The starting point to simulate enhanced oil recovery (EOR) or enhanced gas recovery (EGR) processes is to understand the physics involved in each enhancement technology.
When a special solution is introduced into an existing oil or gas field, the solution interacts with the resident phases such as rock, oil, gas and water. As a result of these inter-actions, behaviours of both each individual phase and inter-phases may be modified.
We define EOR/EGR operations as the coupled thermal, hydraulic, chemical, and mechanical (THMC) processes in terms of the correctly coupled multiphysics. The inclusion of cross-couplings is the key to mathematically formulating the coupled multiphysics.
Cross couplings are the local rules that define how interactions between different processes take place. The mathematical framework of multiphysics is same for all EOR/EGR technologies, while the cross-couplings differ from one to another.
UWA's Reservoir Engineering Group has developed a multiple-processes characteriser that allows the user to implement different cross-couplings for each individual EOR or EGR technology.
As an example, we applied our tool to understand the role of the co- and counter-diffusive properties of CO2 and CH4 in coal; this has important implications for methane recovery (ECBM) and CO2 sequestration in coals, as well as related issues of gas outbursts during mining.
This study addresses how the coal-gas interactions affect CO2 injectivity, in particular the roles of coupled coal deformation, gas flow and the CH4-CO2 counter-diffusion on the evolution of transport and mechanical properties, and therefore on ECBM recovery.
Results of a bench-mark study are shown in Figure 1.