Characteristics of shale gas reservoir and enlightenment of exploration in Qiongzhusi Formation in southern Sichuan Basin
The Qiongzhusi Formation of Cambrian(∈1q)in Sichuan Basin is the most favorable strata for explo-ration and development of shale gas besides the Wufeng Formation of Ordovician(O3w)and Longmaxi Forma-tion of Silurian(S1l).Taking the middle part of Deyang-Anyue rift trough as the research object,meanwhile uti-lizing existing seismic,drilling,logging,experimental data,this paper has analyzed the basic characteristics of ∈1q shale gas reservoirs,and has analyzed the differences between shale gas reservoirs of ∈1q and S1l in south-ern Sichuan Basin,and also has provided technical support for evaluation of layers,optimal selection of advanta-geous areas in ∈1q.The main conclusions are as follows:(1)There are differences in sedimentary paleogeomor-phology of ∈1q,which can be divided into three kinds of sedimentary paleogeomorphology in trough,slope and outside zone of trough,which control the thickness distribution and quality of shale reservoir.(2)In the middle part of Deyang-Anyu rift trough,the sedimentary environment is superior,and the preservation conditions are good;the structure is simple,the thickness of reservoir is large,and the horizontal stress difference between two directions is small,which are conducive to reservoir reconstruction;the buried depth of the target layer is large,which brings challenges to the implementation of the project.(3)The evaluation of layers and optimal se-lection of advantageous areas of ∈1q should follow the overall idea of"vertical stratification and horizontal zona-tion".In the vertical direction,the black shale of layer⑤ should be the main target of the current research,and gradually expand to other layers;in the plane direction,the paleogeomorphic region of the trough and slope should be the main areas to be explored at present,and gradually expand to the zone outside the trough.
Southern Sichuan BasinQiongzhusi FormationCharacteristic of shale gas reservoirEnlightenment of exploration
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