A theoretical study on changes in pressure and tracer concentrations taking into account pores containing immobile fluids in reservoir simulations

Abstract

The conventional reservoir simulation model has been extended. This extension is based on an assumption that the highly heterogeneous distribution of pores in reservoirs generates pores containing immobile fluids. The pores containing immobile fluids only allow the propagation of pressure change. The specific enthalpy and tracer concentrations in these pores are maintained at the initial values.

Attaching the pores containing immobile fluids on the outside of the porous medium defined in the conventional model, we assume that the total pore volume increases by a factor of α. The changes in tracer concentrations are controlled by the porosity of the original porous medium ϕ, whereas that in pressure is controlled by αϕ. Numerical experiments validate these dependencies of pressure and tracer concentrations.

An effective procedure for matching the extended simulation model to field observations is discussed in terms of the abovementioned dependencies. A further extension is described by taking into account the thermal decay of multiple tracers.