Quantitative evaluation of pore structure from mineralogical and diagenetic information extracted from well logs in tight sandstone reservoirs

This present study investigates the microscopic pore structure of tight sandstone reservoirs. Core samples, thin sections, scanning electron microscopy, X-ray diffraction, and mercury-injection curves were used to study the effects of several factors, such as mineral composition and organic carbon content and structures, on microscopic features in tight sandstone reservoirs and their effects on reservoir pore structure. The large variation in rock component content is one of the controlling factors that cause complexities in the diagenesis type and pore structure of the reservoir. Different rock mineral components and diagenesis types were identified in reservoirs with different types of pore structures and the test results suggest that they are the primary factors controlling reservoir pore structure. The rock mineral components of each reservoir were determined by multi-mineral analysis，while a comprehensive diagenetic coefficient was established and each factor's weight was determined by grey relational analysis. In this means, the effects of mineral components and diagenesis types on pore structure were adequately reflected. By quantitative characterization of these two main factors affecting the pore structure of the reservoir (rock composition and diagenesis), a new pore structure evaluation parameter was constructed based on the tight sandstone reservoirs properties in the study area. The presented method could provide technical support for the production of tight reservoirs and accurate prediction of favorable reservoirs, and also provide a new reference for the evaluation of pore structures of complex reservoirs.