A method for quickly forming a cavity in a salt cavern repository layer

Abstract

The application discloses a layered quick cavity forming method for a salt cavern storage. First, a slant well and a vertical well are constructed; then a plurality of horizontal wells are connected to the slant well and the vertical well by horizontal directional drilling at different depths of a target salt layer; and a plurality of porous hoses are respectively lowered into the plurality of horizontal wells. The jetting range of the porous hoses is controlled by adjusting the water injection flow rate of the porous hoses, so that the plurality of horizontal segments are uniformly dissolved; the dissolved salt rock in the brine is discharged to the ground surface through a water outlet pipe, and the insoluble sediments fall and accumulate at the bottom of the horizontal cavity; and the lower interlayer and / or salt layer collapses under the action of the brine soaking and the gravity of the sediments. The plurality of horizontal cavities are simultaneously dissolved by injecting fresh water into the plurality of horizontal cavities through the porous hoses, so that the simultaneous dissolution of the cavities is controlled, and a regular cavity shape is formed. Finally, the plurality of horizontal cavities are completed and connected, and a large salt cavern storage is formed. The application improves the utilization rate and the cavity forming efficiency of the salt cavern, and reduces the cavity forming cost.

Description

Technical Field

[0001] This invention relates to the field of underground oil and gas storage technology, and in particular to a method for rapid cavity creation in a layered salt cavern storage facility. Background Technology

[0002] Underground energy storage facilities are oil or natural gas reservoirs formed by reinjecting oil or natural gas into underground spaces for long-term preservation. Due to their large storage capacity, strong peak-shaving capabilities, and high security, underground energy storage facilities integrate functions such as seasonal peak shaving, emergency gas supply, and strategic energy reserves. Because of their irreplaceable role in peak shaving and ensuring gas supply security, the construction of underground energy storage facilities has received significant attention from various countries. Currently, there are four main types of underground energy storage facilities: depleted oil and gas reservoirs, aquifers, salt caverns, and abandoned mine pits. Salt cavern reservoirs formed through water-soluble extraction have significant advantages. Since salt cavern reservoirs are typically located 800-2000 meters underground, the salt rock possesses good rheological properties and plasticity, allowing certain cracks in the salt rock to self-heal under appropriate temperature and pressure. Unlike salt dome-type reservoirs abroad, my country's salt rock strata are mostly layered salt rocks, with thick salt layers but relatively low purity, numerous interlayers, and high impurity content. Therefore, constructing large-scale underground energy storage facilities in layered salt rock strata presents numerous challenges.

[0003] Current methods for constructing salt cavern reservoirs involve building a vertical well and a directional well, connecting the two wells using directional drilling technology, and injecting an oil pad to prevent excessive dissolution. This method results in minimal salt dissolution in the horizontal well section, low salt rock utilization, and a significant waste of salt rock resources. Furthermore, the need to inject a diesel fuel pad pollutes water resources and increases cavity construction costs. Thick interlayers may prevent salt dissolution, severely impacting cavity construction efficiency. Therefore, existing cavity construction methods are unsuitable for my country's layered salt rock formations and cannot meet the country's energy reserve requirements for salt caverns. Thus, improving the utilization rate and cavity construction efficiency of salt caverns while reducing construction costs is of great significance for the construction of underground salt cavern reservoirs.

[0004] Based on existing horizontal well drilling technology, constructing a salt cavern storage facility with a capacity of approximately 300,000 cubic meters would take about five years. This excessively long construction period severely impacts the planning and development of my country's underground energy reserves and fails to meet the urgent need for large-scale salt cavern storage facilities in layered salt rock. Improving the construction speed and reducing the construction cost of salt caverns in thick salt layers are crucial issues that urgently need to be addressed by those skilled in the art. Summary of the Invention

[0005] This invention provides a rapid cavity-building method for layered salt cavern storage, which improves the utilization rate and cavity-building efficiency of salt caverns while reducing cavity-building costs.

[0006] This invention provides a method for rapid cavity creation in a salt cavern storage layer, comprising:

[0007] Construct one inclined shaft and one vertical shaft;

[0008] Multiple horizontal wells are drilled at different depths of the target salt layer to connect the inclined well and the vertical well;

[0009] A porous hose is inserted into each of the multiple horizontal wells. The injection flow rate of the porous hose is adjusted to control the jet range of the porous hose, so that the multiple horizontal sections are uniformly dissolved.

[0010] Salt rocks dissolve in brine and are discharged to the surface through outlet pipes. Insoluble sediments fall and accumulate at the bottom of the horizontal cavity. The lower interlayer and / or salt layer collapse under the soaking of brine and the gravity of the sediments, and multiple horizontal cavities are completed and connected to form a large salt cavern reservoir.

[0011] Specifically, the horizontal directional drilling of multiple horizontal wells at different depths of the target salt layer, connecting the deviated well and the vertical well, includes:

[0012] Using directional drilling technology, multiple horizontal wells are drilled at different depths of the target salt layer to connect the inclined well and the vertical well.

[0013] Specifically, the step of lowering porous hoses into the plurality of horizontal wells and controlling the jet range of the porous hoses by adjusting the water injection flow rate of the porous hoses includes:

[0014] A porous hose is inserted into each of the plurality of horizontal wells, and the porous hose is suspended above the brine. A water injection pipe is inserted through the inclined well, and the jet range of the porous hose is controlled by adjusting the water injection flow rate of the water injection pipe.

[0015] Specifically, it also includes:

[0016] The water outlet pipe is lowered through the vertical well.

[0017] Specifically, after the formation of a large salt cavern reservoir, the process also includes:

[0018] Remove the porous hose from the inclined shaft; or perform a pipe cutting operation, leaving the horizontal section of the porous hose inside the horizontal cavity.

[0019] Specifically, the porous flexible tube is made of silicone or polyethylene.

[0020] One or more technical solutions provided in this invention have at least the following technical effects or advantages:

[0021] This invention provides a rapid, layered cavity-building method for salt cavern reservoirs, applicable to the construction of large salt cavern reservoirs in thick salt layers. It primarily utilizes multiple horizontal wells to simultaneously construct salt cavern cavities in layers. Specifically:

[0022] First, one inclined well and one vertical well are constructed. Then, multiple horizontal wells are drilled at different depths of the target salt layer, connecting the inclined and vertical wells. Porous hoses are inserted into each of the horizontal wells, suspended above the brine, without the need for a diesel fuel pad to control dissolution. The injection flow rate of the porous hoses is adjusted to control the jetting range, ensuring uniform dissolution across multiple horizontal sections. The dissolved salt rock is discharged to the surface through an outlet pipe, while insoluble sediments fall and accumulate at the bottom of the horizontal cavities. The lower interlayer and / or salt layer collapse under the influence of brine immersion and the gravity of the sediments. Due to buoyancy and the material of the hoses, the dissolution of the upper salt layer and the accumulation of sediment do not affect the water injection into the hoses. Fresh water is injected into multiple horizontal cavities through the porous hoses to dissolve them simultaneously, controlling the simultaneous dissolution within the cavities to form a regular cavity shape. Finally, the multiple horizontal cavities are completed and connected, forming a large salt cavern reservoir. The process is simple to operate and easy to implement in the field.

[0023] The advantages of this invention include:

[0024] 1. This invention utilizes directional drilling technology to drill horizontal wells at different strata, connecting vertical and inclined wells in layers, dissolving multiple layers of salt rock simultaneously, and greatly improving cavity-making efficiency.

[0025] 2. The multi-hole hose of the horizontal well is suspended on the surface of the brine. The jet range of the water outlet of the multi-hole hose is controlled by adjusting the water injection flow rate, so that the salt layer is dissolved evenly.

[0026] 3. During the cavity-building process of this invention, there is no need to add a diesel gasket layer to control the dissolution, which will not contaminate the brine. The porous hose can be reused, reducing the cost of cavity building.

[0027] 4. This invention is particularly suitable for rapid cavity creation in thick salt layers. It can also be used for cavity creation in layered salt rocks with thick interlayers. The sediment accumulates at the bottom of the horizontal cavity, and under the soaking effect of brine, it can solve the problem of the thick interlayers being difficult to collapse.

[0028] 5. Rapidly constructing large-scale storage tanks in thick salt layers improves the utilization rate of salt rock resources and reduces the cost of cavity construction. Attached Figure Description

[0029] Figure 1 A flowchart of a rapid cavity-building method for salt cavern storage layering provided in an embodiment of the present invention;

[0030] Figure 2 This is a schematic diagram of the layered trench construction structure in the rapid cavity construction method for salt cavern storage provided in this embodiment of the invention;

[0031] Figure 3 This is a schematic diagram of the early stage of layered water-soluble cavity creation in the rapid cavity creation method for salt cavern storage provided in this embodiment of the invention;

[0032] Figure 4 Schematic diagram in the middle stage of layered water dissolution cavity formation in the salt cavern storage layered rapid cavity formation method provided by the embodiment of the present invention;

[0033] Figure 5 Schematic diagram in the later stage of layered water dissolution cavity formation in the salt cavern storage layered rapid cavity formation method provided by the embodiment of the present invention;

[0034] Wherein, 1 - inclined well, 2 - vertical well, 3 - water injection pipe, 4 - water outlet pipe, 5 - porous hose, 6 - water outlet holes of porous hose, 7 - first horizontal cavity, 8 - second horizontal cavity, 9 - third horizontal cavity, 10 - insoluble sediment, 11 - final salt cavern cavity. Specific implementation manners

[0035] The embodiment of the present invention provides a salt cavern storage layered rapid cavity formation method, which improves the utilization rate and cavity formation efficiency of the salt cavern while reducing the cavity formation cost.

[0036] In order to better understand the above technical solution, the above technical solution will be described in detail below in conjunction with the specification drawings and specific implementation manners.

[0037] See Figure 1 , the salt cavern storage layered rapid cavity formation method provided by the embodiment of the present invention includes:

[0038] Step S110: Construct an inclined well and a vertical well;

[0039] Step S120: Horizontally directionally drill multiple horizontal wells at different depths of the target salt layer to connect the inclined well and the vertical well;

[0040] Specifically describe this step. Horizontally directionally drilling multiple horizontal wells at different depths of the target salt layer to connect the inclined well and the vertical well includes:

[0041] Using directional drilling technology, horizontally directionally drill multiple horizontal wells at different depths of the target salt layer to connect the inclined well and the vertical well.

[0042] Step S130: Lower porous hoses into multiple horizontal wells respectively, and control the jet range of the porous hoses by adjusting the water injection flow rate of the porous hoses to make the multiple horizontal sections dissolve evenly upward;

[0043] Specifically describe this step. Lowering porous hoses into multiple horizontal wells respectively and controlling the jet range of the porous hoses by adjusting the water injection flow rate of the porous hoses includes:

[0044] Lower porous hoses into multiple horizontal wells respectively, and the porous hoses are suspended on the top of the brine; lower the water injection pipe through the inclined well, and control the jet range of the porous hoses by adjusting the water injection flow rate of the water injection pipe.

[0045] The embodiments of the present invention will be described in detail, and will also include:

[0046] Water inlet and outlet pipes are installed through a vertical well.

[0047] Step S140: Salt rock dissolves in brine and is discharged to the surface through the outlet pipe. Insoluble sediments fall and accumulate at the bottom of the horizontal cavity. The lower interlayer and / or salt layer collapse under the immersion of brine and the gravity of the sediments. Multiple horizontal cavities are completed and connected to form a large salt cavern reservoir.

[0048] To further illustrate the embodiments of the present invention, after forming a large salt cavern storage tank, the method further includes:

[0049] Remove the perforated hose from the inclined shaft; or, perform a pipe cutting operation, leaving the horizontal section of the perforated hose inside the horizontal cavity.

[0050] In this embodiment, the porous flexible tube is made of silicone or polyethylene.

[0051] The following is a further description of the embodiments of the present invention. The embodiments of the present invention provide a rapid, layered cavity-building method for large salt cavern reservoirs. This method is applied to cavity building in horizontal wells. (See also...) Figure 2 , Figure 3 , Figure 4 and Figure 5 The specific steps are as follows:

[0052] 1. In a salt mine in Huai'an with a salt layer thickness greater than 300m, a slanted shaft 1 and a vertical shaft 2 were first drilled. At approximately 80m intervals between salt layer thicknesses, horizontal directional drilling technology was used to connect the two wells at different salt layer thicknesses. A water injection pipe 3 was lowered through the slanted shaft 1 and connected to a directional perforated hose 5 in multiple horizontal sections. The perforated hose 5 covered the entire horizontal section. The salt layer was divided into a first horizontal cavity 7, a second horizontal cavity 8, and a third horizontal cavity 9 from bottom to top by the multiple perforated hoses.

[0053] 2. Fresh water is injected into the porous hoses 5 in each horizontal section through the water injection pipe 3, causing simultaneous dissolution in the first horizontal cavity 7, the second horizontal cavity 8, and the third horizontal cavity 9. Under the buoyancy of the water, the porous hoses 5 in multiple horizontal cavities are all located on the upper surface of the brine. Increasing the water injection flow rate increases the jet range of the water outlet 6 of the porous hoses, flushing the salt layer and interlayer surface to control the uniform dissolution within the cavities. The brine is discharged to the surface through the water outlet pipe 4.

[0054] 3. As the salt layer dissolves upwards, insoluble deposits 10 fall and accumulate at the bottom, forming the final salt cavern cavity 11. When the dissolved thickness of salt layers at different levels approaches the interval thickness of 80m, the lower salt layer or interlayer will collapse under the gravity of the insoluble deposits 10, causing the insoluble deposits 10 to fall to the bottom of the cave. Due to the buoyancy of the brine, the porous hose 5 will remain above the brine in the cave and will not be affected by the falling deposits.

[0055] 4. After all the horizontal cavities in all layers have been constructed and fused together, the porous hoses 5 of the first horizontal cavity 7, the second horizontal cavity 8, and the third horizontal cavity 9 are removed from the inclined shaft 1. If removal is difficult, a pipe cutting operation is performed, leaving the porous hoses 5 of the horizontal sections inside the horizontal cavities.

[0056] The embodiments of the present invention are applicable to the construction of underground storage facilities for natural gas, oil or compressed air energy storage.

[0057] Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including both the preferred embodiments and all changes and modifications falling within the scope of the invention.

[0058] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A method of rapid layered cavernization for salt cavern storage, characterized by, The method comprises the following steps: building a slant well and a vertical well; drilling multiple horizontal wells at different depth levels of a target salt layer to connect the slant well and the vertical well; lowering a porous hose into each of the multiple horizontal wells to control the jetting range of the porous hose by adjusting the water injection flow rate of the porous hose, so as to uniformly dissolve the multiple horizontal sections; the material of the porous hose is silica gel or polyethylene; the step of lowering the porous hose into each of the multiple horizontal wells to control the jetting range of the porous hose by adjusting the water injection flow rate of the porous hose comprises the step of lowering the porous hose into each of the multiple horizontal wells, and the porous hose is suspended at the top of the brine; lowering a water injection pipe into the slant well, and connecting the multiple horizontal sections with the directional porous hose, so that the porous hose covers the entire horizontal section; and controlling the jetting range of the porous hose by adjusting the water injection flow rate of the water injection pipe; lowering a water outlet pipe into the vertical well; the dissolved salt rock in the brine is discharged to the ground surface through the water outlet pipe, and the insoluble sediments fall and accumulate at the bottom of the horizontal cavity; the lower interlayer and / or the salt layer collapse under the action of the brine immersion and the gravity of the sediments, the multiple horizontal cavities are completed and connected, and a large salt cavern reservoir is formed.

2. The salt cavern reservoir zonal rapid cave-in method of claim 1, wherein, the step of drilling the multiple horizontal wells at different depth levels of the target salt layer to connect the slant well and the vertical well comprises the steps of: drilling the multiple horizontal wells at different depth levels of the target salt layer to connect the slant well and the vertical well by using the directional drilling technology.

3. The salt cavern reservoir zonal rapid cave-in method of claim 1, wherein, after the large salt cavern reservoir is formed, the method further comprises the steps of: removing the porous hose from the slant well; or performing a pipe cutting operation to leave the porous hose in the horizontal cavity.

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