Depositional Environments Being Investigated by the National Energy Technology Laboratory NETL for Potential Geologic Storage of CO₂

A need exists for further research on carbon sequestration technologies to capture and store carbon dioxide (CO₂) from stationary sources that would otherwise be emitted to the atmosphere. Carbon Capture and Storage (CCS) technologies have the potential to be a key technology for reducing CO₂ emissions and mitigating global climate change.

Deploying these technologies on a commercial-scale will require geologic storage formations capable of (1) sequestering large volumes of CO₂, (2) receiving CO₂ at an efficient and economic rate of injection, and (3) retaining CO₂ safely over extended periods. Eleven major types of depositional environments, each having their own unique opportunities and challenges, are being considered by the U.S. Department of Energy (DOE) for CO₂ storage. These different classes of reservoirs include deltaic, coal/shale, fluvial, alluvial, strandplain, turbidite, eolian, lacustrine, clastic shelf, carbonate shallow shelf, and reef. Basaltic interflow zones are also being considered as potential reservoirs.

DOE has recently completed a study which investigates the geology, geologic reservoir properties and confining units, and geologic depositional systems of potential reservoirs and how enhanced oil recovery and coal bed methane are currently utilizing CO₂. It looks at the classes of geologic formations that have been identified as having the potential to be CO₂ reservoirs, their distribution and potential storage volumes.

This study also discusses the efforts that DOE is supporting to characterize and test small and large scale injections of CO₂ into these different classes of reservoirs. These tests are important to better understand the directional tendencies imposed by the depositional environment that may influence how fluids flow within these systems today, and how CO₂ in geologic sequestration is anticipated to flow in the future. Although diagenesis has modified fluid flow paths during the intervening millions of years since they were deposited, the basic architectural framework created during deposition remains. Geologic processes that are working today also existed when the sediments were initially deposited. Analysis of modern day depositional analogs, evaluation of core samples, outcrops and well logs from ancient subsurface formations give an indication of how formations were deposited and how fluid flow within these formations is anticipated to flow.