Seismic physical modeling study for the shale oil reservoir with complex lithofacies and meter-scale structures

There are various lithofacies with complex spatial patterns in shale oil reservoirs. The seismic reflections usually reveal the combination of sets of thin mud shales with various lithofacies. The seismic response characteristics of the lithofacies and the differences in seismic response of different lithofacies are still unclear, making the reservoir description difficult. The complex tectonic structures, diverse lithofacies, thin interlayers, fractures with various length scales, and various fracture development zones in the shale oil reservoir have placed very high demands on the design and construction method during the physical modeling of the shale oil reservoir. Facing preceding challenges, a physical modeling study on shale oil reservoir with complex lithofacies and meter-scale structures was carried out. The target is the shale oil reservoir of the ES4 s subsegment in the Jiyang depression. The complex physical model of a shale oil reservoir, with the thin stratigraphic layers and the complicated lithofacies and fracture patterns to date, was designed and constructed in a laboratory. In total, 25 combinations of materials were developed to simulate various lithofacies with different elastic parameters, and the error of the wave velocity simulation is less than 2.35%. The simulation of 1 m thick interlayers and the construction method for seismic physical models with meter-scale geologic structures was realized. The quality control analysis finds that the simulation accuracy of small-scale geologic structure, complex lithofacies, and fractures is relatively reliable. Based on the physical model of the shale oil reservoir, high-density and wide-azimuth seismic data are acquired. Preliminary data processing and analysis find that the model layers have clear reflection characteristics, providing reliable data for the next step of seismic characteristics analysis of complex lithofacies shale oil reservoir. The methodology has improved the capacity of seismic physical modeling to simulate complex oil and gas reservoirs, enabling the seismic physical simulation method to be applied in analyzing the commonly observed complex lithofacies, fractures, and meter-scale structures in unconventional oil and gas reservoirs.