CA3055128C - High temperature-resistance fully-suspended low-damage fracturing fluid and preparing method thereof - Google Patents

Abstract

A high temperature-resistance fully-suspended low-damage fracturing fluid is provided in the present invention, which 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 within a certain degree of salinity. The method for preparing a fracturing fluid includes: 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. The fracturing fluid of the present invention is a super-strong structural fluid formed by physical cross-linking and chemical cross-linking of acrylamide polymer and suspension synergist, and the temperature-resistance capability is up to 150°C; the sand- carrying performance is excellent, and the powerful space structure can fully suspend proppant and is less affected by temperature.

Description

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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, 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-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

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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-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.

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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.

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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-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.

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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 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.

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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.

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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 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%.

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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.

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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 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 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, 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) 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 viscoelasticity viscoelasticity 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 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 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, <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 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 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, 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 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 >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 >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 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 fluid water-based fully- 0 100 proppant without Embodiment suspended fracturing sedimentation 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 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 temperature-resistance fully- Embodiment 1.86 8.82 10.65 suspended 7-1 LYPOOOOCADOO
fracturing fluid Embodiment 2.68 9.33 12.26 Embodiment 1.56 9.12 10.31 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.

Claims (10)

WHAT IS CLAIMED IS:

1. A high temperature-resistant fully-suspended low-damage fracturing fluid, comprising 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 suspending agent, and a remaining component is clean water or brine;
wherein: the low-damage thickening agent is formed by a copolymer of a main-chain monomer A, a main-chain monomer B, a salt-tolerant monomer, and a 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 cross-linking monomer is one of N-vinylcaprolactam, N,N-methylenebisacrylamide, diacetone acrylamide, and N-methylol acrylamide.

2. The high temperature-resistant fully-suspended low-damage fracturing fluid according to claim 1, wherein the salt-tolerant monomer is N-allylimidazole, vinylphosphonic acid, or a mixture of both with equivalent weights.

3. The high temperature-resistant fully-suspended low-damage fracturing fluid according to claim 1, wherein 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 ethylenediaminetetraacetate, sorbitol, hydroxyethylethylenediaminetriacetic acid, or a mixture of two with equivalent amount, and has a content of 5% to 8% in weight percent; and the component B is one of methanol, ascorbic acid, and sodium sulfite, and has a content of 15% to 20% in volume percent.

4. The high temperature-resistant fully-suspended low-damage fracturing fluid according to claim 1, wherein the suspending agent consists of a thickening synergist, a cross-linking agent and water in a mass ratio of 3:1:1.

5. The high temperature-resistant fully-suspended low-damage fracturing fluid according to claim 4, wherein 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, and dodecyl dihydroxy ethyl betaine; the surfactant B is one of coconut oil fatty acid diethanolamide and alkyl glycoside Alkyl poly glycoside (APG);
and the alcohol solvent A is one of methanol, ethylene glycol, and glycerin.

6. The high temperature-resistant fully-suspended low-damage fracturing fluid according to claim 4, wherein the cross-linking agent is one of an organoaluminum crosslinking agent, an organic titanium delayed crosslinking agent, and an organozirconium delayed crosslinking agent.

7. The high temperature-resistant fully-suspended low-damage fracturing fluid according to claim 1, wherein 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.

8. The high temperature-resistant fully-suspended low-damage fracturing fluid according to claim 4, wherein when the cross-linking agent in the suspending agent 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 suspending agent is an organotitanium delayed cross-linking agent or an organic zirconium delayed cross-linking agent, the PH value is adjusted to 8 to 10 by using an alkaline regulator.

9. The high temperature-resistant fully-suspended low-damage fracturing fluid according to claim 1, wherein the salinity of the brine is 0 to 150,000 ppm, the content of Ga2+ in the brine is less than 3000 ppm, the content of Mg2+ is less than 15000 ppm. and the total content of Fe2+ and Fe3+ is less than 5 ppm.

10. A method for preparing a high temperature-resistant fully-suspended low-damage fracturing fluid according to claim 1, comprising:
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 suspending agent; 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.