An experimental study of the rock mechanical properties in highly heterogeneous reservoir rocks of tight sandy conglomerates

ABSTRACT: Tight sandy conglomerates usually consist of tight sandstones in the matrix and gravels embedded in the matrix. With the development of horizontal well and hydraulic fracturing technologies, commercialized and continuous tight oil production has been achieved in several tight sandy conglomerate reservoirs. However, widely distributed gravels with various shapes, sizes, and mechanical properties in such reservoirs exhibit strong heterogeneities and make it difficult to accurately evaluate the rock mechanical properties, which consequently affects the efficacy of well planning and hydraulic fracturing design. This experimental study establishes correlations between physical and mechanical properties in tight sandy conglomerate reservoirs and investigates the effects of the gravels on the heterogeneity of physical properties in the formation. Tri-axial compression tests combined with P wave and S wave velocity measurements provide the static-dynamic correlations. Same samples then go through CT scans, where the pore structures, compression-induced fractures, and permeability isotropies are further quantified. As there is a lack of published lab data, this study enriches relevant data in the literature and improves the understanding of the mechanical and physical heterogeneities in conglomerates.