CO2 Sequestration Modeling Using Pattern Recognition and Data Mining; Case Study of Sacroc Field

Capturing carbon dioxide (CO₂) from large point sources, such as fossil fuel power plants, and depositing it in a geological formation is considered as an efficient way to decrease the impacts of concentrations of CO₂ in the atmosphere. The main concern for a geologic CO₂ sequestration is sustained confinement of the injected CO₂ for long time (hundreds of years). For selection of the proper underground storage and keeping track of the CO₂ plume movement, it is essential to use an appropriate multiphase flow dynamic reservoir model. The Numerical Reservoir Simulator is an appropriate tool to accomplish this task.

SACROC unit, an oil field located in western Scurry County in Texas, is one of the oldest and largest CO₂ injection fields in the US. Initially in 1954, water was injected with the purpose of maintaining the reservoir pressure, and later in 1972 injection of carbon dioxide started to displace the oil in miscible process.

The intricacies of simulating multiphase flow, having large number of time steps required to study injection and post injection periods of CO₂ sequestration, highly heterogeneous reservoir, large number of wells, etc. will lead to having a complicated reservoir model. The time needed to run a single realization for such a reservoir exceeds hours even using a very high computational power. On the other hand, a thorough understanding of CO₂ sequestration process requires multiple realizations of the reservoir. Consequently, using a conventional numerical simulator makes the computational cost of the analysis too high to be practical.

In this paper, we examine the application of a relatively new technology (Surrogate Reservoir Model – SRM) as an alternative to solve the aforementioned problems. SRM is a prototype of full-field reservoir simulation models. An important feature of SRM is its fast analysis and generation of outputs in a very short time period with reasonable accuracy. These characteristics make SRM a unique tool in CO₂ sequestration modeling. This paper discusses the development of an SRM for a CO₂ storage project in SACROC unit that would facilitate fast track modeling and uncertainty analysis of short and long term pressure and saturation distribution.