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Shale fracturing sample coupled with bedding and natural fracture, and its preparation method and process

发布日期:2020-01-07 13:12 Document serial number: 19641813 Release date: 2020-01-07 13:12
Shale fracturing sample coupled with bedding and natural fracture, and its preparation method and process

The present invention relates to the field of artificial fracturing the specimen, particularly, to a shale fracturing the specimen preparation process one kind of bedding and natural fractures coupled, and to shale fracturing samples one kind of bedding and natural fractures coupling.



Background technique:

During the deposition of shale gas reservoirs, weak surfaces such as bedding and micro-fractures are developed. These weak surfaces affect the propagation direction of hydraulic fracturing fractures. According to the bedding development characteristics, mineral composition, and rock mechanical properties of the Longtan Formation complex coal measures in the Sichuan Basin, artificial fracturing samples were prepared in the laboratory and a true triaxial hydraulic fracturing physical simulation experiment was performed to understand the shale reservoir. , An important means to simulate shale mechanical characteristics and efficiently develop shale oil and gas. At present, the core prepared in the laboratory is cast by mixing cement and quartz sand in proportion. The fracturing specimen prepared by this method has better homogeneous and isotropic characteristics. However, this artificial fracturing specimen cannot simulate the shale layer. Characteristics such as micro-fractures and micro-fractures are not suitable for simulating shale cores with micro-fractures and multi-layers.



Technical realization elements:

The purpose of the present invention is to provide a method for preparing shale fracturing samples coupled with bedding and natural fractures, so as to prepare shale fracturing samples capable of simulating coupling between bedding and natural fractures.

In order to achieve the above object, one aspect of the present invention provides a method for preparing a shale fracturing sample coupled with bedding and natural fractures, wherein the method includes:

Step 1: fully mix cement and quartz sand;

Step 2: In the mixture of cement and quartz sand, add a smaller size a-type shredded paper, a larger size b-type shredded paper and water, and then mix well;

In step three, the mixture prepared in step two and a plurality of stacked spacers are placed in the mold;

Step four: after the mixture is allowed to set for the first predetermined time, the separator is withdrawn, and after the mixture is dried for the second predetermined time, a bedding developed artificial shale core is formed.

Optionally, the thickness of the separator is 1mm-2mm.

Optionally, an included angle between the partition plate and the bottom of the mold is 80 degrees to 90 degrees.

Optionally, the width of the partition is equal to the width of the cavity of the mold, and the height of the partition is greater than the height of the cavity of the mold. In step three, the partition is pressed against the Stencil plate.

Alternatively, in step three, a plurality of the separators are first inserted into the mold, and then the mixture is injected into the mold.

Optionally, the mold includes two side plates facing each other, and the side plate is provided with a limiting groove for receiving the partition plate.

Optionally, the mold includes two end plates facing each other, the end plate and the side plate are detachably connected, the end plate and the side plate are plugged into the bottom plate, and the preparation The method further includes step five: disassembling the end plate and the side plate to remove the shale fracturing sample coupled with bedding and natural fractures.

Optionally, the mass ratio of the cement and the quartz sand is 2: 3-3: 2.

Alternatively, the cement is composite portland cement, and the particle size of the quartz sand is 40 mesh to 80 mesh.

Optionally, the length of the a-type shredded paper is 5mm-8mm, the width is 3mm-5mm, and the length of the b-type shredded paper is 10mm-20mm, and the width is 5mm-10mm.

Optionally, the a-type shredded sheet and the b-type shredded sheet are made by cutting 70 g of a4 printing paper or 80 g of a4 printing paper.

Optionally, the mass ratio of the a-type shredded paper to the mixture of cement and quartz sand is 0.1% -0.2%, and the mass ratio of the b-type shredded paper to the mixture of cement and quartz sand is 0.05% -0.1%. The mass ratio of water to cement and quartz sand mixture is 18% -20%.

Optionally, in step one, the cement and quartz sand are stirred using a quartz sand mixer for 10 minutes to 15 minutes.

Optionally, the first predetermined time is 60 minutes to 120 minutes, and the second predetermined time is 15 days to 20 days.

In addition, the present invention also provides a shale fracturing sample coupled with bedding and natural fractures, wherein the shale fracturing sample coupled with bedding and natural fractures passes the bedding and natural fractures described in the above scheme. Fracture coupling shale fracturing sample preparation method.

Through the above technical solution, a type of shredded paper, b-shaped shredded paper and water are added to the mixture of cement and quartz sand, and then mixed uniformly to simulate natural cracks of arbitrary appearance; a partition is inserted into the unsolidified preparation material After the separator is pulled out, adjacent layers can be glued together to form a layered structure, so as to make a shale fracturing sample coupled with layered and natural fractures.

BRIEF DESCRIPTION OF THE DRAWINGS

1 is a schematic structural diagram of a mold and a separator according to an embodiment of the present invention;

2 is a schematic structural diagram of a side plate according to an embodiment of the present invention;

3 is a schematic structural diagram of an end plate according to an embodiment of the present invention;

4 is a schematic structural diagram of a bottom plate according to an embodiment of the present invention;

FIG. 5 is a shale fracturing sample coupled with bedding and natural fractures according to an embodiment of the present invention.

Reference Signs

1 mold 2 partition

3-layer shale fracturing sample coupled with natural fractures

11 side plate 12 end plate

13 limit slot 14 bottom plate

15 hook 16 socket

31a crack 32b crack

33 layers

detailed description

Hereinafter, specific embodiments of the present invention will be described in detail with reference to the drawings. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present invention, and are not intended to limit the present invention.

The invention provides a method for preparing a shale fracturing sample coupled with bedding and natural fractures, wherein the method includes:

Step 1: fully mix cement and quartz sand;

Step 2: In the mixture of cement and quartz sand, add a smaller size a-type shredded paper, a larger size b-type shredded paper and water, and then mix well;

In step three, the mixture prepared in step two and a plurality of stacked spacers 2 are placed in the mold 1;

Step four, after the mixture is allowed to set for the first predetermined time, the separator 2 is pulled out, and after the mixture is dried for the second predetermined time, a shale fracturing sample coupled with bedding and natural fractures is formed.

Cement and quartz sand can constitute the main structural components of shale. Two kinds of shredded paper can simulate cracks of different sizes in the artificial core of the final molding. In particular, this solution is intended to prepare shales with micro-cracks and multiple layers Fracturing the sample, injecting a mixture (including cement, quartz sand, shredded paper, water) and a separator 2 (into the bottom of the mold 1, so that the unsolidified mixture is separated into multiple layers by the separator, After a predetermined time, the separator 2 is drawn from the mixture, so that the multilayered, incompletely solidified mixture can be glued together to a certain extent. By continuing to dry for a second predetermined time, micro-cracks, multilayered structures can be formed. Shale fracturing sample coupled with natural fractures.

Optionally, the thickness of the separator 2 is 1 mm-2 mm. The thickness of the separator 2 determines the distance between the adjacent two layers of the mixture, which can affect the bonding strength of the adjacent two layers of the mixture. Optionally, the thickness of the separator 2 is 1mm-2mm, of course, the separator 2 can also A smaller thickness is selected, and preferably, the thickness of the separator 2 is 1 mm. The partition 2 is a plate with a smooth surface and is made of a material that does not react with the mixture, such as a steel plate, a plastic plate, or the like.

Optionally, an included angle between the partition plate 2 and the bottom of the mold 1 is 80 degrees to 90 degrees. By setting the angle between the partition plate 2 and the bottom of the mold 1 (bottom plate 14), the formed bedding can have a certain angle with the bottom of the mold 1, which is convenient for subsequent experimental operations. The plurality of partitions 2 may be parallel to each other, or may form different angles with the bottom of the mold 1, respectively.

Wherein, the width of the partition 2 is equal to the width of the inner cavity of the mold 1, and the height of the partition 2 is greater than the height of the inner cavity of the mold 1. In step three, the partition 2 is pressed against To the bottom plate 14 of the mold 1. Referring to FIG. 1, the mold 1 may be a hexahedron, for example, a cube. The top of the mold 1 can allow the mixture of cement, quartz sand, etc. to be injected, and the partition 2 can be inserted through the opening. The bottom is the bottom plate 14, which can carry Mixture and separator 2. Wherein, the width of the partition 2 is equal to the width of the internal cavity of the mold 1, so that the mixture therein can be completely separated, and the height of the partition 2 is greater than the height of the internal cavity of the mold 1, and the upper end thereof can be removed from the mold 1. Convex, which can completely separate the multi-layered mixture and facilitate extraction from the mold 1.

The size of the internal cavity of the mold 1 may be 300mmx300mmx300mm or 400mmx400mmx400mm. Correspondingly, an artificial core with a size of 300mmx300mmx300mm or 400mmx400mmx400mm may be prepared.

According to an embodiment of the present invention, in step three, a plurality of the separators 2 are first inserted into the mold 1, and then the mixture is injected into the mold 1. After the plurality of partitions 2 are fixed at a predetermined interval and angle in the mold 1, the mixture is injected between the partitions 2 and between the partitions 2 and the mold 1, so that the mixture is temporarily separated into a multilayer structure. . In other embodiments, a certain amount of the mixture can be injected into the bottom of the mold 1, and then the separator 2 is inserted at a predetermined interval and angle, that is, the separator 2 is stabilized by the mixture at the bottom, and then the mold 1 The mixture is injected into the mold so that the mixture fills the mold 1, and the separator 2 can also be used to separate the mixture into multiple layers.

Further, the mold 1 includes two side plates 11 opposite to each other, and the side plate 11 is provided with a limiting groove 13 for receiving the partition plate 2 inserted therein. The limiting groove 13 can accommodate the two edges of the partition 2 to slide therein, that is, to limit the angle of the partition 2 relative to the bottom of the mold 1 and the interval between adjacent partitions 2 to prevent the partition 2 from moving relative to the target position when inserted. , Resulting in inaccurate angles. In addition, referring to FIG. 2, the side plate 11 may be provided with a plurality of sets of limiting grooves 13 having different angles and different intervals, so that the partition plate 2 may be inserted at different angles and intervals, that is, separated at different angles and intervals. The mixture is poured into a mold 1. In addition, the bottom plate 14 can also be provided with a limiting groove 13, and the partition plate 2 can also be positioned.

Further, the mold 1 includes two end plates 12 opposite to each other, the end plate 12 and the side plate 11 are detachably connected, and the end plate 12 and the side plate 11 are inserted into the bottom plate. In step 14, the preparation method further includes step 5: disassembling the end plate 12 and the side plate 11 to take out the bedding artificial shale core. Figures 2, 3, and 4 show the structure of the side plate 11, the end plate 12, and the bottom plate 14, respectively. The side plate 11 and the end plate 12 are detachably enclosed into a frame structure, and the side plate 11 and the end plate 12 can be detachably inserted into the bottom plate 14, so that after the mixture in the mold 1 is solidified and formed, the side plate 11 and the end plate 12 can be easily removed from the bottom plate 14 to facilitate the removal of the artificial core.

Specifically, the lower edge of the side plate 11 and the end plate 12 is provided with a protruding plug portion, and the bottom plate 14 is provided with a socket corresponding to the plug portion, thereby allowing the side plate 11 and the end plate 12 to be perpendicular to The bottom plate 14 is inserted into the bottom plate 14 in a vertical or vertical direction; the side of the side plate 11 is provided with a socket 16, and the side edge of the end plate 12 is provided with a protruding hook 15 corresponding to the socket, and the hook 15 It includes a horizontal extension portion and a hook portion protruding upward from the upper side of the extension portion. After the hook 15 is inserted into the socket 16, it can be stopped on the side plate 11 by the upper hook portion to prevent the side plate 11 and the end The board 12 comes off. In other embodiments, a hook 15 may be provided on the side plate 11, and a socket 16 may be provided on the end plate 12.

Wherein, the mass ratio of the cement and the quartz sand is 2: 3-3: 2. By selecting the ratio of cement to quartz sand, artificial cores of different composition types can be prepared.

Alternatively, the cement is composite portland cement, and the particle size of the quartz sand is 40 mesh to 80 mesh. The cement is a composite portland cement, for example, pc.pc32.5r. The particle size of quartz sand is 40 mesh-80 mesh, for example, 40 mesh, 45 mesh, 50 mesh, 70 mesh, 80 mesh, and the like.

Specifically, the length of the a-type shredded paper is 5mm-8mm, the width is 3mm-5mm, and the length of the b-type shredded paper is 10mm-20mm, and the width is 5mm-10mm. A-type shreds and b-type shreds can be cut from the same kind of paper and have different sizes to simulate cracks of different sizes.

Further, the a-type shredded sheet and the b-type shredded sheet are made by cutting 70 g of a4 printing paper or 80 g of a4 printing paper. The a-type shreds and the b-type shreds are made of printing paper, for example, 70 g of a4 printing paper or 80 g of a4 printing paper, that is, a single sheet of a4 printing paper with a weight of about 70 g or 80 g.

In addition, the mass ratio of the a-type shredded paper to the mixture of cement and quartz sand is 0.1% -0.2%, the mass ratio of the b-type shredded paper to the mixture of cement and quartz sand is 0.05% -0.1%, and the water The mass ratio with cement and quartz sand mixture is 18% -20%.

Wherein, in step one, the cement and quartz sand are stirred by using a quartz sand mixer for 10 minutes to 15 minutes. Quartz sand mixer should be used for the mixing and mixing of the hard quartz sand. The stirring time is 10-15 minutes (10, 11, 12, 13, 14, 15 minutes, etc.), so that the cement and quartz sand are fully mixed.

In addition, the first predetermined time is 60-120 minutes, and the second predetermined time is 15 days-20 days. The first predetermined time is the initial solidification time of the mixture added to the mold 1, which has a significant effect on the bonding of the adjacent two layers of the mixture after the separator 2 is pulled out. By adjusting the length of the first predetermined time, the adjacent The bonding strength of the two-layer mixture, that is, the bonding strength at the layering. The second predetermined time is the time required for the mixture to fully dry and solidify.

In addition, the present invention also provides a shale fracturing sample coupled with bedding and natural fractures, wherein the shale fracturing sample coupled with bedding and natural fractures passes the bedding and natural fractures described in the above scheme. Fracture coupling shale fracturing sample preparation method. FIG. 5 shows a prepared shale fracturing sample coupled with bedding and natural fractures, in which an a-type fracture 31, a b-type fracture 32, and a bedding 33 are formed.

The preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings, but the present invention is not limited thereto. Within the scope of the technical concept of the present invention, a variety of simple modifications can be made to the technical solution of the present invention, including the combination of various specific technical features in any suitable manner. In order to avoid unnecessary repetition, the present invention provides various possible combinations No further explanation. However, these simple deformations and combinations should also be regarded as the content disclosed by the present invention, and all belong to the protection scope of the present invention.

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