Resin plugging agent for anti-CO2-pollution oil-based drilling fluid as well as preparation method and application of resin plugging agent

Abstract

The invention provides a resin plugging agent for an anti-CO2-pollution oil-based drilling fluid as well as a preparation method and application of the resin plugging agent. The resin plugging agent for the anti-CO2 pollution oil-based drilling fluid is prepared from the following raw materials in parts by mass: 10 to 50 parts of styrene, 8 to 20 parts of hydroxyethyl methylacrylate, 1 to 10 parts of acrylic acid long-chain alkyl ester, 0.01 to 2 parts of triallyl isocyanurate, 0.1 to 1.5 parts of an emulsifier, 1 to 5 parts of an initiator and 50 to 200 parts of water. The invention also provides a preparation method of the resin plugging agent. The resin plugging agent provided by the invention can significantly improve the plugging property of the oil-based drilling fluid, has excellent CO2 pollution capacity, can significantly reduce the filter loss of the drilling fluid, effectively plug the filter loss of the drilling fluid in micro-pores, effectively plug the micro-pores, and improve the well wall instability problem of the oil-based drilling fluid.

Description

Technical Field

[0001] The invention belongs to the technical field of drilling fluid treatment agents, and specifically relates to a resin plugging agent for CO2-resistant oil-based drilling fluid and a preparation method and application thereof. Background Art

[0002] At present, my country's deep and ultra-deep oil and gas resources amount to 67.1 billion tons of oil equivalent, accounting for 34% of the country's total oil and gas resources, with huge mining potential. Deep and ultra-deep layers have become the main battlefield for major oil and gas discoveries in my country. The complex formation conditions of deep and ultra-deep layers have put forward higher requirements for drilling fluids in drilling projects. Deep and ultra-deep layers have great burial depths, high formation stress, and the development of micro-cracks and micro-pores, which may induce hydraulic fracturing, aggravate the rock fragmentation of the well wall, and cause the well wall to become unstable; in addition, due to the development of cracks, the drilling fluid invades along the cracks. If it encounters clay minerals, it is easy to cause hydration expansion, aggravating the instability of the well wall.

[0003] Therefore, when drilling deep and ultra-deep layers, it is necessary to add appropriate plugging agents to the drilling fluid. Rigid plugging agents have high strength, poor deformability, and no expansion. They are difficult to effectively adapt to the size and shape of formation pores and microcracks, and it is difficult to form an effective plugging, and the plugging effect is poor. Flexible plugging agents can adapt to the size and shape of formation pores and microcracks, but their own strength is insufficient. They are easily pushed to the deep part of the formation under the action of pressure difference, and cannot form an effective plugging layer around the well wall. In addition, flexible plugging agents are also prone to failure under high temperature and high salt conditions. At present, in the drilling process of deep wells and ultra-deep wells, the problem of CO2 contamination of drilling fluid is often encountered. In formations with high concentrations of CO2, drilling fluid treatment agents are prone to failure, resulting in increased drilling fluid loss. Traditional plugging agents have insufficient performance in this regard.

[0004] Therefore, it is urgent to develop resin plugging agents for drilling fluids suitable for CO2 contamination in deep and ultra-deep oil and gas wells to effectively plug micropores and ensure the stability of the well wall. Summary of the invention

[0005] In view of the shortcomings of the prior art, the present invention provides a resin plugging agent for CO2-resistant oil-based drilling fluid and its preparation method and application. The plugging agent of the present invention can effectively plug micropores in a CO2-polluted environment to ensure the stability of the well wall.

[0006] To achieve the above object, the technical solution of the present invention is as follows:

[0007] A resin plugging agent for CO2-resistant oil-based drilling fluid is prepared by comprising the following raw materials in parts by weight: 10-50 parts of styrene, 8-20 parts of hydroxyethyl methacrylate, 1-10 parts of long-chain alkyl acrylate, 0.01-2 parts of triallyl isocyanurate, 0.1-1.5 parts of emulsifier, 1-5 parts of initiator, and 50-200 parts of water.

[0008] Preferably, according to the present invention, the resin plugging agent for CO2-resistant oil-based drilling fluid is prepared by including the following raw materials in parts by weight: 20-40 parts of styrene, 10-15 parts of hydroxyethyl methacrylate, 2-5 parts of long-chain alkyl acrylate, 0.05-1 part of triallyl isocyanurate, 0.8-1.5 parts of emulsifier, 2-3 parts of initiator, and 80-150 parts of water.

[0009] Preferably, according to the present invention, the resin plugging agent for CO2-resistant oil-based drilling fluid is prepared by including the following raw materials in parts by weight: 30 parts of styrene, 14 parts of hydroxyethyl methacrylate, 3 parts of long-chain alkyl acrylate, 0.08 parts of triallyl isocyanurate, 1 part of emulsifier, 2.4 parts of initiator, and 100 parts of water.

[0010] Preferably according to the present invention, the long-chain alkyl acrylate is hexadecyl acrylate and / or octadecyl acrylate.

[0011] Preferably according to the present invention, the emulsifier is alkyl alcohol polyoxyethylene ether sulfate sodium salt (DNS-328), petroleum sulfonate (WPS) or emulsifier OS (MS-1).

[0012] Preferably according to the present invention, the initiator is an azo initiator, a persulfate initiator or a redox initiator; the azo initiator is azobisisobutyronitrile or azobiscyclohexylcarbonitrile; the persulfate initiator is potassium persulfate or sodium persulfate; the redox initiator includes an oxidant and a reductant, wherein the oxidant is potassium persulfate or sodium persulfate, the reductant is sodium bisulfite, and the mass ratio of the oxidant to the reductant is 1-2:1.

[0013] The preparation method of the above-mentioned resin plugging agent for CO2-resistant oil-based drilling fluid comprises the following steps:

[0014] Add the emulsifier, stir evenly, then add hydroxyethyl methacrylate, long-chain alkyl acrylate, styrene and triallyl isocyanurate, stir to form an oil-in-water pre-emulsion; heat the pre-emulsion to the reaction temperature, then add the initiator to react; after the reaction is completed, dry and crush to obtain a resin plugging agent for CO2-resistant oil-based drilling fluid.

[0015] Preferably, according to the present invention, the initiator is added dropwise into the system in the form of an initiator aqueous solution, the concentration of the initiator aqueous solution is 0.5-1.5 g / mL; the dropping rate of the initiator aqueous solution is 2-3 drops / s.

[0016] Preferably, according to the present invention, the reaction temperature is 75-90°C, the reaction time is 3-6h, and the reaction is carried out under protective gas protection and stirring conditions; preferably, the protective gas is nitrogen or argon, and the stirring speed is 100-600r / min.

[0017] According to the present invention, the resin plugging agent for CO2-resistant oil-based drilling fluid is used as a plugging agent in CO2-contaminated drilling fluid to reduce the filtration loss of the drilling fluid and effectively plug micropores.

[0018] The technical features and beneficial effects of the present invention are as follows:

[0019] 1. The raw materials used in the present invention are easily available, the synthesis process is simple, the reaction conditions are easy to control, and the prepared plugging agent

[0020] Low cost.

[0021] 2. The resin plugging agent of the present invention can significantly improve the plugging property of oil-based drilling fluid, has excellent CO2 pollution ability, can significantly reduce the filtration loss of drilling fluid, effectively plug the filtration loss of micropores, effectively plug the micropores, and improve the wellbore instability problem of oil-based drilling fluid.

[0022] 3. The resin plugging agent of the present invention has a strong adhesive property. It reacts chemically or physically adsorbs with the functional groups on the surface of the rock matrix, forms a strong bond between the matrix and the plugging agent to enhance the plugging effect, and also produces competitive adsorption with CO2, effectively reducing the impact of CO2 on the drilling fluid, thereby reducing the filtration loss of the drilling fluid. In the present invention, the molecular chains of styrene and long-chain alkyl acrylate contain benzene rings and alkyl chains, respectively, which can make the polymer have higher rigidity and hardness; the hydroxyl group in hydroxyethyl methacrylate is a hydrophilic group, which can make the polymer have good hydrophilicity; triallyl isocyanurate can produce a cross-linking effect to enhance the heat resistance of the polymer. The raw material composition and preparation method of the present invention work together as a whole to achieve the excellent effect of the present invention; the replacement of any raw materials, the proportioning and the inappropriateness of the preparation conditions cannot achieve the excellent effect of the present invention. DETAILED DESCRIPTION

[0023] The present invention will be further described below by means of specific examples, but is not limited thereto.

[0024] The experimental methods described in the examples are conventional methods unless otherwise specified; the reagents and materials used are commercially available unless otherwise specified.

[0025] Example 1

[0026] A method for preparing a resin plugging agent for CO2-resistant oil-based drilling fluid comprises the following steps:

[0027] 1) Take 100g of deionized water and add it into a beaker, add 1g of emulsifier OS, and stir at a speed of 500r / min;

[0028] 2) Add 14 g of hydroxyethyl methacrylate, 3 g of hexadecyl acrylate, 30 g of styrene, and 0.08 g of triallyl isocyanurate into the beaker and stir for 30 min to form a stable oil-in-water pre-emulsion;

[0029] 3) Add the above pre-emulsion into a four-necked flask, heat in an oil bath at 80°C, and introduce nitrogen;

[0030] 4) After the four-necked flask is heated to 80°C, an initiator aqueous solution (1.6 g potassium persulfate and 0.8 g sodium sulfite dissolved in 2.5 mL deionized water) is added dropwise at a rate of 2 drops / s, and the mixture is reacted for 4 hours under nitrogen protection and a stirring speed of 200 r / min;

[0031] 5) After the reaction is completed, the product obtained by the reaction is placed in an oven, dried at 100° C. for 24 hours, and crushed to obtain a resin plugging agent for CO2-resistant oil-based drilling fluid.

[0032] Example 2

[0033] A method for preparing a resin plugging agent for CO2-resistant oil-based drilling fluid is as described in Example 1, except that hexadecyl acrylate is replaced by octadecyl acrylate; other steps or conditions are the same as those in Example 1.

[0034] Example 3

[0035] A method for preparing a resin plugging agent for CO2-resistant oil-based drilling fluid is as described in Example 1, except that the emulsifier OS (MS-1) is replaced by petroleum calcium sulfonate; the other steps or conditions are the same as those in Example 1.

[0036] Example 4

[0037] A method for preparing a resin plugging agent for CO2-resistant oil-based drilling fluid is as described in Example 1, except that the initiator is 2.4 g of azobisisobutyronitrile; and the other steps or conditions are the same as in Example 1.

[0038] Example 5

[0039] A method for preparing a resin plugging agent for CO2-resistant oil-based drilling fluid is as described in Example 1, except that the reaction temperature is 90° C.; other steps or conditions are the same as in Example 1.

[0040] Example 6

[0041] A method for preparing a resin plugging agent for CO2-resistant oil-based drilling fluid is as described in Example 1, except that the reaction time is 6 hours; the other steps or conditions are the same as those in Example 1.

[0042] Comparative Example 1

[0043] A method for preparing a resin plugging agent for CO2-resistant oil-based drilling fluid is as described in Example 1, except that hydroxyethyl methacrylate is replaced by methyl methacrylate; other steps or conditions are the same as in Example 1.

[0044] Comparative Example 2

[0045] A method for preparing a resin plugging agent for CO2-resistant oil-based drilling fluid is as described in Example 1, except that triallyl isocyanurate is replaced by diallyl isocyanurate; other steps or conditions are the same as in Example 1.

[0046] Comparative Example 3

[0047] A method for preparing a resin plugging agent for CO2-resistant oil-based drilling fluid is as described in Example 1, except that no styrene is added; other steps or conditions are the same as in Example 1.

[0048] Comparative Example 4

[0049] A method for preparing a resin plugging agent for CO2-resistant oil-based drilling fluid is as described in Example 1, except that hydroxyethyl methacrylate is not added; other steps or conditions are the same as in Example 1.

[0050] Comparative Example 5

[0051] A method for preparing a resin plugging agent for CO2-resistant oil-based drilling fluid is as described in Example 1, except that hexadecyl acrylate is not added; other steps or conditions are the same as those in Example 1.

[0052] Comparative Example 6

[0053] A method for preparing a resin plugging agent for CO2-resistant oil-based drilling fluid is as described in Example 1, except that triallyl isocyanurate is not added; other steps or conditions are the same as in Example 1.

[0054] Test Example 1

[0055] The plugging agents in the embodiments and comparative examples were tested for rheological and filtration properties.

[0056] (1) Sample preparation:

[0057] The drilling fluid base slurry is composed as follows: first, 80 mL of a CaCl2 aqueous solution with a mass fraction of 20% is prepared, 320 mL of 5# white oil is placed in a slurry cup, and 80 mL of the previously prepared CaCl2 aqueous solution is slowly added under continuous stirring at a speed of 6000 r / min, followed by slow addition of a primary emulsifier (sodium stearate) with a mass fraction of 1.5% and an auxiliary emulsifier (sodium carboxymethyl cellulose) with a mass fraction of 2%. After 10 minutes, 3% of organic soil and 3% of CaO are added in sequence. Subsequently, the stirring speed is increased to 9000 r / min, and stirring is continued for 30 minutes to obtain an oil-based drilling fluid base slurry with an oil-water ratio of 4:1. Then, 8 g of the plugging agent in the embodiment or comparative example is added to the above base slurry and CO2 is passed for 1 hour, and the sample is fully stirred on a high-speed stirrer for 10 minutes to obtain the sample; the rheological and filtration properties after aging at room temperature and 180°C are tested.

[0058] (2) Test method:

[0059] Take a certain amount of prepared sample and pour it into the test slurry cup. Use an electronic six-speed viscometer to record θ 600 ,θ 300 , and calculate the values ​​of AV and PV through the formula; use a medium-pressure filter loss meter to record the filtration loss volume.

[0060] Rheology and filtration properties were determined and the test results are shown in Table 1-2.

[0061] Table 1 Rheological and filtration performance test of drilling fluid plugging agent at room temperature

[0062]

[0063] Table 2 Rheological and filtration performance test of drilling fluid plugging agent at 180℃

[0064]

[0065]

[0066] It can be seen from the data in Table 1-2 that the apparent viscosity, plastic viscosity, dynamic shear force and filtration loss of the CO2-contaminated base slurry after adding the plugging agent at room temperature and 180°C after aging are reduced, indicating that under room temperature and high temperature conditions, the plugging agent sample has excellent resistance to CO2 pollution and also has excellent plugging effect.

[0067] In summary, the resin plugging agent for CO2-resistant oil-based drilling fluid of the present invention can meet the needs of CO2-resistant drilling fluid pollution.

[0068] The preferred embodiments of the present invention are described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the technical concept of the present invention, a variety of simple modifications can be made to the technical solution of the present invention, and these simple modifications all belong to the protection scope of the present invention.

[0069] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not further describe various possible combinations.

[0070] In addition, various embodiments of the present invention may be arbitrarily combined, and as long as they do not violate the concept of the present invention, they should also be regarded as the contents disclosed by the present invention.

Claims

1. A resin plugging agent for oil-based drilling fluids that resists CO2 pollution, characterized in that: The preparation method comprises the following raw materials in parts by weight: 10-50 parts of styrene, 8-20 parts of hydroxyethyl methacrylate, 1-10 parts of long-chain alkyl acrylate, 0.01-2 parts of triallyl isocyanurate, 0.1-1.5 parts of emulsifier, 1-5 parts of initiator and 50-200 parts of water.

2. The resin plugging agent for CO2-resistant oil-based drilling fluid according to claim 1, characterized in that: The resin plugging agent for CO2-resistant oil-based drilling fluid is prepared by including the following raw materials in parts by weight: 20-40 parts of styrene, 10-15 parts of hydroxyethyl methacrylate, 2-5 parts of long-chain alkyl acrylate, 0.05-1 part of triallyl isocyanurate, 0.8-1.5 parts of emulsifier, 2-3 parts of initiator, and 80-150 parts of water.

3. The resin plugging agent for CO2-resistant oil-based drilling fluid according to claim 1, characterized in that: The resin plugging agent for CO2-resistant oil-based drilling fluid is prepared by including the following raw materials in parts by weight: 30 parts of styrene, 14 parts of hydroxyethyl methacrylate, 3 parts of long-chain alkyl acrylate, 0.08 parts of triallyl isocyanurate, 1 part of emulsifier, 2.4 parts of initiator, and 100 parts of water.

4. The resin plugging agent for CO2-resistant oil-based drilling fluid according to claim 1, characterized in that: The long-chain alkyl acrylate is hexadecyl acrylate and / or octadecyl acrylate.

5. The resin plugging agent for CO2-resistant oil-based drilling fluid according to claim 1, characterized in that: The emulsifier is alkyl alcohol polyoxyethylene ether sulfate sodium salt, petroleum sulfonate or emulsifier OS.

6. The resin plugging agent for CO2-resistant oil-based drilling fluid according to claim 1, characterized in that: The initiator is an azo initiator, a persulfate initiator or a redox initiator; the azo initiator is azobisisobutyronitrile or azobiscyclohexylcarbonitrile; the persulfate initiator is potassium persulfate or sodium persulfate; the redox initiator includes an oxidant and a reductant, wherein the oxidant is potassium persulfate or sodium persulfate, the reductant is sodium bisulfite, and the mass ratio of the oxidant to the reductant is 1-2:

1.

7. The method for preparing the resin plugging agent for CO2-resistant oil-based drilling fluid according to claim 1 comprises the following steps: Add the emulsifier, stir evenly, then add hydroxyethyl methacrylate, long-chain alkyl acrylate, styrene and triallyl isocyanurate, stir to form an oil-in-water pre-emulsion; heat the pre-emulsion to the reaction temperature, then add the initiator to react; after the reaction is completed, dry and crush to obtain a resin plugging agent for CO2-resistant oil-based drilling fluid.

8. The method for preparing the resin plugging agent for CO2-resistant oil-based drilling fluid according to claim 7, characterized in that: The initiator is added dropwise into the system in the form of an initiator aqueous solution, the concentration of the initiator aqueous solution is 0.5-1.5 g / mL; the dropping rate of the initiator aqueous solution is 2-3 drops / s.

9. The method for preparing the resin plugging agent for CO2-resistant oil-based drilling fluid according to claim 7, characterized in that: The reaction temperature is 75-90° C., the reaction time is 3-6 hours, and the reaction is carried out under protective gas protection and stirring conditions; preferably, the protective gas is nitrogen or argon, and the stirring speed is 100-600 r / min.

10. The use of the resin plugging agent for CO2-resistant oil-based drilling fluid according to claim 1, characterized in that: It is used as a plugging agent in CO2-contaminated drilling fluid to reduce the filtration loss of drilling fluid and effectively plug micropores.

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