Multi-stage separation degassing coal series gas testing device and testing method

Abstract

The invention belongs to the technical field of coal series gas exploration and development, and particularly relates to a multistage separation degassing coal series gas testing device and testing method.The multistage separation degassing coal series gas testing device comprises a drilling fluid pumping system and a multistage degassing system connected with the drilling fluid pumping system, and the multistage degassing system is connected with a testing control assembly; the multi-stage degassing system comprises a drilling fluid suction pipeline connected with the drilling fluid pumping system, a first slurry pump, a drilling fluid outflow pipeline, a multi-stage separation degasser and a drilling fluid discharge pipeline, and the multi-stage separation degasser comprises a first-stage separation device, a second-stage separation device and a third-stage separation device; according to the invention, the problems of test result hysteresis caused by flowback of the drilling fluid along a relatively long annular pipeline, non-equivalence of the gas content of the tested coal measure strata caused by fluctuation of the flowback amount of the drilling fluid, relatively large test result error caused by dissipation of dissolved gas and low degassing efficiency and the like can be solved; the method is expected to provide a basis for accurately identifying a gas-bearing stratum in a coal-series gas exploration and development process.

Description

Technical Field

[0001] The present invention belongs to the technical field of coal-measure gas exploration and development, and in particular relates to a coal-measure gas testing device and a testing method with multi-stage separation and degassing. Background Art

[0002] As a clean, low-carbon, unconventional natural gas resource, coal-measure gas (CBM) can be efficiently explored and developed to promote the development of renewable energy, thereby accelerating my country's transition to a low-carbon energy system. Coal-measure gas primarily includes coalbed methane (CBM), tight sandstone gas, shale gas, carbonate gas, and natural gas hydrates from coal-derived sources. Due to its diverse source base, accurate identification of oil and gas-bearing formations is crucial during exploration and development. Currently, gas content testing in coal-measure formations is commonly performed using methods such as pressure-maintained coring, well logging inversion prediction, and gas logging.

[0003] Gas content testing during drilling coring involves using a pressure-maintained coring tool to sample coal-bearing formations during drilling. The core is then sealed in a pressure-maintained inner cylinder. The gas content is then determined through indoor gas content testing to determine the gas content of the corresponding layer. However, coal-bearing formations in my country are often characterized by numerous vertical layers and thin thicknesses, making the success rate of coring during drilling often low. Well logging inversion prediction involves identifying the lithology and thickness of coal-bearing formations through geophysical logging techniques. The gas content of coal-bearing formations is then predicted by inverting the response of well logging curves such as density, spontaneous potential, acoustic transit time, natural gamma, and compensated neutrons in gas-bearing zones. However, due to noise in geophysical signals, formation heterogeneity, and groundwater conditions, the accuracy of predictions is often limited. Gas logging involves continuously testing and analyzing the hydrocarbon content in the flowback drilling fluid during drilling to determine the gas content of coal-bearing formations. Gas logging has advantages such as continuity and sensitivity, and is commonly used in coal-bearing gas exploration and development. However, as exploration depth increases, drilling fluid often needs to be returned to the surface through a longer annular pipeline, and the return flow rate fluctuates greatly, resulting in significant lag and asymmetry in the test information. At the same time, due to changes in the temperature and pressure environment during the drilling return flow, some gas escapes, and the degassing efficiency of the drilling fluid in the gas logging degasser is limited, resulting in large errors in the test results. To make the gas logging test results more accurate, we designed a coal-bearing gas logging device with multi-stage separation and degassing, which improves the accuracy of the degassing test in the degasser. The test drilling fluid volume can be adjusted according to the return fluid volume and can reflect the actual return flow layer based on information such as the wellbore diameter, drilling footage, and drilling fluid injection volume, achieving continuous, stable, and accurate gas logging testing. Summary of the Invention

[0004] The purpose of the present invention is to provide a coal-measure gas gas testing device and testing method with multi-stage separation and degassing, which addresses the problems of hysteresis, asymmetry, and low accuracy of gas logging test results during coal-measure gas exploration and development. By developing a coal-measure gas gas testing device and method with multi-stage separation and degassing, it is possible to solve problems such as hysteresis of test results caused by drilling fluid backflow along a long annular pipeline, asymmetry of gas content in the measured coal-measure formations caused by fluctuations in drilling fluid backflow volume, and large errors in test results due to dissolved gas escape and low degassing efficiency, thereby providing a basis for accurately identifying gas-bearing formations during coal-measure gas exploration and development.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is:

[0006] A coal gas testing device with multi-stage separation and degassing, comprising a drilling fluid pumping system, a multi-stage degassing system connected to the drilling fluid pumping system, and the multi-stage degassing system is connected to a test control component; the multi-stage degassing system comprises a drilling fluid suction pipeline connected to the drilling fluid pumping system, a first mud pump, a drilling fluid outflow pipeline, a multi-stage separation degasser and a drilling fluid discharge pipeline, the multi-stage separation degasser comprising a first-stage separation device, a second-stage separation device and a third-stage separation device, each stage of the separation device is provided with a separation device housing, a vertical transmission rod is provided in the separation device housing, the top of the transmission rod extends out of the separation device housing and is controlled to rotate by a motor, a coupling is provided in the middle of the transmission rod, a rotating blade is provided at the lower part of the rotating rod, a liquid inlet connected to the drilling fluid outflow pipeline is provided at the bottom of the separation device housing, a gas separation output pipeline is provided at the upper part of the separation device housing, and a drilling fluid separation output pipeline connected to the next stage of the separation device is provided at the middle and lower part of the separation device housing.

[0007] Furthermore, each separation device housing is provided with an electrode output control valve at the inlet of the drilling fluid separation output pipeline, the rotation speed of the first-stage separation device is less than the rotation speed of the second-stage separation device, which is less than the rotation speed of the third-stage separation device; the gas output pipeline of the multi-stage separation degasser is connected to the test control component.

[0008] Furthermore, the drilling fluid pumping system includes a drilling rig, a drill pipe connected to the drilling rig, and a drill bit at the end of the drill pipe. The drilling rig pumps the drilling fluid from the mud pool into the drill pipe through a pipeline via a second mud pump, and a drilling fluid injection flowmeter is provided on the pipeline; a drilling fluid return pipe is also provided at the wellhead of the drilling rig, and a control valve and a drilling fluid return flowmeter are provided on the drilling fluid return pipe. The drilling fluid return pipe is connected to the mud pool, and the drilling fluid return pipe bypass is connected to the drilling fluid suction pipeline.

[0009] Furthermore, the test control component includes a gas chromatograph connected to the gas separation output pipeline of the multi-stage separation degasser, and also includes a control system, which is connected to the multi-stage separation degasser control pipeline and the first mud pump; the multi-stage separation degasser is also provided with a temperature control system.

[0010] A method for testing a coal-based gas testing device with multi-stage separation and degassing, comprising the following steps:

[0011] S1. During drilling, the drilling fluid injection flowmeter records the drilling fluid injection volume Q1 and calculates the gas logging layer H;

[0012] S2. When the drilling fluid starts to flow back, the time t0 is recorded, and the drilling fluid flowback flowmeter records the drilling fluid flowback volume Q2;

[0013] S3. Based on the drilling fluid flowback volume Q2, the control system regulates the first mud pump of the gas logging system to pump the mud into the multi-stage separation degasser at a pumping volume of 0.1Q2;

[0014] S4. According to the density of the drilling fluid, the control system regulates the motor speed of the three-stage separation device to separate the drilling fluid gas and liquid;

[0015] S5. The drilling fluid is subjected to gas-liquid separation, and the three-stage separated gas is tested by gas chromatography to determine the alkane gas content;

[0016] S6. After testing, the drilling fluid is discharged into the mud pool through the drilling fluid discharge pipeline.

[0017] This process is based on the drilling and completion design and tests the gas logging intervals specified in the design.

[0018] The calculation method of gas logging layer is as follows:

[0019] Assuming that the drilling depth at time t is h, the gas logging layer at time t+Δt is H.

[0020]

[0021] Where H is the gas logging layer, m; Q1 is the drilling fluid injection volume, m 3 ; V1 is the downhole drill volume, m 3 ; V2 is the drilling fluid loss, m 3 ; r is the well diameter, m; v t is the drilling speed during the Δt period, min / m.

[0022] The motor speed of the three-stage separation device is set according to the drilling fluid density:

[0023] Table 1 Relationship between drilling fluid density and separation device speed

[0024]

[0025] The advantages of the present invention are:

[0026] 1. The coal-measure gas logging device with multi-stage separation and degassing provided by the present invention achieves multi-stage separation of drilling fluid through the centrifugal effect of different rotational speeds, thereby solving the problem of low test accuracy caused by low degassing efficiency in gas logging.

[0027] 2. By measuring and controlling the injection volume, flowback volume and test pumping volume of drilling fluid, the gas logging layer and the gas content of the corresponding layer are determined, solving the problems of lag and asymmetry of gas logging results in conventional gas logging. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a structural schematic diagram of the present invention.

[0029] Figure 2 It is a structural diagram of the multi-stage degassing system and test control system in the present invention. DETAILED DESCRIPTION

[0030] like Figure 1-2As shown, a multi-stage separation and degassing coal-measure gas testing device includes a drilling fluid pumping system, the drilling fluid pumping system includes a drilling rig 1, a drill pipe 2 connected to the drilling rig, and a drill bit 9 at the end of the drill pipe. The drilling rig pumps drilling fluid from a mud pool 12 into the drill pipe through a pipeline via a second mud pump 13, and a drilling fluid injection flowmeter 14 is provided on the pipeline; a drilling fluid return pipe 10 is also provided at the wellhead 7 of the drilling rig, and a control valve 4 and a drilling fluid return flowmeter 5 are provided on the drilling fluid return pipe. The drilling fluid return pipe is connected to the mud pool, and the drilling fluid return pipe bypass is connected to the drilling fluid suction pipeline 61 of the gas logging system 6; the gas logging system includes a multi-stage separation and degassing system and a test control group The front end of the multi-stage degassing system is connected to the drilling fluid pumping system, and the rear end is connected to the test control component; the test control component includes a gas chromatograph connected to the gas separation output pipeline 616 of the multi-stage separation degasser 64, and also includes a control system 66, the control system is connected to the multi-stage separation degasser control pipeline 619 and the first mud pump control pipeline 620; the multi-stage separation degasser is also provided with a temperature control system 621; the drilling fluid pumping system is mainly used to control the drilling fluid test volume according to the drilling fluid return volume, and record the drilling fluid injection volume, return volume, test volume and other data; the multi-stage degassing system is mainly used to separate the hydrocarbon components in the drilling fluid; the test control ... Used to operate, control, monitor and record the test data of each phase during the test and the content of hydrocarbon components in the drilling fluid after test separation; the multi-stage degassing system includes a drilling fluid suction pipeline 61 connected to the drilling fluid pumping system, a first mud pump 62, a drilling fluid outflow pipeline 63, a multi-stage separation degasser 64 and a drilling fluid discharge pipeline 11, and the drilling fluid discharge pipeline is arranged at the end of the three-stage separation device. The multi-stage separation degasser includes a first-stage separation device 67, a second-stage separation device 68 and a third-stage separation device 69. Each stage of the separation device is provided with a separation device housing 610, and a vertical transmission rod 612 is provided in the separation device housing, and the top of the transmission rod extends out of the separation device The shell is controlled to rotate by a motor 611, a coupling 613 is provided in the middle of the transmission rod, a rotating blade 614 is provided at the lower part of the rotating rod, a liquid inlet connected to the drilling fluid outflow pipeline is provided at the bottom of the separation device shell, a gas separation output pipeline 616 is provided at the upper part of the separation device shell, and a drilling fluid separation output pipeline 617 connected to the next-stage separation device is provided at the middle and lower part of the separation device shell; each separation device shell is provided with an electrode output control valve 615 at the inlet of the drilling fluid separation output pipeline, the rotation speed of the first-stage separation device is less than that of the second-stage separation device and less than that of the third-stage separation device; the gas output pipeline 616 of the multi-stage separation degasser is connected to the test control component.

[0031] A method for testing a coal-based gas testing device with multi-stage separation and degassing, comprising the following steps:

[0032] S1. During drilling, the drilling fluid injection flowmeter records the drilling fluid injection volume Q1 and calculates the gas logging layer H;

[0033] S2. When the drilling fluid starts to flow back, the time t0 is recorded, and the drilling fluid flowback flowmeter records the drilling fluid flowback volume Q2;

[0034] S3. Based on the drilling fluid flowback volume Q2, the control system regulates the first mud pump of the gas logging system to pump the mud into the multi-stage separation degasser at a pumping volume of 0.1Q2;

[0035] S4. According to the density of the drilling fluid, the control system regulates the motor speed of the three-stage separation device to separate the drilling fluid gas and liquid;

[0036] S5. The drilling fluid is subjected to gas-liquid separation, and the three-stage separated gas is tested by gas chromatography to determine the alkane gas content;

[0037] S6. After testing, the drilling fluid is discharged into the mud pool through the drilling fluid discharge pipeline.

[0038] This process is based on the drilling and completion design and tests the gas logging intervals specified in the design.

[0039] The calculation method of gas logging layer is as follows:

[0040] Assuming that the drilling depth at time t is h, the gas logging layer at time t+Δt is H.

[0041]

[0042] Where H is the gas logging layer, m; Q1 is the drilling fluid injection volume, m 3 ; V1 is the downhole drill volume, m 3 ; V2 is the drilling fluid loss, m 3 ; r is the well diameter, m; v t is the drilling speed during the Δt period, min / m.

[0043] In specific use, during the drilling construction of the exploration well, the drill pipe passes through the overburden 15, the bedrock layer 16, and the coal-bearing stratum 17 in sequence. During this process, the drilling fluid is pumped from the mud pool 12 into the drilling rig 1 through the drill pipe 2 by the second mud pump 13 and pumped into the drilling layer, wherein the drilling fluid injection volume is tested and recorded by the drilling fluid injection flowmeter 14. The drilling fluid is discharged from the drilling layer through the wellbore annulus to the wellhead 7 and flows into the mud pool 12 through the drilling fluid return pipe 10, wherein the drilling fluid return volume is tested and recorded by the drilling fluid return flowmeter 5. The measurement results of the drilling fluid injection volume and the drilling fluid return volume are respectively recorded in the test control component; during gas testing, the drilling fluid suction pipeline 61 is connected to the wellbore annulus 61. Figure 1In the drilling fluid flowback pipeline 10, a control system 66 regulates the power of the first mud pump 62 in real time based on the drilling fluid flowback volume via the first mud pump control line 620 to maintain a constant ratio between the drilling fluid test flow rate and the drilling fluid flowback volume. The test drilling fluid is pumped by the first mud pump 62 via the drilling fluid outflow line 63 into the multi-stage separation degasser 64. The multi-stage separation degasser comprises a primary separation unit, a secondary separation unit, and a tertiary separation unit. Within the primary separation unit, a motor drives a transmission rod, which, through a coupling, causes the rotating blades to rotate, centrifugally separating the pumped drilling fluid. Alkane gas is discharged through the gas separation output line. When the drilling fluid within the separation unit reaches a certain height, the electrode output control valve is triggered, opening the valve and allowing the drilling fluid to flow through the drilling fluid separation output line to the next separation unit. After final separation, the drilling fluid is discharged through the drilling fluid discharge line. The three-stage separation units have the same structure. The control system controls the motors of each of the three separation units via the multi-stage separation degasser control line, controlling the centrifugal separation speed. During the test, the temperature control system of the multi-stage separation degasser was used to adjust the ambient temperature of the multi-stage separation degasser to help separate the heavy alkane gas. The gas separation output pipeline was connected to the gas chromatograph, and the drilling fluid discharge pipeline was connected to the Figure 1 The drilling fluid discharge pipeline is tested, and after the test, the drilling fluid is discharged into the mud pool through the pipeline; the alkane gas in the drilling fluid separated by the multi-stage separation degasser is input into the gas chromatograph through the gas separation output pipeline to test various alkane components and contents, and the test results are recorded in the control system.

[0044] Application Examples

[0045] The testing device and method designed in the present invention have been used in the PB13-C4 well in the Pingdingshan mining area. Drilling construction of the well began on February 25, 2025, and was completed on March 6, 2025. The total footage of the well was 990.00 m, the drilling cycle was 24.25 days, and the completion cycle was 29.5 days. During the logging work of the well, the working performance of the various engineering parameter sensors was stable, and the timely monitoring function of the integrated logging instrument was fully utilized, so that the entire drilling operation was under the all-weather monitoring of the logging instrument. The gas logger set the instrument parameters more reasonably and in real time, and used the advanced detection function of the instrument to record the engineering parameter data in a timely and accurate manner. A total of 15 layers of gas logging anomalies were found in the entire section of this well. The test results are shown in Table 2.

[0046] Table 2 Statistics of gas testing results of well PB13-C4

[0047]

[0048] The entire section of Well PB13-C4 was drilled and cored. After the cores were taken out, they were soaked in clean water. Some of the cores showed bubble reactions after soaking in water, and the formation sections corresponding to the bubble reactions all had gas logging indications. Conventional gas logging and mud logging test equipment was used to perform gas logging in adjacent exploration wells in the same mining area. Some of the cores showed bubble reactions after soaking, but there was no gas logging indication in the conventional gas logging results, proving that the gas logging results using the testing device and method of the present invention are more accurate than those using conventional gas logging and mud logging.

Claims

1. A coal-based gas testing device with multi-stage separation and degassing, characterized by: The invention comprises a drilling fluid pumping system, a multi-stage degassing system connected to the drilling fluid pumping system, and the multi-stage degassing system is connected to the test control component; the multi-stage degassing system comprises a drilling fluid suction pipeline connected to the drilling fluid pumping system, a first mud pump, a drilling fluid outflow pipeline, a multi-stage separation degasser and a drilling fluid discharge pipeline, the multi-stage separation degasser comprises a first-stage separation device, a second-stage separation device and a third-stage separation device, each stage of the separation device is provided with a separation device shell, a vertical transmission rod is provided in the separation device shell, the top of the transmission rod extends out of the separation device shell and is controlled to rotate by a motor, a coupling is provided in the middle of the transmission rod, a rotating blade is provided at the lower part of the rotating rod, a liquid inlet connected to the drilling fluid outflow pipeline is provided at the bottom of the separation device shell, a gas separation output pipeline is provided at the upper part of the separation device shell, and a drilling fluid separation output pipeline connected to the next stage separation device is provided at the middle and lower part of the separation device shell.

2. The coal-based gas measurement device with multi-stage separation and degassing according to claim 1, characterized in that: Each separation device shell is equipped with an electrode output control valve at the inlet of the drilling fluid separation output pipeline. The rotation speed of the first-stage separation device is smaller than that of the second-stage separation device and smaller than that of the third-stage separation device; the gas output pipeline of the multi-stage separation degasser is connected to the test control component.

3. The coal-based gas measurement device with multi-stage separation and degassing according to claim 1, characterized in that: The drilling fluid pumping system includes a drilling rig, a drill pipe connected to the drilling rig, and a drill bit at the end of the drill pipe. The drilling rig pumps drilling fluid from a mud pool into the drill pipe through a pipeline via a second mud pump, and a drilling fluid injection flowmeter is provided on the pipeline; a drilling fluid return pipe is also provided at the wellhead of the drilling rig, and a control valve and a drilling fluid return flowmeter are provided on the drilling fluid return pipe. The drilling fluid return pipe is connected to the mud pool, and a drilling fluid return pipe bypass is connected to the drilling fluid suction pipeline.

4. The coal-based gas measurement device with multi-stage separation and degassing according to claim 1, characterized in that: The test control assembly includes a gas chromatograph connected to the gas separation output pipeline of the multi-stage separation degasser, and also includes a control system, which is connected to the multi-stage separation degasser control pipeline and the first mud pump; the multi-stage separation degasser is also provided with a temperature control system.

5. The method for testing a coal-based gas testing device with multi-stage separation and degassing according to any one of claims 1 to 4, characterized in that: The following steps are involved: S1. During drilling, the drilling fluid injection flowmeter records the drilling fluid injection volume Q1 and calculates the gas logging layer H; S2. When the drilling fluid starts to flow back, the time t0 is recorded, and the drilling fluid flowback flowmeter records the drilling fluid flowback volume Q2; S3. Based on the drilling fluid flowback volume Q2, the control system regulates the first mud pump of the gas logging system to pump the mud into the multi-stage separation degasser at a pumping volume of 0.1Q2; S4. According to the density of the drilling fluid, the control system regulates the motor speed of the three-stage separation device to separate the drilling fluid gas and liquid; S5. The drilling fluid is subjected to gas-liquid separation, and the three-stage separated gas is tested by gas chromatography to determine the alkane gas content; S6. After testing, the drilling fluid is discharged into the mud pool through the drilling fluid discharge pipeline.

6. The method according to claim 5, wherein: The calculation of gas logging layer is as follows: Assuming that the drilling depth at time t is h, the gas logging layer at time t+Δt is H. Where H is the gas logging layer, m; Q1 is the drilling fluid injection volume, m 3 ; V1 is the downhole drill volume, m 3 ; V2 is the drilling fluid loss, m 3 ; r is the well diameter, m; v t is the drilling speed during the Δt period, min / m.

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