An Experimental Investigation of Reaction-Transport Phenomena During Co2 Injection

Abstract

Abstract The injection of carbon dioxide in depleted petroleum reservoirs or in aquifers is a promising way to cope with the short-medium term issue of greenhouse gas emissions mitigation. Several coupled physical and chemical processes may occur during the injection depending on time and location within the reservoir. Far field regions are facing long term reaction in a situation where flow of gas and water at a reduced rate may induce near fluid-rock equilibrium. In contrast, near well-bore regions are subjected mainly to gas at a high flow rate where dissolution/reprecipitation phenomena may increase/decrease drastically the injectivity. The purpose of this study is to investigate experimentally the various situations in representative reservoir conditions with the objective of achieving knowledge and data for future physical and numerical modeling and reservoir numerical simulations of CO2 re-injection. Experiments consist in the co-injection of CO2 and brine in carbonate cores (limestone). The temperature and pressure conditions are such that the CO2 is in supercritical state. Results show that the flow rate and the composition of the fluids initially present in the core play a major role in the fluid-rock interaction leading to various non-uniform dissolution facies and in some cases to re-precipitation and permeability reduction. These phenomena have been observed and quantified using various non destructive techniques (NMR, CT-scanner) and chemical analyses of the producing fluids, leading to a comprehensive understanding of the coupled mechanisms taking place.