The Study Of Shale Gas Enrichment Pattern In The Da'anzhai Member Of Ziliujing Formation Of Lower Jurassic In Easthern Sichuan Basin, China

Tons of research data show that the shale gas resource in China is rich, and the enrichment conditions are similar with the USA.Owning to the different geological conditions, it is hard to copy the American development model, and should pay attention to geological characteristics of shale gas. The investigation of shale gas resources from Da'anzhai member of lower Jurassic in east Sichuan basin holds that it is mainly controlled by lacustrine deposition, and contains brittle mineral. Therefore,the resource potential is well, and it may be beneficial to fracturing treatment.However, it buried so deep that has lower overall exploration degree, so the gas enrichment pattern can be researched detailed here, and find the “sweet sopt” to guiding the production.Using comprehensive research to analyse gas enrichment pattern of Daanzhai member in research region, the paper gets following understandings:(1)The rock assemblages of organic-rich shale are mainly gray and black shale,followed by shell limestone and black shale of the Da'anzhai Segment in study area.(2) one sedimentary facies grows in research region: lake facies. The lakeshore,shallow lake and semi-deep lake facies are widely distributed.(3) The organic geochemical analysis illustrates the important information: the kerogen is primary in type II2, the proportion of type III is high additionally; the organic matter abundance shows they are better hydrocarbon source rocks?(4) The shale is mainly include clay mineral and quartz. The content of brittle mineral is more than the overall average, illustrates the shale has good brittleness, and the compressive strength is lower.(5) The physical analysis shows some informations: the shale primary developed organic pore, inorganic pore(intragranular, intergranular and intercrystalline pore),and fracture systems(macro and micro cracks); it has higher average of porosity and permeability, and porosity and permeability showed a positive correlation.(6) Research on the main factor displayed that the gas content is controlled bytemperature, pressure, TOC, thermal evolution degree, mineral composition, pore and fracture, and the sedimentary facies, lithofacies, fractures and barrier layer determined shale gas enrichment. According to the above, the Daanzhai member of shale gas exploration potential in the study area is bigger,it is expected to further breakthough.