Coupling Compositional Flow, Thermal Effects and Geochemistry Reactions when Injecting CO2 in a Carbonated Oil Field

The goal of this paper is to describe thermal effects on fluid flow and chemical reactions when dealing with a non isothermal oil reservoir. This situation may arise when the initial temperature state is changed by injecting a fluid whose temperature is different from the medium one. In this case, heat transfer should be taken into account during reservoir simulations.A synthetic hydrocarbon reservoir is used to model the oil production with an alternative injection of CO2 and de-sulphated sea water. The oil in place is modelled with 8 components and the mineralogy of the rock formation is composed of Calcite, Dolomite and Quartz. The reservoir being initially at 60 °C, several injection temperatures are assessed in order to simulate the heat transfer between injected and originally in-place fluids. Reservoir simulations are carried out by using IFP Energies nouvelles multi-phase thermal and compositional simulator COORESTM coupled with a geochemical software Arxim.By coupling only thermal effects and the multiphase flow, the study has shown that there are two compulsory effects on oil recovery mechanisms: the thermal expansion of the injected fluid (mostly for the CO2) and modifications of the oil mobility ratios due to the changes of the fluids viscosities consequent to the injection of a cold fluid into a hot reservoir.On the geochemistry part, the study has also shown that temperatures have a kinetic effect on the chemical reactions consequent to rock and fluids interactions. The higher the temperatures are, the faster the chemical reactions will be. Variations of reaction rates are quite significant on the chemical scenario as Calcite may dissolve twice faster between 60 °C and 15 °C.When using fully coupled compositional, heat transfer and geochemistry simulations, in addition to the effects described previously, we can observe that most of the chemical reactions occur around the well bore. The injection of CO2 and water with a different ion composition than the formation water induce modifications in the rock composition. The Calcite will rapidly dissolve releasing calcium ions that will be used to precipitate a part of Dolomite. The overall dissolution of minerals will imply an increase in porosity and permeability at a velocity depending of the injected temperature and improving so the injectivity of the injector well.