Quantitative evaluation of fault connectivity based on topological structural analysis and its petroleum geological implications:A case study of the Well H area in the southern Sichuan Basin
Due to the influence of multi-stage structural superposition,a large number of medium to small scale faults are developed in deep shale gas reservoirs in the southern Sichuan Basin.Quantitative evaluation of fault network structures and plane connectivity is of great significance for deep shale gas exploration and development.In this paper,the medium to small scale faults in the deep shale gas reservoirs in the Well H area in the southern Sichuan Basin are delineated in detail using 3D data.On this basis,topological structural analysis and plane connectivity evaluation are conducted on faults in the shale reservoirs in this area.Then,through correlation analysis of available production data of shale gas wells,the controls of fault network topology and plane connectivity on shale gas enrichment are qualified.This study achieves new findings in three aspects.First,the fault nodes and branches show noticeable differential distribution in space,and agree well with the structures in strikes(NE-SW),as stripes.They are concentrated in the three narrow anticlines,but rare in the three synclines.Second,plane fault connectivity is greatly variable in different structural positions,with better connectivity in the anticlines than in the synclines.The northern portion of the western anticline,the eastern anticline and the central anticline present good,medium and poor fault connectivity,respectively.In the eastern anticline,the northern portion presents relatively higher connectivity than the southern portion.Third,there is a significant correlation between the production data of shale gas and the plane fault connectivity.With increasing fault connectivity,the production of shale gas climbs up and then falls down,indicating that neither high connectivity nor low connectivity of faults is beneficial to the enrichment of shale gas.This recognition is very valuable for evaluating the connectivity of medium to small scale faults and highly practical for exploration and development of deep shale gas.
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