Taura, U; Mahzari, P; Sohrabi, M; (2017) A new methodology for estimation of three-phase relative permeability functions in heavy-oil displacement involving instability and compositional effects. In: Society of Petroleum Engineers - Nigeria Annual International Conference and Exhibition 2017. (pp. pp. 1028-1047). Society of Petroleum Engineers: Lagos, Nigeria.

Text Mahzari 1 SPE-189178-MS.pdf - Published Version Access restricted to UCL open access staff Download (2MB)

Abstract

Simultaneous three-phase flow of gas, oil and water is a common phenomenon in enhanced oil recovery techniques such as Water-Alternating-Gas (WAG) injection. Reliable reservoir simulations are required to predict the performance of these injections before field application. However, most commercial simulators are based on Darcy-type formulation requiring the concept of relative permeability. Generally, three-phase relative permeabilities are calculated from empirical correlations, which are based on two-phase relative permeability. However, heavy oil displacement by gas or water can lead to viscous fingering due to the unfavourable mobility ratio between heavy oil and the displacing fluid. In addition, the injection soluble gases such as CO2 can result in compositional effects. Estimation of three-phase relative permeability under such conditions are extremely complex and using conventional techniques for the estimation can lead to erroneous results. We used the result of three coreflood experiments carried out on a core to generate two-phase and three-phase relative permeability data using an improved history matching methodology that takes into account the instability and the compositional effects in the estimation processes. The results show that a simultaneous CO2 and Water injection (CO2-SWAG) can be adequately matched using a secondary gas/liquid and a tertiary oil/water relative permeabilities. This is because contrary to WAG in conventional oil recovery, where gas and water open up separate saturations paths, in this case, the water follows the gas saturation path due it's lower resistance as a result of the CO2 dissolving in the oil and reducing the oil viscosity. It is also important to include Pc even in high permeable porous media as we observed that the inclusion of capillary pressure dampened the propagation of the viscous fingers and hence helped the front to become stabilised leading to a better sweep efficiency.

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