IMPACTS OF SENSITIVE MINERALS AND SEDIMENTARY MICROFACIES ON THE SENSITIVITY OF FRACTURES IN THE I SUBMEMBER OF THE FIRST MEMBER OF THE SILURIAN LONGMAXI FORMATION: A CASE STUDY IN THE DIANQIANBEI AREA, CHINA

摘要

In this study, scanning electron microscopy and reservoir sensitivity experiments are implemented to study types and distributions of sensitive minerals and distributions of sedimentary m icrofacies in the I submember of the first member of the Silurian Longm axi Formation, accompanied by investigation into shale fracture sensitivity and corresponding in fluential factors. Sensitive minerals include quartz, carbonate minerals, illite , illite/sm ectite mixed layer, lim onite, pyrite, and feldspar. Contents of velocity-, water/salt-, and alkali-sensitive minerals increase northeastward or northward, w hile contents of acid- sensitive and brittle minerals are high in the northeast and southwest and low in the central part of the study area. D istributions of fracture sensitivity damages are related to distributions of sensitive mineral contents. Specifically, siliceous shales are subjected to damages that are related to velocity-, alkali- and acid-sensitivity, siliceous argillaceous shales experience velocity- and water/salt-sensitivity-related damages, w hile siliceous calcareous shales are vu lnerable to acid-sensitivity-related damages. Shales in the study area are featured by their relatively strong stress sensitivity, w hich is speculated to be controlled by the content of brittle minerals and the type of support structures.