基于核磁共振技术的煤层含气量评价方法  

Evaluating method of gas content of coalbed methane based on nuclear magnetic resonance technology

作　　者：余杰 秦瑞宝 黄涛 李利 YU Jie;QIN Ruibao;HUANG Tao;LI Li(School of Geophysics and Petroleum Resources,Yangtze University,Wuhan 434023,China;Exploration and Development Research Institute,CNOOC Research Institute Co.,Ltd.,Beijing 100028,China)

机构地区：[1]长江大学地球物理与石油资源学院,湖北武汉434023 [2]中海油研究总院有限责任公司勘探开发研究院,北京100028

出　　处：《煤炭科学技术》2023年第11期158-165,共8页Coal Science and Technology

基　　金：中国海洋石油集团有限公司“十四五”重大科技项目(KJGG2021-1000)。

摘　　要：我国煤层气资源储量十分丰富,是良好的天然气后备资源,开发利用煤层气具有多重价值。煤层含气量是评价煤层的关键参数,也是决定煤层气勘探开发选区与产能潜力大小的重要因素,利用测井技术评价含气量可以低成本获得地下煤层气关键参数,准确获得含气量对煤层气勘探开发具有极为重要的影响。为了规避煤层中天然气不同赋存状态导致的密度不同和Langmuir单层吸附模型造成的含气量低估,提出了一种基于核磁共振技术评价煤层含气量的新方法,采用经过校准的核磁共振仪器测量煤层中的核磁共振信号,通过分离煤层中吸附态天然气的核磁共振信号,进而计算单位体积地层中天然气分子的摩尔数,综合体积密度测井换算为标准状态下煤层含气量。为验证方法的有效性,设计开展了实际煤样甲烷等温吸附与核磁共振联测试验,试验结果表明,利用不同的T2(横向弛豫时间)截止值可以区分煤层中不同赋存状态的甲烷气体,基于核磁共振新方法计算的与试验测量的煤层含气量符合很好,证明了新方法的有效性。实际测井资料处理解释结果表明,基于核磁测井新方法比常规测井方法计算煤层含气量更加有效。China has abundant coalbed methane(CBM)resources,which is a good reserve of natural gas.The development and utilization of CBM has multiple values.Gas content of coal is the key to evaluate coal seam,and it is also an important factor to determine the exploration and development area and productivity potential of CBM.Using logging data to evaluate gas content is an important means in CBM exploration and development.In order to avoid the density difference caused by different methane states and the underestimation of gas content caused by Langmuir monolayer adsorption model in coal seam,a new method is adopted to separate the NMR signal of adsorbed natural gas in coal seam,calculate the molecules mole number of natural gas in unit volume formation,and convert into the gas content in standard state by density logging.The experimental results of methane isothermal adsorption and NMR show that different T2 cut-off values can be used to distinguish methane states in coal seam.The adsorpted methane content calculated by using new method based on NMR is in good agreement with the measurement of coal sample,which proves the effectiveness of the method.The actual logging data processing and interpretation results show that the new method based on NMR logging is more effective than the method based on conventional logging in calculating gas content of coal seam.

关 键 词：煤层气 核磁共振 T2截止值 含气量 LANGMUIR吸附 

分 类 号：TE19[石油与天然气工程—油气勘探]