Preparation-free authigenic composite acid fracturing fluid and application thereof

Abstract

The invention provides a preparation-free authigenic composite acid fracturing fluid and application thereof. The preparation-free authigenic composite acid fracturing fluid comprises an acid generator, an acid generator catalyst and a preparation-free fracturing fluid. The preparation-free authigenic composite acid fracturing fluid not only has the performance of a fracturing fluid, but also has the performance of an acid fluid. The method has the advantages that few additives are adopted, an acid generator is single, products obtained after hydrolysis under certain conditions are not only hydrochloric acid or organic acid, but hydrochloric acid and organic acid are adopted, and acid-rock reaction is more facilitated; acid production products are controllable; the acid generation temperature is high, and acid generation can be carried out under the condition of 150-200 DEG C; the effective efficiency is high, and the H < + > concentration is up to 1.36-4.6 mol / L. The fracturing fluid system can realize on-line preparation-free, simplify the on-site liquid preparation process, change the fracturing fluid formula at any time according to the requirement of a reservoir for liquid, achieve the effect of volume transformation of the fracturing fluid and the effect of acidification at the same time, and achieve the purpose of uniform acid distribution by enabling acid generated at the reservoir temperature to reach the top end of a crack along with the fracturing fluid.

Description

Technical Field

[0001] The invention belongs to the technical field of fracturing fluids, and in particular relates to a self-generated composite acid fracturing fluid without preparation and application thereof. Background Art

[0002] The exploration depth of high-temperature carbonate reservoirs in my country is getting deeper and deeper, mostly at 6000m-8000m, and is currently advancing to 10,000-meter deep wells. The reservoir temperatures encountered are getting higher and higher, most of which exceed 160°C, and even up to 230°C. The characteristics of my country's carbonate reservoirs are strong heterogeneity, low permeability and density, and high stress. The previous carbonate reservoir transformation technology is suitable for reservoirs with a well depth of less than 7000m and a temperature below 160°C. The acid technology mainly includes ordinary hydrochloric acid, slow hydrochloric acid, emulsified acid, thickened acid, cross-linked gel acid, surfactant self-steering acid, etc., and has achieved good results. The implementation process mostly uses slow acid formation or polymer linear gel formation and a combination of these acids. With the continuous deepening of exploration depth and the continuous increase in temperature, the existing acid technology and process technology are no longer suitable, and both tools and liquids are facing greater challenges. In high-temperature deep wells, the existing acid system reacts too quickly, the filtration loss increases accordingly, and the acid cannot reach the front end of the fracture; at the same time, the unevenness of reservoir transformation is aggravated, and the difficulty of uniform acid distribution increases significantly. The excessively fast reaction speed causes the acid to enter the high-permeability area, and the low-permeability area cannot be effectively transformed; the higher reservoir temperature causes the previous various slow-rate acids to pose a greater threat to the integrity of the wellbore, and the existing corrosion inhibitors are also difficult to effectively protect the tubing.

[0003] Compared with other acidic fluids, autogenous acid has the advantages of being non-acidic or weakly acidic at room temperature, generating acid at a certain temperature, having a low corrosion rate, and having a low acid-rock reaction rate. It is an important way to solve the problem of slow acidification of high-temperature deep wells. Autogenous acid types include autogenous hydrofluoric acid, autogenous hydrochloric acid, autogenous organic acid, and composite autogenous acid. The acid generation temperature reported so far is usually lower than 150°C, which still has certain limitations for the current ultra-deep and ultra-high temperature wells. At present, the non-admixed fracturing fluid has been used in many oil fields and has achieved good results. There are only 2-3 types of fracturing fluid additives, among which the emulsion thickener can realize continuous construction, can quickly become sticky, and has good viscoelasticity. The "stepless speed change" from slippery water to sand-carrying fluid can be achieved by changing the dosage. In order to better apply it to the reservoir transformation of ultra-high temperature wells, it is necessary to add a cross-linking agent to achieve better heat resistance, shear resistance and sand carrying performance. Emulsion thickener fracturing fluid does not require advance preparation or continuous mixing vehicles, which greatly reduces construction costs. It can be applied to a variety of oil and gas reservoirs and has good application prospects and market value.

[0004] CN113755149A discloses a self-generated acid cross-linked fracturing fluid and its application, comprising a thickener, a cross-linker, an acid generator, an activator and water, and is applied to high-temperature carbonate rocks at 130°C to 150°C. CN106833596A discloses a self-generated acid fracturing fluid and its preparation method and application, the fracturing fluid is composed of 10%-40% organic ester, 0.3%-1% thickener, 1%-4% degradable fluid loss reducer and the balance water, and the temperature of the reservoir is 120°C-160°C. CN111500276A discloses a thickened self-generated acid with high viscosity and low acid rock reaction rate, comprising a thickener: 0.4-0.8%; acid generator A: 10-30%; acid generator B: 1-10%; clay stabilizer: 1-2%; corrosion inhibitor: 2-4%, and the balance is water. Summary of the invention

[0005] In view of the deficiencies of the prior art, the object of the present invention is to provide a self-generated composite acid fracturing fluid and its application.

[0006] To achieve this object, the present invention adopts the following technical solutions:

[0007] In a first aspect, the present invention provides a self-generated composite acid fracturing fluid without formulation, wherein the self-generated composite acid fracturing fluid without formulation comprises an acid generating agent, an acid generating catalyst and a self-generated composite acid fracturing fluid without formulation;

[0008] Preferably, the formulation-free fracturing fluid comprises an emulsion thickener, a cross-linking agent and a breaker.

[0009] The self-generated composite acid fracturing fluid of the present invention not only has the performance of fracturing fluid, but also has the performance of acid liquid. There are few types of additives, and the acid generator is single. The product after hydrolysis under certain conditions is not only hydrochloric acid or organic acid, but two types of hydrochloric acid and organic acid, which is more conducive to the acid-rock reaction; the acid-generating product is controllable; the acid-generating temperature is high, and the acid can be generated under the condition of 150℃-200℃; the effectiveness efficiency is high: H + The concentration is as high as 1.36-4.6mol / L. The fracturing fluid system can achieve online free preparation, simplify the on-site preparation process, and change the fracturing fluid formula at any time according to the reservoir's demand for liquid, which can achieve the effect of fracturing fluid volume transformation and acidification at the same time. The acid generated at the reservoir temperature can reach the top of the crack with the fracturing fluid, thereby achieving the purpose of uniform acid distribution.

[0010] Preferably, the self-generated composite acid fracturing fluid without formulation comprises 8-24 parts of acid generating agent, 1-5 parts of acid generating catalyst and 71-89 parts of the self-generated composite acid fracturing fluid by weight;

[0011] The weight proportion of the acid generator can be 8 parts, 10 parts, 16 parts, 20 parts, 21 parts, 22 parts, 23 parts, 24 parts, etc. Specific values ​​within the above numerical range can be selected, and will not be described one by one here.

[0012] The weight proportion of the acid generating catalyst can be 1 part, 1.5 parts, 2 parts, 3 parts, 4 parts, 5 parts, etc. Any specific value within the above numerical range can be selected, and will not be described in detail here.

[0013] The weight proportion of the non-adjustable fracturing fluid can be 71 parts, 72 parts, 74 parts, 76 parts, 78 parts, 86 parts, 88 parts, 89 parts, etc. Specific values ​​within the above numerical range can be selected, and will not be described one by one here.

[0014] Preferably, the non-adjustable fracturing fluid comprises, by weight, 0.7-1.6 parts of an emulsion thickener, 0.5-0.8 parts of a cross-linking agent, and 0.01-0.05 parts of a breaker.

[0015] The weight proportion of the emulsion thickener may be 0.7 parts, 0.8 parts, 0.9 parts, 1.0 parts, 1.2 parts, 1.4 parts, 1.6 parts, etc.

[0016] The weight proportion of the cross-linking agent can be 0.5 part, 0.6 part, 0.65 part, 0.7 part, 0.75 part, 0.8 part, etc.

[0017] The weight percentage of the breaker can be 0.01, 0.02, 0.03, 0.04, 0.05, etc. Specific values ​​within the above numerical range can be selected, and will not be described one by one here.

[0018] Preferably, the acid generator comprises any one or a combination of at least two of haloacetic acid ester, N-haloacetylamino acid ester or N-haloacetylamino acid;

[0019] Preferably, the acid generating catalyst is selected from any one of chloride, bromide or iodide or a combination of at least two thereof; more preferably, it is any one of bromide or iodide or a combination of at least two thereof.

[0020] Preferably, the acid generator comprises any one or a combination of at least two of chloroacetic acid ester, N-chloroacetyl amino acid ester or N-chloroacetyl amino acid;

[0021] Preferably, the acid generating catalyst is selected from any one of sodium bromide, potassium bromide, sodium iodide or potassium iodide, or a combination of at least two thereof.

[0022] Preferably, the chloroacetic acid ester is selected from any one of ethyl 4-chloroacetoacetate, ethyl 2,4-dichloroacetoacetate or ethyl 2-chloroacetoacetate, or a combination of at least two thereof;

[0023] Preferably, the N-chloroacetyl amino acid ester is selected from any one or a combination of at least two of N-chloroacetyl glycine ethyl ester, N-chloroacetyl glycine methyl ester or N-chloroacetyl glycine propyl ester;

[0024] Preferably, the N-chloroacetylamino acid is selected from any one of N-chloroacetylglycine, N-chloroacetylalanine or N-chloroacetyllysine, or a combination of at least two thereof.

[0025] Preferably, the raw materials for preparing the emulsion thickener include any one of acrylamide, 2-acrylamide-2-methylpropane sulfonic acid, acrylic acid, a diene hydrophobic monomer or white oil, or a combination of at least two thereof; more preferably, the raw materials include acrylamide, 2-acrylamide-2-methylpropane sulfonic acid, acrylic acid, a diene hydrophobic monomer and white oil.

[0026] Preferably, the raw materials for preparing the cross-linking agent include any one of zirconium oxychloride, triethanolamine, lactic acid or ethylene glycol ester, or a combination of at least two thereof; preferably, a combination of zirconium oxychloride, triethanolamine, lactic acid and ethylene glycol ester.

[0027] Preferably, the cross-linking agent includes any one of persulfate, hydrogen peroxide or amylase; preferably persulfate.

[0028] In a second aspect, the present invention provides a use of the self-generated composite acid fracturing fluid without preparation as described in the first aspect in the transformation of carbonate rock or sandstone reservoirs.

[0029] The use temperature of the self-generated composite acid fracturing fluid without preparation is 120-200°C.

[0030] The use temperature of the self-generated composite acid fracturing fluid can be 120° C., 130° C., 140° C., 150° C., 160° C., 170° C., 180° C., 190° C., 200° C., etc. Specific point values ​​within the above numerical range can be selected, and they will not be repeated here.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] The self-generated composite acid fracturing fluid of the present invention not only has the performance of fracturing fluid, but also has the performance of acid liquid. There are few types of additives, and the acid generator is single. The product after hydrolysis under certain conditions is not only hydrochloric acid or organic acid, but two types of hydrochloric acid and organic acid, which is more conducive to the acid-rock reaction; the acid-generating product is controllable; the acid-generating temperature is high, and the acid can be generated under the condition of 150℃-200℃; the effectiveness efficiency is high: H +The concentration is as high as 1.36-4.6mol / L. The fracturing fluid system can achieve online free preparation, simplify the on-site preparation process, and change the fracturing fluid formula at any time according to the reservoir's demand for liquid, which can achieve the effect of fracturing fluid volume transformation and acidification at the same time. The acid generated at the reservoir temperature can reach the top of the crack with the fracturing fluid, thereby achieving the purpose of uniform acid distribution. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 is the high temperature and shear resistance curve of the fracturing fluid in Example 1;

[0034] Figure 2 is the high temperature and shear resistance curve of the fracturing fluid in Example 6;

[0035] Figure 3 This is the relationship between the acid concentration (relative to the concentration of hydrochloric acid, %), temperature and time in Example 6. DETAILED DESCRIPTION

[0036] The technical solution of the present invention is further described below in conjunction with the accompanying drawings and through specific implementation methods. It should be understood by those skilled in the art that the embodiments are only to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0037] Example 1

[0038] This embodiment provides a self-generated composite acid fracturing fluid without preparation, which is prepared by the following method:

[0039] According to the mass fraction, the acid generating agent ethyl 2,4-dichloroacetoacetate, the acid generating catalyst potassium bromide and the non-prepared fracturing fluid are mixed according to 9, 3, 88, wherein the non-prepared fracturing fluid includes 1.0% thickener, 0.6% cross-linking agent and the balance water, to obtain the non-prepared autogenous composite acid fracturing fluid. The fracturing fluid is hydrolyzed at 150°C for 3 hours, and the reaction experiment between the fracturing fluid and carbonate rock after the autogenous acid hydrolysis at this temperature is carried out (the amount of hydrogen ion substances consumed by the rock after the unit volume of autogenous acid reacts with the rock at 150°C and the rock specific surface area for 3 hours is used to characterize the autogenous acid generation capacity), and the molar concentration of hydrogen ions produced is calculated. The fracturing fluid is also used for temperature and shear resistance tests.

[0040] The viscosity of the cross-linked acid fracturing fluid is greatly affected by temperature. When the temperature rises to 150°C, the viscosity of the system decreases from 500 Pa·s at the initial heating to 150 mPa·s. When shearing continues at 150°C, the viscosity gradually decreases and remains basically unchanged after 120 minutes. The system viscosity is about 20 mPa·s.

[0041] Example 2

[0042] This embodiment provides a self-generated composite acid fracturing fluid without preparation, which is prepared by the following method:

[0043] By weight, the acid generating agent ethyl 2,4-dichloroacetoacetate, the acid generating catalyst potassium bromide and the non-prepared fracturing fluid are mixed in the proportion of 16, 3, and 81, wherein the non-prepared fracturing fluid includes 1.3% thickener, 0.6% cross-linking agent and the balance water, to obtain the non-prepared autogenous composite acid fracturing fluid. The fracturing fluid is hydrolyzed at 170°C for 3h, and the reaction experiment between the fracturing fluid and carbonate rock after autogenous acid hydrolysis is conducted to calculate the molar concentration of hydrogen ions produced.

[0044] Example 3

[0045] This embodiment provides a self-generated composite acid fracturing fluid and a preparation method thereof, which is prepared by the following method:

[0046] By weight, the acid generating agent N-chloroacetylalanine, the acid generating catalyst potassium bromide and the non-prepared fracturing fluid are mixed in the ratio of 24, 2, and 74, wherein the non-prepared fracturing fluid includes 1.3% thickener, 0.6% cross-linking agent and the balance water, to obtain the non-prepared autogenous composite acid fracturing fluid. The fracturing fluid is hydrolyzed at 200°C for 3h, and the reaction experiment between the fracturing fluid and carbonate rock after autogenous acid hydrolysis is conducted to calculate the molar concentration of hydrogen ions produced.

[0047] Example 4

[0048] This embodiment provides a self-generated composite acid fracturing fluid without preparation, which is prepared by the following method:

[0049] By weight, the acid generating agent N-chloroacetylalanine ethyl ester, the acid generating catalyst potassium bromide and the non-prepared fracturing fluid are mixed in the ratio of 24, 2, and 74, wherein the non-prepared fracturing fluid includes 1.3% thickener, 0.6% cross-linking agent and the balance water to obtain the non-prepared autogenous composite acid fracturing fluid. The fracturing fluid is hydrolyzed at 170°C for 3h, and the reaction experiment between the fracturing fluid and carbonate rock after autogenous acid hydrolysis is conducted to calculate the molar concentration of hydrogen ions produced.

[0050] Example 5

[0051] This embodiment provides a self-generated composite acid fracturing fluid without preparation, which is prepared by the following method:

[0052] By weight, the acid generating agent N-chloroacetylglycine, the acid generating catalyst potassium iodide and the non-prepared fracturing fluid are mixed in the ratio of 24, 4, and 72, wherein the non-prepared fracturing fluid includes 1.3% thickener, 0.6% cross-linking agent and the balance water, to obtain the non-prepared autogenous composite acid fracturing fluid. The fracturing fluid is hydrolyzed at 170°C for 3h, and the reaction experiment between the fracturing fluid and carbonate rock after autogenous acid hydrolysis is conducted to calculate the molar concentration of hydrogen ions produced.

[0053] Example 6

[0054] This embodiment provides a self-generated composite acid fracturing fluid without preparation, which is prepared by the following method:

[0055] By weight, the acid generating agent N-chloroacetyl glycine ethyl ester, the acid generating catalyst potassium bromide and the non-prepared fracturing fluid are mixed in the ratio of 40, 4, and 56, wherein the non-prepared fracturing fluid includes 1.0% thickener, 0.6% cross-linking agent and the balance water, to obtain the non-prepared autogenous composite acid fracturing fluid. The fracturing fluid is hydrolyzed at 180° C. for 3 hours, and the reaction experiment between the fracturing fluid and carbonate rock after autogenous acid hydrolysis is conducted to calculate the molar concentration of hydrogen ions produced.

[0056] The viscosity of the cross-linked acid fracturing fluid is greatly affected by temperature. When the temperature rises to 180°C, the viscosity of the system decreases from 120 Pa·s at the initial heating to 40 mPa·s. When shearing continues at 180°C, the viscosity gradually decreases and remains basically unchanged after 90 minutes. The viscosity of the system is about 20 mPa·s.

[0057] Comparative Example 1

[0058] This embodiment provides a self-generated composite acid fracturing fluid without preparation, which is prepared by the following method:

[0059] By weight, the acid generating agent 2,4-dichlorolevulinic acid propyl ester, the acid generating catalyst potassium bromide and the free fracturing fluid are mixed according to 24, 4, and 72, wherein the free fracturing fluid includes 1.3% thickener, 0.6% cross-linking agent and the balance water to obtain the free autogenous composite acid fracturing fluid. The difference between this comparative example and Example 6 is that the acid generating agent is different, and the others remain unchanged. The fracturing fluid is hydrolyzed at 180°C for 3h, and the reaction experiment of the fracturing fluid and carbonate rock after autogenous acid hydrolysis is performed to calculate the molar concentration of hydrogen ions produced.

[0060] Comparative Example 2

[0061] This embodiment provides a self-generated composite acid fracturing fluid and a preparation method thereof, which is prepared by the following method:

[0062] By weight, the acid generating agent N-chloroacetyl glycine propyl ester, the acid generating catalyst zinc bromide and the free fracturing fluid are mixed according to 24, 4, and 72, wherein the free fracturing fluid includes 1.3% thickener, 0.6% cross-linking agent and the balance water to obtain the free autogenous composite acid fracturing fluid. The difference between this comparative example and Example 6 is that the acid generating agent and the acid generating catalyst are different, and the others remain unchanged. The fracturing fluid is hydrolyzed at 200°C for 3h, and the reaction experiment of the fracturing fluid and carbonate rock after autogenous acid hydrolysis is performed to calculate the molar concentration of hydrogen ions produced.

[0063] The molar concentrations of hydrogen ions in Examples 1-6 and Comparative Examples 1-2 are shown in Table 1.

[0064] Table 1

[0065]

[0066]

[0067] The applicant declares that the present invention illustrates the detailed process flow of the present invention through the above-mentioned embodiments, but the present invention is not limited to the above-mentioned detailed process flow, that is, it does not mean that the present invention must rely on the above-mentioned detailed process flow to be implemented. Those skilled in the art should understand that any improvement of the present invention, equivalent replacement of various raw materials of the product of the present invention, addition of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A self-generated composite acid fracturing fluid without preparation, characterized in that: The self-generated composite acid fracturing fluid without any preparation comprises an acid generating agent, an acid generating catalyst and a self-generated composite acid fracturing fluid without any preparation; The free-formulation fracturing fluid comprises an emulsion thickener, a cross-linking agent and a breaker.

2. The self-generated composite acid fracturing fluid according to claim 1, characterized in that: The self-generated composite acid fracturing fluid without any preparation comprises 8-24 parts of an acid generating agent, 1-5 parts of an acid generating catalyst and 71-89 parts of the self-generated composite acid fracturing fluid by weight; Preferably, the non-adjustable fracturing fluid comprises, by weight, 0.7-1.6 parts of an emulsion thickener, 0.5-0.8 parts of a cross-linking agent, and 0.01-0.05 parts of a breaker.

3. The self-generated composite acid fracturing fluid according to claim 1 or 2, characterized in that: The acid generator includes any one or a combination of at least two of haloacetic acid ester, N-haloacetylamino acid ester or N-haloacetylamino acid; Preferably, the acid generating catalyst is selected from any one of chloride, bromide or iodide or a combination of at least two thereof; more preferably bromide and / or iodide.

4. The self-generated composite acid fracturing fluid according to any one of claims 1 to 3, characterized in that: The acid generator includes any one of chloroacetic acid ester, N-chloroacetyl amino acid ester or N-chloroacetyl amino acid, or a combination of at least two thereof; Preferably, the acid generating catalyst is selected from any one of sodium bromide, potassium bromide, sodium iodide or potassium iodide, or a combination of at least two thereof.

5. The self-generated composite acid fracturing fluid according to claim 4, characterized in that: The chloroacetic acid ester is selected from any one of ethyl 4-chloroacetoacetate, ethyl 2,4-dichloroacetoacetate or ethyl 2-chloroacetoacetate, or a combination of at least two thereof; Preferably, the N-chloroacetyl amino acid ester is selected from any one or a combination of at least two of N-chloroacetyl glycine ethyl ester, N-chloroacetyl glycine methyl ester or N-chloroacetyl glycine propyl ester; Preferably, the N-chloroacetylamino acid is selected from any one of N-chloroacetylglycine, N-chloroacetylalanine or N-chloroacetyllysine, or a combination of at least two thereof.

6. The self-generated composite acid fracturing fluid according to any one of claims 1 to 5, characterized in that: The raw materials for preparing the emulsion thickener include any one of acrylamide, 2-acrylamide-2-methylpropane sulfonic acid, acrylic acid, a diene hydrophobic monomer or white oil, or a combination of at least two thereof; preferably, a combination of acrylamide, 2-acrylamide-2-methylpropane sulfonic acid, acrylic acid, a diene hydrophobic monomer and white oil.

7. The self-generated composite acid fracturing fluid according to any one of claims 1 to 6, characterized in that: The raw materials for preparing the cross-linking agent include any one of zirconium oxychloride, triethanolamine, lactic acid or ethylene glycol ester or a combination of at least two thereof; preferably, the combination of zirconium oxychloride, triethanolamine, lactic acid and ethylene glycol ester.

8. The self-generated composite acid fracturing fluid according to any one of claims 1 to 7, characterized in that: The degumming agent includes any one of persulfate, hydrogen peroxide or amylase, preferably persulfate.

9. Use of the self-generated composite acid fracturing fluid according to any one of claims 1 to 8 in the reconstruction of carbonate reservoirs or sandstone reservoirs.

10. The use of the self-generated composite acid fracturing fluid without preparation according to claim 9 in carbonate or sandstone reservoir reconstruction, characterized in that: The use temperature of the self-generated composite acid fracturing fluid without preparation is 120-200°C.

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