Numerical simulation of the dynamic migration mechanism and prediction of saturation of tight sandstone oil

Abstract

Quantitative characterization of tight sandstone oil migration and accumulation is an emerging research frontier in the field of oil and gas exploration. In this study, a conceptual model containing multiple basic geological elements is developed, and a nonlinear seepage numerical model for tight sandstone oil migration and accumulation is established. The effects of the slip effect, overpressure driving force, buoyancy, and capillary force on the migration and accumulation of tight oil are examined. The results showed that (1) the differences in oil migration and accumulation between tight and conventional reservoirs are reflected in the growth mode of oil saturation, distribution characteristics of oil and water, and extent of the effect of the formation dip angle; (2) the slip effect has a significant impact when the average pore throat radius is less than 150 nm and the overpressure driving force and capillary force are the main mechanical mechanisms controlling oil migration and accumulation in tight sandstone, while the coupling effect of buoyancy, capillary force, and overpressure driving force controls the upper and lower limits of oil saturation. Finally, a dimensional and dimensionless identification chart for rapidly predicting the oil saturation of tight sandstone is proposed and verified using the measured data. This study provides a basis for analyzing the migration and accumulation mechanisms of tight sandstone oil and a new approach for predicting oil saturation. Additionally, we developed digital and visual analysis methods for the migration results, enriching the expression of the dynamics of hydrocarbon accumulation.