Gravity drainage in a fissured reservoir with fluids not in equilibrium

Abstract

If a matrix block in a fractured reservoir is surrounded by gas, the gravity forces tend to expel the oil from the matrix and the capillary forces tend to retain the oil. If the liquid and the gas are not at thermodynamic equilibrium, a lowering of the interfacial tension and a swelling of the liquid may improve the liquid recovery. Experiments performed with ternary mixtures of hydrocarbons (C 1− n C 4− n C 10) under simulated reservoir conditions show that the oil recovery by gravity drainage increases if the content of intermediate components in the gas or in the liquid phase increases. This phenomenon has been confirmed by numerical simulations using compositional models.