Low-filtration guanidine gum fracturing fluid system and preparation method thereof

Abstract

The invention relates to the technical field of fracturing fluids, and provides a low-filtration guanidine gum fracturing fluid system and a preparation method thereof.The guanidine gum fracturing fluid system is prepared from, by weight, 0.3-0.4 part of guanidine gum, 0.13-0.25 part of a cross-linking agent, 0.015-0.025 part of a gel breaker, 0.22-0.32 part of a filtrate reducer, 0.14-0.24 part of a clay stabilizer and 100 parts of water; the filtrate reducer is prepared from the following components in parts by weight: 20 to 30 parts of hydroxypropyl starch ether, 14 to 19 parts of hydroxypropyl methyl cellulose, 3 to 10 parts of sodium dioctyl sulfosuccinate, 10 to 16 parts of multiwalled carbon nanotubes, 5 to 10 parts of sodium citrate, 2 to 3 parts of degradation agent and 80 parts of water. According to the technical scheme, the problem of poor filtrate loss reduction performance of a guanidine gum fracturing fluid system in the prior art is solved.

Description

Technical Field

[0001] The invention relates to the technical field of fracturing fluids, and in particular to a low-filtration-loss guar fracturing fluid system and a preparation method thereof. Background Art

[0002] Guar fracturing fluid is a fracturing fluid system with guar as the main thickener. Guar is a natural high molecular polymer extracted from seeds of plants such as guar beans. In fracturing operations, it can significantly increase the viscosity of the liquid, so that it can carry proppants such as quartz sand and ceramsite into the cracks of the formation. Guar fracturing fluid is widely used in the field of oil and natural gas extraction. In the development of low-permeability oil and gas reservoirs, due to the low permeability of the formation, the flow resistance of oil and gas is large. By using guar fracturing fluid for hydraulic fracturing, artificial cracks can be created in underground rocks to improve the seepage conditions of oil and gas underground. For example, in shale gas extraction, guar fracturing fluid can help transport a large amount of proppants into the tiny cracks of shale, propping up these cracks and keeping them open, so that shale gas can be smoothly extracted from the formation.

[0003] However, the guar gum fracturing fluid currently used has a large filtration loss, which is easy to reduce the effective volume in the crack during use, affecting the proppant delivery distance and the crack expansion effect. Excessive filtration loss may cause excessive scouring of the formation, or even block the cracks and proppant filling layer, causing irreversible damage to the formation. Therefore, the development of a guar gum fracturing fluid system with low filtration loss plays an important role in improving fracturing efficiency, reducing damage to the formation, and improving construction safety. Summary of the invention

[0004] The invention provides a low-fluid loss guar fracturing fluid system and a preparation method thereof, which solves the problem of poor fluid loss reduction performance of the guar fracturing fluid system in the related art.

[0005] The technical solution of the present invention is as follows: The present invention provides a low fluid loss guar fracturing fluid system, comprising the following components in parts by weight: 0.3-0.4 parts of guar gum, 0.13-0.25 parts of cross-linking agent, 0.015-0.025 parts of breaker, 0.22-0.32 parts of fluid loss reducer, 0.14-0.24 parts of clay stabilizer, 100 parts of water; The fluid loss reducer comprises the following components in parts by weight: 20-30 parts of hydroxypropyl starch ether, 14-19 parts of hydroxypropyl methylcellulose, 3-10 parts of sodium salt of dioctyl sulfosuccinate, 10-16 parts of multi-walled carbon nanotubes, 5-10 parts of sodium citrate, 2-3 parts of degradation agent, and 80 parts of water.

[0006] As a further technical solution, the weight ratio of the hydroxypropyl methylcellulose to the sodium salt of dioctyl sulfonate succinate is 2-3:1.

[0007] When the weight ratio of hydroxypropyl methylcellulose to sodium dioctyl sulfonate succinate is 2-3:1, the fluid loss reduction performance of the guar gum fracturing fluid system can be further improved.

[0008] As a further technical solution, the multi-walled carbon nanotubes are modified multi-walled carbon nanotubes, the raw materials of the modified multi-walled carbon nanotubes include multi-walled carbon nanotubes and a modifier, and the modifier includes nano titanium dioxide and acetylbenzamide.

[0009] In the present invention, after the multi-walled carbon nanotubes are modified by using nano-titanium dioxide and acetylbenzamide as modifiers, their compatibility with other components in the fluid loss reducer can be significantly improved, the adsorption effect can be fully exerted, the tiny gaps in the rock pores can be more evenly filled, the fluid loss of the fracturing fluid can be more effectively reduced, and the fluid loss reduction performance of the entire system can be further improved.

[0010] As a further technical solution, the method for preparing the modified multi-walled carbon nanotubes comprises the following steps: A1, dispersing the multi-walled carbon nanotubes and the nano-titanium dioxide in a polyethylene glycol solution, drying, calcining, and crushing to obtain a pretreated product; A2, dispersing the acetylbenzamide in anhydrous ethanol, adding the pretreated material, dispersing evenly, and drying to obtain modified multi-walled carbon nanotubes; The weight ratio of the multi-walled carbon nanotubes to the polyethylene glycol solution is 1:1.3.

[0011] As a further technical solution, the mass fraction of the polyethylene glycol solution is 15% to 20%; during the calcination, the temperature is 500 to 600° C. and the time is 1 to 2 hours.

[0012] As a further technical solution, the multi-walled carbon nanotubes have a diameter of 30-60 nm and a length of 5-20 μm.

[0013] As a further technical solution, the particle size of the nano titanium dioxide is 10-80 nm.

[0014] As a further technical solution, in the modified multi-walled carbon nanotubes, the weight ratio of the multi-walled carbon nanotubes to the modifier is 40:2-5.

[0015] When the weight ratio of multi-walled carbon nanotubes to modifiers in the modified multi-walled carbon nanotubes is 40:2-5, the fluid loss reduction performance of the guar gum fracturing fluid system can be further improved.

[0016] As a further technical solution, the weight ratio of the nano titanium dioxide to acetylbenzamide is 3:2.

[0017] As a further technical solution, the guar gum is one or both of hydroxypropyl guar gum and carboxymethyl guar gum; the cross-linking agent is one or both of an organic boron cross-linking agent and a borate.

[0018] As a further technical solution, the gel breaker is one or more of sodium sulfite, potassium persulfate, and sodium persulfate; the clay stabilizer is one or more of potassium chloride, ammonium chloride, and sodium chloride.

[0019] As a further technical solution, the degradation agent is one or both of ammonium persulfate and sodium persulfate.

[0020] The present invention also proposes a method for preparing the low fluid loss guar gum fracturing fluid system, comprising the following steps: S1, uniformly mixing the components of the fluid loss reducer in parts by weight to obtain the fluid loss reducer; S2, mixing the guar gum, fluid loss reducer, clay stabilizer and water uniformly to obtain a base liquid; S3, adding the cross-linking agent and the breaker into the base fluid, stirring until a gel is formed, and obtaining the guar gum fracturing fluid system.

[0021] The working principle and beneficial effects of the present invention are: In the present invention, the guar gum fracturing fluid system can effectively reduce the filtration loss through the reasonable combination of various components, while taking into account the gel breaking and return performance of the fracturing fluid, which helps to improve the efficiency of the fracturing operation, reduce the repeated fracturing and other operations caused by the filtration loss problem, thereby reducing the mining cost to a certain extent and improving the economy of oil and gas production. Hydroxypropyl methylcellulose and sodium salt of dioctyl sulfonated succinate are added to the filtration loss reducer, and the hydroxypropyl methylcellulose and sodium salt of dioctyl sulfonated succinate have a synergistic effect. Through the composite use of hydroxypropyl methylcellulose and sodium salt of dioctyl sulfonated succinate, the prepared filtration loss reducer can have good adsorption performance, and at the same time, the guar gum fracturing fluid can be better spread on the rock surface, reducing the filtration loss caused by the local pressure difference, thereby improving the filtration loss reduction performance of the guar gum fracturing fluid system. DETAILED DESCRIPTION

[0022] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0023] In the following embodiments and comparative examples, guar gum is hydroxypropyl guar gum, model S24731; the cross-linking agent is an organic boron cross-linking agent, model PJL-2; the breaker is potassium persulfate; the clay stabilizer is potassium chloride; the model of hydroxypropyl starch ether is Avibe 301; the viscosity of hydroxypropyl methylcellulose is 100000 mPa·s; the diameter of the multi-walled carbon nanotube is 50 nm and the length is 10 μm; the particle size of nano-titanium dioxide is 20 nm; the degradation agent is ammonium persulfate; in the polyethylene glycol solution, the weight average molecular weight of polyethylene glycol is 4000.

[0024] Example 1 A low fluid loss guar fracturing fluid system comprises the following components in parts by weight: 0.3 parts of hydroxypropyl guar gum, 0.13 parts of organic boron crosslinking agent PJL-2, 0.015 parts of potassium persulfate, 0.22 parts of fluid loss reducer, 0.14 parts of potassium chloride, and 100 parts of water; The fluid loss reducer comprises the following components in parts by weight: 20 parts of hydroxypropyl starch ether, 14 parts of hydroxypropyl methylcellulose, 3 parts of sodium dioctyl sulfosuccinate, 10 parts of multi-walled carbon nanotubes, 5 parts of sodium citrate, 2 parts of ammonium persulfate, and 80 parts of water; The preparation method of the guar gum fracturing fluid system comprises the following steps: S1. Evenly mix the components of the fluid loss reducer by weight to obtain the fluid loss reducer; S2, mixing hydroxypropyl guar gum, fluid loss reducer, potassium chloride and water uniformly to obtain a base liquid; S3. Add organic boron crosslinking agent PJL-2 and potassium persulfate to the base fluid, and stir until a gel is formed to obtain a guar gel fracturing fluid system.

[0025] Example 2 A low fluid loss guar fracturing fluid system comprises the following components in parts by weight: 0.35 parts of hydroxypropyl guar gum, 0.2 parts of organic boron crosslinking agent PJL-2, 0.02 parts of potassium persulfate, 0.28 parts of fluid loss reducer, 0.18 parts of potassium chloride, and 100 parts of water; The fluid loss reducer comprises the following components in parts by weight: 25 parts of hydroxypropyl starch ether, 15 parts of hydroxypropyl methylcellulose, 9 parts of sodium dioctyl sulfosuccinate, 14 parts of multi-walled carbon nanotubes, 8 parts of sodium citrate, 2.5 parts of ammonium persulfate, and 80 parts of water; The preparation method of the guar gum fracturing fluid system comprises the following steps: S1. Evenly mix the components of the fluid loss reducer by weight to obtain the fluid loss reducer; S2, mixing hydroxypropyl guar gum, fluid loss reducer, potassium chloride and water uniformly to obtain a base liquid; S3. Add organic boron crosslinking agent PJL-2 and potassium persulfate to the base fluid, and stir until a gel is formed to obtain a guar gel fracturing fluid system.

[0026] Example 3 A low fluid loss guar fracturing fluid system comprises the following components in parts by weight: 0.4 parts of hydroxypropyl guar gum, 0.25 parts of organic boron crosslinking agent PJL-2, 0.025 parts of potassium persulfate, 0.32 parts of fluid loss reducer, 0.24 parts of potassium chloride, and 100 parts of water; The fluid loss reducer comprises the following components in parts by weight: 30 parts of hydroxypropyl starch ether, 19 parts of hydroxypropyl methylcellulose, 10 parts of dioctyl sodium sulfosuccinate, 16 parts of multi-walled carbon nanotubes, 10 parts of sodium citrate, 3 parts of ammonium persulfate, and 80 parts of water; The preparation method of the guar gum fracturing fluid system comprises the following steps: S1. Evenly mix the components of the fluid loss reducer by weight to obtain the fluid loss reducer; S2, mixing hydroxypropyl guar gum, fluid loss reducer, potassium chloride and water uniformly to obtain a base liquid; S3. Add organic boron crosslinking agent PJL-2 and potassium persulfate to the base fluid, and stir until a gel is formed to obtain a guar gel fracturing fluid system.

[0027] Example 4 The only difference between this embodiment and embodiment 2 is that in this embodiment, 18.5 parts of hydroxypropyl methylcellulose and 5.5 parts of sodium salt of dioctyl sulfonate succinate are added to the fluid loss reducer.

[0028] Example 5 The only difference between this embodiment and embodiment 2 is that in this embodiment, 16 parts of hydroxypropyl methylcellulose and 8 parts of sodium salt of dioctyl sulfonate succinate are added to the fluid loss reducer.

[0029] Example 6 The only difference between this embodiment and embodiment 2 is that in this embodiment, 18 parts of hydroxypropyl methylcellulose and 6 parts of sodium salt of dioctyl sulfonate succinate are added to the fluid loss reducer.

[0030] Example 7 The only difference between this embodiment and embodiment 6 is that in this embodiment, the multi-walled carbon nanotubes in the fluid loss reducer are modified multi-walled carbon nanotubes, and the preparation method thereof comprises the following steps: dispersing 40 parts of multi-walled carbon nanotubes and 1 part of nano-titanium dioxide in 52 parts of 18% by mass polyethylene glycol solution, drying, calcining at 550° C. for 1.5 h, and crushing to obtain modified multi-walled carbon nanotubes.

[0031] Example 8 The only difference between this embodiment and embodiment 6 is that in this embodiment, the multi-walled carbon nanotubes in the fluid loss reducer are modified multi-walled carbon nanotubes, and the preparation method thereof comprises the following steps: dispersing 1 part of acetylbenzamide in 45 parts of anhydrous ethanol, adding 40 parts of multi-walled carbon nanotubes, dispersing evenly, and drying to obtain modified multi-walled carbon nanotubes.

[0032] Example 9 The difference between this embodiment and embodiment 6 is that, in this embodiment, the multi-walled carbon nanotubes in the fluid loss agent are modified multi-walled carbon nanotubes, and the preparation method thereof comprises the following steps: A1, dispersing 40 parts of multi-walled carbon nanotubes and 0.6 parts of nano-titanium dioxide in 52 parts of 18% by mass polyethylene glycol solution, drying, calcining at 550° C. for 1.5 h, and crushing to obtain a pretreated product; A2. After dispersing 0.4 parts of acetylbenzamide in 45 parts of anhydrous ethanol, add the above-mentioned pretreated material, disperse evenly, and dry to obtain modified multi-walled carbon nanotubes.

[0033] Example 10 The only difference between this embodiment and embodiment 9 is that in this embodiment, during the preparation of the modified multi-walled carbon nanotubes, 3.6 parts of nano-titanium dioxide and 2.4 parts of acetylbenzamide were added.

[0034] Embodiment 11 The only difference between this embodiment and embodiment 9 is that in this embodiment, during the preparation of the modified multi-walled carbon nanotubes, 1.2 parts of nano-titanium dioxide and 0.8 parts of acetylbenzamide were added.

[0035] Example 12 The only difference between this embodiment and embodiment 9 is that in this embodiment, during the preparation of the modified multi-walled carbon nanotubes, 3 parts of nano-titanium dioxide and 2 parts of acetylbenzamide are added.

[0036] Comparative Example 1 The difference between this comparative example and Example 1 is that in this comparative example, 17 parts of sodium salt of dioctyl sulfonate succinate is added to the fluid loss reducer, and no hydroxypropyl methylcellulose is added.

[0037] Comparative Example 2 The difference between this comparative example and Example 1 is that in this comparative example, 17 parts of hydroxypropyl methylcellulose are added to the fluid loss reducer, and no sodium salt of dioctyl sulfonate succinate is added.

[0038] Comparative Example 3 The difference between this comparative example and Example 1 is that in this comparative example, hydroxypropyl methylcellulose and sodium dioctyl sulfonate succinate are not added to the fluid loss reducer.

[0039] The guar gum fracturing fluid systems prepared in Examples 1 to 12 and Comparative Examples 1 to 3 were tested for initial filtration loss and filtration coefficient according to the test method in SY / T 5107-2016 "Method for evaluating performance of water-based fracturing fluids", wherein the filtration coefficient is a filtration coefficient not controlled by viscosity. The test results are shown in Table 1 below.

[0040] Table 1 Performance test data of guar gum fracturing fluid system

[0041] Compared with Comparative Examples 1 to 3, the initial filtration loss and the filtration coefficient of Example 1 are significantly reduced, indicating that when hydroxypropyl methylcellulose and sodium dioctyl sulfonate succinate are added to the filtration reducer, dihydroxypropyl methylcellulose and sodium dioctyl sulfonate succinate have a synergistic effect, and the filtration loss reduction performance of the guar gum fracturing fluid system can be improved by the compound use of hydroxypropyl methylcellulose and sodium dioctyl sulfonate succinate.

[0042] Compared with Examples 2 and 4, the initial filtration loss and the filtration coefficient of Examples 5-6 are reduced, indicating that when the weight ratio of hydroxypropyl methylcellulose to sodium dioctyl sulfonate succinate is 2-3:1, the filtration loss reduction performance of the guar gum fracturing fluid system can be further improved.

[0043] Compared with Examples 6 to 8, the initial filtration loss and the filtration coefficient of Examples 9 to 12 are reduced, indicating that the filtration loss reduction performance of the guar gum fracturing fluid system can be further improved by modifying the multi-walled carbon nanotubes with nano-titanium dioxide and acetylbenzamide.

[0044] Compared with Examples 9-10, the initial filtration loss and the filtration coefficient of Examples 11-12 are reduced, indicating that when the weight ratio of multi-walled carbon nanotubes to the modifier is 40:2-5, the filtration loss reduction performance of the guar gum fracturing fluid system can be further improved.

[0045] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A low fluid loss guar fracturing fluid system, characterized in that: The composition comprises the following components in parts by weight: 0.3-0.4 parts of guar gum, 0.13-0.25 parts of cross-linking agent, 0.015-0.025 parts of breaker, 0.22-0.32 parts of fluid loss reducer, 0.14-0.24 parts of clay stabilizer, 100 parts of water; The fluid loss reducer comprises the following components in parts by weight: 20-30 parts of hydroxypropyl starch ether, 14-19 parts of hydroxypropyl methylcellulose, 3-10 parts of sodium salt of dioctyl sulfosuccinate, 10-16 parts of multi-walled carbon nanotubes, 5-10 parts of sodium citrate, 2-3 parts of degradation agent, and 80 parts of water.

2. A low fluid loss guar fracturing fluid system according to claim 1, characterized in that: The weight ratio of the hydroxypropyl methylcellulose to the sodium salt of dioctyl sulfosuccinate is 2-3:

1.

3. A low fluid loss guar fracturing fluid system according to claim 1, characterized in that: The multi-walled carbon nanotubes are modified multi-walled carbon nanotubes. The raw materials of the modified multi-walled carbon nanotubes include multi-walled carbon nanotubes and a modifier. The modifier includes nano titanium dioxide and acetylbenzamide.

4. A low fluid loss guar fracturing fluid system according to claim 3, characterized in that: The preparation method of the modified multi-walled carbon nanotubes comprises the following steps: A1, dispersing the multi-walled carbon nanotubes and the nano-titanium dioxide in a polyethylene glycol solution, drying, calcining, and crushing to obtain a pretreated product; A2, dispersing the acetylbenzamide in anhydrous ethanol, adding the pretreated material, dispersing evenly, and drying to obtain modified multi-walled carbon nanotubes; The weight ratio of the multi-walled carbon nanotubes to the polyethylene glycol solution is 1:1.

3.

5. A low fluid loss guar fracturing fluid system according to claim 3, characterized in that: In the modified multi-walled carbon nanotubes, the weight ratio of the multi-walled carbon nanotubes to the modifier is 40:2-5.

6. A low fluid loss guar fracturing fluid system according to claim 3, characterized in that: The weight ratio of the nano titanium dioxide to acetylbenzamide is 3:

2.

7. The low fluid loss guar fracturing fluid system according to claim 1, characterized in that: The guar gum is one or both of hydroxypropyl guar gum and carboxymethyl guar gum; the cross-linking agent is one or both of organic boron cross-linking agent and borate.

8. The low fluid loss guar fracturing fluid system according to claim 1, characterized in that: The debonding agent is one or more of sodium sulfite, potassium persulfate, and sodium persulfate; the clay stabilizer is one or more of potassium chloride, ammonium chloride, and sodium chloride.

9. The low fluid loss guar fracturing fluid system according to claim 1, characterized in that: The degradation agent is one or both of ammonium persulfate and sodium persulfate.

10. The method for preparing a low fluid loss guar gum fracturing fluid system according to any one of claims 1 to 9, characterized in that: The following steps are involved: S1, after mixing the components of the fluid loss reducer in parts by weight uniformly, obtaining the fluid loss reducer; S2, mixing the guar gum, fluid loss reducer, clay stabilizer and water uniformly to obtain a base liquid; S3, adding the cross-linking agent and the breaker into the base fluid, stirring until a gel is formed, and obtaining the guar gum fracturing fluid system.

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