Sedimentary Study on Coal-formed Gas Reservoir of  Permo-Carboniferous System in Jiyang Area, Shandong

Key words: 
• coal-formed gas /
• diagenesis /
• reservoir sediment /
• reservoir space /
• Jiyang sag

Abstract: This paper studies coal gas reservoir sedimentology on the basis of establishing sequence stratigraphy framework. Coal gas pool stored in sandstone (compact sandstone) reservoir of Permian system becomes important natural gas pool. In Jiyang, sandy deposit, which is mainly featured by river facies and lacustrine coastal faces, develops in Wanshan, Kuishan and Xiaofu Member of the Upper Shihezi Formation. And these three members become the main reservoir of coal gas. The main reservoir sedimentary facies is channel fill formed by channel detention and marginal bank. The main reservoir space of coal gas is induced porosity. In this area sandstone diagenesis of Carbonic-Permian system is very strong and there are less protosomatic intergmular pores. Most intergranular pore space is shaped after corrosion. Matrix or cement filled in intergranular pore space suffered from after-corrosionand then formed such heterogeneousintergranular pore space. The direct cap rock of gas pool of Permian system is mainly fluvial facies of Lower Shihezi Formation, delta plain of Shanxi Formation and Taiyuan Formation and mudstone, coal and carbargilite of limnological facies.