Exact Solution for Water Evaporation During CO2 Injection

Abstract

The objective of this study is to develop an analytical model for 1D gas-water flow with evaporation of water into the mobile gas phase. The evaporation rate is proportional to the fluid-fluid interfacial area, which is a function of the water saturation. Introduction of saturation-dependent potential allows reducing the 2 × 2 non-linear system of PDEs to one hyperbolic equation. The saturation distribution is obtained by non-linear method of characteristics. The first integral allows for explicit expression of the vapor concentration versus saturation. It was shown that typical properties of rock-CO2-water system, the evaporation time has order of magnitude of millions of pore volumes injected. Close match was observed between a series of three corefloods and the analytical model, and the tuned model coefficients belong to their common intervals. This validates the developed model for 1D gas-water flow with water evaporation into the injected gas.