Assessing CO2 EOR in different areas of a field with different rock and fluid properties requires proper dynamic reservoir modelling. Good SCAL data is a key input to the dynamic model. Consequently a comprehensive SCAL program was designed for a super giant carbonate reservoir, onshore Abu Dhabi, for modeling CO2 EOR process in secondary & tertiary conditions. A careful selection of the core material based on a Petrophysical Group (PG) review was performed to make the experiments representative of key areas of the field in which CO2 flood is planned or studied.
Laboratory experiments were designed at full reservoir conditions with H2S oil bearing, and to assess possible impact of H2S on displacement efficiency. Water-oil relative permeability tests showed insignificant impact of H2S, compared with non-H2S tests on cores of different PG's. Injectivity issues and importance of brine composition on water mobility were identified. Trapped gas to water and oil were also mapped successfully.
The comparative analysis of CO2 EOR flooding scenarios using long composite cores with continuous CO2 injection and CO2 WAG were also performed. They indicate higher displacement efficiency with continuous CO2 injection. Tests were also conducted on composites with non-H2S live crude, representative of reservoir zones with little or insignificant presence of H2S.
This study indicated for the first time in the published literature, the impact of H2S in water-oil relative permeabilities of carbonates at full reservoir conditions. The gas process displacement efficiency tests also verified negligible impact of H2S (up to 12%) in CO2 EOR 1D core floods.