基于煤岩脆性指数的煤体结构测井定量判识

摘要

准确判识煤体结构是煤层气勘探开发研究的一个关键问题,不同煤体结构类型的煤层,因孔隙大小、裂隙网络和破碎程度不同,对煤层气富集和运移的影响也不相同.根据煤体的破碎程度,将沁水盆地F区块3#煤层煤体结构类型划分为原生结构、过渡结构和碎裂结构,并分析了不同煤体结构的测井响应特征.统计表明:随着煤体破碎程度增加,测井曲线上通常表现为密度与电阻率均降低、井径扩大、声波时差增大.在测井资料定性划分煤体结构的基础上,提出利用阵列声波测井资料计算煤岩脆性指数来定量判识煤体结构.通过实际应用认为,用煤岩脆性指数定量判识煤体结构是可行的,判识结果与实际钻井取心资料符合率较高,能够提高煤体结构研究的精度.%An accurate identification of coal structure is one of key issues in coalbed methane (CBM) exploration and development.Different coal structure have different influences on the migration and enrichment of coalbed methane.According to the coal broken degree,the coal structure of No.3 coal bed was divided into primary struc-ture,transition structure and cataclastic structure in F block of Qinshui Basin,and the characteristics of their log-ging response were analyzed.The results show that the logging curve is usually characterized with lower density and resistivity,and higher borehole diameter and acoustic time as the coal broken degree increases.Based on the qualitative identifying of coal structure by logging data,array acoustic logging data was used to calculate the coal rock brittleness index (BI) quantitatively.The application results show that it is feasible to identify coal structure quantitatively by the coal rock brittleness index,the identification result is consistent with the actual drilling coring data,and it can greatly reduce the error of the qualitative identification.