Analysis of pressure-maintaining coring process in deep coal seams and gas content determination methods
Gas content is an important parameter for calculating coalbed methane (CBM) reserves and guiding their exploration and development. For deep coal seams, the prolonged coring duration and inaccuracies in lost gas volume calculations result in reduced accuracy in gas content measurement using conventi...
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| Main Authors: | , , , , , |
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| Format: | Article |
| Language: | zho |
| Published: |
Editorial Office of Petroleum Geology and Experiment
2025-01-01
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| Series: | Shiyou shiyan dizhi |
| Subjects: | |
| Online Access: | https://www.sysydz.net/cn/article/doi/10.11781/sysydz2025010163 |
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| Summary: | Gas content is an important parameter for calculating coalbed methane (CBM) reserves and guiding their exploration and development. For deep coal seams, the prolonged coring duration and inaccuracies in lost gas volume calculations result in reduced accuracy in gas content measurement using conventional wireline coring methods. To accurately determine the actual gas content in deep coal seams and gas occurrence state, pressure-maintaining coring technology, which retains in-situ pressure and gas content in samples, is considered the most effective method. However, due to the unique characteristics of unconventional reservoirs, such as adsorption gas, there are currently no standardized coring processes or gas content determination methods. To address this issue, this paper analyzed the environmental conditions and gas loss characteristics during each stage of pressure-maintaining coring. Considering the presence of both adsorbed gas and free gas in deep coal seams, the study proposes a method for determining both components based on pressure-maintaining coring. The analysis shows that gas content calculations in pressure-maintaining coring have the characteristics of "four stages, two losses, and two collections". The reasonable design of pressure points during pressure-reducing and gas-collecting stages of pressure-maintaining coring can effectively distinguish adsorption gas from free gas. In addition, by analyzing the differences and connections between the two methods, the gas content measured using pressure-maintaining coring can be used to correct gas loss caused by using wireline coring at the same well platform. Based on this, a method for calculating gas content in deep coal seams based on wireline coring was established. The successful application of pressure-maintaining coring technology is significant for deep coal seam exploration. The study recommends appropriately increasing the number of pressure-maintaining coring test wells in deep coal seam exploration areas to precisely determine the actual gas content in reservoirs. |
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| ISSN: | 1001-6112 |