Characteristics and potential for exploration of shale reservoir in Dalong Formation in northern Sichuan
In this study,we analyze the distribution of vertical and horizontal lithofacies as well as the sedimentary facies of a typical field section of the Dalong Formation in Guankou Village of Chaotian District in northern Sichuan,based on field observations and the identification of thin sections of rock and micropaleontological fossils.We then discuss the potential for shale exploration based on data from wells in the area,the main and trace geochemical elements in it,its total organic carbon content,physical properties,and micropores.The results showed the following:(1)A set of assemblages of gray siliceous limestone,gray-black calcareous shale,gray-black carbonaceous shale,and mudstone had developed from top to bottom in the Dalong Formation.The siliceous limestone and argillaceous limestone in the upper Dalong Formation contained a large amount of ammonites,conodonts,and radiolaria fossils,while the carbonaceous shale and calcareous shale in the lower Dalong Formation contained a small amount of Rhizaria,ostracods,bivalves,gastropods,and brachiopods.(2)The sedimentary environment of shale in the Dalong Formation had an anoxic-poor oxygen-saline water environment that was conducive to the preservation and enrichment of organic matter.(3)The organic matter of shale in the Dalong Formation was of the Ⅱ 1 type.It was highly abundant,and was in the mature stage of its evolution.The pores mainly consisted of intergranular pores,intraparticle pores,and organic matter pores.The black shale in the upper Dalong Formation was highly porous and contained a large amount of brittle minerals.The shale had good fracture-related properties and suitable geological conditions for the accumulation of shale gas.In sum,shale in the Dalong Formation in northern Sichuan has considerable potential for extraction,and it can be used as a backup reservoir for the exploration of shale gas.
万方数据
维普
