Rock Physics Modeling of CO2 Bearing Reservoir Rocks

AbstractCO2 capture and storage (CCS) is a technique to reduce CO2 emission, and CO2 is also used in EOR (enhanced oil recovery). It may increase oil production by 15–25% from an oil field. In this paper we present how to deal with the seismic response due to CO2 injection. To understand the seismic response due to CO2 flooding requires knowledge of the distribution of CO2 in brine, viscous loss due to CO2 and dissolution of CO2 in brine. Furthermore, the basic principle for EOR methods by CO2 is that high solubility of CO2 increases the density and lowers the viscosity at reservoir conditions of the oil, thus improving the oil mobility and the efficiency of water flooding. However, the viscous losses during the fluid flow are responsible for seismic wave attenuation. Moreover, when injecting CO2 into the water-saturated sample, some CO2 may be dissolved in the water. The Gassmann and Reuss or Gassmann and Voigt method may be used to calculate CO2 saturated seismic properties. Considering the significant differences between velocity values in these two methods, a large uncertainty is associated with fluid-saturation estimation from seismic data. I provided the rock physics model to calculate the CO2 saturated seismic properties to understand the seismic response due to the CO2 flooding. This model was tested laboratory measured data of sandstone from Lei and Xueb (2009) and carbonate from Wang et al. 1998. Modeling results provided us the viscous loss and dissolution of CO2 effects to calculate the CO2 saturated seismic properties. This model may be also used to calculate the accurate hydrocarbon production during the EOR method by CO2 injection.