Multi-scale Imaging and Simulation of Structure, Flow and Reactive Transport for CO2 Storage and EOR in Carbonate Reservoirs

Abstract

As we continue to use fossil fuels for our energy supply, the concentration of CO2 in the Earth’s atmosphere is likely to continue to increase. It has been shown that this is correlated with an increase in the temperature of the atmosphere and potential associated climate change. To mitigate this problem, Carbon Capture and Storage (CCS) has been mooted over the past decade. In this chapter, we will focus on CO2 storage in downhole rock formations. Rock formations suitable for storage include saline aquifers and depleted oil and gas reservoirs. Also coal bed methane (CBM) reservoirs may be suitable for storage, but we will not consider these in the current chapter. In the case of saline aquifers, we consider only the storage of CO2. In the case of depleted oil/gas reservoirs, the storage of CO2 can be combined with Enhanced Oil Recovery (EOR). This may lead to a more favorable economic scenario and has recently been coined as CCUS (Carbon Capture and Utilized Storage). In particular we will focus in this chapter on carbonate reservoirs. Sandstone reservoirs have been relatively well studied. However, much less is known about the storage properties of carbonate rocks, which have very different petrophysical and flow properties. Moreover, carbonate rocks constitute a significant fraction of existing depleted hydrocarbon reservoirs. Our aim is to study the pore scale properties of carbonates and upscale these to the core and field scales. First, carbonates have a very different structure from sandstones, associated with their composition and diagenesis. Carbonates usually have a much broader pore size distribution (PSD) than sandstones with extensive microporosity (Cantrell and Hagerty 1999). In addition, carbonates are often naturally fractured (Ameen et al. 2010). This leads to a broad range of heterogeneity as a function of length scale, in comparison …