A novel score system to evaluate carbonate reservoir combining microscale and macroscale parameters

Abstract

The central Sichuan Basin, located in western China, holds great significance in terms of hydrocarbon production, especially in relation to complex carbonate reservoirs, notably the Qixia Formation of the Middle Permian epoch. However, the comprehensive evaluation of this geological formation presents considerable challenges due to complex lithology, limited availability of reservoir property data at various scales, inadequacies in data integration, and the absence of a reliable reservoir ranking system for development decision making. Previous studies primarily relying on conventional data at the reservoir level, such as well logs and geological information, have proven insufficient in accurately characterizing the reservoir. This is especially evident without precise lithological information and detailed knowledge of microscale properties, which are crucial for effective reservoir evaluation. To address these challenges, this study integrates advanced technologies like X-ray diffraction, micro-CT and scanning electron microscope (SEM) techniques in digital drill cutting analysis at the microscale. A novel scoring system has been developed using a prominent component analysis (PCA) approach and an expert scoring system, which incorporates existing conventional well log data and digital cutting analysis. This scoring system has been validated using actual production data, thus establishing a robust evaluation methodology for assessing the exploration potential and optimizing development strategies for carbonate gas reservoirs in the Qixia Formation. The innovative approach, which incorporates parameters at both micro- and macroscales, holds promising potential in facilitating future exploration and development efforts.