A positive and negative bidirectional high-pressure plugging agent and its preparation method

Abstract

The present invention discloses a positive and negative bidirectional high-pressure plugging agent and a preparation method thereof, comprising the following components in parts by weight: 100 parts of a base material, 40-45 parts of a filling material, 5-15 parts of a curing agent, 5-10 parts of a curing aid, 20-25 parts of an adhesive, and 15-20 parts of rigid particles; the base material is a water-absorbing and expanding material, and the filling material comprises 10-15 parts of an irregular granular material, 10-15 parts of a shape memory alloy, 10-15 parts of expanded graphite, and 10-15 parts of a fiber; the preparation method is as follows: S1, the base material is subjected to water absorption and expansion. The filling material, curing agent, curing aid and the water-absorbed base material are uniformly mixed in step S2; the mixture of step S1 is dried and crushed; S3, polyvinyl alcohol and acrylamide are prepared into a protective solution by a free radical synthesis method; S4, the surface of the mixture obtained in step S2 is coated with the protective solution prepared in step S3 and cured; S5, the surface of the cured mixture containing the protective layer obtained in step S4 is coated with rigid particles and adhesive, which can improve the bidirectional pressure bearing capacity of the crack in both positive and negative directions and avoid spitting back.

Description

Technical Field

[0001] The invention discloses a forward and reverse bidirectional high-pressure plugging agent and a preparation method thereof, belonging to the technical field of oil and gas development. Background Art

[0002] As oil and gas exploration and development expand into deeper, unconventional areas, conventional oil and gas development technologies face numerous drilling challenges, particularly in fractured formations where severe lost circulation not only prolongs drilling cycles but also results in significant losses of drilling fluid and plugging materials, potentially leading to complex accidents such as stuck pipe, overflow, and even blowouts. Currently, bridging plugging, high-water-loss plugging, and polymer gel plugging are the main methods used to address fractured leakage in deep formations. However, due to the depth of the formation, the leakage characteristics may not be obvious, resulting in a low one-time success rate for plugging. Multiple trial plugging methods are required to explore the optimal plugging method, resulting in significant waste. Among them, bridging plugging is one of the most commonly used plugging methods in oil fields. However, in most cases, the compatibility between the plugging materials and the cracks is low, resulting in insignificant plugging effects. Although high water loss plugging has good graduation ability, it has serious backflow problems and a high formation leakage rate. Polymer gel plugging is currently a more advanced plugging technology. Cross-linked polymers are used for plugging, but the cross-linking time cannot be controlled, and the final setting time in complex cracks is difficult to determine, which can easily cause oil-based drilling fluid leakage and economic losses. Therefore, it is currently necessary to ensure that the high pressure-bearing capacity of conventional drilling fluid while drilling plugging systems can be achieved, while also improving the drilling fluid's anti-gas intrusion effect while drilling. It is necessary to develop an efficient while drilling plugging system and improve the plugging technology with reverse pressure-bearing capacity. Summary of the Invention

[0003] The invention discloses a positive and negative bidirectional high-pressure plugging agent and a preparation method thereof, which overcomes the shortcomings of the prior art, can achieve true reverse pressure bearing, can effectively eliminate the pressure difference between the formation and the internal space of the crack, and avoid the occurrence of spitting back.

[0004] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0005] A bidirectional high-pressure plugging agent comprising the following components in parts by weight:

[0006] 100 parts base material, 40-45 parts filler, 5-15 parts curing agent, 5-10 parts curing aid, 20-25 parts adhesive, 15-20 parts rigid particles;

[0007] The substrate is a water-swelling material, and the filling material includes 10-15 parts of irregular granular material, 10-15 parts of shape memory alloy, 10-15 parts of expanded graphite, and 10-15 parts of fiber.

[0008] The water-swelling material is sodium polyacrylate resin, the curing agent is phthalic anhydride, the curing aid is 2-ethyl-4-methylimidazole, and the irregular particle materials are limestone and quartz sand.

[0009] The limestone and quartz sand are compounded in a 1:1 ratio.

[0010] The shape memory alloy is a NiTi shape memory alloy or a Cu-based shape memory alloy and a Fe-based shape memory alloy or a combination of the above three materials.

[0011] The length of the shape memory alloy is no more than 1 mm.

[0012] The fiber is polybutylene terephthalate fiber or polytrimethylene terephthalate fiber or short-staple sepiolite fiber or a combination of the three materials, and the fiber length is 0.01-0.1 mm.

[0013] The adhesive is polyethylene glycol 400 or modified epoxy resin or modified emulsified resin or a combination of the three materials.

[0014] The rigid particle material is walnut shell, and the particle size is 50-200 μm.

[0015] The preparation method of the plugging agent is as follows:

[0016] S1. Perform water absorption operation on the base material, and evenly mix the filling material, curing agent, curing aid and the base material after water absorption;

[0017] S2, drying and crushing the mixture of step S1;

[0018] S3, preparing a protective solution by using a free radical synthesis method with polyvinyl alcohol and acrylamide;

[0019] S4, coating the surface of the mixture obtained in step S2 with the protective solution prepared in step S3 and curing the mixture;

[0020] S5, coating the surface of the solidified mixture containing the protective layer obtained in step S4 with rigid particles and adhesive.

[0021] The crushed particles of the mixture obtained in step S2 have a particle size of 0.05-0.3 mm, the protective agent coating thickness is 0.1-0.2 mm, and the rigid particles and adhesive coating thickness is 0.1-0.3 mm.

[0022] Compared with the prior art, the present invention has the following beneficial effects.

[0023] 1. After the prepared plugging material enters the crack along with the drilling fluid, the temperature of the formation crack will be relatively high, and the first coating layer of the plugging material will gradually melt, creating a gap between the second coating layer and the core. Under the action of ground stress, the second coating layer begins to disintegrate and collapse inward. The water-absorbing resin serving as the core wraps around various filler materials. The shape memory alloy will also return to its original shape due to the increase in temperature, stretching the second coating layer. The water-absorbing resin is gradually exposed and comes into contact with external water (including water in the drilling fluid and formation water). After absorbing water, the core expands and deforms, thereby filling the internal space of the crack. Another part of the plugging material, because the second coating layer has not collapsed or has not completely collapsed, acts as a rigid particle bridge within the crack. Among them, for the plugging material whose second coating layer has partially collapsed, free water from the outside enters the material through the cracks in the coating layer, causing the core material to expand and support the coating layer, further enhancing the overall structural strength of the material.

[0024] 2. As the plugging material sinks into the formation along with the drilling fluid, it will penetrate into the surface of the crack to form a filling layer, and its interior will also be completely filled, eliminating the pressure difference between the formation and the internal space of the crack. The new mixture of various filling materials re-wrapped will expand and partially solidify, which will enhance the friction between the plugging section and the inner wall of the crack, improve the positive and negative bidirectional pressure bearing capacity of the crack, and avoid the occurrence of spitting. DETAILED DESCRIPTION

[0025] The present invention provides a bidirectional high-pressure plugging agent, comprising the following components in parts by weight:

[0026] 100 parts base material, 40-45 parts filler, 5-15 parts curing agent, 5-10 parts curing aid, 20-25 parts adhesive, 15-20 parts rigid particles;

[0027] The base material is a water-absorbing and expanding material, and the filling material comprises 10-15 parts of irregular particle material, 10-15 parts of shape memory alloy, 10-15 parts of expanded graphite, and 10-15 parts of fiber.

[0028] The water-swelling material is sodium polyacrylate resin. The chemical formula of sodium polyacrylate resin is that it is made of acrylic acid and its esters as raw materials and is obtained by aqueous solution polymerization. The solid product is white granular and has high water absorption.

[0029] The curing agent is phthalic anhydride, and the preferred curing aid is 2-ethyl-4-methylimidazole, which is compatible with the modified epoxy resin. The curing time can be adjusted by the amount of curing agent to ensure that the plugging agent does not solidify during the sinking process, sinks smoothly to the leakage site and solidifies quickly at high temperature.

[0030] The irregular granular materials are limestone and quartz sand. The limestone and quartz sand are compounded in a 1:1 ratio. The particle size distribution of the limestone and quartz sand is between 50, 100, 200 and 300 μm. The particle size combination ratio is 1:1.5:1.5:1, and the weight proportion in various filling materials is 20-25%. Among them, the main component of limestone is calcium carbonate (CaCO3); quartz sand is quartz particles obtained by crushing quartz stone. Quartz stone is a non-metallic mineral, a hard, wear-resistant, chemically stable silicate mineral, and its main component is silicon dioxide.

[0031] The shape memory alloy is a NiTi shape memory alloy or a Cu-based shape memory alloy and an Fe-based shape memory alloy or a combination of the above three materials, preferably a NiTi shape memory alloy or a Cu-based shape memory alloy, whose length does not exceed 1 mm and the weight proportion of the filler materials is 20-25%. Among them, the NiTi shape memory alloy has the advantages of good mechanical properties, oxidation resistance, corrosion resistance and good biocompatibility. Compared with the NiTi shape memory alloy, the Cu-based shape memory alloy is low in price and easy to process.

[0032] The expanded graphite is selected from materials with a rebound efficiency of not less than 80% after 5 minutes of pressure application at 30 MPa, and a rebound modulus of not less than 60% after 48 hours of pressure application at 30 MPa, and accounts for 20-25% by weight of the various filling materials. Among them, the graphite-based granular material is resistant to high temperatures and has good toughness and a certain degree of elasticity. It is not easily broken under extrusion and impact, and acts as a pressure buffer in the plugging layer, preventing the particles in the plugging layer from being directly impacted and broken during downhole pressure fluctuations.

[0033] The fiber is polybutylene terephthalate fiber or polytrimethylene terephthalate fiber or short-staple sepiolite fiber or a combination of the above three materials. The fiber length is 0.01-0.1 mm and the weight proportion in various filling materials is 25-30%. Among them, the fiber mainly plays a traction and connection role in the pressure-bearing plugging slurry, and it is necessary to select the specific length and width mentioned above. If the aspect ratio is too large, the fiber is easy to agglomerate during the stirring process, resulting in poor dispersion performance. If the aspect ratio is too small, its traction and connection ability will be weak.

[0034] The adhesive is polyethylene glycol 400 or modified epoxy resin or modified emulsified resin or a combination of the above three materials, preferably modified epoxy resin or modified emulsified resin.

[0035] The rigid particle material is selected from one or more of walnut shell, quartz sand, calcite and talc, more preferably walnut shell, and has a particle size of 50 to 200 μm.

[0036] The preparation method of the plugging agent is as follows:

[0037] S1. Perform water absorption operation on the base material, and evenly mix the filling material, curing agent, curing aid and the base material after water absorption;

[0038] S2. Place the mixture from step S1 in an oven at 50-55°C for 4-6 hours, and then crush it using a crusher to form kernels;

[0039] S3, preparing a protective solution by using a free radical synthesis method with polyvinyl alcohol and acrylamide;

[0040] S4, fully covering the surface of the core obtained in step S2 with the protective solution prepared in step S3 and taking it out for curing;

[0041] S5. Roll the cured mixture containing the protective layer obtained in step S4 in the mixture of rigid particles and adhesive to ensure that it is completely covered, take it out and place it in a curing box for curing and drying to obtain a bidirectional high-pressure-bearing cured plugging material.

[0042] The crushed particles of the mixture obtained in step S2 have a particle size of 0.05-0.3 mm, the protective agent coating thickness is 0.1-0.2 mm, and the rigid particles and adhesive coating thickness is 0.1-0.3 mm.

[0043] Polyvinyl alcohol (PVA) is an organic compound that appears as a white, flaky, or powdery solid. It is odorless and soluble in water. A key chemical raw material, PVA is stable at room temperature and pressure but should be avoided in the presence of heat, open flames, or high temperatures. It is hygroscopic and does not melt when heated. It decomposes at approximately 150°C, becoming yellowish due to water loss. It is resistant to corrosion by acids, alkalis, grease, and lubricants.

[0044] The plugging agent prepared by this method has a three-layer structure, which mainly uses various filling materials wrapped by the core water-absorbing and expanding material to perform the plugging effect. The first wrapping layer and the second wrapping layer are to allow the plugging core to play a role when it reaches the plugging section.

[0045] The test method is as follows:

[0046] A high-temperature and high-pressure plugging instrument was used to conduct a high-temperature and pressure plugging evaluation on the prepared positive and negative bidirectional high-pressure plugging agent. The crack model used a steel block with a diameter of 10 cm and a height of 20 cm and a groove in the middle. It was sealed with cement to simulate the leakage layer phenomenon.

[0047] Base slurry formula: 5% bentonite + 0.5% Na2CO3 + 0.25% CMC (the amount of base slurry used in the experiment is 500mL / time); add 5% to 10% of the forward and reverse bidirectional high-pressure plugging material prepared in the experiment of the present invention to the base slurry, stir evenly, and obtain the plugging slurry. Use a high-temperature and high-pressure plugging instrument, connect the pipeline, install the crack steel block, pour the above-prepared plugging slurry into the device for sealing, increase the confining pressure to 10MPa, raise the temperature to 180°C, and use a displacement pump to squeeze the plugging slurry into the simulated crack in the forward and reverse directions, observe and record the amount of slurry lost and filtered out. After the experiment, wait until the temperature drops to room temperature, take out the crack module, and observe the plugging effect of the material in the crack.

[0048] The plugging material prepared by this technology was used as the sample control group Q1, the shape memory alloy type in the filling material was changed as the comparison group Q2, the fiber type in the filling material was changed as the control group Q3, the shape memory alloy and fiber types in the filling material were changed as the control group Q4, the adhesive type was changed as the control group Q5, the shape memory alloy and adhesive types in the filling material were changed as the control group Q6, the fiber and adhesive types in the filling material were changed as the control group Q7, the shape memory alloy, fiber and adhesive types in the filling material were changed as the control group Q8, the fiber and adhesive types in the filling material were changed, and the shape memory alloy was not wrapped as the control group Q9. 15 parts of 10-20 mesh calcium carbonate particles, 10 parts of 40-80 mesh calcium carbonate particles, 30 parts of 40-80 mesh walnut shell particles, 45 parts of 120-325 mesh calcium carbonate powder, and 3 parts of 3 mm long polypropylene fibers were used as the comparison group Q10, and plugging experiments were carried out respectively. The structures are shown in the following table.

[0049] Serial number formula Positive bearing pressure value / MPa Reverse pressure value / MPa Blocking length / cm 1 Base slurry + 8% Q1 7.2 3.4 4.2 2 Base slurry + 8% Q2 7.0 3.2 4.1 3 Base slurry + 8% Q3 7.6 3.6 4.5 4 Base slurry + 8% Q4 7.0 3.4 4.3 5 Base slurry + 8% Q5 8.6 4.2 5.6 6 Base slurry + 8% Q6 7.8 4.0 5.1 7 Base slurry + 8% Q7 9.4 4.6 6.7 8 Base slurry + 8% Q8 8.4 4.4 6.5 9 Base slurry + 8% Q9 6.8 2.8 3.0 10 Base paste + 8% Q10 4.4 0.6 0.2

[0050] Experimental data show that the forward and reverse bidirectional high-pressure plugging material of the present invention can effectively seal cracks, forming a dense plugging layer in the cracks. The formed plugging layer can withstand a pressure of more than 7 MPa at a high temperature of 180°C, and can withstand a pressure of more than 3 MPa in the reverse direction. Traditional plugging materials can only temporarily block cracks, but will be destroyed as the pressure increases, and their pressure-bearing capacity is far inferior to the plugging agent prepared by the present invention.

[0051] The embodiments of the present invention are described in detail above, but the present invention is not limited to the above embodiments. Various changes can be made within the knowledge of ordinary technicians in this field without departing from the scope of the present invention.

Claims

1. A bidirectional high-pressure plugging agent, characterized in that: The invention comprises the following components in parts by weight: 100 parts base material, 40-45 parts filler, 5-15 parts curing agent, 5-10 parts curing aid, 20-25 parts adhesive, 15-20 parts rigid particles; The substrate is a water-swelling material, and the filling material includes 10-15 parts of irregular granular material, 10-15 parts of shape memory alloy, 10-15 parts of expanded graphite, and 10-15 parts of fiber; The water-swellable material is sodium polyacrylate resin; the irregular particle material is limestone and quartz sand; the shape memory alloy is NiTi shape memory alloy, Cu-based shape memory alloy, Fe-based shape memory alloy, or a combination of the above three materials; the fiber is polybutylene terephthalate fiber, polypropylene terephthalate fiber, or short-staple sepiolite fiber, or a combination of the above three materials; the adhesive is polyethylene glycol 400, modified epoxy resin, or modified emulsified resin, or a combination of the above three materials.

2. A positive and negative bidirectional high pressure plugging agent according to claim 1, characterized in that: The curing agent is phthalic anhydride, and the curing aid is 2-ethyl-4-methylimidazole.

3. The positive and negative bidirectional high pressure plugging agent according to claim 1, characterized in that: The limestone and quartz sand are compounded in a 1:1 ratio.

4. The positive and negative bidirectional high pressure plugging agent according to claim 1, characterized in that: The length of the shape memory alloy is no more than 1 mm.

5. The positive and negative bidirectional high pressure plugging agent according to claim 1, characterized in that: The fiber length is 0.01-0.1 mm.

6. The positive and negative bidirectional high pressure plugging agent according to claim 1, characterized in that: The rigid particle material is walnut shell, and the particle size is 50-200 μm.

7. The positive and negative bidirectional high pressure plugging agent according to claim 1, characterized in that: The preparation method of the plugging agent is as follows: S1. Perform water absorption operation on the base material, and evenly mix the filling material, curing agent, curing aid and the base material after water absorption; S2, drying and crushing the mixture of step S1; S3, preparing a protective solution by using a free radical synthesis method with polyvinyl alcohol and acrylamide; S4, coating the surface of the mixture obtained in step S2 with the protective solution prepared in step S3 and curing the mixture; S5, coating the surface of the solidified mixture containing the protective layer obtained in step S4 with rigid particles and an adhesive.

8. The forward and reverse bidirectional high-pressure plugging agent according to claim 7, characterized in that: The crushed particles of the mixture obtained in step S2 have a particle size of 0.05-0.3 mm, and the thickness of the rigid particles and the adhesive coating is 0.1-0.3 mm.