Geological Characteristics Of Shale Gas In The Lower Silurian Longmaxi Formation In Weiyuan Area, Southern Sichuan

Weiyuan area plays an important role in China’s shale gas industry,it is a demonstr ation area of shale gas exploration in China.To further refine the study of the region and precise location deployment.This paper is a study of the shale in the Longmaxi formation in weiyuan area and fully investigate the geological data of the region.Refer to previous research results,After the field reconnaissance and sample collection.Various analytical methods are used.The geological characteristics of the shale formation,sedimentary facies,organic geochemistry and reservoir characteristics of longmaxi formation in the research area were studied.According to core and logging data,analyz the characteristics of sea level fluctuation and sedimentary cycle,the bottom interface of longmaxi formation in weiyuan area was identified.Divide it into two subparagraphs,the second paragraph is divided intofour small layers:a,b,c and d.Organic shale is mainly concentrated at the bottom.The study area is affected by the ancient uplift of leshan-longnu temple,the formation of longmaxi formation is characterized by the gradual thickening of north to south st rata.According to the sedimentary facies,such as rock type,biological assemblage and sedimentary structure.The longma stream group in weiyuan area was divided into two sub-facies and five microfacies.The mud microfacies is the most favorable for the enrichment of shale gas.By analyzing geochemical features in the study area,found that organic matter types in the study area are mainly Ⅰ-Ⅱ 1type.The TOC value is more than 2%.The organic carbon is the highest in the neijiang-zigong area.The TOC value is more than 3%.The Ro value is generally greater than 2%.The thickness distribution of black m udstone in the longmaxi formation in weiyuan(20-60m).Horizontal continuity is good,from north to south gradually thickening.Adjacent to leshan-longnu temple area,the thickness of the change is large.The thickest black shale(60-80m)in the southern neijiang-zigong area.The conditions are favorable for the formation of shale gas reservoirs.The quartz content of longmaxi formation in the study area is generally greater than 40%.It is beneficial to the fracturing and reconstruction of gas well.The storage space types are mainly micro-pores and fractures.The effective porosity is generally less than 1%,and the permeability is much less than 0.01×10-3μ m2.High gas content.A mong them,the total gas content of the W-203 well is 6.96m/t.The total gas content of the W-206 well is 3.5m3/t.Combined with the effective shale thickness,organic matter abundance,organic maturity and mineral composition of longma stream formati on in weiyuan area.This paper divides and evaluates the shale of longma stream in the region.The weiyuan-neijiang-zigong area is divided into a favorable area for shale gas enrichment.