The Characteristics Of Permian Marine Shale Reservoirs In Xuancheng Area Of Lower Yangtze

The marine shale of the Permian Dalong Formation and Gufeng Formation in the Lower Yangtze Xuancheng area is extremely heterogeneous,the pore structure and type are complex,and the gas-bearing properties of different layers vary greatly.It is necessary to carry out further reservoir research work on the Dalong Formation and Gufeng Formation in this area to clarify the development characteristics and differences of shale reservoirs in different strata.Therefore,in this paper,the shale shales of the Permian Dalong Formation and Gufeng Formation in Well Gangdi 1 in the Yangtze Xuancheng area are taken as research objects.Based on literature investigation and experimental testing,the reservoir characteristics of the Dalong Formation and Gufeng Formation are explored and favorable reservoirs are conducted.Preferably.The content of brittle minerals in the Dalong Formation and Gufeng Formation are both greater than 40%,and the fracturability is good.Three lithofacies such as siliceous shale,mixed shale and clay shale are developed.The TOC of the Dalong Formation ranged from 0.59%to 4.13%,with an average of 2.12%;kerogen microscopic component analysis revealed that the organic matter types were type III and type II;the organic matter maturity was 1.34%to 1.72%,with an average of1.51%.The shale is a medium-good source rock.The TOC of the Gufeng group ranges from 0.64%to 13.75%,with an average of 6.4%;the analysis of kerogen micro-components shows that the organic matter types are type III and type II;the organic matter maturity is 1.26%to 1.5%,with an average of 1.41%.The shale is a good source rock.Silica shale has better hydrocarbon generation potential than mixed shale than clay shale.The shale of the Dalong Formation is dominated by alternating or interstitial organic matter,with organic pores,matrix pores,and micro-fractures all developed;the Gufeng Formation sees more irregular clumps,bands,and biostructure organic matter,which is very It is dense,with no pores developed inside,and matrix pores are more developed,mainly interlayer pores of clay minerals,and more diagenetic shrinkage fractures are developed.Quantitative analysis of microscopic pores shows that there are many open pores in the Dalong Formation,and the pore types are dominated by slab-like plate-like pores,which have good connectivity and are conducive to the migration of shale gas;the Gufeng Formation has fewer open pores and pores The types are mainly slit holes or micropores,and the pore connectivity is average.Compared with the Gufeng Formation,the mud shale of the Dalong Formation has larger specific surface area and pore volume,which is beneficial to the adsorption of shale gas.Reservoir types and characteristics of shale of different lithofacies are inconsistent.Siliceous shale facies have organic pores and large pores,and matrix pores have intercrystalline pores;mixed shale facies have organic pores,and interlayer pores and intercrystalline pores are rare.Such as matrix pores,with pore scales ranging from nanometers to micrometers;the content of clay minerals in clayey shale facies is as high as 49%,and the pores are mostly a small amount of migrating organic pores and elongated interlayer pores of clay minerals,organic matter content Lower.The gas content of the Dalong Formation is 0.05-0.62m~3/t,with an average of0.32m~3/t,while the gas content of the Gufeng Formation is extremely low and almost gas-free.The gas content of the siliceous shale of the Dalong Formation is higher than that of mixed shale Higher than clay shale.Comprehensive evaluation of the characteristics of the shale mineral composition,organic matter characteristics,porosity and permeability,and gas content of the Dalong Formation/Gufeng Formation reservoir shows that the Dalong Formation reservoir is superior to the Gufeng Formation and has more exploration potential;Siliceous shale facies are superior to mixed shale facies than clay shale facies.