Blockage-removing, scale-inhibiting and energy-increasing type integrated fracturing fluid system as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of oil field chemicals, and particularly relates to a plug removal, scale inhibition and energy increasing type integrated fracturing fluid system as well as a preparation method and application thereof. The fracturing fluid is prepared from the following components in percentage by weight: 20 to 30 percent of the water-soluble high-molecular polymer provided by the invention, 20 to 40 percent of a non-polar solvent, 0.01 to 5 percent of a cross-linking agent, 0.5 to 5 percent of a suspending agent, 0.5 to 5 percent of an emulsifying agent, 0.5 to 10 percent of a blocking remover, 0.5 to 10 percent of a scale inhibitor and 1 to 20 percent of an energy increasing agent. The water-soluble high-molecular polymer is obtained by carrying out copolymerization on acrylamide, sodium acrylate, 2-acrylamido-2-methyl propane sodium sulfonate and cis-13-docosamido propyl dimethyl hydroxypropyl betaine, and the water-soluble high-molecular polymer is obtained by carrying out copolymerization on acrylamide, sodium acrylate, 2-acrylamido-2-methyl propane sodium sulfonate and cis-13-docosamido propyl dimethyl hydroxypropyl betaine. The problems that low-temperature gel breaking of medium and low-temperature oil and gas reservoirs and conventional water-based fracturing fluid, cold damage to high-wax-content and high-pour-point oil reservoirs, scaling of output liquid after fracturing influences the yield and the like can be solved.

Description

Technical Field

[0001] The invention belongs to the technical field of oilfield chemicals, and in particular relates to an integrated fracturing fluid system for removing blockage, preventing scale and enhancing energy, and a preparation method and application thereof. Background Art

[0002] There are still many low-temperature, low-pressure, high-wax and high-condensate oil reservoirs in my country. When conventional water-based fracturing fluids are used for fracturing operations in the above-mentioned reservoirs, defects such as incomplete gel breaking and poor flowback capacity of the fracturing fluids are often observed. The main reason is that the reservoir temperature is low and the low-temperature gel breaking ability of conventional breakers is weak; the cold fluid injected into the formation causes cold damage to the reservoir, reducing the conductivity of the fracturing cracks.

[0003] In the past decade, large-scale hydraulic fracturing of unconventional oil and gas resources has had a significant impact on the world's energy landscape. However, hydraulic fracturing produces a large amount of flowback fluid, whose evaluation indicators include mineralization, turbidity, organic matter, etc. The flowback fluid from shale gas well fracturing in the United States is mainly reused in fracturing construction through deep well injection or recovery. The dynamic scaling trend test study of fracturing fluid flowback fluid shows that the scaling trend of fracturing output fluid significantly and seriously affects oil and gas production.

[0004] Therefore, it is necessary to develop new fracturing fluid technology that can effectively solve on-site technical problems, have the characteristics of unblocking, scale prevention, and waterproofing, and the integrated use of slippery water and sand-carrying fluid is simple to construct, easy to flow back, and has little damage to water-sensitive reservoirs. It can enhance the reservoir volume transformation capacity, improve the recovery rate, and have good production and application prospects. Summary of the invention

[0005] In order to address the deficiencies in the prior art, the present invention provides an integrated fracturing fluid system for unblocking, scaling prevention and energy enhancement, and a preparation method and application thereof, so as to solve the problems of medium and low temperature oil and gas reservoirs, low temperature gel breaking of conventional water-based fracturing fluids and their cold damage to high wax content and high condensate oil reservoirs, and scaling of the produced fluid after fracturing affecting production.

[0006] The technical solution provided by the present invention is as follows:

[0007] A water-soluble high molecular polymer is prepared by the following method: acrylamide, sodium acrylate, sodium 2-acrylamido-2-methylpropane sulfonate and cis-13-docosapentaenoyl propyl dimethyl hydroxypropyl betaine are selected, and the four monomers are copolymerized under the action of an initiator to form a water-soluble high molecular polymer with a molecular weight of 3 to 30 million.

[0008] The water-soluble high molecular polymer provided by the present invention has a significant viscosity increasing effect and can be applied to fracturing fluid to improve the drag reduction and sand carrying performance of the fracturing fluid.

[0009] Specifically, the molar ratio of acrylamide, sodium acrylate, sodium 2-acrylamido-2-methylpropane sulfonate and cis-13-docosapentaenoylamidopropyl dimethyl hydroxypropyl betaine is: (10-50): (5-50): (5-50): (0.1-10).

[0010] Specifically, the initiator is selected from ammonium persulfate and sodium bisulfite, and the weight ratio of the initiator to the copolymer reaction monomer is (0.001-1%):1.

[0011] Specifically, the copolymerization temperature is 5-50°C.

[0012] Specifically, the copolymerization reaction time is 4-24 hours.

[0013] The method also provides an integrated fracturing fluid system for unblocking, scale inhibition and energy enhancement, which comprises the following components by weight percentage: 20-30% of the water-soluble high molecular polymer provided by the present invention, 20-40% of the non-polar solvent, 0.01-5% of the cross-linking agent, 0.5-5% of the suspending agent, 0.5-5% of the emulsifier, 0.5-10% of the unblocking agent, 0.5-10% of the scale inhibitor, and 1-20% of the energy enhancer.

[0014] The integrated fracturing fluid system for unblocking, scaling prevention and energy enhancement provided by the present invention can effectively solve the scaling of high-mineralization mixing water during volume fracturing, the strong velocity sensitivity of clay particle migration in the transformed reservoir, the low formation pressure coefficient, the presence of oil and gas in the well but no production after fracturing, etc., and solve the technical problems of "low permeability, low temperature, low flowback" reservoirs, poor reservoir drainage after fracturing, and affecting oil and gas testing and production.

[0015] Specifically, the non-polar solvent is selected from one, two or three of white oil, solvent oil and xylene, and the weight ratio of the three is (5-10):(2-5):(2-5), preferably 2:1:1.

[0016] Specifically, the crosslinking agent is a water-soluble phenolic resin or an organic zirconium or a mixture of the two.

[0017] Specifically, the suspending agent is modified diatomaceous earth or hydrophilic nano-silicon dioxide or a mixture of both.

[0018] Specifically, the emulsifier is selected from one or more of sorbitan fatty acid esters, polyoxyethylene sorbitan fatty acid esters, alkylphenol polyoxyethylene ethers or alkanolamides.

[0019] Specifically, the blocking agent is selected from one or more of oxalic acid, citric acid, aminosulfonic acid, sodium ethylenediaminetetramethyl phosphate, sodium polyepoxysuccinate, sodium gluconate, ethylenediaminetetraacetic acid, sodium acetate, sodium hydroxyacetate, sorbitan fatty acid ester, diethylene glycol laurate, diphenyl ether gemini surfactant, nonylphenol polyoxyethylene ether or alkyl glucose anhydride.

[0020] Specifically, the scale inhibitor is selected from one or more of tannin, carboxymethyl cellulose, sodium polyacrylate, hydrolyzed maleic anhydride, maleic acid-acrylic acid copolymer, acrylic acid-methacrylate copolymer, acrylic acid-methacrylic acid sulfonic acid copolymer or acrylic acid-methacrylate-hydroxyalkyl acrylate copolymer.

[0021] Specifically, the energizer is a mixture of ammonium chloride and sodium nitrate, and the mixing ratio of the two is 1:(1-10), preferably 0.75:1.

[0022] The present invention also provides a method for preparing an integrated fracturing fluid system for removing blockage, preventing scale and enhancing energy, comprising the following steps:

[0023] 1) According to the amount of the formula, the non-polar solvent, cross-linking agent, emulsifier and suspending agent are added to the reaction kettle respectively, and the stirring is turned on and the mixture is uniformly sheared by a variable frequency emulsification pump; the stirring speed for uniform mixing is 2000-3000 r / min, and the stirring time is 0.5-2h;

[0024] 2) adding a water-soluble high molecular polymer to the mixture obtained in step 1), and mixing the mixture uniformly by circulating shearing with a variable frequency emulsifying pump; the stirring speed for the uniform mixing is 2000-3000 r / min, and the stirring time is 0.5-2h;

[0025] 3) Adding a plugging remover, a scale inhibitor, and an energizer to the mixture obtained in step 2), and mixing them evenly by circulating shearing with a variable frequency emulsifier pump, thereby obtaining the plugging remover, scale inhibitor, and energizer integrated fracturing fluid system; the stirring speed for the even mixing is 500-2000 r / min, and the stirring time is 0.5-1h.

[0026] The present invention also provides the application of an integrated fracturing fluid system for removing blockage, preventing scale and enhancing energy as a fracturing fluid for developing unconventional oil and gas reservoirs such as low-permeability or ultra-low-permeability oil and gas reservoirs. The dosage of the fracturing fluid is 0.01%-1% of the total mass of the prepared liquid.

[0027] Compared with the prior art, the present invention has the following advantages:

[0028] 1. The present invention provides an integrated fracturing fluid system for unblocking, scale prevention and energy enhancement, which can solve the problems of scaling of high-mineralization mixing water during volume fracturing, strong velocity sensitivity of clay particle migration in the transformed reservoir, low formation pressure coefficient, oil and gas in the well but no production after fracturing, etc. It has the characteristics of unblocking, scale prevention, water lock, simple construction of integrated use of slippery water and sand-carrying fluid, easy backflow, and little damage to water-sensitive reservoirs;

[0029] 2. The integrated fracturing fluid system can achieve adjustable viscosity within the range of 1 to 200 mPa·s, temperature resistance of 180°C, drag reduction rate of 80%; 50°C scale removal rate, carbonate scale below 5mm, scale removal rate can reach more than 95%; 50°C scale inhibition rate, can achieve calcium carbonate ≥90%, calcium sulfate ≥90%, barium sulfate ≥70% respectively;

[0030] 3. The preparation method of the integrated fracturing fluid system of the present invention is simple, easy to operate, low in cost, and has good economic promotion value. DETAILED DESCRIPTION

[0031] The principles and features of the present invention are described below. The examples given are only used to explain the present invention and are not used to limit the scope of the present invention.

[0032] Preparation of water-soluble polymer A:

[0033] Acrylamide, sodium acrylate, sodium 2-acrylamido-2-methylpropane sulfonate and cis-13-docosapentaenoylpropyl dimethyl hydroxypropyl betaine are mixed in a molar ratio of 50:30:15:5, and a composite initiator is added in an amount of 0.01 wt% based on the weight of the copolymer reaction monomer. The specific composition of the composite initiator is ammonium persulfate and sodium bisulfite in a ratio of 1:1. The mixture is reacted at 30° C. for 8 hours to obtain the product.

[0034] The viscosity average molecular weight of the obtained water-soluble high molecular weight polymer was measured and the result was 12 million.

[0035] Example 1 (produced in 100 kg)

[0036] The ingredients are as follows:

[0037]

[0038]

[0039] Add white oil, solvent oil, xylene and isomeric alcohol tridecanol into a 50°C reactor and stir at 400r / min. Continue stirring and start the high shear emulsifier equipped with the reactor at a shear cycle speed of 2000r / min. After 20 minutes, add water-soluble phenolic resin and organic zirconium. After 20 minutes of mixed reaction, add sorbitan fatty acid ester (S60), polyoxyethylene sorbitan fatty acid ester (Tween80), alkylphenol polyoxyethylene ether (APEO), and alkanolamide (oleic acid diethanolamide). Mix and react for 20 minutes. After 30 minutes, modified diatomaceous earth and hydrophilic nano-silica are added, and after mixing and reacting for 20 minutes, water-soluble polymer A is added. After mixing and reacting for 60 minutes, oxalic acid, sodium polyepoxysuccinate, diphenyl ether gemini surfactant, nonylphenol polyoxyethylene ether, tannin, carboxymethyl cellulose, hydrolyzed maleic anhydride, ammonium chloride and sodium nitrate are added. The shear cycle speed is 1000 r / min, and the mixing reaction is carried out for 60 minutes to allow each component to fully react and be evenly mixed, so as to obtain the integrated fracturing fluid system of plugging removal, scale inhibition and energy enhancement.

[0040] Example 2 (produced in 100 kg)

[0041] The ingredients are as follows:

[0042]

[0043]

[0044] Add white oil, solvent oil, xylene and isomeric alcohol tridecanol into a 50°C reactor and stir at 400 r / min. Continue stirring and start the high shear emulsifier equipped with the reactor at a shear cycle speed of 2000 r / min. After 20 minutes, add water-soluble phenolic resin and organic zirconium. After mixing and reacting for 20 minutes, add sorbitan fatty acid ester (S60), polyoxyethylene sorbitan fatty acid ester (Tween80), alkylphenol polyoxyethylene ether (APEO) and alkanolamide (oleic acid diethanolamide). Mix and react for 30 minutes. n, then add modified diatomaceous earth and hydrophilic nano-silica, mix and react for 20 minutes, then add water-soluble polymer A, mix and react for 60 minutes, then add citric acid, sodium polyepoxysuccinate, diphenyl ether gemini surfactant, nonylphenol polyoxyethylene ether, sodium polyacrylate, maleic acid-acrylic acid copolymer, hydrolyzed maleic anhydride, ammonium chloride and sodium nitrate, shear cycle speed is 1000r / min, mix and react for 60 minutes, so that each component can fully act and be evenly mixed, so as to obtain the said integrated fracturing fluid system of plugging removal, scale inhibition and energy enhancement.

[0045] Example 3 (produced by 100 kg)

[0046] The ingredients are as follows:

[0047]

[0048] Add white oil, solvent oil, xylene and isomeric alcohol tridecanol into a 50°C reactor and stir at 400 r / min. Continue stirring and start the high shear emulsifier equipped with the reactor at a shear cycle speed of 2000 r / min. After 20 minutes, add water-soluble phenolic resin and organic zirconium. After mixing and reacting for 20 minutes, add sorbitan fatty acid ester (S60), polyoxyethylene sorbitan fatty acid ester (Tween80), alkylphenol polyoxyethylene ether (APEO) and alkanolamide (oleic acid diethanolamide). Mix and react for 3 minutes. After 0 minutes, modified diatomaceous earth and hydrophilic nano-silica are added, and after mixing and reacting for 20 minutes, water-soluble polymer A is added. After mixing and reacting for 60 minutes, aminosulfonic acid, sodium polyepoxysuccinate, diphenyl ether gemini surfactant, nonylphenol polyoxyethylene ether, tannin, sodium polyacrylate, carboxymethyl cellulose, ammonium chloride and sodium nitrate are added. The shear cycle speed is 1000r / min, and the mixing reaction is carried out for 60 minutes to allow each component to fully react and be evenly mixed, so as to obtain the integrated fracturing fluid system of plugging removal, scale inhibition and energy enhancement.

[0049] Performance Test:

[0050] The following tests are carried out according to the standard method of SY / T 7627-2021 Technical requirements for water-based fracturing fluids:

[0051] Drag reduction rate 0.05% viscosity 2-5mPa·s: Example 1 (79.4%), Example 3 (76.1%), Example 2 (73.8%);

[0052] Viscosity-temperature curve: (Example 2) 0.4%-100°C, (Example 1) 0.7%-150°C, (Example 3) 1%-180°C;

[0053] Gas production of fracturing fluid at 50°C: Example 1 (50ml, 150ml), Example 2 (61ml, 183ml), Example 3 (47ml, 171ml);

[0054] Deblocking capacity of debonding liquid: 50°C, 2mm calcium carbonate, (Example 2) 99.3%, (Example 1) 97.6%, (Example 3) 95.2%;

[0055] Scale inhibition rate: 50°C, calcium carbonate, (Example 2) 96.1%, (Example 1) 93.4%, (Example 3) 91.8%.

[0056]

[0057]

[0058] Comparative Example 1

[0059] The preparation of reference example 1 is different in that: a water-soluble polymer B is first prepared, which is different from the water-soluble polymer A, and the cis-13-docosahexaenoylamidopropyl dimethylhydroxypropyl betaine monomer is not added therein, and then used in the fracturing fluid.

[0060] Comparative Example 2

[0061] The preparation is similar to that of Example 1, except that: a water-soluble polymer C is first prepared, which is different from the water-soluble polymer A and does not contain a cross-linking agent, and is then used in the fracturing fluid.

[0062] Comparative Example 3

[0063] The preparation is similar to that of Example 1, except that: a water-soluble polymer C is first prepared, which is different from the water-soluble polymer A, and no plugging remover is added thereto, and then used in the fracturing fluid.

[0064] Comparative Example 4

[0065] The preparation is similar to that of Example 1, except that: a water-soluble polymer C is first prepared, which is different from the water-soluble polymer A, and the scale inhibitor is not added thereto, and then used in the fracturing fluid.

[0066] Comparative Example 5

[0067] The preparation is similar to that of Example 1, except that a water-soluble polymer C is first prepared, which is different from the water-soluble polymer A and does not contain an energizer, and is then used in the fracturing fluid.

[0068] The performance tests of Examples 1 to 5 are as follows:

[0069]

[0070] By comparing and analyzing the above tests of Examples 1 to 3 and Comparative Examples 1 to 3, it can be seen that the absence of the above components will lead to a significant reduction in the corresponding functional effects of the fracturing fluid system, especially the absence of cis-13-docosapentaenoylpropyldimethylhydroxypropyl betaine monomer, which will seriously reduce the viscosity increasing and drag reducing effects of the fracturing fluid system.

[0071] Therefore, it can be seen from the above implementation that:

[0072] 1) The integrated fracturing fluid system for unblocking, scale prevention and energy enhancement provided by the present invention is suitable for 180°C high-temperature reservoir fracturing, and can solve the scaling of high-mineralization mixing water during volume fracturing, the strong velocity sensitivity of clay particle migration in the transformed reservoir, the low formation pressure coefficient, the presence of oil and gas in the well but no production after fracturing, etc. It has the characteristics of unblocking, scale prevention, waterproof lock, and the integration of slippery water and sand-carrying fluid for simple construction, easy backflow, and little damage to water-sensitive reservoirs;

[0073] 2) The integrated fracturing fluid system for plugging removal, scale inhibition and energy enhancement provided by the present invention can achieve adjustable viscosity within the range of 1 to 200 mPa·s, temperature resistance of 180°C, drag reduction rate of 80%; scale removal rate at 50°C, carbonate scale below 5mm, and scale removal rate of more than 95%; scale inhibition rate at 50°C, calcium carbonate ≥90%, calcium sulfate ≥90%, and barium sulfate ≥70% respectively;

[0074] 3) In general, compared with the prior art, the integrated fracturing fluid system for unblocking, scale inhibition and energy enhancement provided by the present invention has both unblocking and scale inhibition functions, and can be applied to fracturing of reservoirs with low formation pressure coefficients. This innovative achievement effectively solves on-site technical problems, and the preparation method is simple, easy to operate, and has low cost, and has good economic promotion value.

[0075] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A water-soluble high molecular polymer, It is characterized in that The method is as follows: acrylamide, sodium acrylate, sodium 2-acrylamido-2-methylpropane sulfonate and cis-13-docosapentaenoyl propyl dimethyl hydroxypropyl betaine are selected, and the four monomers are copolymerized under the action of an initiator to form a water-soluble high molecular polymer with a molecular weight of 3 to 30 million.

2. The water-soluble high molecular polymer according to claim 1, Features: The molar ratio of acrylamide, sodium acrylate, sodium 2-acrylamido-2-methylpropane sulfonate and cis-13-docosapentaenoylamidopropyl dimethylhydroxypropyl betaine is: (10-50): (5-50): (5-50): (0.1-10); The initiator is selected from ammonium persulfate and sodium bisulfite, and the weight ratio of the initiator to the copolymer reaction monomer is (0.001-1%):1; The temperature of the copolymerization reaction is 5-50°C; The copolymerization reaction time is 4-24h.

3. An integrated fracturing fluid system for plugging removal, scale prevention and energy enhancement, It is characterized in that The invention comprises the following components by weight percentage: 20-30% of the water-soluble high molecular polymer according to claim 1 or 2, 20-40% of the non-polar solvent, 0.01-5% of the cross-linking agent, 0.5-5% of the suspending agent, 0.5-5% of the emulsifier, 0.5-10% of the unblocking agent, 0.5-10% of the scale inhibitor, and 1-20% of the energy enhancer.

4. The integrated fracturing fluid system for removing blockage, preventing scale and enhancing energy according to claim 3, Features: The non-polar solvent is selected from one, two or three of white oil, solvent oil and xylene, and the weight ratio of the three is (5-10):(2-5):(2-5); The cross-linking agent is a water-soluble phenolic resin or an organic zirconium or a mixture of the two; The suspending agent is modified diatomaceous earth or hydrophilic nano silicon dioxide or a mixture of the two.

5. The integrated fracturing fluid system for removing blockage, preventing scale and enhancing energy according to claim 3, Features: The emulsifier is selected from one or more of sorbitan fatty acid esters, polyoxyethylene sorbitan fatty acid esters, alkylphenol polyoxyethylene ethers or alkanolamides.

6. The integrated fracturing fluid system for removing blockage, preventing scale and enhancing energy according to claim 3, Features: The blocking agent is selected from one or more of oxalic acid, citric acid, aminosulfonic acid, sodium ethylenediaminetetramethyl phosphate, sodium polyepoxysuccinate, sodium gluconate, ethylenediaminetetraacetic acid, sodium acetate, sodium hydroxyacetate, sorbitan fatty acid ester, diethylene glycol laurate, diphenyl ether gemini surfactant, nonylphenol polyoxyethylene ether or alkyl gluconic anhydride.

7. The integrated fracturing fluid system for removing blockage, preventing scale and enhancing energy according to claim 3, Features: The scale inhibitor is selected from one or more of tannin, carboxymethyl cellulose, sodium polyacrylate, hydrolyzed maleic anhydride, maleic acid-acrylic acid copolymer, acrylic acid-methacrylate copolymer, acrylic acid-methacrylic acid sulfonic acid copolymer or acrylic acid-methacrylate-hydroxyalkyl acrylate copolymer.

8. The integrated fracturing fluid system for removing blockage, preventing scale and enhancing energy according to claim 3, Features: The energizer is a mixture of ammonium chloride and sodium nitrate, and the mixing ratio of the two is 1:(1-10).

9. A method for preparing the integrated fracturing fluid system for removing blockage, preventing scale and enhancing energy according to any one of claims 3 to 8, It is characterized in that The following steps are involved: 1) According to the amount of the formula, the non-polar solvent, cross-linking agent, emulsifier and suspending agent are added to the reaction kettle respectively, and the stirring is turned on and the mixture is uniformly sheared by a variable frequency emulsification pump; the stirring speed for uniform mixing is 2000-3000 r / min, and the stirring time is 0.5-2h; 2) adding a water-soluble high molecular polymer to the mixture obtained in step 1), and mixing the mixture uniformly by circulating shearing with a variable frequency emulsifying pump; the stirring speed for the uniform mixing is 2000-3000 r / min, and the stirring time is 0.5-2h; 3) Adding a plugging remover, a scale inhibitor, and an energizer to the mixture obtained in step 2), and mixing them evenly by circulating shearing with a variable frequency emulsifier pump, thereby obtaining the plugging remover, scale inhibitor, and energizer integrated fracturing fluid system; the stirring speed for the even mixing is 500-2000 r / min, and the stirring time is 0.5-1h.

10. An application of the integrated fracturing fluid system for removing blockage, preventing scale and enhancing energy according to any one of claims 3 to 8, Features: The fracturing fluid is used as a fracturing fluid for developing oil and gas reservoirs of low or ultra-low permeability oil and gas reservoirs. The dosage of the fracturing fluid is 0.01%-1% of the total mass of the prepared liquid.

Images