Study On The Characteristics And Resource Potential Of The Lower Paleozoic Shale Gas Reservoir In Northeastern Yunnan Region

The Lower Paleozoic Qiongzhusi Formation(Fm.) and Longmaxi Fm. is the main production of southern marine shale gas exploration and development in our country strata. And it shows a great potential of resources. With a wide range of longitudinal horizontal distribution, large thickness, good continuity, organic carbon content and high degree of thermal evolution, porosity, good brittleness characteristics.This article has taken the Lower Paleozoic marine shale in the northeast of Yunnan Zhaotong as the research object. Through data collection, field geological survey, experimental test analysis and other means to analysis reservoir characteristics of rock gas, potential resources from the four aspects of geological background, sedimentary environment, source rock, reservoir characteristics, occurrence characteristics and preservation conditions, and then predict favorable areas and draw the following results and understanding:(1) The sedimentary facies of Qiongzhusi Fm. is deep shelf. The average thickness of Qiongzhusi is 200～400 m, the buried deep is 3000-4500 m. The sedimentary facies of Longmaxi Fm. is shallow shelf. The average thickness of Longmaxi Fm. is 100 m, while the maximum is 350 m. The buried depth of Suijiang County in eastern, Weixin County in the northern is more than 3000 m, and Yanjin county and Daguan County Creek in center buried in less than 2000 m.(2) Due to high degree of thermal evolution, two sets of shale in mature stage.(3) The brittle mineral content of Qiongzhusi Fm. is more than Longmaxi Fm., while the Longmaxi Fm. contents more clay minerals and carbonate minerals than Qiongzhusi Fm.(4) The Lower Paleozoic shale has rich pores and fissures, and the main innergranular pore intergranular pore, intergranular pore and pore types of organic matter etc. Mercury injection experiments show that the transition pore and the pore is the main part of Qiongzhusi Fm. and Longmaxi Fm. shale pore.(5) Two sets of shale has entered the late diagenesis after a deep effect in the period of geological history. The clay minerals are illite/smectite mixed layer and illite, with the series transformed chlorite minerals. A large number of holes are formed in the process of mineral transformation, which can provide effective space for the occurrence of shale gas.(6) It is estimated that the favorable zone of shale gas resources in Northeast Yunnan shale gas is 6188.9 ×108 m3. The prospect area of shale gas resources in Northeast Yunnan amount to 4736.74 × 108 m3; The forecast area of shale gas resources in Northeast Yunnan to 14800.15 ×108 m3.