Acid‐Fracture Propagation Mechanisms and Controlling Factors in Interbedded Dolomite‐Limestone Carbonate Reservoirs

ABSTRACT The deep carbonate reservoirs of the Maokou Formation in the Sichuan Basin exhibit strong heterogeneity and complex fracture propagation behaviour, posing significant challenges for effective acid fracturing stimulation. To address these issues, this study conducted acid fracturing experiments under true triaxial stress conditions with layered stress loading, using synthetic dolomite–limestone composite samples. The investigation focused on the effects of interbed thickness, wellbore configuration and bedding orientation on fracture initiation and propagation. Results demonstrate that increasing dolomite thickness from 60 to 140 mm led to a 15.67% increase in breakdown pressure, with acid preferentially penetrating and etching the thicker interbeds. Vertical wells generated more complex fracture networks compared to horizontal wells, where fracture propagation was significantly constrained under high stress differentials. Under lateral bedding distribution, overburden stress resulted only in low‐angle fracture deflections, substantially inhibiting cross‐layer propagation. For thick‐bedded dolomite formations, higher pumping pressure is required to ensure effective fracture initiation; for formations with lateral bedding distribution, deflection techniques are necessary to secure vertical propagation; and for strongly heterogeneous reservoirs, vertical wells are preferred to generate complex fracture networks. These findings provide critical insights into the fracture mechanisms within interbedded carbonate reservoirs and offer direct theoretical and practical support for the optimisation of field‐scale acid fracturing designs and enhanced production strategies.