深部煤层钻孔保压取心流程分析及含气量测定方法

Analysis of pressure-maintaining coring process in deep coal seams and gas content determination methods

吴见 张松航 贾腾飞 晁巍巍 彭文春 李世龙

WU Jian ZHANG Songhang JIA Tengfei CHAO Weiwei PENG Wenchun LI Shilong

1. 中联煤层气有限责任公司, 北京 100016; 2. 山西省三气共采省技术创新中心, 太原 030000; 3. 中国地质大学(北京), 北京 100083

1. China United Coalbed Methane Co., Ltd., Beijing 100016, China; 2. Technical Innovation Center for Three Gas Co-Production of Shanxi Province, Taiyuan, Shanxi 030000, China; 3. China University of Geosciences (Beijing), Beijing 100083, China

含气量是煤层气储量计算和勘探开发的重要参数。针对深煤层，由于提心时间长，损失气量计算失准，导致绳索取心含气量测试方法准确性降低。为了准确获取深煤层的真实含气量，确定气体的赋存状态，能够保留样品原位压力和原位含气量的保压取心技术被认为是最有效的方法。然而，由于非常规储层保压取心的特殊性(含吸附气)，目前还没有统一的取心流程和标准的含气量测定方法。为此，通过分析保压取心各阶段的环境特点和含气量损失特征，针对深煤层存在吸附气和游离气的特点，提出了基于保压取心的吸附气和游离气的测定方法。分析表明，保压取心含气量计算具有“四阶段、两损失、两收集”的特点；合理设计保压取心降压集气阶段的压力点，能够有效区分吸附气和游离气。此外，分析保压取心和常规绳索取心的差异和联系，认为通过同井台保压取心含气量可校正绳索取心损失气量，进而建立基于绳索取心的深煤层含气量计算方法。保压取心技术的成功应用对深煤层勘探意义重大，建议在深煤层勘探区适当增加保压取心井测试，以明确储层的真实含气性。

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.

中海油“十四五”重大科技项目(KJGG2022-1002)和国家自然科学基金项目(41872178，U1910205)联合资助。

https://doi.org/10.11781/sysydz2025010163