Abstract:

The southwest margin of Ordos Basin has developed faults and fractures to varying scales, significantly enhancing the permeability of tight reservoirs and forming high-quality fault-fracture reservoirs against a backdrop of low permeability reservoir types. However, this also complicates the reservoir's homogeneity and the variability of its capacity, posing challenges for fine characterization of the reservoir's internal structure and for researching capacity control factors. To address these issues, the study employs spatial characterization of the fracture system, fracture classification, and capacity comparative analysis. Further, the development characteristics of the fault-fracture reservoir are defined through joint well-seismic and reservoir research. Key findings from this research include: 1） Establishment of the “binary four zones” model for fault-fracture reservoirs, which divides the reservoir into four distinct zones: the core fracture zone, the induced fracture zone, the micro-fracture transformation zone, and the matrix pore zone. Among these, the core fracture zone is identified as the primary contributor to production yield. 2） It is observed that the longer the fault extension length and the higher the solid drilling structure position, the higher the single well production capacity in the core fracture zone. The induced fracture zone's proximity to the fault correlates with higher production capacity, demonstrating the spatial impact of fault structures on reservoir productivity. 3） The production characteristics of fracture wells are categorized into three stages: ① the fracture system acts as the high yield stage; ② the fracture system serves as the storage stage and plays the role of diversion; ③ the fracture's primarily function in diversion. This research significantly increases the proportion of high-yield wells in the fault-fracture reservoir, providing crucial insights for guiding efficient, ongoing exploration and development activities in the Mesozoic reservoirs on the southwest margin of the basin. This strategic approach enhances understanding and management of fault-fracture reservoirs, optimizing resource extraction and improving operational efficiencies.

Key words: southwest margin of Ordos Basin, fault-fracture reservoir, “binary four zones” model, development characteristics, high yield enrichment law