Enrichment factors and sweep spot evaluation of Jurassic tight oil in central Sichuan Basin, SW China

Abstract

The secondary migration mechanism, enrichment factors of Jurassic tight oil in central Sichuan Basin were well investigated through physical simulation experiment of reservoir formation, casting and fluorescent thin sections, field emission scanning electron microscope (FESEM) and environment scanning electron microscope (ESEM). The results show that migration of Jurassic tight oil in central Sichuan Basin is a low-velocity non-Darcy flow through low-efficient migration path under the huge migration driving force, and has three migration and seepage stages, i.e. viscous flow stage, nonlinear seepage stage, and quasi-liner seepage stage. Microscopically, the migration pathway of tight oil is the pore-fracture composite conduction; macroscopically, the migration mode of tight oil is the large-scale short–distance migration. Distribution of favorable zones of tight oil is controlled by distribution of high-quality source rocks. The hydrocarbon-generation strength of 0.4 × 106 t/km2 can be as a threshold to determine favorable zone of tight oil in the study area. The reservoirs with high permeability and high porosity can form tight oil sweet spots, and the development degree of fractures is closely related to well with high yield of tight oil well. Keywords: Migration pathway, Migration driving force, Non-Darcy seepage, Pore-fracture composite conduction, Tight oil sweep spot, Jurassic tight oil, Central Sichuan Basin