One-driving-two U-shaped well group for deep geothermal development, well completion method and collection method

Abstract

The deep geothermal development one-driving-two U-shaped well forming method comprises the steps that a vertical well is arranged at a target stratum, and the vertical well comprises a vertical well section and a butt joint cavity formed in the bottom of the vertical well section; a first horizontal well is arranged, and the tail end of the horizontal section of the first horizontal well is fixed into the butt joint cavity through the long-distance needle threading magnetic steering technology; and a second horizontal well is arranged, the tail end of the horizontal section of the second horizontal well is fixed into the butt joint cavity through the long-distance needle penetrating magnetic steering technology, the included angle between the horizontal section of the first horizontal well and the horizontal section of the second horizontal well ranges from 90 degrees to 180 degrees, and the second horizontal well and the first horizontal well are symmetrically arranged relative to the vertical well to form a one-driving-two U-shaped well set. The invention further provides a one-driving-two U-shaped well group and a deep geothermal collection method. According to the method, one straight well is in butt joint with two horizontal wells to form a one-to-two U-shaped well group, the geothermal development investment of the U-shaped well is reduced, the land occupation is reduced, and more efficient development of deep geothermal energy is realized.

Description

Technical Field

[0001] The present invention relates to the technical field of geothermal development, and in particular to a one-to-two U-shaped well group, a well completion method and a collection method for deep geothermal development. Background Art

[0002] China's geothermal resources are widely distributed and are a renewable energy source with the advantages of abundant reserves, cleanliness, great development potential and direct utilization. The advantage of underground thermal energy utilization is that even in areas without underground hot water, as long as the geothermal gradient is abnormally positive, there is high-temperature rock mass within a certain depth underground. By using heat exchange media such as water injected underground, the heat energy can be brought to the surface for use, such as heating, etc. It is a clean, environmentally friendly and renewable energy source.

[0003] Deep geothermal refers to geothermal resources buried more than 2500m deep. In the existing technology, a U-shaped well group is usually formed by combining a vertical well and a horizontal well. The heat exchange principle of the U-shaped butt-joint well is to drill a U-shaped butt-joint well into the rock formation, use casing cementing technology to seal the geothermal well, and establish an in-well heat exchange system. Low-temperature water is injected into the water inlet well. During the flow along the vertical well section and the horizontal well section, the low-temperature water is heated by the surrounding rock and then flows upward from the water outlet well out of the heat exchanger. After the hot water returns to the ground, its heat is lifted by the heat pump unit and used for building heating. The cooled circulating water enters the underground heat exchange cycle again, bringing the heat in the surrounding rock to the surface. The cycle repeats over and over again without any hydraulic connection with the groundwater and without damaging the groundwater resources. However, this type of well group has problems such as limited heat exchange effect, high well group drilling cost, and high investment.

[0004] Therefore, there is a need in the prior art for the design of a one-to-two U-shaped well composition method for deep geothermal development. Summary of the invention

[0005] In view of this, the purpose of the embodiments of the present invention is to propose a one-to-two U-shaped well group, a well completion method and a collection method for deep geothermal development. By designing the well completion method, a vertical well is connected to two horizontal wells to form a "one-to-two U-shaped well group", thereby reducing the investment in U-shaped well geothermal development, reducing the ground area occupied, and achieving more efficient development of deep geothermal energy.

[0006] Based on the above purpose, an embodiment of the present invention provides a method for forming a one-to-two U-shaped well for deep geothermal development, the method comprising the following steps:

[0007] A vertical well is arranged at the target formation, wherein the vertical well includes a vertical well section and a docking cavity arranged at the bottom of the vertical well section;

[0008] The first horizontal well is laid out, and the end of the horizontal section of the first horizontal well is fixed in the docking cavity using the long-distance needle magnetic guidance technology;

[0009] The second horizontal well is laid out, and the end of the horizontal section of the second horizontal well is fixed in the docking cavity using the long-distance needle-threading magnetic guidance technology. The angle between the horizontal sections of the first horizontal well and the second horizontal well is 90° to 180°. The second horizontal well and the first horizontal well are symmetrically arranged about the vertical well to form a one-to-two U-shaped well group.

[0010] In some embodiments, the horizontal distance between the position where the first horizontal well is connected to the docking cavity and the position where the second horizontal well is connected to the docking cavity is 1 m to 5 m.

[0011] In some embodiments, the horizontal section lengths of the first horizontal well and the second horizontal well are both greater than or equal to 500 m.

[0012] In some embodiments, the horizontal sections of the first horizontal well and the second horizontal well do not intersect with the development faults of the formation.

[0013] In some embodiments, the wellbores of the vertical well, the first horizontal well, and the second horizontal well include a heat exchange casing and a surface casing, and the surface casing is arranged at the periphery of the end of the heat exchange casing close to the surface and is coaxially tightly connected thereto.

[0014] In some embodiments, the diameter of the heat exchange sleeve is 170-180-177.8 mm, and the diameter of the surface sleeve is 240-270 mm.

[0015] In some embodiments, the heat exchange casing is installed at a depth greater than or equal to 2500 m in the formation, and the surface casing is installed at a depth of 100 to 500 m.

[0016] In some embodiments, the docking cavity includes a three-way structure formed by at least two fiberglass sleeves.

[0017] Another aspect of the present invention provides a one-to-two U-shaped well group for deep geothermal development, comprising:

[0018] A vertical well, the vertical well comprising a vertical well section and a docking cavity arranged at the bottom of the vertical well section;

[0019] A first horizontal well, the first horizontal well comprising a first vertical section, a first inclined well section and a first horizontal section, and an end of the first horizontal section is fixed in the docking cavity;

[0020] The second horizontal well includes a second vertical section, a second inclined section and a second horizontal section. The end of the second horizontal section is fixed to the docking cavity. The angle between the first horizontal section and the second horizontal section is 90° to 180°. The second horizontal well and the first horizontal well are symmetrically arranged about the vertical well to form a one-to-two U-shaped well group.

[0021] In another aspect, the present invention provides a deep geothermal collection method, the method comprising the following steps:

[0022] Injecting heat exchange medium from the first horizontal well and the second horizontal well respectively, so that the two heat exchange mediums flow in the first horizontal well and the second horizontal well respectively and absorb heat from the formation to increase temperature;

[0023] The heated heat exchange medium is combined at the docking cavity and flows out through the wellhead of the vertical well;

[0024] The heat exchange medium is introduced into the heat-using system to release energy and cool down, and then it is divided into the first horizontal well and the second horizontal well for circulating heat exchange.

[0025] The present invention has at least the following beneficial technical effects:

[0026] The present invention provides a one-to-two U-shaped well group, a well completion method and a collection method for deep geothermal development. The advantages of the U-shaped well group formed by the method of the present invention over the one-to-one well group in the prior art are: (1) the drilling cost can be reduced under the same burial depth and well completion method, that is, one less vertical well can be drilled; (2) land acquisition costs can be saved and ground engineering investment can be reduced; and (3) the heat exchange efficiency is greatly improved by injecting into two horizontal wells at the same time, which significantly improves the development effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present invention. For ordinary technicians in this field, other embodiments can be obtained based on these drawings without paying creative work.

[0028] Figure 1 A schematic diagram of an embodiment of a one-to-two U-shaped well composition method for deep geothermal development provided by the present invention;

[0029] Figure 2 A schematic diagram of an embodiment of a one-to-two U-shaped well group provided by the present invention;

[0030] Figure 3 A schematic diagram of an embodiment of a one-to-two U-shaped well group well location deployment provided by the present invention.

[0031] Description of reference numerals:

[0032] 10. Vertical well; 11. Heat exchange casing; 12. Surface casing; 13. Docking cavity; 20. First horizontal well; 30. Second horizontal well. DETAILED DESCRIPTION

[0033] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the embodiments of the present invention are further described in detail below in combination with specific embodiments and with reference to the accompanying drawings.

[0034] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by technicians in the technical field of the present invention; the terms used in this specification are only for the purpose of describing specific embodiments and are not intended to limit the present invention. For example, the directions or positions indicated by the terms "length", "width", "up", "down", "left", "right", "front", "back", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc. are based on the directions or positions shown in the drawings, which are only for the convenience of description and should not be understood as limitations on the present technical solution.

[0035] The terms "including" and "having" and any variations thereof in the specification and claims of the present invention and the above-mentioned drawings are intended to cover non-exclusive inclusions; the terms "first", "second", etc. in the specification and claims of the present invention or the above-mentioned drawings are used to distinguish different objects rather than to describe a specific order. "Multiple" means two or more, unless otherwise clearly and specifically defined.

[0036] In the specification and claims of the present invention and the above-mentioned drawings, when an element is referred to as being "fixed to" or "mounted on" or "disposed on" or "connected to" another element, it may be directly or indirectly located on the other element. For example, when an element is referred to as being "connected to" another element, it may be directly or indirectly connected to the other element.

[0037] In addition, reference to "embodiments" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present invention. The appearance of the phrase in various places in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0038] like Figure 1 As shown, the present invention proposes a method for forming a one-to-two U-shaped well for deep geothermal development, comprising the following steps:

[0039] S1. Deploy a vertical well at the target formation, wherein the vertical well includes a vertical well section and a docking cavity arranged at the bottom of the vertical well section;

[0040] S2. Laying out the first horizontal well, and fixing the end of the horizontal section of the first horizontal well in the docking cavity by using the long-distance needle magnetic guidance technology;

[0041] S3. Lay out the second horizontal well, and use the long-distance needle-threading magnetic guidance technology to fix the end of the horizontal section of the second horizontal well in the docking cavity. The angle between the horizontal sections of the first horizontal well and the second horizontal well is 90° to 180°. The second horizontal well and the first horizontal well are symmetrically arranged about the vertical well to form a one-to-two U-shaped well group.

[0042] Further, in S1, the vertical well RU2-1 is completed first, and the docking cavity is There are at least 2 fiberglass casings with a total length of no less than 10m. The vertical wellbore includes a heat exchange casing and a surface casing. The surface casing is arranged on the periphery of the end of the heat exchange casing close to the surface and is coaxially and tightly connected. The depth is not less than 2500m, and the diameter of the surface casing is or The depth is determined by the depth of the surface water bottom in the heat-using area, which is generally between 100m and 500m.

[0043] Furthermore, in S2, the first horizontal well RU2-H1 is laid, and the long-distance magnetic guidance technology (MGD-C) is used to connect the end of the horizontal section of the RU2-H1 well to the docking cavity of the vertical well RU2-1 well.

[0044] Furthermore, in S3, the second horizontal well U2-H2 is laid, and the long-distance magnetic guidance technology (MGD-C) is used to connect the end of the horizontal section of the RU2-H2 well to the docking cavity of the vertical well RU2-1.

[0045] Furthermore, the first horizontal well and the second horizontal well are both composed of a vertical section, an inclined well section, and a horizontal section. The wellbore of the vertical section includes a heat exchange casing and a surface casing. The surface casing is arranged at the periphery of the end of the heat exchange casing close to the surface and is coaxially tightly connected. The diameter of the heat exchange casing is 170 to 180177.8 mm, and the diameter of the surface casing is 240 to 270 mm. In some embodiments, the surface casing is (or ), the depth is determined by the depth of the surface water bottom plate in the heat-using area, generally between 100m and 500m; the specifications of the heat exchange casing are or The vertical depth of the horizontal section shall not be less than 2500m, and the distance between the horizontal section and the front of the target shall not be less than 500m.

[0046] Furthermore, the horizontal sections of the first horizontal well and the second horizontal well cannot intersect with the developed faults in the formation where the horizontal sections are located.

[0047] The advantages of the present invention are mainly reflected in four aspects: first, the drilling cost can be reduced under the same burial depth and well formation mode, that is, one less vertical well is drilled compared with the traditional "one-to-one U-shaped well group"; second, the land acquisition cost is saved; third, the ground engineering investment is reduced; and fourth, the development effect is significantly improved. As shown in Table 1, the heat exchange effect comparison between the "one-to-two U-shaped well group" and the "one-to-one U-shaped well group" shows that the heat exchange power of the "one-to-two U-shaped well group" is nearly twice that of the "one-to-one U-shaped well group" under the same heat exchange depth, horizontal section length, and heat exchange casing specifications.

[0048] Table 1 Comparison of heat exchange development effects between "one-to-two U-shaped well group" and "one-to-one U-shaped well group"

[0049]

[0050] Another aspect of the present invention provides a one-to-two U-shaped well group for deep geothermal development, wherein the well group is formed by the above method, such as Figure 2 As shown, the well group includes:

[0051] A vertical well 10, the vertical well 10 comprises a vertical well section and a docking cavity 13 arranged at the bottom of the vertical well section;

[0052] A first horizontal well 20, the first horizontal well 20 comprises a first vertical section, a first inclined well section and a first horizontal section, and an end of the first horizontal section is fixed in the docking cavity 13;

[0053] The second horizontal well 30 includes a second vertical section, a second inclined section and a second horizontal section. The end of the second horizontal section is fixed to the docking cavity 13. The angle between the first horizontal section and the second horizontal section is 90° to 180°. The second horizontal well and the first horizontal well are symmetrically arranged about the vertical well to form a one-to-two U-shaped well group.

[0054] Furthermore, the wellbores of the vertical well, the first horizontal well and the second horizontal well include a heat exchange casing 11 and a surface casing 12. The surface casing 12 is arranged at the periphery of the end of the heat exchange casing 11 close to the surface and is coaxially and tightly connected.

[0055] Furthermore, if Figure 3 In the schematic diagram of an embodiment of the U-shaped well group well location deployment shown, based on the actual geographical location, the angle between the first horizontal section and the second horizontal section is set to 120°.

[0056] Furthermore, those skilled in the art should understand that the well group structure of the present invention is not limited to the one-to-two form, and can also be designed as a one-to-many form based on this and in combination with actual needs. Specifically, the docking cavity has multiple docking ports, and multiple horizontal wells are arranged with the vertical well as the center. Each horizontal well includes a vertical well section, an inclined well section and a horizontal section. The end of each horizontal section is fixedly connected to the docking cavity through a docking port. Multiple horizontal wells are symmetrically arranged about the vertical well to form a one-to-many U-shaped well group, and the angle between the horizontal section of each horizontal well and the horizontal section of the adjacent horizontal well is 90° to 180°.

[0057] Another aspect of the present invention provides a deep geothermal collection method, which uses the above-mentioned deep geothermal development one-to-two U-shaped well group to collect geothermal energy, including the following steps:

[0058] S1. Injecting heat exchange medium from the first horizontal well and the second horizontal well respectively, so that the two heat exchange mediums flow in the first horizontal well and the second horizontal well respectively and absorb heat from the formation to increase the temperature;

[0059] S2, making the heated heat exchange medium merge at the docking cavity and flow out through the wellhead of the vertical well;

[0060] S3, introducing the heat exchange medium into the heat system to release energy and cool down, and then diverting it into the first horizontal well and the second horizontal well for circulating heat exchange.

[0061] The above are exemplary embodiments disclosed in the present invention, but it should be noted that various changes and modifications may be made without departing from the scope disclosed in the embodiments of the present invention as defined in the claims. The functions, steps and / or actions of the method claims according to the disclosed embodiments described herein do not need to be performed in any particular order. In addition, although the elements disclosed in the embodiments of the present invention may be described or required in individual form, they may also be understood as multiple unless explicitly limited to the singular.

[0062] It should be understood that, as used herein, the singular forms "a", "an" are intended to include the plural forms as well, unless the context clearly supports an exception. It should also be understood that, as used herein, "and / or" refers to any and all possible combinations including one or more of the associated listed items.

[0063] The serial numbers of the embodiments disclosed in the above embodiments of the present invention are only for description and do not represent the advantages or disadvantages of the embodiments.

[0064] A person skilled in the art should understand that the discussion of any of the above embodiments is only exemplary and is not intended to imply that the scope of the disclosure of the embodiments of the present invention (including the claims) is limited to these examples; under the concept of the embodiments of the present invention, the technical features in the above embodiments or different embodiments can also be combined, and there are many other changes in different aspects of the embodiments of the present invention as above, which are not provided in detail for the sake of simplicity. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the embodiments of the present invention should be included in the protection scope of the embodiments of the present invention.

Claims

1. A method for forming a one-to-two U-shaped well for deep geothermal development, characterized in that: include: Arrange a vertical well at the target formation, the vertical well comprising a vertical well section and a docking cavity arranged at the bottom of the vertical well section; Laying out a first horizontal well, and fixing the end of the horizontal section of the first horizontal well in the docking cavity by using a long-distance needle-threading magnetic guidance technology; A second horizontal well is arranged, and the end of the horizontal section of the second horizontal well is fixed in the docking cavity by using long-distance needle-threading magnetic guidance technology. The angle between the horizontal sections of the first horizontal well and the second horizontal well is 90° to 180°. The second horizontal well and the first horizontal well are symmetrically arranged about the vertical well to form a one-to-two U-shaped well group.

2. The one-to-two U-shaped well formation method for deep geothermal development according to claim 1 is characterized in that: A horizontal distance between a position where the first horizontal well is connected to the docking cavity and a position where the second horizontal well is connected to the docking cavity is 1 m to 5 m.

3. The one-to-two U-shaped well formation method for deep geothermal development according to claim 1 is characterized in that: The horizontal section lengths of the first horizontal well and the second horizontal well are both greater than or equal to 500 m.

4. The one-to-two U-shaped well formation method for deep geothermal development according to claim 1 is characterized in that: The horizontal sections of the first horizontal well and the second horizontal well have no intersection with the faults developed in the formation.

5. The one-to-two U-shaped well formation method for deep geothermal development according to claim 1 is characterized in that: The wellbores of the vertical well, the first horizontal well and the second horizontal well include a heat exchange casing and a surface casing. The surface casing is arranged at the periphery of the end of the heat exchange casing close to the surface and is coaxially and tightly connected thereto.

6. The one-to-two U-shaped well formation method for deep geothermal development according to claim 5 is characterized in that: The diameter of the heat exchange sleeve is 170-180177.8 mm, and the diameter of the surface sleeve is 240-270 mm.

7. The one-to-two U-shaped well formation method for deep geothermal development according to claim 5 is characterized in that: The heat exchange casing is installed at a depth greater than or equal to 2500m in the stratum, and the surface casing is installed at a depth of 100 to 500m.

8. The one-to-two U-shaped well formation method for deep geothermal development according to claim 1 is characterized in that: The docking cavity comprises a three-way structure formed by at least two glass fiber reinforced plastic sleeves.

9. A one-to-two U-shaped well group for deep geothermal development, characterized in that: include: A vertical well, the vertical well comprising a vertical well section and a docking cavity arranged at the bottom of the vertical well section; A first horizontal well, the first horizontal well comprising a first vertical section, a first inclined well section and a first horizontal section, an end of the first horizontal section being fixed in the docking cavity; The second horizontal well comprises a second vertical section, a second inclined section and a second horizontal section, the end of the second horizontal section is fixed to the docking cavity, the angle between the first horizontal section and the second horizontal section is 90° to 180°, and the second horizontal well and the first horizontal well are symmetrically arranged with respect to the vertical well to form a one-to-two U-shaped well group.

10. A deep geothermal collection method, characterized in that: The one-to-two U-shaped well group for deep geothermal development as described in claim 8 is used for geothermal collection, and the method comprises: Injecting heat exchange medium from the first horizontal well and the second horizontal well respectively, so that the two heat exchange mediums flow in the first horizontal well and the second horizontal well respectively and absorb heat from the formation to increase temperature; The heated heat exchange medium is combined at the docking cavity and flows out through the wellhead of the vertical well; The heat exchange medium is introduced into the heat system to release energy and cool down, and then is divided into the first horizontal well and the second horizontal well again for circulating heat exchange.

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