Abstract: At present, most simulations of hydraulic fractures are conduced based on the assumption of smooth parallel plates, ignoring the effects of the morphology of the fractures on acid etching behaviors and fluid diversion capacity. A self-developed device named "acid pressure test system for fracture fluid diversion" was used to simulate smooth and rough fractures, respectively, with smooth and rough plates to study the characteristics of acid etching behaviors and diversion capacity of the two types of fracture morphology with different acid injection volumes and periods. The results show that the tortuosity of the fracture profile increased after acid etching for smooth fractures, whereas the opposite was observed for rough fractures, as acid etching reduced the peaks and deepened the troughs. Increasing the acid injection volume or period led to significantly larger change in elevation, fracture width, acid dissolution amount, and diversion capacity for rough fractures than for smooth fractures, whereas the former had not only better retention ability of fluid diversion, but also higher sensitivity to changes in acid injection parameters. In conclusion, the assumption of rough plates is beneficial for realistically evaluating the diversion capacity of acid pressure fractures under reservoirs, thus improving the targetedness of the acid pressure scheme design and the acid pressure effect.

Key words: hydraulic fracture morphology, rough fracture, smooth fracture, acid etching, diversion capacity