Numerical investigating oil-water flow in shale oil reservoirs accounting for fracture swarms and injected hydraulic fluids

The development of shale oil has transformed the global energy landscape by unlocking previously inaccessible resources through advancements in hydraulic fracturing and horizontal drilling. However, understanding the behavior of fracturing fluids within the reservoir remains a significant challenge. This study investigates the migration and distribution of fracturing fluids, focusing on unpropped fracture swarms generated during hydraulic fracturing. Using a reservoir simulation model calibrated to match fracturing treatment conditions, we analyze the oil-water two-phase flow and the pathways of injected fracturing fluids. Our findings reveal that unpropped fractures act as the primary storage for fracturing fluids, the pressure gradient generated by highconductivity fractures causes a portion of the fracturing fluid, originally directed toward the wellbore, to deviate and migrate into the matrix. Spontaneous imbibition, driven by capillary pressure, facilitates fluid entry into the matrix but does not enhance oil recovery. Additionally, water huff-and-puff processes were found ineffective in improving recovery due to the accumulation of water near the wellbore. Upscaling techniques, while useful in characterizing fracture swarms, demonstrated early-stage discrepancies in water cut, underscoring the need for variable saturation profiles. These insights into the complex oil-water flow mechanisms provide essential support for the efficient development of shale oil reservoirs.