| Co-exploration and co-mining of the unconventional natural gases in coal series, including coalbed methane(CBM), tight sandstone gas and shale gas, is leading the direction of natural gas industry in China, but the research on the symbiotic reservioring is still in its infancy. Therefore, based on the sample tests and literature review, the sequence sratigraphic framework of Permo-Carboniferous coal measures in Linxing area of northeastern Ordos Basin has been built. Cycle changes of physical property and sequence control of the source-reservoir-cap rock assemblages in coal measures have been discussed, and the distribution of favorable source-reservoir-cap rock assemblages has been predicted, relying on typical drillhore columns. The Benxi, Taiyuan and Shanxi formations are divided into 12 three-order sequcences, and channel sand bodies in lowstand system tract(LST) are the high quality of tight sandstone reservoirs, and coal seam and dark shale in the transgressive systems tract(TST) and highstand systems tract(HST) are the excellent hydrocarbon source rocks, whereas shales in the upper TST and HST have excellent sealing capacity. Pore structure of rocks shows vertical ―Ⅱâ†'â… â†'Ⅲ‖ model inside a three-order sequence, the specific surface area, median pressure and micropore volume first increased and then decreased, and the maximum value appeares near the maximum flooding surface(MFS), but the porosity is in contrast. Three types of source-reservoir-cap rock assemblages in coal measures can be distingushed, including the source-reservoir integration, immediate body and mixed one. In vertical, coal measures containe 4~5 sets of source-reservoir-cap rock assemblages, and each can stride across serveal three-order sequences, which varies in the different drillhores. Investigation showed that the source-reservoir-cap rock assemblages are the most favorable in the SQ2-SQ5 and SQ5-SQ9 sequence groups of the northern Linxing area. |
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