Identification of paleokarst fractured-vuggy reservoir based on fault coordination:A case study of the Qixia Formation in southern Sichuan Basin of China
The paleokarst fractured-vuggy reservoir is an important type of carbonate reservoir,the accurate identification of which is crucial for the exploration and development of carbonate oil and gas reservoir as well as for accessing carbonate deposits.The reservoir of the Qixia Formation is a typical fractured-vuggy reservoir in southern Sichuan Basin,with the characteristics of low porosity and permeability.The early fractured karst vug is typical pre-existing"mechanical structural surface"that significantly influences the formation of subsequent faults.In this study,we use the coordination between the strike of the reverse fault and the axial direction of the local structure(fault coordination)to predict,analyze,and identify the fractured-vuggy reservoir in the Qixia Formation.The results were verified by the characteristics of production of gas wells and seismic data,and yielded an accuracy of higher than 85％.They showed that the distribution of the fractured vug in the Qixia Formation was mainly controlled by non-coordinated faults on and close to the anticline,and large-angle reverse faults in the syncline.The identification of fractured vugs based on highly non-coordinated faults yielded a higher accuracy than that based on the large-angle reverse faults.The work here provides an important reference for the identification of paleokarst fractured vugs in other regions.
paleokarst fractured-vuggy reservoirfault coordinationcarbonate reservoirQixia Formation in southern Sichuan Basin
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