QUANTITATIVE EVALUATION OF FAULT CONNECTIVITY AND ITS PETROLEUM SIGNIFICANCE BASED ON TOPOLOGICAL ANALYSIS: A CASE STUDY FROM THE WELL H AREA, SOUTHERN SICHUAN BASIN

Due to the influence of multi-stage structural superposition, a large number of medium to small scale faults were developed in deep shale gas reservoir in the southern Sichuan Basin. Quantitative analysis and evaluation of fault network structures and plane connectivity are of great significance for deep shale gas exploration and development. On the basis of detailed delineation of medium to small scale faults in deep shale gas reservoir, this study conducted topological structural analysis and connectivity evaluation of fault networks in the well H area of southern Sichuan Basin. By integrating topological quantitative evaluation with the production data of shale gas wells, the controlling effects of fault network topology and plane connectivity on shale gas accumulation were discussed. This investigation indicates three aspects of new findings. (1) High level of spatial variation was observed in the distribution of fault nodes and branches in the well H area in southern Sichuan Basin. Their NE-SW oriented distribution, being in accordance with the strikes of folds, presents high concentration in the cores of three narrow anticlines and limited distribution in the three synclines, respectively. (2) There are significant differences in fault network connectivity in different structural domains in the well H area, with better connectivity in the anticlines than 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. (3) There is a significant correlation between the production data of shale gas and the topological connectivity of fault networks in the well H area. With increasing fault connectivity, the production of shale gas climbs up and then falls down, indicating that neither high connectivity nor low connectivity of fault networks benefits shale gas accumulation.