Diagenetic Controls on the Reservoir Quality of Fine-Grained “Tight” Sandstones: A Case Study Based on NMR Analysis

Abstract

Accurate description of diagenetic controls on reservoir quality in “tight” sandstones can be difficult because of the inherent fine grain size and complex components of such oil reservoirs. In this study, petrological techniques and nuclear magnetic resonance (NMR) analysis were applied to fine-grained tight sandstones with varying grain sizes in order to reveal the diagenetic controls on reservoir quality. Results show that macropores in tight sandstones occur mainly as intergranular and dissolution pores, whereas micropores are distributed within ductile rock fragments, clay, and mica minerals, as well as occurring as dissolution micropores. Pore size distribution (PSD)/T2 spectra display three distribution patterns: (i) a macropore-dominant bimodal distribution, (ii) a macropore–micropore bimodal distribution, and (iii) a micropore-dominant skewed distribution. A decrease in grain size correlates with weaker framework support of particles and thus more intensive mechanical compaction, resulting in the...