Shale gas enrichment law of Ordovician Wufeng Formation to Silurian Long-maxi Formation in Anchang syncline of Zheng'an area,northern Guizhou
There are good prospects for shale gas exploration and development in northern Guizhou area on the outer edge of Sichuan Basin.Based on wire-logging,mud-logging,and analytical data,the characteristics and enrich-ment law of shale gas reservoirs of Ordovician Wufeng Formation to Silurian Longmaxi Formation in Anchang syncline of Zheng'an area in northern Guizhou were analyzed.The results show that:(1)The lithologies of Ordo-vician Wufeng Formation to Silurian Longmaxi Formation in Anchang syncline of Zheng'an area in northern Guizhou are mainly composed of siliceous shale and siliceous rock,and the pore types are mainly organic pores,intergranular pores,intragranular dissolved pores,intercrystalline pores,as well as bedding fractures,structural fractures and micro-fractures.The total organic carbon(TOC)content in rocks ranges from 0.34％to 6.65％,with an average of 3.69％.It shows an overall trend of first increasing and then decreasing from bottom to top in the vertical direction.On the plane,it is higher in the syncline core and decreases in a circular band.The mass volume of gas in the rock core ranges from 1.6 to 6.2 m3/t,with an average of 3.9 m3/t.The total gas content of Longmaxi Formation increases vertically with depth,and gradually decreases from the middle of the syncline to the north and south ends in the plane,and from the syncline core to the two sides.The overall brittleness index of minerals is relatively high,indicating good fracturing ability.(2)The Wufeng Formation to Longmaxi Formation in the study area has a unique geological background of"shelf margin,reformed residue,and shallow syncline burial".Its favorable sedimentary environment and paleoproductivity laid the foundation for shale gas enrichment and accu-mulation,good preservation conditions avoided the large-scale escape of natural gas in shale reservoirs,and the overlying Xintan Formation and the underlying Baota Formation formed a sealing combination of"upper cap and lower seal".(3)The residual synclinal shale gas outside the basin is obviously enriched in the synclinal center,the core is a favorable location for shale gas accumulation,the low-angle reverse faults on both wings are also favor-able enrichment areas for shale fas,and the development of micro-fractures is favorable for shale gas accumula-tion and stable production.Therefore,the core site of"wide,gentle and deep"should be considered first for the deployment of wells in middle-shallow residual synclines.
shale gasreservoir characteristicsbrittleness indexupper cap and lower sealfault barriaenrich-ment in coreOrdovician Wufeng Formation to Silurian Longmaxi FormationAnchang synclinenorthern Guizhou
万方数据
维普
