The Dynamic Aspect of Formation Storage Use for CO₂ Sequestration

The Athabasca Oil Sands Project Joint Venture (AOSP JV) owners – Shell Canada Energy (Shell), Chevron Canada Limited (Chevron) and Marathon Oil Sands L.P. (Marathon) – are advancing front-end development plans of a fully integrated carbon capture, pipeline and storage project in Alberta called the Quest CCS Project. A Final Investment Decision for Quest is scheduled for 2012. Quest is designed as a fully integrated CCS project in the oil sands sector involving CO₂ capture at the Scotford upgrader near Fort Saskatchewan, pipeline transportation northeast from Scotford and CO₂ storage in a deep saline formation zone, the Basal Cambrian Sand. Over the expected lifetime of 25 years, the project will capture and store up to 1.1 Mt of CO₂ per year from the steam methane reformer units at the existing Scotford upgrader and at the upgrader’s expansion currently under construction

Conventional volumetric methods for the pore space assessment of CO₂ storage, such as the guidance provided by the 2008 Carbon Sequestration ATLAS of the United States and Canada, are good tools in estimating the pore space available, while also considering empirical DOE ranges for storage efficiency, such as area and vertical sweep efficiency, gravity contact efficiency and microscopic displacement efficiency. Such assessment would suggest a CO₂ storage capacity of the Basal Cambrian Sand at Quest of approximately 7 Mt per township (6 miles x 6 miles). However, such an estimate is of a static nature, not taking into account dynamic system constraints such as required injection rates, bottom-hole pressure constraints and associated well count and well spacing, including pressure interference and regional pore pressure increase.

Dynamic reservoir simulation has been performed, for a variety of subsurface realizations, covering the full range of current subsurface uncertainties, with the aim to optimize the development while also estimating the required pore space for CO₂ storage. Following the concept of linking the required pore space to pore pressure increase, rather than CO₂ plume extension, resulted in a significant reduction of pore space utilization in the Basal Cambrian Sand from the initial 7 Mt per township to only 0.67 Mt per township and will have a potential impact on additional CCS developments in the region.