Research On Evaluation System Of China Southern Constituency Marine Shale Gas

Recent years, unconventional gas attaches great concerns of various countries and oil companies. Shale gas has become a hotspot area in global unconventional natural gas exploration and development currently. But a suitable method to evaluate Chinese shale gas do not exist to select area. The author anlayzed regional geological setting of shale gas reservoir and shale gas characteristics and basic conditions of shale gas accumulation of the study area based on "tectonic controls basin, basin controls sedimentary facies, facies control shale distribution ". Shale gas reservoir elements are mainly researched using basin analysis technology. Meanwhile a analogically analyses of the shale gas accumulation conditions of American five major shale gas basins and the study area are carried out in order to explores the evaluation ideas and technical methods of favorable objective of shale gas in Southern China. Shale in Southern China is old, with high degree of thermal evolution, poor storage conditions, complex structural conditions and ground conditions, so the evaluation system and standards of the selected area’s shale gas in Southern China should take the retention conditions as the core, with geological assessment and economic evaluation taken into account.Using Argon ion buffing, scanning electron microscopy and GRI, system researched3sets of the shale reservoir space, they mainly contain the nanoscale pore, the aperture of lower Cambrian shale is mainly2～10nm, accounting for70%, the Lower Silurian Longmaxi shale aperture is generally2～50nm (74.3%),2～10nm and10～50nm each accounted for about45%, while the pore size of Permian Dalong Formation shale is slightly larger, the pore diameter is mainly distributed between10and50nm, the nano-scale pore throat of lower Cambrian clay shale is smaller, with relatively poor storage performance, storage properties of lower Silurian and upper Permian clay shale is preferable.The evolution of Southern marine sedimentary basin is multi-stage, different evolutionary stages have different types of dark shale sets. There are a few "sweet spots" of shale gas exploration. They include Jiumenchong Formation’s deep-water continental shelf shale formed on the early Cambrian passive margin of Qiannan sag, Wufeng-Longmaxi Formation’s deep-water continental shelf mud shale of the intracratonic lag deposit formed in Southeast Sichuan in Late Ordovician-Early Silurian, and the Dalong Formation’s basin siliceous shale formed in the Bathyal basin in Late Permian of Hunan areaWe select three sets of main shale of Lower Cambrian, Upper Ordovician-Lower Silurian and Upper Permian by the key parameters of interested area. There are three favorable zones which were Southeast Sichuan,around the upheaval in the middle of Yunnan province and central Hunan. We continued to evaluate it and preferably choosed some main exploration aims like huangping zone in Qiannan sag, pengshui zone in Southeast Sichuan for the three important exploration layer systems and four types of shalesEvaluation system guided exploration and production timely, the mining area of shale gas were expanded, the drilled wells (eg. HY1、PY1、XY1) got good effect.