Preparation method and application of fine particles for improving connectivity of small fractures of reservoir

Abstract

The invention relates to a preparation method and application of fine particles for improving connectivity of fine fractures of a reservoir, and belongs to the field of fine particle materials. The fine particles are prepared from the following raw materials in parts by weight: 1%-4% of ferric oxide, 30%-35% of nanocarbon, 8%-12% of silicon, 20%-25% of silicon carbide, 2.5%-5% of gamma-aluminum oxide, 8%-15% of aluminum dihydrogen phosphate, 13%-20% of kaolin, 2.5%-3% of sepiolite, 1.0%-1.5% of tungsten trioxide and 3%-6% of tungsten carbide. The fine particle disclosed by the invention can still keep the shape in a high-strength and high-pressure environment, meets high closing stress and high suspension capacity of a stratum fracture under a reservoir transformation condition, can suspend in low-speed slickwater for a long time, and is particularly suitable for supporting the fine fracture in unconventional low-permeability oil and gas reservoir transformation.

Description

Technical Field

[0001] The invention belongs to the field of fine particle materials, and relates to a preparation method and application of fine particles for improving the connectivity of fine fractures in reservoirs. Background Art

[0002] The research and development of fine particle materials is crucial to fill the defects of existing proppants, especially in filling small cracks. Current proppants have some limitations and are difficult to enter small cracks. Traditional large-particle quartz sand or ceramsite proppants may have sedimentation problems in low-viscosity liquids, resulting in the inability to effectively fill these small cracks. Existing proppants can usually only support the main cracks and centimeter-level branch cracks in the formation after reservoir transformation. Existing proppant materials are generally quartz sand or ceramsite, and the mesh size is mostly less than or equal to 140 mesh. The apparent density of this type of traditional proppant is generally 2.6g / cm 3 -3.3g / cm 3 It is very easy to have a density of 1.012g / cm 3 During the reservoir transformation process, these traditional large-particle proppants cannot enter the small cracks extending from the branch fractures. After the construction is completed, the unused small cracks are closed due to the lack of proppants to support them, which reduces the effective fracture volume and the connectivity between the fractures.

[0003] According to Stokes sedimentation theory, In a liquid medium with the same viscosity and density, the smaller the density difference between the particles and the liquid and the smaller the particle size, the smaller the sedimentation velocity of the particles in the liquid medium, and the particles can easily enter the tiny cracks at the far end.

[0004] Therefore, it is necessary to develop a new type of material that can be suspended in low-viscosity liquids and can enter small cracks of various sizes to improve fracture connectivity. This new material should have an appropriate particle size and stability to ensure that it remains suspended in the liquid and can effectively fill small cracks, improve fracture conductivity, and improve reservoir reconstruction effects. Summary of the invention

[0005] In order to solve the technical problems mentioned in the background technology, the present invention provides a micron-sized material that is particularly designed to address the technical defects in the reservoir transformation process, such as the inability of proppants to enter micron-sized cracks for support, the laying and stacking in the reservoir transformation fluid, the poor support effect, and the small effective fracture network of the matrix. The purpose is to improve the connectivity of small cracks in the reservoir, solve the problem of effective utilization of small cracks, achieve mutual communication between small cracks, and improve the reservoir transformation effect.

[0006] In order to achieve the above object, the present invention provides the following technical solutions: A fine particle for improving the connectivity of fine cracks in a reservoir is made of the following raw materials in parts by weight: 1%-4% iron oxide, 30%-35% nanocarbon, 8%-12% silicon, 20%-25% silicon carbide, 2.5%-5% gamma-alumina, 8%-15% dihydrogen aluminum phosphate, 13%-20% kaolin, 2.5%-3% sepiolite, 1.0%-1.5% tungsten trioxide, and 3%-6% tungsten carbide.

[0007] The present invention also provides a method for preparing the fine particles for improving the connectivity of fine fractures in a reservoir, comprising the following steps: S1: weigh each raw material component according to the above ratio; S2: mixing the raw material components and then performing wet or dry molding to obtain a matrix body; S3: placing the base body into a calcining furnace and calcining it at 850°C; S4: cooling the base body after constant temperature calcination, and then performing dry grinding or wet grinding. The particle size distribution of the ground particles is normally distributed, the distribution curve is symmetrical, and the expected value μ is 1100 mesh, i.e. 13 μm; S5: The ground particles are placed in a calcining furnace again and calcined in vacuum at a temperature of 1200°C-1350°C; S6: cooling, filtering and washing; S7: After the material is dried by gas, fine particles are obtained.

[0008] Furthermore, the particles in the raw materials in the above S1 are crushed by a crusher and then prepared into small and medium-sized particles.

[0009] Furthermore, the calcination in the above S3 does not require vacuum conditions, and the calcination constant temperature time is 6-8h.

[0010] Furthermore, the grinding balls used in the planetary ball mill in S4 are any two of φ3, φ6, φ10, and φ20, the grinding speed is 1000rpm-3000rpm, and the grinding time is 13-16h.

[0011] Furthermore, the calcination constant temperature time in the above S5 is 1.5-2.5h.

[0012] Unless otherwise specified, the materials, reagents and experimental equipment involved in the present invention are all commercially available products in the field of chemical materials.

[0013] Compared with the existing materials for improving crack connectivity, the present invention has the following beneficial effects: 1. The present invention provides a micron-sized material with a large distribution scale, which can improve cracks of different widths, and the mesh number can reach up to 2000 mesh and the minimum mesh number can reach 200 mesh. In the fine particle seepage experiment, the average permeability of 200 mesh fine particles reached 62.84mD, the average permeability of 400 mesh fine particles reached 44.81mD, the average permeability of 800 mesh fine particles reached 24.85mD, the average permeability of 1200 mesh fine particles reached 15.78mD, and the average permeability of 1600 mesh fine particles reached 7.45mD.

[0014] 2. The present invention provides a high-strength special composite material that can maintain its shape under high-strength and high-pressure conditions. Its compressive strength can reach 70MPa, which meets the high closure stress of formation fractures under reservoir transformation conditions. It has a white powder appearance and a tap density of 1.25g / cm 3 -1.40g / cm 3 It has strong suspension ability and can be suspended for a long time in low-speed slippery water.

[0015] 3. The present invention provides a material with very small particle size and wide size distribution between 200 mesh and 2000 mesh, which is particularly suitable for supporting small cracks in the transformation of unconventional low-permeability oil and gas reservoirs.

[0016] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention and implement it according to the contents of the specification, the following is a detailed description of the preferred embodiments of the present invention in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 A schematic diagram of the appearance of a fine particle for improving the connectivity of fine fractures in a reservoir according to the present invention; Figure 2 A schematic diagram of the present invention showing a method of improving the connectivity of fine cracks in a reservoir by the entry of fine particles into fine cracks in the formation; Figure 3 This is a schematic diagram of the distribution state of fine particles and conventional proppants in a low-viscosity liquid for improving the connectivity of fine fractures in a reservoir according to the present invention. DETAILED DESCRIPTION

[0018] The technical solution of the present invention will be described clearly and completely below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0019] In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", and "third" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance.

[0020] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0021] In addition, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other. Example 1

[0022] According to the requirements of reservoir reconstruction technology, the following is the construction pumping procedure (part) of fine particles applied to a well. The well after construction achieved higher production than the adjacent wells:

[0023] Comparison with adjacent well production: Example 2

[0024] According to the requirements of reservoir reconstruction technology, the following is the construction pumping procedure (part) of fine particles applied to a well. The well after construction achieved higher production than the adjacent wells:

[0025] Comparison with adjacent well production:

[0026] From the comparative verification of the above embodiments, it can be clearly seen that the fine particles shown in the present invention can still maintain their shape in a high-intensity and high-pressure environment, meet the high closure stress of formation fractures under reservoir transformation conditions, have strong suspension ability, and can be suspended in low-speed slippery water for a long time. They are particularly suitable for supporting small cracks in the transformation of unconventional low-permeability oil and gas reservoirs.

[0027] In summary, the present invention provides a micron-sized material with a large distribution scale, which can improve cracks of different widths, and the mesh number can reach up to 2000 mesh and the minimum mesh number can reach 200 mesh. In the fine particle seepage experiment, the average permeability of 200 mesh fine particles reached 62.84mD, the average permeability of 400 mesh fine particles reached 44.81mD, the average permeability of 800 mesh fine particles reached 24.85mD, the average permeability of 1200 mesh fine particles reached 15.78mD, and the average permeability of 1600 mesh fine particles reached 7.45mD.

[0028] The present invention provides a high-strength special composite material that can maintain its shape under high-strength and high-pressure conditions. Its compressive strength can reach 70MPa, which meets the high closure stress of formation fractures under reservoir transformation conditions. It has a white powder appearance and a tap density of 1.25g / cm 3 -1.40g / cm 3 It has strong suspension ability and can be suspended for a long time in low-speed slippery water.

[0029] The invention provides a material with very small particle size and wide size distribution between 200 mesh and 2000 mesh, which is particularly suitable for supporting fine cracks in the transformation of unconventional low-permeability oil and gas reservoirs.

[0030] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0031] The above-mentioned embodiments only express several implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A fine particle for improving the connectivity of fine fractures in a reservoir, characterized in that: It is made of the following raw materials in parts by weight: 1%-4% iron oxide, 30%-35% nano carbon, 8%-12% silicon, 20%-25% silicon carbide, 2.5%-5% γ-alumina, 8%-15% dialuminum phosphate, 13%-20% kaolin, 2.5%-3% sepiolite, 1.0%-1.5% tungsten trioxide and 3%-6% tungsten carbide.

2. A method for preparing fine particles for improving the connectivity of fine fractures in a reservoir, characterized in that: The following steps are involved: S1: Weigh each raw material component according to the weight ratio, the weight ratio of each raw material is: iron oxide 1%-4%, nano carbon 30%-35%, silicon 8%-12%, silicon carbide 20%-25%, γ-alumina 2.5%-5%, aluminum dihydrogen phosphate 8%-15%, kaolin 13%-20%, sepiolite 2.5%-3%, tungsten trioxide 1.0%-1.5%, tungsten carbide 3%-6%; S2: mixing the raw material components and then performing wet or dry molding to obtain a matrix body; S3: placing the matrix green body into a calcining furnace and calcining it at a constant temperature of 850° C.; S4: cooling the base body after constant temperature calcination, and then performing dry grinding or wet grinding. The particle size distribution of the ground particles is normally distributed, the distribution curve is symmetrical, and the expected value μ is 1100 mesh, i.e. 13 μm; S5: placing the ground particles into a calcining furnace again, and calcining them at a temperature of 1200° C. to 1350° C. under vacuum; S6: After cooling the particles calcined at a constant temperature in vacuum, filtering and washing them, and drying them with coal gas to obtain fine particles.

3. The method for preparing fine particles for improving the connectivity of fine fractures in a reservoir according to claim 2, characterized in that: All raw materials in step S1 are crushed by a crusher.

4. The method for preparing fine particles for improving the connectivity of fine fractures in a reservoir according to claim 2, characterized in that: The calcination process in step S3 is performed under vacuum conditions or non-vacuum conditions, and the calcination time is 6-8 hours.

5. The method for preparing fine particles for improving the connectivity of fine fractures in a reservoir according to claim 2, characterized in that: The grinding process in step S4 adopts a planetary ball mill, and the grinding balls used are any two of φ3, φ6, φ10, and φ20, the grinding speed is 1000rpm-3000rpm, and the grinding time is 13-16h.

6. The method for preparing fine particles for improving the connectivity of fine fractures in a reservoir according to claim 2, characterized in that: The calcination time in step S5 is 1.5-2.5 hours.

7. Use of fine particles for improving connectivity of fine fractures in reservoirs as claimed in any one of claims 1 to 6, characterized in that: The fine particles are used to fill fine cracks, improve the conductivity of the cracks, and improve the reservoir transformation effect.

Images