Numerical Simulation of Foamy Oil Stability Using Natural Gas Huff and Puff for Ultra-Deep Heavy Oil Reservoir

Abstract

The nature of injected gas dispersion in oil distinguishes foamy oil behavior from conventional heavy oil behavior. Unlike normal two-phase flow, it involves flow of dispersed gas bubbles with pseudo single phase. This paper presents the results of a numerical simulation study of the stability of foamy oil created by liberation of dissolved gas during natural gas huff and puff process. Through the history matching of labs test conducted by three series of various core tubes in numerical simulation, foamy oil impactions on recovery were discussed based on vertical heterogeneous model. The effects on the stability of foamy oil flow behavior were investigated by mobility ratio, viscous to gravity ratio, layer permeability contrast, vertical to horizontal permeability ratio and the transverse dispersion number in the paper. The results show that foamy oil stability increases with higher oil viscosity, higher injection gas density. The oil recovery decrease with the mobility ratio and the layer permeability contrast, while the oil recovery increase with the vertical to horizontal permeability ratio. This work demonstrates that the transverse dispersion number should be used to assess vertical or microscopic sweep efficiency. The study indicates that foamy oil in porous media during production is unstable, but it will be huge potentials to apply natural gas huff and puff for ultra-deep heavy oil reservoirs.