Method for treating thick intercalations of laminated salt rock

Abstract

The application discloses a treatment method for thick interbeds of layered salt rock. The treatment method comprises the following steps: high-pressure water jet slotting is performed on the area where the thick interbeds of the layered salt rock are drilled, so as to form a slot on the thick interbeds; high-pressure water jet is performed on the slot to form a fracture, until the thick interbeds collapse. In the technical scheme, the problem that the insoluble or hardly soluble interbeds cannot collapse in the process of cavity forming of a salt cavern gas storage, which leads to the incapability of rapid upward expansion and the difficulty in forming an ideal cavity shape, is effectively solved. The drilling combination drilling tool is used, and the engineering operation is safe and controllable. The high-pressure water jet slotting and fracturing have good adaptability to the treatment of the interbeds in the salt cavern. The method can be widely used for rapid treatment of the insoluble interbeds encountered in the process of cavity forming of a salt cavern gas storage.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of layered salt rock cavity making, and in particular to a layered salt rock thick interlayer processing method. BACKGROUND

[0002] Underground gas storage has the functions of seasonal peak regulation, emergency supply, strategic reserve and market regulation. The salt cavern type gas storage has the characteristics of good stability, moderate burial depth and large single cavity volume, and is popularized in China. However, the insoluble interlayer is developed in the rock salt stratum in China. In the process of water injection and cavity washing, when dissolved to the lower part of the interlayer, it is blocked by the insoluble interlayer and cannot continue to develop according to the designed shape. This causes the time and position of the interlayer collapse to be uncontrollable, which has a great adverse effect on the stability of the salt cavern gas storage and the later operation. Therefore, it is of great significance to seek a fast and efficient thick interlayer collapse processing method to ensure the safety of the salt cavern gas storage.

[0003] In the related art, the processing method aiming at making the thick interlayer collapse is to perform lateral branch drilling in the library drilling stage, and to form effective holes and connected cracks in the thick interlayer through small range fracturing.

[0004] Looking at the above processing method, the efficiency of causing the thick interlayer to collapse is low, that is, it is difficult to form the collapse of the thick interlayer. SUMMARY

[0005] Therefore, the present application provides a layered salt rock thick interlayer processing method, which can effectively reduce the difficulty of collapse.

[0006] The present application provides a layered salt rock thick interlayer processing method, comprising:

[0007] High-pressure water jet slotting is performed on the area of the thick interlayer of the layered salt rock drilled by a borehole to form a slot on the thick interlayer;

[0008] High-pressure water jet is performed on the slot to form fracturing until the thick interlayer collapses.

[0009] Optionally, the slot is an annular slot.

[0010] Optionally, the high-pressure water jet slotting is performed by using a drill bit assembly, and the drill bit assembly comprises a drill bit for performing drilling, and an axial nozzle and a radial nozzle are opened on the drill bit, the axial nozzle is configured to spray low-pressure water flow for drilling, and the radial nozzle is configured to spray high-pressure water flow for slotting.

[0011] Optionally, the radial nozzle of the drill bit is lowered to a depth consistent with the middle depth of the target interlayer.

[0012] The processing method of the thick interlayer of the layered salt rock provided above utilizes the high-pressure water jet to cut the thick interlayer in the salt cavity, the existence of the slot greatly reduces the cracking pressure, and then the high-pressure water is continuously injected into the slot to perform the hydraulic fracturing of the interlayer, so that the problem that the interlayer cannot be collapsed and expanded upward quickly due to difficult dissolution and is difficult to form an ideal dissolved cavity shape in the process of forming a cavity of the salt cavern gas storage is effectively solved. The drilling combination drilling tool is adopted to integrate the drilling, cutting and fracturing processes, the high-pressure water jet cutting and fracturing process has good adaptability to the processing of the interlayer in the salt cavern, and the operation practicability is high. The process is environmentally friendly and has high cavity forming efficiency. The method can be widely used for collapsing various thick interlayers encountered in the cavity forming of the layered salt rock. BRIEF DESCRIPTION OF DRAWINGS

[0013] The technical solutions and other beneficial effects of the present application will be apparent from the following detailed description of specific embodiments of the present application, combined with the accompanying drawings.

[0014] Figure 1 The processing method flowchart provided for the embodiments of the present application.

[0015] Figure 2 The actual operation schematic diagram of the thick interlayer processing method provided for the embodiments of the present application.

[0016] In the drawings, the elements are identified as follows:

[0017] 1-high pressure water pump, 2-drilling machine rotary table, 3-surface casing, 4-intermediate casing, 5-working string, 6-drill bit, 7-salt layer, 8-thick interlayer, 9-dissolved cavity, 10-slot. DETAILED DESCRIPTION

[0018] The technical solutions in the embodiments of the present application will be described clearly and completely in combination with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0019] In the description of the present application, it should be understood that the terms “first” and “second” are used only for the purpose of description, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features limited by “first” and “second” can explicitly or implicitly include one or more of the features. In the description of the present application, the meaning of “multiple” is two or more, unless otherwise specifically limited.

[0020] In the description of the present application, it is necessary to explain that, unless otherwise explicitly specified and limited, the terms "mounting", "connection", "connecting" should be understood in a broad sense, for example, it can be fixed connection, or detachable connection, or integrally connected; it can be mechanical connection, or electrical connection or can communicate with each other; it can be directly connected, or indirectly connected through intermediate medium, it can be the internal communication of two elements or the interaction relationship between two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0021] The following disclosure provides many different embodiments or examples for implementing different structures of the present application. In order to simplify the disclosure of the present application, the components and arrangements of specific examples are described below. Of course, they are only examples, and the purpose is not to limit the present application. In addition, the present application can repeatedly refer to numbers and / or letters in different examples, and such repetition is for the purpose of simplification and clarity, which itself does not indicate the relationship between the various embodiments and / or arrangements discussed. In addition, the present application provides examples of various specific processes and materials, but those skilled in the art can realize the application of other processes and / or the use of other materials.

[0022] Before introducing the technical solutions of the present application, it is necessary to explain the background of the creation of the invention of the present application.

[0023] It is generally known that in the related art, the processing method aiming to make the thick interlayer collapse is as follows: (1) during the drilling stage, first drill a hole to the bottom of the salt rock; (2) on the basis of identifying the thickness and position of the interlayer, form holes in the thick interlayer in a certain range by physical action; (3) after the formation of holes in the thick interlayer, exploit the salt layer below the thick interlayer; inject diesel into the salt well to control the upward dissolution of the cavity and expand the diameter of the lower cavity to make the interlayer suspended and provide space for the collapse of the interlayer; (4) adjust the position of the salt well casing mouth to exploit the salt layer above the thick interlayer; use the oil cushion method to control the upward dissolution of the cavity; add a self-vibrating cavitation jet device to the lower part of the water injection pipe to adjust the direction of the downhole water injection to be horizontal and the water injection pressure to be 6-12 MPa to accelerate the dissolution of the cavity in the horizontal direction; (5) adjust the downhole water injection pipe mouth to the thick interlayer and use the self-vibrating cavitation jet device to directly erode the thick interlayer to further promote the dissolution and peeling of the thick interlayer, wherein a certain amount of chemical substances for accelerating the dissolution of the interlayer material are optionally added to the water solution injected into the well. In this processing method, holes are first formed in the thick interlayer by physical action, and then the lower layer of the thick interlayer is suspended and the upper layer of the thick interlayer is chemically eroded.

[0024] The present inventors have found, through repeated experiments on the above-mentioned related art treatment method, that: first, the pores generated by physical action of the thick interlayer gradually close over time. Second, chemical erosion of the thick interlayer is inherently slow, as it involves dissolving the components that make up the thick interlayer. Third, whether the pores are formed by chemical erosion or physical action, the direction of crack propagation caused by these means is not directional or regular, which makes it difficult to form large-scale cracks that determine collapse, and usually only intermittent and discontinuous local cracks are formed, reducing the efficiency of collapse.

[0025] Based on the above-mentioned awareness of the inventors of the above-mentioned problems, the present inventors have proposed a treatment method that uses high-pressure water jets to cut slots in the thick interlayer 8 in the salt cavity, which greatly reduces the cracking pressure of the slot 10, and then continuously injects high-pressure water jets into the slot 10 to perform hydraulic fracturing of the interlayer. Since the action site of the high-pressure water jet is the location of the slot 10, the hydraulic fracturing caused by the high-pressure water jet will gradually expand in all directions along the slot 10, and the flow direction of the high-pressure water jet constrains the direction of expansion, making it easier to produce larger cracks and reducing the difficulty of collapse of the thick interlayer 8. Thus, the present invention is created.

[0026] Reference Figure 1 The present application provides a treatment method for a layered salt rock thick interlayer 8, comprising:

[0027] High-pressure water jet cutting is performed on the area of the thick interlayer 8 of the layered salt rock that has been drilled, to form a slot 10 on the thick interlayer 8.

[0028] High-pressure water jets are applied to the slot 10 to form fractures until the thick interlayer 8 collapses.

[0029] The distribution position of the thick interlayer 8 in the layered salt rock is common knowledge. Specifically, the upper and lower layers of the thick interlayer 8 are salt layers 7, which refer to difficultly soluble or insoluble rock layers with a thickness of 3-30 m, but are not limited to this thickness.

[0030] As a demonstrable implementation, the slot 10 is a ring-shaped slot 10.

[0031] In this way, through the "ring shape" of the slot 10, the fracturing force generated when the high-pressure water jet is used to act on the slot 10 can cause the slot 10 to expand uniformly in all directions, forming large-scale cracks sufficient to cause the thick interlayer 8 to collapse.

[0032] Reference Figure 2In a typical embodiment, the high pressure water jet slotting described above is performed using a drill bit 6 assembly comprising a drill bit 6 for performing the drilling, the drill bit 6 having axial nozzles configured to jet low pressure water flow for drilling and radial nozzles configured to jet high pressure water flow for slotting.

[0033] Thus, during drilling, the drilling direction is the axial direction, and the low pressure water flow from the axial nozzles can directly act on the drilling direction (i.e. the vertical direction). When drilling to the position of the thick interlayer 8, the radial nozzles are activated to generate radial high pressure water jet, so that the action on the thick interlayer 8 is in the horizontal direction.

[0034] It should be understood that the "axial" and "radial" directions herein refer to the direction along the drill pipe connecting the drill bit 6 assembly.

[0035] As for other components matched with the drill bit 6 assembly, common forms widely used in geological drilling can be used, which will be demonstrated later.

[0036] In a typical embodiment, the radial nozzles of the drill bit 6 are lowered to a depth consistent with the middle depth of the thick interlayer 8.

[0037] In this way, the slot 10 of the thick interlayer 8 can cause the crack propagation direction to expand uniformly in all directions.

[0038] Now, the operation process of the present application will be described in a common application scenario. It should be noted that this common embodiment cannot be used as a basis for understanding the necessity features claimed by the present application to solve the technical problems, but only as an example.

[0039] Reference Figure 1 The method for processing the thick interlayer in the embodiment comprises the following steps:

[0040] S1, connect the working string 5, and connect the drill and slot integrated drill bit 6 to the bottom end of the working string.

[0041] S2, connect the inner annulus of the working string 5 to the outlet of the high pressure water pump 1 through the high pressure water pipe, and connect the annulus wellhead of the intermediate pipe 4 to the inlet of the high pressure water pump 1.

[0042] S3, start the high pressure water pump 1 and the drilling machine rotary table 2.

[0043] S4, sequentially lower the string 5 from the intermediate casing 4. The depth is parallel to the target depth of the interlayer and the position of the drill bit nozzles.

[0044] S5, after reaching the target depth, fixing the wellhead part, increasing the pumping pressure of the high-pressure water pump 1, opening the high-pressure water channel of the drilling and cutting integrated drill bit 6, opening the radial nozzle, and rotating the high-pressure water jet cutting nozzle with the drill bit, and cutting the interlayer in the radial direction. The interlayer in China's rock salt is mainly mudstone layer and gypsum layer, which is mostly in honeycomb structure after water dissolution. The jet pressure impacts and damages the interlayer rock skeleton, and washes and carries out the silt, making a radial slot in the middle of the interlayer. The existence of the slot greatly reduces the interlayer rock mass cracking pressure.

[0045] S6, continuously injecting high-pressure water into the slot to make the slot crack extend in the horizontal direction and cause the interlayer to collapse.

[0046] The above is only the preferred specific embodiment of the present application, but the protection scope of the present application is not limited to this. Any person skilled in the art can easily think of changes or replacements within the technical scope disclosed in the present application, which should be covered within the protection scope of the present application.

Claims

1. A method for treating a thick interlayer of a layered salt rock, characterized in that, Comprising: Implementing high pressure water jet slotting on the area of a thick interlayer of a bedded salt rock that is drilled to form an annular slot on the thick interlayer; Implementing high pressure water jet on the slot to form a fracture until the thick interlayer collapses; Implementing the high pressure water jet slotting using a drill bit assembly comprising a drill bit to perform drilling, the drill bit having an axial nozzle and radial nozzles, the axial nozzle configured to jet a low pressure water flow for drilling, the radial nozzles configured to jet a high pressure water flow for slotting; The radial nozzles of the drill bit are lowered to a depth that coincides with the middle depth of the target interlayer to form the annular slot.

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