Multi-stage separation and degassing coal measure gas measuring device and testing method

Abstract

The present application belongs to the technical field of coal measures gas exploration and development, and particularly relates to a multi-stage separation degassing coal measures gas testing device and testing method, which comprises a drilling fluid pumping system, a multi-stage degassing system connected with the drilling fluid pumping system, and a testing control assembly connected with the multi-stage degassing system; the multi-stage degassing system comprises a drilling fluid suction pipeline connected with 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 separation device, a second separation device, and a third separation device; the present application can solve the problems of test result hysteresis caused by the return flow of drilling fluid along a long annular pipeline, the inequality of measured coal measures formation gas content caused by the fluctuation of drilling fluid return flow, and the large test result error caused by the low degassing efficiency of dissolved gas, so as to provide a basis for accurately identifying gas-bearing formations during the exploration and development of coal measures gas.

Description

Technical Field

[0001] This invention belongs to the field of coalbed methane exploration and development technology, and particularly relates to a coalbed methane gas measuring device and testing method with multi-stage separation and degassing. Background Technology

[0002] Coal-series gas, as a clean and low-carbon unconventional natural gas resource, can promote the development of renewable energy through efficient exploration and development, thereby helping my country's energy sector rapidly transition towards low-carbon development. Coal-series gas mainly includes coalbed methane, coal-series tight sandstone gas, coal-series shale gas, coal-series carbonate rock gas, and natural gas hydrates from coal-type gas sources. Due to its diverse gas source characteristics, accurately identifying oil and gas-bearing strata is crucial during exploration and development. Currently, methods such as well drilling with pressure-maintaining coring for gas-bearing testing, well logging inversion prediction, and gas logging are commonly used to test the gas-bearing capacity of coal-series strata.

[0003] Gas content testing via core sampling during drilling involves using a core sampling tool to extract cores from the corresponding coal-bearing formation during the drilling process. The extracted cores are sealed in a pressure-holding inner cylinder, and then the gas content is measured in a laboratory to determine the gas content of the corresponding strata. However, coal-bearing formations in my country are often characterized by numerous vertical layers and thin thickness, resulting in a low success rate for core sampling during drilling. Well logging inversion prediction involves identifying the lithology and thickness of coal-bearing formations using geophysical logging methods, and then predicting the gas content of the coal-bearing formations by inverting the responses of logging curves such as density, spontaneous potential, sonic transit time, natural gamma, and compensated neutron in the gas-bearing layer. However, due to factors such as noise in geophysical signals, formation heterogeneity, and groundwater environment, the accuracy of the prediction results is often unsatisfactory. Gas logging refers to determining the gas content of coal-bearing formations by continuously testing and analyzing the hydrocarbon component content in the flowback drilling fluid during the drilling process. Gas logging offers advantages such as continuity and sensitivity, making it commonly used in coalbed methane exploration and development. However, as exploration depth increases, drilling fluid often needs to be flowed back to the surface through long annular pipelines, and the flowback volume fluctuates significantly, resulting in substantial lag and asymmetry in the test information. Furthermore, changes in temperature and pressure during the flowback process cause some gas to escape, and the limited degassing efficiency of the drilling fluid in the gas logging degasser often leads to large errors in the test results. To improve the accuracy of gas logging test results, we designed a multi-stage separation and degassing coalbed methane gas logging device. This device improves the accuracy of degassing tests, and the tested drilling fluid volume can be adjusted according to the flowback fluid volume while also reflecting the true flowback layer based on information such as well diameter, drilling footage, and drilling fluid injection volume, achieving continuous, stable, and accurate gas logging testing. Summary of the Invention

[0004] The purpose of this invention is to provide a multi-stage separation and degassing coalbed methane gas testing device and method, addressing the problems of lag, inconsistency, and low accuracy in gas logging test results during coalbed methane exploration and development. By developing a multi-stage separation and degassing coalbed methane gas testing device and method, it is possible to solve problems such as the lag in test results caused by drilling fluid flowback along long annular pipelines, the inconsistency in measured gas content of coalbed methane formations due to fluctuations in drilling fluid flowback volume, and the large errors in test results caused by dissolved gas escape and low degassing efficiency. This aims to provide a basis for accurately identifying gas-bearing strata during coalbed methane exploration and development.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] A multi-stage separation and degassing coalbed methane gas detection device includes a drilling fluid pump suction system and a multi-stage degassing system connected to the drilling fluid pump suction system. The multi-stage degassing system is connected to a test control component. The multi-stage degassing system includes a drilling fluid suction pipeline connected to the drilling fluid pump suction 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 includes a primary separation device, a secondary separation device, and a tertiary separation device. Each separation device has a separation device housing. A vertical transmission rod is installed inside the separation device housing. The top of the transmission rod extends out of the separation device housing and is rotated by a motor. A coupling is installed in the middle of the transmission rod. Rotating blades are installed at the lower part of the rotating rod. An inlet connected to the drilling fluid outflow pipeline is installed at the bottom of the separation device housing. A gas separation output pipeline is installed at the top of the separation device housing. A drilling fluid separation output pipeline connected to the next stage separation device is installed in the lower middle part of the separation device housing.

[0007] Furthermore, each separation unit has an electrode output control valve at the inlet of the drilling fluid separation output pipeline. The rotation speed of the first-stage separation unit is less than that of the second-stage separation unit, which is less than that of the third-stage separation unit. 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 drilling fluid from the mud pit into the drill pipe through a pipeline via a second mud pump. A drilling fluid injection flow meter is installed on the pipeline. A drilling fluid return pipe is also installed at the wellhead of the drilling rig. The drilling fluid return pipe is equipped with a control valve and a drilling fluid return flow meter. The drilling fluid return pipe is connected to the mud pit, and a bypass of the drilling fluid return pipe 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 separator degasser, and a control system connected to the control pipeline of the multi-stage separator degasser and the first mud pump; the multi-stage separator degasser is also equipped with a temperature control system.

[0010] A testing method for a multi-stage separation and degassing coalbed methane gas measuring device includes the following steps:

[0011] S1. During the drilling process, the drilling fluid injection flow meter records the drilling fluid injection volume Q1 and calculates the gas-measuring layer H;

[0012] S2. Record time t0 when drilling fluid begins to flow back, and record drilling fluid flow back volume Q2 by drilling fluid flow back meter;

[0013] S3. Based on the drilling fluid return rate Q2, the control system adjusts the first mud pump of the gas measurement system to pump the mud into the multi-stage separator degasser at a pumping rate of 0.1Q2.

[0014] S4. Based on the drilling fluid density, the control system adjusts the motor speed of the three-stage separation device to perform gas-liquid separation of the drilling fluid.

[0015] S5. The drilling fluid undergoes gas-liquid separation, and the separated gases are tested by a gas chromatograph to determine the alkane gas content;

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

[0017] This process involves testing the gas logging zones specified in the well completion design.

[0018] The method for calculating atmospheric stratigraphic levels is as follows:

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

[0020]

[0021] In the formula, H represents the gas-gauge formation, in meters (m); Q1 represents the drilling fluid injection volume, in meters (m). 3 V1 is the volume of the downhole drill body, in meters. 3 V2 is the drilling fluid loss, in meters. 3 r is the well diameter, in meters; v t Δt represents the drilling rate in min / m.

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

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

[0024]

[0025] The advantages of this invention are:

[0026] 1. The multi-stage separation and degassing coalbed methane gas measuring device provided by the present invention achieves multi-stage separation of drilling fluid through centrifugal effect at different rotation speeds, thereby solving the problem of low testing accuracy caused by low degassing efficiency in gas logging;

[0027] 2. By measuring and adjusting the injection volume, flowback volume, and test pump volume of drilling fluid, the gas logging layers and corresponding gas logging content are determined, thus solving the problems of lag and inconsistency in gas logging results in conventional gas logging. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the structure of the present invention.

[0029] Figure 2 This is a schematic diagram of the multi-stage degassing system and test control system in this invention. Detailed Implementation

[0030] like Figure 1-2As shown, a multi-stage separation and degassing coalbed methane gas detection device includes a drilling fluid pump system. The drilling fluid pump 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 pit 12 into the drill pipe via a pipeline and a second mud pump 13. A drilling fluid injection flow meter 14 is installed on the pipeline. A drilling fluid return pipe 10 is also installed at the wellhead 7 of the drilling rig. The drilling fluid return pipe is equipped with a control valve 4 and a drilling fluid return flow meter 5. The drilling fluid return pipe is connected to the mud pit, and a bypass of the drilling fluid return pipe 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 multi-stage degassing system is connected at the front end to the drilling fluid pump suction system and at the rear end 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 degassing unit 64, and a control system 66 connected to the control pipeline 619 of the multi-stage degassing unit and the control pipeline 620 of the first mud pump. The multi-stage degassing unit also has a temperature control system 621. The drilling fluid pump suction system is mainly used to adjust the drilling fluid test volume according to the drilling fluid return flow rate, and simultaneously record data such as drilling fluid injection volume, return flow rate, and test volume. The multi-stage degassing system is mainly used to separate hydrocarbon components in the drilling fluid. The test control system mainly... Used for operation, control, monitoring, and recording of test data for each phase during the testing process, as well as the hydrocarbon component content in the drilling fluid after separation; the multi-stage degassing system includes a drilling fluid suction pipeline 61 connected to the drilling fluid pump suction 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. The drilling fluid discharge pipeline is located 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 separation device is equipped with a separation device housing 610, and a vertical transmission rod 612 is installed inside the separation device housing, with the top of the transmission rod extending 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, and a rotating blade 614 is provided at the lower part of the rotating rod. The bottom of the shell of the separation device is provided with an inlet connected to the drilling fluid outflow pipeline. The upper part of the shell of the separation device is provided with a gas separation output pipeline 616, and the lower middle part of the shell of the separation device is provided with a drilling fluid separation output pipeline 617 connected to the next stage separation device. Each shell of the separation device 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, which is 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 testing method for a multi-stage separation and degassing coalbed methane gas measuring device includes the following steps:

[0032] S1. During the drilling process, the drilling fluid injection flow meter records the drilling fluid injection volume Q1 and calculates the gas-measuring layer H;

[0033] S2. Record time t0 when drilling fluid begins to flow back, and record drilling fluid flow back volume Q2 by drilling fluid flow back meter;

[0034] S3. Based on the drilling fluid return rate Q2, the control system adjusts the first mud pump of the gas measurement system to pump the mud into the multi-stage separator degasser at a pumping rate of 0.1Q2.

[0035] S4. Based on the drilling fluid density, the control system adjusts the motor speed of the three-stage separation device to perform gas-liquid separation of the drilling fluid.

[0036] S5. The drilling fluid undergoes gas-liquid separation, and the separated gases are tested by a gas chromatograph to determine the alkane gas content;

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

[0038] This process involves testing the gas logging zones specified in the well completion design.

[0039] The method for calculating atmospheric stratigraphic levels is as follows:

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

[0041]

[0042] In the formula, H represents the gas-gauge formation, in meters (m); Q1 represents the drilling fluid injection volume, in meters (m). 3 V1 is the volume of the downhole drill body, in meters. 3 V2 is the drilling fluid loss, in meters. 3 r is the well diameter, in meters; v t Δt represents the drilling rate in min / m.

[0043] In practical use, during the drilling of exploration wells, the drill pipe sequentially passes through the overburden 15, bedrock 16, and coal-bearing strata 17. During this process, drilling fluid is pumped from the mud pit 12 into the drilling rig 1 by the second mud pump 13 and then into the drilling formation via the drill pipe 2. The drilling fluid injection volume is measured and recorded by the drilling fluid injection flow meter 14. The drilling fluid is discharged from the drilling formation through the wellbore annulus to the wellhead 7 and flows into the mud pit 12 through the drilling fluid return pipe 10. The drilling fluid return volume is measured and recorded by the drilling fluid return flow meter 5. The measurement results of the drilling fluid injection volume and the drilling fluid return volume are recorded in the test control component. During gas testing, the drilling fluid suction pipe 61 is connected to... Figure 1In the drilling fluid return pipeline 10, the control system 66 adjusts the power of the first mud pump 62 in real time according to the drilling fluid return volume via the first mud pump control pipeline 620 to ensure a constant ratio between the drilling fluid test flow rate and the drilling fluid return volume. The test drilling fluid is pumped from the first mud pump 62 into the multi-stage separator / degasser 64 via the drilling fluid outflow pipeline 63. The multi-stage separator / degasser consists of a primary separation device, a secondary separation device, and a tertiary separation device. In the primary separation device, a motor drives a transmission rod, which, via a coupling, causes the rotating blades to rotate, resulting in centrifugal separation of the pumped drilling fluid. Alkane gas is discharged through the gas separation output pipeline. When the drilling fluid in the separation device reaches a certain height, triggering the electrode output control valve, the valve opens, and the drilling fluid flows into the next stage separation device through the drilling fluid separation output pipeline. Finally, after separation, the drilling fluid is discharged through the drilling fluid discharge pipeline. The tertiary separation devices have the same structure, and the control system controls the motor of each tertiary separation device via the multi-stage separator / degasser control pipeline to control the centrifugal separation speed. During testing, the ambient temperature of the multi-stage degasser was adjusted by regulating its temperature control system to facilitate the separation of heavy alkane gases. The gas separation output pipeline was connected to a gas chromatograph, and the drilling fluid discharge pipeline was connected to... Figure 1 The drilling fluid discharge pipeline is tested, and the drilling fluid is discharged into the mud pit through the pipeline after the test. The alkane gas in the drilling fluid separated by the multi-stage separator degasser is input into the gas chromatograph through the gas separation output pipeline to test the various alkane components and contents, and the test results are recorded into the control system.

[0044] Application examples

[0045] The testing device and method designed in this invention have been used in well PB13-C4 in the Pingdingshan mining area. Drilling of this well began on February 25, 2025, and was completed on March 6, 2025, with a total drilling footage of 990.00 m, a drilling cycle of 24.25 days, and a completion cycle of 29.5 days. During the logging operation in this well, the sensors for various engineering parameters performed stably, fully utilizing the timely monitoring function of the integrated logging instrument, ensuring that the entire drilling operation was under the 24 / 7 monitoring of the logging instrument. The gas logging technicians set the instrument parameters reasonably and in real-time, utilizing the instrument's advanced detection functions to record engineering parameter data promptly and accurately. A total of 15 gas logging anomalies were detected throughout the well section; the test results are shown in Table 2.

[0046] Table 2 Statistical Table of Gas Logging Results for Well PB13-C4

[0047]

[0048] Core samples were taken from the entire PB13-C4 well section. After the cores were retrieved, they were soaked in clean water. Some cores showed a bubble reaction after soaking in water, and gas logging was performed on the corresponding formation sections. Gas logging was also performed on adjacent exploration wells in the same mining area using conventional gas logging equipment. Some cores showed a bubble reaction after soaking, but no gas logging was performed in the conventional gas logging results. This proves that the gas logging results using the testing equipment and method of this invention are more accurate than conventional gas logging.

Claims

1. A testing method for a multi-stage separation and degassing coalbed methane gas measuring device, characterized in that: The device includes a drilling fluid pump suction system and a multi-stage degassing system connected to the drilling fluid pump suction system. The multi-stage degassing system is connected to a test control component. The multi-stage degassing system includes a drilling fluid suction pipeline connected to the drilling fluid pump suction system, a first mud pump, a drilling fluid outflow pipeline, a multi-stage separator degasser, and a drilling fluid discharge pipeline. The multi-stage separator degasser includes a first-stage separator, a second-stage separator, and a third-stage separator. Each separator has a separator housing. A vertical transmission rod is installed inside the separator housing. The top of the transmission rod extends out of the separator housing and is rotated by a motor. A coupling is installed in the middle of the transmission rod. Rotating blades are installed at the bottom of the rotating rod. An inlet connected to the drilling fluid outflow pipeline is installed at the bottom of the separator housing. A gas separation output pipeline is installed at the top of the separator housing. A drilling fluid separation output pipeline connected to the next stage separator is installed in the lower middle part of the separator housing. The testing method includes the following steps: S1. During drilling, the drilling fluid injection flow meter records the drilling fluid injection volume. Q 1. Calculate the atmospheric stratigraphic level H The atmospheric stratigraphic level is calculated as follows: assuming... t Drilling depth at all times h ,but At what time was the atmospheric measurement layer? H , In the formula, H The stratigraphic level is measured in meters (m). Q 1 represents the drilling fluid injection volume, in meters. 3 ; V 1 for Downhole drill bit volume, m 3 ; V 2 For drilling fluid filtration loss, m 3 ; r The well diameter is in meters (m). v t for Drilling rate over a given period, in min / m; S2. Record time t0 when drilling fluid begins to flow back, and simultaneously record the drilling fluid flow rate using a drilling fluid flow meter. Q 2 ; S3. Based on drilling fluid flowback volume Q 2 The control system regulates the first mud pump of the gas measurement system at 0.1... Q 2 The pumping rate will pump the mud slurry into the multi-stage separator and degasser; S4. Based on the drilling fluid density, the control system adjusts the motor speed of the three-stage separation device respectively, that is, the speed of the first-stage separation device is less than the speed of the second-stage separation device is less than the speed of the third-stage separation device, so as to perform gas-liquid separation of drilling fluid; S5. The drilling fluid undergoes gas-liquid separation, and the separated gases are tested by a gas chromatograph to determine the alkane gas content; S6. After testing, the drilling fluid is discharged into the mud pit through the drilling fluid discharge pipeline.

2. The testing method of the coalbed methane gas measuring device with multi-stage separation and degassing as described in claim 1, characterized in that: Each separation unit housing is equipped with an electrode output control valve at the inlet of the drilling fluid separation output pipeline, and the gas output pipeline of the multi-stage separation degasser is connected to the test control component.

3. The testing method of the coalbed methane gas measuring device with multi-stage separation and degassing as described in 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 the mud pit into the drill pipe through a pipeline via a second mud pump. A drilling fluid injection flow meter is installed on the pipeline. A drilling fluid return pipe is also installed at the wellhead of the drilling rig. The drilling fluid return pipe is equipped with a control valve and a drilling fluid return flow meter. The drilling fluid return pipe is connected to the mud pit, and a bypass of the drilling fluid return pipe is connected to the drilling fluid suction pipeline.

4. The testing method of the coalbed methane gas measuring device with multi-stage separation and degassing as described in claim 1, characterized in that: The test control component includes a gas chromatograph connected to the gas separation output pipeline of the multi-stage separator degasser, and a control system connected to the control pipeline of the multi-stage separator degasser and the first mud pump; the multi-stage separator degasser is also equipped with a temperature control system.

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