Brine layer top plate blocking method

Abstract

The invention discloses a bittern layer top plate plugging method, and relates to the technical field of bittern layer top plate plugging, and the bittern layer top plate plugging method comprises the following steps: determining the mechanical strength and pore permeability characteristics of a salt layer top plate according to the mechanical strength test and physical property characteristic analysis of the salt layer top plate; the radius and height of the salt cavern are determined according to the designed well spacing, row spacing and security pillars, and therefore the salt bed roof blocking range is determined; drilling a group of transverse horizontal butt joint wells; the other set of horizontal butt joint wells are drilled out, the set of horizontal butt joint wells perpendicularly intersect with the face where the horizontal sections of the horizontal butt joint wells in the third step are located, and a two-layer three-dimensional space structure is formed; the horizontal butt joint well is in butt joint with the lower portion of the target well; and a plugging agent is injected into the horizontal butt joint well and the target well for plugging. The two layers of horizontal butt joint well groups are implemented, a three-dimensional plugging body is formed, all cracks of the whole salt cavern roof can be covered, a gas and halogen upward flowing channel can be blocked, and the plugging quality of the bittern layer roof is effectively improved.

Description

Technical Field

[0001] The invention relates to the technical field of brine layer roof plugging, in particular to a brine layer roof plugging method. Background Art

[0002] In recent years, with the release of relevant policy documents such as the national three-rate index, higher requirements have been put forward for the development of salt mines, and salt caverns, as high-quality underground storage spaces, have been increasingly valued. High-quality salt caverns meet the following requirements (pressure bearing capacity 10MPa, salt cavern volume 1 million m 3 , salt layer depth 1000m), but also faced a series of problems. First of all, my country's rock salt is not like Europe and the United States in the form of salt domes. Most of it is enriched in the form of single layers or interlayers. During the development process, rock salt is mainly dissolved above, supplemented by lateral dissolution, and almost insoluble downward, resulting in rock salt quickly exposing the salt layer roof. During the mining process, after fresh water is injected out of the casing, a short-circuit cycle is formed on the upper roof, and no rock salt is dissolved downward, thereby reducing the brine concentration. At the same time, in recent years, as a high-quality underground storage space, the stability and airtightness of salt caverns are the first considerations. However, the roof of the domestic marine stratum salt layer is carbonate rock strata and gypsum, which has developed pores and fractures and is not a good cap layer, so it needs to be transformed.

[0003] At present, the domestic transformation is mainly carried out on wellbore, and the transformation technology for salt layer roof is still very limited. Existing technology drills a large number of vertical wells on the salt layer roof and injects cement for plugging. This method plugs within a plane and has a certain effect on general roof, but it cannot completely cover all areas and there is still a risk of roof leakage. Summary of the invention

[0004] The crack system of the salt layer roof extends to a certain length in both the longitudinal and transverse directions. If conventional vertical wells or directional wells are used for cementing, this method is used for plugging in one plane, which has a certain effect on the general roof, but it cannot completely cover all areas, and there is still a risk of roof leakage. The purpose of the present invention is to overcome the shortcomings of the prior art and provide a method for plugging the brine layer roof, implement two-layer horizontal docking well groups, form a three-dimensional plugging body, which can cover all cracks in the entire salt cavern roof, cut off the gas brine upward channel, effectively improve the plugging quality, and provide reliable technical support for the efficient mining of rock salt and the comprehensive utilization of salt caverns.

[0005] The object of the present invention is achieved through the following technical scheme: a method for plugging the roof of a brine layer, the method comprising the following steps:

[0006] S1. Determine the mechanical strength and porosity characteristics of the salt layer roof.

[0007] S2. Determine the radius and height of the salt cavern, thereby determining the sealing range of the salt layer roof.

[0008] S3. Drill a set of horizontal docking wells.

[0009] S4, drilling another group of horizontal docking wells, which respectively intersect with the planes where the horizontal docking wells in step S3 are located. If there is a certain height difference between the horizontal sections of the two groups of horizontal docking wells, a two-layer three-dimensional spatial structure is formed. If there is no height difference between the horizontal sections of the two groups of horizontal docking wells, a single-layer three-dimensional spatial structure is formed.

[0010] S5. The horizontal docking well is docked with the lower part of the target well.

[0011] S6. Inject plugging agent into the horizontal docking well and the target well.

[0012] In the step S1, the mechanical strength and porosity characteristics of the salt layer roof are determined based on the mechanical strength test and physical property characteristics analysis.

[0013] In step S2, the radius and height of the salt cavern are determined according to the geological conditions of the salt cavern, the designed well spacing, row spacing, safety pillars and cavity structure parameters.

[0014] In step S3, the two groups of horizontal docking wells drilled are arranged in a diamond or square well layout, which can better cover the area affected by the salt cavern roof, which is both economical and efficient.

[0015] A group of horizontally connected wells includes several horizontally connected wells, the distance between each horizontally connected well does not exceed 300m, and the distance between adjacent horizontally connected wells does not exceed 300m.

[0016] The horizontal docking well comprises a vertical well section, an inclined well section and a horizontal section, and is docked and connected with the target well to form a "U" shape.

[0017] In step S5, a casing is provided at the lower part of the target well, and a precise positioning instrument is placed in the casing. The horizontal docking well is docked with the precise positioning instrument in the lower casing of the target well, providing convenience for the horizontal docking well.

[0018] The casing is made of glass fiber reinforced plastic casing.

[0019] In step S6, a high-strength plugging agent with good air tightness is injected into the horizontal docking well and the target well to improve the plugging effect.

[0020] The beneficial effects of the present invention are:

[0021] 1. The two groups of horizontal butt-jointed wells of the present invention form a plane plus three-dimensional network to form an overall plugging, improve the plugging efficiency, ensure the stability and airtightness of the salt cavern, increase the brine concentration and plug the brine layer roof. At the same time, the two groups of horizontal butt-jointed well technology are used to communicate several independent and unconnected cracks that need to be plugged, thereby improving the plugging quality.

[0022] 2. The present invention provides convenience for horizontal docking wells through glass fiber reinforced plastic casing and precise positioning instruments. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a schematic diagram of the structure of two groups of horizontal docking wells of the present invention;

[0024] Figure 2 It is a diamond-shaped well arrangement;

[0025] Figure 3 The well layout is square. DETAILED DESCRIPTION

[0026] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. The components of the embodiments of the present invention generally described and shown in the drawings here can be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the claimed invention, but merely represents selected embodiments of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0027] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

[0028] In one embodiment of the present application:

[0029] like Figures 1 to 3 As shown, a method for plugging the roof of a brine layer comprises the following steps:

[0030] S1. According to the mechanical strength test and physical property analysis of the salt layer roof, its mechanical strength and porosity characteristics are determined.

[0031] S2. According to the geological conditions of the salt cavern, the designed well spacing, row spacing, safety pillars and cavity structure parameters, the radius and height of the salt cavern are determined, thereby determining the sealing range of the salt layer roof.

[0032] S3. Drill a set of horizontal docking wells.

[0033] S4, drill another group of horizontal docking wells, which are respectively formed with the horizontal docking wells in step S3 to form a vertical intersection, and there is a certain height difference between the horizontal sections of the two groups of horizontal docking wells, which is determined according to the thickness and lithology of the salt layer roof, not less than 5 meters, and the two groups of horizontal docking wells are respectively arranged in the upper and lower layers of the salt layer roof, forming a two-layer three-dimensional spatial structure, and the two groups of horizontal docking wells can be well types such as vertical wells and directional wells. The two groups of horizontal docking wells after crossing form a regular interwoven structure like a fishing net or a football net, covering and plugging all the holes and seams of the salt layer roof; a group of horizontal docking wells includes several horizontal docking wells, and the well spacing of each horizontal docking well does not exceed 300m, and the row spacing between adjacent horizontal docking wells does not exceed 300m, and each horizontal docking well includes a vertical well section, an inclined well section and a horizontal section, which are connected to the target well to form a "U" shape. After the horizontal docking well is built, perforation, acidification and hydraulic fracturing can also be added according to the actual situation to make the wellbore track communicate with all the cracks in the salt layer roof. The two groups of horizontal butt-jointed wells drilled are arranged in a diamond or square pattern, which can better cover the affected area of ​​the salt cavern roof (i.e., the brine layer roof). For example, the diamond well pattern can significantly improve the plugging degree on the plane of the salt cavern roof by expanding the well spacing in the direction of the principal stress of the formation and shortening the well spacing in the direction perpendicular to the principal stress. The diamond well pattern is suitable for blocks with relatively developed fractures. Enlarging the well spacing in the direction of the fractures can increase the extension length of the plugging cement slurry, allowing the cement to reach each fracture faster and deeper. The square well pattern is suitable for formations where natural microfractures are not developed and the anisotropy of planar permeability is not obvious. In this case, the square well pattern can provide a stable and effective plugging well spacing. The square well pattern, due to its regular geometric shape, makes implementation and management relatively simple. Figure 2 As shown in the figure, the white circle represents the horizontal docking well, the straight line represents the docking connection line, and the dotted line represents the control range of the plugged well. Figure 3 As shown, the white circles represent horizontal docking wells, and the dotted lines represent docking connection lines. At the same time, the well layout is not limited to diamond or square. Triangles and other polygonal well layouts can be set according to the number and form of cracks that need to be blocked and the actual situation on site.

[0034] S5. A fiberglass casing is provided at the lower part of the target well, and an RMRS precise positioning instrument is placed in the fiberglass casing. The horizontal docking well is docked with the precise positioning instrument in the fiberglass casing at the lower part of the target well. The target well can be a vertical well, a directional well or a horizontal well.

[0035] S6. Inject high-strength and air-tight plugging agents into the horizontal docking well and the target well for plugging.

[0036] The above is only an embodiment of the present invention. It should be understood that the present invention is not limited to the form disclosed herein, and should not be regarded as excluding other embodiments, but can be used in various other combinations, modifications and environments, and can be modified within the scope of the concept described herein through the above teachings or the technology or knowledge of the relevant field. The changes and modifications made by those skilled in the art shall not deviate from the spirit and scope of the present invention, and shall be within the scope of protection of the claims attached to the present invention.

Claims

1. A method for plugging the roof of a brine layer, characterized in that: The following steps are involved: S1. Determine the mechanical strength and porosity characteristics of the salt layer roof; S2. Determine the radius and height of the salt cavern, thereby determining the plugging range of the salt layer roof; S3, drilling a set of horizontal butt-jointed wells; S4, drilling another group of horizontal docking wells, which respectively intersect with the planes where the horizontal docking wells in step S3 are located, and form a two-layer three-dimensional spatial structure; S5. The horizontal docking well is docked with the lower part of the target well; S6. Inject plugging agent into the horizontal docking well and the target well.

2. The method for sealing the roof of a brine layer according to claim 1, characterized in that: In the step S1, the mechanical strength and porosity characteristics of the salt layer roof are determined based on the mechanical strength test and physical property characteristics analysis.

3. The method for sealing the roof of a brine layer according to claim 1, characterized in that: In step S2, the radius and height of the salt cavern are determined according to the geological conditions of the salt cavern, the designed well spacing, row spacing, safety pillars and cavity structure parameters.

4. The method for sealing the roof of a brine layer according to claim 1, characterized in that: The two groups of horizontal butt-joint wells drilled are arranged in a diamond or square pattern.

5. A method for sealing a brine layer roof according to claim 1 or 4, characterized in that: A group of horizontally connected wells includes several horizontally connected wells, the distance between each horizontally connected well does not exceed 300m, and the distance between adjacent horizontally connected wells does not exceed 300m.

6. A method for sealing the roof of a brine layer according to claim 5, characterized in that: The horizontal docking well includes a vertical well section, an inclined well section and a horizontal section, and is docked and connected with the target well to form a "U" shape.

7. The method for sealing the roof of a brine layer according to claim 1, characterized in that: In step S5, a casing is provided at the lower part of the target well, a precise positioning instrument is placed in the casing, and the lower part of the target well is docked with the horizontal docking well through the casing and the precise positioning instrument.

8. The method for sealing the roof of a brine layer according to claim 7, characterized in that: The casing is made of glass fiber reinforced plastic casing.

9. The method for sealing the roof of a brine layer according to claim 1, characterized in that: In the step S6, a high-strength plugging agent with good air tightness is injected into the horizontal docking well.

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