Capacity and Constraints for Carbon Dioxide Sequestration in Aquifers and Depleted Oil/Gas Reservoirs in Carbonate Environment

Abstract

AbstractProduction of oil/gas to meet the increasing energy needs results in generation of significant amount of CO2. This study presents results of experimental and simulation work to understand opportunities and challenges in sequestering CO2 in carbonate rocks typical of aquifers and oil/gas reservoirs in the Middle East. CO2 corefloods were conducted in samples from carbonate analog outcrops to simulate sequestration process, and, changes in the pore-space due to dissolution/precipitation were quantified by time lapse CTscans and measurement of relative permeabilities. Density and compressibility of CO2 and Solubility in reservoir brines was measured to calibrate predictive models and used in simulation studies.Objective is to reliably calculate sequestration capacity available in aquifers and depleted reservoir in a region, and to evaluate the long-term stability of seals in such systems. Experimental results facilitate reliable simulation studies which are very important for determining how much CO2 can be sequestrated. Such studies also lead to understanding of potential leaks due to interaction of CO2 with carbonate minerals of sealing formations.Density and compressibility measurements of CO2 are reported at up to 5000 psia and 250 F. The results show good agreements with available predictive models and were used to calibrate parameters in such models. CT-scans and petrophysical properties of core samples show dissolution in some pores but precipitation in other pores of carbonate matrix. Simulation study reports ranges for storage capacity in tones/acreft.The results of this study are directly applicable for evaluating CO2 sequestration opportunities in Qatar, Middle-East since the outcrop samples studied are analog for Arab and Khuff Formations, which hold most of the petroleum reserves in the Middle-East. CO2 properties and its interaction with carbonate matrix are significant for CO2 sequestration study anywhere.