Geologic Sequestration of CO2 in a Depleted Oil Reservoir: An Overview of a Field Demonstration Project

Abstract

Abstract Sequestration of Carbon dioxide (CO2) in deep, geologic formations is one of the options currently being studied to mitigate the amount of CO2 released to the atmosphere. Depleted oil and gas reservoirs are one of the geologic targets considered for sequestration. Even though CO2 is currently being used in the enhanced oil recovery operations, injection of CO2 in depleted oil reservoirs as a carbon sequestration strategy needs validation. This paper provides an overview of the first U.S. field test of CO2 sequestration in a depleted oil reservoir, sponsored by the United States Department of Energy. The main objective of the project is characterization of CO2 migration through an integrated study that includes, field/laboratory experiments and numerical simulations. A small-scale field experiment was conducted whereby approximately 2100 tons of CO2 was injected in the West Pearl Queen Field, NM over a two-month period. Migration of CO2 was monitored using high-resolution 4-dimensional surface seismic surveys as well as downhole pressure monitors. Comparison of pre-injection and post-injection surveys indicates presence of an anomaly within the vicinity of the injection well, which could be resulting from injected CO2. After a 6-month soaking period CO2 was vented from the injection well. The amount of reservoir fluids produced during venting was monitored. A number of samples of reservoir fluid and gas were collected for compositional analyses. Changes in chemical compositions of fluid samples were observed indicating interaction between CO2 and reservoir fluids. The field experiment data are currently being integrated along with laboratory experiment data and numerical simulations to determine reservoir response to CO2 injection and to perform long-term fate calculations for such CO2 sequestration operations.