A method for improving the recovery rate of trona in the construction of a natural trona mine type gas storage

Abstract

The present application relates to the technical field of soda mine recovery, and particularly relates to a method for improving the recovery rate of soda mine in the construction of natural soda mine type gas storage, which comprises the following steps: according to the development characteristics of multi-layer soda mine and the stability requirements of the gas storage, the target layer in the middle of the main area of the soda mine is planned as a construction layer; a straight well injection-production well pattern is arranged in the construction layer, and soda is recovered by combining a single straight well dissolution mining mode with a double straight well fracturing dissolution mining mode; a docking well connected injection-production well pattern is arranged in the lower layer of the construction layer, and soda is recovered by using a paired horizontal well docking dissolution mining mode or a straight well and horizontal well docking dissolution mining mode. According to the development characteristics of multi-layer soda mine and the stability requirements of the gas storage, and in combination with the distribution characteristics of the reservoir and the characteristics of different well types, a three-dimensional injection-production well pattern combination is formulated, and the overall resource recovery rate in the construction of multi-layer soda mine is improved by means of plane partition, vertical layering and individualized design of regional resource development.

Description

Technical Field

[0001] This invention relates to the field of alkali ore mining technology, and in particular to a method for improving the alkali ore recovery rate in the construction of natural alkali ore-type gas storage facilities. Background Technology

[0002] Since 2011, five oil wells in the northern part of the depression have confirmed the development of natural alkali deposits. To better evaluate natural alkali deposit A, well B was deployed in 2022 for both oil and alkali exploration. Core sampling was conducted continuously at depths of 1470.0-1832.3 meters, and core logging revealed 99.4 meters / 134 layers of natural alkali deposits, with individual layer thicknesses ranging from 0.1 to 4.12 meters and an average thickness of 0.74 meters. In 2023, relying on a geological exploration fund project, a total of 30 wells were deployed, with a total drilling footage of 52,000 meters. Eleven wells have been completed, and nine have encountered mineralization.

[0003] Natural alkali is readily soluble in water. Water-soluble development of natural alkali is similar to water-soluble salt mining, creating underground cavities and considering the construction of gas storage facilities. The main vertical stratigraphic section A of the alkali mine has been identified. The upper strata, sections I and II, are dominated by natural alkali with low salt content, making them favorable for development. The middle strata, section III, has the largest thickness and area, with symbiotic salt and alkali deposits, which is conducive to the coordinated development of natural alkali and the construction of gas storage facilities. The lower strata, section IV, also exhibits symbiotic salt and alkali deposits, with well-developed mudstone interlayers.

[0004] The natural alkali deposit A ​​has a large resource volume, a wide distribution range, and a moderate vertical burial depth. The alkali deposit in the middle III section is thick, which provides the basic geological conditions for the reconstruction of a gas storage facility. However, the integrated design of multi-layer natural alkali development and gas storage construction is still in the exploratory stage, and there is a lack of effective methods to improve the recovery rate of alkali deposits in the construction of natural alkali deposit-type gas storage facilities. Summary of the Invention

[0005] The purpose of this invention is to provide a method for improving the recovery rate of alkali ore in the construction of natural alkali ore-type gas storage facilities, by optimizing the well network combination configuration to improve the overall resource recovery rate.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] A method for improving the recovery rate of alkali ore in the construction of natural alkali ore-type gas storage facilities includes:

[0008] Based on the development characteristics of multi-layered alkali deposits and the stability requirements of gas storage facilities, the target stratum in the middle of the main alkali deposit area is planned as the reservoir construction stratum.

[0009] A vertical well injection-production well network is deployed in the reservoir layer, and a combination of single vertical well fracturing and alkali production mode and dual vertical well fracturing and alkali production mode is adopted.

[0010] Connecting wells are deployed in the lower strata of the reservoir layer to link the injection and production well network. Alkali extraction is carried out using a paired horizontal well docking solution extraction mode or a vertical well docking solution extraction mode.

[0011] Furthermore, the main distribution area of ​​alkali deposits, with a burial depth of 400m-2850m and a dip angle of 10-22°, is designated as the main alkali deposit area.

[0012] Furthermore, the strata in the central part of the main alkali mine area with a longitudinal thickness greater than 90m, a burial depth of 500-2000m, and meeting the requirements for planar distribution range are planned as reservoir construction strata.

[0013] Furthermore, the reservoir layer is more than 200m away from the fault location.

[0014] Furthermore, the upper layers of the reservoir will remain unused for the time being.

[0015] Furthermore, the vertical well injection and production well network deployed in the reservoir layer is an irregular well network, with at least 141 vertical well locations and a well spacing of 120-130m.

[0016] Furthermore, at least two alkali-collecting layers are set in the lower layer of the reservoir layer.

[0017] Furthermore, a network of injection and production wells is formed by connecting superimposed multi-branch horizontal wells with straight U-shaped wells in each alkali-producing layer. The production wells of the straight U-shaped wells are vertical wells, and the horizontal well sections of the injection wells are connected to the production wells. The superimposed multi-branch horizontal wells are set in the horizontal well sections of the injection wells.

[0018] Furthermore, a network of injection and production wells is formed by connecting superimposed multi-branch horizontal wells with flat U-shaped wells in each alkali-producing layer. The production wells and injection wells of the flat U-shaped wells are connected on the same horizontal plane, and the superimposed multi-branch horizontal wells are set in the connecting section between the production wells and the injection wells.

[0019] Furthermore, fishbone-shaped branch wells are deployed in each alkali-producing layer and connected to straight U-shaped wells to form an injection-production well network. The production wells of the straight U-shaped wells are vertical wells, the horizontal well sections of the injection wells are connected to the production wells, and the fishbone-shaped branch wells are set in the horizontal well sections of the injection wells.

[0020] Furthermore, fishbone-shaped branch wells are deployed in each alkaline layer and connected to flat U-shaped wells to form an injection-production well network. The production wells and injection wells of the flat U-shaped wells are connected on the same horizontal plane, and the fishbone-shaped branch wells are set in the connecting section between the production wells and the injection wells.

[0021] Furthermore, the method also includes: constructing a gas storage chamber in the area where the reservoir layer is buried at a depth of 850m-2000m.

[0022] Furthermore, the method also includes: designing the single-cavity parameters of the gas storage chamber based on the development characteristics of the multi-layered alkali ore and the stability requirements of the gas storage tank.

[0023] Furthermore, the single-cavity parameters of the gas storage chamber include: a single-cavity thickness greater than or equal to 90 μm, and a single-cavity diameter that is half the thickness of the single-cavity.

[0024] Furthermore, the method also includes: designing the single-cavity storage capacity parameters of the gas storage chamber based on the development characteristics of the multi-layered alkali ore and the stability requirements of the gas storage tank.

[0025] Furthermore, the storage parameters of the single cavity include: a single cavity ore body volume of 100,000-120,000 cubic meters, a single cavity storage capacity of 27-35 million cubic meters, a single cavity operating pressure of 12.2-29.6 MPa, and a working gas volume of 15-20 million cubic meters.

[0026] Furthermore, the upper and lower limit pressures of the single-chamber operation are calculated based on pressure gradients of 0.017 MPa / m and 0.007 MPa / m, respectively.

[0027] The technical effects and advantages of this invention are as follows:

[0028] (1) Based on the development characteristics of multi-layered alkali deposits and the stability requirements of gas storage facilities, a joint development model of converting gas storage facilities in the middle strata of the main alkali deposit area and sintering and mining in the lower strata was realized to maximize resource utilization and improve the investment efficiency of the oilfield.

[0029] (2) Based on the reservoir distribution characteristics and the characteristics of different well types, formulate a three-dimensional injection-production well network combination, and improve the overall resource recovery rate in the construction of multi-layer alkali mine reservoirs by dividing the area into planar zones, stratifying the vertical layers, and designing the regional resource utilization situation in a personalized manner.

[0030] (3) The method for improving the recovery rate of alkali ore in the construction of natural alkali ore gas storage provided by the present invention is scientific, reliable and feasible. It is particularly suitable for integrated development blocks of alkali leaching mining and storage construction with complex geological features of multi-layered systems, and has broad application prospects.

[0031] Other features and advantages of the invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention may be realized and obtained by means of the structures pointed out in the description, claims and drawings. Attached Figure Description

[0032] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0033] Figure 1This is a flowchart illustrating the method for improving the recovery rate of alkali ore in the construction of natural alkali ore-type gas storage facilities in this embodiment;

[0034] Figure 2 This is a schematic diagram illustrating the technical principle of improving the recovery rate of alkali ore in the construction of natural alkali ore-type gas storage facilities in this embodiment.

[0035] Figure 3 A schematic diagram of a single vertical well + dual vertical well combination karst mining;

[0036] Figure 4 This is a schematic diagram of a single vertical well slag extraction process.

[0037] Figure 5 This is a schematic diagram of fracturing and smelting production using two vertical wells.

[0038] Figure 6 A schematic diagram of a straight U-shaped well docking for sintering and extraction;

[0039] Figure 7 A schematic diagram of a flat U-shaped well docking and sintering process;

[0040] Figure 8 A schematic diagram of the wellbore structure for connecting a flat U-shaped well to a fusion extraction site;

[0041] Figure 9 A schematic diagram of a fishbone-shaped branch well and a straight U-shaped well docking for sintering and extraction.

[0042] Figure 10 This is a schematic diagram of a fishbone-shaped branch well and a flat U-shaped well docking for fusion extraction. Detailed Implementation

[0043] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0044] See Figure 1 and Figure 2 This invention provides a method for improving the recovery rate of alkali ore in the construction of natural alkali ore-type gas storage facilities. The method includes the following steps:

[0045] S1. Based on the development characteristics of multi-layered alkali deposits and the stability requirements of gas storage facilities, the target stratum in the middle of the main alkali deposit area is planned as the storage stratum.

[0046] S2. Deploy a vertical well injection-production well network in the reservoir layer and use a combination of single vertical well fracturing and alkali production mode and dual vertical well fracturing and alkali production mode.

[0047] S3. Deploy docking wells in the lower layer of the reservoir to connect the injection and production well network, and use a docking sol-production mode of paired horizontal wells or a docking sol-production mode of vertical wells and horizontal wells to produce alkali.

[0048] In this embodiment of the invention, based on the development characteristics of multi-layered alkali deposits and the stability requirements for solid mineral redevelopment into gas storage facilities, and through detailed geological studies of natural alkali deposits and reservoir characteristic analysis, a three-dimensional development model is adopted for planning and deployment. The central, stable ore layer of the main alkali deposit area is selected as the reservoir construction layer. A vertical injection-production well network is deployed in this reservoir construction layer, employing a combination of single vertical well fracturing and production modes for alkali production. Simultaneously, connecting wells are deployed in the lower strata of the reservoir construction layer to connect the injection-production well network, using either paired horizontal wells or a combination of vertical and horizontal wells for alkali production. Based on planar zoning, vertical stratification, and personalized design of regional resource utilization, a three-dimensional injection-production well network configuration of "central gas storage wells, with surrounding bottom-embedded wells" is achieved in the study block. This three-dimensional injection-production well network combination improves alkali production efficiency, thereby increasing the overall resource recovery rate during the reservoir construction process of multi-layered alkali deposits.

[0049] According to a preferred embodiment, in the construction of a natural alkali deposit-type gas storage facility, the main alkali deposit distribution area, with a burial depth of 400m-2850m and a dip angle of 10-22°, is designated as the main alkali deposit area. Furthermore, based on the development characteristics of multi-layered alkali deposits and the stability requirements of the gas storage facility, the strata in the central part of the main alkali deposit area with a longitudinal thickness greater than 90m, a burial depth of 500-2000m, and meeting the requirements for planar distribution range, are planned as the storage construction layers. The storage construction layers are located more than 200m away from fault locations.

[0050] See Figures 3-10 Considering the stability of the gas storage roof, the upper layer of the gas storage layer will not be used for the time being. The gas storage layer is a gas storage layer, and the lower layer of the gas storage layer is equipped with at least two alkali-collecting layers to form a combined alkali-collecting layer.

[0051] The natural alkali development technology solution adopted in this embodiment of the invention is as follows: combining the reservoir distribution characteristics and the characteristics of different well types, the optimal three-dimensional well network combination configuration is formulated, and the overall resource recovery rate in the construction of multi-layer alkali mines is improved by combining single vertical well convection dissolution production method, double vertical well fracturing and connection dissolution production method, vertical and horizontal well combination water dissolution method, and horizontal and horizontal well combination water dissolution method.

[0052] According to an embodiment of the present invention, the vertical well injection-production well network deployed in the reservoir layer is an irregular well network. Preferably, at least 141 vertical well locations are deployed, with a well spacing of 120-130m.

[0053] like Figures 3-5As shown, the reservoir formation employs a combination of single-well fracturing and alkali extraction modes. The single-well formation thickness ranges from 60-100m, while the fracturing formation thickness is >100m. The design is based on the following: 1) To maintain cavity stability, horizontal wells cannot be used for solid ore gas storage; 2) For single-well fracturing, given the limited cavity diameter (<50m), well spacing, and swept volume, with an annual extraction volume of 20,000-30,000 tons, a recommended formation thickness is <100m; 3) For fracturing and alkali extraction with dual-wells, which increases the swept volume and achieves higher alkali recovery, with an annual extraction volume of 40,000-50,000 tons, a recommended formation thickness is >100m.

[0054] In practical applications, the vertical well single-well convection method is a commonly used solution extraction technology. Vertical well development is simple, streamlined, labor-intensive, and easy to operate. Its production process can be divided into three stages: trenching, production, and aging. The methods can be either forward or reverse circulation water injection. Forward circulation water injection involves injecting water from the central pipe, with the brine at the bottom of the solution cavity returning to the surface through the gap between the casing and the central pipe. Forward circulation water injection is the primary method for single-well development to minimize the lateral solution angle. After the production well is put into production, reverse circulation water injection is generally used for well washing and trenching. Water injection methods are divided into continuous and intermittent injection. Continuous water injection means that water injection begins as soon as the well is put into production and continues until the ore is mined out. Continuous water injection is beneficial for protecting the roof and accelerating the dissolution of the ore layer. However, in mines with low brine concentration and good ore dissolution performance, continuous water injection should be used whenever possible. Intermittent water injection refers to the process of injecting water intermittently after a well is put into production. Intermittent water injection has low operating costs, but its ability to dissolve ore is poor and its dissolution rate is low. The solution cavity will generate negative pressure, which is not good for the protection of the roof. After production stops, a cavity will be generated in the upper part of the solution cavity due to the continued dissolution, forming negative pressure.

[0055] The dual-well fracturing and interconnection fracturing method can be divided into three stages: fracturing, propagation, and production. Its advantages include high production capacity, low production cost, and high and stable alkali-halite concentration. Secondly, it utilizes hydraulic pressure and dissolution to force open fractures in the ore layer, increasing permeability and continuously dissolving the ore to form necessary channels along the ore layer between wells. Its disadvantages include high fracturing cost and stringent fracturing requirements; otherwise, interconnection failure is likely. Currently, the success rate of interconnection fracturing is relatively high in reservoirs below 1000m, while above 1000m, vertical fractures are the main method, and horizontal interconnection is difficult.

[0056] Multi-branch wells refer to wells where two or more branch wells (secondary wells) are drilled from the bottom of a main wellbore to enter the oil and gas reservoir, and even tertiary sub-wells are drilled from the secondary wells and then reconnected to the main wellbore. Multi-branch wells allow the exploitation of multiple oil and gas layers from a single main wellbore, achieving multi-target or three-dimensional exploitation. Stacked multi-branch wells involve drilling multiple horizontal branch wells from a main wellbore in different formations in the same direction, while fishbone-shaped branch wells have multiple horizontal branch wells distributed in a feather-like (fishbone-like) pattern with their main wellbore.

[0057] According to a preferred embodiment of the present invention, such as Figures 6-8 As shown, a network of injection and production wells is formed by deploying superimposed multi-branch horizontal wells and connecting them with straight U-shaped wells in each alkali-producing layer. The production wells of the straight U-shaped wells are vertical wells, and the horizontal well sections of the injection wells are connected to the production wells. The superimposed multi-branch horizontal wells are set in the horizontal well sections of the injection wells.

[0058] The design basis for the superimposed multi-branch horizontal well + straight U-shaped well (well spacing <1000m) docking sintering production mode is mainly as follows: 1) Superimposed multi-branch horizontal wells are suitable for multi-layered or single-layer thick reservoirs with few thin interlayers; 2) For docking sintering production with straight U-shaped wells, ore layer experience shows that when the well spacing is <1000m and the thickness is <60m, it has a higher ore body recovery rate; 3) Regarding the requirement for the depth of the horizontal section, when it is greater than 1000m, the horizontal fractures of the docking fracturing are more developed, the connectivity is high, and the ore control volume is large, with an annual sintering production of 150,000 tons in a 500m horizontal section.

[0059] According to another preferred embodiment, in each alkali production layer below the reservoir layer, superimposed multi-branch horizontal wells are deployed and connected with flat U-shaped wells to form an injection-production well network. The production wells and injection wells of the flat U-shaped wells are connected on the same horizontal plane, and the superimposed multi-branch horizontal wells are set in the connection section between the production wells and the injection wells.

[0060] The design basis for the superimposed multi-branch horizontal well + flat-U-shaped well (well spacing > 1000m) docking fusion production mode is mainly as follows: 1) Superimposed multi-branch horizontal wells are suitable for multi-layered or single-layer thick reservoirs with few thin interlayers; 2) For flat-U-shaped well docking fusion production, it is suitable for reservoir development conditions with well spacing < 1000m and thickness < 60m; 3) Regarding the requirement for the depth of the horizontal section, when it is greater than 1000m, the horizontal fractures of the docking fracturing are more developed, the connectivity is high, and the ore control volume is large, with an annual fusion production of 150,000 tons in a 500m horizontal section.

[0061] According to another preferred embodiment, such as Figure 9As shown, in each alkali production layer below the reservoir layer, fishbone-shaped branch wells are deployed and connected with straight U-shaped wells to form an injection-production well network. Among them, the production wells of the straight U-shaped wells are vertical wells, the horizontal well sections of the injection wells are connected to the production wells, and the fishbone-shaped branch wells are set in the horizontal well sections of the injection wells.

[0062] The design basis for the fishbone-shaped branch well (intercalation layer > 5m) + straight U-shaped well (well spacing < 1000m) docking sintering mode is mainly as follows: 1) Fishbone-shaped branch wells are suitable for reservoirs with multiple and thick intercalations, with a single intercalation thickness > 5m; 2) For docking sintering with straight U-shaped wells, ore seam experience shows that when the well spacing is < 1000m and the thickness is < 60m, it has a higher ore body recovery rate; 3) Regarding the requirement for the depth of the horizontal section, when it is greater than 1000m, the horizontal fractures of the docking fracturing are more developed, the connectivity is higher, and the ore control volume is larger, with an annual sintering volume of 150,000 tons in a 500m horizontal section.

[0063] According to another preferred embodiment, such as Figure 10 As shown, in each alkali production layer below the reservoir layer, fishbone-shaped branch wells are deployed and connected with flat U-shaped wells to form an injection-production well network. Among them, the production wells and injection wells of the flat U-shaped wells are connected on the same horizontal plane, and the fishbone-shaped branch wells are set in the connection section between the production wells and the injection wells.

[0064] The design basis for the fishbone branch well + flat U-shaped well (well spacing > 1000m) docking sintering production mode is mainly as follows: 1) Fishbone branch wells are suitable for reservoirs with multiple and thick interlayers, and a single interlayer thickness > 5m; 2) Flat U-shaped well docking sintering production is suitable for reservoirs with a well spacing < 1000m and a thickness < 60m; 3) Regarding the requirement for the depth of the horizontal section, when it is greater than 1000m, the horizontal fractures of the docking fracturing are more developed, the connectivity is high, and the ore control volume is large, with an annual sintering production of 150,000 tons in a 500m horizontal section.

[0065] In this embodiment of the invention, compared with hydraulic fracturing, the horizontal drilling connection method has the following advantages: high connectivity rate, which can reach 100%; controllable docking layer and docking direction; large open area and high recovery rate; and less formation leakage and pollution.

[0066] Furthermore, the method for improving the recovery rate of alkali ore in the construction of natural alkali ore-type gas storage facilities provided in this embodiment of the invention further includes: constructing gas storage chambers in areas with a burial depth of 850m-2000m in the storage layer. Simultaneously, the single-chamber parameters of the gas storage chambers are designed based on the development characteristics of multi-layered alkali ore and the stability requirements of the gas storage facility.

[0067] According to a preferred embodiment, the single-cavity parameters of the gas storage chamber include: a single-cavity thickness greater than or equal to 90 μm, and a single-cavity diameter half the thickness of the single cavity. For example, a gas storage chamber with a single-cavity diameter of 45 μm and a single-cavity thickness of 90 μm has a cavity volume of 143,000 cubic meters. The well spacing in vertical wells is generally greater than three times the maximum cavity diameter.

[0068] The method further includes: designing the single-cavity storage capacity parameters of the gas storage chamber based on the development characteristics of the multi-layered alkali ore and the stability requirements of the gas storage facility. Specifically, the single-cavity storage capacity parameters include: a single-cavity ore body volume of 100,000-120,000 cubic meters, a single-cavity storage capacity of 27-35 million cubic meters, a single-cavity operating pressure of 12.2-29.6 MPa, and a working gas volume of 15-20 million cubic meters. The upper and lower limit operating pressures of the single-cavity chamber are calculated using pressure gradients of 0.017 MPa / m and 0.007 MPa / m, respectively.

[0069] This invention provides a method for improving the recovery rate of alkali deposits during the construction of natural alkali deposit-type gas storage facilities. The method involves converting the target strata in the main alkali deposit area into a gas storage facility and developing the lower alkali deposit layer through dissolution and extraction, thereby maximizing resource utilization and improving the investment efficiency of oil fields. At the same time, this method is scientific, reliable, and highly feasible, and is particularly suitable for integrated development blocks with complex geological features of multi-layered alkali dissolution and extraction and storage construction, with broad application prospects.

[0070] The following is a detailed description through a specific example:

[0071] Example 1

[0072] Table 1 compares the geological parameters of the study block and the Jintan gas storage facility. The Jintan gas storage facility is the first underground gas storage facility in my country built using underground saline strata. Its geological parameters are shown in Table 1. The A-type natural alkali deposit has abundant resources, a wide distribution area (reaching 26 square kilometers), and a moderate vertical burial depth (800-2800m). The alkali deposit in the central III section is thick (80-110m), providing the basic geological conditions for its conversion into a gas storage facility. It is expected to become the first intelligent alkali deposit gas storage facility in China.

[0073] Table 1

[0074]

[0075] Drawing on efficient salt mine development models both domestically and internationally, this embodiment adopts a combined approach of natural alkali development and gas storage construction. Taking into account reservoir development characteristics and the need for efficient storage, a three-dimensional development model is used for planning and deployment, with planar zoning, vertical layering, and personalized design of regional resource utilization to improve the overall resource recovery rate in multi-layered alkali mine storage construction.

[0076] The A-grade alkali ore caprock is developed throughout the area, with localized faulting, but this has little impact on reservoir construction. The top of the ore layer consists of a thick mudstone layer, exceeding 80m in some areas and approximately 12m in others, which is locally breached by faults; these faults must be avoided during cavity construction. Additionally, there are numerous interlayers, composed of mudstone and argillaceous dolomite, making cavity formation highly unlikely.

[0077] The technical principles adopted in this embodiment are as follows: gas storage facilities are to be constructed in the central strata of alkali ore with a thickness greater than 90m; considering the stability of the gas storage facility roof, the upper strata of the construction area will not be used for the time being; the lower strata of the gas storage facility will be connected by connecting wells for leaching and extraction; the construction area is preferably a region with large thickness and solid reserves (thickness greater than 40m), and the vertical well water leaching method will be used for development. Later, depending on the decline in production, the solidity of reserves at the edges, and market demand, the deployment at the edges will be considered.

[0078] Specifically, based on the development characteristics of multi-layered alkali deposits and the stability requirements of gas storage facilities, and comparing the screening criteria for salt cavern gas storage facilities, the middle layer with a longitudinal thickness greater than 90m, a burial depth of 850-2000m, and a distance of more than 200m from the fault in the main area of ​​the A natural alkali deposit is selected as the construction layer for the gas storage facility.

[0079] Considering the stability of the gas storage roof, the upper layers of the building will not be used for the time being.

[0080] For the lower strata of the reservoir layer, at least two alkali production layers are set up, and alkali production is jointly carried out by deploying docking wells to connect the injection and production well network. A well row spacing of 200m and a well spacing of 500-1500m are adopted, deploying 20 pairs of stacked multi-branch horizontal wells + fishbone-shaped branch wells. Specifically, the alkali production is achieved by docking stacked multi-branch horizontal wells + straight-horizontal U-shaped wells, or stacked multi-branch horizontal wells + horizontal-horizontal U-shaped wells, or fishbone-shaped branch wells + straight-horizontal U-shaped wells, or fishbone-shaped branch wells + horizontal-horizontal U-shaped wells. This achieves a well network configuration of "central gas storage well, with surrounding bottom embedded wells" in the study block, constructing a three-dimensional well network joint development model for alkali development and gas storage construction.

[0081] For the reservoir formation, a vertical well injection and production well network is deployed. This network is irregular, with 141 vertical wells deployed at a spacing of 120-130 meters. A combination of single vertical well convection dissolution and production and dual vertical well fracturing and interconnection dissolution and production is used for alkali production. At the same time, the individual parameters and reservoir capacity parameters of the gas storage chamber are designed in the study block.

[0082] Specifically, based on the development characteristics of multi-layered alkali deposits and the stability requirements of gas storage facilities, gas storage chambers are constructed in areas with concentrated resource reserves at depths of 850m-2000m in the middle layer. The thickness of the alkali deposit in the deployment wells is greater than 100m, with a reserved height of 10m at the top and bottom of the chambers. The designed thickness of a single chamber is 90m, and the diameter of the chamber in a single well is half the thickness of the chamber, approximately 45m, determined by reference to the stability evaluation results. The well spacing is usually greater than 3 times the maximum chamber diameter, approximately 135m. Simulation results also indicate that a single chamber with a diameter of 45m and a thickness of 90m is expected to have a chamber volume of 143,000 cubic meters.

[0083] Furthermore, based on the development characteristics of multi-layered alkali deposits and the stability requirements of gas storage facilities, individual chamber storage capacity parameters are designed, including: a single chamber ore body volume of 100,000-120,000 cubic meters for each well area, a single chamber storage capacity of 27-35 million cubic meters, a single chamber operating pressure of 12.2-29.6 MPa, and a working gas volume of 15-20 million cubic meters. The upper and lower operating pressure limits for each chamber are calculated using pressure gradients of 0.017 MPa / m and 0.007 MPa / m, respectively.

[0084] The method for improving the recovery rate of alkali ore in the construction of natural alkali ore gas storage provided in this invention differs from existing single-layer salt mine gas storage technology in that it is a method that considers multiple layers, large burial depth, large differences in ore layer thickness, different ore body types, and integrated design for combined storage construction to improve the recovery rate of alkali ore. It is more complex and technically more difficult. The main difference in expected effect is that it is a personalized combination design in both plane and vertical directions, which is a three-dimensional development model with higher alkali ore recovery rate and better comprehensive benefits.

[0085] In the above embodiments, the descriptions of each embodiment have their own emphasis. Parts not described in detail in a particular embodiment can be found in the relevant descriptions of other embodiments. Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for improving the recovery rate of alkali ore in the construction of natural alkali ore-type gas storage facilities, characterized in that, The method includes: Based on the development characteristics of multi-layered alkali deposits and the stability requirements of gas storage facilities, the target stratum in the middle of the main alkali deposit area is planned as the reservoir construction stratum. A vertical well injection-production well network is deployed in the reservoir layer, and a combination of single vertical well fracturing and alkali production mode and dual vertical well fracturing and alkali production mode is adopted. Connecting wells are deployed in the lower strata of the reservoir layer to link the injection and production well network. Alkali extraction is carried out using a paired horizontal well docking solution extraction mode or a vertical well docking solution extraction mode.

2. The method according to claim 1, characterized in that, The main alkali deposit distribution area is defined as the region with a burial depth of 400m-2850m and a dip angle of 10-22°.

3. The method according to claim 2, characterized in that, The strata with a longitudinal thickness greater than 90m, a burial depth of 500-2000m, and meeting the requirements for planar distribution in the central part of the alkali mine main area are planned as reservoir construction strata.

4. The method according to claim 3, characterized in that, The reservoir layer is more than 200m away from the fault location.

5. The method according to claim 1, characterized in that, The upper layers of the database will not be used for the time being.

6. The method according to claim 1, characterized in that, The vertical well injection and production well network deployed in the reservoir layer is an irregular well network, with at least 141 vertical well locations and a well spacing of 120-130m.

7. The method according to claim 1, characterized in that, At least two alkali-collecting layers are set in the lower layer of the reservoir.

8. The method according to claim 7, characterized in that, In each alkali-producing layer, superimposed multi-branch horizontal wells are deployed and connected with straight U-shaped wells to form an injection-production well network. Among them, the production wells of the straight U-shaped wells are vertical wells, the horizontal well sections of the injection wells are connected to the production wells, and the superimposed multi-branch horizontal wells are set in the horizontal well sections of the injection wells.

9. The method according to claim 7, characterized in that, In each alkali-producing layer, superimposed multi-branch horizontal wells are deployed and connected with flat U-shaped wells to form an injection-production well network. The production wells and injection wells of the flat U-shaped wells are connected on the same horizontal plane, and the superimposed multi-branch horizontal wells are set in the connection section between the production wells and the injection wells.

10. The method according to claim 7, characterized in that, Fishbone-shaped branch wells are deployed in each alkali-producing layer and connected to the straight U-shaped wells to form an injection-production well network. The production wells of the straight U-shaped wells are vertical wells, the horizontal well sections of the injection wells are connected to the production wells, and the fishbone-shaped branch wells are set in the horizontal well sections of the injection wells.

11. The method according to claim 7, characterized in that, Fishbone-shaped branch wells are deployed in each alkali-producing layer and connected to flat U-shaped wells to form an injection-production well network. The production wells and injection wells of the flat U-shaped wells are connected on the same horizontal plane, and the fishbone-shaped branch wells are set in the connecting section between the production wells and the injection wells.

12. The method according to claim 1, characterized in that, The method also includes: constructing a gas storage chamber in the area where the reservoir layer is buried at a depth of 850m-2000m.

13. The method according to claim 12, characterized in that, The method further includes: designing the single-cavity parameters of the gas storage chamber based on the development characteristics of the multi-layered alkali ore and the stability requirements of the gas storage tank.

14. The method according to claim 13, characterized in that, The single-cavity parameters of the gas storage chamber include: a single-cavity thickness greater than or equal to 90 μm, and a single-cavity diameter that is half the thickness of the single-cavity.

15. The method according to claim 12, characterized in that, The method further includes: designing the single-cavity storage capacity parameters of the gas storage chamber based on the development characteristics of the multi-layered alkali ore and the stability requirements of the gas storage tank.

16. The method according to claim 15, characterized in that, The storage parameters of the single chamber include: a single chamber ore body volume of 100,000-120,000 cubic meters, a single chamber storage capacity of 27-35 million cubic meters, a single chamber operating pressure of 12.2-29.6 MPa, and a working gas volume of 15-20 million cubic meters.

17. The method according to claim 16, characterized in that, The upper and lower operating pressure limits for a single chamber are calculated based on pressure gradients of 0.017 MPa / m and 0.007 MPa / m, respectively.

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