Abstract: In response to the difficulty of quantitative characterization of the fracture network sweep volume of sandwich-type shale oil volume fracturing in Qingcheng Oilfield, Ordos Basin, a fracture network stimulation volume prediction model is established by applying physical model experiments and mine field data and coupling key geological engineering parameters, and a multi-scale pore percolation model considering fluid pressure is established to quantitatively characterize the fracture network percolation volume based on rock microstructure and wettability, and a new concept of fracture network sweep efficiency is proposed to quantitatively evaluate the fracture network sweep volume. The study shows that the shale oil volume fractures generally show a strip-like fracture network with the main fractures dominating and branch fractures supplementing, and the shape is similar to a "cactus"; the main controlling factors affecting the sweep volume of the fracture network are fracturing fluid volume, fracture density, brittleness index, pumping rate, horizontal stress difference, reservoir thickness, and sand addition; the stimulation volume of fracture network is the main contributor to the fracture network sweep volume of the horizontal well volume fracturing. The percolation volume of fracturing fluid in the fracture network is mainly used to replenish the energy of the formation, the fracture network sweep efficiency of the typical platform is 33.2% to 63.6%, and the fracture network sweep volume needs to be further improved. The research results can provide a reference for the evaluation of the volume fracturing effect of shale oil horizontal wells.

Key words: shale oil, fracture network sweep volume, percolation model, fracture network sweep efficiency, Qingcheng Oilfield