Carbon Dioxide Deep Aquifer Isolated Two-phase Flow Simulation And Rock Physics Research

It seems certain that the change in CO₂ concentration in the atmosphere is due to human energy production from fossil fuels. The global warming issue has sparked public interest on all levels. To reduce CO₂ emissions, one must either reduce CO₂ production, or find alternative disposal schemes. Several different sequestration schemes — injection into deep oceans, un-minable coal seams, depleted oil reservoirs and saline aquifers, have been proposed to reduce atmospheric emissions. Sequestration of CO₂ by injection into deep geological aquifers appears to be the best choice in terms of resident storage time, storage capacity and proximity to emission cites.The Norwegian oil company, Statoil, is injecting approximately one million tonnes per year of recovered CO₂ into the Utsira Sand, a saline formation under the sea associated with the Sleipner West Heimdel gas reservoir. The large contrast in seismic impedence between water and supercritical CO₂ in Utsira sand has been successfully monitored with repeated surface seismic measurements in 1999,2001 and 2002. Based on these published time-lapse data, this thesis focuses on the developement of two-phase flow model and rock physics model in order to further characterize the CO₂ plume e.g. with respect to the distribution of CO₂ saturation in seismic section, the geophysical abnormity signature caused by immiscible pore fluids, and to find or analyse some new machanisms.Fluid flow simulation is performed using FEM (finite element methord) modeling for considering the THM couling effect on the two phase flow process. A coupled thermoporoelastic model of non-isothermal flow and deformation in elastic porous media with two immiscible porous fluids (CO₂ and groundwater) is presented, accounting for porosity change, compressibility and thermal expansion of convective heat flow. The govening equations are based on the equations of equilibrium, Darcy's law, Fourier's law and the conservation equations of mass and energy. Three phases and constituents (solid rock skeleton, liquid water and liquid or supercritical CO₂) are identified with no consideration of the supercritical CO₂ phase change in short time about saveral years after CO₂ injection. Thermal non-equilibrium between the phases is assumed throughout with a advantage in the convenience in model modifying to get the CO₂ phase changing effect. The simulating results can provide fluid pressures, relative saturation, and distribution of the fluids in the reservoir. The simulating code is validated on two BMT case with different codes from GEO-SEQ participate research teams.However, when CO₂ is injected underground, it forms fingers extending into the rock pores saturated with water, brine or petroleum. This flow instability phenomenon, known as viscous fingering, is significant for CO₂ sequestration because it will govern the available volume for CO₂ storage in the deep formation and the most important, from...