Recyclable quasi-interpenetrating network foam fracturing fluid and preparation method thereof
By developing a recyclable interpenetrating network foam fracturing fluid composed of multi-effect agents, thickening additives, clay stabilizers, iron ion stabilizers and modified nanocellulose reinforcers, the problems of poor temperature, formation damage, and large construction costs of the existing CO2 foam fracturing fluid are solved, and multiple recycling and reuse of liquids are achieved, reducing costs and environmental risks.
Patent Information
- Application Number
- CN202411617829.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-11-13
- Publication Date
- 2025-02-25
AI Technical Summary
The existing CO2 foam fracturing fluid has problems such as poor foam temperature, great damage to the formation, high construction costs, high costs and potential environmental risks.
A recyclable interpenetrating network foam fracturing liquid is provided, which consists of a multi-effect agent, a thickening additive, a clay stabilizer, an iron ion stabilizer and a modified nanocellulose reinforcer, and multiple recovery and reuse of the liquid is achieved through specific preparation methods and process flows.
This foam fracturing fluid not only has excellent fracturing performance, but can also be reused, reducing construction costs, reducing damage to the formation, and reducing the risk of environmental pollution.
Smart Images
Figure CN119505859A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to the technical field of petroleum exploitation and fracturing, in particular to a recyclable pseudo-interpenetrating network foam fracturing fluid and a preparation method thereof. Background Art
[0002] Excessive carbon dioxide emissions are one of the main causes of the greenhouse effect, which can lead to a series of environmental problems, such as melting glaciers, rising sea levels, desertification and global warming. Therefore, it is necessary to reduce CO2 emissions and reduce the content of CO2 in the atmosphere. Carbon capture and storage (CCS) technology has become an important method to mitigate the greenhouse effect. However, the cost of CCS is very high, mainly due to the CO2 capture process, which limits the application of this technology. Carbon dioxide utilization can greatly reduce the economic burden of CCS and effectively reduce CO2 emissions. CO2 foam fracturing is a solution that can achieve CO2 utilization and can store CO2 in the formation.
[0003] CO2 foam fracturing fluid has the characteristics of easy backflow, low filtration loss, and strong sand carrying capacity. However, foam is a thermodynamic metastable system and tends to decay over time. Therefore, cross-linked polymer gel is often added as a foam stabilizing substance. However, there are residues after the cross-linked polymer gel is broken, which damages the formation and the conductivity of the supporting fractures, seriously affecting the fracturing transformation effect. Polymer-free viscoelastic surfactant (VES) fracturing fluid has been a hot topic of research at home and abroad in the past decade due to its dynamically reversible three-dimensional network structure. VES fracturing fluid has the rheological properties of cleanliness, no residue, low damage, low viscosity and high elasticity, simple on-site preparation, and no need for other chemical additives such as cross-linking agents. However, the high cost of viscoelastic surfactants and potential environmental risks are the defects of VES-CO2 foam fracturing fluid, which seriously restricts its application. Therefore, the existing CO2 foam fracturing still has problems such as poor foam temperature resistance, great damage to the formation, and high construction cost. Summary of the invention
[0004] In view of the above problems existing in the current CO2 foam fracturing fluid, the present invention provides a recyclable pseudo-interpenetrating network foam fracturing fluid, which not only has excellent fracturing performance but can also be reused to reduce construction costs.
[0005] The recyclable pseudo-interpenetrating network foam fracturing fluid provided by the present invention comprises the following components in percentage by mass:
[0006] Multi-effect agent 2-4%, thickening aid 0.1-2%, clay stabilizer 1-2%, iron ion stabilizer 0.5-2.5%, strengthener 0.05-0.5%, and the balance is water.
[0007] The multi-effect agent is selected from one or more of cocoamidopropyl dimethylamine, oleamidopropyl dimethylamine, fatty amide propyl dimethylamine, and erucic acid amide propyl dimethylamine.
[0008] The preparation method of the reinforcing agent is as follows:
[0009] (1) dispersing nanocellulose in a sodium hydroxide aqueous solution by ultrasonication and mechanically stirring for 2-3 h for alkalization;
[0010] (2) filtering to remove undissolved solids, then adding 2-(chloromethyl)ethylene oxide to the solution, and stirring at 60-70° C. for 5-6 hours to prepare an intermediate;
[0011] (3) Add N-methyl-1,2-ethylenediamine and solvent isopropanol to the intermediate, and stir at 75-85° C. for 2-4 hours to obtain a strengthener.
[0012] The thickening aid is selected from a mixture of one or more of sodium p-benzenesulfonate, sodium salicylate, sodium p-vinylbenzenesulfonate and sodium benzenesulfonate.
[0013] The clay stabilizer is potassium chloride.
[0014] The iron ion stabilizer is aminotri(methylenephosphonic acid) or sodium ethylenediaminetetraacetate or a mixture of the two.
[0015] The method for preparing the recyclable pseudo-interpenetrating network foam fracturing fluid comprises the following steps:
[0016] S1. Add thickening agent, clay stabilizer, iron ion stabilizer and fortifier into water and stir until completely dissolved, then add multi-effect agent and stir for several minutes to form an emulsion;
[0017] S2. Introduce stimulating gas CO2 into the emulsion, the emulsion gradually becomes clear and transparent, and the viscosity increases, forming a foam fracturing fluid base liquid; continue to introduce CO2 into the foam fracturing fluid base liquid to form a foam fracturing fluid.
[0018] S3, introducing methane gas into the foam fracturing fluid to defoam the foam fracturing fluid and obtain an emulsion again;
[0019] S4, repeating steps S2 and S3 with the newly obtained emulsion to achieve multiple recycling of the foam fracturing fluid.
[0020] The foam fracturing fluid provided by the present invention can also realize the performance test of the foam fracturing fluid reservoir conditions, and the method is as follows:
[0021] (1) Add thickening agent, clay stabilizer, iron ion stabilizer and fortifier into water and stir until completely dissolved, then add multi-effect agent and stir for 5 minutes to form an emulsion;
[0022] (2) The emulsion is transferred to a visualized high-temperature and high-pressure reactor, the air inlet valve and the vent valve are opened, and the stimulating gas CO2 is introduced into the visualized high-temperature and high-pressure reactor at a rate of 2-3 L / min. During the introduction process, the emulsion is stirred by the stirring motor provided in the visualized high-temperature and high-pressure reactor, and the stirring speed is 100-200 rpm. During the introduction of the stimulating gas, the emulsion gradually becomes clear and transparent, and the viscosity increases, forming a foam fracturing fluid base liquid.
[0023] (3) Close the vent valve, turn on the heating switch, and after the temperature of the visualized high temperature and high pressure reactor reaches the simulated temperature, continue to introduce the stimulating gas CO2 so that the pressure of the visualized high temperature and high pressure reactor reaches the simulated pressure, then adjust the stirring speed to 2000 rpm, stir for 3-5 minutes, and the foam fracturing fluid can be formed; then the performance of the foam fracturing fluid is tested. The simulated temperature is 60-150°C, and the simulated pressure is 5-50MPa.
[0024] (4) After the fracturing fluid is used up, the foam fracturing fluid can be recovered by introducing methane gas into the foam fracturing fluid at a rate of 0.1-0.8 L / min to simulate the interference of methane on the foam fracturing fluid in the reservoir, and methane gradually replaces the irritating gas in the visualized high-temperature and high-pressure reactor, defoaming the foam fracturing fluid, and re-obtaining the emulsion.
[0025] (5) Repeating steps (2) to (4) can realize multiple recycling and reuse of the foam fracturing fluid.
[0026] Compared with the prior art, the present invention is beneficial in that:
[0027] (1) The multi-effect agent used in the foam fracturing fluid of the present invention has three functions; first, the multi-effect agent has a surfactant after protonation, and can be used as a foaming agent in the foam fracturing fluid, effectively adsorbed on the gas-liquid interface, reducing the surface tension of the fracturing fluid base fluid, and forming a high-quality foam fracturing fluid; second, in addition to being adsorbed on the interface, the protonated multi-effect agent can also form worm-like micelles in the solution, greatly improving the stability of the foam fracturing fluid; third, after the fracturing construction is completed, since the multi-effect agent still has a certain surfactant, it can be used as a drainage agent in the fracturing fluid to improve the backflow capacity of the fracturing fluid. One agent has multiple uses, replacing the foaming agent, foam stabilizer and drainage agent of the conventional foam fracturing fluid, simplifying the difficulty and cost of liquid preparation.
[0028] (2) The enhancer used in the present invention is a modified nanocellulose with good dispersibility and temperature and salt resistance, and will not aggregate in the reservoir environment and lose its effect. If the unmodified original nanocellulose is directly added to the fracturing fluid, agglomeration will occur. The enhancer of the present invention has the dual functions of foam interface performance and enhanced liquid film performance. At the gas-liquid interface, the enhancer forms hydrogen bonds with the multi-effect agent. Under the influence of the hydrogen bonds, the enhancer closely links the multi-effect agent like a bridge, thereby increasing the adsorption strength of the multi-effect agent at the interface, and the foaming ability is further improved; in the liquid film, the worm-like micelle network formed by the enhancer and the multi-effect agent is intertwined to form a more complex pseudo-interpenetrating network structure, which greatly enhances the strength of the liquid film and further improves the stability of the foam.
[0029] (3) By introducing or removing the irritating gas CO2, the foam fracturing can be recycled and reused, which greatly reduces the fracturing cost, while reducing the emission of chemical substances such as surfactants and reducing the risk of environmental pollution. The irritating gas CO2 is non-toxic, cheap, non-flammable, and easy to obtain. At the same time, it realizes the full utilization of CO2 and seals CO2 in the formation.
[0030] (4) The recyclable pseudo-IPN foam fracturing fluid of the present invention can simulate the performance of the foam fracturing fluid under reservoir conditions, and is more in line with the actual working conditions of the foam fracturing fluid in the reservoir.
[0031] (5) The fracturing fluid of the present invention does not need to introduce a breaker. When the hydrocarbon substance in the formation destroys the micelle structure or is diluted by the formation water, the foam stability is significantly reduced, thereby achieving the purpose of breaking the gel. There is no residue after breaking the gel, and the damage to the reservoir is extremely low. It is very suitable for the production increase transformation of low permeability or ultra-low permeability reservoirs.
[0032] Other advantages, objectives and features of the present invention will be embodied in part through the following description, and in part will be understood by those skilled in the art through study and practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS
[0033] Figure 1 It is a schematic diagram of the CO2 response mechanism of the multi-effect agent in the present invention.
[0034] Figure 2 It is a schematic diagram of the mechanism by which the strengthening agent of the present invention strengthens the interfacial properties of foam.
[0035] Figure 3 It is a schematic diagram of the strengthening mechanism of the strengthening agent of the present invention on the liquid film.
[0036] Figure 4 It is the change in the viscosity of the foam base fluid after repeated introduction / removal of CO2 into / from the foam fracturing fluid of the present invention. DETAILED DESCRIPTION
[0037] The preferred embodiments of the present invention are described below in conjunction with the accompanying drawings. It should be understood that the preferred embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.
[0038] A method for preparing a strengthening agent:
[0039] (1) 10 g of nanocellulose was dispersed in 250 mL of a 20 wt % NaOH solution using ultrasound and then alkalized at 20° C. with magnetic stirring for 2 h.
[0040] (2) The undissolved solid portion was filtered off, and then 240 mL of 2-(chloromethyl)ethylene oxide was added to the solution, and stirred at 65° C. for 6 h to prepare an intermediate.
[0041] (3) Add 200 mL of a mixed solution of N-methyl-1,2-ethylenediamine and isopropanol to the intermediate in a mass ratio of 6:4, and stir at 80° C. for 3 hours to fully quaternize the mixture, thereby obtaining a reinforcing agent.
[0042] The synthetic route of the enhancer is as follows:
[0043]
[0044] The prepared enhancer was used to prepare foam fracturing fluid in the following Examples 1-6.
[0045] Example 1
[0046] A recyclable pseudo-interpenetrating network foam fracturing fluid, the preparation and performance test are as follows:
[0047] Step 1, weigh 2wt% of multi-effect agent, 0.1wt% of thickening aid, 1wt% of clay stabilizer, 0.5wt% of iron ion stabilizer, 0.05wt% of strengthener, and the balance is water;
[0048] Among them, the multi-effect agent is oleic acid amide propyl dimethylamine; the thickening aid is a mixture of sodium salicylate and sodium benzene sulfonate, and the mixing mass ratio is 1:1; the clay stabilizer is potassium chloride; the iron ion stabilizer is a mixture of aminotri(methylenephosphonic acid) and sodium ethylenediaminetetraacetate, and the mixing mass ratio is 2:1.
[0049] Step 2: Add thickening aid, clay stabilizer, iron ion stabilizer and enhancer into water, stir until completely dissolved, then add multi-effect agent and stir for 5 minutes to form an emulsion.
[0050] Step 3, transfer the emulsion to a visualized high-temperature and high-pressure reactor, open the air inlet valve and the vent valve, introduce the stimulating gas CO2 into the visualized high-temperature and high-pressure reactor at a rate of 2L / min, and stir the emulsion with the stirring motor of the visualized high-temperature and high-pressure reactor during the introduction process, the stirring speed is 100 rpm, and the emulsion gradually becomes clear and transparent and the viscosity increases during the introduction of the stimulating gas, forming a foam fracturing fluid base liquid; the viscosity of the base liquid is measured to be 118mPa·s. The visualized high-temperature and high-pressure reactor refers to a high-temperature and high-pressure reactor with a visual window, which can observe the fracturing fluid in the reactor from the outside, and the bottom of the reactor is equipped with a stirring device. Any reactor that meets the above requirements can be used.
[0051] Step 4, close the vent valve, turn on the heating device switch, and after the temperature of the visualized high temperature and high pressure reactor reaches the simulated temperature of 80°C, continue to introduce the stimulating gas CO2 so that the pressure of the visualized high temperature and high pressure reactor reaches the simulated pressure of 20MPa. Then adjust the stirring speed to 2000 rpm and stir for 3 minutes to form a foam fracturing fluid. It was measured that the CO2 foam fracturing fluid has a liquid separation half-life of 121 minutes under the conditions of 80°C and 20MPa, and the sedimentation rate of 40-70 mesh ceramsite proppant in the fracturing fluid is 0.56cm / min, which meets the requirements of fracturing construction.
[0052] Step 5: After the fracturing fluid is used up, the foam fracturing fluid can be recovered. Methane gas is introduced into the prepared foam fracturing fluid at a rate of 0.1 L / min to simulate the interference of methane on the foam fracturing fluid in the reservoir. Methane gradually replaces the irritating gas in the visualized high-temperature and high-pressure reactor, and the foam fracturing fluid is defoamed to obtain an emulsion again. The viscosity of the emulsion is measured to be 2.5 mPa·s.
[0053] Step 6: Repeat steps 3-5 to realize multiple recycling of the foam fracturing fluid, and the performance of the fracturing fluid remains good after repeating the process 5 times.
[0054] The same method as steps S1-S4 is used, except that the strengthening agent is not used, to obtain a foam fracturing fluid. The performance of the fracturing fluid under the conditions of 80°C and 20MPa is that the half-life of the liquid separation is 71min, and the sedimentation rate of the 40-70 mesh ceramsite proppant in the fracturing fluid is 1.45cm / min, which indicates the strengthening effect of the strengthening agent on the CO2 foam fracturing fluid.
[0055] The CO2 response mechanism of the multi-effect agent in the present invention is as follows Figure 1As shown, CO2 is introduced into the aqueous solution of the multi-effect agent, and the tertiary amine in the multi-effect agent combines with the proton in the carbonic acid to undergo a protonation reaction to form a tertiary amine cation. Due to the formation of tertiary amine cations, the multi-effect agent has surface activity. A part of the multi-effect agent is adsorbed on the interface to reduce the surface tension and improve the foaming ability of the foam fracturing fluid; the other part of the multi-effect agent self-polymerizes in the solution to form worm-like micelles, which entangle with each other to increase the viscoelasticity of the solution, thereby improving the stability of the foam. When the fracturing construction is completed, by removing CO2, the tertiary amine cation undergoes a deprotonation reaction, the surfactant of the multi-effect agent is lost, and the worm-like micelles dissociate, thereby restoring the original state, achieving the purpose of recovering the fracturing fluid.
[0056] The mechanism by which the reinforcing agent in the present invention strengthens the interfacial properties of the foam is as follows: Figure 2 As shown in the figure, at the gas-liquid interface, the reinforcing agent forms a hydrogen bond with the multi-effect agent. Under the influence of the hydrogen bond, the reinforcing agent closely links the multi-effect agent together like a bridge, thereby increasing the adsorption strength of the multi-effect agent at the interface and improving the foaming performance. In addition, nanocellulose has a large desorption energy. When nanocellulose is adsorbed on the gas-liquid interface, it is difficult to desorb from the interface. The irreversible adsorption characteristics of nanocellulose greatly improve the strength of the liquid film, and the sand carrying capacity of the foam fracturing fluid is also improved accordingly.
[0057] The strengthening mechanism of the strengthening agent on the liquid film in the present invention is as follows Figure 3 As shown, the enhancer has a certain flexibility and is intertwined with the worm-like micelles formed by the multifunctional agent to form a more complex interpenetrating network structure, which greatly improves the strength of the liquid film and the stability of the foam.
[0058] Example 2
[0059] A recyclable pseudo-interpenetrating network foam fracturing fluid, the preparation and performance test are as follows:
[0060] Step 1, weigh 2.5wt% of multi-effect agent, 1.8wt% of thickening aid, 1.5wt% of clay stabilizer, 2wt% of iron ion stabilizer, 0.3wt% of strengthener, and the balance is water;
[0061] Among them, the multi-effect agent is a mixture of cocamidopropyl dimethylamine, stearamidopropyl dimethylamine, and erucamidopropyl dimethylamine, with a mixing mass ratio of 2:1:1; the thickening aid is sodium salicylate; the clay stabilizer is potassium chloride; and the iron ion stabilizer is sodium ethylenediaminetetraacetic acid.
[0062] Step 2: Add thickening aid, clay stabilizer, iron ion stabilizer and enhancer into water, stir until completely dissolved, then add multi-effect agent and stir for 5 minutes to form an emulsion.
[0063] Step 3, transfer the emulsion to the visualized high-temperature and high-pressure reactor, open the air inlet valve and the vent valve, introduce the stimulating gas CO2 into the visualized high-temperature and high-pressure reactor at a rate of 2L / min, and use the stirring motor of the visualized high-temperature and high-pressure reactor to stir the emulsion during the introduction process. The stirring speed is 200 rpm. During the introduction of the stimulating gas, the emulsion gradually becomes clear and transparent, and the viscosity increases, forming a foam fracturing fluid base liquid; the viscosity of the base liquid is measured to be 358mPa·s.
[0064] Step 4, close the vent valve, turn on the heating switch, and after the temperature of the visualized high temperature and high pressure reactor reaches the simulated temperature of 150°C, continue to introduce the stimulating gas CO2 so that the pressure of the visualized high temperature and high pressure reactor reaches the simulated pressure of 50MPa. Then adjust the stirring speed to 2000 rpm and stir for 3 minutes to form a foam fracturing fluid. It was measured that the CO2 foam fracturing fluid has a liquid separation half-life of 146 minutes under the conditions of 150°C and 50MPa, and the sedimentation rate of 40-70 mesh ceramsite proppant in the fracturing fluid is 0.22cm / min, which meets the requirements of fracturing construction.
[0065] Step 5: After the fracturing fluid is used up, the foam fracturing fluid can be recovered. Methane gas is introduced into the prepared foam fracturing fluid at a rate of 0.8 L / min to simulate the interference of methane on the foam fracturing fluid in the reservoir. Methane gradually replaces the irritating gas in the visualized high-temperature and high-pressure reactor, and the foam fracturing fluid is defoamed to obtain an emulsion again. The viscosity of the emulsion is measured to be 3.3 mPa·s.
[0066] Step 6: Repeat steps 3-5 to realize multiple recycling of the foam fracturing fluid, and the performance of the fracturing fluid remains good after repeating the process 4 times. Figure 4 This is the change in viscosity of the foam fracturing fluid base fluid repeated 4 times.
[0067] The same method as steps S1-S4 is used, except that the intensifier is not used, to obtain a foam fracturing fluid. The performance of the fracturing fluid under the conditions of 150°C and 50MPa is that the liquid separation half-life is 80min, and the sedimentation rate of the 40-70 mesh ceramsite proppant in the fracturing fluid is 1.24cm / min, indicating the intensifying effect of the intensifier on the CO2 foam fracturing fluid.
[0068] Example 3
[0069] A recyclable pseudo-interpenetrating network foam fracturing fluid, the preparation and performance test are as follows:
[0070] Step 1, weigh 4wt% of multi-effect agent, 2wt% of thickening aid, 2wt% of clay stabilizer, 2.5wt% of iron ion stabilizer, 0.5wt% of strengthener, and the balance is water;
[0071] Among them, the multi-effect agent is oleic acid amide propyl dimethylamine; the thickening aid is a mixture of sodium p-vinylbenzene sulfonate and sodium p-benzene sulfonate, and the mixing mass ratio is 1:1; the clay stabilizer is potassium chloride; and the iron ion stabilizer is aminotri(methylenephosphonic acid).
[0072] Step 2: Add thickening aid, clay stabilizer, iron ion stabilizer and enhancer into water, stir until completely dissolved, then add multi-effect agent and stir for 5 minutes to form an emulsion.
[0073] Step 3, transfer the emulsion to the visualized high-temperature and high-pressure reactor, open the air inlet valve and the vent valve, introduce the stimulating gas CO2 into the visualized high-temperature and high-pressure reactor at a rate of 2.5L / min, and use the stirring motor of the visualized high-temperature and high-pressure reactor to stir the emulsion during the introduction process. The stirring speed is 150 rpm. During the introduction of the stimulating gas, the emulsion gradually becomes clear and transparent, and the viscosity increases, forming a foam fracturing fluid base liquid; the viscosity of the base liquid is measured to be 254mPa·s.
[0074] Step 4, close the vent valve, turn on the heating switch, and after the temperature of the visualized high temperature and high pressure reactor reaches the simulated temperature of 130°C, continue to introduce the stimulating gas CO2 so that the pressure of the visualized high temperature and high pressure reactor reaches the simulated pressure of 45MPa. Then adjust the stirring speed to 2000 rpm and stir for 3 minutes to form a foam fracturing fluid. It was measured that the CO2 foam fracturing fluid had a liquid separation half-life of 127 minutes under the conditions of 130°C and 45MPa, and the sedimentation rate of 40-70 mesh ceramsite proppant in the fracturing fluid was 0.19cm / min, which met the requirements of fracturing construction.
[0075] Step 5: After the fracturing fluid is used up, the foam fracturing fluid can be recovered. Methane gas is introduced into the prepared foam fracturing fluid at a rate of 0.8 L / min to simulate the interference of methane on the foam fracturing fluid in the reservoir. Methane gradually replaces the irritating gas in the visualized high-temperature and high-pressure reactor, and the foam fracturing fluid is defoamed to obtain an emulsion again. The viscosity of the emulsion is measured to be 2.8 mPa·s.
[0076] Step 6: Repeat steps 3-5 to realize multiple recycling of the foam fracturing fluid, and the performance of the fracturing fluid remains good after repeating the process 4 times.
[0077] The same method as steps S1-S4 is used, except that the intensifier is not used, to obtain a foam fracturing fluid. The performance of the fracturing fluid under the conditions of 130°C and 45MPa is that the liquid separation half-life is 69min, and the sedimentation rate of the 40-70 mesh ceramsite proppant in the fracturing fluid is 1.35cm / min, indicating the intensifying effect of the intensifier on the CO2 foam fracturing fluid.
[0078] Example 4
[0079] A recyclable pseudo-interpenetrating network foam fracturing fluid, the preparation and performance test are as follows:
[0080] Step 1, weigh 2.8wt% of multi-effect agent, 1.6wt% of thickening aid, 1.2wt% of clay stabilizer, 2.0wt% of iron ion stabilizer, 0.3wt% of strengthener, and the balance is water;
[0081] Among them, the multi-effect agent is oleamide propyl dimethylamine; the thickening aid is sodium salicylate; the clay stabilizer is potassium chloride; and the iron ion stabilizer is aminotri(methylene phosphonic acid).
[0082] Step 2: Add thickening aid, clay stabilizer, iron ion stabilizer and enhancer into water, stir until completely dissolved, then add multi-effect agent and stir for 5 minutes to form an emulsion.
[0083] Step 3, transfer the emulsion to the visualized high-temperature and high-pressure reactor, open the air inlet valve and the vent valve, introduce stimulating gas CO2 into the visualized high-temperature and high-pressure reactor at a rate of 2.2 L / min, and use the stirring motor of the visualized high-temperature and high-pressure reactor to stir the emulsion during the introduction process. The stirring speed is 150 rpm. During the introduction of the stimulating gas, the emulsion gradually becomes clear and transparent, and the viscosity increases, forming a foam fracturing fluid base liquid; the viscosity of the base liquid is measured to be 208 mPa·s.
[0084] Step 4, close the vent valve, turn on the heating switch, and after the temperature of the visualized high temperature and high pressure reactor reaches the simulated temperature of 100°C, continue to introduce the stimulating gas CO2 so that the pressure of the visualized high temperature and high pressure reactor reaches the simulated pressure of 35MPa. Then adjust the stirring speed to 2000 rpm and stir for 3 minutes to form a foam fracturing fluid. It was measured that the CO2 foam fracturing fluid had a liquid separation half-life of 155 minutes at 100°C and 35MPa, and the sedimentation rate of 40-70 mesh ceramsite proppant in the fracturing fluid was 0.15cm / min, which met the requirements of fracturing construction.
[0085] Step 5: After the fracturing fluid is used up, the foam fracturing fluid can be recovered. Methane gas is introduced into the prepared foam fracturing fluid at a rate of 0.6 L / min to simulate the interference of methane on the foam fracturing fluid in the reservoir. Methane gradually replaces the irritating gas in the visualized high-temperature and high-pressure reactor, and the foam fracturing fluid is defoamed to obtain an emulsion again. The viscosity of the emulsion is measured to be 2.9 mPa·s.
[0086] Step 6: Repeat steps 3-5 to realize multiple recycling of the foam fracturing fluid, and the performance of the fracturing fluid remains good after repeating the process 4 times.
[0087] The same method as steps S1-S4 is used, except that the enhancer is not used, to obtain a foam fracturing fluid. The performance of the fracturing fluid under the conditions of 100°C and 35MPa is that the liquid separation half-life is 81min, and the sedimentation rate of the 40-70 mesh ceramsite proppant in the fracturing fluid is 0.87cm / min, indicating the enhancing effect of the enhancer on the CO2 foam fracturing fluid.
[0088] Example 5
[0089] A recyclable pseudo-interpenetrating network foam fracturing fluid, the preparation and performance test are as follows:
[0090] Step 1, weigh 2.2wt% of multi-effect agent, 0.4wt% of thickening aid, 1.0wt% of clay stabilizer, 1.5wt% of iron ion stabilizer, 0.1wt% of strengthener, and the balance is water;
[0091] Among them, the multi-effect agent is a mixture of oleamidopropyl dimethylamine and erucic acid amidopropyl dimethylamine, with a mixing mass ratio of 3:2; the thickening aid is sodium p-toluenesulfonate; the clay stabilizer is potassium chloride; and the iron ion stabilizer is sodium ethylenediaminetetraacetate.
[0092] Step 2: Add thickening aid, clay stabilizer, iron ion stabilizer and enhancer into water, stir until completely dissolved, then add multi-effect agent and stir for 5 minutes to form an emulsion.
[0093] Step 3, transfer the emulsion to the visualized high-temperature and high-pressure reactor, open the air inlet valve and the vent valve, introduce the stimulating gas CO2 into the visualized high-temperature and high-pressure reactor at a rate of 2L / min, and use the stirring motor of the visualized high-temperature and high-pressure reactor to stir the emulsion during the introduction process. The stirring speed is 200 rpm. During the introduction of the stimulating gas, the emulsion gradually becomes clear and transparent, and the viscosity increases, forming a foam fracturing fluid base liquid; the viscosity of the base liquid is measured to be 156mPa·s.
[0094] Step 4, close the vent valve, turn on the heating switch, and after the temperature of the visualized high temperature and high pressure reactor reaches the simulated temperature of 90°C, continue to introduce the stimulating gas CO2 so that the pressure of the visualized high temperature and high pressure reactor reaches the simulated pressure of 5MPa. Then adjust the stirring speed to 2000 rpm and stir for 3 minutes to form a foam fracturing fluid. It was measured that the CO2 foam fracturing fluid had a liquid separation half-life of 121 minutes under the conditions of 90°C and 5MPa, and the sedimentation rate of 40-70 mesh ceramsite proppant in the fracturing fluid was 0.22cm / min, which met the requirements of fracturing construction.
[0095] Step 5: After the fracturing fluid is used up, the foam fracturing fluid can be recovered. Methane gas is introduced into the prepared foam fracturing fluid at a rate of 0.6 L / min to simulate the interference of methane on the foam fracturing fluid in the reservoir. Methane gradually replaces the irritating gas in the visualized high-temperature and high-pressure reactor, and the foam fracturing fluid is defoamed to obtain an emulsion again. The viscosity of the emulsion is measured to be 1.7 mPa·s.
[0096] Step 6: Repeat steps 3-5 to realize multiple recycling of the foam fracturing fluid, and the performance of the fracturing fluid remains good after repeating the process 4 times.
[0097] The same method as steps S1-S4 is used, except that the strengthening agent is not used, to obtain a foam fracturing fluid. The performance of the fracturing fluid under the conditions of 90°C and 5MPa is that the half-life of the liquid separation is 67min, and the sedimentation rate of the 40-70 mesh ceramsite proppant in the fracturing fluid is 1.18cm / min, indicating the strengthening effect of the strengthening agent on the CO2 foam fracturing fluid.
[0098] Example 6
[0099] A recyclable pseudo-interpenetrating network foam fracturing fluid, the preparation and performance test are as follows:
[0100] Step 1, weigh 3.6wt% of multi-effect agent, 1.8wt% of thickening aid, 2.0wt% of clay stabilizer, 2.0wt% of iron ion stabilizer, 0.2wt% of strengthener, and the balance is water;
[0101] Among them, the multi-effect agent is a mixture of oleamidopropyl dimethylamine and cocoamidopropyl dimethylamine, with a mixing mass ratio of 2:1; the thickening aid is sodium benzenesulfonate; the clay stabilizer is potassium chloride; and the iron ion stabilizer is sodium ethylenediaminetetraacetate.
[0102] Step 2: Add thickening aid, clay stabilizer, iron ion stabilizer and enhancer into water, stir until completely dissolved, then add multi-effect agent and stir for 5 minutes to form an emulsion.
[0103] Step 3, transfer the emulsion to the visualized high-temperature and high-pressure reactor, open the air inlet valve and the vent valve, introduce the stimulating gas CO2 into the visualized high-temperature and high-pressure reactor at a rate of 2.6L / min, and use the stirring motor of the visualized high-temperature and high-pressure reactor to stir the emulsion during the introduction process. The stirring speed is 200 rpm. During the introduction of the stimulating gas, the emulsion gradually becomes clear and transparent, and the viscosity increases, forming a foam fracturing fluid base liquid; the viscosity of the base liquid is measured to be 185mPa·s.
[0104] Step 4, close the vent valve, turn on the heating switch, and after the temperature of the visualized high temperature and high pressure reactor reaches the simulated temperature of 60°C, continue to introduce the stimulating gas CO2 so that the pressure of the visualized high temperature and high pressure reactor reaches the simulated pressure of 40MPa. Then adjust the stirring speed to 2000 rpm and stir for 3 minutes to form a foam fracturing fluid. It was measured that the CO2 foam fracturing fluid has a liquid separation half-life of 159 minutes at 60°C and 40MPa, and the sedimentation rate of 40-70 mesh ceramsite proppant in the fracturing fluid is 0.11cm / min, which meets the requirements of fracturing construction.
[0105] Step 5: After the fracturing fluid is used up, the foam fracturing fluid can be recovered. Methane gas is introduced into the prepared foam fracturing fluid at a rate of 0.6 L / min to simulate the interference of methane on the foam fracturing fluid in the reservoir. Methane gradually replaces the irritating gas in the visualized high-temperature and high-pressure reactor, and the foam fracturing fluid is defoamed to obtain an emulsion again. The viscosity of the emulsion is measured to be 2.3 mPa·s.
[0106] Step 6: Repeat steps 3-5 to realize multiple recycling of the foam fracturing fluid, and the performance of the fracturing fluid remains good after repeating the process 4 times.
[0107] The same method as steps S1-S4 is used, except that the enhancer is not used, to obtain a foam fracturing fluid. The performance of the fracturing fluid at 60°C and 40MPa is that the liquid separation half-life is 126min, and the sedimentation rate of the 40-70 mesh ceramsite proppant in the fracturing fluid is 0.75cm / min, indicating the enhancing effect of the enhancer on the CO2 foam fracturing fluid.
[0108] Comparative example: Foam fracturing fluid produced by a company in Dongguan.
[0109] The residue content after foam fracturing fluid degelation, degelling fluid surface tension, core damage, etc. were tested in accordance with the petroleum and natural gas industry standards SY / 5107-2016 "Fracturing Fluid Performance Evaluation Standard" and SY / T7627-2016 "Fracturing Fluid General Technical Conditions". The test results are shown in Table 1.
[0110] Table 1. Performance test results comparison table
[0111] Test items Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Comparison example Residue content / % 0 0 0 0 0 0 15.8 Surface tension mN / m 23.82 22.66 23.54 22.44 24.86 23.28 52.16 Injury rate / % 0.26 0.31 0.25 0.33 0.36 0.39 21.32
[0112] As can be seen from Table 1, the foam fracturing fluid prepared by the present invention has no residue, low surface tension, good drainage properties, and extremely low damage to the formation, and is particularly suitable for increasing the production of unconventional reservoirs.
[0113] The above description is only a preferred embodiment of the present invention and does not constitute any form of limitation to the present invention. Although the present invention has been disclosed as a preferred embodiment as above, it is not intended to limit the present invention. Any technician familiar with the profession can make some changes or modifications to equivalent embodiments of equivalent changes using the technical contents disclosed above without departing from the scope of the technical solution of the present invention. However, any simple modification, equivalent change and modification made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention still falls within the scope of the technical solution of the present invention.
Claims
1. A recyclable pseudo-interpenetrating network foam fracturing fluid, characterized in that: The following components are included in mass percentage: Multi-effect agent 2-4%, thickening aid 0.1-2%, clay stabilizer 1-2%, iron ion stabilizer 0.5-2.5%, strengthener 0.05-0.5%, the balance is water; The multi-effect agent is selected from one or more of cocoamidopropyl dimethylamine, oleamidopropyl dimethylamine, fatty amide propyl dimethylamine, erucic acid amide propyl dimethylamine; The preparation method of the reinforcing agent is as follows: (1) dispersing nanocellulose in a sodium hydroxide aqueous solution by ultrasonication and mechanically stirring for 2-3 h for alkalization; (2) filtering to remove undissolved solids, then adding 2-(chloromethyl)ethylene oxide to the solution, and stirring at 60-70° C. for 5-6 hours to prepare an intermediate; (3) Add N-methyl-1,2-ethylenediamine and solvent isopropanol to the intermediate, and stir at 75-85° C. for 2-4 hours to obtain a strengthener.
2. The recyclable pseudo-interpenetrating network foam fracturing fluid according to claim 1, characterized in that: The thickening aid is selected from a mixture of one or more of sodium p-benzenesulfonate, sodium salicylate, sodium p-vinylbenzenesulfonate and sodium benzenesulfonate.
3. The recyclable pseudo-interpenetrating network foam fracturing fluid according to claim 1, characterized in that: The clay stabilizer is potassium chloride.
4. The recyclable pseudo-interpenetrating network foam fracturing fluid according to claim 1, characterized in that: The iron ion stabilizer is aminotri(methylenephosphonic acid) or sodium ethylenediaminetetraacetate or a mixture of the two.
5. A method for preparing a recyclable pseudo-interpenetrating network foam fracturing fluid as claimed in any one of claims 1 to 4, characterized in that: Here are the steps: S1. Add thickening agent, clay stabilizer, iron ion stabilizer and fortifier into water and stir until completely dissolved, then add multi-effect agent and stir for several minutes to form an emulsion; S2, introducing stimulating gas CO2 into the emulsion, the emulsion gradually becomes clear and transparent, the viscosity increases, and a foam fracturing fluid base fluid is formed; continue to introduce CO2 into the foam fracturing fluid base fluid to form a foam fracturing fluid; S3, introducing methane gas into the foam fracturing fluid to defoam the foam fracturing fluid and obtain an emulsion again; S4, repeating steps S2 and S3 with the newly obtained emulsion to achieve multiple recycling of the foam fracturing fluid.