Effect of fluid–shale interaction on hydraulic fracture effectiveness

The effectiveness of hydraulic fractures is one of the critical factors determining the production performance of shale oil wells. To investigate the influence of fluid–shale interaction during formation stimulation on the effectiveness of hydraulic fractures and shale oil production, first, a series of conductivity tests were performed on shale cores after soaking in different fluids, revealing the evolution rules of conductivity of propped fracture under different fluid-shale interaction mechanisms. Furthermore, by considering the fluid–shale interaction in the reservoir numerical simulation model, the impact of hydraulic fracture effectiveness evolution on shale oil well productivity and its differences in reservoirs with different permeability anisotropy were analyzed. The research results indicate that the softening of fracture surfaces caused by fluid-shale interaction causes fracture conductivity damage, and the longer the soaking time, the more severe the damage. Generally, the degree of damage on the fracture conductivity caused by water–shale interaction is higher than that caused by supercritical CO2 shale interaction under the same soaking time. When considering the damage of hydraulic fracture effectiveness caused by fluid–shale interaction, the production of shale oil wells is significantly reduced. For shale reservoirs with strong permeability anisotropy, the cumulative oil production loss caused by fluid–shale interaction is more severe than that with weak permeability anisotropy.