Monitoring the reservoir geochemistry of the Pembina Cardium CO2 monitoring project, Drayton Valley, Alberta

The Pembina Cardium CO2 Monitoring Project in central Alberta was built to assess the Cardium formation’s storage potential for CO2 and stimulate oil production. Three baseline trips and 28 monitoring trips were undertaken over a three year period from February 2005 to March 2008 to collect fluids and gas from eight producing wells. Chemical and isotope analyses were conducted on the fluid and gas samples to determine the changes in the geochemistry of the pilot area and to assess the fate of the injected CO2. It was found that within 67 days after commencement of CO2 injection, injection CO2 break-through occurred in four of the eight monitoring wells. Further, CO2 dissolution was observed in three of the four monitoring wells in this time frame and in one well, 12–12, both CO2 dissolution and calcite mineral dissolution were observed within 67 days of the onset of CO2 injection. Within 18 months siderite dissolution and calcite dissolution were observed in all four of these wells. In the remaining four wells, CO2 dissolution was observed, indicated by a slow decreased in pH from 7.5 to 7.2 with no significant change in total alkalinity or calcium concentration in the water. Inter-well communications were observed between wells 08–11 and 12–12 by means of residual “kill fluid” migration occurring from well 12–12 to well 08–11.