The Effect of Multi-Scale Faults and Fractures on Oil Enrichment and Production in Tight Sandstone Reservoirs: A Case Study in the Southwestern Ordos Basin, China

The Chang 8 Member of the Upper Triassic Yanchang Formation in southwestern Ordos Basin is a typical tight sandstone reservoir and has an average porosity 8.60% air permeability 0.20 mD. Multi-scale faults fractures are widely developed these reservoirs. In this study, three-dimensional seismic data, outcrops, cores, imaging logs, thin sections were used to classify at multiple scales. Combined with oil production influence multi-scale on enrichment was analyzed. results show can be divided into six levels: type-I faults, type-II large-scale fractures, mesoscale small-scale micro-scale fractures. As scale decreases, number increases power function. Type-I cut caprocks not conducive preservation oil. Type-II connect source rocks reservoirs migration channels source. Large-scale mudstone interlayer seepage channel inside reservoir. Mesoscale controlled by thick interlayers, restricted interlayers or layer interfaces. These main effective storage spaces. Micro-scale serve as important spaces for case study development proves that have greatest impact fluid flow, while wells drilled zone higher capacity. changes degree different scales, strikes, positions faults. Meso- key influencing early single-well production, stable single wells. Consequently, significantly effects reservoirs, research conclusions guide exploration such similar