Three-Phase Flow in Field-Scale Simulations of Gas and WAG Injections

Abstract

Three-phase flow is present in many oil recovery processes of interest to the oil industry. It occurs in processes such as primary production below bubble point pressure in reservoirs with water drive, in gas or water alternating gas (WAG) injection into waterflooded reservoirs, in thermal oil recovery, and in surfactant flooding. Despite its common occurrence, our ability to reliably model three-phase flow using numerical simulation is questionable. This paper shows the importance of three-phase flow at typical oil field conditions. It also shows the uncertainties in the predictions of oil recovery due to the three-phase relative permeability model. Numerical simulations of immiscible gas and WAG injection into a waterflooded one eighth of a five-spot were performed to determine the importance of the three-phase flow at conditions that are of interest to the oil industry. Consistent oil-water imbibition and oil-gas drainage relative permeability and capillary pressure were derived for this purpose, including a new form for imbibition capillary pressure. Dimensionless scaling groups for three-dimensional three-phase flow in porous media were developed. The scaling groups were used to design simulations at various conditions of gravity, viscous and capillary force interactions. In addition, several simulations were made to determine the uncertainty of the results due to the model for three-phase relative permeabilities. The results of this study show that there is a significant uncertainty associated with the selection of the three-phase relative permeability model for field scale simulations of gas and WAG injections. This uncertainty is translated into doubtful simulation results in terms of distribution of the fluids inside large volumes of the reservoir, total oil recovery, and fluids production rates. It is shown that additional oil recovery due to gas injection after a waterflood can be different by a factor of two depending on the model for three-phase relative permeability. It is also shown that the producing gas oil ratio (GOR) varies considerably depending on the model for three-phase relative permeability, while maintaining the same two-phase relative permeabilities. Accurate predictions of oil recovery in processes that exhibit three-phase flow need more rigorous models for three-phase relative permeability. Large three-phase flow regions were present for most of the conditions simulated. The size of the three-phase flow regions ranged from 20% to 80% of the volume of the reservoir. The size of the three-phase flow region was a strong function of the kro model used. Thus, an argument asserting that only a small part of the reservoir is affected by the uncertainties in the three-phase relative permeability model is not supported by these results.

Operator Splitting for Three-Phase Flow in Heterogeneous Porous Media

“…We present an operator splitting technique for the numerical solution of a highly nonlinear system of differential equations modeling three-phase flow through heterogeneous porous media. Three-phase flow in porous media is important in a number of scientific and technological contexts, including enhanced oil recovery [8][9][10][11][12][13][14], geological CO 2 sequestration [15], and radionuclide migration from repositories of nuclear waste [16,17].…”

Analytical solutions for surfactant‐enhanced remediation of nonaqueous phase liquids

“…Figure 13 also shows that the MHE and NSH conservation laws result in virtually indistinguishable recovery curves after 0.75 PVI for injection composition O, while the recoveries when the SH conservation law applies are always smaller than the NSH conservation law recoveries. The work of Guzman et al [1994] reported similarly large differences in oil recovery from two relative permeability models with a fully immiscible three‐phase system.…”

“…Many researchers have examined the numerical simulation of multiphase flow for both oilfield [e.g., Giordano and Salter , 1984; Guzman et al , 1994] and groundwater applications [e.g., Delshad et al , 1996; Falta , 2003; Kaluarachchi and Parker , 1990; Panday et al , 1995]. Although simulators are essential to predict the potential for success of a SEAR project, there are currently few benchmark analytical solutions to use in validating simulations of three‐phase partially miscible flow [ Giordano and Salter , 1984; LaForce and Johns , 2005].…”

Computational fluid dynamic simulation of multi-phase flow in fractured porous media during water-alternating-gas injection process

“…Cyclic dependency of the three-phase hysteresis permeability becomes important in tertiary oil recovery processes such as WAG injection and cyclic steam stimulation (CSS) processes (Fatemi, 2015). Simulation studies showed remarkable uncertainties when applying three-phase relative permeability models in gas and WAG injections at field scales (Guzman et al, 1994). The simulation results of oil recovery with and without including hysteresis revealed that a higher oil RF is obtained by incorporating hysteresis effect in relative permeability correlations, compared to the no-hysteresis case (Ghomian et al, 2008).…”