Special reservoir protection material for oil-based drilling fluid as well as preparation method and application of special reservoir protection material

Abstract

The invention relates to a special reservoir protection material for oil-based drilling fluid as well as a preparation method and application of the special reservoir protection material. The raw materials of the special reservoir protection material comprise a proppant, a micro-elastic plugging agent, a composite plugging agent and microcapsules. The special reservoir protection material provided by the invention can be well suitable for oil-based drilling, and reservoir damage caused by inapplicable particle properties is reduced. When the composite material is applied to a protection method of a multi-size screen closed reservoir, the application range of pore throat cracks of a reservoir protection material can be widened, and the reservoir protection effect that main seepage channels are fully covered is achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of oil and gas well engineering, and in particular to a special reservoir protection material for oil-based drilling fluid, a preparation method thereof, and an application thereof. Background Art

[0002] In the field of oil exploration and development, low- and extra-low-permeability reservoirs often face challenges such as difficulty in development and low productivity due to their extremely low permeability. To effectively develop these reservoirs, the use of drilling fluids and reservoir protection technologies are crucial. Traditional water-based drilling fluids can easily damage the reservoir during drilling, causing problems such as filtration, water lock, and clay swelling. These damages not only reduce reservoir permeability but also impact the well's subsequent productivity.

[0003] In recent years, oil-based drilling fluids have been widely used in the development of low- and extra-low-permeability reservoirs due to their excellent high-temperature resistance, pollution resistance, and lubricity. However, even with oil-based drilling fluids, some degree of reservoir damage is unavoidable. In particular, during the drilling process, emulsification, clogging, and oil-phase adhesion can lead to decreased reservoir permeability, impacting oil and gas well production. However, effective reservoir protection methods for oil-based drilling fluids are currently lacking. Therefore, it is necessary to develop reservoir protection methods for oil-based drilling fluids suitable for low- and extra-low-permeability reservoirs to improve their effectiveness.

[0004] Traditional reservoir protection methods primarily target water-based drilling fluids, and their underlying theories are primarily based on the 1 / 3 bridging rule, ideal filling theory, D90 rule, and D50 rule. Currently, these traditional reservoir protection methods suffer from the following issues: First, existing low- and extra-low-permeability reservoir protection methods primarily target water-based drilling fluids. Most of these materials, due to their surface properties, are unsuitable for oil-based drilling fluids. Mainstream ultrafine calcium carbonate-based reservoir protection materials exhibit aggregation and sedimentation in oil-based drilling fluids, failing to meet the requirements for oil-based drilling fluid reservoir protection. Second, current reservoir protection material size selection is based on the principle of rapidly forming a dense seal within pores or fractures. This requires the material to penetrate the reservoir's seepage channels. Given the inherently low flowback capacity of low- and extra-low-permeability reservoirs, this results in the material penetrating the reservoir, causing some degree of damage regardless of the underlying theoretical conditions, defeating the purpose of reservoir protection. Third, addressing the issues surrounding oil-based drilling fluids and reservoir protection theory, some studies have provided new methods. For example, CN110361305A discloses a method for adding and supplementing solid-phase materials for deep-well drilling fluid reservoir protection based on solid-phase particle size degradation. This method provides a method for solid-phase particle size degradation, where the particle size distribution matches the reservoir pore throat size or fracture width, improving reservoir protection effectiveness. Other studies have also provided similar methods for selecting particle sizes comparable to or smaller than the pore throat or fracture size, which can improve but not completely eliminate reservoir protection efficiency. Consequently, traditional materials and particle size selection methods suitable for water-based environments are less effective for oil-based drilling fluid reservoir protection.

[0005] Therefore, it is of great significance to construct a reservoir protection method that can be well applied to oil-based drilling fluids in low-permeability and ultra-low-permeability reservoirs, thereby improving the reservoir protection effect of oil-based drilling fluids. Summary of the Invention

[0006] To address the above technical issues, the present invention provides a reservoir protection material specifically designed for oil-based drilling fluids, as well as its preparation method and application. This material is well-suited for oil-based drilling, reduces reservoir damage caused by unsuitable particle properties, and effectively improves the reservoir protection effectiveness of oil-based drilling fluids.

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

[0008] In a first aspect, the present invention provides a special reservoir protection material for oil-based drilling fluid, wherein the raw materials for preparing the special reservoir protection material include proppant, microelastic plugging agent, composite plugging agent and microcapsule.

[0009] The present invention combines proppants, microelastic plugging agents, composite plugging agents, and microcapsules to create a reservoir protection material specifically designed for oil-based drilling fluids. When applied to oil-based drilling fluids used in low- and extra-low-permeability reservoirs, the synergistic effects of the various raw materials effectively enhance the protective effect. Furthermore, the material reduces reservoir damage caused by unsuitable particle properties, further enhancing reservoir protection.

[0010] Preferably, the raw materials for preparing the special reservoir protection material include the following components in parts by weight:

[0011]

[0012] In the present invention, the content of the proppant is 30-50 parts by weight, for example, it can be 32 parts by weight, 34 parts by weight, 36 parts by weight, 38 parts by weight, 40 parts by weight, 42 parts by weight, 44 parts by weight, 46 parts by weight or 48 parts by weight, etc., and is not limited to the values ​​listed above. Other data not listed within the numerical range are also applicable.

[0013] The content of the microelastic plugging agent is 20-40 parts by weight, for example, 22 parts by weight, 24 parts by weight, 26 parts by weight, 28 parts by weight, 30 parts by weight, 32 parts by weight, 34 parts by weight, 36 parts by weight or 38 parts by weight, etc., and is not limited to the values ​​listed above. Other values ​​not listed within the numerical range are also applicable.

[0014] The content of the composite plugging agent is 10-30 parts by weight, for example, it can be 12 parts by weight, 14 parts by weight, 16 parts by weight, 18 parts by weight, 20 parts by weight, 22 parts by weight, 24 parts by weight, 26 parts by weight or 28 parts by weight, etc. It is not limited to the values ​​listed above, and other data not listed within the numerical range are also applicable.

[0015] The content of the microcapsules is 3-5 parts by weight, for example, 3.2 parts by weight, 3.4 parts by weight, 3.6 parts by weight, 3.8 parts by weight, 4 parts by weight, 4.2 parts by weight, 4.4 parts by weight, 4.6 parts by weight or 4.8 parts by weight, etc., and is not limited to the values ​​listed above. Other data not listed within the numerical range are also applicable.

[0016] Preferably, the proppant is a non-spherical rigid embedded proppant.

[0017] Preferably, the non-spherical shape is a cone shape, preferably a regular tetrahedron shape.

[0018] Preferably, the rigid embedding proppant comprises any one of metal material, fiberglass reinforced plastic material or polycarbonate, or a combination of at least two thereof.

[0019] Preferably, the metal material comprises an aluminum-based metal powder material.

[0020] Preferably, the metal material is a dense filling body formed by solidifying aluminum-based metal powder material in a regular tetrahedral form, and the size of the filling body can be controlled according to the mold.

[0021] Preferably, the fiberglass reinforced plastic material comprises glass fiber and resin.

[0022] Preferably, the fiberglass reinforced plastic material is a dense filling body formed by curing glass fiber and resin in a regular tetrahedral form, and the size is controllable according to the mold.

[0023] Preferably, the polycarbonate is a dense filling body formed by curing a commercially available polycarbonate material in a regular tetrahedral form, and the size of the filling body can be controlled according to the mold.

[0024] In the present invention, raw materials of any one or a combination of at least two of commercially available metal materials, fiberglass materials or polycarbonate are prepared into a regular tetrahedral shape, the size of which is selected according to actual conditions, and then a mold is used to make a specific non-spherical rigid embedding proppant of the corresponding size.

[0025] Preferably, the micro-elastic plugging agent is a plugging agent that has the ability to change its shape within 20% under the temperature and pressure conditions of the target layer.

[0026] Preferably, the microelastic plugging agent includes any one of polyvinyl chloride, polyetheretherketone, epoxy resin, carbon fiber or polyaramid, or a combination of at least two thereof.

[0027] Preferably, the size of the microelastic plugging agent is consistent with the shortest side size of the proppant.

[0028] In the present invention, the micro-elastic plugging agent is prepared from any one or a combination of at least two of commercially available polyvinyl chloride, polyetheretherketone, epoxy resin, carbon fiber or polyaramid into a regular tetrahedral shape. The size of the micro-elastic plugging agent is selected according to actual conditions, and a mold is used to make a specific micro-elastic plugging agent with the corresponding size.

[0029] Preferably, the composite plugging agent includes any one of quartz sand, calcium carbonate, polyester fiber or graphite, or a combination of at least two of them.

[0030] Preferably, the calcium carbonate is modified ultrafine calcium carbonate whose surface is modified by a coupling agent.

[0031] Preferably, the coupling agent is an oil-soluble coupling agent.

[0032] Preferably, the oil-soluble coupling agent includes a silane coupling agent and / or a titanate coupling agent.

[0033] Preferably, the silane coupling agent includes any one of an aminosilane coupling agent, a methylsilane coupling agent, a sulfur-containing silane coupling agent, a methacrylate silane coupling agent or an epoxy silane coupling agent, or a combination of at least two thereof.

[0034] Preferably, the raw material of the titanate coupling agent includes stearic acid.

[0035] Preferably, the polyester fiber is a modified polyester fiber that has been subjected to a coating treatment.

[0036] Preferably, the coating treatment is a surface oleophilic coating treatment.

[0037] Preferably, the surface oleophilic coating is a coating introduced with long-chain alkanes, silicone oil or fluorocarbon compounds.

[0038] In the present invention, the composite plugging agent is prepared from any one or a combination of at least two of commercially available quartz sand, calcium carbonate, polyester fiber or graphite into a regular tetrahedral shape. The size of the composite plugging agent is selected according to actual conditions, and a mold is used to make a specific plugging agent with the corresponding size.

[0039] Preferably, the microcapsules are spherical thermosensitive acid-soluble microcapsules.

[0040] Preferably, the spherical thermosensitive acid-soluble microcapsules are microcapsule-type solid acids composed of a core material and a wrapping material.

[0041] Preferably, the core material comprises sulfamic acid.

[0042] Preferably, the wrapping material comprises a double-layer wrapping material formed of paraffin wax and ethyl cellulose.

[0043] In the present invention, the microcapsules can be obtained by simply mixing the core material and the wrapping material.

[0044] Preferably, the activation temperature of the spherical thermosensitive acid-soluble microcapsules is greater than 60° C., and the activation time is 10-24 hours (for example, 10 hours, 12 hours, 14 hours, 16 hours, 18 hours, 20 hours, 22 hours or 24 hours, etc.).

[0045] Preferably, the raw materials for preparing the special reservoir protection material also include a wetting agent.

[0046] Preferably, the content of the wetting agent is 1-3 parts by weight, for example, it can be 1 part by weight, 1.2 parts by weight, 1.4 parts by weight, 1.6 parts by weight, 1.8 parts by weight, 2 parts by weight, 2.2 parts by weight, 2.4 parts by weight, 2.6 parts by weight, 2.8 parts by weight or 3 parts by weight, etc., and is not limited to the values ​​listed above. Other unlisted data within the numerical range are also applicable.

[0047] In the present invention, based on the total mass of the proppant, microelastic plugging agent, composite plugging agent and microcapsule being 100 parts by weight, the wetting agent is used in an amount of 1-3 parts by weight.

[0048] Preferably, the wetting agent includes a fatty acid wetting agent and / or a phospholipid wetting agent, and more preferably a combination of a fatty acid wetting agent and a phospholipid wetting agent.

[0049] Preferably, the composite ratio of the fatty acid wetting agent to the phospholipid wetting agent is 1:(0.8-1.2), and (0.8-1.2) can be, for example, 0.8, 0.85, 0.9, 0.95, 1, 1.05, 1.1, 1.15 or 1.2, etc., and is not limited to the above-listed values. Other unlisted data within the numerical range are also applicable.

[0050] Preferably, the fatty acid wetting agent includes any one of calcium stearate, calcium oleate or calcium laurate, or a combination of at least two thereof.

[0051] Preferably, the phospholipid wetting agent comprises cephalin and / or inositol phospholipids.

[0052] In a second aspect, the present invention provides a method for selecting raw material size, which is used to select and prepare the size of raw material proppants, microelastic plugging agents, composite plugging agents and microcapsules for preparing the special reservoir protection materials for oil-based drilling fluids described in the first aspect.

[0053] Preferably, the method for selecting the raw material size comprises the following steps:

[0054] (1) Determine the distribution and peak value of cracks or main seepage pores;

[0055] (2) selecting the proppant size according to the distribution state and peak value described in step (1);

[0056] (3) selecting the size of the microelastic plugging agent according to the proppant size described in step (2);

[0057] (4) selecting the size of the composite plugging agent according to the distribution state and peak value described in step (1);

[0058] (5) selecting the size of the microcapsules according to the distribution state and peak value described in step (1);

[0059] The order of steps (2), (4) and (5) is not limited.

[0060] Preferably, the method for determining the distribution state and peak value of the cracks or main seepage pores in step (1) comprises the following steps:

[0061] S1-1: Collect imaging logging and conventional logging data in the target area for research or application, analyze the distribution range of reservoir fractures and main seepage pores in the target well, and provide reference for the selection of main reservoir protection range and reservoir protection materials for oil-based drilling fluids;

[0062] S1-2: Collect reservoir cores from adjacent wells and analyze the distribution of the main pores and pore throats in the reservoir using the mercury injection method. Analyze the size distribution of seepage channels (i.e., fractures or main seepage pores) that contribute more than 10% to the permeability, and determine the distribution status and peak value of the fractures or main seepage pores.

[0063] Preferably, the imaging logging and conventional logging data in step S1-1 refer to measured data from adjacent wells that belong to the same formation or have similar geological properties as the target well.

[0064] Preferably, the mercury intrusion method in step S1-2 is a constant-pressure mercury intrusion method.

[0065] Preferably, the permeability contribution rate in step S1-2 is obtained by a permeability contribution rate calculation method based on pore size distribution, and the specific method is: first, the pore size distribution data of the rock is obtained by mercury injection, nitrogen adsorption or other pore structure testing methods; then, based on the pore size distribution data, the relationship between pore volume and permeability is modeled using the Carman-Kozeny equation or a similar permeability model, and the pore volume and permeability contribution value of each pore size or pore size range is calculated; finally, the permeability contribution value of each pore size or pore size range is added to obtain the total permeability, and the permeability contribution rate of each pore size or pore size range is calculated.

[0066] Preferably, the fractures in step S1-2 are target well reservoir fractures interpreted from imaging logging data.

[0067] Preferably, the method for selecting the proppant size in step (2) includes:

[0068] If the fracture or main seepage pore presents a single peak distribution state, the shortest side length of the proppant is 1.5-2 times (for example, 1.5 times, 1.6 times, 1.7 times, 1.8 times, 1.9 times or 2 times, etc.) the fracture aperture or the main seepage pore diameter;

[0069] Alternatively, the fractures or main seepage pores present a multi-peak distribution state, and the shortest side dimension of the proppant forms a multi-scale distribution according to each peak.

[0070] Preferably, the size of the microelastic plugging agent in step (3) is consistent with the size of the proppant.

[0071] Preferably, the method for selecting the size of the composite plugging agent in step (4) includes selecting according to the reservoir protection particle size of the fracture or main seepage pore d90-d100, wherein d90-d100 can be, for example, d90, d91, d92, d93, d94, d95, d96, d97, d98, d99 or d100, etc., and is not limited to the values ​​listed above. Other data not listed within the numerical range are also applicable.

[0072] Preferably, the reservoir protection particle size of d90-d100 is preferably the particle size value corresponding to 90-100% (for example, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98% or 99%, etc.) in the cumulative distribution of the main seepage channel size.

[0073] Preferably, the method for selecting the size of the microcapsules in step (5) includes selecting according to 0.5 times the minimum peak size of the cracks or main seepage pores in a unimodal or multimodal distribution state.

[0074] In the present invention, the sizes of proppants, microelastic plugging agents, composite plugging agents and microcapsules are selected by adopting a method of selecting raw material sizes, so that the prepared special reservoir protection material for oil-based drilling fluid can be embedded with particles at the entrances of cracks or main seepage pores to form a seepage channel entrance screen, thereby reducing the irreversible damage such as granularity and emulsification blockage caused by the invasion of foreign particles into low-permeability reservoirs from the source, thereby effectively improving the effect of reservoir protection.

[0075] In a third aspect, the present invention provides a method for preparing the reservoir protection material for oil-based drilling fluid as described in the first aspect, the preparation method comprising the following steps:

[0076] First, the sizes of the proppant, microelastic plugging agent, composite plugging agent and microcapsule are selected and prepared according to the raw material size selection method described in the second aspect, and then the proppant, microelastic plugging agent, composite plugging agent and microcapsule prepared above are mixed to obtain the reservoir protection material dedicated to oil-based drilling fluid.

[0077] In a fourth aspect, the present invention provides a method for protecting a reservoir by enclosing a curtain, the method comprising the following steps:

[0078] a. Determine the distribution of water phase droplets and solid phase particles in oil-based drilling fluid;

[0079] b. preparing a special reservoir protection material for oil-based drilling fluid according to the preparation method of the special reservoir protection material for oil-based drilling fluid described in the third aspect;

[0080] c. Observe the degree of overlap between the size distribution of the oil-based drilling fluid special reservoir protection material and the aqueous phase droplet and solid phase particle size distribution described in step a, and reduce the amount of the oil-based drilling fluid special reservoir protection material added in the overlapping portion accordingly;

[0081] d. Add the special reservoir protection material for oil-based drilling fluid described in step b into the oil-based drilling fluid and stir.

[0082] Preferably, the distribution of the aqueous phase droplets in step a is observed using a polarizing microscope.

[0083] Preferably, the solid phase particle distribution in step a is obtained by analyzing with a laser particle size analyzer.

[0084] Preferably, the amount of the special reservoir protection material added in step d is determined according to the distribution state of the fractures or main seepage pores.

[0085] Preferably, the method for determining the amount of the reservoir protection material specifically for the oil-based drilling fluid to be added specifically includes:

[0086] If the cracks or main seepage pores are unimodal in distribution, after drilling into the target well reservoir section, add the oil-based drilling fluid special reservoir protection material into the oil-based drilling fluid at a rate of 5-8% by mass of the oil-based drilling fluid, and stir at a speed of 6000-10000 r / min (for example, 6500 r / min, 7000 r / min, 7500 r / min, 8000 r / min, 8500 r / min, 9000 r / min, or 9500 r / min, etc.) for 20-30 min (for example, 21 min, 22 min, 23 min, 24 min, 25 min, 26 min, 27 min, 28 min, or 29 min, etc.);

[0087] If the cracks or main seepage pores have a multi-peak distribution, add the oil-based drilling fluid special reservoir protection material to the oil-based drilling fluid according to the number of peaks at 5% of the mass of the oil-based drilling fluid for each peak, and stir at a speed of 6000r / min for 20min.

[0088] Preferably, when the cracks or main seepage pores are multi-peak distributed, the oil-based drilling fluid-specific reservoir protection material is added to the oil-based drilling fluid in stages in the order of peak values ​​from large to small, thereby facilitating the purpose of blocking large peaks first and covering peak values ​​with a curtain seal.

[0089] Compared with the prior art, the present invention has at least the following beneficial effects:

[0090] (1) The present invention obtains a reservoir protection material specifically for oil-based drilling fluid by compounding a proppant, a microelastic plugging agent, a composite plugging agent, and microcapsules. When the material is applied to oil-based drilling fluid in low-permeability or extra-low-permeability reservoirs, the protective effect of the material on the oil-based drilling fluid reservoir can be effectively improved through the synergistic effect of the various raw materials. At the same time, the material can also reduce reservoir damage caused by inappropriate particle properties, further improving the protective effect on the reservoir.

[0091] (2) Further preferably, the method for selecting raw material size provided by the present invention can select the size of the raw material for preparing the special reservoir protection material for oil-based drilling fluid, thereby selecting raw material particles based on the size of the pore throat or fracture, and then constructing a special reservoir protection material suitable for oil-based drilling, which can achieve the purpose of forming a dense screen curtain outside the pore throat or fracture entrance end with a larger permeability contribution rate, and reduce the irreversible granularity and emulsification blockage caused by the invasion of foreign particles into the low permeability reservoir from the source, thereby effectively improving the reservoir protection effect of the oil-based drilling fluid.

[0092] (3) Further preferably, the curtain-shaped closed reservoir protection method provided by the present invention targets the multi-size distribution characteristics of pore throats and cracks in low-permeability and extra-low-permeability reservoirs, and adopts a reservoir protection particle size of d90-d100, thereby increasing the applicable range of pore throats and cracks of the special reservoir protection material for oil-based drilling fluid as much as possible, achieving a reservoir protection effect of full coverage of the main seepage channels, so that the permeability recovery rate of the oil field can reach more than 89%. DETAILED DESCRIPTION

[0093] For the convenience of understanding the present invention, the present invention is given below with examples. It should be understood by those skilled in the art that the examples are only for the purpose of helping to understand the present invention and should not be regarded as specific limitations of the present invention.

[0094] Unless otherwise specified, the raw materials in the following examples and comparative examples are all commercially available. Some of the raw material information is as follows:

[0095] The raw material of the non-spherical rigid embedded proppant is polycarbonate, purchased from PC 141R-111;

[0096] The raw material of micro-elastic plugging agent is polyvinyl chloride, purchased from Shanghai Chlor-Alkali M-1000;

[0097] The raw material of composite plugging agent is quartz sand;

[0098] The raw material of spherical thermosensitive acid-soluble microcapsules, ethyl cellulose, was purchased from Shanghai Helisite Chemical Co., Ltd. with the brand name EC-T.

[0099] The wetting agent was calcium stearate and cephalin in a mass ratio of 1:1. Cephalin was purchased from Sichuan Huanxu Biotechnology Co., Ltd.

[0100] Example 1

[0101] The target reservoir A of a low-permeability oilfield in the East China Sea has no fracture distribution, and the peak distribution of the main seepage pores is in the range of 1.5-1.8μm. The peak distribution size of the water phase droplets in the oil-based drilling fluid used is 0.8μm, and the peak distribution size of the solid phase in the oil-based drilling fluid is 22μm.

[0102] The implementation process of the screen curtain closed reservoir protection method in this embodiment is as follows:

[0103] (1) Preparation of special reservoir protection materials for oil-based drilling fluids

[0104] The specific raw material ratio for preparing the reservoir protection material for oil-based drilling fluids is as follows: 45 parts by weight of non-spherical rigid embedded proppant, 32 parts by weight of microelastic plugging agent, 20 parts by weight of composite plugging agent, 3 parts by weight of spherical thermosensitive acid-soluble microcapsules, and 1 part by weight of a wetting agent. The non-spherical rigid embedded proppant has an equilateral tetrahedron structure and is 2.25 μm long; the microelastic plugging agent has an equilateral tetrahedron structure and is 2.25 μm long; the composite plugging material has a particle size of 1.35-1.5 μm; and the spherical thermosensitive acid-soluble microcapsules have a particle size of 0.75 μm.

[0105] (2) After the target well target layer is encountered, the oil-based drilling fluid dedicated reservoir protection material described in step (1) is added to the oil-based drilling fluid at a rate of 5% by mass of the oil-based drilling fluid, and the mixture is fully stirred at a speed of 6000 r / min for 20 minutes to disperse into the oil-based drilling fluid.

[0106] Example 2

[0107] The target reservoir B of a low-permeability oilfield in the East China Sea contains fractures with a width of 26μm. The peak distribution of the main seepage pores is in the range of 2-2.5μm. The peak distribution size of the water phase droplets in the oil-based drilling fluid used is 1.2μm, and the peak distribution size of the solid phase in the oil-based drilling fluid is 24μm.

[0108] The implementation process of the screen curtain closed reservoir protection method in this embodiment is as follows:

[0109] (1) Preparation of special reservoir protection materials for oil-based drilling fluids

[0110] The specific raw material ratio for preparing the reservoir protection material for oil-based drilling fluids is as follows: 50 parts by weight of non-spherical rigid embedded proppant, 35 parts by weight of microelastic plugging agent, 10 parts by weight of composite plugging agent, 5 parts by weight of spherical thermosensitive acid-soluble microcapsules, and 3 parts by weight of a wetting agent. The non-spherical rigid embedded proppant has an equilateral tetrahedral structure with lengths of 50 μm and 4 μm; the microelastic plugging agent has an equilateral tetrahedral structure with lengths of 50 μm and 4 μm; the composite plugging material has a particle size of 23.4-26 μm and 1.8-2 μm; and the spherical thermosensitive acid-soluble microcapsules have a particle size of 1 μm.

[0111] (2) First, a non-spherical rigid embedded proppant with a side length of 50 μm is added to the oil-based drilling fluid according to 5% of the mass of the oil-based drilling fluid, and the mixture is dispersed into the oil-based drilling fluid by stirring at a speed of 10,000 r / min for 30 minutes.

[0112] (3) Subsequently, a non-spherical rigid embedded proppant with a side length of 4 μm and a special reservoir protection material for oil-based drilling fluid was added to the oil-based drilling fluid at a mass ratio of 5% of the oil-based drilling fluid, and the mixture was fully stirred at a speed of 10,000 r / min for 30 minutes to disperse it into the oil-based drilling fluid.

[0113] Example 3

[0114] The target reservoir C of a low-permeability oilfield in the East China Sea has no fracture distribution, and the main seepage pore distribution peaks are in the three peak ranges of 1.6-1.8μm, 3.1-3.4μm, and 6.4-6.8μm. The peak distribution size of the water phase droplets in the oil-based drilling fluid used is 1.6μm, and the peak distribution size of the solid phase in the oil-based drilling fluid is 23μm.

[0115] The implementation process of the screen curtain closed reservoir protection method in this embodiment is as follows:

[0116] (1) Preparation of special reservoir protection materials for oil-based drilling fluids

[0117] The specific raw material ratios for preparing the reservoir protection material for oil-based drilling fluids are as follows: 40 parts by weight of non-spherical rigid embedded proppant, 30 parts by weight of microelastic plugging agent, 25 parts by weight of composite plugging agent, 5 parts by weight of spherical thermosensitive acid-soluble microcapsules, and 2 parts by weight of a wetting agent. The non-spherical rigid embedded proppant has an equilateral tetrahedral structure with lengths of 2.8μm, 5.6μm, and 11.5μm; the microelastic plugging agent has an equilateral tetrahedral structure with lengths of 2.8μm, 5.6μm, and 11.5μm; the composite plugging material has particle sizes of 1.4-1.6μm, 2.8-3.1μm, and 5.8-6.4μm; and the spherical thermosensitive acid-soluble microcapsules have a particle size of 0.8μm.

[0118] (2) First, a non-spherical rigid embedded proppant with a side length of 11.5 μm and a special reservoir protection material for oil-based drilling fluid was added to the oil-based drilling fluid according to 5% of the mass of the oil-based drilling fluid, and the mixture was fully stirred at a speed of 80,000 r / min for 30 minutes to disperse it into the oil-based drilling fluid.

[0119] (3) Subsequently, a non-spherical rigid embedded proppant with a side length of 5.6 μm and a special reservoir protection material for oil-based drilling fluid was added to the oil-based drilling fluid at a mass ratio of 5% of the oil-based drilling fluid, and the mixture was fully stirred at a speed of 80,000 r / min for 30 minutes and dispersed into the oil-based drilling fluid.

[0120] (4) Subsequently, a non-spherical rigid embedded proppant with a side length of 2.8 μm and a special reservoir protection material for oil-based drilling fluid was added to the oil-based drilling fluid at a mass ratio of 5% of the oil-based drilling fluid, and the mixture was fully stirred at a speed of 80,000 r / min for 30 minutes to disperse it into the oil-based drilling fluid.

[0121] Example 4

[0122] The difference between this embodiment and Example 1 is that, in the process of preparing the reservoir protection material for oil-based drilling fluid, the specific ratio of the raw materials is adjusted to: 45 parts by weight of non-spherical rigid embedded proppant, 20 parts by weight of micro-elastic plugging agent, 30 parts by weight of composite plugging agent, 5 parts by weight of spherical temperature-sensitive acid-soluble microcapsules, and 3 parts by weight of a wetting agent for combination; other oil field selection, raw materials, size selection and implementation process are the same as those in Example 1.

[0123] Example 5

[0124] The difference between this embodiment and embodiment 1 is that, in the process of preparing the reservoir protection material for oil-based drilling fluid, the specific ratio of the raw materials is adjusted to: 30 parts by weight of non-spherical rigid embedded proppant, 40 parts by weight of micro-elastic plugging agent, 25 parts by weight of composite plugging agent, 5 parts by weight of spherical temperature-sensitive acid-soluble microcapsules, and 3 parts by weight of a wetting agent for combination; other oil field selection, raw materials, size selection and implementation process are the same as those in embodiment 1.

[0125] Comparative Example 1

[0126] The target reservoir, Reservoir A in a low-permeability oilfield in the East China Sea, has no fractures. The peak distribution of the primary seepage pore size is in the 1.5-1.8 μm range. The peak distribution size of the aqueous phase droplets in the oil-based drilling fluid used is 0.8 μm, and the peak distribution size of the solid phase in the oil-based drilling fluid is 22 μm. Referring to the shielding and temporary plugging technology in the "Technology for Protecting Oil and Gas Reservoirs" (4th edition), as a reference for comparison with Example 1, the relevant materials are applicable to the materials of the present invention, and the particle size distribution is as shown in the "Technology for Protecting Oil and Gas Reservoirs" (4th edition).

[0127] Comparative Example 2

[0128] The difference between this comparative example and Example 1 is that, in the process of preparing the special reservoir protection material for oil-based drilling fluid, no non-spherical rigid embedded proppant is added to the raw materials, and the reduced weight portion is proportionally distributed to the micro-elastic plugging agent, the small-particle composite plugging agent and the spherical temperature-sensitive acid-soluble microcapsule; other oil field selection, raw materials, size selection and implementation process are the same as in Example 1.

[0129] Comparative Example 3

[0130] The difference between this comparative example and Example 1 is that, in the process of preparing the reservoir protection material for oil-based drilling fluid, no microelastic plugging agent is added to the raw materials, and the reduced weight portion is proportionally distributed to the non-spherical rigid embedded proppant, the composite plugging agent and the spherical temperature-sensitive acid-soluble microcapsule; other oil field selection, raw materials, size selection and implementation process are the same as in Example 1.

[0131] Comparative Example 4

[0132] The difference between this comparative example and Example 1 is that, in the process of preparing the special reservoir protection material for oil-based drilling fluid, no composite plugging agent is added to the raw materials, and the reduced weight portion is proportionally distributed to the micro non-spherical rigid embedded proppant, elastic plugging agent and spherical temperature-sensitive acid-soluble microcapsule; other oil field selection, raw materials, size selection and implementation process are the same as in Example 1.

[0133] Comparative Example 5

[0134] The difference between this comparative example and Example 1 is that, in the process of preparing the special reservoir protection material for oil-based drilling fluid, no spherical temperature-sensitive acid-soluble microcapsules are added to the raw materials, and the reduced weight is proportionally distributed to the non-spherical rigid embedded proppant, elastic plugging agent and particle size composite plugging agent; other oil field selection, raw materials, size selection and implementation process are the same as in Example 1.

[0135] The implementation effect analysis method is as follows:

[0136] (1) Cores and oil-based drilling fluids from the target reservoirs of Oilfield A, Oilfield B, and Oilfield C were collected indoors, and a comparative evaluation of the degree of reservoir damage was conducted with reference to the petroleum and natural gas industry standard for drilling fluid reservoir damage, "SY / T 6540-2002 Indoor Evaluation Method for Drilling and Completion Fluid Damage to Reservoirs."

[0137] (2) According to the implementation methods of Examples 1-5 and Comparative Example 1, the drilling fluid damage evaluation was carried out using the collected cores and drilling fluids, and compared with the oil-based drilling fluid (original) without curtain sealing reservoir protection optimization. The experimental results are shown in Table 1.

[0138] Table 1

[0139]

[0140] The test results show that:

[0141] (1) In oil fields A, B and C, the oil-based drilling fluid (original) that was not optimized for curtain-sealed reservoir protection had a permeability recovery rate of 29.76-45.85% after the experiment. However, after the oil-based drilling fluid was optimized by the curtain-sealed reservoir protection method of the present invention, the permeability recovery rate measured after the experiment was more than 89%. Obviously, the curtain-sealed reservoir protection method provided by the present invention can form a dense curtain outside the pore throat or fracture entrance end with a large permeability contribution rate, thereby reducing the irreversible granularity and emulsification blockage caused by the invasion of foreign particles into the low permeability reservoir from the source, thereby meeting the needs of oil-based drilling fluid reservoir protection and effectively improving the reservoir protection effect of oil-based drilling fluid in low permeability reservoirs under multi-size seepage channel conditions.

[0142] (2) By comparing Example 1 with Comparative Example 1, it can be seen that the permeability recovery rate measured in Example 1 is 89.65%, while the permeability recovery rate measured in Comparative Example 1 is only 72.54%, indicating that the specific screen curtain closed reservoir protection method provided by the present invention has a better protection effect on the oil-based drilling fluid reservoir.

[0143] (3) By comparing Example 1 with Comparative Examples 2-5, it can be seen that the permeability recovery rates measured in Comparative Examples 2-5 are 91.85-94.63%, indicating that the present invention can exert a synergistic effect by compounding the proppant, microelastic plugging agent, composite plugging agent and microcapsule, so that the obtained special reservoir protection material for oil-based drilling fluid can well protect the oil-based drilling fluid reservoir. When any of the above raw material components is missing, the synergistic effect will be destroyed, so that when the special reservoir protection material for oil-based drilling fluid is applied to the oil-based drilling fluid of the low-permeability and extra-low-permeability reservoir, its effect on reservoir protection is significantly reduced.

[0144] The applicant declares that the above is only a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention fall within the scope of protection and disclosure of the present invention.

Claims

1. A reservoir protection material for oil-based drilling fluid, characterized in that: The raw materials for preparing the special reservoir protection material for oil-based drilling fluid include proppant, microelastic plugging agent, composite plugging agent and microcapsule.

2. The special reservoir protection material for oil-based drilling fluid according to claim 1, characterized in that: The raw materials for preparing the special reservoir protection material for oil-based drilling fluid include the following components in parts by weight:

3. The special reservoir protection material for oil-based drilling fluid according to claim 1 or 2, characterized in that: The proppant is a non-spherical rigid embedded proppant; Preferably, the non-spherical shape is a cone shape; Preferably, the rigid embedding proppant comprises any one or a combination of at least two of a metal material, a fiberglass material or a polycarbonate; Preferably, the microelastic plugging agent is a plugging agent that has the ability to change its shape within 20% under the temperature and pressure conditions of the target layer; Preferably, the microelastic plugging agent comprises any one of polyvinyl chloride, polyetheretherketone, epoxy resin, carbon fiber or polyaramid, or a combination of at least two thereof; Preferably, the composite plugging agent includes any one of quartz sand, calcium carbonate, polyester fiber or graphite, or a combination of at least two thereof; Preferably, the microcapsules are spherical thermosensitive acid-soluble microcapsules; Preferably, the spherical thermosensitive acid-soluble microcapsules are microcapsule-type solid acids composed of a core material and a wrapping material; Preferably, the core material comprises aminosulfonic acid; Preferably, the wrapping material comprises a double-layer wrapping material formed of paraffin wax and ethyl cellulose.

4. The special reservoir protection material for oil-based drilling fluid according to any one of claims 1 to 3, characterized in that: The raw materials for preparing the special reservoir protection material for oil-based drilling fluid also include a wetting agent; Preferably, the content of the wetting agent is 1-3 parts by weight; Preferably, the wetting agent comprises a fatty acid wetting agent and / or a phospholipid wetting agent.

5. A method for selecting raw material size, characterized in that: The method for selecting the raw material size is used to select and prepare the size of the raw material proppant, microelastic plugging agent, composite plugging agent and microcapsule for preparing the reservoir protection material for oil-based drilling fluid according to any one of claims 1 to 4.

6. The method for selecting raw material size according to claim 5, characterized in that: The method comprises the following steps: (1) Determine the distribution status and peak value of cracks or main seepage pores; (2) selecting the proppant size according to the distribution state and peak value of step (1); (3) selecting the size of the microelastic plugging agent according to the proppant size described in step (2); (4) selecting the size of the composite plugging agent according to the distribution state and peak value described in step (1); (5) selecting the size of the microcapsules according to the distribution state and peak value described in step (1); The order of steps (2), (4) and (5) is not limited.

7. The method for selecting raw material size according to claim 5 or 6, characterized in that: The method for selecting the proppant size in step (2) comprises: If the fracture or main seepage pore presents a single peak distribution state, the shortest side length of the proppant is 1.5-2 times the fracture opening or the main seepage pore diameter; If the fracture or main seepage pore presents a multi-peak distribution state, the shortest side dimension of the proppant forms a multi-scale distribution according to each peak value; Preferably, the size of the microelastic plugging agent in step (3) is consistent with the size of the proppant; Preferably, the method for selecting the size of the composite plugging agent in step (4) includes selecting according to the reservoir protection particle size of the fracture or main seepage pore d90-d100; Preferably, the reservoir protection granularity of d90-d100 is the granularity value corresponding to 90-100% of the cumulative distribution of the size of the fracture or main seepage channel; Preferably, the method for selecting the size of the microcapsules in step (5) includes selecting according to 0.5 times the minimum peak size of the cracks or main seepage pores in a unimodal or multimodal distribution state.

8. A method for preparing the reservoir protective material for oil-based drilling fluid according to any one of claims 1 to 4, the method comprising the following steps: First, the sizes of proppants, microelastic plugging agents, composite plugging agents and microcapsules are selected and prepared according to the method for selecting the raw material size described in any one of claims 5 to 7, and then the proppants, microelastic plugging agents, composite plugging agents and microcapsules prepared as above are mixed to obtain the reservoir protection material dedicated to oil-based drilling fluid.

9. A method for protecting a reservoir enclosed by a screen curtain, characterized in that: The protection method comprises the following steps: a. Determine the distribution of water phase droplets and solid phase particles in oil-based drilling fluid; b. The special reservoir protection material for oil-based drilling fluid is prepared by the preparation method of the special reservoir protection material for oil-based drilling fluid according to claim 8; c. Observe the overlap between the oil-based drilling fluid special reservoir protection material and the water phase droplet and solid phase particle size distribution in step a, and reduce the amount of the oil-based drilling fluid special reservoir protection material added in the overlapping part accordingly; d. Add the special reservoir protection material for oil-based drilling fluid described in step b into the oil-based drilling fluid and stir.

10. The method for protecting a curtain-enclosed reservoir according to claim 9, characterized in that: The distribution of the aqueous phase droplets in step a is observed using a polarizing microscope; Preferably, the solid phase particle distribution in step a is obtained by analyzing with a laser particle size analyzer; Preferably, the amount of the special reservoir protection material added in step d is determined according to the distribution state of the fractures or main seepage pores; Preferably, the method for determining the amount of the added reservoir protection material for the oil-based drilling fluid specifically comprises: If the cracks or main seepage pores are distributed in a single peak, after encountering the target well reservoir section, add the special reservoir protection material for oil-based drilling fluid into the oil-based drilling fluid at 5-8% of the mass of the oil-based drilling fluid, and stir at a speed of 6000r / min for 20min; If the cracks or main seepage pores are multi-peaked, add the special reservoir protection material for oil-based drilling fluid to the oil-based drilling fluid according to the number of peaks at 5% of the mass of each peak oil-based drilling fluid, and stir them at a speed of 6000-10000r / min for 20-30min; Preferably, when the fractures or main seepage pores present multi-peak distribution, the special reservoir protection material is added to the oil-based drilling fluid in stages in the order of peak values ​​from large to small.

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