Application of logging data in recognition of coal structure and stratification

The type of coal structure which is very important for CBM exploitation,is closely related to the pore and fracture characteristics of coal reservoir.Taking Hancheng area as an example,based on the analysis of core samples of parameter wells,coal structure was divided into three groups,which are:lump coal (class I),lump-powder coal (class II) and powder coal (class III).According to the analogy of resistivity logs,caliper logs and natural gamma logs of NO.3,5 and 11 coal seams,the relationship between well logs and coal structures in the study area was established:The form of resistivity logs and natural gamma logs of class I and III was smooth box or bell-shaped,while the logs of class II fluctuated strongly;Diameter extension of class II and III was serious and the diameter extension of class II was inhomogeneous.Thus,a method to identify coal structure through using resistivity logging,caliper logging and natural gamma logging is proposed in this paper,and based on this relationship,some stratifications in different coal structures in the same coal seam were also identified exactly.