A kind of adjustable temporary plugging agent and its preparation method and application

Abstract

The present invention relates to the technical field of temporary plugging agents, and specifically discloses an adjustable temporary plugging agent, a preparation method and an application. The adjustable temporary plugging agent provided by the present invention comprises: 4 parts to 10 parts of polydimethylsiloxane, 4 parts to 5 parts of cationic polyacrylamide, 4 parts to 10 parts of water-soluble chromium salt, 4 parts to 10 parts of water-soluble carboxylates, 1 part to 10 parts of N, N-methylene acrylamide, 2 parts to 10 parts of phenolic resin, 2 parts to 10 parts of chitosan, 10 parts to 120 parts of methyl methacrylate and 100 parts to 200 parts of deionized water. The temporary plugging agent provided by the present invention has a high gelling strength, an excellent plugging effect, a plugging rate of more than 96%, and can realize the integration of plugging and unplugging of the temporary plugging agent, will not cause damage to the reservoir, is convenient for construction operation, can be widely used in the fields of crude oil extraction, petroleum refining, oil well repair, etc., to achieve effective plugging of oil well cracks or production layers, and has a high research and promotion value.

Description

Technical Field

[0001] The invention relates to the technical field of temporary plugging agent preparation, and in particular to an adjustable temporary plugging agent and a preparation method and application thereof. Background Art

[0002] As a large number of mature oil fields have entered the dry period, even after water injection development, only 25%-35% of underground crude oil can be obtained. There are still a large number of unused reservoirs or oil layers with low utilization to be further exploited. Using fracturing means to increase oil and gas production and extend the life of oil wells is a common method at present. Before carrying out fracturing operations, it is necessary to use temporary plugging agents to plug the original cracks. After the fracturing effect is completed, the temporary plugging agents are gradually unblocked to avoid damage to the formation by the temporary plugging agents.

[0003] Temporary plugging agents are usually divided into oily temporary plugging agents, acid-soluble temporary plugging agents and water-soluble temporary plugging agents. With the development of reservoirs, reservoir pressure and oil content decrease. Therefore, oily temporary plugging agents that rely on crude oil to remove temporary plugging agents are gradually withdrawn from major well sites. Acid-soluble temporary plugging agents require a large amount of acid to be injected into the formation to remove plugging. The acid will not only corrode downhole tools, but also corrode the reservoir, causing the permeability of the near-well area to increase. Since the 1980s, water-soluble temporary plugging agents have been widely used in oilfield exploitation. At present, the most commonly used water-soluble temporary plugging agents are mainly temporary plugging agents based on acrylamide, which have the main disadvantages of slow dissolution speed, slow plugging speed, low pressure bearing strength, easy solidification, and difficult to remove plugging. Therefore, a temporary plugging agent with controllable unblocking time, excellent plugging performance, and no effect on the later oil well production performance is needed. Summary of the invention

[0004] In view of the problems of existing temporary plugging agents such as slow plugging speed, uncontrollable plugging time and difficulty in unblocking, the present invention provides an adjustable temporary plugging agent, a preparation method and an application thereof.

[0005] In order to solve the above technical problems, the technical solution provided by the present invention is:

[0006] An adjustable temporary plugging agent comprises the following raw material components in parts by weight: 4-10 parts of polydimethylsiloxane, 4-5 parts of cationic polyacrylamide, 4-10 parts of water-soluble chromium salt, 4-10 parts of water-soluble carboxylate, 1-10 parts of N,N-methylene acrylamide, 2-10 parts of phenolic resin, 2-10 parts of chitosan, 10-120 parts of methyl methacrylate and 100-200 parts of deionized water.

[0007] Compared with the prior art, the adjustable temporary plugging agent provided by the present invention uses polydimethylsiloxane and cationic polyacrylamide as main crosslinking agents, and uses water-soluble cadmium salt and water-soluble carboxylate as secondary crosslinking agents. When mixed on the ground, the primary crosslinking agent and the secondary crosslinking agent undergo a first crosslinking reaction to form a primary crosslinking system; at the same time, the polydimethylsiloxane and N,N-methylene acrylamide in the main crosslinking agent will crosslink with the phenolic resin, and further multiple crosslinking will be performed on the basis of the primary crosslinking system to form a three-dimensional crosslinked network structure, thereby enhancing the plugging effect; furthermore, chitosan and N,N-methylene acrylamide, as well as chitosan, are crosslinked with each other to form a three-dimensional crosslinked network structure. Sugars themselves will also undergo cross-linking, forming a cross-chain structure based on the three-dimensional cross-linked network structure, which significantly enhances the viscosity, strength and stability of the temporary plugging agent, and effectively improves its effect of filling pores and blocking the flow of oil and water; methyl methacrylate, as a degradable breaker, can form a complex with the aluminum-oxygen bonds in the clay through coordination bonds. The formed complex will change the charge and solubility of the clay surface, increase the dispersibility of the clay, and promote the detachment of the clay from the well wall, thereby playing a degumming role. By adjusting the addition ratio of methyl methacrylate, the temporary plugging agent can be automatically unblocked within a specific time, thereby achieving the purpose of controllable unblocking time.

[0008] The temporary plugging agent provided by the present invention not only improves the plugging performance of the temporary plugging agent, but also realizes automatic and complete gel breaking of the temporary plugging agent within 10d-30d, thereby achieving the purpose of integrated plugging and unblocking, and has high promotion value.

[0009] Preferably, the adjustable temporary plugging agent comprises the following raw material components in parts by weight: 5-9 parts of polydimethylsiloxane, 4.3-4.7 parts of cationic polyacrylamide, 5-9 parts of water-soluble chromium salt, 5-9 parts of water-soluble carboxylate, 5-10 parts of N,N-methylene acrylamide, 4-8 parts of phenolic resin, 4-8 parts of chitosan, 40-70 parts of methyl methacrylate and 150-170 parts of deionized water.

[0010] Furthermore, the adjustable temporary plugging agent includes the following raw material components in parts by weight: 8 parts of polydimethylsiloxane, 4.5 parts of cationic polyacrylamide, 8 parts of water-soluble chromium salt, 8 parts of water-soluble carboxylate, 10 parts of N,N-methylene acrylamide, 6 parts of phenolic resin, 6 parts of chitosan, 50 parts of methyl methacrylate and 160 parts of deionized water.

[0011] The preferred dosage of each component can make the prepared gel have higher blocking performance and achieve the effect of automatic gel breaking within 10 days to 30 days.

[0012] Preferably, the mass ratio of the polydimethylsiloxane to the cationic polyacrylamide is 1:0.5-1.

[0013] Preferably, the cationic polyacrylamide has a molecular weight of 10 million to 14 million and an ionicity of 18% to 22%.

[0014] Furthermore, the cationic polyacrylamide has a molecular weight of 12 million and an ionicity of 20%.

[0015] The preferred cationic polyacrylamide can fully cross-link with chromium ions, and is conducive to making the cross-linking reaction have an appropriate reaction speed, thereby ensuring the smooth progress of the construction.

[0016] Preferably, the water-soluble chromium salt is chromium nitrate.

[0017] Preferably, the water-soluble carboxylate is sodium acetate.

[0018] The present invention also provides a method for preparing the adjustable temporary plugging agent described in any one of the above, comprising at least the following steps:

[0019] Weigh each component according to the designed ratio, add the weighed polydimethylsiloxane and cationic polyacrylamide into deionized water, mix evenly, then add the weighed water-soluble chromium salt and water-soluble carboxylate, mix evenly, then add the weighed N,N-methylene acrylamide, phenolic resin and chitosan, stir for 2h-8h, add the weighed methyl methacrylate, react at 50℃-80℃ for 6h-10h, and obtain an adjustable temporary plugging agent.

[0020] The preparation method of the temporary plugging agent provided by the present invention comprises the following steps: firstly dissolving a main cross-linking agent (polydimethylsiloxane and cationic polyacrylamide) in water, adding a secondary cross-linking agent (cadmium salt and carboxylate) to cross-link the main cross-linking agent and the secondary cross-linking agent to form a primary cross-linking system, then adding N,N-methylene acrylamide, phenolic resin and chitosan to cross-link the polydimethylsiloxane in the main cross-linking agent with the phenolic resin, the N,N-methylene acrylamide with the phenolic resin, the N,N-methylene acrylamide with the chitosan, and the chitosan itself to form a complex three-dimensional cross-linking network, thereby enhancing the viscosity, gelling strength and stability of the temporary plugging agent; after adding methyl methacrylate, heating is performed at a certain temperature, so that the methyl methacrylate can be fully mixed with the system, and the cross-linking reaction between various components can be further promoted, the viscosity of the system is improved, and the plugging effect of the temporary plugging agent is further enhanced.

[0021] The present invention also provides the use of any of the above-mentioned reversible composite gels in oil field exploitation or oil field well repair.

[0022] The temporary plugging agent provided by the present invention has high gelling strength and excellent plugging effect. The plugging rate can reach more than 96%, and the temporary plugging agent can realize the integration of plugging and unplugging without causing damage to the reservoir. The construction operation is convenient, and the temporary plugging agent can be widely used in the fields of crude oil extraction, petroleum refining, oil well repair, etc. to achieve effective plugging of oil well cracks or production layers, and has high research and promotion value. DETAILED DESCRIPTION

[0023] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0024] In order to better illustrate the present invention, further examples are given below.

[0025] Example 1

[0026] The present embodiment provides an adjustable temporary plugging agent, comprising the following raw material components in parts by weight: 8 parts of polydimethylsiloxane, 4.5 parts of cationic polyacrylamide, 8 parts of water-soluble chromium salt, 8 parts of water-soluble carboxylate, 10 parts of N,N-methylene acrylamide, 6 parts of phenolic resin, 6 parts of chitosan, 50 parts of methyl methacrylate and 160 parts of deionized water.

[0027] The cationic polyacrylamide has a molecular weight of 12 million and an ionicity of 20%.

[0028] The preparation method of the above-mentioned adjustable temporary plugging agent is as follows:

[0029] Weigh each component according to the designed ratio, add the weighed polydimethylsiloxane and cationic polyacrylamide into deionized water, stir until completely dissolved, add the weighed chromium nitrate and sodium acetate, stir and mix for 30 minutes, then add the weighed N,N-methylene acrylamide, phenolic resin and chitosan, stir for 4 hours, add the weighed methyl methacrylate, react at 75°C for 6 hours to obtain an adjustable temporary plugging agent.

[0030] Example 2

[0031] The present embodiment provides an adjustable temporary plugging agent, comprising the following raw material components in parts by weight: 4 parts of polydimethylsiloxane, 4 parts of cationic polyacrylamide, 4 parts of chromium nitrate, 4 parts of sodium acetate, 1 part of N,N-methylene acrylamide, 2 parts of phenolic resin, 2 parts of chitosan, 10 parts of methyl methacrylate and 100 parts of deionized water.

[0032] The cationic polyacrylamide has a molecular weight of 12 million and an ionicity of 20%.

[0033] The preparation method of the above-mentioned adjustable temporary plugging agent is as follows:

[0034] Weigh each component according to the designed ratio, add the weighed polydimethylsiloxane and cationic polyacrylamide into deionized water, stir until completely dissolved, add the weighed chromium nitrate and sodium acetate, stir and mix for 30 minutes, then add the weighed N,N-methylene acrylamide, phenolic resin and chitosan, stir for 2 hours, add the weighed methyl methacrylate, react at 65°C for 8 hours to obtain an adjustable temporary plugging agent.

[0035] Example 3

[0036] The present embodiment provides an adjustable temporary plugging agent, comprising the following raw material components in parts by weight: 6 parts of polydimethylsiloxane, 4.5 parts of cationic polyacrylamide, 6 parts of chromium nitrate, 6 parts of sodium acetate, 5 parts of N,N-methylene acrylamide, 4 parts of phenolic resin, 4 parts of chitosan, 50 parts of methyl methacrylate and 180 parts of deionized water.

[0037] The cationic polyacrylamide has a molecular weight of 12 million and an ionicity of 20%.

[0038] The preparation method of the above-mentioned adjustable temporary plugging agent is as follows:

[0039] Weigh each component according to the designed ratio, add the weighed polydimethylsiloxane and cationic polyacrylamide into deionized water, stir until completely dissolved, add the weighed chromium nitrate and sodium acetate, stir and mix for 30 minutes, then add the weighed N,N-methylene acrylamide, phenolic resin and chitosan, stir for 5 hours, add the weighed methyl methacrylate, react at 60°C for 7 hours to obtain an adjustable temporary plugging agent.

[0040] Example 4

[0041] The present embodiment provides an adjustable temporary plugging agent, comprising the following raw material components in parts by weight: 7 parts of polydimethylsiloxane, 4.5 parts of cationic polyacrylamide, 9 parts of chromium nitrate, 7 parts of sodium acetate, 8 parts of N,N-methylene acrylamide, 7 parts of phenolic resin, 5 parts of chitosan, 120 parts of methyl methacrylate and 160 parts of deionized water.

[0042] The cationic polyacrylamide has a molecular weight of 12 million and an ionicity of 20%.

[0043] The preparation method of the above-mentioned adjustable temporary plugging agent is as follows:

[0044] Weigh each component according to the designed ratio, add the weighed polydimethylsiloxane and cationic polyacrylamide into deionized water, stir until completely dissolved, add the weighed chromium nitrate and sodium acetate, stir and mix for 30 minutes, then add the weighed N,N-methylene acrylamide, phenolic resin and chitosan, stir for 4 hours, add the weighed methyl methacrylate, react at 50°C for 10 hours to obtain an adjustable temporary plugging agent.

[0045] Example 5

[0046] The present embodiment provides an adjustable temporary plugging agent, comprising the following raw material components in parts by weight: 10 parts of polydimethylsiloxane, 5 parts of cationic polyacrylamide, 10 parts of chromium nitrate, 10 parts of sodium acetate, 10 parts of N,N-methylene acrylamide, 10 parts of phenolic resin, 10 parts of chitosan, 70 parts of methyl methacrylate and 200 parts of deionized water.

[0047] The cationic polyacrylamide has a molecular weight of 12 million and an ionicity of 20%.

[0048] The preparation method of the above-mentioned adjustable temporary plugging agent is as follows:

[0049] Weigh each component according to the designed ratio, add the weighed polydimethylsiloxane and cationic polyacrylamide into deionized water, stir until completely dissolved, add the weighed chromium nitrate and sodium acetate, stir and mix for 30 minutes, then add the weighed N,N-methylene acrylamide, phenolic resin and chitosan, stir for 8 hours, add the weighed methyl methacrylate, react at 80°C for 6 hours to obtain an adjustable temporary plugging agent.

[0050] Comparative Example 1

[0051] This comparative example provides an adjustable temporary plugging agent, the raw material composition of which is exactly the same as that of Example 1, except that polydimethylsiloxane is replaced by an equal amount of cationic polyacrylamide.

[0052] The preparation method of the above-mentioned adjustable temporary plugging agent is exactly the same as that in Example 1, and will not be repeated here.

[0053] Comparative Example 2

[0054] This comparative example provides an adjustable temporary plugging agent, the raw material composition of which is exactly the same as that of Example 1, except that polydimethylsiloxane is replaced by an equal amount of polyvinyl alcohol.

[0055] The preparation method of the above-mentioned adjustable temporary plugging agent is exactly the same as that in Example 1, and will not be repeated here.

[0056] Comparative Example 3

[0057] This comparative example provides an adjustable temporary plugging agent, the raw material composition of which is exactly the same as that of Example 1, except that N,N-methylene acrylamide is replaced by an equal amount of acrylamide.

[0058] The preparation method of the above-mentioned adjustable temporary plugging agent is exactly the same as that in Example 1, and will not be repeated here.

[0059] Comparative Example 4

[0060] This comparative example provides an adjustable temporary plugging agent, the raw material composition of which is exactly the same as that of Example 1, except that methyl methacrylate is replaced by an equal amount of hydroxy diester of acrylate.

[0061] The preparation method of the above-mentioned adjustable temporary plugging agent is exactly the same as that in Example 1, and will not be repeated here.

[0062] Performance testing of temporary plugging agents

[0063] 1. Compression performance test

[0064] Prepare displacement water with a mineralization of 8000 mg / L sodium chloride and 5000 mg / L calcium chloride, take the temporary plugging agents prepared in Examples 1-5 and Comparative Examples 1-4, and use a multifunctional core displacement device to conduct a pressure displacement test. The displacement pressure is set to 30.0 MPa, and the water is driven at a rate of 1 mL / min until the water content of the outlet water is 98%. The temporary plugging agent is injected. After the pumping is completed, it is placed at 60°C to gel for 8 hours, and displacement water is injected at a rate of 1 mL / min until the first drop of displacement fluid flows out of the core outlet. The pressure change during the process is recorded, and the highest pressure point is the breakthrough pressure. The test results are shown in Table 1.

[0065] Table 1

[0066]

[0067]

[0068] It can be seen from the above table that the breakthrough pressure of the composite gel prepared in the example is greater than 18 MPa, indicating that the temporary plugging agent has excellent pressure resistance and is conducive to improving the success rate of open well operations.

[0069] 2. Gelation time and deblocking time

[0070] The temporary plugging agents prepared in Examples 1-5 were evenly divided into 5 portions, respectively, and placed in a constant temperature oil bath at 60° C. for constant temperature curing, and the gelation and gel breaking of the composite gel were regularly observed.

[0071] Determination of gelation time: Use the inversion method, place the sample horizontally for 1 minute, and the gelation endpoint is when the sample stops flowing completely, and record the gelation time.

[0072] Unblocking time test: start timing after the gel is completely gelled, and use a rheometer to measure the viscosity value. When the viscosity is less than 30mPa·s, it is completely broken, and the unblocking time is recorded.

[0073] The test results show that the temporary plugging agent prepared in the embodiment of the present invention has a gelling time of 6h-8h and a plugging removal time of 10d-30d.

[0074] 3. Blockage rate and unblocking rate

[0075] Prepare displacement water with a mineralization of 8000 mg / L sodium chloride and 5000 mg / L calcium chloride, take the temporary plugging agents prepared in Examples 1-5 and Comparative Examples 1-4, and use a multifunctional core displacement device to conduct a pressure displacement test. Add clay to the core to simulate the formation fracture environment in the oil and water well, set the displacement pressure to 30.0 MPa, and drive at a speed of 1 mL / min until the water content of the outlet water is 98%. Inject 1L of temporary plugging agent, and after the pumping is completed, place it at 60°C to gel for 8 hours, measure its permeability, and calculate the plugging rate. After the test is completed, place the core and the core holder at a constant temperature of 60°C for 20 hours, and continue to measure its permeability after the constant temperature ends, and calculate the unblocking rate. The test results are shown in Table 2.

[0076] Plugging rate = (initial permeability - permeability after plugging) / initial permeability × 100%

[0077] Unblocking rate = permeability after unblocking / initial permeability × 100%

[0078] Table 2

[0079]

[0080]

[0081] It can be seen from the above table that the temporary plugging agent prepared in the embodiment of the present invention has a plugging rate of more than 96% and a plugging removal rate of more than 80%, indicating that the temporary plugging agent of the present invention can achieve integrated plugging and plugging removal, has a high plugging removal rate, and has little impact on the formation.

[0082] In summary, the temporary plugging agent prepared by the present invention can achieve the purpose of integrated plugging and unblocking, without the need to inject other substances for unblocking. At the same time, the temporary plugging agent has good pressure bearing strength and plugging performance, and the preparation process of the temporary plugging agent is simple and the raw material cost is low. It has broad application prospects in the field of oil field exploitation or oil field well repair.

[0083] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modification, equivalent substitution or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A controllable temporary plugging agent, It is characterized in that The invention comprises the following raw material components in parts by weight: 4-10 parts of polydimethylsiloxane, 4-5 parts of cationic polyacrylamide, 4-10 parts of water-soluble chromium salt, 4-10 parts of water-soluble carboxylate, 1-10 parts of N,N-methylene acrylamide, 2-10 parts of phenolic resin, 2-10 parts of chitosan, 10-120 parts of methyl methacrylate and 100-200 parts of deionized water.

2. The adjustable temporary plugging agent according to claim 1, It is characterized in that The invention comprises the following raw material components in parts by weight: 5-9 parts of polydimethylsiloxane, 4.3-4.7 parts of cationic polyacrylamide, 5-9 parts of water-soluble chromium salt, 5-9 parts of water-soluble carboxylate, 5-10 parts of N,N-methylene acrylamide, 4-8 parts of phenolic resin, 4-8 parts of chitosan, 40-70 parts of methyl methacrylate and 150-170 parts of deionized water.

3. The adjustable temporary plugging agent according to claim 2, It is characterized in that The invention comprises the following raw material components in parts by weight: 8 parts of polydimethylsiloxane, 4.5 parts of cationic polyacrylamide, 8 parts of water-soluble chromium salt, 8 parts of water-soluble carboxylate, 10 parts of N,N-methylene acrylamide, 6 parts of phenolic resin, 6 parts of chitosan, 50 parts of methyl methacrylate and 160 parts of deionized water.

4. The adjustable temporary plugging agent according to any one of claims 1 to 2, It is characterized in that The mass ratio of the polydimethylsiloxane to the cationic polyacrylamide is 1:0.5-1.

5. The adjustable temporary plugging agent according to any one of claims 1 to 3, It is characterized in that The cationic polyacrylamide has a molecular weight of 10 million to 14 million and an ionicity of 18% to 22%.

6. The adjustable temporary plugging agent according to claim 5, It is characterized in that The cationic polyacrylamide has a molecular weight of 12 million and an ionicity of 20%.

7. The adjustable temporary plugging agent according to any one of claims 1 to 3, It is characterized in that The water-soluble chromium salt is chromium nitrate.

8. The adjustable temporary plugging agent according to any one of claims 1 to 3, It is characterized in that The water-soluble carboxylate is sodium acetate.

9. A method for preparing the adjustable temporary plugging agent according to any one of claims 1 to 8, It is characterized in that At least the following steps are included: Weigh each component according to the designed ratio, add the weighed polydimethylsiloxane and cationic polyacrylamide into deionized water, mix evenly, then add the weighed water-soluble chromium salt and water-soluble carboxylate, mix evenly, then add the weighed N,N-methylene acrylamide, phenolic resin and chitosan, stir for 2h-8h, add the weighed methyl methacrylate, react at 50℃-80℃ for 6h-10h, and obtain an adjustable temporary plugging agent.

10. Use of the controllable temporary plugging agent according to claim 9 in oil field exploitation or oil field well repair.

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