An underground coal gasification string integrity simulation test device and test method

Abstract

The invention discloses a simulation test device and method for the integrity of an underground coal gasification string. The device mainly includes a load loading device, a test string, a temperature reduction device and a heating device. A tensile / compressive load is applied to the test string through the load loading device to test the strength of the test string; cooling circulating water is pumped into the outer wall of the test string through the temperature reduction device to adjust the temperature; the temperature inside the test string is adjusted through the heating device. The simulation test device and method for the integrity of the underground coal gasification string of the invention can simulate the change of the bearing capacity of the string under the ultra-high temperature environment of underground coal gasification, and can also simulate the change of the bearing capacity of the string for heavy oil fire flooding, providing a test evaluation means for the selection of oil casing in high-temperature wells. Through the invention, the change rules of the structural strength and sealing performance of the string under different downhole working conditions can be obtained, and effective string specifications and models can be selected according to the operating pressure and temperature range, effectively reducing the cost of coal gasification mining.

Description

Technical Field

[0001] The invention belongs to the technical field of oil production engineering, and relates to a simulation test device and a test method for the integrity of an underground coal gasification string. Background Art

[0002] The amount of coal gasifiable resources is huge. At present, the amount of coal resources with a burial depth of 1000 - 3000 m on land is 3.77×10¹² t. Calculated according to the gasification utilization rate of 40%, the methane resource amount equivalent to the calorific value is 272 - 332×10¹² m 3 , which is 3 times the amount of conventional natural gas resources. Calculated with a coal seam thickness of 5 m, the abundance of coal gasifiable resources is as high as 112×10⁸ m 3 / km 2 . Underground coal gasification is a process of carbonizing high-carbon resources into low-carbon or even carbon-free resources, which can realize the development concept of low-carbon and circular economy and accelerate the transformation of the energy structure.

[0003] At present, the basic theory of underground coal gasification is weak and the process technology is difficult. In the combustion area of the underground coal gasification cavity, the temperature is as high as 1200℃, and the temperature of the wellbore is 300 - 800℃. There are multi-component gases such as hydrogen, carbon dioxide, and water vapor in the wellbore, facing problems such as casing deformation, corrosion perforation, wellhead lifting, and annulus pressure. There is an urgent need for string integrity and control technology, to develop an indoor ultra-high temperature string simulation test device, obtain the change law of string performance at ultra-high temperature, effectively evaluate the physical performance of the string at ultra-high temperature and the actual service performance of the string after cooling.

[0004] The existing string integrity tests mainly rely on the ISO 13679 standard and stipulate that the maximum temperature is heated to 180℃. Combining with the needs of heavy oil thermal recovery, the SY / T 6952.3 standard proposes a test method for the performance of casing strings heated to 300℃. However, these standard heating methods mainly use heating tapes on the outer wall of the pipe or oil bath heating on the outer wall of the pipe (the oil bath can be heated to a maximum of 350℃), and cannot heat and cool synchronously, and can only be air-cooled or water-cooled after heating. This makes it impossible to obtain the performance of the casing string at temperatures above 500℃, and it is impossible to test the performance change of the casing string in high and low temperature cyclic alternation. In addition, when testing the sealing performance of the casing string according to the existing standard, a leak detection ring is installed at the joint connection, but when using a heating tape for heating, the leak detection ring cannot be installed because the heating tape is wound around the joint, which is likely to misjudge the sealing performance of the casing string. Summary of the Invention

[0005] The purpose of the invention is to solve the problem that the attenuation of the strength and sealing performance of the string in an ultra-high temperature environment cannot be evaluated in the prior art, and to provide a simulation test device and a test method for the integrity of an underground coal gasification string.

[0006] To achieve the above object, the invention adopts the following technical solutions:

[0007] A simulation test device for the integrity of an underground coal gasification string, comprising a load loading device, a cooling device and a heating device;

[0008] The load loading device includes an upper platform, a pressure cylinder, a lower platform and a base. The pressure cylinder is vertically arranged between the upper platform and the lower platform, and the base is arranged below the lower platform. The test string is installed between the upper platform and the lower platform through an upper flange and a lower flange;

[0009] The cooling device includes a double-layer axially hollow string sleeved on the outer periphery of the test string and a plurality of spray nozzles. The plurality of spray nozzles are arranged on the inner wall of the double-layer axially hollow string for spraying and cooling the test string;

[0010] The heating device includes an upper heating rod and a lower heating rod. The upper heating rod is installed in the test string through an upper flange, and the lower heating rod is installed in the test string through a lower flange.

[0011] A further improvement of the present invention lies in:

[0012] A coupling is arranged on the outer wall of the test string, and a leak detector is arranged on the coupling for detecting whether the test string leaks.

[0013] A temperature measuring instrument is arranged on the outer wall of the test string for recording the temperature of the outer wall of the test string.

[0014] A temperature and pressure gauge is arranged outside the test string, and the detection end extends to the inside of the test string for recording the internal temperature and pressure of the test string.

[0015] An inlet is opened above the double-layer axially hollow string, and a drain valve is arranged on the lower platform at the position between the test string and the cooling device.

[0016] A test method for a simulation test device for the integrity of an underground coal gasification string includes the following steps:

[0017] Step 1, start the load loading device, apply a tensile / compressive load to the test string, introduce nitrogen into the test string, record the internal pressure, tensile load and string deformation at this time on the load loading device, and at the same time record the temperature of the outer wall of the test string and the internal temperature by the temperature measuring instrument and the temperature and pressure gauge respectively, and detect whether the test string leaks by the leak detector;

[0018] Step 2, start the heating device, heat the upper heating rod and the lower heating rod to the set temperature at the same time, record the internal pressure, load and string deformation at this time on the load loading device, and at the same time record the temperature of the outer wall of the test string and the internal temperature by the temperature measuring instrument and the temperature and pressure gauge respectively, and detect whether the test string leaks by the leak detector;

[0019] Step 3: Start the cooling device, open the water inlet, pump in cooling water, spray and cool the test string, and at the same time open the drain valve. Record the internal pressure, load, and string deformation on the load loading device at this time. Meanwhile, use a thermometer and a temperature and pressure gauge to record the external wall temperature and internal temperature of the test string respectively, and use a leak detector to detect whether the test string leaks.

[0020] Step 4: Turn off the heating device, relieve the internal pressure and load through the load loading device, and turn off the cooling device after the temperature of the test string drops to room temperature. Analyze the variation laws of the structural strength and sealing performance of the test string with temperature based on the recorded internal pressure, load, string deformation, and temperature change data.

[0021] Steps 2 and 3 are carried out simultaneously.

[0022] Steps 2 and 3 are carried out alternately.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] The present invention discloses a simulation test device for the integrity of a coal underground gasification string, including a load loading device, a test string, a cooling device, and a heating device. The load loading device is used to apply tensile / compressive loads to the test string to test the strength of the test string; the cooling device is used to pump cooling circulating water to the outer wall of the test string to adjust the outer wall temperature of the test string; the heating device is used to adjust the internal temperature of the test string. The simulation test device for the integrity of a coal underground gasification string of the present invention can simulate the change of the load-bearing capacity of the string in the ultra-high temperature environment of coal underground gasification and the change of the casing string performance in high-low temperature cyclic alternation, and can also simulate the change of the load-bearing capacity of the string for heavy oil fire flooding, providing a test and evaluation method for the selection of high-temperature wellbore oil casings.

[0025] The present invention discloses a test method for a simulation test device for the integrity of a coal underground gasification string. The load loading device is used to apply tensile / compressive loads to the test string to test the strength of the test string; the cooling device is used to pump cooling circulating water to the outer wall of the test string to adjust the outer wall temperature of the test string; the heating device is used to adjust the internal temperature of the test string. Through the present invention, the variation laws of the structural strength and sealing performance of the string under different downhole working conditions can be obtained, the attenuation law of the string performance with the increase of temperature and the recovery value of the string performance after cooling can be determined, and an effective string specification model can be selected according to the operating pressure and temperature range, effectively reducing the coal gasification mining cost. Description of the Drawings

[0026] Figure 1 It is a structural schematic diagram of the simulation test device for the integrity of a coal underground gasification string of the present invention;

[0027] Figure 2 is Figure 1Cross-sectional view along the A-A direction.

[0028] Wherein: 1 - upper flange; 2 - thermometer; 3 - leak detector; 4 - upper platform; 5 - cooling device; 6 - coupling; 7 - pressure cylinder; 8 - test string; 9 - lower platform; 10 - base; 11 - drain valve; 12 - lower flange; 13 - lower heating rod; 14 - upper heating rod; 15 - water inlet; 16 - temperature and pressure gauge. Specific implementation mode

[0029] In order to enable those skilled in the art to better understand the solution of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of the embodiments, and are not intended to limit the scope of the present invention disclosure. In addition, in the following description, the descriptions of well-known structures and technologies are omitted to avoid unnecessarily confusing the concepts disclosed in the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the scope of protection of the present invention.

[0030] The present invention will be further described in detail below with reference to the accompanying drawings:

[0031] See Figure 1 and Figure 2 The present invention discloses a simulation test device for the integrity of an underground coal gasification string, including a load loading device, a cooling device 5 and a heating device; the load loading device includes an upper platform 4, and the lower part of the upper platform 4 is connected to a lower platform 9 through two vertically arranged pressure cylinders 7. Two bases 10 are arranged below the lower platform 9, and the test string 8 is installed between the upper platform 4 and the lower platform 9 through an upper flange 1 and a lower flange 12; the cooling device 5 includes a double-layer axially hollow pipe column sleeved on the outer periphery of the test string 8 and a plurality of spray nozzles. The plurality of spray nozzles are arranged on the inner wall of the double-layer axially hollow pipe column for spraying and cooling the test string 8; a water inlet 15 is opened above the double-layer axially hollow pipe column, and a drain valve 11 is arranged on the lower platform 9 corresponding to the position between the test string 8 and the cooling device 5. The heating device includes an upper heating rod 14 and a lower heating rod 13, and the upper heating rod 14 and the lower heating rod 13 are respectively screwed into the test string 8 through the upper platform 4 and the lower platform 9.

[0032] A coupling 6 is arranged on the outer wall of the test string 8, and a leak detector 3 is arranged on the coupling 6 for detecting whether the test string 8 leaks. A thermometer 2 is arranged on the outer wall of the test string 8 for recording the temperature of the outer wall of the test string 8. A temperature and pressure gauge 16 is arranged inside the test string 8 and extends to the outside of the test string 8 for recording the temperature and pressure inside the test string 8.

[0033] The invention discloses a test method for an integrity simulation test device of an underground coal gasification string, which comprises the following steps: Step 1, start the load loading device, apply tensile / compressive load to the test string 8, introduce nitrogen into the test string 8, record the internal pressure, tensile load and string deformation amount on the load loading device at this time, simultaneously record the outer wall temperature and internal temperature of the test string 8 by the temperature measuring instrument 2 and the temperature and pressure gauge 16 respectively, and detect whether the test string leaks by the leak detector 3; Step 2, start the heating device, heat the upper heating rod 14 and the lower heating rod 13 to the set temperature T simultaneously, record the internal pressure, load and string deformation amount on the load loading device at this time, simultaneously record the outer wall temperature and internal temperature of the test string 8 by the temperature measuring instrument 2 and the temperature and pressure gauge 16 respectively, and detect whether the test string leaks by the leak detector 3; Step 3, start the cooling device 5, open the water inlet 15, pump in cooling water, spray and cool the test string 8, simultaneously open the drain valve 11, record the internal pressure, load and string deformation amount on the load loading device at this time, simultaneously record the outer wall temperature and internal temperature of the test string 8 by the temperature measuring instrument 2 and the temperature and pressure gauge 16 respectively, and detect whether the test string leaks by the leak detector 3; Step 4, turn off the heating device, relieve the internal pressure and load through the load loading device, and turn off the cooling device 5 after the temperature of the test string 8 drops to room temperature; Analyze the variation law of the structural strength and sealing performance of the test string 8 with temperature according to the recorded internal pressure, load, string deformation amount and temperature change data. Step 2 and Step 3 can be carried out alternately or step by step.

[0034] The integrity simulation test device and test method for the underground coal gasification string provided by the invention can simulate the change of the load-bearing capacity of the string under the ultra-high temperature environment of underground coal gasification, and can also simulate the change of the load-bearing capacity of the string for heavy oil fire flooding, providing a test and evaluation means for the selection of oil casing in high-temperature wells. Through the invention, the variation law of the structural strength and sealing performance of the string under different downhole working conditions can be obtained, and the effective string specifications and models can be selected according to the operating pressure and temperature range, effectively reducing the coal gasification mining cost.

[0035] The above content is only to illustrate the technical idea of the invention, and the protection scope of the invention cannot be limited thereby. Any modification made on the basis of the technical solution according to the technical idea proposed by the invention falls within the protection scope of the claims of the invention.

Claims

1. An integrity simulation test device for underground coal gasification pipe string, characterized in that It includes a load loading device, a cooling device (5) and a heating device; The load loading device includes an upper platform (4), a pressure cylinder (7), a lower platform (9) and a base (10). The pressure cylinder (7) is vertically arranged between the upper platform (4) and the lower platform (9), and the base (10) is arranged below the lower platform (9). The test string (8) is installed between the upper platform (4) and the lower platform (9) through an upper flange (1) and a lower flange (12); The cooling device (5) includes a double-layer axially hollow pipe column sleeved on the outer periphery of the test string (8) and a plurality of spray nozzles. The plurality of spray nozzles are arranged on the inner wall of the double-layer axially hollow pipe column for spraying and cooling the test string (8); An inlet (15) is opened above the double-layer axially hollow pipe column, and a drain valve (11) is arranged on the lower platform (9) at the position between the test string (8) and the cooling device (5); The heating device includes an upper heating rod (14) and a lower heating rod (13). The upper heating rod (14) is installed in the test string (8) through the upper flange (1), and the lower heating rod (13) is installed in the test string (8) through the lower flange (12); A coupling (6) is arranged on the outer wall of the test string (8), and a leak detector (3) is arranged on the coupling (6) for detecting whether the test string (8) leaks; A temperature measuring instrument (2) is arranged on the outer wall of the test string (8) for recording the outer wall temperature of the test string (8); A temperature and pressure gauge (16) is arranged outside the test string (8), and the detection end extends to the inner side of the test string (8) for recording the internal temperature and pressure of the test string (8).

2. A test method for the test device of the integrity simulation of an underground coal gasification string as described in claim 1, characterized in that, It includes the following steps: Step 1: Start the load loading device, apply a tensile / compressive load to the test string (8), introduce nitrogen into the test string (8), record the internal pressure, tensile load and pipe string deformation at this time on the load loading device. At the same time, the outer wall temperature and internal temperature of the test string (8) are respectively recorded by the temperature measuring instrument (2) and the temperature and pressure gauge (16), and the leak detector (3) is used to detect whether the test string (8) leaks; Step 2: Start the heating device, heat the upper heating rod (14) and the lower heating rod (13) to the set temperature at the same time, record the internal pressure, load and pipe string deformation at this time on the load loading device. At the same time, the outer wall temperature and internal temperature of the test string (8) are respectively recorded by the temperature measuring instrument (2) and the temperature and pressure gauge (16), and the leak detector (3) is used to detect whether the test string (8) leaks; Step 3: Start the cooling device (5), open the inlet (15), pump in cooling water, spray and cool the test string (8). At the same time, open the drain valve (11), record the internal pressure, load and pipe string deformation at this time on the load loading device. At the same time, the outer wall temperature and internal temperature of the test string (8) are respectively recorded by the temperature measuring instrument (2) and the temperature and pressure gauge (16), and the leak detector (3) is used to detect whether the test string (8) leaks; Step 4: Turn off the heating device, unload the internal pressure and load through the load loading device, and turn off the temperature reduction device (5) after the temperature of the test pipe string (8) drops to room temperature; analyze the variation law of the structural strength and sealing performance of the test pipe string (8) with temperature based on the recorded data of internal pressure, load, pipe string deformation, and temperature change.

3. A test method for the simulation test device of the integrity of the underground coal gasification string as described in claim 2, characterized in that, The above-mentioned Step 2 and Step 3 are carried out simultaneously.

4. A test method for the test device of the integrity of the underground coal gasification string as described in claim 2, characterized in that, The above-mentioned Step 2 and Step 3 are carried out alternately.

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