Weyburn oilfield core assessment investigating cores from pre and post CO2 injection: Determining the impact of CO2 on the reservoir

- Comparing analytical data in this paper from pre-CO2 and post-CO2 cores indicates there are no significant mineralogical changes from the injected CO2, in the portion of the reservoir where the observation well was drilled.
- There seems to be no increase in porosity or permeability, when compared to previously drill wells, indicating that ionic trapping is not occurring at location of the observation well.
- The recently drilled wells have however provided a rare opportunity to directly study samples of reservoir rocks exposed to the CO2 flood for over a decade, and provide some potential calibration of previous research.

The purpose of this paper is to detail a mineralogical examination of core samples obtained from a recently drilled well in the Weyburn oilfield in southern Saskatchewan, Canada. The research was undertaken as part of the Saskatchewan CO2 Oilfield Use for Storage and EOR Research project (SaskCO2USER) managed by the Petroleum Technology Research Centre (PTRC), and jointly funded by the US Department of Energy and the Saskatchewan Government. The SaskCO2USER program has built on over a decade of research by the IEA GHG Weyburn-Midale CO2 Monitoring and Storage Project (WMP).The WMP included several studies of the geochemical evolution of the reservoir in response to CO2 injection through a combination of predictive modelling, fluid sampling and laboratory assessments. The recently drilled wells have however provided a rare opportunity to directly study samples of reservoir rocks exposed to the CO2 flood for over a decade, and provide some potential calibration of previous research.This research utilized SEM, QEMSCAN, cadotholuminescence, and EDS mapping to determine if there has been any change on the mineralogical framework in the reservoir over a decade of CO2 injection. Previous research has interpreted that ionic trapping has been occurring in the Weyburn reservoir since a year after injection. Although various WMP studies made the interpretation that dissolution and mineral trapping of injected CO2 will be active processes in the Weyburn field. This study found that there were no significant mineralogical changes in the samples analyzed from the recently drilled observation well.