沁水盆地南部TS地区煤层气储层测井评价方法

摘要

煤层气是一种自生自储于煤岩地层的非常规天然气资源,其储层测井评价内容及方法不同于常规天然气,在煤层气勘探开发过程中更关注于有关煤岩工业分析组分、基质孔隙度、裂缝渗透率及煤层含气量等一系列关键的储层参数.针对沁水盆地南部TS地区煤层气勘探目标层,分析了各种测井响应特征,采用回归分析法计算煤岩工业分析组分；针对煤层气含量影响因素众多且较为复杂的特点,结合相关地区煤岩样品实验分析结果,利用基于等温吸附实验的兰氏煤阶方程估算煤层含气量参数；通过煤岩孔隙结构的分析,采用变骨架密度的密度孔隙度计算公式求取煤岩总孔隙度,利用迭代逼近算法计算裂缝孔隙度；根据煤岩裂缝中面割理发育而端割理不甚发育的特点,以简化的单组系板状裂缝模型计算煤岩裂缝渗透率.通过对TS -A井进行实际计算,结果表明,煤岩工业分析组分和煤层含气量计算结果精度高,总孔隙度一般在5.5％左右,而裂缝孔隙度则大多小于0.5％,裂缝渗透率主要分布在0.001×10-3～10×10-3 μm2之间,孔渗参数计算结果与相邻井区现有资料相符.采用测井方法可以快速、系统地对煤层气储层多种参数进行准确评价.%Coalbed methane (CBM) is an unconventional natural gas which is generated and stored in coal-beds. Unlike conventional natural gas, the parameters of proximate analysis components, matrix porosity, frac-tural permeability and gas content and so on, should be paid more attention in the evaluation of coalbed methane reservoir. In this paper, geophysical logging data are used to evaluate the parameters of coalbed methane reservoir in the TS District of Southern Qinshui Basin. First the responses were analyzed from the geophysical logging data, and then the proximate analysis components of coal were calculated by regression analytical method and its application condition was studied. Considering the variety and complexity of the factors of CBM content, the Langmuir rank equation method, which is based on the isotherm adsorption equation, was introduced to estimate the CBM gas content through combining the analysis results of the correlation region coal samples. By analyzing the dual porosity characters of coalbeds, the total porosity can be calculated by density porosity formula of variable matrix density, while using the dual lateral logging data, the fracture porosity can be calculated by iteration approximation method. At last, according to the well developed face cleat but the little developed butt cleat in the coalbeds, the fractural permeability of CBM reservoir can be calculated by a simplified single group plate crack model. The calculation result of well TS-A show that the proximate analysis components and CBM gas content are with high precision, meanwhile, the total porosity is about 5. 5% , the fracture porosity is mostly less than 0. 5% , and the fracture permeability is about 0. 001 × 10-3 u,m2 to 10 × 10 -3 μm2. These poroperm characteristics matched well with the data of adjacent area. These means the certain parameters of CBM reservoir can be estimated accurately by geophysical logging data.