Dialysis oil displacement fracturing fluid as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of oil and gas reservoir development and research, and discloses a dialysis oil displacement fracturing fluid as well as a preparation method and application thereof. The dialysis oil displacement fracturing fluid comprises the following components: water, a resistance reducing agent, an oil gas displacer, a clay stabilizer, a cleanup additive, a demulsifier and a gel breaker. Based on the total weight of the dialysis oil displacement fracturing fluid, the content of the water is 98.7%-99.2%, the content of the resistance reducing agent is 0.2%-0.3%, the content of the oil gas displacing agent is 0.15%-0.25%, the content of the clay stabilizer is 0.25%-0.35%, the content of the cleanup additive is 0.05%-0.15%, the content of the demulsifier is 0.15%-0.35%, and the content of the gel breaker is 5-15 ppm. The method greatly improves the formation pressure coefficient, greatly reduces the water content of the output liquid, and improves the daily oil production in the test stage.

Description

Technical Field

[0001] The invention belongs to the technical field of oil and gas reservoir development research, and more specifically, relates to a dialysis oil-displacing fracturing fluid and a preparation method and application thereof. Background Art

[0002] The exploration and development of low-pressure tight oil reservoirs is difficult, and it is difficult to achieve high and stable production during the self-flowing stage of oil wells. New technologies and new ideas are needed to conduct field tests and achieve breakthroughs.

[0003] Well Fulu 101 (sidetrack horizontal well) is a typical low-pressure tight oil reservoir in the Sichuan Basin. The tight sandstone reservoir of the second section of the Lianggaoshan Formation in this area belongs to condensate oil and gas reservoir. The measured original formation pressure coefficient is only 0.74, which belongs to a low-pressure system. The oil well can hardly achieve high and stable production during the self-flowing stage. Three vertical wells were tested in the same layer in this area, and the daily gas production was 5129m 3 / d, 416m 3 / d, 960m 3 / d, and the daily condensate production is 0.75m 3 / d, only oil spots, 4.09m 3 / d; In the same area, horizontal wells such as Zhong 1 Well were tested, but none of them had any return flow from their outlets, making it impossible to produce.

[0004] At present, the fracturing fluid preparation scheme in this area still adopts the conventional shale gas design idea: resistance reducing agent + anti-swelling agent + drainage agent. It has been applied in many wells such as the adjacent well Zhong 1 well, but the gas test effect is poor and production cannot be carried out. Through demonstration, the main problems are as follows:

[0005] (1) The original formation pressure coefficient in this area is only 0.74, and the production gas-oil ratio is very low, only 70-158m 3 / t, the wellbore is difficult to lift, unable to carry fluid to increase production, and unable to reach the conditions for self-flowing production. The fracturing fluid entering the well needs to complete the sand carrying function while also playing the role of increasing formation energy storage and percolation and oil displacement;

[0006] (2) The three-phase seepage environment of oil, gas and carbon in condensate oil and gas reservoirs is relatively complex. Conventional fracturing fluids are prone to emulsification and water lock, which can seriously reduce production or even lead to failure.

[0007] (3) Multi-stage fracturing of horizontal wells, with a large total amount of fluid entering the well, usually 30,000 m 3 The above mentioned, however, low-pressure reservoirs are difficult to flow back, with a flowback rate of only 3-5% in general, and the water content of the produced fluid is around 90% for a long time, making it a difficult task to obtain a higher daily oil production.

[0008] Therefore, it is urgent to propose a new dialysis oil-flooding fracturing fluid and a preparation method and apply it in low-pressure tight oil reservoirs. Summary of the invention

[0009] The purpose of the present invention is to address the deficiencies of the prior art and to propose a dialysis oil-displacing fracturing fluid and its preparation method and application. The present invention greatly increases the formation pressure coefficient, greatly reduces the water content of the output fluid, and increases the daily oil production in the test phase.

[0010] In order to achieve the above-mentioned purpose, the first aspect of the present invention provides a dialysis oil-flooding fracturing fluid, which comprises the following components: water, a drag reducing agent, an oil-gas displacement agent, a clay stabilizer, a drainage agent, a demulsifier and a gel breaker; based on the total weight of the dialysis oil-flooding fracturing fluid, the water content is 98.7%-99.2%, the drag reducing agent content is 0.2%-0.3%, the oil-gas displacement agent content is 0.15%-0.25%, the clay stabilizer content is 0.25%-0.35%, the drainage agent content is 0.05%-0.15%, the demulsifier content is 0.15%-0.35% and the gel breaker content is 5-15ppm.

[0011] According to the present invention, preferably, the polymer molecular weight of the drag reducing agent is above 15 million, and the salt tolerance reaches a mineralization degree of 10×10 4 ppm-30×10 4 ppm, heat and shear resistance (test conditions include: 0.5% drag reducer, 90℃, 60min, 170S -1 )≥60mPa.s, cross-linked heat and shear resistance (test conditions include: 0.5% drag reducing agent + 0.5% cross-linking agent (cross-linking agent used for testing cross-linked heat and shear resistance known to those skilled in the art), 90℃, 60min, 170S -1 )≥150mPa.s, drag reduction performance ≥80%, and residue content is less than 100ppm.

[0012] According to the present invention, preferably, the method for preparing the drag reducing agent comprises:

[0013] acrylamide monomer, sulfonate monomer, catalyst and surfactant are polymerized under liquid nitrogen insulation conditions to obtain a colloid;

[0014] Cutting, drying and granulating the colloid to obtain polymer powder;

[0015] The polymer powder, solvent, suspending agent and emulsifier are mixed, stirred and sheared uniformly to obtain the drag reducing agent.

[0016] In the present invention, the process of "mixing and stirring the polymer powder, solvent, suspending agent and emulsifier to uniformly mix" includes: adding the suspending agent to the solvent to stir, dissolve and mix, then adding the emulsifier as the oil phase, and after high-speed shearing and emulsification to uniformly mix, slowly adding the polymer powder, shearing and stirring to form a uniform suspension emulsion, i.e., the drag reducing agent.

[0017] According to the present invention, preferably, based on the total weight of the drag reducing agent, the content of the acrylamide monomer is 40.0%-60.0%, the content of the sulfonate monomer is 10.0%-40.0%, the content of the catalyst is 0.10%-0.25%, the content of the surfactant is 3.0%-4.0%, the content of the solvent is 10.0%-23.0%, the content of the suspending agent is 2.0%-3.0%, and the content of the emulsifier is 2.0%-3.0%.

[0018] According to the present invention, preferably, the solvent is at least one of white oil, alcohol and diesel.

[0019] According to the present invention, preferably, the suspending agent is sodium-based bentonite and / or calcium-based bentonite.

[0020] According to the present invention, preferably, the catalyst is acrylonitrile and / or sodium persulfate.

[0021] According to the present invention, preferably, the surfactant and the emulsifier are each independently OP and / or SPAN.

[0022] In the present invention, the role of the surfactant is to perform surface hydrophilic treatment, increase the water solubility rate of the polymer obtained by the polymerization reaction, so that the polymer reaches more than 95% of the viscosity of the drag reducing agent within 20 seconds, and at the same time, the maximum salt tolerance of the polymer can reach a mineralization degree of 10×10 4 ppm, the viscosity remains above 60% of that in clean water, even at a mineralization of 30×10 4 It can also be dissolved well in ppm salt water.

[0023] According to the present invention, preferably, the reaction temperature of the polymerization reaction is 5°C-15°C.

[0024] According to the present invention, preferably, the cutting adopts a spiral cutting technology to cut the colloid into small pieces; and the equipment used for drying is a fluidized drying equipment.

[0025] According to the present invention, preferably, the particle size of the polymer powder is 80-120 mesh.

[0026] According to the present invention, preferably, the oil-gas displacing agent is octanoate and / or organosilicon.

[0027] According to the present invention, preferably, the clay stabilizer is benzyltrimethylammonium chloride and / or choline chloride.

[0028] According to the present invention, preferably, the drainage aid is a lauryl alcohol polyoxyethylene ether drainage aid.

[0029] According to the present invention, preferably, the demulsifier is a polyether demulsifier.

[0030] According to the present invention, preferably, the gel breaker is at least one of ammonium persulfate, sodium persulfate and their respective encapsulated forms.

[0031] The second aspect of the present invention provides a method for preparing the dialysis oil displacement fracturing fluid, the preparation method comprising: mixing and stirring the water, drag reducing agent, oil and gas displacement agent, clay stabilizer, drainage agent, demulsifier and gel breaker to obtain the dialysis oil displacement fracturing fluid.

[0032] The third aspect of the present invention provides the use of the dialysis oil-flooding fracturing fluid in low-pressure tight oil reservoirs.

[0033] According to the present invention, preferably, the original formation pressure coefficient of the low-pressure tight oil reservoir is 0.70-1.00.

[0034] According to the present invention, preferably, the sand-to-liquid ratio of the dialysis oil displacement fracturing fluid in the sand-added fracturing construction is (10-40):100.

[0035] According to the present invention, preferably, the well shut-in time for the sand fracturing construction of the dialysis oil displacement fracturing fluid is 60-80 days.

[0036] The beneficial effects of the technical solution of the present invention are as follows:

[0037] 1. The present invention prepares a drag reducing agent of a strong suspension emulsion polymer, and mixes it with additives such as demulsifiers, oil and gas displacement agents, and drainage aids to form an imbibition oil-displacing fracturing fluid, and then combines supporting measures such as optimized well-keeping time to give play to the imbibition oil-displacing effect of the fracturing fluid, greatly improve the formation pressure coefficient, greatly improve the formation energy, greatly reduce the water content of the output fluid, and increase the daily oil production in the test phase. The core of the present invention is to form a complete set of fracturing processes for low-pressure tight oil reservoirs, which has been successfully practiced on site and has been proven to have good promotion prospects.

[0038] 2. The dialysis oil displacement fracturing fluid of the present invention is heated to 170S at 25°C. -1 After shearing, the viscosity drops from 23.8mPa.s to 20.8mPa.s, and it has good rheological properties.

[0039] 3. When the demulsifier content of the dialysis oil-flooding fracturing fluid of the present invention is 0.3%, the demulsification time is 60 min and 120 min, and the demulsification rate reaches 100%.

[0040] 4. The dialysis oil-displacing fracturing fluid of the present invention can significantly reduce interfacial tension and significantly improve the wetting properties of natural rocks, namely:

[0041] The dialysis oil displacement fracturing fluid of the present invention can reduce the interfacial tension to 1.18-1.3 mN / m;

[0042] The rock wettability experiment of the dialysis oil-flooding fracturing fluid described in the present invention was carried out using the natural core of the pilot well of Fulu 101 Well. The results showed that the contact angles of the original natural rocks in the well were 65.7° and 66.4°, which were determined to be hydrophilic. After being immersed in the dialysis oil-flooding fracturing fluid described in the present invention for 24 hours, the contact angles were changed to 53° and 55°, and the hydrophilicity was significantly enhanced, indicating that the dialysis oil-flooding fracturing fluid described in the present invention has the function of changing the wettability of rocks.

[0043] 5. After the production of Fulu 101 well (side-drilling horizontal well) was completed using the dialysis oil-displacing fracturing fluid of the present invention, the measured formation pressure coefficient increased from 0.74 to 0.86.

[0044] 6. After using the dialysis oil displacement fracturing fluid of the present invention in a horizontal well in the tight sandstone reservoir area of ​​the second section of the Lianggaoshan Formation, the daily gas production of the horizontal well was 4257m 3 / d, daily condensate oil production 26.88m 3 / d, the production has been greatly improved, which has realized the effective development of low-pressure condensate oil and gas reservoirs and ensured the future profitable development of the blocks.

[0045] Other features and advantages of the present invention will be described in detail in the following detailed description. DETAILED DESCRIPTION

[0046] The preferred embodiments of the present invention will be described in more detail below. Although the preferred embodiments of the present invention are described below, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided to make the present invention more thorough and complete, and to fully convey the scope of the present invention to those skilled in the art.

[0047] Example 1

[0048] The present embodiment provides a dialysis oil recovery fracturing fluid. Based on the total weight of the dialysis oil recovery fracturing fluid, the water content is about 98.9%, the drag reducing agent content is 0.3%, the oil and gas replacement agent silicone content is 0.2%, the clay stabilizer benzyltrimethylammonium chloride content is 0.3%, the lauryl alcohol polyoxyethylene ether drainage aid content is 0.1%, the polyether demulsifier content is 0.2% and the gel breaker ammonium persulfate content is 10ppm.

[0049] in:

[0050] The polymer molecular weight of the drag reducing agent is above 15 million, and the salt tolerance reaches a mineralization degree of 10×10 4 ppm-30×10 4 ppm, heat and shear resistance ≥ 60mPa.s, cross-linking heat and shear resistance ≥ 150mPa.s, drag reduction ≥ 80%, residue content is less than 100ppm;

[0051] The preparation method of the drag reducing agent comprises:

[0052] acrylamide monomer, sulfonate monomer, catalyst and surfactant are subjected to polymerization reaction under liquid nitrogen insulation conditions (the reaction temperature of the polymerization reaction is 5° C.-15° C.) to obtain a colloid;

[0053] The colloid is cut by spiral cutting technology, dried by fluidized drying equipment and granulated to obtain a polymer powder with a particle size of 80-120 mesh;

[0054] The polymer powder, solvent, suspending agent and emulsifier are mixed and stirred uniformly to obtain the drag reducing agent.

[0055] Based on the total weight of the drag reducing agent, the content of the acrylamide monomer is 55%, the content of the sulfonate monomer is 25%, the content of the catalyst is 0.20%, the content of the surfactant is 3.5%, the content of the solvent is 11.3%, the content of the suspending agent is 2.5%, and the content of the emulsifier is 2.5%.

[0056] The solvent is white oil; the suspending agent is sodium bentonite; the catalyst is acrylonitrile; the surfactant is OP; and the emulsifier is OP.

[0057] The preparation method of the above-mentioned dialysis oil displacement fracturing fluid comprises: mixing and stirring the water, drag reducing agent, oil-gas replacement agent, clay stabilizer, drainage agent, demulsifier and gel breaker uniformly to obtain the dialysis oil displacement fracturing fluid.

[0058] The above-mentioned dialysis oil displacement fracturing fluid was applied to the fracturing construction of Fulu 101 well (sidetrack horizontal well), and the fracturing construction parameters were:

[0059] Completed 13-stage sand fracturing in the whole well, with a total net fluid volume of 22925.59m3 3 The average liquid consumption per stage is 1706.91m 3 ; Total amount of sand added: 3307.97m 3 , average single section 254.46m 3 The average sand ratio is 19.29%, and the average comprehensive sand-liquid ratio is 15.91%. The average liquid strength is 34.0m 3 / m; average sand adding strength 7.3t / m.

[0060] The wellhead pressure of Fulu 101 (lateral drilling horizontal well) was 25 days after well shut-in. After 25 days, the production was tested: the production was measured by a Φ10.00mm nozzle and a Φ20.00mm gasket flowmeter. The wellhead pressure was 0.96-1.06MPa, and the daily natural gas production was 0.2527×10 4 m 3 / d, daily water output 21.36m 3 / d, daily oil production 17.28m 3 / d.

[0061] Example 2

[0062] In this embodiment, the dialysis oil displacement fracturing fluid of embodiment 1 is applied to the fracturing construction of Fulu 101 well (sidetrack horizontal well). The difference between this embodiment and embodiment 1 is only that:

[0063] The wellhead pressure of Fulu 101 (lateral drilling horizontal well) was 2.17-2.00 MPa, and the daily natural gas production was 0.4257×10 4 m 3 / d, daily water output 6.24m 3 / d, daily oil production 26.88m 3 / d.

[0064] The embodiments of the present invention have been described above, and the above description is exemplary, not exhaustive, and is not limited to the disclosed embodiments. Many modifications and changes will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments.

Claims

1. A dialysis oil displacement fracturing fluid, characterized in that: The dialysis oil displacement fracturing fluid comprises the following components: water, a drag reducing agent, an oil-gas displacement agent, a clay stabilizer, a drainage aid, a demulsifier and a gel breaker; based on the total weight of the dialysis oil displacement fracturing fluid, the content of water is 98.7%-99.2%, the content of the drag reducing agent is 0.2%-0.3%, the content of the oil-gas displacement agent is 0.15%-0.25%, the content of the clay stabilizer is 0.25%-0.35%, the content of the drainage aid is 0.05%-0.15%, the content of the demulsifier is 0.15%-0.35% and the content of the gel breaker is 5-15ppm.

2. The dialysis oil displacement fracturing fluid according to claim 1, wherein: The polymer molecular weight of the drag reducing agent is above 15 million, and the salt tolerance reaches a mineralization degree of 10×10 4 ppm-30×10 4 ppm, heat and shear resistance ≥60mPa.s, cross-linking heat and shear resistance ≥150mPa.s, drag reduction performance ≥80%, residue content is less than 100ppm.

3. The dialysis oil displacement fracturing fluid according to claim 2, wherein: The preparation method of the drag reducing agent comprises: acrylamide monomer, sulfonate monomer, catalyst and surfactant are polymerized under liquid nitrogen insulation conditions to obtain a colloid; Cutting, drying and granulating the colloid to obtain polymer powder; The polymer powder, solvent, suspending agent and emulsifier are mixed, stirred and sheared uniformly to obtain the drag reducing agent.

4. The dialysis oil displacement fracturing fluid according to claim 3, wherein: Based on the total weight of the drag reducing agent, the content of the acrylamide monomer is 40.0%-60.0%, the content of the sulfonate monomer is 10.0%-40.0%, the content of the catalyst is 0.10%-0.25%, the content of the surfactant is 3.0%-4.0%, the content of the solvent is 10.0%-23.0%, the content of the suspending agent is 2.0%-3.0%, and the content of the emulsifier is 2.0%-3.0%.

5. The dialysis oil displacement fracturing fluid according to claim 3, wherein: The solvent is at least one of white oil, alcohol and diesel; The suspending agent is sodium bentonite and / or calcium bentonite; The catalyst is acrylonitrile and / or sodium persulfate; The surfactant and emulsifier are each independently OP and / or SPAN.

6. The dialysis oil displacement fracturing fluid according to claim 3, wherein: The reaction temperature of the polymerization reaction is 5°C-15°C; The cutting adopts spiral cutting technology; The equipment used for drying is a fluidized drying equipment; The particle size of the polymer powder is 80-120 meshes.

7. The dialysis oil displacement fracturing fluid according to claim 1, wherein: The oil-gas replacement agent is octanoate and / or organosilicon; The clay stabilizer is benzyltrimethylammonium chloride and / or choline chloride; The drainage aid is a lauryl alcohol polyoxyethylene ether drainage aid; The demulsifier is a polyether demulsifier; The breaker is at least one of ammonium persulfate, sodium persulfate and their respective encapsulated capsules.

8. The method for preparing the dialysis oil displacement fracturing fluid according to any one of claims 1 to 7, characterized in that: The preparation method comprises: mixing and stirring the water, the drag reducing agent, the oil-gas replacement agent, the clay stabilizer, the drainage aid, the demulsifier and the gel breaker evenly to obtain the dialysis oil displacement fracturing fluid.

9. Use of the dialysis oil displacement fracturing fluid according to any one of claims 1 to 7 in low-pressure tight oil reservoirs.

10. The use according to claim 9, wherein: The original formation pressure coefficient of the low-pressure tight oil reservoir is 0.70-1.00; The sand-to-liquid ratio of the dialysis oil displacement fracturing fluid for sand fracturing construction is (10-40):100; The well shut-down time of the sand-added fracturing construction of the dialysis oil-flooding fracturing fluid is 60-80 days.