Self-heating fracturing fluid as well as preparation method and application thereof

Abstract

The invention discloses a self-heat-generation fracturing fluid and a preparation method and application thereof.The self-heat-generation fracturing fluid comprises a base fluid, a cross-linking agent and an instant heating agent, the instant heating agent comprises alkali and hydrochloric acid, the base fluid comprises a thickening agent, a sterilizing agent, a cleanup additive, a clay stabilizer, a conditioning agent and the balance water, and the thickening agent adopts guanidine gum; comprising 0.2%-0.5% of a thickening agent, 0.1%-0.15% of a sterilizing agent, 0.5%-0.55% of a cleanup additive, 0.5%-0.55% of a clay stabilizer, 0.3%-0.35% of a conditioning agent, 0.4%-0.6% of a cross-linking agent, 5%-10% of alkali, 4.6%-9.1% of hydrochloric acid and the balance of water. Compared with a traditional sodium nitrite / ammonium chloride system, an acid-base neutralization system instant heating agent is adopted, the heat generation speed is higher, the heat generation efficiency is improved, and the production cost is reduced; the peak temperature is high, no side reaction gas is generated, and the risk of cold damage of fracturing fluid to a reservoir can be effectively reduced; meanwhile, guanidine gum is selected as a thickening agent, so that the sand carrying effect is better.

Description

Technical Field

[0001] This invention belongs to the field of petroleum fracturing technology, specifically relating to a self-heating fracturing fluid, its preparation method, and its application. Background Technology

[0002] Fracturing fluid is a heterogeneous and unstable chemical system formed by a variety of additives in a certain proportion. It is a working fluid used to fracture oil and gas reservoirs. Its main function is to transfer the high pressure generated by the surface equipment to the formation, causing the formation to fracture and transport proppant along the fracture.

[0003] During fracturing, when the wax precipitation point of crude oil is below 30℃, the crude oil encounters the cold fracturing fluid, causing cold damage to the reservoir. Paraffin wax will precipitate in the pores of the rock on the fracture wall, resulting in a decrease in the proportion of large pores after fracturing, a slight increase in crude oil viscosity, and poor flow performance. Therefore, it is necessary to avoid cold damage and ensure the temperature of the reservoir during fracturing. In the early stage, the self-generating heat fracturing technology of ammonium salt and nitrite heat generation system was explored and tested. With the goal of "heat generation and temperature increase, gas generation and pressurization", the concentration of various additives such as heat generation agent, acid-resistant thickener, and catalyst in fracturing fluid was optimized to form a self-generating heat-enhancing fracturing fluid system formula. Field tests showed a certain production increase effect. However, this system is prone to gas generation during the heat generation process, and there is also a side reaction of gas decomposition into toxic substances. In addition, the reaction rate of this system is relatively slow, and the temperature change is slow after the fracturing fluid reaches the formation at room temperature. There is still room for further improvement in single-well production. Summary of the Invention

[0004] The purpose of this invention is to provide a self-generating thermal fracturing fluid, its preparation method, and its application, in order to solve the problem of excessive gas pressure generated by existing self-generating thermal fracturing fluids, and the problem of gas decomposition into toxic byproducts.

[0005] To solve the above problems, the present invention adopts the following technical solution:

[0006] A self-generating thermal fracturing fluid, comprising the following components by volume percentage:

[0007] The mixture comprises 0.2%-0.5% thickener, 0.1%-0.15% bactericide, 0.5%-0.55% drainage aid, 0.5%-0.55% clay stabilizer, 0.3%-0.35% regulator, 0.4%-0.6% crosslinking agent, 5%-10% alkali, 4.6%-9.1% hydrochloric acid, and the balance being water; the thickener is guar gum.

[0008] Furthermore, the guar gum used is CJ2-6 hydroxypropyl guar gum.

[0009] Furthermore, the bactericide used is CJSJ-3 bactericide.

[0010] Furthermore, the discharge aid is CF-5D discharge aid.

[0011] Furthermore, the clay stabilizer used is COP-3 clay stabilizer.

[0012] Furthermore, the regulator is TJ-1 regulator.

[0013] Furthermore, the crosslinking agent is organoboron and ammonium persulfate.

[0014] Furthermore, the alkali is one or more of sodium hydroxide and potassium hydroxide, and the hydrochloric acid concentration is 30-36%.

[0015] A method for preparing a self-generating thermal fracturing fluid includes the following steps:

[0016] According to the determined dosage, guar gum, bactericide, drainage aid, clay stabilizer and regulator are added to a certain amount of water in sequence and stirred evenly to prepare guar gum base solution;

[0017] The guar gum base solution and the proppant are mixed to prepare a sand-carrying base solution;

[0018] Adding alkali to the sand-carrying liquid and then adding hydrochloric acid yields a self-heating sand-carrying liquid.

[0019] A self-heating fracturing fluid is prepared by adding a crosslinking agent to a self-heating sand-carrying fluid.

[0020] Self-generating thermal fracturing fluid is used in oil and gas extraction.

[0021] Compared with the prior art, the present invention has the following beneficial technical effects:

[0022] This invention provides a self-generating thermal fracturing fluid, comprising a base fluid, a crosslinking agent, an alkali, and hydrochloric acid. By volume percentage, it includes 0.2%-0.5% thickener, 0.1%-0.15% bactericide, 0.5%-0.55% flow aid, 0.5%-0.55% clay stabilizer, 0.3%-0.35% regulator, 0.4%-0.6% crosslinking agent, 5%-10% alkali, 4.6%-9.1% hydrochloric acid, and the balance being water. The thickener is guar gum. Compared to the traditional sodium nitrite / ammonium chloride self-generating thermal system, this invention uses an acid-base neutralization self-generating thermal system, resulting in faster heat generation, higher peak temperature, and no side reaction gases. This effectively reduces the cold damage to the reservoir caused by the fracturing fluid and decreases the generation of gaseous side reaction products. Furthermore, the use of guar gum as a thickener improves proppant carrying capacity.

[0023] The present invention discloses a method for self-heating fracturing fluid, which involves a preparation process of base fluid-alkali-acid-crosslinking agent, and the compatibility test shows that the heat-generating agent has good compatibility with guar gum fracturing fluid.

[0024] Preferably, to address the issue of viscosity decrease after mixing guar gum fracturing fluid with a quick-heating agent, a crosslinking agent is added to the self-heating sand-carrying fluid. Attached Figure Description

[0025] Figure 1 This is a flowchart illustrating the preparation method of autogenous thermal fracturing fluid in an embodiment of the present invention.

[0026] Figure 2 This is a flowchart of the secondary hybrid autogenous thermal fracturing construction process. Detailed Implementation

[0027] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0028] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0029] This invention provides a self-generating thermal fracturing fluid, such as... Figure 1 As shown, the mixture includes a crosslinking agent, a quick-heating agent, and a base liquid. The quick-heating agent is made of alkali and hydrochloric acid. The base liquid includes a thickener, a bactericide, a drainage aid, a clay stabilizer, a regulator, and the balance being water. The thickener is guar gum, which, by volume percentage, includes 0.2%-0.5% guar gum, 0.1%-0.15% bactericide, 0.5%-0.55% drainage aid, 0.5%-0.55% clay stabilizer, 0.3%-0.35% regulator, 0.4%-0.6% crosslinking agent, 5%-10% alkali, 4.6%-9.1% hydrochloric acid, and the balance being water.

[0030] The guar gum used is CJ2-6 hydroxypropyl guar gum.

[0031] Specifically, by volume percentage, the base solution includes 0.2%-0.5% CJ2-6 hydroxypropyl guar gum, 0.1%-0.15% CJSJ-3 bactericide, 0.5%-0.55% CF-5D drainage aid, 0.5%-0.55% COP-3 clay stabilizer, 0.3%-0.35% TJ-1 conditioner, and the balance being water.

[0032] The crosslinking agent is a composite reagent of organoboron and ammonium persulfate; the alkali is a solid alkali, specifically one or more of sodium hydroxide and potassium hydroxide; and the hydrochloric acid is industrial hydrochloric acid with a concentration of 30%-36%.

[0033] This invention provides a method for preparing autogenous thermal fracturing fluid, comprising the following steps:

[0034] Add guar gum, bactericide, drainage aid, clay stabilizer and regulator to a measured amount of water and stir evenly to prepare a base solution;

[0035] Add a solid alkali to the base solution to dissolve it;

[0036] Add hydrochloric acid to the base solution.

[0037] Add a crosslinking agent to the base liquid;

[0038] Specifically, the method and process for determining the self-generating thermal fracturing fluid used in this patent are as follows:

[0039] S1 collects temperature and reservoir fluid properties of reservoirs in cold-damaged areas, including viscosity, density, freezing point, and water content.

[0040] S2. Based on the reservoir fluid characteristics collected in S1, the peak heat generation temperature of the fracturing fluid is determined. Then, the type of heat-generating agent is determined through laboratory experiments, and the optimal composition is determined to be an acid-base neutralization heat-generating system.

[0041] S3. Based on the type of heat-generating agent determined in S2, the formula was optimized through indoor experiments. The experimental simulation determined that the self-heating formula was 5-10% solid alkali + 4.6-9.1% hydrochloric acid.

[0042] S4, based on the heat-generating agent formulation determined in S3, is compounded with different types of fracturing fluids, including guar gum and EM30. + CNI was used to test the viscosity and heat generation effect of the mixture system, and the type of self-heating fracturing fluid was determined to be guar gum plus self-heating agent.

[0043] Based on the above-mentioned autogenous thermal fracturing fluid, the preparation process and dosage of each component of the autogenous thermal fracturing fluid are determined:

[0044] Step 1: Based on the types of self-heating fracturing fluid determined in the above steps, further conduct gelation performance tests on the crosslinking gel self-heating fracturing fluid by considering factors such as the order of addition of fracturing fluid base fluid, accelerator, and crosslinking agent, and optimize the fracturing fluid preparation process as base fluid-alkali-acid-crosslinking agent.

[0045] Step 2: Based on the self-heating fracturing fluid preparation process determined in Step 1, the viscosity of the mixture of guar gum and heat-generating agent at different concentrations is measured. The optimal guar gum fracturing fluid concentration is 0.2-0.5%, and the suitable crosslinking ratio is 0.4-0.6%.

[0046] The prepared autogenous thermal fracturing fluid is used in oil and gas extraction, specifically suitable for reservoirs with high crude oil viscosity, high pour point, and relatively poor fluidity. Its construction process is as follows: Figure 2 As shown, specifically:

[0047] Stir the pre-prepared base liquid evenly in the sand mixing tank;

[0048] The solid alkali is dissolved and then injected into the base solution;

[0049] Add the crosslinking agent to the sand mixing vehicle;

[0050] Finally, inject hydrochloric acid into the sand mixing truck.

[0051] The specific construction methods and techniques are as follows:

[0052] The first step is to determine the dosage of each component of the fracturing fluid for the target well based on the determined formula of the autogenous heating fracturing fluid and the fracturing fluid dosage of the target well, including the volume of guar gum, crosslinking agent, bactericide, drainage aid, clay stabilizer, regulator and water.

[0053] The second step involves adding the guar gum, bactericide, drainage aid, clay stabilizer, and regulator to a measured amount of water according to the dosage determined in the first step, stirring until evenly mixed to prepare a guar gum base solution.

[0054] The third step involves using the existing fracturing equipment to mix the guar gum base solution prepared in the second step with the proppant prepared by the proportioning pump in the mixing tank via the agitator, thus creating a uniform proppant-carrying base solution.

[0055] The proportioning pump controls the amount of fluid used. The agitator controls the amount of proppant used by controlling its rotation speed. The mixing tank mixes the proppant and fracturing fluid evenly using an internal stirring device; the proppant is mainly made of quartz sand.

[0056] The fourth step involves injecting solid alkali into the sand-carrying base fluid from the third step using a two-stage mixed self-generating thermal fracturing construction device.

[0057] The fifth step involves turning on the acid pump after the alkali has entered the sand mixing truck to inject the liquid from the fourth step, thereby achieving an exothermic acid-base reaction to form a self-heating sand-carrying base liquid.

[0058] The sixth step involves adding a crosslinking agent to the self-heating sand-carrying fluid from the fifth step to form a crosslinked sand-carrying fluid for fracturing operations.

[0059] Example 1

[0060] A self-generating thermal fracturing fluid, by volume percentage, comprises 0.2% guar gum, 0.12% CJSJ-3 bactericide, 0.53% CF-5D flow aid, 0.53% COP-3 clay stabilizer, 0.35% TJ-1 modifier, 0.4% organoboron and ammonium persulfate, 5% sodium hydroxide, and 6% hydrochloric acid, with the balance being water. First, 0.2% guar gum, 0.12% CJSJ-3 bactericide, 0.53% CF-5D flow aid, 0.53% COP-3 clay stabilizer, and 0.35% TJ-1 modifier are added to a measured amount of water and stirred until homogeneous to obtain a base fluid. Then, 5% sodium hydroxide is added to the base fluid to dissolve it, followed by 0.4% organoboron and ammonium persulfate, and finally 6% hydrochloric acid.

[0061] Example 2

[0062] A self-generating thermal fracturing fluid, by volume percentage, comprises 0.3% guar gum, 0.1% CJSJ-3 bactericide, 0.55% CF-5D flow aid, 0.53% COP-3 clay stabilizer, 0.35% TJ-1 modifier, 0.5% organoboron and ammonium persulfate, 7% sodium hydroxide, and 8% hydrochloric acid, with the balance being a base fluid. First, 0.3% guar gum, 0.1% CJSJ-3 bactericide, 0.55% CF-5D flow aid, 0.53% COP-3 clay stabilizer, and 0.35% TJ-1 modifier are added to a measured amount of water and stirred until homogeneous to obtain the base fluid. Then, 7% sodium hydroxide is added to the base fluid to dissolve it, followed by the addition of 0.5% organoboron and ammonium persulfate, and finally, 8% hydrochloric acid is added.

[0063] Example 3

[0064] A self-generating thermal fracturing fluid, by volume percentage, comprises 0.2% guar gum, 0.1% CJSJ-3 bactericide, 0.5% CF-5D flow aid, 0.53% COP-3 clay stabilizer, 0.35% TJ-1 modifier, 0.6% organoboron and ammonium persulfate, 5% sodium hydroxide, and 4.6% hydrochloric acid, with the balance being a base fluid. First, 0.2% guar gum, 0.1% CJSJ-3 bactericide, 0.5% CF-5D flow aid, 0.53% COP-3 clay stabilizer, and 0.35% TJ-1 modifier are added to a measured amount of water and stirred until homogeneous to obtain the base fluid. Then, 5% sodium hydroxide is added to the base fluid to dissolve it, followed by the addition of 0.6% organoboron and ammonium persulfate, and finally, 4.6% hydrochloric acid.

[0065] Example 4

[0066] A self-generating thermal fracturing fluid, by volume percentage, comprises 0.5% guar gum, 0.15% CJSJ-3 bactericide, 0.5% CF-5D flow aid, 0.55% COP-3 clay stabilizer, 0.3% TJ-1 modifier, 0.4% organoboron and ammonium persulfate, 8% sodium hydroxide, and 5.5% hydrochloric acid, with the balance being a base fluid. First, 0.5% guar gum, 0.15% CJSJ-3 bactericide, 0.5% CF-5D flow aid, 0.55% COP-3 clay stabilizer, and 0.3% TJ-1 modifier are added to a measured amount of water and stirred until homogeneous to obtain the base fluid. Then, 8% sodium hydroxide is added to the base fluid to dissolve it, followed by the addition of 0.4% organoboron and ammonium persulfate, and finally, 5.5% hydrochloric acid.

[0067] Example 5

[0068] A self-generating thermal fracturing fluid, by volume percentage, comprises 0.5% guar gum, 0.15% CJSJ-3 bactericide, 0.55% CF-5D flow aid, 0.55% COP-3 clay stabilizer, 0.3% TJ-1 modifier, 0.6% organoboron and ammonium persulfate, 10% sodium hydroxide, and 9.1% hydrochloric acid, with the balance being a base fluid. First, 0.5% guar gum, 0.15% CJSJ-3 bactericide, 0.55% CF-5D flow aid, 0.55% COP-3 clay stabilizer, and 0.3% TJ-1 modifier are added to a measured amount of water and stirred until homogeneous to obtain the base fluid. Then, 10% sodium hydroxide is added to the base fluid to dissolve it, followed by the addition of 0.6% organoboron and ammonium persulfate, and finally, 9.1% hydrochloric acid.

[0069] Example 6

[0070] A self-generating thermal fracturing fluid, by volume percentage, comprises 0.5% guar gum, 0.14% CJSJ-3 bactericide, 0.52% CF-5D flow aid, 0.54% COP-3 clay stabilizer, 0.33% TJ-1 modifier, 0.6% organoboron and ammonium persulfate, 5% sodium hydroxide, and 4.6% hydrochloric acid, with the balance being a base fluid. First, 0.5% guar gum, 0.14% CJSJ-3 bactericide, 0.52% CF-5D flow aid, 0.54% COP-3 clay stabilizer, and 0.33% TJ-1 modifier are added to a measured amount of water and stirred until homogeneous to obtain the base fluid. Then, 5% sodium hydroxide is added to the base fluid to dissolve it, followed by the addition of 0.6% organoboron and ammonium persulfate, and finally, 4.6% hydrochloric acid.

[0071] Example 7

[0072] A self-generating thermal fracturing fluid, by volume percentage, comprises 0.3% guar gum, 0.14% CJSJ-3 bactericide, 0.55% CF-5D flow aid, 0.55% COP-3 clay stabilizer, 0.3% TJ-1 modifier, 0.4% organoboron and ammonium persulfate, 10% sodium hydroxide, and 9.1% hydrochloric acid, with the balance being a base fluid. First, 0.3% guar gum, 0.14% CJSJ-3 bactericide, 0.55% CF-5D flow aid, 0.55% COP-3 clay stabilizer, and 0.3% TJ-1 modifier are added to a measured amount of water and stirred until homogeneous to obtain the base fluid. Then, 10% sodium hydroxide is added to the base fluid to dissolve it, followed by the addition of 0.4% organoboron and ammonium persulfate, and finally, 9.1% hydrochloric acid.

[0073] Example 8

[0074] A self-generating thermal fracturing fluid, by volume percentage, comprises 0.5% guar gum, 0.13% CJSJ-3 bactericide, 0.52% CF-5D flow aid, 0.54% COP-3 clay stabilizer, 0.3% TJ-1 modifier, 0.4% organoboron and ammonium persulfate, 5% sodium hydroxide, and 9.1% hydrochloric acid, with the balance being a base fluid. First, 0.5% guar gum, 0.13% CJSJ-3 bactericide, 0.52% CF-5D flow aid, 0.54% COP-3 clay stabilizer, and 0.3% TJ-1 modifier are added to a measured amount of water and stirred until homogeneous to obtain the base fluid. Then, 5% sodium hydroxide is added to the base fluid to dissolve it, followed by the addition of 0.4% organoboron and ammonium persulfate, and finally, 9.1% hydrochloric acid.

[0075] Sand-carrying performance and heat generation tests were conducted on the above embodiments, and the experimental data are shown in Table 1:

[0076] Table 1

[0077]

[0078] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A self-generating thermal fracturing fluid, characterized in that, The components include, in volume percentage: 0.2%-0.5% thickening agent, 0.1%-0.15% bactericide, 0.5%-0.55% cleanup additive, 0.5%-0.55% clay stabilizer, 0.3-0.35% regulator, 0.4%-0.6% crosslinking agent, 5%-10% base, 4.6%-9.1% hydrochloric acid, and the balance water; the thickening agent is guanidium gum.

2. The self-generating thermal fracturing fluid of claim 1, wherein, The guanidium gum is CJ2-6 hydroxypropyl guanidium gum.

3. The self-generating thermal fracturing fluid of claim 1, wherein, The bactericide is CJSJ-3 bactericide.

4. The self-generating thermal fracturing fluid of claim 1, wherein, The cleanup additive is CF-5D cleanup additive.

5. The self-generating thermal fracturing fluid of claim 1, wherein, The clay stabilizer is COP-3 clay stabilizer.

6. The self-generating thermal fracturing fluid of claim 1, wherein, The regulator is TJ-1 regulator.

7. The self-generating thermal fracturing fluid of claim 1, wherein, The crosslinking agent is organic boron and ammonium persulfate.

8. The self-generating thermal fracturing fluid of claim 1, wherein, The base is one or more of sodium hydroxide and potassium hydroxide, and the concentration of the hydrochloric acid is 30-36%.

9. A method of preparing the self-generating thermal fracturing fluid as claimed in claim 1, characterized by, The method includes the following steps: According to the determined amount, guanidium gum, bactericide, cleanup additive, clay stabilizer, and regulator are sequentially added into a certain amount of water and stirred to prepare guanidium gum base fluid; The guanidium gum base fluid and proppant are stirred to prepare sand-carrying base fluid; The base is added into the sand-carrying base fluid, and then hydrochloric acid is added to obtain self-generating heat sand-carrying base fluid; The crosslinking agent is added into the self-generating heat sand-carrying base fluid to prepare self-generating heat fracturing fluid.

10. The self-generating heat fracturing fluid of any one of claims 1-8 is applied in oil and gas exploitation.

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