Water jacket high-temperature product well system for underground coal gasification process

Abstract

The utility model relates to a water jacket high-temperature product well system for a coal underground gasification process. The water jacket high-temperature product well system comprises an underground gasification furnace, a product well, an oil pipe and a casing pipe, the product well is formed in the ground and extends to a coal seam, the casing pipe is connected to a wellhead of the product well and arranged outside the oil pipe in a sleeving mode, and the oil pipe is erected at one end of the wellhead and hung in the product well. The underground gasification furnace is located below a coal seam and conducts controllable combustion on the coal seam, and high-temperature synthesis gas generated through combustion is conveyed to a wellhead through an oil pipe; according to the water jacket high-temperature product well system, the high-temperature packer, the oil pipe, the sleeve and the continuous pipe are utilized to form the water jacket, the water jacket becomes a circulation channel of cooling water in the whole circulation system, and indirect heat exchange is conducted on the cooling water and high-temperature synthesis gas through cooperation of the circulation channel and the cooling water circulation system, so that temperature control over a product well is achieved. Therefore, water consumption of cooling water is reduced, and waste heat is recovered.

Description

Technical Field

[0001] The utility model belongs to the technical field of underground coal gasification technology, and in particular relates to a water-jacketed high-temperature product well system used in underground coal gasification technology. Background Art

[0002] Underground coal gasification (ISC) is a process that converts coal directly into product gas, usually called synthesis gas, by combustion and gasification of underground coal seams in the presence of an oxidant. The synthesis gas can then be used as a feedstock for a variety of applications, including fuel production, chemical production, and power generation. This underground coal gasification technology is applicable to most coal deposits. In view of the increasingly stringent environmental requirements for the mining industry and considering the related labor and infrastructure costs, this technology is undoubtedly very attractive.

[0003] Surface wells penetrate the coal seam directly, providing an effective channel for oxidant injection and product gas production. A pair of wells are connected or extended horizontally underground to form a substantially horizontal drilling channel (also referred to as a coal seam well or connecting channel). This channel facilitates oxidant injection, combustion zone growth and product gas transportation. A well used for oxidant injection is called an "injection well" and the other well used for producing product gas is called a "product well". Both directional horizontal drilling and vertical drilling can be used as injection wells or product wells. Underground coal gasification (ISC) may also require the use of one or more vertical wells (e.g., functional wells and auxiliary wells) between the injection well and the product well.

[0004] When there are injection wells, product wells and horizontal channels connecting the two in a coal seam, this structure is called an underground coal gasification (ISC) unit or well pair. The ISC unit includes a combustion zone, a gasification zone and a pyrolysis zone. Among them, the combustion zone is near the oxidant injection point in the coal seam; the gasification zone surrounds the combustion zone in a radial form or is downstream of the combustion zone, and the coal is gasified and partially oxidized in the gasification zone to generate product gas; the pyrolysis zone is downstream of the gasification zone, and the pyrolysis reaction of coal generally occurs here. The high-temperature product gas flows downstream from the gasification zone and is eventually transported to the ground from the wellhead of the product well. While the coal is burning or gasifying, the ISC combustion zone in the coal seam will grow and become larger.

[0005] The product gas (raw synthesis gas) generated by underground coal gasification usually contains synthesis gas (a mixture of CO, CO2, H2, CH4 and other gases) and other components such as solid particles, water, coal tar, hydrocarbon vapor, and other trace components including H2S, NH4, COS, etc.). The complexity of its composition depends on many aspects: the oxidant used in underground coal gasification (air or other oxidants, such as oxygen, oxygen-enriched air or steam mixture), the intrinsic water in the coal seam or the water infiltrating into the coal seam from the surrounding strata, the coal quality and the operating parameters of the underground coal gasification process, including temperature, pressure, etc.

[0006] In conventional underground gasifier product wells, when high-temperature syngas passes through the wellbore of the product well, the syngas temperature is overheated, causing the casing, oil pipe and cement in the wellbore to be damaged under the action of thermal stress, which further leads to the degradation of the sealing performance of the wellbore and causes fluid (such as oil, gas or water) to leak, which may not only lead to waste of resources, but also cause pollution to the surrounding environment. Summary of the invention

[0007] The purpose of the utility model is to provide a water jacketed high temperature product well system with a simple structure and reasonable design in order to solve the above problems.

[0008] The utility model achieves the above-mentioned purpose through the following technical solutions:

[0009] A water-jacketed high-temperature product well system for underground coal gasification process, comprising an underground gasifier, a product well, an oil pipe and a casing, wherein the product well is opened on the ground and extends to the coal seam, the casing is connected to the wellhead of the product well and is sleeved on the outside of the oil pipe, the oil pipe is mounted at one end of the wellhead and suspended inside the product well, the underground gasifier is located below the coal seam and performs controllable combustion on the coal seam, and the high-temperature synthesis gas generated by the combustion is transported to the wellhead through the oil pipe, the inner wall of the casing at one end away from the wellhead is connected to a high-temperature packer, the high-temperature packer is sleeved on the surface of the oil pipe, and the upper surface of the high-temperature packer forms a cavity with the inner wall of the casing and the surface of the oil pipe;

[0010] A cooling water circulation mechanism is arranged on the ground, and the cooling water circulation mechanism includes a water storage component, a ground manifold and a heat exchanger. The water storage component and the heat exchanger are connected via the ground manifold. The water storage component injects cooling water into the cavity via the water injection port of the ground manifold to cool down the high-temperature synthesis gas in the oil pipe. The water storage component guides the cooling water heated in the cavity from the water inlet port of the ground manifold to the heat exchanger for heat exchange and cooling, and thereby circulates and injects the water into the cavity.

[0011] As a further optimization solution of the utility model, the underground gasification furnace uses injected oxidant to carry out controllable combustion of the coal seam.

[0012] As a further optimization solution of the utility model, a certain gap is reserved between the casing and the inner wall of the production well, and cement is injected into the gap to form a cementing cement ring.

[0013] As a further optimization solution of the present invention, the top of the sleeve is connected with an airtight buckle for sealing the sleeve.

[0014] As a further optimization scheme of the utility model, the water storage assembly includes a water injection pump, a water reservoir and a valve. The water reservoir and the water injection pump are connected in sequence to one side of the heat exchanger close to the water injection port of the ground manifold through a ground manifold. The valve is connected to a position of the ground manifold close to the water injection port to adjust the cooling water flow rate.

[0015] As a further optimization scheme of the utility model, the cooling water circulation mechanism also includes a continuous pipe, which is installed in the wellhead, one end of the continuous pipe is connected to the water injection port of the ground manifold through the wellhead bypass, and the other end extends to the bottom of the cavity, and the water inlet port of the ground manifold extends to the inside of the cavity close to the wellhead.

[0016] As a further optimization solution of the utility model, one end of the oil pipe away from the wellhead extends into the casing and is connected to a screen pipe, and the screen pipe extends to the coal seam to prevent foreign matter from entering the oil pipe.

[0017] The beneficial effect of the utility model is that the utility model utilizes a high-temperature packer, an oil pipe, a casing and a continuous pipe to form a water jacket, which becomes a circulation channel for cooling water in the entire circulation system. Through the cooperation of this circulation channel and the cooling water circulation system, the cooling water and the high-temperature synthesis gas are indirectly heat exchanged to achieve temperature control of the product well, thereby reducing the cooling water consumption and recovering waste heat. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a schematic diagram of a water-jacketed high-temperature product well system of the utility model.

[0019] In the figure: 1. Coal seam; 2. Screen pipe; 3. High-temperature packer; 4. Continuous pipe; 5. Casing; 6. Cementing cement ring; 7. Valve; 8. Wellhead; 9. Surface manifold; 10. Underground gasifier; 11. Oil pipe; 12. Water injection pump; 13. Water reservoir; 14. Heat exchanger. DETAILED DESCRIPTION

[0020] The present application is further described in detail below in conjunction with the accompanying drawings. It is necessary to point out here that the following specific implementation methods are only used to further illustrate the present application and cannot be understood as limiting the scope of protection of the present application. Technical personnel in this field can make some non-essential improvements and adjustments to the present application based on the above application content.

[0021] like Figure 1As shown, a water-jacketed high-temperature product well system for underground coal gasification process includes an underground gasifier 10, a product well, an oil pipe 11 and a casing 5, wherein the product well is opened on the ground and extends to the coal seam 1, the casing 5 is connected to the wellhead 8 of the product well and is sleeved on the outside of the oil pipe 11, the oil pipe 11 is erected at one end of the wellhead 8 and suspended inside the product well, the underground gasifier 10 is located below the coal seam 1 and performs controllable combustion on the coal seam 1, and the high-temperature synthesis gas generated by the combustion is transported to the wellhead 8 through the oil pipe 11, and the inner wall of the casing 5 away from the wellhead 8 is connected to a high-temperature packer 3, the high-temperature packer 3 is sleeved on the surface of the oil pipe 11, and the upper surface of the high-temperature packer 3 forms a cavity with the inner wall of the casing 5 and the surface of the oil pipe 11;

[0022] A cooling water circulation mechanism is provided on the ground, and the cooling water circulation mechanism includes a water storage component, a ground manifold 9 and a heat exchanger 14. The water storage component and the heat exchanger 14 are connected through the ground manifold 9. The water storage component injects cooling water into the cavity through the water injection port of the ground manifold 9 to cool the high-temperature synthesis gas in the oil pipe 11. The water storage component guides the cooling water heated in the cavity from the water inlet port of the ground manifold 9 to the heat exchanger 14 for heat exchange and cooling, and thus circulates and injects it into the cavity.

[0023] High temperature packer 3: After the packer is set, it can seal the oil pipe 11 and the casing annulus (i.e., cavity). The material used for the packer can meet the high temperature of 800°C of the synthetic gas and can withstand the water column pressure of the cooling water;

[0024] Oil pipe 11: The material of the oil pipe 11 can meet the corrosion requirements of the synthesis gas, and can be stainless steel, chromium alloy, nickel-chromium alloy, monel, etc. The inner diameter of the oil pipe 11 must meet the size required for the synthesis gas output, and the specific size is: 5-95 / 8 inches;

[0025] Casing 5: The material of the casing 5 can meet the corrosion requirements of the synthetic gas, specifically, it can be stainless steel, chromium alloy, nickel-chromium alloy, Monel, etc. The size of the casing 5 is: 95 / 8-133 / 8 inches;

[0026] Wellhead 8: used to connect casing 5. Oil pipe 11 is suspended inside wellhead 8 and connected to the synthesis gas pipeline on the ground. Coiled pipe 4 is installed in wellhead 8 and connected to the water injection end of ground manifold 9 through wellhead bypass. A cooling water return outlet is provided on one side of wellhead 8 and connected to the water inlet port of ground manifold 9. The wellhead needs to meet the high temperature requirement of synthesis gas, and the specific design temperature is not less than 350°C.

[0027] It should be noted that the present solution utilizes the high-temperature packer 3, the oil pipe 11, the casing 5 and the coiled pipe 4 to form a water jacket, which becomes a circulation channel for cooling water in the entire circulation system. This circulation channel is utilized to perform indirect heat exchange with the high-temperature synthesis gas to achieve temperature control of the product well, reduce cooling water consumption and recover waste heat.

[0028] Through this circulation setting, this scheme can not only reduce the temperature of synthesis gas and protect the safe production of product wells, but also does not increase the wastewater generated by synthesis gas cooling, and can also realize the recovery and reuse of synthesis gas temperature, where the product well shaft refers to the part of the product well located underground.

[0029] It should be further explained that, since the temperature of the synthesis gas produced by the underground gasifier 10 is as high as 600°C to 800°C, the temperature of the synthesis gas is relatively high. In order to protect the safety of the product wellbore, a water jacket is used to reduce the temperature of the synthesis gas to below 350°C when the synthesis gas passes through the oil pipe 11, so as to prevent the high-temperature synthesis gas produced by the underground gasifier 10 from damaging the casing 5, the oil pipe 11 and the cementing cement ring 6, thereby ensuring the safe and stable operation of the underground gasifier 10.

[0030] Furthermore, the underground gasifier 10 controls the combustion of the coal seam 1 by injecting an oxidant.

[0031] Furthermore, a certain gap is reserved between the casing 5 and the inner wall of the production well, and cement is injected into the gap to form a cementing cement ring 6 .

[0032] Cementing cement ring 6: The performance decline period of the cement used in the cementing cement ring needs to meet the service life of the product well.

[0033] Furthermore, the top of the sleeve 5 is connected with an airtight buckle for sealing the sleeve 5 .

[0034] Furthermore, the water storage component includes a water injection pump 12, a water reservoir 13 and a valve 7. The water reservoir 13 and the water injection pump 12 are connected in sequence to one side of the heat exchanger 14 close to the water injection port of the ground manifold 9 through the ground manifold 9. The valve 7 is connected to the ground manifold 9 close to the water injection port to adjust the cooling water flow.

[0035] Water reservoir 13: The water reservoir 13 provides a storage place for cooling water and has the function of purifying cooling water.

[0036] Injection pump 12: The injection pump 12 is connected to the surface manifold 9 to inject cooling water into the product well. The head of the injection pump 12 needs to meet the water column pressure formed by the water jacket so that the cooling water can return to the water inlet end of the surface manifold 9. The displacement of the injection pump 12 meets the requirement of reducing the temperature of the synthesis gas.

[0037] Furthermore, the cooling water circulation mechanism also includes a continuous pipe 4, which is installed in the wellhead 8. One end of the continuous pipe 4 is connected to the water injection port of the ground manifold 9 through the wellhead bypass, and the other end extends to the bottom of the cavity. The water inlet port of the ground manifold 9 extends to the inside of the cavity near the wellhead 8.

[0038] Coiled tubing 4: The coiled tubing 4 is lowered to a position 5 to 10 meters away from the high-temperature packer. It can be made of stainless steel, chromium alloy, nickel-chromium alloy, monel and other materials. The inner diameter of the coiled tubing 4 needs to meet the flow rate of cooling water. The specific size is: 1 / 2-2 inches.

[0039] Furthermore, one end of the oil pipe 11 away from the wellhead 8 extends into the casing 5 and is connected to a screen pipe 2 . The screen pipe 2 extends to the coal seam 1 to prevent foreign matter (coal slag or other particulate matter) from entering the oil pipe 11 .

[0040] Sieve pipe 2: The material of the screen pipe 2 can be selected according to the composition of the synthesis gas and the production life of the underground gasifier 10. The selected material can meet the corrosion requirements of the synthesis gas. Specifically, stainless steel, chromium alloy, nickel-chromium alloy, monel and other materials can be selected; the inner diameter of the screen pipe 2 needs to reach the size required for the synthesis gas production, and the specific size is 5-95 / 8 inches. The aperture specification of the screen pipe 2 is 10-20mm, and the total hole area accounts for 15% to 30% of the surface area of ​​the pipe. Specifically, it can be configured according to the actual gas production requirements to ensure that the gas volume entering the wellbore meets the design requirements.

[0041] Before using the water jacket high temperature product well system, the following work needs to be done:

[0042] 1) It is necessary to simulate the gasification process of the underground gasifier in advance to obtain the process parameters such as synthesis gas pressure, composition, output, temperature, etc.

[0043] 2) After obtaining the gasification simulation parameters, determine the completion string size of the underground coal gasification furnace product well, and select the appropriate coiled tubing size through calculation;

[0044] 3) After determining the size of the completion string of the underground coal gasification furnace product well, select the specifications and models of the high-temperature packer according to the liquid column height of the cooling water in the product well, so that it can meet the corrosion damage of the synthetic gas to the packer under high temperature conditions;

[0045] 4) The sealing performance of the wellhead connection and valve selected for the product well must meet the corrosion and high temperature damage of the product well synthesis gas;

[0046] 5) Determine the displacement of the water injection pump according to the temperature and output of the synthesis gas that needs to be reduced, and determine the head of the water injection pump according to the cooling water column in the product well;

[0047] 6) Select the heat exchange capacity of the heat exchanger according to the cooling water temperature and flow rate of the surface manifold of the product well;

[0048] 7) Design the water storage capacity of the reservoir and the function of purifying circulating cooling water according to the production process requirements of the product well synthesis gas.

[0049] The above-mentioned embodiments only express several implementation methods of the utility model, and the description is relatively specific and detailed, but it cannot be understood as limiting the scope of the patent of the utility model. It should be pointed out that for ordinary technicians in this field, several modifications and improvements can be made without departing from the concept of the utility model, which all belong to the protection scope of the utility model.

Claims

1. A water-jacketed high-temperature product well system for underground coal gasification process, characterized in that: The invention comprises an underground gasifier (10), a product well, an oil pipe (11) and a casing (5), wherein the product well is opened on the ground and extends to the coal seam (1), the casing (5) is connected to the wellhead (8) of the product well and is sleeved on the outside of the oil pipe (11), the oil pipe (11) is erected at one end of the wellhead (8) and is suspended inside the product well, the underground gasifier (10) is located below the coal seam (1) and controls combustion of the coal seam (1), and the high-temperature synthesis gas generated by the combustion is transported to the wellhead (8) through the oil pipe (11), and the inner wall of the casing (5) at one end away from the wellhead (8) is connected to a high-temperature packer (3), the high-temperature packer (3) is sleeved on the surface of the oil pipe (11), and the upper surface of the high-temperature packer (3) forms a cavity with the inner wall of the casing (5) and the surface of the oil pipe (11); A cooling water circulation mechanism is provided on the ground, and the cooling water circulation mechanism comprises a water storage component, a ground manifold (9) and a heat exchanger (14). The water storage component and the heat exchanger (14) are connected via the ground manifold (9). The water storage component injects cooling water into the cavity via the water injection port of the ground manifold (9) to cool the high-temperature synthesis gas in the oil pipe (11). The water storage component guides the cooling water heated in the cavity from the water inlet port of the ground manifold (9) to the heat exchanger (14) for heat exchange and cooling, thereby circulating and injecting the cooling water into the cavity.

2. A water-jacketed high-temperature product well system for underground coal gasification process according to claim 1, characterized in that: The underground gasification furnace (10) uses injected oxidant to controllably burn the coal seam (1).

3. The water-jacketed high-temperature product well system for underground coal gasification process according to claim 1, characterized in that: A certain gap is reserved between the casing (5) and the inner wall of the production well, and cement is injected into the gap to form a cementing cement ring (6).

4. A water-jacketed high-temperature product well system for underground coal gasification process according to claim 1, characterized in that: The top of the sleeve (5) is connected with an airtight buckle for sealing the sleeve (5).

5. The water-jacketed high-temperature product well system for underground coal gasification process according to claim 1, characterized in that: The water storage component comprises a water injection pump (12), a water reservoir (13) and a valve (7); the water reservoir (13) and the water injection pump (12) are connected in sequence to a side of a heat exchanger (14) close to a water injection port of the ground manifold (9) through a ground manifold (9); the valve (7) is connected to a position of the ground manifold (9) close to the water injection port and is used to adjust the flow rate of cooling water.

6. A water-jacketed high-temperature product well system for underground coal gasification process according to claim 5, characterized in that: The cooling water circulation mechanism also includes a continuous pipe (4), which is installed in the wellhead (8), one end of which is connected to the water injection port of the surface manifold (9) through the wellhead bypass, and the other end of which extends to the bottom of the cavity, and the water inlet port of the surface manifold (9) extends to the inside of the cavity near the wellhead (8).

7. The water-jacketed high-temperature product well system for underground coal gasification process according to claim 1, characterized in that: One end of the oil pipe (11) away from the wellhead (8) extends into the casing (5) and is connected to a screen pipe (2); the screen pipe (2) extends to the coal seam (1) and is used to prevent foreign matter from entering the oil pipe (11).

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