Single-well terrestrial heat exploitation device and terrestrial heat exploitation method

Abstract

The invention discloses a single-well geothermal exploitation device which comprises a closed oil pipe, a packer and a lifting pipe column. Wherein the closed oil pipe, the packer and the lifting pipe column are arranged in a single well, and one end of the oil pipe and one end of the lifting pipe column are arranged at a wellhead; the packer is arranged on the oil pipe, connected with the inner wall of the single well and used for dividing the single well into an upper part and a lower part; the lifting pipe column is arranged at the upper part of the single well; and a heat-conducting medium is filled in the oil pipe. After deep geothermal energy is transferred to a shallow layer through the hot rod, cold water is only injected into the upper portion of a single well through the lifting pipe column, and the problems that the whole section of a shaft is lifted, and energy consumption is large are solved; meanwhile, only a heat-insulating section of the oil pipe is a heat-insulating oil pipe, and other sections of the oil pipe are common oil pipes, so that the problem that deep well development is limited due to tensile strength of the heat-insulating oil pipe when the heat-insulating oil pipe is used in a whole shaft is solved.

Description

Technical Field

[0001] The present invention relates to the technical field of geothermal development, and in particular to a single-well geothermal mining device and a geothermal mining method. Background Art

[0002] In recent years, the demand for fossil energy has increased year by year, resulting in increasing pressure on supply and demand, and the environmental pollution caused by it has also become increasingly serious. The development and utilization of renewable energy is an effective way to solve the above problems. The International Energy Agency (IEA) pointed out that by 2040, renewable energy will account for at least half of the growth in global total power generation. Compared with other renewable resources such as solar energy, wind energy and tidal energy, geothermal resources have the advantages of wide geographical distribution, large resources, clean and environmental protection, and good thermal energy continuity. However, according to the IEA report data: in 2017, compared with bioenergy (50%), hydropower (31%), wind energy (9%) and solar energy (8%), geothermal energy only accounted for 2% of global renewable energy consumption. An important reason for the low market share of geothermal energy is its high development cost, of which the drilling cost accounts for 50% of the total cost of geothermal projects. Reducing the cost of geothermal drilling is an important measure to promote the large-scale utilization of geothermal energy, and the development of geothermal resources using abandoned wells is expected to become an effective way to solve the problem of geothermal well development costs.

[0003] Usually, the geothermal gradient in the area where the oil field is located is high, and many abandoned wells contain rich geothermal resources. According to relevant statistics, there are currently 20 to 30 million abandoned wells in the world, and the number of abandoned wells in my country has exceeded 100,000. Domestic and foreign scholars have conducted a lot of research on abandoned well transformation measures and heat extraction applications. At present, the most commonly used method is the downhole heat exchanger (BHE) heat extraction method. The existing downhole heat exchanger heat extraction method mainly uses a pump to pump cold water into the annulus of the oil casing. The liquid passes from the wellhead through the annulus of the oil casing to the bottom of the well, absorbs heat from the formation, and the temperature rises. Then it is lifted from the bellmouth to the ground, and the heat is used on the ground before being pumped back into the well, forming a cycle to achieve the effect of geothermal energy development, such as Figure 1 This method has the following two problems: (1) the whole wellbore is lifted, which consumes a lot of energy; (2) the whole wellbore uses insulated oil pipes, which limits the development of deep wells due to the tensile strength of the insulated oil pipes. Summary of the invention

[0004] The object of the present invention is to provide a single-well geothermal production device and a geothermal production method to solve the above-mentioned technical problems.

[0005] To achieve the above-mentioned object, the present invention provides a single-well geothermal production device, the device comprising: a sealed oil pipe, a packer, and a lifting string;

[0006] Wherein, the sealed oil pipe, the packer and the lifting string are arranged in a single well, and one end of the oil pipe and the lifting string is arranged at the wellhead; the packer is arranged on the oil pipe and connected to the inner wall of the single well, so as to divide the single well into two parts, upper and lower; the lifting string is arranged in the upper part of the single well; the oil pipe is filled with a heat-conducting medium.

[0007] The present invention also provides a geothermal mining method, the method comprising:

[0008] A packer is set on the tubing which is sealed at one end;

[0009] lowering the oil pipe and lift string into a single well;

[0010] Injecting heat transfer medium from the other end of the oil pipe and sealing the other end;

[0011] Inject cold water into the well through the lifting string, and discharge hot water converted by geothermal heat out of the well;

[0012] Wherein, one end of the oil pipe and the lifting string are arranged at the wellhead; the packer is connected to the inner wall of the single well to divide the single well into upper and lower parts; the lifting string is arranged in the upper part of the single well.

[0013] Technical effects and advantages of the present invention:

[0014] The present invention provides a single-well geothermal exploitation device, which comprises: a sealed oil pipe, a packer, and a lifting pipe string; wherein the sealed oil pipe, the packer, and the lifting pipe string are arranged in a single well, and one end of the oil pipe and the lifting pipe string are arranged at the wellhead; the packer is arranged on the oil pipe and connected to the inner wall of the single well, so as to divide the single well into an upper and lower part; the lifting pipe string is arranged in the upper part of the single well; and a heat-conducting medium is contained in the oil pipe.

[0015] After the deep geothermal energy is transferred to the shallow position by the "heat rod" of the present invention, the cold water is injected into the upper part of the single well by means of the lifting pipe string, thereby solving the problem of high energy consumption caused by lifting the whole section of the wellbore in the prior art. At the same time, the oil pipe in the present invention uses the insulated oil pipe only in the insulated section, while the other sections use the ordinary oil pipe, thus solving the problem of using the insulated oil pipe in the whole wellbore in the prior art, which limits the deep well development due to the tensile strength of the insulated oil pipe.

[0016] Other features and advantages of the present invention will be described in the following description, and partly become obvious from the description, or be understood by implementing the present invention. The purpose and other advantages of the present invention can be realized and obtained by the structures pointed out in the description and the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is a diagram of a heat extraction device for a downhole heat exchanger in the prior art;

[0018] Figure 2 This is the hot rod structure diagram;

[0019] Figure 3 This is a schematic diagram of the geothermal production string of the original well;

[0020] Figure 4 Schematic diagram of the geothermal production string for side-drilling wells. DETAILED DESCRIPTION

[0021] The technical solution of the present invention will be clearly and completely described below in conjunction with the accompanying drawings provided by the present invention, and the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0022] It should be noted that the structures, proportions, sizes, etc. illustrated in the drawings of this specification are only used to match the contents disclosed in the specification for people familiar with this technology to understand and read, and are not used to limit the limiting conditions for the implementation of the present invention, so they have no substantial technical significance. Any modification of the structure, change of the proportion relationship or adjustment of the size should still fall within the scope of the technical content disclosed by the present invention without affecting the effects and purposes that can be achieved by the present invention. At the same time, the terms such as "upper", "lower", "left", "right", "middle" and "one" quoted in this specification are only for the convenience of description, and are not used to limit the scope of the implementation of the present invention. The change or adjustment of their relative relationship should also be regarded as the scope of the implementation of the present invention without substantially changing the technical content.

[0023] In order to better understand this solution, the basic principles of the present invention are first introduced:

[0024] This patent mainly uses the "hot rod" principle to transfer deep geothermal heat to shallow strata, and then circulates it through a water medium to carry the energy to the ground for use, and then pumps it into the well to achieve the effect of circulating geothermal energy.

[0025] The hot rod is a sealed tube filled with substances such as ammonia, freon, propane, and carbon dioxide. The upper section of the tube is the condenser, the lower end is the evaporator, and the middle is the insulation section. When the lower end of the hot pile absorbs heat, the liquid substance will be converted into gas, and then rise to the condenser, and the heat will be dissipated through the condenser. The gaseous substance is then liquefied into liquid and flows back to the lower end of the hot pile under the action of gravity. The substance in the hot rod is constantly converted between gas and liquid, relying on the unidirectional thermal conductivity of the hot rod and the efficient heat transfer and heat dissipation efficiency, thereby continuously transferring heat upward, such as Figure 2 shown.

[0026] This patent applies the "hot rod" principle to the field of geothermal exploitation. The "hot rod" is used to transfer deep geothermal energy to shallow positions, reducing lifting energy consumption. At the same time, the abandoned oil well can be used for side drilling to lower the "hot rod" to a deeper position, where the formation temperature is higher and the utilization efficiency is higher. Figure 3 , Figure 4 As shown. In theory, the closed oil pipe ("heat rod") is divided into three parts: "heat dissipation section", "heat insulation section" and "heat absorption section". The "heat dissipation section" and "heat absorption section" use ordinary oil pipes (i.e. standard oil pipes), and the "heat insulation section" uses insulated oil pipes to reduce heat loss during heat transfer. The lower "heat absorption section" absorbs the heat of the formation, vaporizes the filler in the heat rod, and carries the heat up to the "heat dissipation section". After the heat is dissipated, the filler liquefies and releases the heat, and flows back to the "heat absorption section" due to its own gravity, forming a self-circulating heat lift without external power.

[0027] The single-well geothermal production device of the present invention is explained in detail below. The device includes: a sealed oil pipe, a packer, and a lifting string;

[0028] Specifically, the sealed oil pipe, the packer and the lifting string are arranged in a single well, and one end of the oil pipe and the lifting string is arranged at the wellhead; the packer is arranged on the oil pipe and connected to the inner wall of the single well, so as to divide the single well into two parts, upper and lower; the lifting string is arranged in the upper part of the single well.

[0029] Among them, the oil pipe located in the upper part is the heat dissipation section; the lower part of the oil pipe is divided into two sections, the upper section is the heat insulation section, and the lower section is the heat absorption section; the oil pipe of the heat insulation section adopts an insulated oil pipe, and the oil pipes of the heat dissipation section and the heat absorption section adopt standard oil pipes.

[0030] Specifically, the oil pipe is filled with a heat-conducting medium, wherein the heat-conducting medium includes at least one of the following: ammonia, freon, propane, and carbon dioxide.

[0031] The present invention also provides a geothermal exploitation method using the above device, which mainly includes geothermal development of the original well and geothermal development of the side-drilling well, and the specific steps are as follows:

[0032] 1. When selecting wells, the following principles should be followed in selecting target wells: 1) Abandoned wells with geothermal development value should have higher reservoir temperature, better permeability and porosity (open system utilization). The above physical parameters need to be analyzed based on the existing historical data of the well, and the economic value of the target well should be evaluated; 2) The output heat should be easy to use. There should be geothermal power stations (for power generation), residential areas (for cooling, heating and bathing) around the abandoned wells, and excessive heat loss due to long heating paths should be avoided as much as possible; 3) Abandoned wells with casing completion should be selected as much as possible to facilitate later transformation.

[0033] 2. During on-site construction, first lower the sealed oil pipe ("hot rod" pipe string), then lower the lifting oil pipe. The pipe string structure is as follows: Figure 3 , Figure 4 shown.

[0034] 3. Inject heat-conducting medium into the "hot rod" pipe column, and seal the "hot rod" with a wire plug to make the inside of the pipe a closed cavity.

[0035] 4. The “heat rod” continuously lifts the heat upwards and uses the sealer to achieve sealing.

[0036] 5. Inject cold water into the well through the lifting oil pipe, carry out heat exchange, and discharge the hot water after exchange from the wellhead.

[0037] Finally, it should be noted that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments or to make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A single well geothermal extraction device, It is characterized in that The device comprises: a sealed oil pipe, a packer, and a lifting pipe string; Wherein, the sealed oil pipe, the packer and the lifting string are arranged in a single well, and one end of the oil pipe and the lifting string is arranged at the wellhead; the packer is arranged on the oil pipe and connected to the inner wall of the single well, so as to divide the single well into two parts, upper and lower; the lifting string is arranged in the upper part of the single well; the oil pipe is filled with a heat-conducting medium.

2. The device according to claim 1, It is characterized in that The heat transfer medium includes at least one of the following: ammonia, freon, propane, and carbon dioxide.

3. The device according to claim 1, It is characterized in that The oil pipe located at the upper part is a heat dissipation section.

4. The device according to claim 3, It is characterized in that The lower part of the oil pipe is divided into two sections, an upper section and a lower section.

5. The device according to claim 4, It is characterized in that The upper section of the lower part of the oil pipe is a heat insulation section, and the lower section of the lower part of the oil pipe is a heat absorption section.

6. The device according to claim 5, It is characterized in that The oil pipe of the heat insulation section adopts a heat insulation oil pipe.

7. The device according to claim 5, It is characterized in that The oil pipes of the heat dissipation section and the heat absorption section are standard oil pipes.

8. A geothermal extraction method based on the device according to any one of claims 1 to 7, It is characterized in that The method comprises: A packer is set on the tubing which is sealed at one end; lowering the oil pipe and lift string into a single well; Injecting heat-conducting medium from the other end of the oil pipe and sealing the other end; Inject cold water into the well through the lifting string, and discharge hot water converted by geothermal heat out of the well; Wherein, one end of the oil pipe and the lifting string are arranged at the wellhead; the packer is connected to the inner wall of the single well to divide the single well into upper and lower parts; the lifting string is arranged in the upper part of the single well.

9. The method according to claim 8, It is characterized in that The heat transfer medium includes at least one of the following: ammonia, freon, propane, and carbon dioxide.

10. The method according to claim 8, It is characterized in that The oil pipe located at the upper part is a heat dissipation section.

11. The method according to claim 8, It is characterized in that The lower part of the oil pipe is divided into two sections, an upper section and a lower section.

12. The method according to claim 11, It is characterized in that in, The upper section of the lower part of the oil pipe is a heat insulation section, and the lower section of the lower part of the oil pipe is a heat absorption section.

13. The method according to claim 12, It is characterized in that The oil pipe of the heat insulation section adopts a heat insulation oil pipe.

14. The method according to claim 12, It is characterized in that The oil pipes of the heat dissipation section and the heat absorption section are standard oil pipes.

15. The method according to claim 8, It is characterized in that Before lowering the oil pipe and the lifting string into the single well, the method further includes: selecting a single well that meets the requirements.

16. The method according to claim 15, It is characterized in that The single wells that meet the requirements include: abandoned wells with geothermal development value, and the abandoned wells have reservoir temperature, permeability and porosity that meet the requirements; there are equipment that uses heat near the single well; the single well is an abandoned well with complete casing.

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