The Determination of CO2 Storage Potential Parameters for the Real Depositional Environments

Abstract

Abstract A reliable and safe geological storage of CO2 must require a detailed characterization of the reservoirs which is usually consists of a huge amount of data. Often, this kind of information is accumulated and processed over many decades of subsurface exploration. Therefore, the regions of the intensive exploration, especially well established petroleum provinces, offer a good prospect for an industrial-scale deployment of CCS. The data gathered is incredibly useful for screening and evaluation of trapping mechanisms. The environments represents the largest share of geological conditions. They correspond to the submarine fan of the Achimov formation (AF), the barrier island of the Cherkashinsky (BR), the deltaic environment of the Tanopchinsky (DT) and the fluvial sediments of the Tyumen (FL). Every reservoir model corresponds to a sector of a larger regional model. About 20 parameters were varied in the study to evaluate the storage performance of the environments. The average reservoir permeability is tuned in a subset of cases to ensure reaching the full storage capacity at 50 years to normalize the fluid dynamics in time. The results testify that the saline aquifers in the fluvial environments appear to be not suitable for a large-scale CCS. They are characterized by low storage potential (Es>0.04) as well as low capacity and injectivity. Other environments (AF, BR and DT) are characterized by a better Es≼0.1. The barrier island depositional environments should be considered the most perspective for CCS, with Es occasionally exceeding 0.15. Approximately, 0.2-0.3 megatons of CO2 per 1 km2 of reservoir area can be stored in aquifers characterized by the effective thickness of 10-15m. An intriguing observation is that the BR exhibits the largest net-to-gross thickness, NTG, and the smallest number of non-reservoir intervals, NRI. At the same time, the worst environments for CCS are characterized by either small NTG (FL) or large NRI (AF). It can be expected that the formations characterized by the largest NTG and a relatively small NRI are best for the carbon storage. On the other hand, if NRI is 0, then the reservoir shows strong communication in the vertical direction. Due to the buoyancy, this can lead to a rapid CO2 accumulation and spreading in a narrow interval beneath the caprock and, thus, to a smaller Ev. The paper provides arguments for the selection of reservoirs belonging to certain depositional environments over others during screening process for carbon storage location. Storage efficiency, being the integral factor describing how big an area is required to store a given amount of CO2, is subdivided into factors and parameters. An approach is described for estimation of effects that depositional environment and reservoir engineering parameters produce on storage efficiency in CCS projects.