Although there are a number of mathematical modeling studies for carbon dioxide (CO 2 ) injection into aquifer formations, experimental studies are limited and most studies focus on injection into sandstone reservoirs as opposed to carbonate ones. This study presents the results of computerized tomography (CT) monitored laboratory experiments to analyze permeability and porosity changes as well as to characterize relevant chemical reactions associated with injection and storage of CO 2 in carbonate formations. CT monitored experiments are designed to model fast near well bore flow and slow reservoir flows. Highly heterogeneous cores drilled from a carbonate aquifer formation located in South East Turkey were used during the experiments. Porosity changes along the core plugs and the corresponding permeability changes are reported for different CO 2 injection rates and different salt concentrations of formation water. It was observed that either a permeability increase or a permeability reduction can be obtained. The trend of change in rock properties is very case dependent because it is related to distribution of pores, brine composition and thermodynamic conditions. As the salt concentration decreases, porosity and the permeability decreases are less pronounced. Calcite deposition is mainly influenced by orientation, with horizontal flow resulting in larger calcite deposition compared to vertical flow.

No abstract

Sequestration of carbon dioxide in geological formations is an alternative way of managing extra carbon. Although there are a number of mathematical modeling studies related to this subject, experimental studies are limited and most studies focus on injection into sandstone reservoirs as opposed to carbonate ones. This study describes a fully coupled geochemical compositional equation-of-state compositional simulator (STARS) for the simulation of CO 2 storage in saline aquifers. STARS models physical phenomena including (1) thermodynamics of sub-and supercritical CO 2 , and PVT properties of mixtures of CO 2 with other fluids, including (saline) water; (2) fluid mechanics of single and multiphase flow when CO 2 is injected into aquifers; (3) coupled hydrochemical effects due to interactions between CO 2 , reservoir fluids, and primary mineral assemblages; and (4) coupled hydromechanical effects, such as porosity and permeability change due to the aforementioned blocking of pores by carbonate particles and increased fluid pressures from CO 2 injection. Matching computerized tomography monitored laboratory experiments showed the uses of the simulation model. In the simulations dissolution and deposition of calcite as well as adsorption of CO 2 that showed the migration of CO 2 and the dissociation of CO 2 into HCO 3 and its subsequent conversion into carbonate minerals were considered. It was observed that solubility and hydrodynamic storage of CO 2 is larger compared to mineral trapping.

TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractStarted as an EOR technique to produce oil, injection of carbon dioxide which is essentially a greenhouse gas is becoming more and more important. Although there are a number of mathematical modeling studies, experimental studies are limited and most studies focus on injection into sandstone reservoirs as opposed to carbonate ones. This study presents the results of computerized tomography (CT) monitored laboratory experiments to characterize relevant chemical reactions associated with injection and storage of CO 2 in carbonate formations. Porosity changes along the core plugs and the corresponding permeability changes are reported for differing CO 2 injection rates and with differing salt concentrations. CT monitored experiments are designed to model fast near wellbore flow and slow reservoir flows. It was observed that permeability initially increased and decreased for slow injection cases. As the salt concentration decreased the porosity and thus the permeability decrease was less pronounced. The experiments were modeled using a commercial simulator where solution and deposition of calcite were considered by means of chemical reactions. The calibrated model was then used to analyze field scale injections. It was observed that solubility storage of CO 2 is larger compared to mineral trapping.

No abstract