Degradable temporary plugging particles as well as preparation method and application thereof

Abstract

The invention discloses degradable temporary plugging particles as well as a preparation method and application thereof, and relates to the technical field of oil exploitation. According to the invention, polylactic acid, an inorganic reinforcing filler, a surfactant, a plasticizer, a cross-linking agent and an initiator are adopted as raw materials, and the temporary plugging particles with a three-dimensional network structure are prepared through a cross-linking reaction. The inorganic reinforcing filler, the surfactant and the plasticizer are added on the basis of the polylactic acid, and a cross-linking reaction is carried out under the action of the cross-linking agent and the initiator, so that the compatibility of the temporary plugging particles and oil reservoir fluid can be improved, the temporary plugging reinforcing effect of the temporary plugging particles is improved, and the oil exploitation efficiency is improved; the temperature resistance, the strength and the degradation performance of the temporary plugging particles can be improved, and meanwhile, the prepared temporary plugging particles are simple in process, easy to operate and suitable for large-scale industrial production.

Description

Technical Field

[0001] The present invention relates to the technical field of oil extraction, and particularly to a degradable temporary plugging particle, a preparation method thereof, and an application thereof. Background Art

[0002] In oil extraction operations, the temporary plugging technology plays a key role in effectively plugging specific areas of the reservoir and improving the extraction efficiency. As the core material of this technology, the performance of the temporary plugging agent directly determines the quality of the temporary plugging effect. With the continuous improvement of the country's requirements for green environmental protection in oilfields, self-degradable temporary plugging agents with characteristics such as environmental protection, pollution-free, and self-cleaning are increasingly favored.

[0003] Currently, common chemically synthesized degradable polymers mainly include polylactic acid (PLA), polycaprolactone, polyglycolide, etc. However, in terms of the mechanical properties of the materials, these degradable polymers have good ductility and flexibility, but low melting points, poor heat resistance, and low mechanical strength and elastic modulus, which limit their application as temporary plugging agents in the process of oil extraction. Therefore, it is necessary to modify the degradable polymers to improve their heat resistance and mechanical properties, etc., so as to meet the actual temporary plugging requirements and improve the oil extraction efficiency.

[0004] In the prior art, CN112745819A discloses a degradable temporary plugging agent and a preparation method thereof. The degradable temporary plugging agent includes a polyester material and inorganic nanoparticles added to the polyester material. Among them, the polyester material is at least two of polylactic acid, polyglycolide, and polybutylene succinate, and the inorganic nanoparticles are nano-silica, etc. The viscosity of the prepared degradable temporary plugging agent can reach 79 mPa·s, the swelling ratio can reach 32 times, the temporary plugging strength can reach 7.9 kPa, and the degradation rate can reach 98.3% at a temperature of 100°C. However, the above temporary plugging agent is only prepared by melt blending of raw materials. Due to the large difference in melting points between the raw materials, uniform mixing between the raw materials cannot be achieved during the preparation process, thereby affecting the performance of the temporary plugging agent. CN112795373A discloses a soluble temporary plugging agent, a temporary plugging ball for fracturing applicable to different temperatures, and a preparation method thereof. The temporary plugging ball is prepared from polycaprolactone, polylactic acid, polyglycolic acid, polybutylene succinate, nano-silica, and a chain extender. It uses the chain extender triglycidyl isocyanurate to carry out high-density crosslinking with the polyester resin to prepare the temporary plugging agent, and at the same time introduces nano-silica to enhance toughness, but the prepared temporary plugging agent has poor compatibility with reservoir fluids, thereby affecting the temporary plugging performance of the temporary plugging agent.

[0005] Therefore, based on polylactic acid, developing a degradable temporary plugging particle with good heat resistance, strength, degradation performance, and temporary plugging performance, and using it in the process of oil drilling can improve the recovery rate of crude oil and bring new breakthroughs to the oil extraction industry. Summary of the Invention

[0006] In view of the above-mentioned prior art, the object of the present invention is to provide a degradable temporary plugging particle and its preparation method and application. The present invention uses polylactic acid, inorganic reinforcing filler, surfactant, plasticizer, crosslinking agent and initiator as raw materials, and prepares a temporary plugging particle with a three-dimensional network structure through a crosslinking reaction. Among them, by adding an inorganic reinforcing filler, a surfactant and a plasticizer on the basis of polylactic acid, and undergoing a crosslinking reaction under the action of a crosslinking agent and an initiator, the degradation performance, plugging performance and strength of the temporary plugging particle can be improved.

[0007] To achieve the above object, the present invention adopts the following technical solutions:

[0008] In the first aspect of the present invention, a degradable temporary plugging particle is provided, and the degradable temporary plugging particle is prepared by mixing polylactic acid, inorganic reinforcing filler, surfactant, plasticizer, crosslinking agent and initiator in a weight ratio of (20-40):(10-20):(5-10):(3-8):(2-5):(1-3);

[0009] The inorganic reinforcing filler is one or more of nano-silica, kaolin or montmorillonite, the surfactant is one or more of Tween-80, OP-10, AEO-9, AEO-10, and the plasticizer is tributyl citrate.

[0010] Preferably, the crosslinking agent is N,N'-methylenebisacrylamide, and the initiator is potassium persulfate and / or azodiisobutyramidine hydrochloride.

[0011] In the second aspect of the present invention, a preparation method of the above-mentioned degradable temporary plugging particle is provided, including the following steps:

[0012] (1) Heat the polylactic acid to a molten state, and sequentially add the inorganic reinforcing filler, surfactant and plasticizer, and then stir to obtain a premix;

[0013] (2) After mixing the crosslinking agent and the initiator, add them to deionized water to obtain a mixed solution, add the mixed solution to the premix for reaction, and after the reaction is completed, granulate, form and dry to obtain the degradable temporary plugging particle.

[0014] Preferably, in step (1), the heating temperature is 150-180°C.

[0015] Preferably, in step (1), the stirring time is 30-60 min.

[0016] Preferably, in step (2), the mass ratio of the total mass of the crosslinking agent and the initiator to the mass of deionized water is (0.5-1.5):20.

[0017] Preferably, in step (2), the reaction temperature is 70-90°C, and the reaction time is 2-4 h.

[0018] Preferably, in step (2), the drying temperature is 80 - 100 °C, and the drying time is 2 - 3 h.

[0019] Preferably, in step (2), the particle size of the degradable temporary plugging particles is 0.1 - 1 mm.

[0020] In the third aspect of the present invention, there is provided an application of the above-mentioned degradable temporary plugging particles in oil drilling and / or oil and gas field development.

[0021] Advantages of the present invention:

[0022] The present invention uses polylactic acid, inorganic reinforcing filler, surfactant, plasticizer, crosslinking agent and initiator as raw materials, and prepares degradable temporary plugging particles with a three-dimensional network structure through a crosslinking reaction. Among them, polylactic acid is used as the main raw material to give full play to the good heat resistance and biodegradability advantages of polylactic acid itself, so as to ensure the heat resistance and degradability of the prepared temporary plugging particles. After meeting the temporary plugging requirements of the reservoir, the temporary plugging particles can be naturally degraded, effectively reducing the long-term impact on the reservoir environment and conforming to the concept of green and environmental protection mining. At the same time, inorganic reinforcing filler, surfactant and plasticizer are added on the basis of polylactic acid, and a crosslinking reaction occurs under the action of a crosslinking agent and an initiator, which can not only improve the compatibility of the temporary plugging particles with the reservoir fluid, so as to improve the dispersibility and stability of the temporary plugging particles in the reservoir, thus significantly enhancing the temporary plugging effect and improving the oil recovery efficiency, but also improving the heat resistance, strength and processing performance of the temporary plugging particles. In addition, the preparation process of the temporary plugging particles of the present invention is simple, easy to operate, does not require complex equipment and high-cost investment, is suitable for large-scale industrial production, and has significant economic value and market competitiveness. Description of the Drawings

[0023] Figure 1 : Picture of the temporary plugging particles prepared in Example 1. Detailed Description of the Invention

[0024] It should be noted that the following detailed description is illustrative and is intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present application belongs.

[0025] In the prior art, the temporary plugging agent, as the core material of the temporary plugging technology, its performance directly determines the quality of the temporary plugging effect. With the continuous improvement of the country's requirements for green environmental protection in oil fields, self-degradable temporary plugging agents with characteristics such as environmental protection, pollution-free, and self-cleaning are becoming more and more popular. And polylactic acid has the characteristics of degradability and good temperature resistance. Therefore, using polylactic acid as the base material to develop a degradable temporary plugging material with excellent temporary plugging performance, high strength, good temperature resistance, and good compatibility with reservoir fluids to meet the actual temporary plugging needs and improve oil recovery efficiency has important practical significance and broad application prospects.

[0026] Based on this, the present invention provides a degradable temporary plugging particle, which is prepared by mixing polylactic acid, inorganic reinforcing filler, surfactant, plasticizer, crosslinking agent and initiator. The present invention uses polylactic acid as the base material, and utilizes the good temperature resistance and degradability of polylactic acid to enhance the temperature resistance and degradation performance of the prepared temporary plugging particles. The three components of inorganic reinforcing filler, surfactant and plasticizer are used as modifiers of polylactic acid, and under the joint action of crosslinking agent and initiator, polylactic acid is modified, so that the strength, compatibility with reservoir fluids and temporary plugging performance of the prepared temporary plugging particles with three-dimensional network structure are significantly improved.

[0027] In order to enable those skilled in the art to more clearly understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below in conjunction with specific embodiments.

[0028] The experimental materials used in the embodiments of the present invention are all conventional experimental materials in the art and can be obtained through commercial channels.

[0029] Example 1: Preparation method of degradable temporary plugging particles

[0030] Prepare polylactic acid, inorganic reinforcing filler, surfactant, plasticizer, crosslinking agent and initiator according to a weight ratio of 30:15:8:5:4:2. Among them, the inorganic reinforcing filler is nano-silica, the surfactant is polyoxyethylene sorbitan fatty acid ester, the plasticizer is tributyl citrate, the crosslinking agent is N,N'-methylenebisacrylamide, and the initiator is potassium persulfate;

[0031] The specific preparation process is as follows:

[0032] (1) Heat polylactic acid to 165 °C to make it in a molten state, and sequentially add inorganic reinforcing filler, surfactant and plasticizer to the molten polylactic acid, and stir for 45 minutes to obtain a premix;

[0033] (2) After mixing the crosslinking agent and the initiator, add them to deionized water to obtain a mixed solution; then add the mixed solution to the premix and react at 80 °C for 3 h. After the reaction is completed, granulate and then dry at 90 °C for 2.5 h to obtain degradable temporary plugging particles with a particle size of 0.1 - 1.0 mm.

[0034] Example 2: Preparation method of degradable temporary plugging particles

[0035] Weigh poly(lactic acid), inorganic reinforcing filler, surfactant, plasticizer, crosslinking agent and initiator according to a weight ratio of 20:10:5:3:2:1. Among them, the inorganic reinforcing filler is nano-silica, the surfactant is polyoxyethylene sorbitan fatty acid ester, the plasticizer is tributyl citrate, the crosslinking agent is N,N'-methylenebisacrylamide, and the initiator is potassium persulfate;

[0036] The specific preparation process is as follows:

[0037] (1) Heat poly(lactic acid) to 150 °C to make it molten, and sequentially add the inorganic reinforcing filler, surfactant and plasticizer to the molten poly(lactic acid). After stirring for 60 min, obtain a premix;

[0038] (2) After mixing the crosslinking agent and the initiator, add them to deionized water to obtain a mixed solution; then add the mixed solution to the premix and react at 70 °C for 4 h. After the reaction is completed, granulate and then dry at 80 °C for 2 h to obtain degradable temporary plugging particles with a particle size of 0.1 - 1.0 mm.

[0039] Example 3: Preparation method of degradable temporary plugging particles

[0040] Weigh poly(lactic acid), inorganic reinforcing filler, surfactant, plasticizer, crosslinking agent and initiator according to a weight ratio of 40:20:10:8:5:3. Among them, the inorganic reinforcing filler is nano-silica, the surfactant is polyoxyethylene sorbitan fatty acid ester, the plasticizer is tributyl citrate, the crosslinking agent is N,N'-methylenebisacrylamide, and the initiator is potassium persulfate;

[0041] The specific preparation process is as follows:

[0042] (1) Heat poly(lactic acid) to 180 °C to make it molten, and sequentially add the inorganic reinforcing filler, surfactant and plasticizer to the molten poly(lactic acid). After stirring for 30 min, obtain a premix;

[0043] (2) After mixing the crosslinking agent and the initiator, add them to deionized water to obtain a mixed solution; then add the mixed solution to the premix and react at 90 °C for 2 h. After the reaction is completed, granulate and dry at 100 °C for 2 h to obtain degradable temporary plugging particles with a particle size of 0.1 - 1.0 mm.

[0044] Comparative Example 1:

[0045] Prepare polylactic acid, crosslinking agent and initiator according to a weight ratio of 30:4:2. Among them, the crosslinking agent is N,N'-methylenebisacrylamide, and the initiator is potassium persulfate;

[0046] The specific preparation method is as follows:

[0047] (1) Heat polylactic acid to 165 °C to make it in a molten state, stir for 45 min to obtain a premix;

[0048] (2) After mixing the crosslinking agent and the initiator, add them to deionized water to obtain a mixed solution; then add the mixed solution to the premix and react at 80 °C for 3 h. After the reaction is completed, granulate and dry at 90 °C for 2.5 h to obtain degradable temporary plugging particles with a particle size of 0.1 - 1.0 mm.

[0049] Comparative Example 2:

[0050] Prepare polylactic acid, inorganic reinforcing filler, crosslinking agent and initiator according to a weight ratio of 30:15:4:2. Among them, the inorganic reinforcing filler is nano-silica, the crosslinking agent is N,N'-methylenebisacrylamide, and the initiator is potassium persulfate;

[0051] The specific preparation method is as follows:

[0052] (1) Heat polylactic acid to 165 °C to make it in a molten state, add the inorganic reinforcing filler to the molten polylactic acid, and stir for 45 min to obtain a premix;

[0053] (2) After mixing the crosslinking agent and the initiator, add them to deionized water to obtain a mixed solution; then add the mixed solution to the premix and react at 80 °C for 3 h. After the reaction is completed, granulate and dry at 90 °C for 2.5 h to obtain degradable temporary plugging particles with a particle size of 0.1 - 1.0 mm.

[0054] Comparative Example 3:

[0055] Prepare polylactic acid, surfactant, crosslinking agent and initiator according to a weight ratio of 30:8:4:2. Among them, the surfactant is polyoxyethylene sorbitan fatty acid ester, the crosslinking agent is N,N'-methylenebisacrylamide, and the initiator is potassium persulfate;

[0056] The specific preparation method is as follows:

[0057] (1) Heat the polylactic acid to 165 °C to make it in a molten state, add the surfactant to the molten polylactic acid, and stir for 45 min to obtain a premix.

[0058] (2) Mix the crosslinking agent and the initiator, add them to deionized water to obtain a mixed solution; then add the mixed solution to the premix, react at 80 °C for 3 h, after the reaction is completed, granulate and dry at 90 °C for 2.5 h to obtain degradable temporary plugging particles with a particle size of 0.1 - 1.0 mm.

[0059] Comparative Example 4:

[0060] Prepare the polylactic acid, plasticizer, crosslinking agent and initiator according to a weight ratio of 30:5:4:2, wherein the plasticizer is tributyl citrate, the crosslinking agent is N,N'-methylenebisacrylamide, and the initiator is potassium persulfate.

[0061] The specific preparation method is as follows:

[0062] (1) Heat the polylactic acid to 165 °C to make it in a molten state, add the plasticizer to the molten polylactic acid in sequence, and stir for 45 min to obtain a premix.

[0063] (2) Mix the crosslinking agent and the initiator, add them to deionized water to obtain a mixed solution; then add the mixed solution to the premix, react at 80 °C for 3 h, after the reaction is completed, granulate and dry at 90 °C for 2.5 h to obtain degradable temporary plugging particles with a particle size of 0.1 - 1.0 mm.

[0064] Test Example 1: Performance Detection

[0065] 1. Degradation rate

[0066] Put the degradable temporary plugging particles into a beaker containing distilled water, the material-liquid ratio of the degradable temporary plugging particles to distilled water is 1 g:20 mL, place them in an oil bath at 120 °C for constant temperature degradation treatment for 24 h, filter, separate the solid, dry and weigh, calculate the degradation rate, and the results are shown in Table 1.

[0067] Among them, the calculation formula for the degradation rate is:

[0068] Degradation rate = [(m1 - m2) / m1] × 100%;

[0069] In the formula, m1 is the mass of the temporary plugging particles before degradation, g; m2 is the mass of the temporary plugging particles after degradation, g.

[0070] 2. Plugging performance and unplugging performance

[0071] Select cores with specifications of D (diameter) = 2.50 cm, L (height) = 6.11 cm, and V 孔隙 = 1.42 cm 3 for the experiment, and measure the permeability K0 of the cores;

[0072] Mix the temporary plugging particles and fracturing fluid prepared in Example 1 and Comparative Examples 1-4 at a material-liquid ratio of 1 g: 20 mL to obtain a fracturing fluid containing temporary plugging particles. Among them, the fracturing fluid is prepared from fresh water, guar gum solution, and hydrochloric acid, and the mass fraction of the guar gum solution is 0.3%;

[0073] Pass the cores through the fracturing fluid containing temporary plugging particles, measure the permeability K1 of the cores, then pass through brine for backwashing and measure the permeability K2 of the cores, and calculate the temporary plugging rate and the core permeability recovery rate. The results are shown in Table 1.

[0074] The calculation formula for the temporary plugging rate is: temporary plugging rate = [(K0 - K1) / K0] × 100%;

[0075] The calculation formula for the core permeability recovery rate is: core permeability recovery rate = (K2 / K0) × 100%.

[0076] 3. Temperature resistance performance

[0077] Mix bentonite, deionized water, and sodium carbonate at 12 g: 400 mL: 0.6 g and stir for 25 min to obtain a bentonite-based slurry; add the plugging particles prepared in Example 1 and Comparative Examples 1-4 to the bentonite-based slurry to obtain a drilling fluid containing plugging particles. Among them, the mass ratio of the plugging particles to the bentonite is 1: 3; then age the above drilling fluid at 160 °C for 16 h, and refer to GB / T 16783.1-2014 "Petroleum and natural gas industries - Drilling fluids - Field testing - Part 1: Water-based drilling fluids" to measure the apparent viscosity (AV) of the aged drilling fluid, and detect the medium-pressure filtration loss (API, 0.7 MPa, room temperature, 30 min) of the drilling fluid. The results are shown in Table 1.

[0078] 4. Pressure-bearing strength

[0079] Determine the pressure-bearing strength of the temporary plugging particles prepared in Example 1 and Comparative Examples 1-4 through a core flow tester to determine the plugging strength of each temporary plugging particle. The results are shown in Table 1. Specifically: wet the temporary plugging particles with water and load them into a steel ring to prepare a filter cake with a thickness of 1.0 cm, place the filter cake in a core holder, heat up to 160 °C, and record the maximum pressure at the inlet end of the core holder during the displacement process, which is the pressure-bearing strength of the temporary plugging particles.

[0080] Table 1 Performance of the temporary plugging particles prepared in Example 1 and Comparative Examples 1-4

[0081]

[0082] As can be seen from Table 1, the degradation rate of the temporary plugging particles prepared by the present invention can reach 96.8%, the plugging rate is 99.7%, the core permeability recovery rate is 99.5%, the apparent viscosity is 26 mPa·s, the medium-pressure filtration loss is 1.8 mL, and the pressure-bearing strength is 26 MPa, which are much higher than the above performances of the temporary plugging particles prepared in Comparative Examples 1-4. Among them, the higher the apparent viscosity and the lower the medium-pressure filtration loss of the aged temporary plugging material, the more it proves that the temporary plugging material will not be decomposed at high temperature, which further indicates that the temporary plugging material has good temperature resistance. As can be seen from Table 1, the present invention has a synergistic effect in improving the temporary plugging performance and temperature resistance of the temporary plugging material by adding inorganic reinforcing fillers, surfactants and plasticizers on the basis of acid.

[0083] The above are only the preferred embodiments of the present application and are not used to limit the present application. For those skilled in the art, various changes and modifications can be made to the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A degradable temporary plugging particle, characterized in that: The degradable temporary plugging particles are prepared by mixing polylactic acid, inorganic reinforcing filler, surfactant, plasticizer, crosslinking agent and initiator in a weight ratio of (20-40): (10-20): (5-10): (3-8): (2-5): (1-3); The inorganic reinforcing filler is one or more of nano-silicon dioxide, kaolin or montmorillonite, the surfactant is one or more of Tween-80, OP-10, AEO-9 and AEO-10, and the plasticizer is tributyl citrate.

2. The degradable temporary plugging particles according to claim 1, characterized in that: The cross-linking agent is N,N'-methylenebisacrylamide, and the initiator is potassium persulfate and / or azobisisobutyric acid salt.

3. The method for preparing the degradable temporary plugging particles according to claim 1 or 2, characterized in that: The following steps are involved: (1) heating polylactic acid to a molten state, sequentially adding an inorganic reinforcing filler, a surfactant, and a plasticizer, and stirring to obtain a premix; (2) After mixing the crosslinking agent and the initiator, add them into deionized water to obtain a mixed solution, add the mixed solution into the premix to react, and after the reaction is completed, granulate and dry to obtain the degradable temporary plugging particles.

4. The method for preparing the degradable temporary plugging particles according to claim 3, characterized in that: In step (1), the heating temperature is 150-180° C. and the stirring time is 30-60 min.

5. The method for preparing the degradable temporary plugging particles according to claim 3, characterized in that: In step (2), the mass ratio of the total mass of the crosslinking agent and the initiator to the mass of deionized water is (0.5-1.5):

20.

6. The method for preparing the degradable temporary plugging particles according to claim 3, characterized in that: In step (2), the reaction temperature is 70-90°C and the reaction time is 2-4h.

7. The method for preparing the degradable temporary plugging particles according to claim 3, characterized in that: In step (2), the drying temperature is 80-100° C. and the drying time is 2-3 h.

8. The method for preparing the degradable temporary plugging particles according to claim 3, characterized in that: In step (2), the particle size of the degradable temporary plugging particles is 0.1-1 mm.

9. Use of the degradable temporary plugging particles according to claim 1 or 2 in oil drilling and / or oil and gas field development.

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