Three-dimensional U-shaped well structure and construction method thereof

Abstract

The embodiment of the invention provides a three-dimensional U-shaped well structure and a construction method thereof, and belongs to the field of underground resource development. Comprising an injection well and a production well, the injection well and the production well are arranged to extend to the target stratum depth from the earth surface, and the injection well and the production well are located on a first plane; the U-shaped connecting well is used for connecting the injection well and the production well and located on a second plane which is not coplanar with the first plane, and the second plane is parallel to the horizontal plane or forms a first set angle with the horizontal plane. The structure breaks through the limitation of traditional well type plane arrangement, can be flexibly arranged in a three-dimensional space according to geological conditions, and maximizes the resource contact area. The method is suitable for development and utilization of various underground resources such as petroleum, natural gas, geothermal energy and shale gas, the resource recovery efficiency can be remarkably improved, the investment payback period is shortened, and the overall economic benefit of a project is improved.

Description

Technical Field

[0001] The present application relates to the technical field of underground resource development, and in particular to a three-dimensional U-shaped well structure and a construction method thereof. Background Art

[0002] With the continuous increase in global energy demand, the efficient development of underground resources has become a key research topic in the energy field. Traditional underground resource extraction methods mainly include vertical well mining, inclined well mining, and horizontal well mining. In practical applications, these methods suffer from low extraction efficiency, limited resource coverage, and low recovery rates.

[0003] In recent years, U-shaped well technology has gained widespread application in underground resource extraction. Traditional U-shaped well technology utilizes a vertically and horizontally U-shaped well structure, extracting underground resources through fluid circulation between injection and production wells. However, traditional U-shaped well structures are primarily arranged within a two-dimensional plane, failing to fully utilize three-dimensional space. This results in limited contact area with the resource layer during extraction, low extraction efficiency, and limited coverage of underground resources.

[0004] For example, in oil and gas extraction, traditional U-shaped wells, confined to a single plane, cannot adapt to the three-dimensional distribution of complex geological structures. This results in ineffective coverage of some resource areas, limiting production and recovery rates. Similarly, in geothermal energy development, the planar layout of traditional U-shaped wells limits contact area with the heat reservoir, resulting in low heat extraction efficiency and difficulty in maximizing economic benefits.

[0005] Therefore, it is necessary to develop a new type of well structure to make full use of three-dimensional space to expand the contact area with the formation, so as to improve the efficiency of resource extraction, and it can be widely used in the exploitation of various underground resources such as oil, natural gas, and geothermal energy. Summary of the Invention

[0006] An embodiment of the present application provides a three-dimensional U-shaped well structure and a construction method thereof. The structure can be flexibly arranged in three-dimensional space according to geological conditions to maximize the resource contact area, and can be applied to the development and utilization of various underground resources such as oil, natural gas, geothermal energy, and shale gas.

[0007] In order to achieve the above-mentioned objectives, an embodiment of the present application provides a three-dimensional U-shaped well structure, including: an injection well and a production well, which are arranged to extend from the surface to the target formation depth, wherein the injection well and the production well are located in a first plane; and a U-shaped connecting well, used to connect the injection well and the production well, which is located in a second plane that is not coplanar with the first plane, wherein the second plane is parallel to the horizontal plane or at a first set angle.

[0008] Optionally, the U-shaped connecting well includes an injection extension line, a production extension line and a U-shaped connecting line, wherein the first plane is perpendicular to the horizontal plane, and the projection of the injection extension line on the horizontal plane is perpendicular to the first plane or at a second set angle.

[0009] Optionally, the injection extension line is parallel to the production extension line or is at a third set angle, the first set angle is 0°-45°, and the second set angle is 30°-90°.

[0010] Optionally, the U-shaped connecting well is connected to the injection well through a first connecting point and is connected to the production well through a second connecting point, and the line connecting the first connecting point and the second connecting point is parallel to the horizontal plane or at a fourth set angle, wherein the fourth set angle is 0°-45°.

[0011] Optionally, the U-shaped connecting well is one or more layers, the horizontal distance between the injection well and the production well is 500-2000m, the vertical depth of the injection well and the production well is 1000-5000m, and the length of the U-shaped connecting well is 1000-3000m. When the U-shaped connecting well is multi-layered, the three-dimensional U-shaped well structure also includes an intelligent fluid distribution system for controlling the fluid distribution ratio of each layer, wherein the second planes of each two adjacent layers are parallel to each other or at a fifth set angle.

[0012] Optionally, the U-shaped connecting well has 2-5 layers, wherein the second planes of each layer are parallel to each other, and the distance between two adjacent layers is 20-100m.

[0013] Optionally, the U-shaped connecting well consists of three layers, including an upper layer, a middle layer and a lower layer, wherein the injection volume and production capacity of the upper layer, the lower layer and the middle layer increase, and the injection pressure of the upper layer, the middle layer and the lower layer increases.

[0014] Optionally, the three-dimensional U-shaped well structure is applied to oil and gas extraction or geothermal extraction, wherein the wellbore structures of the production well, the injection well and the U-shaped connecting section include: casing and cement ring.

[0015] Optionally, when the three-dimensional U-shaped well structure is applied to geothermal extraction, the casing is a high-temperature casing, which can withstand high temperatures above 350°C. The wellbore structure of the production well also includes: an insulating layer, located between the casing and the cement ring, with a thermal conductivity coefficient of ≤0.85W / (m·K).

[0016] On the other hand, the present application provides a method for constructing a three-dimensional U-shaped well structure, the construction method comprising: determining the spatial layout of the three-dimensional U-shaped well according to the three-dimensional spatial characteristics of the resource distribution in the target area, including the number of layers, vertical offset angle, lateral offset angle and torsion angle of the U-shaped connecting well of the three-dimensional U-shaped well; drilling the injection well and the production well of the three-dimensional U-shaped well, wherein the injection well and the production well are located in a first plane; according to the spatial layout, drilling from the bottom of the injection well and the production well respectively toward the target area to form the U-shaped connecting well, wherein the U-shaped connecting well is located in a second plane that is not coplanar with the first plane, wherein the second plane is parallel to the horizontal plane or at a first set angle; and establishing a multi-layer three-dimensional fluid injection control system and a balanced production control system on the three-dimensional U-shaped well structure according to the resource type of the target area.

[0017] Through the above technical solution, this application provides a three-dimensional U-shaped well structure and its construction method, which can be applied to underground resource extraction. This structure breaks through the limitations of traditional well layout and can be flexibly arranged in three dimensions according to geological conditions, maximizing the resource contact area. This application is applicable to the development and utilization of various underground resources such as oil, natural gas, geothermal energy, and shale gas, and can significantly increase resource recovery rate, shorten investment payback period, and improve the overall economic benefits of the project.

[0018] Other features and advantages of the embodiments of the present application will be described in detail in the subsequent detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The accompanying drawings are used to provide a further understanding of the embodiments of the present application and constitute a part of the specification. Together with the following detailed description, they are used to explain the embodiments of the present application but do not constitute a limitation on the embodiments of the present application. In the accompanying drawings:

[0020] Figure 1 This is a schematic diagram of the well layout of the three-dimensional U-shaped well structure in the embodiment of the present application in a simple stratigraphic texture;

[0021] Figure 2 This is a schematic diagram of well layout when the formation texture has a certain inclination in the embodiment of the present application;

[0022] Figure 3 This is a schematic diagram of well layout according to stratum layers in an embodiment of the present application;

[0023] Figure 4a-4b This is a cross-sectional view of a three-dimensional U-shaped wellbore according to an embodiment of the present application;

[0024] Figures 5a-5d A schematic diagram comparing a U-shaped well of the embodiment of the present application with a U-shaped well of different structures in the prior art;

[0025] Figure 6 Schematic diagram comparing the outlet temperatures of a U-shaped well in the embodiment of the present application and a U-shaped well of different structures in the prior art;

[0026] Figure 7 Schematic diagram of economic analysis of the three-dimensional U-shaped well of the embodiment of the present application and the U-shaped wells of different structures in the prior art;

[0027] Figure 8 A schematic flow chart of a method for constructing a three-dimensional U-shaped well structure provided in an embodiment of the present application. DETAILED DESCRIPTION

[0028] The following describes the specific implementation of the embodiment of the present application in detail with reference to the accompanying drawings. It should be understood that the specific implementation described herein is only used to illustrate and explain the embodiment of the present application and is not intended to limit the embodiment of the present application.

[0029] It should be noted that the acquisition, transmission, storage, use, and processing of data in the technical solution of this application are in compliance with the relevant provisions of laws and regulations. In the embodiments of this application, certain software, components, models, and other existing solutions in the industry may be mentioned. These should be considered as exemplary. Their purpose is only to illustrate the feasibility of implementing the technical solution of this application, but it does not mean that the applicant has or will necessarily use such solutions.

[0030] Before introducing the various embodiments of this application, a brief description of the existing technical solutions is given. Traditional underground resource mining methods mainly include vertical well mining, inclined well mining, and horizontal well mining. These methods have problems such as low mining efficiency, limited resource coverage, and low recovery rate in actual application. The applicant, referring to industry statistics, found that traditional well technology has the following major problems:

[0031] 1) Limited spatial layout: Traditional well types are only arranged in a plane or in a single direction, resulting in limited resource contact area.

[0032] 2) Poor adaptability: In complex geological structures such as fault blocks, folds, and thin interbeds, traditional well types cannot effectively adapt to the spatial distribution characteristics of resources.

[0033] 3) Uneven fluid distribution: The single-plane layout causes the injected fluid to flow along the dominant channel, forming a "channeling" phenomenon, and a large amount of resource areas are bypassed.

[0034] 4) Large energy dissipation: Under the planar layout, the fluid flows over a long distance in the wellbore, resulting in large energy loss, which affects the mining efficiency.

[0035] 5) Low design flexibility: Unable to optimize design based on different resource types and geological characteristics, resulting in "one-size-fits-all" development.

[0036] Therefore, it is necessary to develop a new type of well structure that can make full use of three-dimensional space to expand the contact area with the formation, thereby improving the efficiency of resource extraction, and can be widely used in the exploitation of various underground resources such as oil, natural gas, and geothermal energy.

[0037] In this regard, the first aspect of the present application provides a three-dimensional U-shaped well structure, such as Figure 1 As shown, it may include: injection well A, production well B and U-shaped connection well C.

[0038] The injection well A and the production well B are set to extend from the surface to the target formation depth, wherein the injection well A and the production well B are located in the first plane. Figure 1 In the three-dimensional coordinate system, XY is the two horizontal axes and Z is the vertical axis, then the first plane can be the XZ plane. In one embodiment, the three-dimensional U-shaped well structure provided by the present application includes at least one injection well A and at least one production well B. Figure 1 As shown, the injection well A and the production well B can be drilled vertically downward to the target depth to form a vertical section 1 (at Figure 2 The vertical section 4 is a vertical section, and drilling can also be performed at a certain inclination angle. In this embodiment, the vertical depth of injection well A and production well B is 1000-5000m, preferably 3000m; the horizontal distance between the two wells is 500-2000m, preferably 1000m.

[0039] The U-shaped connecting well C is used to connect the injection well A and the production well B, and can be located in a second plane that is not coplanar with the first plane, thereby forming a three-dimensional U-shaped structure in three-dimensional space. For example, the second plane can be a horizontal plane (XY plane) and is perpendicular to the first plane (XZ plane). For example, the U-shaped connecting well C can be at least one set of horizontal connecting well sections, such as Figure 1 As shown, it can include two horizontal sections 2 and a U-shaped connecting section 3, thereby forming a U-shaped connecting well on the horizontal plane or the approximate horizontal plane at a specific depth of the reservoir. In this embodiment, the length of the U-shaped connecting well is 1000-3000m, preferably 2000m.

[0040] In this application, U-shaped connecting wells can present a multi-angle, multi-directional, and multi-level three-dimensional layout in three-dimensional space according to the geological structure and resource distribution characteristics. For example, this three-dimensional layout can include vertical offset, horizontal offset, and torsional offset to form various types of three-dimensional U-shaped structures. For example, according to the differences in stratum characteristics, this application provides Figure 1-3 The well layout scheme shown in the figure: For formations with simpler texture and weaker formation heterogeneity, the well layout scheme shown in the figure can be Figure 1 The well layout scheme shown in the figure can be used for strata with a certain inclination angle. Figure 2The well layout scheme shown in the figure can be used for formations with distinct stratification characteristics. Figure 3 The multi-level well layout shown.

[0041] The present application will be further described in detail below with reference to the accompanying drawings and embodiments. In an embodiment where the three-dimensional layout includes a vertical offset, the second plane may be parallel to the horizontal plane ( Figure 1 ), or at a first set angle to the horizontal plane ( Figure 2 ), thus forming a vertical offset. Figure 2 In the case of vertical offset shown, the U-shaped connecting shaft may include two vertical offset sections 5 and a U-shaped connecting section 6. In one embodiment, the first set angle of the vertical offset is 0°-45°, such as 10°-45°, preferably 30°.

[0042] In an embodiment where the three-dimensional layout includes a horizontal offset, the U-shaped connecting well may include an injection extension line, a production extension line, and a U-shaped connecting line. In the case where the first plane is perpendicular to the horizontal plane, the projection of the injection extension line on the horizontal plane may be perpendicular to the first plane ( Figure 1 or Figure 2 ), or at a second set angle (not shown) with the first plane, thereby forming a horizontal offset. It is understood that the horizontal offset refers to the Figure 1 In the three-dimensional coordinate system of , the U-shaped connecting well is inclined toward the X-axis or the Y-axis on the horizontal plane XY. In one embodiment, the second set angle can be 30°-90°, for example, 30°-75°, preferably 50°. In addition, if the projection of the injection extension line on the horizontal plane is perpendicular to the first plane as a reference (that is, the horizontal offset angle is 0), then the sum of the corresponding horizontal offset angle and the second set angle is 90°, that is, the horizontal offset angle is 0°-60°, for example, 15°-60°, preferably 40°.

[0043] In the horizontally offset embodiment, the injection extension line can be parallel to the production extension line ( Figure 1 or Figure 2 ), or the two may be non-parallel and present a third set angle (not shown). In the case where the two are non-parallel, the production extension line may also be set in the same manner according to the above-mentioned horizontal offset angle range of the injection extension line, so that the two may be offset in opposite directions or offset in the same direction at different angles. The reverse offset may also include diffuse offset and convergent offset, which is not limited in this application.

[0044] In an embodiment where the three-dimensional layout includes a torsional offset, the U-shaped connecting well is connected to the injection well via a first connection point and to the production well via a second connection point, and the line connecting the first connection point and the second connection point is parallel to the horizontal plane ( Figure 1 or Figure 2), or a fourth setting angle with the horizontal plane, thereby forming a torsional offset. In one embodiment, the fourth setting angle is 0°-45°, such as 0°-30°, and preferably 10°.

[0045] In one embodiment, the U-shaped connecting well is one or more layers. Wherein, in the case of the U-shaped connecting well being multiple layers, the second planes of each two adjacent layers are parallel to each other ( Figure 3 ) or at a fifth setting angle. In one embodiment, the fifth setting angle is 0°-45°, such as 10°-30°, preferably 10°.

[0046] In addition, when the U-shaped well is multi-layered, the three-dimensional U-shaped well structure also includes an intelligent fluid distribution system that can be used to control the fluid distribution ratio of different horizontal well sections. The intelligent fluid distribution system includes a main control unit, a layered injection control valve, a layered production control valve, and a real-time monitoring system; the layered injection control valve and the layered production control valve are respectively installed at the inlet and outlet of each layer of the horizontal well section; the real-time monitoring system includes a distributed fiber optic temperature measurement system, a pressure sensor, a flow meter, a water content analyzer, and a gas-oil ratio monitoring device, etc. This application does not limit this.

[0047] Among them, in the case of a multi-level well layout, the second planes of each layer can be parallel to each other, and the distance between two adjacent layers can be 20-100m, preferably 50m. In one embodiment, the U-shaped connecting well can be 2-5 layers, preferably 3 layers, which can include upper, middle and lower layers. That is, in this case, the multi-level horizontal connecting well sections can be divided into upper, middle and lower horizontal wells in turn to meet the mining needs of different strata. In one embodiment, the three-layer horizontal connecting well sections are located at different depths, and the distance between two adjacent layers can be equal, for example, both are 50m. Its specific structure refers to Figure 3 As shown, the relevant parameters can be as follows:

[0048] 1) Upper horizontal well section C1: located at a depth of 2950 m, with a vertical offset angle range of 0°-15° (0° in the figure), a horizontal offset angle range of 0°-25° (0° in the figure), and a length of 2000 m;

[0049] 2) Middle horizontal well section C2: located at a depth of 3000 m, with a vertical offset angle range of 0°-30° (0° in the figure), a horizontal offset angle range of 0°-40° (0° in the figure), and a length of 2200 m;

[0050] 3) Lower horizontal well section C3: Located at a depth of 3050 m, with a vertical offset angle range of 0°-45° (0° in the figure), a horizontal offset angle range of 0°-55° (0° in the figure), and a length of 2400 m.

[0051] In one embodiment, a three-dimensional U-shaped well structure can be used to extract underground resources such as oil, natural gas, geothermal energy, coalbed methane, or shale gas. In the case of a three-layer U-shaped well, the injection rate and production capacity of the upper, lower, and middle layers increase, while the injection pressure of the upper, middle, and lower layers increases. The following provides extraction parameter settings for different resources.

[0052] In the embodiment where the underground resource is oil, the fluid injection strategy includes: injecting 30-50m3 of fluid in the upper well section. 3 / h, injection pressure 12-18MPa, injection temperature 50-70℃; injection volume in the middle well section 50-80m 3 / h, injection pressure 15-22MPa, injection temperature 50-70℃; injection volume in the lower well section 40-70m 3 / h, injection pressure 18-25MPa, injection temperature 50-70℃.

[0053] In the embodiment where the underground resource is natural gas, the fluid injection strategy includes: injecting 25-40m3 of fluid in the upper well section. 3 / h, injection pressure 10-15MPa, injection temperature 40-50℃; injection volume in the middle well section 40-60m 3 / h, injection pressure 13-18MPa, injection temperature 40-50℃; injection volume in the lower well section 30-50m 3 / h, injection pressure 15-20MPa, injection temperature 40-50℃.

[0054] In the embodiment where the underground resource is geothermal energy, the fluid injection strategy includes: injecting 35-55m3 of fluid in the upper well section. 3 / h, injection pressure 12-18MPa, injection temperature 10-20℃; injection volume in the middle well section 55-75m 3 / h, injection pressure 15-22MPa, injection temperature 10-20℃; injection volume in the lower well section 45-65m 3 / h, injection pressure 18-25MPa, injection temperature 10-20℃.

[0055] In the embodiment where the underground resource is coalbed methane or shale gas, the fluid injection strategy includes: injecting 20-35m3 of fluid in the upper well section. 3 / h, injection pressure 8-13MPa, injection temperature 35-45℃; injection volume in the middle well section 35-55m 3 / h, injection pressure 10-16MPa, injection temperature 35-45℃; injection volume in the lower well section 25-45m 3 / h, injection pressure 12-18MPa, injection temperature 35-45℃.

[0056] In addition, the wellbore structure of the production well, injection well and U-shaped connection section may include: casing and cement ring, etc. Figure 4a In one embodiment, the inner diameter of the casing is 0.1-0.3 m, preferably 0.178 m; the thickness of the casing is 0.05-0.15 m, preferably 0.1 m; and the thickness of the cement sheath is 0.05-0.15 m, preferably 0.1 m.

[0057] When the three-dimensional U-shaped well structure is used for geothermal energy extraction, the casing can be a high-temperature resistant special steel casing with a high temperature resistance of more than 350°C. In addition, the wellbore structure of the production well can also include: an insulation layer (insulation layer) located between the casing and the cement sheath, such as Figure 4b As shown, its thickness is 0.05-0.15m, preferably 0.1m, and its thermal conductivity is ≤0.85W / (m·K). That is to say, when the present application is applied to geothermal exploitation, in order to achieve the best insulation effect, the wellbore cross-sectional structure of the production well is designed to be a multi-layer composite structure, and its wellbore can include casing, insulation layer and cement ring from the inside to the outside. Among them, the inner diameter of the casing is 0.19m and the thickness is 0.1m; the insulation layer thickness is 0.1m; and the cement ring thickness is 0.1m. In contrast, injection wells and horizontal wells are intended to achieve sufficient heat exchange with the formation, so only a single-layer casing structure is set without an insulation layer, but its inner diameter needs to be consistent with the inner diameter of the production well casing, for example, both are 0.19m.

[0058] It is understood that for oil and natural gas extraction, or coalbed methane and shale gas extraction, when applying this application, the production well structure does not need to be equipped with additional insulation materials. In addition, the choice of casing materials for injection wells and production wells also varies. For example, for oil and natural gas extraction, high-strength alloy steel casing with a compressive strength of ≥110 ksi can be used, and this application does not limit this.

[0059] In summary, the key technical point of the present application is to provide a three-dimensional U-shaped well structure. The structure includes at least one injection well, at least one production well and a U-shaped connecting well, such as at least one group of horizontally connected well sections. The horizontally connected well sections present a multi-angle, multi-directional, and multi-level three-dimensional layout in three-dimensional space, thereby forming a three-dimensional U-shaped structure. This structure breaks through the limitations of the traditional well-type planar layout and can be flexibly arranged in three-dimensional space according to geological conditions to maximize the resource contact area. For example, for oil extraction, the multi-level well structure of the present application is particularly suitable for oil reservoirs with multi-oil layer distribution characteristics. It can contact multiple oil-producing layers at the same time, realize single-well multi-layer oil production, and significantly improve the single-well production and the overall recovery rate of the oil field. Compared with the prior art, the present application has the following beneficial effects:

[0060] 1) Three-dimensional layout: This breaks through the limitations of traditional well layout and can be flexibly arranged in three dimensions based on geological conditions, maximizing resource contact area. Typical cases show that resource coverage can be increased to 90-95%;

[0061] 2) Multi-level development: Through a combination of vertical and horizontal offset designs, resources at different depths and in different directions are developed simultaneously, significantly improving single-well recovery rates.

[0062] 3) Balanced fluid distribution: The three-dimensional layout uses layered injection devices to set different injection parameters based on the permeability differences between each layer, cutting off the dominant channel for crossflow in the high-permeability layer. At the same time, the different pressure gradients in the upper, middle, and lower well sections are used to form a three-dimensional balanced pressure field. The pressure difference suppresses the unidirectional flow of fluid. Intelligent valves are used to control flow pressure in real time. The pressure of adjacent layers is dynamically compensated for crossflow signs. Combined with the three-dimensional production system's layered production control, a two-way balanced drive of injection and production is achieved, transforming the traditional planar crossflow pattern into a three-dimensional uniform displacement, thereby effectively reducing crossflow.

[0063] 4) Efficient energy utilization: The optimized three-dimensional spatial layout shortens the fluid flow path, reduces energy loss, and improves energy utilization efficiency;

[0064] 5) Wide range of applications: This technology is not only applicable to oil and natural gas extraction, but can also be applied to the development of geothermal energy, shale gas, coalbed methane and other resources;

[0065] 6) Significant economic benefits: Compared with traditional technologies, three-dimensional U-shaped wells significantly improve resource recovery rates, shorten investment payback periods, and improve economic benefits.

[0066] In order to better illustrate the present application, two embodiments are provided below to further illustrate the content and technical solutions of the present application, and to assist in illustrating the feasibility and beneficial effects of the present application. It is worth noting that the specific implementation methods herein are used to assist in illustrating the present application, and the present application is not limited to these implementation methods.

[0067] Example 1: Application of different three-dimensional U-shaped wells in geothermal mining

[0068] For geothermal mining, when using this application, considering the cost of drilling multi-level horizontal wells, the well structure can be simplified during geothermal mining, such as using Figure 1 In order to compare the advantages of this application, in addition to the well structure studied in this paper ( Figure 5b ), and three other well structures such as single U-shaped well ( Figure 5a ), multiple injection U-shaped wells ( Figure 5c , for example, including multiple injection wells A1-A3) and multiple horizontal U-shaped wells ( Figure 5d ) were compared.

[0069] Table 1: Technical parameters under geothermal conditions

[0070] Main parameters Adopt value Vertical Depth 3km Horizontal straight line segment length 1.5km Vertical well spacing 1km Casing inner diameter 0.178m Casing thickness 0.05m Insulation layer thickness 0.1m Cement sheath thickness 0.1m Injection temperature 15℃ surface temperature 15℃ Injection speed 1.2m / s Rock density 2500kg / m3 Constant-pressure heat capacity of rock 900J / (kg·K) Thermal conductivity of rock 2.3w / (m·k) geothermal gradient 0.025℃ / m Thermal conductivity of casing 80w / (m·k) Equivalent thermal conductivity of insulation layer 0.25w / (m·k) Runtime 20 years

[0071] In order to reasonably compare the heat transfer effects and power generation economic benefits of different well structures, when simulating different well structures, except for the parameters related to the horizontal section, other relevant parameters are consistent with Table 1.

[0072] Specifically, the relevant comparison indicators include the outlet temperature and the LCOE (levelized cost of electricity) value after 20 years of operation. LCOE refers to the average cost obtained by allocating all costs of an energy project over its entire life cycle to each unit of electricity generation according to a certain discount rate. This indicator is an important parameter for evaluating the economic feasibility of electricity production methods. By comprehensively considering the costs and benefits of the entire life cycle of the project, it can comprehensively and objectively reflect the long-term cost levels of different energy technologies. Therefore, this application uses this parameter to compare the economic feasibility of power generation of different geothermal well structures.

[0073] like Figure 6 As shown in the figure, for the entire geothermal heat exchange system, the outlet temperatures of the four well structures show significant differences over time. The double U-shaped well structure has the highest initial outlet temperature (about 87°C), which remains high throughout the 20-year operation period, eventually stabilizing at about 42°C. The multi-horizontal section well is second, with an initial temperature of about 76°C and eventually stabilizing at about 37°C. The multi-injection well has an initial temperature of about 69°C, but decays rapidly, dropping to about 30°C after 5 years. The single U-shaped well performs the worst, with an initial temperature of only about 49°C, which quickly decays to about 27°C and remains stable at a low level. This is mainly due to the double U-shaped well structure having a longer horizontal heat exchange section, which enables more efficient heat energy extraction.

[0074] in addition, Figure 7 The LCOE comparison of different well configurations is intuitively demonstrated. The results show that the double U-shaped well has the best economic performance, with an LCOE of approximately $0.435 per kWh. The multi-injection U-shaped well and multi-horizontal U-shaped well rank second, with LCOEs of approximately $0.55 per kWh and $0.92 per kWh, respectively. The single U-shaped well, however, has the worst economic performance, with an LCOE of approximately $5.4 per kWh, significantly higher than the other three configurations. This result is highly consistent with the temperature output performance, fully demonstrating the significant advantages of the double U-shaped well configuration in geothermal energy development.

[0075] It can be seen that the research on the double U-shaped well heat exchange power generation process in this application has important practical value and realistic significance for improving geothermal energy extraction efficiency and optimizing the economic benefits of power generation.

[0076] Example 2: Application of three-dimensional U-shaped wells in oil field development

[0077] The three-dimensional U-shaped well structure proposed in this application is an innovative technical solution for underground resource development. Through its unique multi-angle, multi-directional, and multi-level three-dimensional spatial layout, it has achieved comprehensive improvements in technical indicators and economic benefits. To explore the potential of the three-dimensional U-shaped well structure in oilfield development, in the absence of actual application data, the applicant constructed a mechanism model using reservoir simulation software. Using the three-, four-, and five-layer well layouts (100m spacing) adopted in this application as reference, a comparative study of the three-dimensional U-shaped well and traditional well layout patterns was conducted. The specific simulation results are shown in Table 2.

[0078] Table 2: Statistics of oilfield development and application with different well structures

[0079]

[0080] From the analysis of Table 2, we can find that in the three-dimensional development technology system of oil and gas reservoirs, the three-dimensional U-shaped well multi-layer layout scheme proposed in this application (3, 4, or 5 horizontal wells can be deployed according to the reservoir depth gradient) has demonstrated breakthrough efficiency in the 3-layer implementation stage: by cutting the reservoir in three dimensions, the resource contact area has been increased from 15,000m2 of the traditional U-shaped well to 15,000m2. 2 Jump to 35,000m 2 (Increased by 133%), the daily output of a single oil well increased from 60-80 tons to 120-150 tons (doubled), the natural gas recovery rate increased from 60-68% to 75-85%, and the single well investment payback period was shortened from 3-5 years to 2-3 years, taking the lead in achieving a coupled balance between technological breakthroughs and economic feasibility.

[0081] When the number of well layers is expanded to 4 or 5, the technical effect shows a significant attenuation feature: for example, from the perspective of reservoir utilization boundary, the 3-layer scheme has achieved efficient coverage of the main oil-bearing layer (resource coverage rate of 95%). The resource coverage rate of the subsequent newly added layers (4 and 5 layers) can only increase slightly by 1.5% from 95% to 96.5% (4 layers) and then by 0.5% to 97% (5 layers) due to the limitation of the vertical heterogeneity of the reservoir (such as decreasing permeability and decreasing oil saturation). From the perspective of production capacity contribution, the oil recovery rate increased from 48-55% in the 3-layer to 49-60% in the 4-layer (an increase of 15.5%) and 49-57% in the 5-layer (an increase of 15.2%). The gain amplitude continues to narrow. The root cause is that the stress interference between multiple wellbores causes the permeability damage in the near-well zone and the seepage efficiency of the newly added layers decreases. In terms of daily natural gas production per well, the 3-layer scheme achieves 150,000-200,000 m 3 After the breakthrough of / d, the 4th and 5th floors can only be upgraded to 220,000-250,000 m 3 / d, 250,000-270,000 m 3 / d, the output increment per unit layer is from 70,000 to 100,000 m 3 / d drops sharply to 30,000-50,000 m 3 / d, reflecting that the remaining available seepage channels in the reservoir are gradually saturated.

[0082] In summary, the three-layer, three-dimensional U-shaped well plan precisely matches the vertical sweet spot distribution of the reservoir, achieving efficient reservoir development (95% resource coverage and more than doubling production) while effectively avoiding the "technical marginal decline" and "economic investment imbalance" issues faced by four- and five-layer wells, thus establishing an optimal implementation model that combines technological breakthroughs with commercial sustainability. Therefore, in the actual application of three-dimensional oil and gas reservoir development, the three-layer well layout is preferred, with four- and five-layer wells serving as supplementary options in scenarios with extremely favorable reservoir endowments, thereby balancing the dynamic relationship between technological innovation and development economics.

[0083] Method Example

[0084] The second aspect of the present application provides a method 200 for constructing a three-dimensional U-shaped well structure, which can be applied in underground resource mining, such as Figure 8 As shown, the construction method 200 may include:

[0085] Step S210: Determine the spatial layout of the three-dimensional U-shaped well based on the three-dimensional spatial characteristics of the resource distribution in the target area. The spatial layout may include the number of layers of U-shaped connecting wells, vertical offset angles, lateral offset angles, and torsion angles of the three-dimensional U-shaped well.

[0086] Step S220, drilling an injection well and a production well of a three-dimensional U-shaped well, wherein the injection well and the production well are located in a first plane;

[0087] Step S230: Drilling from the bottom of the injection well and the production well toward the target area according to the spatial layout to form a U-shaped connecting well, wherein the U-shaped connecting well is located in a second plane that is not coplanar with the first plane, wherein the second plane is parallel to the horizontal plane or at a first set angle; and

[0088] Step S240 , establishing a multi-layer three-dimensional fluid injection control system and a balanced production control system on the three-dimensional U-shaped well structure according to the resource type of the target area.

[0089] In addition, for the application method of the three-dimensional U-shaped well structure constructed in this application, its complete application process can also include: geological exploration and well location optimization, three-dimensional U-shaped well construction, multi-layer three-dimensional fluid injection system, three-dimensional balanced production system and closed-loop circulation optimization control, as described below.

[0090] 1) Geological exploration and well location optimization:

[0091] Advanced geological exploration technology can be used to accurately model the target area; analyze the three-dimensional spatial characteristics of resource distribution, including fault distribution, stratigraphic changes, permeability distribution, etc.; apply computational fluid dynamics simulation to optimize the spatial layout of three-dimensional U-shaped wells; determine the optimal vertical offset angle, lateral offset angle and torsion angle; and establish a multi-level well network design to achieve maximum resource coverage.

[0092] 2) Construction of three-dimensional U-shaped well:

[0093] Advanced drilling technology can be used to complete the vertical drilling of injection wells and production wells; according to the design parameters, horizontal connecting well sections can be drilled from the injection wells and production wells to the target area respectively; necessary wellbore docking technology can be implemented to ensure the integrity of the horizontal connecting well sections; according to the characteristics of different formations, corresponding completion processes can be adopted; and intelligent downhole monitoring equipment can be installed to realize real-time monitoring of the wellbore status.

[0094] 3) Multi-layer three-dimensional fluid injection system:

[0095] According to different resource types, corresponding fluid injection strategies can be designed; layered injection devices can be installed to achieve differentiated injection at different levels; for example, the injection volume of the upper horizontal well section: 30-50m 3 / h, injection pressure: 12-18MPa; injection volume in the middle horizontal well section: 50-80m 3 / h, injection pressure: 15-22MPa; injection volume in the lower horizontal well section: 40-70m 3 / h, injection pressure: 18-25MPa; dynamic adjustment of flow and pressure is achieved through intelligent control valves.

[0096] 4) Stereoscopic balanced extraction system:

[0097] Intelligent flow control devices can be installed in each horizontal section of the production well; for example, the production capacity of the upper horizontal well section is: 40-60m 3 / h; production capacity of the middle horizontal well section: 60-90m 3 / h; Output capacity of lower horizontal well section: 50-80m 3 / h; achieve balanced extraction in each layer to avoid local over-exploitation; equipped with an intelligent production and liquid control system to automatically adjust the output of each layer based on real-time monitoring data.

[0098] 5) Closed-loop optimization control:

[0099] A complete surface-downhole closed-loop control system can be established; multi-parameter monitoring data including temperature, pressure, flow rate, water content, etc. can be collected; artificial intelligence algorithms can be used to analyze production dynamics in real time and optimize injection and production parameters; regular production tests can be conducted to evaluate the production capacity contribution of each layer; and based on the test results, the operation strategy of the three-dimensional U-shaped well can be dynamically adjusted to achieve the optimal development effect.

[0100] In summary, this application provides a three-dimensional U-shaped well structure and its application method in underground resource extraction. The structure includes at least one injection well, at least one production well, and at least one set of U-shaped connecting wells. The U-shaped connecting wells can present a three-dimensional layout with multiple angles, directions, and levels in three-dimensional space, thereby forming a three-dimensional U-shaped structure.

[0101] This three-dimensional U-shaped well structure in this application breaks through the limitations of traditional planar well layouts and can be flexibly arranged in three dimensions according to geological conditions, maximizing the resource contact area. For example, in oil production, this multi-layered well structure is particularly suitable for reservoirs with multiple oil layers. It can simultaneously contact multiple oil-producing layers, achieving multi-layer oil production from a single well, significantly improving single-well production and the overall oil field recovery rate.

[0102] In addition, the complete application process of this application also includes geological exploration and well location optimization, three-dimensional U-shaped well construction, multi-layer three-dimensional fluid injection system, three-dimensional balanced production system and closed-loop circulation optimization control. It is worth noting that, given the limitations of current drilling technology, the cost of drilling U-shaped connecting wells in the reservoir is relatively high, but this does not affect the beneficial effects of the innovative three-dimensional U-shaped well structure of this application. If there are some breakthroughs in subsequent drilling technology, this innovative structure of this application can be promoted and applied on a large scale, and then effectively play a significant role in the development of underground resources.

[0103] It should also be noted that the terms "comprises," "includes," or any other variations thereof are intended to encompass non-exclusive inclusion, such that a process, method, commodity, or apparatus that includes a series of elements includes not only those elements but also other elements not explicitly listed, or includes elements inherent to such process, method, commodity, or apparatus. In the absence of further limitations, an element defined by the phrase "comprises a ..." does not exclude the presence of other identical elements in the process, method, commodity, or apparatus that includes the element.

[0104] The above are merely embodiments of the present application and are not intended to limit the present application. For those skilled in the art, the present application may have various changes and variations. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present application should all be included within the scope of the claims of the present application.

Claims

1. A three-dimensional U-shaped well structure, characterized in that: include: an injection well and a production well, arranged to extend from the surface to a target formation depth, wherein the injection well and the production well are located in a first plane; and A U-shaped connecting well is used to connect the injection well and the production well, and is located in a second plane that is not coplanar with the first plane, wherein the second plane is parallel to the horizontal plane or at a first set angle.

2. The three-dimensional U-shaped well structure according to claim 1, characterized in that: The U-shaped connecting well includes an injection extension line, a production extension line and a U-shaped connecting line. The first plane is perpendicular to the horizontal plane, and the projection of the injection extension line on the horizontal plane is perpendicular to the first plane or is at a second set angle.

3. The three-dimensional U-shaped well structure according to claim 2, characterized in that: The injection extension line is parallel to the production extension line or is at a third set angle, The first setting angle is 0°-45°, and the second setting angle is 30°-90°.

4. The three-dimensional U-shaped well structure according to claim 1, characterized in that: The U-shaped connecting well is connected to the injection well through a first connecting point and is connected to the production well through a second connecting point. A line connecting the first connection point and the second connection point is parallel to the horizontal plane or is at a fourth set angle, wherein the fourth set angle is 0°-45°.

5. The three-dimensional U-shaped well structure according to claim 1, characterized in that: The U-shaped connecting well is one or more layers, the horizontal distance between the injection well and the production well is 500-2000m, the vertical depth between the injection well and the production well is 1000-5000m, and the length of the U-shaped connecting well is 1000-3000m. When the U-shaped connecting well is multi-layered, the three-dimensional U-shaped well structure also includes an intelligent fluid distribution system for controlling the fluid distribution ratio of each layer, wherein the second planes of each two adjacent layers are parallel to each other or at a fifth set angle.

6. The three-dimensional U-shaped well structure according to claim 5, characterized in that: The U-shaped connecting well has 2-5 layers. The second planes of each layer are parallel to each other, and the distance between two adjacent layers is 20-100m.

7. The three-dimensional U-shaped well structure according to claim 6, characterized in that: The U-shaped connecting well has three layers, including the upper layer, the middle layer and the lower layer. The injection volume and production capacity of the upper layer, the lower layer and the middle layer increase gradually, and the injection pressure of the upper layer, the middle layer and the lower layer increases gradually.

8. The three-dimensional U-shaped well structure according to claim 1, characterized in that: The three-dimensional U-shaped well structure is used in oil and gas mining or geothermal mining. Wherein, the wellbore structures of the production well, the injection well and the U-shaped connecting section include: casing and cement ring.

9. The three-dimensional U-shaped well structure according to claim 8, characterized in that: When the three-dimensional U-shaped well structure is applied to geothermal mining, the casing is a high-temperature casing with a high temperature resistance of 350°C or above. The wellbore structure of the production well further includes: an insulating layer located between the casing and the cement ring, with a thermal conductivity coefficient of ≤0.85W / (m·K).

10. A method for constructing a three-dimensional U-shaped well structure, characterized in that: The construction method comprises: Determining the spatial layout of the three-dimensional U-shaped well according to the three-dimensional spatial characteristics of resource distribution in the target area, including the number of layers, vertical offset angle, lateral offset angle, and torsion angle of the U-shaped connecting wells of the three-dimensional U-shaped well; Drilling an injection well and a production well of the three-dimensional U-shaped well, wherein the injection well and the production well are located in a first plane; According to the spatial layout, drilling from the bottom of the injection well and the production well toward the target area respectively to form the U-shaped connecting well, wherein the U-shaped connecting well is located in a second plane that is not coplanar with the first plane, wherein the second plane is parallel to the horizontal plane or at a first set angle; and According to the resource type of the target area, a multi-layer three-dimensional fluid injection control system and a balanced production control system are established on the three-dimensional U-shaped well structure.

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