Research on Reconstruction Technology of Highly Heterogeneous Complex Lithology Reservoir

Abstract The Permian Maokou Formation reservoirs in the Sichuan Basin are typically characterized by deep burial depths, complex lithologies, diverse reservoir types, and strong heterogeneity. Under formation temperature conditions, the reaction rates between dolomite and limestone with acid show significant differences, leading to substantial variations in the lengths of acid-etched fractures developed in different lithologies. This situation makes it challenging to achieve uniform transformation, resulting in poor transformation effectiveness. In this paper, based on rock composition analysis experiments on rock samples in the working area, and the cloud-limestone interactive reservoir is divided into three categories according to the dolomite content. Aiming at different dolomite limestone content, the optimal fracture shape, optimal fracture control volume and maximum gas production capacity are carried out through laboratory experiments such as acid rock reaction kinetics and large physical model. It is evident that achieving efficient stimulation of dolomitic-limestone interaction reservoirs necessitates the determination of optimal construction parameters. For weakly dolomitized reservoirs, implementing a mesh-joint acid fracturing process is recommended to mitigate the reaction rate and expand the fracture-controlled volume. The multi-fracture acid pressing process is used to slow down the reaction rate, increase the fracture action distance and increase the fracture control range. For strongly dolomitized reservoirs, the long-fracture acid fracturing process is employed to enhance non-uniform etching and create deep fractures while maintaining a specific effective distance, thereby further improving conductivity.