] Table 7 illustrates rheology of the fracturing fluid
15 comprising 4% VES (Aromox), 4% KCl, 1% HEC and 0.8% to 1% zinc
oxide nanoparticles in water at low shear.
14
Table 7
VES KCl in Temperature Viscosity Viscosity Viscosity
in w/w at shear at shear of at shear
w/w of 3 rpm 100 rpm of . 300
rpm
4% 4% 50 900 213 110
4% 4% 60 600 159 92
4% 4% 70 400 123 76
4% 4% 80 300 84 56
4% 4% 90 100 45 34
[0037] FIG. 7 is a graph of viscosity values with respect
to temperature for a fracturing fluid comprising 4%
viscoelastic surfactant, 4% potassium chloride and 1%
5 hydroxyethyl cellulose corresponding to table 7, in accordance
with an embodiment of the present invention.
[0038] Table 8 illustrates rheology of the fracturing fluid
comprising 5% VES (Aromox), 4% KCl, 1% HEC and 0.8% to 1% zinc
10 oxide nanoparticles in water at low shear.
Table 8
VES KCl in Temperature Viscosity Viscosity Viscosity
in w/w at shear at shear of at shear
w/w of 3 rpm 100 rpm of 300
rpm
5% 4% 50 1400 264 120
5% 4% 60 800 201 110
5% 4% 70 600 165 96
5% 4% 80 400 129 80
15
[0039] FIG. 8 is a graph of viscosity values with respect
to temperature for a fracturing fluid comprising 5%
viscoelastic surfactant, 4% potassium chloride and 1%
5 hydroxyethyl cellulose corresponding to table 8, in accordance
with an embodiment of the present invention.
[0040] Table 9 illustrates rheology of the fracturing fluid
comprising 8% VES (Aromox), 12% Calcium chloride and 0.08%
10 zinc oxide nanoparticles in 79.92% water at a shear rate of
100.
Table 9
VES in Calcium Temperature Viscosity Shear
w/w Chloride (Cp) Stress (Pa)
in w/w
8% 12% 60 54 5.8
8% 12% 70 76.4 7.69
8% 12% 80 154 14.9
8% 12% 90 83.5 8.3
[0041] Table 10 illustrates rheology of the fracturing
15 fluid comprising 8% VES (Aromox) and 12% Calcium chloride at a
shear rate of 100 without any zinc oxide nanoparticles.
Table 10
VES in Calcium Temperature Viscosity at shear
w/w Chloride in of 3 rpm
w/w
8% 12% 60 51
16
8% 12% 70 54
8% 12% 80 63
8% 12% 90 84
[0042] On comparing values of Table 9 and Table 10, it is
observed that adding zinc oxide nanoparticles to the
fracturing fluid facilitates in maintaining the viscosity of
5 the fracturing fluid at high temperatures.
10
15
[0043]
rate for
invention.
proppant
(ppg) in
ml
8
8
8
8
[0044]
Table 11 illustrates values of proppant settling
fracturing fluids prepared using the present
Table 11
VES % + KCl % + Temp (oC) Time of
100 HEC % settling in
minutes
3+4+1 80 8
4+4+1 80 10
3+4+0.5 80 4
4+4+0.5 80 5
While the exemplary embodiments of the present
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
17
5
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.
18
5
10
15

We claim:
1. A process for preparation of a fracturing fluid, the
process comprising the steps of:
a) adding one or more salts to water to obtain a brine;
b) adding a viscoelastic surfactant to the brine to
obtain a solution; and
c) adding zinc oxide nanoparticles to the solution to
obtain a fracturing fluid.
2. The process as claimed in claim 1, wherein the one or more
salts comprise potassium chloride and calcium chloride.
3. The process as claimed in claim 1, wherein the viscoelastic
surfactant is amidoamine oxide derived from N-(3-
(dimethylamino) propyl) tallow amide.
20 4. The process as claimed in claim 1, wherein the viscoelastic
surfactant is biodegradable.
5. The process as claimed in claim 1, wherein the viscoelastic
surfactant is added in an amount ranging between 4% and 8%
25 w/w.
6. The process as claimed in claim 1, wherein size of the zinc
oxide nanoparticles is 25 nanometres.
19
5
10
7. The process as claimed in claim 1, wherein the zinc oxide
nanoparticles are added in an amount ranging between 0.08% and
1% w/w.
8. The process as claimed in claim 1 comprising the step of
addi ng cellulose to the solution.
9. A fracturing fluid comprising:
water as a base fluid;
one or more salts;
a viscoelastic surfactant; and
zinc oxide nanoparticles.
15 10. The fracturing fluid as claimed in claim 9, wherein the
one or more salts comprise potassium chloride and calcium
chloride.
11. The fracturing fluid as claimed i n claim 9, wherein the
20 viscoelastic surfactant is amidoamine oxide derived from N-(3-
(dimethylamino) propyl) tallow amide.
25
12. The fracturing fluid as claimed in claim 9, wherein the
viscoelastic surfactant is biodegradable.
13. The fracturing fluid as claimed in claim 9, wherein the
viscoelastic surfactant is in an amount ranging between 4% and
8% w/w.
20
14. The fracturing fluid as claimed in claim 9, wherein size
of the zinc oxide nanoparticles is 25 nanometres.
5 15. The fracturing fluid as claimed in claim 9, wherein the
zinc oxide nanoparticles are in an amount ranging between
0.08% and 1% w/w .
16. The fracturing fluid as claimed in claim 9 comprising
10 cellulose.