A consolidated plugging material for oil-based drilling fluids and a method of making and use thereof

Abstract

The present application relates to a kind of oil-based drilling fluid consolidation plugging material and its preparation method and purposes, the oil-based drilling fluid consolidation plugging material includes: oil-based gel, consolidation material and crosslinking agent;The oil-based gel includes: base oil, castor oil-based prepolymers containing end-NCO group and lipophilic nanosilica;The consolidation material includes oil-based drilling cuttings powder, lime and organic soil.The oil-based drilling fluid consolidation plugging material provided by the present application, by using the mixed system of oil-based gel, solid material and crosslinking agent, can form the plugging layer with oil-based gel as main and solid material as auxiliary during use, can effectively improve the plugging success rate of oil-based drilling fluid loss, and the strength of solidified layer after solidification can reach more than 5MPa.

Description

Technical Field

[0001] This invention relates to the field of oil-based drilling fluid technology for oil drilling, specifically to a consolidation and plugging material for oil-based drilling fluid, its preparation method, and its applications. Background Technology

[0002] Currently, due to the well-developed bedding fractures in shale formations, well leakage problems with oil-based drilling fluids are widespread and have remained unresolved, posing a significant challenge to the efficient development of shale oil and gas. Current methods for addressing oil-based drilling fluid leakage primarily utilize water-based drilling fluid plugging techniques. Initially, drilling-while-drilling plugging and bridging slurry plugging were the main approaches, but these proved ineffective, leading to the shift to cement plugging.

[0003] For example, CN113898313A discloses a method for preventing collapse and plugging leakage in shale gas horizontal wells using oil-based drilling fluid. The method includes the following steps: identifying the leakage zone to confirm the occurrence of leakage; determining the depth of the leakage zone and measuring the leakage rate; if the leakage rate indicates seepage, directly adding seepage plugging material to the oil-based drilling fluid and maintaining circulation, while the drill bit continues drilling normally and the decrease in leakage is observed; if the leakage rate indicates a medium or large leakage, stopping the mud pump and halting drilling; preparing new oil-based mud in a separate mud tank; adding the leakage plugging material and mixing thoroughly to obtain the plugging slurry; for medium-sized leakage, not retracting the drill bit, directly positioning the drill bit at or below the leakage zone; for large leakage, retracting the drill pipe, repeatedly activating the bypass valve above the drill bit, then lowering the drill bit to the leakage zone and dropping a ball to open the bypass outlet; starting the mud pump and injecting the plugging slurry into the leakage zone for sealing. This method allows for targeted leakage plugging with a high success rate and excellent pressure resistance.

[0004] However, due to a series of reasons, such as the oleophilic wetting of the fracture surface, the hydrophilic and oleophobic nature of the plugging material, and the mismatch between the size of the plugging material and the fracture, plugging while drilling and bridging slurry plugging solutions are often ineffective. Cement has poor resistance to oil-based drilling fluid contamination; once mixed with oil-based drilling fluid, its consolidation effect is poor, and the success rate of plugging is far lower than that of water-based drilling fluid. Ultimately, when the above methods fail to work after repeated attempts, the oil-based drilling fluid is often replaced with a water-based drilling fluid before plugging operations are carried out, increasing the lost time and greatly delaying the project schedule.

[0005] Therefore, developing a consolidation plugging material suitable for oil-based drilling fluids is of great significance for the efficient development of shale oil and gas, addressing the shortcomings of existing technologies, especially the poor compatibility of existing plugging materials with oil-based drilling fluids, mismatch with fracture size, and difficulty in adhering to the surface of oil-wetted fractures to form an effective plugging layer. Summary of the Invention

[0006] In view of the problems existing in the prior art, the purpose of the present invention is to provide a solidified plugging material for oil-based drilling fluid, its preparation method and application. When oil-based drilling fluid leakage occurs, the plugging material provided by the present invention can be pumped into the leakage fracture and solidify at a reasonable temperature and time to form a plugging layer with sufficient strength and strong retention ability on the oil-wetted surface. This effectively improves the success rate of plugging oil-based drilling fluid leakage, reduces economic losses and the loss of manpower and material resources caused by multiple plugging operations, and solves the problems of poor compatibility with oil-based drilling fluid, mismatch with fracture size, and difficulty in forming an effective plugging layer on the oil-wetted fracture surface of existing plugging materials.

[0007] To achieve this objective, the present invention adopts the following technical solution:

[0008] In a first aspect, the present invention provides a consolidation and plugging material for oil-based drilling fluids, the oil-based drilling fluid consolidation and plugging material comprising: an oil-based gel, a consolidation material, and a crosslinking agent;

[0009] The oil-based gel comprises: base oil, castor oil-based prepolymer with terminal -NCO groups, and oleophilic nano-silica;

[0010] The consolidation materials include oil-based drill cuttings, lime, and organic clay.

[0011] The solidified plugging material for oil-based drilling fluid provided by this invention, by adopting a mixed system of oil-based gel, solid material and crosslinking agent, can form a plugging layer with oil-based gel as the main component and solid material as the auxiliary component during use, which can effectively improve the plugging success rate of oil-based drilling fluid leakage, and the strength of the solidified layer after curing can reach more than 5MPa.

[0012] As a preferred technical solution of the present invention, the oil-based drilling fluid consolidation and plugging material comprises, by weight, 30-70 parts of oil-based gel, 30-70 parts of consolidation material and 2-7 parts of crosslinking agent.

[0013] As a preferred embodiment of the present invention, the oil-based gel comprises, by weight: 100-110 parts of base oil, 40-80 parts of castor oil-based prepolymer containing terminal -NCO groups, and 5-10 parts of oleophilic nano-silica.

[0014] As a preferred embodiment of the present invention, the base oil includes base oil for oil-based drilling fluids.

[0015] Preferably, the base oil includes one or a combination of at least two of the following: 0# diesel oil, 3# white oil, 5# white oil, gas-derived oil, linear paraffin, or linear α-olefin.

[0016] Preferably, the castor oil-based prepolymer containing terminal -NCO groups is prepared by reacting castor oil, isocyanate monomers and an initiator.

[0017] Preferably, the purity of the castor oil is >70%.

[0018] Preferably, the isocyanate monomer includes one or a combination of at least two of toluene diisocyanate, isophorone diisocyanate, diphenylmethane diisocyanate, dicyclohexylmethane diisocyanate, hexamethylene diisocyanate, or lysine diisocyanate.

[0019] Preferably, the initiator comprises one or a combination of at least two of azobisisobutyronitrile, zinc isooctanoate, tin isooctanoate, bismuth isooctanoate, or dibutyltin dilaurate.

[0020] Preferably, the average particle size of the oleophilic nano-silica is 10-300 nm.

[0021] As a preferred technical solution of the present invention, the consolidation material comprises, by weight: 50-80 parts of oil-based drill cuttings powder, 10-20 parts of lime, and 10-20 parts of organic soil.

[0022] As a preferred embodiment of the present invention, the crosslinking agent includes one or a combination of at least two of the following: trimethylolpropane, 2-ethyl-4-methylimidazole, 2-phenylimidazole, 2-isopropylimidazole, tetrachlorophthalic anhydride, hexahydrophthalic anhydride, diethylenetriamine, triethylenetetramine, dimethylaminopropylamine, or diethylaminopropylamine.

[0023] As a preferred embodiment of the present invention, the oil-based drilling fluid consolidation and plugging material further includes 3-10 parts of retarder by weight percentage.

[0024] Furthermore, to prevent the solidification of oil-based drilling fluid plugging materials during use, a certain amount of retarder can be introduced into the oil-based drilling fluid plugging materials to prevent premature solidification. Furthermore, to prevent use in environments with higher temperatures, such as >140℃, a high-temperature retarder can be introduced to prevent the oil-based drilling fluid plugging materials from solidifying too quickly under high-temperature conditions.

[0025] Preferably, the retarder is a high-temperature retarder.

[0026] Preferably, the high-temperature retarder includes one or a combination of at least two of diethyl malonate, methyl ethyl ketone oxime, acetone oxime, or caprolactam.

[0027] In a second aspect, the present invention provides a method for preparing a solidified plugging material for oil-based drilling fluid as described in the first aspect. The preparation method includes adding a solidifying material and a crosslinking agent to an oil-based gel according to a formula and stirring to obtain a solidified plugging material suitable for oil-based drilling fluid.

[0028] As a preferred technical solution of the present invention, when the oil-based drilling fluid solidification and plugging material contains a retarder, the retarder is also added to the oil-based gel and stirred.

[0029] Preferably, the stirring rate is 600-800 r / min.

[0030] Preferably, the stirring time is 30-50 minutes.

[0031] Thirdly, the present invention provides the use of the solidified plugging material for oil-based drilling fluid as described in the first aspect, wherein the use is to seal the leakage of oil-based drilling fluid during the drilling process using the solidified plugging material for oil-based drilling fluid.

[0032] Compared with existing technical solutions, the present invention has the following beneficial effects:

[0033] (1) The oil-based gel in the consolidation and plugging material of the present invention contains a castor oil-based prepolymer with terminal -NCO groups. The prepolymer contains castor oil blocks, which gives the consolidation and plugging material good oleophilicity and good compatibility with oil-based drilling fluids. It still has a good consolidation effect when mixed with oil-based drilling fluids and has good retention ability on the surface of oil-wetted fractures. When combined with solid materials and gelling agents, it can effectively improve the consolidation strength and improve the pressure bearing capacity.

[0034] (2) The retarder of the present invention can make the solidified sealing material flow before it is pumped to the leak layer, preventing premature solidification and ensuring sufficient safe construction time; the selection of high temperature retarder can avoid the solidification of the sealing material when sealing under high temperature conditions.

[0035] (3) The solidified plugging material of the present invention is a mixed system composed of oil-based gel, solid material, crosslinking agent and retarder. After being pumped to the leaking layer, it can form a plugging layer with oil-based gel as the main component and solid material as the auxiliary component. It has the characteristics of good gelation controllability, high pressure resistance and good compatibility with oil-based drilling fluid, which can effectively improve the plugging success rate of oil-based drilling fluid leakage. Detailed Implementation

[0036] To better illustrate the present invention and facilitate understanding of its technical solutions, typical but non-limiting embodiments of the present invention are as follows:

[0037] This embodiment provides a consolidation and plugging material for oil-based drilling fluids, wherein the oil-based drilling fluid consolidation and plugging material comprises, by weight, the following:

[0038] 30-70 parts of oil-based gel, 30-70 parts of consolidating material and 2-7 parts of crosslinking agent.

[0039] Specifically, the oil-based gel in the oil-based drilling fluid consolidation and plugging material is 30-70 parts by weight, for example, 30 parts, 40 parts, 50 parts, 60 parts or 70 parts, but not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0040] Specifically, the solidifying material in the oil-based drilling fluid solidifying and plugging material is 30-70 parts by weight, for example, 30 parts, 40 parts, 50 parts, 60 parts or 70 parts, etc., but not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0041] Specifically, the crosslinking agent in the oil-based drilling fluid consolidation and plugging material is 2-7 parts by weight, for example, 2 parts, 3 parts, 4 parts, 5 parts, 6 parts or 7 parts, but not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0042] The oil-based gel comprises, by weight, 100-110 parts of base oil, 40-80 parts of castor oil-based prepolymer containing terminal -NCO groups, and 5-10 parts of oleophilic nano-silica.

[0043] For example, the preparation process of the oil-based gel can be selected as follows: according to the formula, base oil, castor oil-based prepolymer containing terminal -NCO groups and lipophilic nano-silica are mixed together. During the mixing process, the stirring speed is controlled at 300-500 r / min and the stirring time is 30-40 min. Specifically, the stirring speed can be selected as 300 r / min, 350 r / min, 400 r / min, 450 r / min or 500 r / min, etc., and the stirring time can be selected as 30 min, 32 min, 34 min, 36 min, 38 min or 40 min, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0044] Specifically, the base oil in the oil-based gel is 100-110 parts by weight, for example, 100 parts, 102 parts, 104 parts, 106 parts, 108 parts or 110 parts, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0045] Specifically, the castor oil-based prepolymer containing terminal -NCO groups in the oil-based gel is 40-80 parts by weight, for example, 40 parts, 50 parts, 60 parts, 70 parts or 80 parts, etc., but not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0046] Specifically, the oil-based gel contains 5-10 parts by weight of lipophilic nano-silica, for example, 5, 6, 7, 8, 9, or 10 parts, but is not limited to the listed values; other unlisted values ​​within this range are also applicable. Adding lipophilic nano-silica to the base oil can effectively promote the gelation and solidification of the oil-based gel.

[0047] The base oil includes oil-based drilling fluid base oil, such as one or a combination of at least two of the following: 0# diesel, 3# white oil, 5# white oil, gas-to-oil, linear paraffin, or linear α-olefin.

[0048] In this invention, the gas-to-oil process can be selected from gas-to-oil processes used in the preparation of drilling fluids, such as Saraline 185V produced by Shell.

[0049] In this invention, the number of carbon atoms in the linear paraffin can be controlled to be 16-22.

[0050] In this invention, the number of carbon atoms in the linear α-olefin can be controlled to be 12-22.

[0051] The castor oil-based prepolymer with terminal -NCO groups is prepared by reacting castor oil, isocyanate monomers, and an initiator. Specifically, the preparation process of the castor oil-based prepolymer with terminal -NCO groups is as follows:

[0052] (1) Add castor oil and isocyanate monomers into the reaction vessel and stir until homogeneous.

[0053] (2) Maintain stirring speed and add initiator dropwise to the reaction vessel under a protective atmosphere, controlling the dropwise addition to 30-45 minutes.

[0054] (3) Raise the temperature to the reaction temperature and keep it warm for a certain time to obtain castor oil-based prepolymer with terminal -NCO groups.

[0055] In step (1), the molar ratio of the hydroxyl group of castor oil to the -NCO group of isocyanate monomer in the mixture of castor oil and isocyanate monomer is 1:(1-3), for example, it can be 1:1, 1:1.5, 1:2, 1:2.5 or 1:3, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0056] In step (1), the stirring rate is 200-500 r / min and the stirring time is 30-60 min. Specifically, the stirring rate can be selected as 200 r / min, 300 r / min, 400 r / min or 500 r / min, etc., and the stirring time can be selected as 30 min, 40 min, 50 min or 60 min, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0057] In step (2), the mass of the initiator is 0.1-1% of the total mass of castor oil and isocyanate monomers, for example, 0.1%, 0.2%, 0.4%, 0.6%, 0.8%, or 1%, but not limited to the listed values; other unlisted values ​​within this range are also applicable. The protective atmosphere during the addition of the initiator can be an inert atmosphere or a gas that does not react with the material system, such as nitrogen, helium, neon, or argon. Furthermore, the added initiator is a solution with alcohol as the solvent and the initiator as the solute, and the initiator's mass percentage is 10-15%.

[0058] In step (3), the reaction temperature is 40-100℃ and the reaction time is 1-6h. Specifically, the reaction temperature can be controlled at 40℃, 50℃, 60℃, 70℃, 80℃, 90℃ or 100℃, etc. The reaction is carried out at the reaction temperature within this range, and the reaction time can be controlled at 1h, 2h, 3h, 4h, 5h or 6h, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0059] Specifically, the castor oil has a purity >70%, and its molecular structure is shown below. The presence of castor oil molecular blocks in the prepolymer effectively improves its affinity with the oil phase. Higher purity of the castor oil is preferred, ideally >80%, and more preferably >85%.

[0060]

[0061] Specifically, the isocyanate monomers include one or a combination of at least two of toluene diisocyanate, isophorone diisocyanate, diphenylmethane diisocyanate, dicyclohexylmethane diisocyanate, hexamethylene diisocyanate, or lysine diisocyanate.

[0062] Specifically, the initiator includes one or a combination of at least two of azobisisobutyronitrile, zinc isooctanoate, tin isooctanoate, bismuth isooctanoate, or dibutyltin dilaurate.

[0063] Specifically, the average particle size of the oleophilic nano-silica is 10-300nm, for example, it can be 10nm, 20nm, 40nm, 60nm, 80nm, 100nm, 120nm, 140nm, 160nm, 180nm, 200nm, 220nm, 240nm, 260nm, 280nm or 300nm, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also applicable. Preferably, it is 15-150nm, and more preferably, it is 20-80nm.

[0064] The consolidation material comprises, by weight, 50-80 parts of oil-based drill cuttings powder, 10-20 parts of lime, and 10-20 parts of organic soil.

[0065] Specifically, the oil-based drill cuttings powder in the consolidation material is 50-80 parts by weight, for example, 50 parts, 60 parts, 70 parts or 80 parts, etc., but not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0066] The oil-based drill cuttings powder is made from the residue of rock cuttings returned during on-site oil-based drilling, which is centrifuged and dried to remove the oil phase. It has good oleophilicity and binding properties. The present invention can reduce the treatment cost of waste oil-containing drill cuttings and alleviate the environmental pressure on oil-based drilling fluids. For example, a 100-mesh grinding product can be used.

[0067] Specifically, the lime in the consolidation material is 10-20 parts by weight, for example, 10 parts, 12 parts, 14 parts, 16 parts, 18 parts or 20 parts, etc., but not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0068] The lime is quicklime, specifically commercially available quicklime powder. The particle size can be selected based on conventional settings in the field and without affecting the sealing performance. For example, a product with a sieve size of 100 mesh can be selected.

[0069] Specifically, the organic soil in the consolidation material is 10-20 parts by weight, for example, 10 parts, 12 parts, 14 parts, 16 parts, 18 parts or 20 parts, etc., but not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0070] The organic soil is a commercially available industrial product, which is the product of montmorillonite modified by an organic modifier. For example, the organic modification can be selected by using a quaternary ammonium salt cationic modifier with 1-4 alkyl chains and 12-18 alkyl chain lengths or a silane coupling agent with 12-18 alkyl chain lengths to modify montmorillonite. The specific modification process can be designed and selected according to the conventional modification process in the art. For example, the organic soil can be selected as a product that passes through a 200-mesh sieve.

[0071] The crosslinking agent includes one or a combination of at least two of the following: trimethylolpropane, 2-ethyl-4-methylimidazole, 2-phenylimidazole, 2-isopropylimidazole, tetrachlorophthalic anhydride, hexahydrophthalic anhydride, diethylenetriamine, triethylenetetramine, dimethylaminopropylamine, or diethylaminopropylamine.

[0072] Furthermore, to prevent the solidification of oil-based drilling fluid plugging materials during use, a certain amount of retarder can be introduced into the oil-based drilling fluid plugging materials to prevent premature solidification. Furthermore, to prevent use in environments with higher temperatures, such as >140℃, a high-temperature retarder can be introduced to prevent the oil-based drilling fluid plugging materials from solidifying too quickly under high-temperature conditions.

[0073] Specifically, the oil-based drilling fluid consolidation and plugging material also contains a retarder, in parts by weight of 3-10 parts, such as 3, 4, 5, 6, 7, 8, 9, or 10 parts, but not limited to the listed values; other unlisted values ​​within this range are also applicable. The retarder is a high-temperature retarder, specifically one or a combination of at least two of diethyl malonate, methyl ethyl ketone oxime, acetone oxime, or caprolactam.

[0074] For example, the preparation process of the solidified plugging material for oil-based drilling fluid is as follows: according to the formula, the solidifying material, crosslinking agent and high-temperature retarder are added to the oil-based gel and stirred evenly to obtain a solidified plugging material suitable for oil-based drilling fluid; the stirring speed during the preparation process is 600-800 r / min and the stirring time is 30-50 min, specifically the stirring speed is 600 r / min, 650 r / min, 700 r / min, 750 r / min or 800 r / min, etc., and the stirring time can be controlled to 30 min, 40 min or 50 min, etc., but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0075] Specific embodiments based on the foregoing embodiments are as follows:

[0076] In the following embodiments, unless otherwise stated, all raw materials used are conventional materials and are commercially available. The methods used in the embodiments, unless otherwise specified, are existing technologies.

[0077] In the materials used in the examples, No. 3 white oil was purchased from Guangzhou Maoming Petrochemical Co., Ltd.;

[0078] The refined castor oil was purchased from Inner Mongolia Weiyu Biotechnology Co., Ltd., with an acid value ≤1.60mgKOH / g, free fatty acids ≤0.80%, moisture ≤0.160%, and specific gravity (20℃) 0.952-0.956.

[0079] Toluene diisocyanate (TDI), isophorone diisocyanate (IPDI), diphenylmethane diisocyanate (MDI), azobisisobutyronitrile, zinc isooctanoate, anhydrous ethanol, trimethylolpropane, tetrachlorophthalic anhydride, methyl ethyl ketone oxime, and ε-caprolactam were purchased from Saen Chemical Technology (Shanghai) Co., Ltd.

[0080] Oleophilic nano-silica, model R972, with an average particle size of 30nm, was purchased from Shanghai Kaiyin Chemical Co., Ltd.

[0081] Commercially available quicklime products should be selected from those that pass through a 100-mesh sieve.

[0082] Organic soil, model HFGEL-310, was purchased from Zhejiang Fenghong New Material Co., Ltd., and was sieved through a 200-mesh screen. The undersize product was selected.

[0083] The oil-based drill cuttings powder is derived from oil-based dried rock cuttings from shale gas fields in Sichuan and Chongqing. It is prepared in the laboratory and passed through a 100-mesh sieve, with the undersized product being selected.

[0084] Example 1

[0085] This embodiment provides a solidified plugging material for oil-based drilling fluid, comprising the following components in parts by weight: 50 parts oil-based gel, 50 parts solid phase material, 3 parts crosslinking agent and 5 parts high-temperature retarder.

[0086] The oil-based gel comprises the following raw materials in parts by weight: 100 parts of No. 3 white oil, 60 parts of castor oil-based prepolymer containing terminal -NCO groups, and 10 parts of oleophilic nano silica.

[0087] The castor oil-based prepolymer containing terminal -NCO groups is prepared by reacting castor oil, isoflurone diisocyanate, and initiator azobisisobutyronitrile. The specific preparation method is as follows:

[0088] (1) Castor oil and isoflurane diisocyanate were added to the reaction vessel at a molar ratio of hydroxyl and -NCO groups of 1:1.5 and stirred at 350 r / min for 30 min.

[0089] (2) While maintaining the stirring speed, under N2 protection, add 10% by mass of azobisisobutyronitrile ethanol solution dropwise to the reaction vessel, and control the addition to complete within 30 minutes. The mass of azobisisobutyronitrile is 0.5% of the total mass of castor oil and isoflurone diisocyanate.

[0090] (3) Raise the temperature to 60℃ and keep it warm for 3 hours to obtain castor oil-based prepolymer containing terminal -NCO groups.

[0091] The oil-based gel was prepared by stirring the base oil, castor oil-based prepolymer with terminal -NCO groups, and oleophilic nano-silica at 300 r / min for 30 min.

[0092] The solid material comprises the following raw materials in parts by weight: 60 parts oil-based drill cuttings powder, 20 parts lime, and 20 parts organic clay.

[0093] The crosslinking agent is trimethylolpropane.

[0094] The high-temperature retarder is methyl ethyl ketone oxime.

[0095] The oil-based drilling fluid consolidation and plugging material is prepared through the following steps:

[0096] Solid materials, crosslinking agents, and high-temperature retarders are added to oil-based gels and stirred at 600 r / min for 30 min to obtain solidified plugging materials for oil-based drilling fluids.

[0097] Example 2

[0098] This embodiment provides a solidified plugging material for oil-based drilling fluid, comprising the following components in parts by weight: 30 parts oil-based gel, 70 parts solid phase material and 7 parts crosslinking agent.

[0099] The oil-based gel comprises the following raw materials in parts by weight: 100 parts of No. 3 white oil, 40 parts of castor oil-based prepolymer containing terminal -NCO groups, and 5 parts of oleophilic nano silica.

[0100] The castor oil-based prepolymer containing terminal -NCO groups is prepared by reacting castor oil, toluene diisocyanate, and zinc isooctanoate as an initiator. The specific preparation method is as follows:

[0101] (1) Castor oil and toluene diisocyanate were added to the reaction vessel at a molar ratio of hydroxyl and -NCO groups of 1:3, and stirred at a stirring speed of 450r / min for 30min.

[0102] (2) While maintaining the stirring speed, add a 10% (w / w) zinc isooctanoate ethanol solution to the reaction vessel under N2 protection, and control the addition to complete the addition within half an hour. The mass of zinc isooctanoate is 0.3% of the total mass of castor oil and toluene diisocyanate.

[0103] (3) Raise the temperature to 80℃ and keep it warm for 2 hours to obtain castor oil-based prepolymer containing terminal -NCO groups.

[0104] The oil-based gel was prepared by stirring the base oil, castor oil-based prepolymer with terminal -NCO groups, and oleophilic nano-silica at 400 r / min for 30 min.

[0105] The solid material comprises the following raw materials in parts by weight: 50 parts oil-based drill cuttings powder, 10 parts lime, and 15 parts organic clay.

[0106] The crosslinking agent is trimethylolpropane.

[0107] The oil-based drilling fluid consolidation and plugging material is prepared through the following steps:

[0108] Solid materials and crosslinking agents are added to oil-based gels and stirred at 700 r / min for 30 min to obtain solidified plugging materials for oil-based drilling fluids.

[0109] Example 3

[0110] This embodiment provides a solidified plugging material for oil-based drilling fluid, comprising the following components in parts by weight: 70 parts oil-based gel, 30 parts solid phase material, 5 parts crosslinking agent and 10 parts high-temperature retarder.

[0111] The oil-based gel comprises the following raw materials in parts by weight: 100 parts of No. 3 white oil, 80 parts of castor oil-based prepolymer containing terminal -NCO groups, and 8 parts of oleophilic nano silica.

[0112] The castor oil-based prepolymer containing terminal -NCO groups is prepared by reacting castor oil, diphenylmethane diisocyanate, and azobisisobutyronitrile (azobisisobutyronitrile) as an initiator. The specific preparation method is as follows:

[0113] (1) Castor oil and diphenylmethane diisocyanate were added to the reaction vessel at a molar ratio of hydroxyl and -NCO groups of 1:2, and stirred at a stirring speed of 500r / min for 30min.

[0114] (2) While maintaining the stirring speed, under N2 protection, add 10% by mass of azobisisobutyronitrile ethanol solution dropwise to the reaction vessel, and control the addition to complete the addition within half an hour. The mass of azobisisobutyronitrile is 0.8% of the total mass of castor oil and diphenylmethane diisocyanate.

[0115] (3) Raise the temperature to 50℃ and keep it warm for 4 hours to obtain castor oil-based prepolymer containing terminal -NCO groups.

[0116] The oil-based gel was prepared by stirring the base oil, castor oil-based prepolymer with terminal -NCO groups, and oleophilic nano-silica at 500 r / min for 30 min.

[0117] The solid material comprises the following raw materials in parts by weight: 80 parts oil-based drill cuttings powder, 15 parts lime, and 10 parts organic clay.

[0118] The crosslinking agent is trimethylolpropane.

[0119] The high-temperature retarder is methyl ethyl ketone oxime.

[0120] The oil-based drilling fluid consolidation and plugging material is prepared through the following steps:

[0121] Solid materials, crosslinking agents, and high-temperature retarders are added to the oil-based gel and stirred at 800 r / min for 30 min to obtain a solidified plugging material for oil-based drilling fluid.

[0122] Example 4

[0123] This embodiment provides a solidified plugging material for oil-based drilling fluid, comprising the following components in parts by weight: 40 parts oil-based gel, 60 parts solid phase material and 2 parts crosslinking agent.

[0124] The oil-based gel comprises the following raw materials in parts by weight: 100 parts of No. 3 white oil, 70 parts of castor oil-based prepolymer containing terminal -NCO groups, and 6 parts of oleophilic nano silica.

[0125] The castor oil-based prepolymer containing terminal -NCO groups is prepared by reacting castor oil, isoflurone diisocyanate, and initiator azobisisobutyronitrile. The specific preparation method is as follows:

[0126] (1) Castor oil and isoflurane diisocyanate were added to the reaction vessel at a molar ratio of hydroxyl and -NCO groups of 1:1 and stirred at a stirring speed of 200r / min for 30min.

[0127] (2) While maintaining the stirring speed, under N2 protection, add 10% by mass of azobisisobutyronitrile ethanol solution dropwise to the reaction vessel, and control the addition to complete the addition within half an hour. The mass of azobisisobutyronitrile is 0.1% of the total mass of castor oil and isoflurone diisocyanate.

[0128] (3) Raise the temperature to 100℃ and keep it warm for 1 hour to obtain castor oil-based prepolymer containing terminal -NCO groups.

[0129] The oil-based gel was prepared by stirring the base oil, castor oil-based prepolymer with terminal -NCO groups, and oleophilic nano-silica at 350 r / min for 30 min.

[0130] The solid material comprises the following raw materials in parts by weight: 70 parts oil-based drill cuttings powder, 17 parts lime, and 13 parts organic clay.

[0131] The crosslinking agent is trimethylolpropane.

[0132] The oil-based drilling fluid consolidation and plugging material is prepared through the following steps:

[0133] Solid materials and crosslinking agents are added to oil-based gels and stirred at 750 r / min for 30 min to obtain solidified plugging material for oil-based drilling fluids.

[0134] Example 5

[0135] This embodiment provides a solidified plugging material for oil-based drilling fluid, comprising the following components in parts by weight: 50 parts oil-based gel, 50 parts solid phase material, 3 parts crosslinking agent and 5 parts high-temperature retarder.

[0136] The oil-based gel comprises the following raw materials in parts by weight: 100 parts of linear α-olefin (15 carbon atoms), 60 parts of castor oil-based prepolymer containing terminal -NCO groups, and 10 parts of oleophilic nano-silica.

[0137] The castor oil-based prepolymer containing terminal -NCO groups is prepared by reacting castor oil, toluene diisocyanate, and the initiator azobisisobutyronitrile. The specific preparation method is as follows:

[0138] (1) Castor oil and toluene diisocyanate were added to the reaction vessel at a molar ratio of hydroxyl and -NCO groups of 1:1.5 and stirred at a stirring speed of 350r / min for 30min.

[0139] (2) While maintaining the stirring speed, add a 10% (w / w) zinc isooctanoate ethanol solution to the reaction vessel under N2 protection, and control the addition to complete the addition within half an hour. The mass of zinc isooctanoate is 0.5% of the total mass of castor oil and toluene diisocyanate.

[0140] (3) Raise the temperature to 60℃ and keep it warm for 3 hours to obtain castor oil-based prepolymer containing terminal -NCO groups.

[0141] The oil-based gel was prepared by stirring the base oil, castor oil-based prepolymer with terminal -NCO groups, and oleophilic nano-silica at 300 r / min for 30 min.

[0142] The solid material comprises the following raw materials in parts by weight: 60 parts oil-based drill cuttings powder, 20 parts lime, and 20 parts organic clay.

[0143] The crosslinking agent is tetrachlorophthalic anhydride.

[0144] The high-temperature retarder is diethyl malonate.

[0145] The oil-based drilling fluid consolidation and plugging material is prepared through the following steps:

[0146] Solid materials, crosslinking agents, and high-temperature retarders are added to oil-based gels and stirred at 600 r / min for 30 min to obtain solidified plugging materials for oil-based drilling fluids.

[0147] Example 6

[0148] This embodiment provides a solidified plugging material for oil-based drilling fluid, comprising the following components in parts by weight: 50 parts oil-based gel, 50 parts solid phase material and 3 parts crosslinking agent.

[0149] The oil-based gel comprises the following raw materials in parts by weight: 100 parts linear paraffin (20 carbon atoms), 60 parts castor oil-based prepolymer with terminal -NCO groups, and 10 parts oleophilic nano silica.

[0150] The castor oil-based prepolymer containing terminal -NCO groups is prepared by reacting castor oil, dicyclohexylmethane diisocyanate, and initiator dibutyltin dilaurate. The specific preparation method is as follows:

[0151] (1) Castor oil and dicyclohexylmethane diisocyanate were added to the reaction vessel at a molar ratio of hydroxyl and -NCO groups of 1:1.5 and stirred at 350 r / min for 30 min.

[0152] (2) While maintaining the stirring speed, under N2 protection, add 10% by mass of dibutyltin dilaurate ethanol solution to the reaction vessel dropwise, and control the addition to complete the addition within half an hour. The mass of dibutyltin dilaurate is 0.5% of the total mass of castor oil and dicyclohexylmethane diisocyanate.

[0153] (3) Raise the temperature to 60℃ and keep it warm for 3 hours to obtain castor oil-based prepolymer containing terminal -NCO groups.

[0154] The oil-based gel was prepared by stirring the base oil, castor oil-based prepolymer with terminal -NCO groups, and oleophilic nano-silica at 300 r / min for 30 min.

[0155] The solid material comprises the following raw materials in parts by weight: 60 parts oil-based drill cuttings powder, 20 parts lime, and 20 parts organic clay.

[0156] The crosslinking agent is trimethylolpropane.

[0157] The oil-based drilling fluid consolidation and plugging material is prepared through the following steps:

[0158] Solid materials and crosslinking agents are added to oil-based gels and stirred at 600 r / min for 30 min to obtain solidified plugging material for oil-based drilling fluids.

[0159] Example 7

[0160] This embodiment provides a solidified plugging material for oil-based drilling fluid, comprising the following components in parts by weight: 50 parts oil-based gel, 50 parts solid phase material, 3 parts crosslinking agent and 3 parts high-temperature retarder.

[0161] The oil-based gel comprises the following raw materials in parts by weight: 100 parts of 0# diesel oil, 60 parts of castor oil-based prepolymer containing terminal -NCO groups, and 10 parts of oleophilic nano-silica.

[0162] The castor oil-based prepolymer containing terminal -NCO groups is prepared by reacting castor oil, lysine diisocyanate, and bismuth isooctanoate initiator. The specific preparation method is as follows:

[0163] (1) Castor oil and lysine diisocyanate were added to the reaction vessel at a molar ratio of hydroxyl and -NCO groups of 1:1.5 and stirred at 350 r / min for 30 min.

[0164] (2) While maintaining the stirring speed, under N2 protection, add 10% bismuth isooctanoate ethanol solution dropwise to the reaction vessel, and control the addition to complete the addition within half an hour. The mass of bismuth isooctanoate is 0.5% of the total mass of castor oil and lysine diisocyanate.

[0165] (3) Raise the temperature to 60℃ and keep it warm for 3 hours to obtain castor oil-based prepolymer containing terminal -NCO groups.

[0166] The oil-based gel was prepared by stirring the base oil, castor oil-based prepolymer with terminal -NCO groups, and oleophilic nano-silica at 300 r / min for 30 min.

[0167] The solid material comprises the following raw materials in parts by weight: 60 parts oil-based drill cuttings powder, 20 parts lime, and 20 parts organic clay.

[0168] The crosslinking agent is trimethylolpropane.

[0169] The high-temperature retarder is diethylaminopropylamine.

[0170] The oil-based drilling fluid consolidation and plugging material is prepared through the following steps:

[0171] Solid materials, crosslinking agents, and high-temperature retarders are added to oil-based gels and stirred at 600 r / min for 30 min to obtain solidified plugging materials for oil-based drilling fluids.

[0172] Example 8

[0173] This embodiment provides a solidified plugging material for oil-based drilling fluid, comprising the following components in parts by weight: 50 parts oil-based gel, 50 parts solid phase material, 6 parts crosslinking agent and 3 parts high-temperature retarder.

[0174] The oil-based gel comprises the following raw materials in parts by weight: 100 parts of No. 5 white oil, 60 parts of castor oil-based prepolymer containing terminal -NCO groups, and 10 parts of oleophilic nano silica.

[0175] The castor oil-based prepolymer containing terminal -NCO groups is prepared by reacting castor oil, hexamethylene diisocyanate, and initiator azobisisobutyronitrile. The specific preparation method is as follows:

[0176] (1) Castor oil and hexamethylene diisocyanate were added to the reaction vessel at a molar ratio of hydroxyl and -NCO groups of 1:1.5 and stirred at 350 r / min for 30 min.

[0177] (2) While maintaining the stirring speed, under N2 protection, add 10% by mass of azobisisobutyronitrile ethanol solution dropwise to the reaction vessel, and control the addition to complete the addition within half an hour. The mass of azobisisobutyronitrile is 0.5% of the total mass of castor oil and hexamethylene diisocyanate.

[0178] (3) Raise the temperature to 60℃ and keep it warm for 3 hours to obtain castor oil-based prepolymer containing terminal -NCO groups.

[0179] The oil-based gel was prepared by stirring the base oil, castor oil-based prepolymer with terminal -NCO groups, and oleophilic nano-silica at 300 r / min for 30 min.

[0180] The solid material comprises the following raw materials in parts by weight: 60 parts oil-based drill cuttings powder, 20 parts lime, and 20 parts organic clay.

[0181] The crosslinking agent is tetrachlorophthalic anhydride.

[0182] The high-temperature retarder is ε-caprolactam.

[0183] The oil-based drilling fluid consolidation and plugging material is prepared through the following steps:

[0184] Solid materials, crosslinking agents, and high-temperature retarders are added to oil-based gels and stirred at 600 r / min for 30 min to obtain solidified plugging materials for oil-based drilling fluids.

[0185] Example 9

[0186] The only difference from Example 1 is that no high-temperature retarder was added to the oil-based drilling fluid consolidation and plugging material.

[0187] Comparative Example 1

[0188] The only difference from Example 1 is that no consolidating material is added to the oil-based drilling fluid consolidation and plugging material.

[0189] Comparative Example 2

[0190] The only difference from Example 1 is that no crosslinking agent was added to the oil-based drilling fluid consolidation plugging material.

[0191] Comparative Example 3

[0192] The only difference from Example 1 is that the oil-based drilling fluid consolidation and plugging material does not contain oleophilic nano-silica.

[0193] Comparative Example 4

[0194] The only difference from Example 1 is that the castor oil-based prepolymer with terminal -NCO groups is replaced with an equal amount of castor oil.

[0195] Comparative Example 5

[0196] The only difference from Example 1 is that the castor oil-based prepolymer with terminal -NCO groups is replaced with an equal amount of isoflurane diisocyanate.

[0197] Test case

[0198] Construction time is a crucial factor in ensuring downhole safety. In the deep shale gas formations of Sichuan and Chongqing, oil-based drilling fluids are commonly used in four-stage drilling operations. The bottom hole temperature can reach 150℃, requiring the solidified plugging material to be in a good flow state before being pumped to the leaking layer, and to begin solidification only after reaching the target layer.

[0199] The curing time of the oil-based drilling fluid solidification and plugging agents prepared in Examples 1-9 and Comparative Examples 1-5 was mechanically tested. The specific test method is as follows: the oil-based drilling fluid solidification and plugging material was prepared at room temperature, poured into a mold, and placed in an oven. The time required for curing to begin was tested at a set temperature. The experimental results are shown in Tables 1 and 2, respectively.

[0200] Table 1

[0201]

[0202]

[0203] Table 2

[0204]

[0205]

[0206] According to the experimental results in Tables 1 and 2, the curing time for Examples 1, 3, 5, 7, and 8 was generally over 20 hours at 60℃, over 15 hours at 120℃, and over 3 hours at 150℃, ensuring sufficient safe construction time. Furthermore, changing the amount of crosslinking agent, high-temperature retarder, and solid material affects the curing time of the solidified plugging material for oil-based drilling fluids, with the crosslinking agent and high-temperature retarder having the most significant impact on the solidification time. Comparative Examples 1 and 7, by halving or omitting the high-temperature retarder, resulted in a significantly faster solidification rate of the product at different temperatures, while still meeting construction safety requirements. Example 8, by doubling the crosslinking agent, also significantly accelerated the solidification rate of the product at different temperatures, while still meeting construction safety requirements. Examples 2, 4, 6, and 9, by not adding a high-temperature retarder, resulted in the product solidifying rapidly after temperatures exceeded 150°C, failing to meet the safety requirements for on-site leak sealing at high temperatures. Comparative Example 1, by not adding a solid material, resulted in a significantly prolonged solidification time at various temperatures. Comparative Example 2, by not adding a crosslinking agent, resulted in… The product failed to solidify at various temperatures for extended periods, making effective plugging impossible. Comparative Example 3, lacking nano-silica, resulted in prolonged curing times at various temperatures, hindering effective plugging and indicating that oleophilic nano-silica also affects curing time. The experimental results show that the oil-based drilling fluid solidification plugging material provided by this invention has the advantage of safe and controllable solidification time, making it suitable for handling complex well leaks in deep shale gas and oil-based drilling fluids. Comparative Examples 4 and 5, using only castor oil or isoflurane diisocyanate as monomers in the prepolymer, resulted in the product failing to solidify at various temperatures.

[0207] Furthermore, during the plugging process, the key to ensuring successful plugging is that the plugging material must form a sufficiently strong plugging layer at the crack. The compressive strength of the oil-based drilling fluids prepared in Examples 1-9 and Comparative Examples 1-3 was tested after the solidified plugging material was cured. The plugging materials in Comparative Examples 4 and 5 were not tested for compressive strength because they were not cured. The testing method was as follows: After the solidified plugging material cured, its compressive strength was tested at different times using an SZR-3 bitumen penetration tester. The results are shown in Tables 3 and 4.

[0208] Table 3

[0209]

[0210]

[0211] Table 4

[0212]

[0213]

[0214] According to the experimental results in Tables 3 and 4, the curing temperature has virtually no effect on the final cured strength of each sample. Compared with Examples 1, 2, and 3, after changing the type of isocyanate, the consolidation strength fluctuated but remained above 5 MPa. Example 4 increased the amount of solid material, which significantly increased the consolidation strength. Examples 5, 6, 7, and 8 changed or altered the type and amount of crosslinking agent and high-temperature retarder, which affected the consolidation time but did not cause a significant change in the final consolidation strength of the product. Examples 2, 4, 6, and 9 did not add high-temperature retarder, and the product strength after consolidation still reached above 6 MPa, indicating that the retarder does not affect the strength of the sealing material after curing. Comparative Example 1 did not add solid material, which caused the product strength to decrease significantly after curing at various temperatures, making it unable to effectively seal the leak layer under pressure. Comparative Example 2 did not add crosslinking agent, which caused the product to fail to cure for a long time at various temperatures, making it impossible to conduct curing strength tests. Comparative Example 3 did not add oleophilic nano silica, which caused the product strength to decrease to about 4 MPa after curing, indicating that oleophilic nano silica has a positive effect on improving curing strength. The experimental results above show that the solidification strength of the oil-based drilling fluid solidification plugging material provided by the present invention can generally reach more than 5 MPa, and the solidification strength can be significantly improved by increasing the amount of solid material, which meets the requirements of deep shale gas pressure plugging. In comparative examples 4 and 5, the prepolymer monomer was replaced with prepolymer, which resulted in the failure of solidification.

[0215] In summary, the oil-based drilling fluid consolidation plugging material provided by this invention is a mixed system composed of oil-based gel, solid phase material, crosslinking agent, and high-temperature retarder. After being pumped to the leakage layer, it can form a plugging layer with oil-based gel as the main component and solid phase material as the auxiliary component. It has the characteristics of controllable gelation time, high pressure bearing strength, and good compatibility with oil-based drilling fluid. It can effectively improve the plugging success rate of oil-based drilling fluid leakage and meet the plugging needs of deep shale gas oil-based drilling fluid.

[0216] The present invention is described in detail through the above embodiments, but the present invention is not limited to the above detailed structural features, that is, it does not mean that the present invention must rely on the above detailed structural features to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent substitutions for the components used in the present invention, additions of auxiliary components, and selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

[0217] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the protection scope of the present invention.

[0218] 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 describe the various possible combinations separately.

[0219] Furthermore, various different embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the present invention, they should also be regarded as the content disclosed by the present invention.

Claims

1. A consolidation and plugging material for oil-based drilling fluids, characterized in that, The oil-based drilling fluid consolidation and plugging material comprises, by weight: 30-70 parts oil-based gel, 30-70 parts consolidation material, 2-7 parts crosslinking agent, and 3-10 parts retarder. The oil-based gel comprises: 100-110 parts of base oil, 40-80 parts of castor oil-based prepolymer containing terminal -NCO groups, and 5-10 parts of oleophilic nano-silica. The base oil includes one or a combination of at least two of the following: 0# diesel oil, 3# white oil, 5# white oil, gas-derived oil, linear paraffin, or linear α-olefins. The castor oil-based prepolymer containing terminal -NCO groups is prepared by reacting castor oil, isocyanate monomers, and an initiator. The isocyanate monomers include one or a combination of at least two of toluene diisocyanate, isophorone diisocyanate, diphenylmethane diisocyanate, dicyclohexylmethane diisocyanate, hexamethylene diisocyanate, or lysine diisocyanate. The initiator includes one or a combination of at least two of azobisisobutyronitrile, zinc isooctanoate, tin isooctanoate, bismuth isooctanoate, or dibutyltin dilaurate. The consolidation material includes: 50-80 parts of oil-based drill cuttings powder, 10-20 parts of lime, and 10-20 parts of organic soil; The crosslinking agent includes one or a combination of at least two of the following: trimethylolpropane, 2-ethyl-4-methylimidazole, 2-phenylimidazole, 2-isopropylimidazole, tetrachlorophthalic anhydride, hexahydrophthalic anhydride, diethylenetriamine, triethylenetetramine, dimethylaminopropylamine, or diethylaminopropylamine. The retarder is a high-temperature retarder, which includes one or a combination of at least two of diethyl malonate, methyl ethyl ketone oxime, acetone oxime, or caprolactam. The oleophilic nano-silica was purchased from Shanghai Kaiyin Chemical Co., Ltd., model R972, with an average particle size of 30nm.

2. The solidification and plugging material for oil-based drilling fluid as described in claim 1, characterized in that, The base oil includes base oils for oil-based drilling fluids.

3. The solidification and plugging material for oil-based drilling fluid as described in claim 1, characterized in that, The purity of the castor oil is >70%.

4. A method for preparing a solidified plugging material for oil-based drilling fluid as described in any one of claims 1-3, characterized in that, The preparation method includes adding a consolidating material, a crosslinking agent, and a retarder to an oil-based gel according to a formula and stirring to obtain a consolidating and plugging material suitable for oil-based drilling fluids.

5. The preparation method according to claim 4, characterized in that, The stirring rate is 600-800 r / min.

6. The preparation method according to claim 4, characterized in that, The stirring time is 30-50 minutes.

7. The use of a solidification and plugging material for oil-based drilling fluids as described in any one of claims 1-3, characterized in that, The purpose is to use a solidified plugging material for oil-based drilling fluid to seal the leakage of oil-based drilling fluid during the drilling process.

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