Note: Descriptions are shown in the official language in which they were submitted.
LYPOOOOCADOO
HIGH TEMPERATURE-RESISTANT FULLY-SUSPENDED LOW-
DAMAGE FRACTURING FLUID AND PREPARING METHOD THEREOF
CROSS-REFERENCE TO RELATED APPLICATIONS
This application claims the benefit of priority of Chinese Application No.
201910059140.9 filed
Jan 22, 2019.
BACKGROUND OF THE INVENTION
(1) Field of the Invention
The present invention relates to the field of oilfield chemical technology, in
particular, to a high
temperature-resistance fully-suspended low-damage fracturing fluid.
(2) Description of the Related Art
Fracturing liquid is a fluid used in the fracturing operation for fracture
creation and transporting
proppants along the length of the fracture, and is one of the key factors that
determine the success
or failure of operation and construction results. A successful and efficient
fracturing operation
requires fracturing fluids with many excellent performance characteristics,
the most important of
which are (1) universal water quality applicability, (2) wide range of
temperature adaptation, (3)
excellent shear resistance, (4) efficient sand-carrying performance, and (5)
minimal damage
characteristics.
Since the 1960s, guar gum fracturing fluids have dominated fracturing
operations. Although these
fracturing fluids are constantly improving and improving their performance,
they have exposed
many problems in the above-mentioned various performances due to the nature
and structural
features of natural polymers therein. In the past 20 years, the research and
development for
synthesis of polymer-based fracturing fluids has fundamentally solved many
problems in guar gum
fracturing fluids. However, polymer-based fracturing fluids still have some
shortcomings that
require further enhancement and improvement.
For example, Chinese Patent CN106928959A disclosed a fully-suspended
fracturing fluid and a
matching cross-linking agent, wherein the cross-linking agent is prepared from
the following
components in parts by weight: 6 to 12 parts of a water-soluble high-valent
metal salt, 8 to 16 parts
of a polyhydric alcohol, and 4 to 10 parts of a carboxylic acid or a salt
thereof. The fully-suspended
fracturing fluid prepared by mixing a thickening agent with at least one of an
anti-swelling agent,
1
CA 3055128 2020-02-18
LYPOOOOCADOO
a drainage-aiding agent, and a viscosity retention agent, and then cross-
linking the mixture with
the above cross-linking agent has a highest temperature to be resisted of 130
C, wherein the
sedimentation rate of the proppant is set at a rate of 2 mm/h at 90 C.
Chinese Patent
CN103215028B disclosed a fully-suspended fracturing fluid comprising the
following components
in parts by weight: 4 to 15 parts of a fully-suspended fracturing fluid
thickening agent; 100 parts
of water, aggravated brine or acid; wherein the thickening agent is a mixture
composed of 35-55%
of dimethyl bis-hexadecyl octadecyl chloride or a derivative thereof, 5 to 15%
of a
polycondensation phosphate, 5 to 10% of a shielding filtrate loss reducer, and
20 to 50% of water.
The fracturing fluid is actually a weighted fracturing fluid of a viscoelastic
surfactant type, which
enhances the suspension of proppant by increasing the density of the liquid,
with a density of 1.3-
2. 2g/cm3, having a specific gravity of sand of 50% and a highest temperature
to be resisted being
120 C. Chinese Patent CN104178102A disclosed a cross-linkable high temperature-
resistance low-
damage multi-component copolymer fracturing fluid and a preparation method
thereof comprising
a preparation method of thickening agent for fracturing fluid, cross-linking
agent for fracturing
fluid and gel breaker for fracturing fluid, and a method of preparing
fracturing fluid using several
additives. The fracturing fluid can be "physically cross-linked" to form a
jelly with a reversible
structure, has excellent temperature-resistance, and has residue content as
low as 2 mg/L. However,
the fracturing fluid has not been disclosed or elaborated in terms of the
performance of its sand-
carrying performance.
BRIEF SUMMARY OF THE INVENTION
One object of the present invention is to provide a high temperature-
resistance fully-suspended
low-damage fracturing fluid for the deficiencies of polymeric fracturing
fluids.
Another object of the present invention is to provide a method for preparing a
high temperature-
resistance fully-suspended low-damage fracturing fluid.
The high temperature-resistance fully-suspended low-damage fracturing fluid
includes the
following weight percent components: 0.3% to 0.5% of a low-damage thickening
agent, 0.1% to
0.4% of a multi-functional stabilizer; 0.1% to 0.3% of a regulator; 0.4% to
0.8% of a suspension
synergist, and a remaining component is clean water or brine.
The low-damage thickening agent is formed by a copolymer of a main-chain
monomer A, a main-
2
CA 3055128 2019-09-12
LYPOOOOCADOO
chain monomer B, a salt-tolerant monomer, and a promote cross-linking monomer
for promoting
polymerization reaction; wherein the main chain monomer A is acrylamide; the
main-chain
monomer B acrylic acid or sodium acrylate; the salt-tolerant monomer is one or
two of 2-
acrylamido-2-phenylethanesulfonic acid, N-vinylpyrrolidone, N-allyl imidazole,
vinylphosphonic
acid; and the promote cross-linking monomer is one of N-vinylcaprolactam, N,N-
methylenebisacrylamide, diacetone acrylamide, and N-methylol acrylamide.
Preferably, the salt-
tolerant monomer is a mixture of N-allyl imidazole or vinylphosphonic acid or
a mixture of both
with equivalent weights.
Preferably, the thickening agent is produced by Chengdu Duan Petroleum
Technology Co., Ltd.,
with product code of BCG-1XF. The product is white particles or powder of <80
mesh, and the
apparent molecular weight is 2 to 3 millions. Further, the product meets the
following basic
performance indicators: moisture <10%; insoluble content <0.2%; when using tap
water
preparation (0.5% dosage), the viscosity at room temperature is <3min; the
viscosity of the base
liquid is 70-80mPa.s.
In one embodiment, the multi-functional stabilizer is an aqueous solution
containing a component
A and a component B; the component A is one of sodium gluconate, sodium
iminodisuccinate,
sodium ethylened i am inetetraacetate, sorb itol, hydroxyethylethylenedi am i
netri aceti c acid, or a
mixture of two with equivalent amount, and has a content is 5% to 8%; and the
component B is
one of methanol, ascorbic acid, sodium sulfite, and sea wave, and has a
content is 15% to 20%.
Preferably, the multi-functional stabilizer is produced by Chengdu Yanyou
Petroleum Co., Ltd.,
with the product code of BC-5, and the product is a colorless or light yellow
transparent liquid.
In one embodiment, the suspension synergist is compounded by a thickening
synergist, a cross-
linking agent and water in a mass ratio of 3:1:1.
In one embodiment, the thickening synergist is composed of the following mass
percentage:8% to
12% of a surfactant A, 10% to 15% of a surfactant B, 5% to 10% of an alcohol
solvent A, and a
remaining component is water; wherein the surfactant A is one of sodium
dodecyl diphenyl ether
disulfonate, sodium dodecyl dinaphthalene sulfonate, isopropanolamine dodecyl
benzene sulfonate,
sodium dodecyl benzene sulfonate, dodecyl dihydroxy Ethyl betaine; the
surfactant B is one of
Coconut oil fatty acid diethanolamide and alkyl glycoside APG; and the alcohol
solvent A is one
3
CA 3055128 2019-09-12
LYPOOOOCADOO
of methanol, ethylene glycol, and glycerin.
In one embodiment, the cross-linking agent is one of an organoaluminum
crosslinking agent, an
organic titanium delayed crosslinking agent, and an organozirconium delayed
crosslinking agent.
In one embodiment, the regulator is an acid regulator or an alkaline
regulator; the acid regulator is
composed of 5% to 10% of citric acid or acetic acid, 8% to 10% of alcohol
solvent B and 80% to
87% of water; the alkaline regulator is one of sodium carbonate,
triethanolamine, ethylenediamine,
and sodium hydrogencarbonate; and the alcohol solvent B is one of ethylene
glycol, glycerin,
xylitol, and methanol. When the cross-linking agent in the suspension
synergist is an
organoaluminum cross-linking agent, a PH value is adjusted to 5 to 6.5 by
using an acidic regulator;
when the cross-linking agent in the suspension synergist is an organotitanium
retarding cross-
linking agent or an organic zirconium retarding cross-linking agent, the PH
value is dajusted to 8
to 10 by using an alkaline regulator.
In one embodiment, a salinity of the brine is 0 to 150,000 ppm, a content of
Ga2+ in the brine is
less than 3000 ppm, a content of Mg2+ is less than 15000 ppm, and a total
content of Fe2+ and Fe3+
__ is less than 5 ppm.
The method for preparing a high temperature-resistance fully-suspended low-
damage fracturing
fluid includes two steps of preparing a base fracturing fluid and preparing a
fully-suspended
fracturing fluid, and the specific steps are as follows: step 1: under a
stirring condition, adding a
low-damage thickening agent, a multi-functional stabilizer and a regulator
into water or brine; and
after stirring uniformly, swelling 2 to 4 hours to obtain a base fracturing
fluid; and step 2: throughly
mixing the base fracturing fluid and a suspension synergist; and under a joint
action of physical
cross-linking and chemical cross-linking, forming a fully-suspended fracturing
fluid with high
sand-carrying performance and high temperature-resistance.
Compared with the prior art, the present invention has the following
beneficial effects.
The fracturing fluid of the present invention is a super-strong structural
fluid formed by an
acrylamide polymer and a suspension synergist, and has the following
characteristics:
A thickening agent is introduced into a group that can be "physically cross-
linked" and "chemically
cross-linked", and a mixture of a special surfactant and cross-linking agent
having physical and
chemical cross-linking function is selected as the suspension synergist, and a
viscoelastic cross-
CA 3055128 2019-09-12
LYPOOOOCADOO
linked gel is formed by the suspension synergist and thickening solution
molecule. A strong spatial
network structure is formed by the combination of two kinds of "cross-linking"
actions.
The mineralization resistance can be adjusted by a high-salinity brine dosing
with a salinity less
than 150,000 ppm.
The high temperature-resistance of the fracturing fluid prepared with clear
water can reach 150 C;
and the high temperature-resistance of the fracturing fluid prepared with the
high-salinity brine
having a 150,000 ppm salinity can be up to 140 C.
The shear speed is high, and the 800s-I high shear has little damage to the
fracturing fluid structure;
after continuous shearing for 120 min at 100 s-I, the apparent viscosity is
greater than 50mPa.s.
The sand-carrying performance is excellent, and strong space structure can
fully suspend the
proppant, which is less affected by temperature. After continuous shearing for
120 min at 1005-I,
the apparent viscosity is greater than 50 mPa.s; after the 30-50 mesh proppant
is added to the fully-
suspended low-damage fracturing fluid at a specific gravity of sand of 20% for
maintaining the
temperature at 90 C for 1 h, the sedimentation rate of proppant is less than
5%.
It has low damage, the insoluble content of the thickening agent is as low as
0.1%, which reduces
reservoir damage and significantly improves the transformation effect of oil
and gas reservoirs.
Other advantages objects, and features of the present invention will be set
forth in part in the
description below. Some will also be understood by those skilled in the art
from the study and
practice of the present invention.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a structural diagram of a conventional guar gum prepared with clear
water.
FIG. 2 is a microscopy scan view of a fully-suspended low-damage fracturing
fluid prepared with
clear water in Embodiment 1.
FIG. 3 is a diagram showing a performance test curve of temperature and shear
speed of a fully-
suspended low-damage fracturing fluid in Embodiment 6-1.
FIG. 4 is a diagram showing a performance test curve of temperature and shear
speed of a fully-
suspended low-damage fracturing fluid in Embodiment 7-1.
5
CA 3055128 2019-09-12
LYPOOOOCADOO
FIG. 5 is a diagram showing a performance test curve of temperature and shear
speed of a fully-
suspended low-damage fracturing fluid in Embodiment 8-3.
FIG. 6 is a diagram showing a performance test curve of temperature and shear
speed of a fully-
suspended low-damage fracturing fluid in Embodiment 5-2.
DETAILED DESCRIPTION
The present invention will be further described in detail below with reference
to the accompanying
drawings, so that those skilled in the art can implement according to the
description.
It is to be understood that the terms "having", "comprising", and "including",
as used herein, do
not denote the presence or addition of one or more other elements or
combinations thereof. Both
experimental conditions and experimental methods for evaluating the
performance of the high tem-
perature-resistance fully-suspended low-damage fracturing fluid involved in
the embodiments are
referred to "SY/T5107-2005 Water-based Fracturing liquid Performance
Evaluation Method". The
percent number "%" referred to in the embodiments is a mass percentage unless
otherwise specified.
Embodiment 1
A high temperature-resistance fully-suspended low-damage fracturing fluid,
based on 100 parts by
weight, has the contents of each component as follows:
0.3 to 0.5 parts of low-damage thickening agent, 0.1 to 0.4 parts of multi-
functional stabilizer; 0.1
to 0.3 parts of regulator; 0.4 to 0.8 parts of suspension synergist, and the
remaining component is
clean water or brine within a certain degree of salinity.
Among which, the low-damage thickening agent is formed by a mixture of the
main chain mono-
mer A "acrylamide", the main chain monomer B "sodium acrylate", the salt-
tolerant monomer "2-
acrylamido-2-phenylethanesulfonic acid and N-allyl with equal weights", and a
promote cross-
linking monomer "N-vinylcaprolactam" for promoting polymerization reaction.
The thickening
agent is produced by Chengdu BaiChun Petroleum Technology co., LTD., with
product code of
BCG-1XF-1. The product is white particles or powder of <80 meshes and the
apparent molecular
weight is 2 to 3 millions. Further, basic performance index achieved by the
product: water of <10%,
insoluble content of <0.2%; when using tap water for preparation (0.5%
dosage), its viscosity is of
<3 min and its viscosity of the base liquid is 70-80 mPa.s at room
temperature.
6
CA 3055128 2019-09-12
LYPOOOOCADOO
The multi-functional stabilizer is produced by Chengdu BaiChun Petroleum
Technology co., LTD.,
with product code of BC-5-1. The product is a colorless or light yellow
transparent liquid, the
composition and content of which are: sorbitol and
hydroxyethylethylenediaminetriacetic acid are
used in a mass ratio of 1:1, and the total content is 6%; the sodium sulfite
content is 16%; and the
water content is 78%.
The suspension synergist is produced by Chengdu BaiChun Petroleum Technology
co., LTD., with
product code of B-555-1. The product is a colorless to pale yellow transparent
viscous liquid, and
is compounded by a thickening synergist B-55-1, a cross-linking agent and
water in a mass ratio of
3:1:1, wherein the thickening synergist B-55-1 and the cross-linking agent are
products of Chengdu
.. BaiChun Petroleum Technology co., LTD.
The components of the thickening synergist B-55-1 are as follows: 10% of
sodium dodecyl diphe-
nyl ether disulfonate, 12% of coconut oil fatty acid diethanolamide, 6% of
methanol, and 72% of
water.
The cross-linking agent is an organic zirconium delayed cross-linking agent.
The regulator is an
alkaline regulator of ethylenediamine, and the pH value of the fracturing
fluid is controlled at 8-9.
When the dosing water of the fracturing fluid is brine, the salinity is 0 to
150,000 ppm. Further, in
the brine, the content of Ga2+ is less than 3000 ppm, the content of Mg2+ is
less than 15000 ppm,
and the sum of Fe2+ and Fe3+ is less than 5 ppm.
The method for preparing high temperature-resistance fully-suspended low-
damage fracturing
fluid includes preparing a base fracturing fluid and preparing a fully-
suspended fracturing fluid,
which include: adding the low-damage thickening agent, the multi-functional
stabilizer and the
regulator to water to form a uniform liquid under circulation or agitation,
and then swelling for
2-4h, to obtain the base fracturing fluid; then, mixing the base fracturing
fluid thoroughly with the
suspension synergist to form a fully-suspended fracturing fluid in excellent
sand-carrying perfor-
mance and temperature-resistance under the action of physical cross-linking
and chemical cross-
linking.
The results obtained by testing the performance of the fracturing fluid show
that the fracturing fluid
prepared with clean water may withstand temperature up to 150 C, while the
fracturing fluid pre-
7
CA 3055128 2019-09-12
LYPOOOOCADOO
pared with 150000 ppm mineralized brine may withstand temperature up to 140
C. After contin-
uous shearing for 120 min at 100s-1, the apparent viscosity is greater than 50
mPa.s; after the 30-
50 mesh proppant is added to the fully-suspended low-damage fracturing fluid
at a specific gravity
of sand of 20% for maintaining the temperature at 90 C for 1 h, the
sedimentation rate of proppant
is less than 5%.
The structure of the fracturing fluid prepared in the present embodiment is
compared with the
structure of a conventional guar gum. Fig. 1 is a view showing the structure
of a conventional guar
gum prepared using clear water. Fig. 2 is a view showing the structure of
fully-suspended low-
damage fracturing fluid prepared using clear water in Embodiment 1. It can be
seen that both the
conventional guar gum and the fracturing fluid in Embodiment 1 have a mesh
structure, but the
mesh structure in Embodiment 1 is more uniform, in which the mesh distribution
is uniform and
dense, and the size is uniform. This is because the thickening agent of the
present invention intro-
duces groups which may be "physically cross-linked" and "chemically cross-
linked", and the sus-
pension synergist is mixed with the special surfactant and cross-linking agent
to have physical and
chemical cross-linking effects so as to form a viscoelastic cross-linked gel
with the thickening
solution molecules, so that a strong spatial mesh structure is formed by the
combination of two
kinds of "cross-linking".
Embodiment 2
A high temperature-resistance fully-suspended low-damage fracturing fluid,
based on 100 parts by
weight, has the contents of each component as follows:
0.3 to 0.5 parts of low-damage thickening agent, 0.1 to 0.4 parts of multi-
functional stabilizer; 0.1
to 0.3 parts of regulator; 0.4 to 0.8 parts of suspension synergist, the
remaining component is clean
water or brine within a certain degree of salinity.
Among which, the low-damage thickening agent is formed by a mixture of a main
chain monomer
A "acrylamide", a main chain monomer B "acrylic acid", a salt-tolerant monomer
"N-vinyl pyrrol-
idone and N-allyl imidazole with equal weights", and a promote cross-linking
monomer "N-vi-
nylcaprolactam" for promoting polymerization reaction. The thickening agent is
produced by
Chengdu BaiChun Petroleum Technology co., LTD., with product code of BCG-1XF-
1, and the
basic performance index reached is the same as in Embodiment 1.
8
CA 3055128 2019-09-12
LYPOOOOCADOO
The multi-functional stabilizer is produced by Chengdu BaiChun Petroleum
Technology co., LTD.,
with product code of BC-5-1. The product is a colorless or light yellow
transparent liquid, the
composition and content of which are: sorbitol and
hydroxyethylethylenediaminetriacetic acid are
used in a mass ratio of 1:1, and the total content is 6%; the sodium sulfite
content is 16%; and the
water content is 78%.
The suspension synergist is produced by Chengdu BaiChun Petroleum Technology
co., LTD., with
product code of B-55S-2. The product is a colorless to pale yellow transparent
viscous liquid, and
is compounded by a thickening synergist B-55-2, a cross-linking agent and
water in a mass ratio of
3:1:1, wherein the thickening synergist B-55-2 and the cross-linking agent are
products of Chengdu
BaiChun Petroleum Technology co., LTD.
The thickening synergist B-55-2 consists of 8% of sodium dodecyl dinaphthalene
sulfonate, 10%
of coconut oil fatty acid diethanolamide, 5% of methanol, and 77% of water.
The cross-linking agent is an organic aluminum cross-linking agent. The
regulator is an acid regu-
lator composed of 6% of citric acid, 8% of ethylene glycol, 86% of water, and
the pH of the frac-
turing fluid is controlled at 5-6.
The dosing water of the fracturing fluid is brine, wherein the salinity is 0
to 150000 ppm. Further,
in the brine, the content of Ga2+ is less than 3000 ppm, the content of Mg2+
is less than 15000 ppm,
and the sum of Fe2+ and Fe3+ is less than 5 ppm.
The fracturing fluid is prepared in the same manner as in Embodiment 1.
The results obtained by testing the performance of the fracturing fluid show
that the fracturing fluid
prepared with clean water may withstand temperatures up to 150 C, while the
fracturing fluid
prepared with 150000 ppm mineralized brine may withstand temperatures up to
140 C. After con-
tinuous shearing for 120 min at 100s-1, the apparent viscosity is greater than
50 mPa.s; after the 30-
50 mesh, proppant is added to the fully-suspended low-damage fracturing fluid
at a specific gravity
of sand of 20% for maintaining the temperature at 90 C for 1 h, the
sedimentation rate of proppant
is less than 5%.
Embodiment 3
9
CA 3055128 2019-09-12
LYP0000CADOO
A high temperature-resistance fully-suspended low-damage fracturing fluid,
based on 100 parts by
weight, has the contents of each component as follows:
0.3 to 0.5 parts of low-damage thickening agent, 0.1 to 0.4 parts of multi-
functional stabilizer; 0.1
to 0.3 parts of regulator; 0.4 to 0.8 parts of suspension synergist, the
remaining components are
clean water or brine within a certain degree of salinity.
Among which, the low-damage thickening agent is formed by a mixture of a main
chain monomer
A "acrylamide, a main chain monomer B "acrylic acid", a salt-tolerant monomer
"N-allyl imidaz-
ole", and a promote cross-linking monomer "N-vinylcaprolactam" for promoting
polymerization
reaction. The thickening agent is produced by Chengdu BaiChun Petroleum
Technology co., LTD.,
with product code of BCG-1XF-3, and the basic performance index reached is the
same as in Em-
bodiment 1.
The multi-functional stabilizer BC-5-2 is a colorless or light yellow
transparent liquid, the compo-
sition and content of which are: sorbitol and iminodisuccinate sodium salt are
used in a mass ratio
of 1:1, and the total content is 8%; the sodium hyposulfite content is 20%;
and the water content is
72%.
The suspension synergist is produced by Chengdu BaiChun Petroleum Technology
co., LTD., with
product code of B-55S-2. The product is a colorless to pale yellow transparent
viscous liquid, and
is compounded by a thickening synergist B-55-3, a cross-linking agent and
water in a mass ratio of
3:1:1, wherein the thickening synergist B-55-3 and the cross-linking agent are
products of Chengdu
BaiChun Petroleum Technology co., LTD.
The thickening synergist B-55-3 consists of 8% of dodecylbenzenesulfonic acid
isopropanolamine
salt, 12% of 8-10 alkyl glycoside APG, 8% of ethylene glycol, and 72% of
water.
The cross-linking agent is an organic zirconium delayed cross-linking agent.
The regulator is an
alkaline regulator of triethanolamine, and the pH of the fracturing fluid is
controlled at 8-9. The
dosing water of the fracturing fluid is brine, wherein the salinity is 0 to
150000 ppm. Further, in
the brine, the content of Ga2+ is less than 3000 ppm, the content of Mg2+ is
less than 15000 ppm,
and the sum of Fe2+ and Fe3+ is less than 5 ppm.
The fracturing fluid is prepared in the same manner as in Embodiment 1.
CA 3055128 2019-09-12
LYPOOOOCADOO
The results obtained by testing the performance of the fracturing fluid show
that the fracturing fluid
prepared with clean water may withstand temperatures up to 150 C, while the
fracturing fluid
prepared with 150000 ppm mineralized brine may withstand temperatures up to
140 C. After con-
tinuous shearing for 120 min at 100s-1, the apparent viscosity is greater than
50 mPa.s; after the 30-
50 mesh proppant is added to the fully-suspended low-damage fracturing fluid
at a specific gravity
of sand of 20% for maintaining the temperature at 90 C for 1 h, the
sedimentation rate of proppant
is less than 5%.
Embodiment 4
A high temperature-resistance fully-suspended low-damage fracturing fluid,
based on 100 parts by
weight, has the contents of each component as follows:
0.3 to 0.5 parts of low-damage thickening agent, 0.1 to 0.4 parts of multi-
functional stabilizer; 0.1
to 0.3 parts of regulator; 0.4 to 0.8 parts of suspension synergist, the
remaining components are
clean water or brine within a certain degree of salinity.
Among which, the low-damage thickening agent is formed by a mixture of a main
chain monomer
A "acrylamide, a main chain monomer B "acrylic acid", a salt-tolerant monomer
"N-allyl imidaz-
ole", and a promote cross-linking monomer "N-vinylcaprolactam" for promoting
polymerization
reaction. The thickening agent is produced by Chengdu BaiChun Petroleum
Technology co., LTD.,
with product code of BCG-1XF-4, and the basic performance index reached is the
same as in Em-
bodiment 1.
The multi-functional stabilizer BC-5-2 has components and content as follows:
sorbitol and imi-
nodisuccinate sodium salt are used in a mass ratio of 1:1, and the total
content is 8%; the sodium
hyposulfite content is 20%; and the water content is 72%.
The suspension synergist B-55S-4 is compounded by the thickening synergist B-
55-3, a cross-
linker and water in a mass ratio of 3:1:1. The thickening synergist B-55-3
consists of 8% of do-
decylbenzenesulfonic acid isopropanolamine salt, 12% of 8-10 alkyl glycoside
APG, 8% of eth-
ylene glycol, and 72% of water.
The cross-linking agent is an organic aluminum cross-linking agent. The
regulator is composed of
8% of acetic acid, 10% of methanol and 88% of water, and the pH of the
fracturing fluid is con-
trolled at 5-6.
11
CA 3055128 2019-09-12
LYPOOOOCADOO
The fracturing fluid is prepared in the same manner as in Embodiment 1.
The results obtained by testing the performance of the fracturing fluid show
that the fracturing fluid
prepared with clean water may withstand temperatures up to 150 C, while the
fracturing fluid
prepared with 150000 ppm mineralized brine may withstand temperatures up to
140 C. After con-
tinuous shearing for 120 min at 100s-1, the apparent viscosity is greater than
50 mPa.s; after the 30-
50 mesh proppant is added to the fully-suspended low-damage fracturing fluid
at a specific gravity
of sand of 20% for maintaining the temperature at 90 C for 1 h, the
sedimentation rate of proppant
is less than 5%.
Embodiment 5
The high temperature-resistance fully-suspended low-damage fracturing fluid is
prepared by the
low-damage thickening agent BCG-1XF-1, the multi-functional stabilizer BC-5-1,
a regulator and
the suspension synergist B-55S-1 in Embodiment I. The performance of the
fracturing fluid ob-
tained by different components in distribution ratios is as follows:
Embodiment 5-1: The content of each component is as follows in terms of 100
parts by weight: 0.3
parts of low-damage thickening agent, 0.1 part of multi-functional stabilizer,
0.1 part of regulator,
0.4 parts of suspension synergist, and 99.1 parts of water.
The residue content of the fracturing fluid prepared according to this formula
may not be measured,
and the highest temperature to be resisted is 100 C. After continuous
shearing for 90min at 100s-
1, the apparent viscosity is greater than 53.6 mPa.s; after the 30-50 mesh
proppant is added to the
fully-suspended low-damage fracturing fluid at a specific gravity of sand of
20% for maintaining
the temperature at 90 C for 1 h, the sedimentation rate of proppant is 4.5%.
Embodiment 5-2: The content of each component is as follows in terms of 100
parts by weight: 0.5
parts of low-damage thickening agent, 0.4 part of multi-functional stabilizer,
0.25 parts of regulator,
0.8 parts of suspension synergist, and 98.05 parts of water.
The residue content of the fracturing fluid prepared according to this formula
is 1.56mg/L, enabling
good cross-linking performance and viscoelastic performance, with a highest
temperature to be
resisted of 150 C. After continuous shearing for 120 min at 100s-1, the
apparent viscosity is greater
12
CA 3055128 2019-09-12
LYPOOOOCADOO
than 50 mPa.s; after the 30-50 mesh proppant is added to the fully-suspended
low-damage fractur-
ing fluid at a specific gravity of sand of 20% for maintaining the temperature
at 90 C for 1 h, the
sedimentation rate of proppant is 0.
Embodiment 5-3: The content of each component is as follows in terms of 100
parts by weight: 0.5
parts of low-damage thickening agent, 0.3 part of multi-functional stabilizer,
0.3 part of regulator,
0.7 parts of suspension synergist, and 98.2 parts of high salinity brine.
Among which, the simulated
composition of the brine is: 1.0% of CaCl2 + 2.0% of MgC12=6H20 + 0.5% of
K2SO4 + 6% of NaCI
+ 6% of KCI + 84.5% of clean water.
The residue content of the fracturing fluid prepared according to this formula
is 2.23mg/L, enabling
good cross-linking performance and viscoelastic performance, with a highest
temperature to be
resisted of 140 C. After continuous shearing for 120min at 100s-1, the
apparent viscosity is greater
than 56.6 mPa.s; after the 30-50 mesh proppant is added to the fully-suspended
low-damage frac-
turing fluid at a specific gravity of sand of 20% for maintaining the
temperature at 90 C for 1 h,
the sedimentation rate of proppant is 2.8%.
Embodiment 6
The high temperature-resistance fully-suspended low-damage fracturing fluid is
prepared by the
low-damage thickening agent BCG-1XF-1, the multi-functional stabilizer BC-5-2,
a regulator and
the suspension synergist B-55S-2 in Embodiment 2. The performance of the
fracturing fluid ob-
tained by different components in distribution ratios is as follows:
Embodiment 6-1: The content of each component is as follows in terms of 100
parts by weight: 0.3
parts of low-damage thickening agent, 0.2 part of multi-functional stabilizer,
0.2 parts of regulator,
0.4 parts of suspension synergist, and 98.9 parts of water.
The residue content of the fracturing fluid prepared according to this formula
may not be measured,
and the highest temperature to be resisted is 95 C. After continuous shearing
for 90min at 100s-I,
the apparent viscosity is greater than 57.3 mPa.s; after the 30-50 mesh
proppant is added to the
fully-suspended low-damage fracturing fluid at a specific gravity of sand of
20% for maintaining
the temperature at 90 C for 1 h, the sedimentation rate of proppant is 4.8%.
13
CA 3055128 2019-09-12
LYPOOOOCADOO
Embodiment 6-2: The content of each component is as follows in terms of 100
parts by weight: 0.5
parts of low-damage thickening agent, 0.4 part of multi-functional stabilizer,
0.3 parts of regulator,
0.8 parts of suspension synergist, and 98.0 parts of water.
The residue content of the fracturing fluid prepared according to this formula
is 2.06mg/L, enabling
good cross-linking performance and viscoelastic performance, with a highest
temperature to be
resisted of 140 C. After continuous shearing for 120 min at 100s', the
apparent viscosity is greater
than 53.8mPa.s; after the 30-50 mesh proppant is added to the fully-suspended
low-damage frac-
turing fluid at a specific gravity of sand of 20% for maintaining the
temperature at 90 C for 1 h,
the sedimentation rate of proppant is 1.6%.
Embodiment 6-3: The content of each component is as follows in terms of 100
parts by weight: 0.5
parts of low-damage thickening agent, 0.4 part of multi-functional stabilizer,
0.3 part of regulator,
0.7 part of suspension synergist, and 98.1 parts of high salinity brine. Among
which, the simulated
composition of the brine is: 1.0% of CaCl2 + 2.0% of gC12=6H20 + 0.5% of K2SO4
+ 6% of NaCl
+ 6% of KC1 + 84.5% of clean water.
The residue content of the fracturing fluid prepared according to this formula
is 2.32mg/L, enabling
good cross-linking performance and viscoelastic performance, with a highest
temperature to be
resisted of 135 C. After continuous shearing for 120min at 100s-1, the
apparent viscosity is greater
than 52.6 mPa.s; after the 30-50 mesh proppant is added to the fully-suspended
low-damage frac-
turing fluid at a specific gravity of sand of 20% for maintaining the
temperature at 90 C for 1 h,
the sedimentation rate of proppant is 3.6%.
Embodiment 7
The high temperature-resistance fully-suspended low-damage fracturing fluid is
prepared by the
low-damage thickening agent BCG-1XF-3, the multi-functional stabilizer BC-5-2,
a regulator and
the suspension synergist B-55S-3 in Embodiment 3. The performance of the
fracturing fluid ob-
tamed by different components in distribution ratios is as follows:
Embodiment 7-1: The content of each component is as follows in terms of 100
parts by weight: 0.4
parts of low-damage thickening agent, 0.3 part of multi-functional stabilizer,
0.3 parts of regulator,
0.5 parts of suspension synergist, and 98.5 parts of water.
14
CA 3055128 2019-09-12
LYPOOOOCADOO
The residue content of the fracturing fluid prepared according to this formula
is 1.86mg/L, and the
highest temperature to be resisted is 120 C. After continuous shearing for
120min at 100s-1, the
apparent viscosity is greater than 68.3 mPa.s; after the 30-50 mesh proppant
is added to the fully-
suspended low-damage fracturing fluid at a specific gravity of sand of 20% for
maintaining the
temperature at 90 C for 1 h, the sedimentation rate of proppant is 0.
Embodiment 7-2: The content of each component is as follows in terms of 100
parts by weight: 0.4
parts of low-damage thickening agent, 0.3 part of multi-functional stabilizer,
0.3 part of regulator,
0.5 parts of suspension synergist, and 98.5 parts of high salinity brine.
Among which, the simulated
composition of the brine is: 1.0% of CaCl2 + 2.0% of MgC12=6H20 + 0.5% of
K2SO4 + 6% of NaCl
+ 6% of KC1 + 84.5% of clean water.
The residue content of the fracturing fluid prepared according to this formula
is 1.63mg/L, enabling
good cross-linking performance and viscoelastic performance, with a highest
temperature to be
resisted of 110 C. After continuous shearing for 120 min at 100s-1, the
apparent viscosity is greater
than 58.1mPa.s; after the 30-50 mesh proppant is added to the fully-suspended
low-damage frac-
turing fluid at a specific gravity of sand of 20% for maintaining the
temperature at 90 C for 1 h,
the sedimentation rate of proppant is 2.3%.
Embodiment 7-3: The content of each component is as follows in terms of 100
parts by weight: 0.5
parts of low-damage thickening agent, 0.4 part of multi-functional stabilizer,
0.3 part of regulator,
0.8 parts of suspension synergist, and 98.0 parts of high salinity brine.
Among which, the simulated
composition of the brine is: 1.0% of CaCl2 + 2.0% of MgCl2 6H20 + 0.5% of
K2SO4 + 6% of NaCl
+ 6% of KCI + 84.5% of clean water.
The residue content of the fracturing fluid prepared according to this formula
is 2.35mg/L, enabling
good cross-linking performance and viscoelastic performance, with a highest
temperature to be
resisted of 140 C. After continuous shearing for 120min at 100s-1, the
apparent viscosity is greater
than 57.2 mPa.s; after the 30-50 mesh proppant is added to the fully-suspended
low-damage frac-
turing fluid at a specific gravity of sand of 20% for maintaining the
temperature at 90 C for 1 h,
the sedimentation rate of proppant is 3.5%.
Embodiment 8
CA 3055128 2019-09-12
LYPOOOOCADOO
The high temperature-resistance fully-suspended low-damage fracturing fluid is
prepared by the
low-damage thickening agent BCG-1XF-4, the multi-functional stabilizer BC-5-2,
a regulator and
the suspension synergist B-55S-4 in Embodiment 4. The performance of the
fracturing fluid ob-
tained by different components in distribution ratios is as follows:
Embodiment 8-1: The content of each component is as follows in terms of 100
parts by weight: 0.3
parts of low-damage thickening agent, 0.3 part of multi-functional stabilizer,
03 parts of regulator,
0.4 parts of suspension synergist, and 98.7 parts of water.
The residue content of the fracturing fluid prepared according to this formula
may not be measured,
and the highest temperature to be resisted is 100 C. After continuous shearing
for 90min at 100s-1,
the apparent viscosity is greater than 59.2 mPa.s; after the 30-50 mesh
proppant is added to the
fully-suspended low-damage fracturing fluid at a specific gravity of sand of
20% for maintaining
the temperature at 90 C for 1 h, the sedimentation rate of proppant is 2.1%.
Embodiment 8-2: The content of each component is as follows in terms of 100
parts by weight: 0.5
parts of low-damage thickening agent, 0.4 part of multi-functional stabilizer,
0.3 parts of regulator,
0.8 parts of suspension synergist, and 98.0 parts of water.
The residue content of the fracturing fluid prepared according to this formula
is 2.56mg/L, enabling
good cross-linking performance and viscoelastic performance, with a highest
temperature to be
resisted of 150 C. After continuous shearing for 120 min at 100s-', the
apparent viscosity is greater
than 70.8mPa.s; after the 30-50 mesh proppant is added to the fully-suspended
low-damage frac-
turing fluid at a specific gravity of sand of 20% for maintaining the
temperature at 90 C for 1 h,
the sedimentation rate of proppant is 0.
Embodiment 8-3: The content of each component is as follows in terms of 100
parts by weight: 0.5
parts of low-damage thickening agent, 0.4 part of multi-functional stabilizer,
0.3 part of regulator,
0.8 parts of suspension synergist, and 98.0 parts of high salinity brine.
Among which, the simulated
composition of the brine is: 1.0% of CaCl2 + 2.0% of MgC 6H20 + 0.5% of K2SO4
+ 6% of NaCl
+ 6% of KC1 + 84.5% of clean water.
The residue content of the fracturing fluid prepared according to this formula
is 2.68mg/L, enabling
good cross-linking performance and viscoelastic performance, with a highest
temperature to be
resisted of 140 C. After continuous shearing for 120min at 100s-i, the
apparent viscosity is greater
16
CA 3055128 2019-09-12
LYP0000CADOO
than 54.5 mPa.s; after the 30-50 mesh proppant is added to the fully-suspended
low-damage frac-
turing fluid at a specific gravity of sand of 20% for maintaining the
temperature at 90 C for 1 h,
the sedimentation rate of proppant is 3.0%.
Embodiment 9
The performances of four low-damage thickening agents (BCG-1XF-1, BCG-1XF-2,
BCG-1XF-
3, BCG-1XF-4) in Embodiments 1-4 are compared with conventional thickening
agents for tests,
and the test results are shown in Table 1. From the comparison of the basic
performance indexes in
Table 1, it can be seen that the thickening agents of BCG-1XF series may meet
the performance
requirements of high temperature-resistance fully-suspended low-damage
fracturing fluid. It can
also be seen from the comparison data that the thickening agent BCG-1XF
selected in the present
invention is excellent in salt resistance, cross-linking, viscoelasticity and
the like due to the intro-
duction of a unique monomer component during synthesis.
Remarks: the composition of the brine in the table is: 1.0% of CaCl2 + 2.0% of
MgC12=6H20 +0.5%
of K2SO4 + 6% of NaC1 + 6% of KC1 + 84.5% of clean water.
BCG-1: a cross-linkable high temperature-resistance multi-component copolymer
thickening agent
mainly composed of acrylic acid, acrylamide, cetyldimethyldiallyl chloride,
and 2-acrylamido-2-
methylpropanesulfonic acid.
BCG-JZ: a high temperature-resistance thickening agent for weighted cleaning
fracturing fluid
mainly composed of acrylic acid, bisacrylamide, octadecyldimethyldiallyl
ammonium chloride, 2-
acrylamido2-methylpropanesulfonic acid, and maleic acid.
BCG-1H: a thickening agent for supramolecular polymer fracturing fluid mainly
composed of
acrylic acid, acrylamide, fumaric acid and 2-acrylamido-2-
methylpropanesulfonic acid.
Conventional polyacrylamide polymer, mainly composed of acrylic acid, and
acrylamide.
Table 1 Comparison of performance of several kinds of thickening agents for
fracturing fluid
(0.5% dosage, under room temperature condition)
17
CA 3055128 2019-09-12
LYP0000CADOO
viscosity of
viscosity cross-linking, viscoelastic
insolubles/% base liquid
thickening speed/min performance
(4h)/mPa.s
agent
clean clean
clean water brine brine clean water brine
water water
substantially
hangable,
2 ¨ 12¨' 70¨' 60¨' hangable,
BCG-1XF-1 0.12 good
2.5 15 90 80 good
viscoelasticity
viscoelasticity
substantially
substantially
10 ¨ 70 ¨ 60 ¨ hangable, hangable,
BCG-1XF-2 0.11 2 ¨ 3
15 80 70 better general
viscoelasticity viscoelasticity
substantially
hangable,
13¨' 70-' 60¨' hangable,
BCG-1XF -3 0.10 2 ¨ 3 good
15 80 70 good
viscoelasticity
viscoelasticity
substantially
hangable,
2 l2'' 70' 60'' hangable,
BCG-1XF-4 0.13 good
2.5 15 90 80 good
viscoelasticity
viscoelasticity
unable to be
without cross-
1.5 30¨' 90¨' 30¨'
BCG-1 0.22 hanged, good
linking, poor
¨'2
40 100 40 viscoelasticity viscoelasticity
slightly-weak
weak cross-
1.5 10¨' 80¨' 60¨' cross-linking,
BCG-JZ 0.18 linking, good
¨ 2 low
15 100 80
viscoelasticity
viscoelasticity
18
CA 3055128 2019-09-12
LYPOOOOCADOO
without cross-
5 ¨ 60 ¨ 20 ¨ weak cross-
BC G-1H 0.10 > 60
linking, poor
10 80 30 linking
viscoelasticity
conventional
without cross- without cross-
5¨ 80'-. 20 ¨
polyacrylamide 0.5 > 40 linking, better
linking, poor
10 100 50
polymer
viscoelasticity viscoelasticity
Embodiment 10
The multi-functional stabilizer BC-5 series of the present invention may
eliminate the effects of
high salinity, complex ions and dissolved oxygen on the fracturing fluid to a
certain extent, ensuring
that for the fracturing fluid, cross-linking bonds, covalent bonds, etc. are
not damaged under normal
temperature or even high temperature conditions while improving the stability
performance of the
fracturing fluid. Using the base liquid of fracturing fluid with the simulated
brine formulation in
Embodiment 1 of 0.5% of low-damage thickening agent + 0.3% of stabilizer +
0.2% of regulator,
in which the stabilizers are the multi-functional stabilizer in Embodiment 1,
the multi-functional
stabilizer in Embodiment 2, the metal ion stabilizer 1, the metal ion
stabilizer 2, the high tempera-
ture stabilizer, and the viscosity retention agent respectively, and adding
0.6% of the suspension
synergist in Embodiment 1 for rheological testing, may obtain the performance
of swelling and
temperature-resistance of several groups of liquids, as shown in Table 2. It
can be seen that the
multi-functional stabilizers 1 and 2 provided by the present invention have
unique advantages in
various performance indexes, and if they are replaced with other similar
stabilizers, the perfor-
mance of the fracturing fluid may not achieve the desired results.
Table 2 Comparison of performance of several kinds of stabilizers
swelling of thickening agent
fracturing
reagent main component fluid
time of disso- viscosity
lution/min of base
performance
19
CA 3055128 2019-09-12
LYPOOOOCADOO
liquid of
tempera-
ture-re-
(4h)/mPa.s
sistance
(140 C,
100s-1,
120min)
multi-func-
tional stabi- sorbitol, hydroxyethylethylenedia-
12.5 69
lizer (BC-
minetriacetic acid, sodium sulfite 56.8mPa.s
5-1)
multi-
functional sorbitol, sodium iminodisuccinate,
13.5 68
stabilizer sodium hyposulfite 53.3mPa.s
(BC-5-2)
metal ion diethylenetriaminepentaacetic acid,
16 57
<20mPa.s
stabilizer 1 sodium gluconate
metal ion
disodium edetate 22 54
<20mPa.s
stabilizer 2
high
sodium thiosulfate, ammonium
temperature >40 45
<30mPa.s
thiosulfate
stabilizer
viscosity
retention thiourea or sodium sulfite >40 48
<30mPa.s
agent
Embodiment 11
The suspension synergists (B-55S-1, B-55S-2, B-55S-3, B-55S-4) provided by the
present
invention are compounded with several components having special functions, and
has outstanding
CA 3055128 2019-09-12
LYPOOOOCADOO
performance in several aspects such as fracturing fluid cross-linking,
viscoelastic structure
enhancement and high temperature-resistance and suspension proppant
performance. The
fracturing fluid is prepared using clean water and the relevant tests of
performance are carried out.
The results are shown in Table 3. It can be seen that in the fracturing fluid
of the present invention,
after the thickening agent is determined, other similar reagents are
completely incapable of
replacing the effects produced by the suspension synergist. This is enough to
illustrate the effect of
the suspension synergist of the present invention and the thickening agent,
and more to reflect its
originality. Remarks: highest temperature to be resisted refers to that the
apparent viscosity of the
fracturing fluid may be kept above 50mPa.s after being sheared at 100s-1 for
2h. The sedimentation
rate of proppant refers to that the fracturing fluid (30 to 50 mesh proppant,
with specific weight of
sand of 20%) mixed the proppant is poured into a measuring cylinder, then the
sedimentation rate
of the proppant is calculated after the temperature is kept at 90 C for 1
hour (calculated based on
the volume of the clear liquid deposited on the liquid surface).
Table 3 Comparison of the effects of the suspension synergist of the present
invention and other
similar reagents on the
highest
sedimentation
cross-linking temperature
reagent main component rate
of
state to be
proppant
resisted
Sodium dodecyl diphenyl ether
suspension hangable,
disulfonate, coconut oil fatty acid
synergist (B- strong 150 C 0
diethanolamide, organic zirconium
55S-1) viscoelasticity
delayed cross-linking agent
sodium dodecyl dinaphthalene
suspension hangable,
sulfonate, coconut oil fatty acid
synergist (B- good 140 C 1.6
diethanolamide, organic aluminum
55S-2) viscoelasticity
cross-linking agent
21
CA 3055128 2019-09-12
LYP0000CADOO
dodecylbenzenesulfonic acid
suspension hangable,
isopropanolamine salt, 8-10 alkyl
synergist (B- strong 150 C 0
glycoside APG, organic zirconium
55S-3) viscoelasticity
delayed cross-linking agent
dodecylbenzenesulfonic acid
suspension hangable,
isopropanolamine salt, 8-10 alkyl
synergist (B- strong 150 C 0
glycoside APG, organic aluminum
55S-4) viscoelasticity
cross-linking agent
without cross-
adjuvant SDBS linking, good 110 C 28.3
viscoelasticity
without cross-
viscosity
SDBS, sodium cocosulfonate linking, good 120 C 25.6
synergist
viscoelasticity
synthetic
weak cross-
surfactant
alkyl tertiary amine, esters linking, good 120 C 22.8
cross-linking
viscoelasticity
agent
substantially
aluminum
hangable,
cross-linking aluminum citrate, polyol 100 C 40.9
general
agent
viscoelasticity
substantially
zirconium
zirconium oxychloride, polyol, hangable,
cross-linking 110 C 45.3
citric acid general
agent 1
viscoelasticity
zirconium zirconium sulfate, polyol, sodium weak cross-
120 C 42.6
cross-linking gluconate linking,
22
CA 3055128 2019-09-12
LYPOOOOCADOO
agent 2 general
viscoelasticity
substantially
compounded
sodium cocosulfonate, aluminum hangable,
cross-linking 125 C
22.1
citrate, polyol better
agent 1
viscoelasticity
substantially
compounded
SDBS, zirconium cross-linking hangable,
cross-linking 130 C
19.8
agent 2 good
agent 2
viscoelasticity
Embodiment 12
The fracturing fluids in Embodiments 6-1, 7-1, 8-3, and 5-2 are tested for
temperature and shear
resistance. Testing instrument: Huck RS6000 rheometer, rotating cylinder test,
using rotor PZ38.
Test formulation, test conditions for fracturing fluid, and the results are
shown in Table 4.
Table 4 Test results of components and temperature and shear resistance of
typical embodiments
of the present invention
shear rate, 100s-1
apparent
Groups main component temperature/
time/min
viscosity/mPa.s
C
0.3 parts of BCG-1XF-2, 0.2
Embodiment parts of BC-5-1, 0.2 parts of
100 90 >57.3
6-1 regulator, 0.4 parts of B-55S-2,
98.9 parts of clean water
Embodiment 0.4 parts of BCG-1XF-3, 0.3
120 120 >68.3
7-1 parts of BC-5-2, 0.3 parts of
23
CA 3055128 2019-09-12
LYPOOOOCADOO
regulator, 0.5 parts of B-55S-3,
98.5 parts of clean water
0.5 parts of BCG-1XF-4, 0.4
Embodiment parts of BC-5-2, 0.3 parts of
140 120
>54.5
8-3 regulator, 0.5 parts of B-55S-4,
98.0 parts of brine
0.5 parts of BCG-1XF-1, 0.4
Embodiment parts of BC-5-1, 0.25 parts of
150 120
>72.8
5-2 regulator, 0.8 parts of B-55 S-1,
98.05 parts of clean water
Test results of temperature and shear resistance of several embodiments of
fracturing fluids are
shown in Figs. 3, 4, 5 and 6, respectively. First, the structure of the
fracturing fluid after early high
shearing (800s-1) is not destroyed, and the apparent viscosity recovers
quickly, and finally the test
of shear is completed for 120 minutes; second, the water-based fracturing
fluid and the brine-based
fracturing fluid have a temperature-resistance of 150 C and 140 C
respectively under the premise
of 0.5% of the thickening agent, and after 100s1 shearing for a long time, the
apparent viscosity of
the water-based fracturing fluid is above 70mPa.s, and the apparent viscosity
of the brine-based
fracturing fluid is above 50, indicating that the apparent viscosity is not
dependent on time, and
there is a structural dynamic equilibrium in the . The results show that the
fully-suspended
fracturing fluid of the present invention has excellent salt tolerance,
temperature-resistance and
shear resistance, and a stable structure of the fracturing fluid, thereby
meeting the requirements in
long-term reservoir transformation for well construction within the
temperature range.
Embodiment 13
A base solution of the fracturing fluid is separately prepared according to
the formulations in
Embodiments 6-1, 7-1, 8-3 and 5-2, and 200m1 of the base solution is taken
while adding the
suspension synergist for stirring evenly and putting in the oven at 90 C for
30min; then, the liquid
is poured into a mixer while controlling the speed of the mixer until the
liquid may form a vortex
without producing foam, and 70g of 30 ¨ 50 mesh ceramsite (20% specific weight
of sand) is
24
CA 3055128 2019-09-12
LYPOOOOCADOO
weighed to slowly disperse the ceramsite; after the ceramsite is uniformly
dispersed in the liquid,
it is poured into a 100 ml measuring cylinder, and then the measuring cylinder
is placed in an oven
with a constant temperature of 90 C for 1 h to record the volume of the
supernatant from the
chromatogram; the suspension rate F of fracturing fluid is calculated as
follows:
F = (1-V/200) x100%,
the test records and calculation results are shown in Table 5.
Table 5 Test results of sand suspension for several groups of high temperature-
resistance fully-
suspended fracturing fluid
Groups Type deposited clean suspension
experimental
solution V. ml rate F, %
phenomena
water-based fully- 0 100 proppant
without
Embodiment
6-1 suspended fracturing
sedimentation
fluid
water-based fully- 0 100 proppant
almost
Embodiment
7-1 suspended fracturing without
fluid
sedimentation
brine-based fully- 6 97.0 proppant
without
Embodiment
8 suspended fracturing
sedimentation
-3
fluid
water-based fully- 0 100 proppant
without
Embodiment
suspended fracturing
sedimentation
5-2
fluid
Embodiment 14
During the fracturing transformation process, the damage of the fracturing
fluid to the formation is
mainly reflected in two aspects: damage on formation base and damage on
diversion capacity of
CA 3055128 2019-09-12
LYPOOOOCADOO
support fracture. The fracturing fluid provided by the present invention has
substantially no water-
insoluble matter (or of extremely low content) after gel breaking and
hydration, so it has inevitably
excellent characteristics of low damage.
Through the test of the content of the broken gel residue and the test of the
damage rate of diversion
capacity of the support fracture, the damage magnitude on the diversion
capacity of the support
fracture from the fracturing fluid may be directly reflected. The test of
damage on the permeability
of rock core base may further measure the damage magnitude of the fracturing
fluid to the
formation. According to SY/T5107-2005 Water-based Fracturing liquid
Performance Evaluation
Method, relevant experiments are carried out on the fracturing fluids in
Embodiments 6-1, 7-1, 8-
3 and 5-2, and the conventional guar gum fracturing fluid for comparison. The
results are shown
in Table 6. It can be seen that the residue content of the fracturing fluid
provided by the present
invention is almost zero, which has a low damage rate to the permeability of
rock core base and
diversion capacity of support fracture, and is significant as compared with
the conventional guar
gum fracturing fluid, reflecting its genuine characteristics of low damage.
Table 6 Test results of damage of several groups of fracturing fluid
damage rate to
damage rate to
diversion
residue content,
permeability of
fracturing fluid type capacity of
mg/L rock core base,
support fracture,
Vo
conventional guar gum fracturing
489.36 82.6 46.8
fluid
Embodiment
high 0 6.35 8.92
6-1
temperature-
resistance fully- Embodiment
1.86 8.82 10.65
suspended 7-1
26
CA 3055128 2019-09-12
LYPOOOOCADOO
fracturing fluid Embodiment
2.68 9.33 12.26
8-3
Embodiment
1.56 9.12 10.31
5-2
In summary, the high temperature-resistance fully-suspended low-damage
fracturing fluid of the
present invention is a super structural fluid formed by the physical cross-
linking and chemical
cross-linking of the acrylamide polymer and the suspension synergist, which
has the following
features: (1) salinity resistance, capable of being prepared by high salinity
brine with less than
150000 ppm; (2) high temperature-resistance, up to 150 C; (3) strong shear
recovery, high shear
having low damage to the fracturing fluid structure; (4) excellent sand-
carrying performance,
powerful spatial structure suspending proppant and less affected by
temperature; (5) low damage,
reducing damage to reservoir and significantly improving the transformation of
oil and gas
reservoirs.
Although the embodiments of the present invention have been disclosed as
above, they are not
limited to the applications listed in the specification and the embodiments.
It can be applied to a
wide variety of fields suitable for the present invention. Additional
modifications can be readily
implemented by those skilled in the art. The present invention is therefore
not limited to the specific
details and the details shown and described herein, without departing from the
scope of the
invention.
27
CA 3055128 2019-09-12
