Influence of filling characteristics on rock physical properties of deep carbonate reservoirs based on digital rock modeling

Abstract

Deep carbonate reservoirs are rich in oil and gas resources and are important targets for exploration. This study focuses on the Maokou Formation carbonate reservoir in the Sichuan Basin, which exhibits significant heterogeneity, complex karst characteristics, and filling phenomena. Due to the limited number of carbonate samples with representative filling characteristics and the difficulty of characterizing different types of fillings with similar densities using high-precision X-ray computed tomography, the rock physical properties of carbonate rocks with different filling minerals in the Maokou Formation reservoir are unclear. This makes it difficult to establish a system for the reservoir’s physical properties and fluid-sensitive parameters. This study integrates thin-section and image analyses to statistically characterize the filling minerals and proposes two approaches for constructing 3D digital rock models that incorporate karst and filling features of the Maokou Formation reservoir. Additionally, accurate P-wave velocity (Vp) and S-wave velocity (Vs) for different types of fillings were obtained using rock-physics experiments, providing precise input parameters for digital rock simulations. Several typical samples were selected to conduct acoustic experiments under varying confining pressures to measure Vp and Vs. This study analyzed the elastic properties of the rock under different mineral-filling proportions, filling orientations, and fluid-filling characteristics in the Maokou Formation carbonate reservoir, providing support for the extraction of the reservoir’s physical properties and fluid-sensitive parameters, as well as for quantitative reservoir prediction.

Keywords

Deep carbonate reservoirs / Filling characteristics / Digital rock / Rock-physics experiment / Numerical simulation

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