Abstract:
BACKGROUNDThe pore characteristics of shale are one of the key parameters for evaluation of the shale reservoir capacity. Scanning Electron Microscopy (SEM) has been widely used to describe the pore characteristics of shale. However, the classification of micro-pore types in mud shale reservoirs in the literature was relatively diverse, and the quantitative characterization of pore based on SEM was relatively lacking.
OBJECTIVESTo classify the pore types and quantitatively characterize these pores in shale.
METHODS18 shale samples were selected as the research object in this study. Based on the form, position and origin of pores observed by argon ion polishing and Scanning Electron Microscopy, the types of different pores in the sample were classified. By using JMicroVision image analysis software, the pore characteristics including the number of pore types, pore size, face rate, shape coefficient, probability entropy and other parameters were quantitatively described.
RESULTSThe inter-crystal (particle) pores and organic pores were the most developed, followed by intra-crystal (particle) pores and crystal gap inter-crystal (particle) pores. The sizes of pore were mainly nanometer. The probabilistic entropy of intra-crystal (particle) pores and organic pores were mainly distributed between 0.5 and 0.7, with a different shape coefficient distribution. The shape coefficients of organic pores were mainly distributed between 0.6 and 0.7, and their shape were mainly oval or nearly circular. The shape coefficient of intra-crystal (particle) pores and inter-crystal (particle) pores were mainly between 0.3 and 0.7, which were mainly affected by the original pore morphology, compaction and dissolution.
CONCLUSIONSThe combination of SEM and JMicroVision is an effective means to quantitatively study the development characteristics of different types of micropores. This work has laid a foundation for the study of the genesis and evolution of micropores.