How to Discover a Storage Resource: Following the Principles of the SPE-SRMS What is Required to Classify as Storage Resource as ‘Discovered’?

Abstract

How can we know that a developable storage resource exists at a given location – i.e. it is discovered? Is the presence of a permeable rock sufficient? How does a developer, financier or policy maker gain sufficient confidence that CO2 can be stored at an injection site to proceed with a project? The SPE have released the SRMS (Storage Resource Management System) which can clarify communication of storage resource confidence, using a consistent set of principles for classification (of resource maturity and ‘certainty’) and associated storage resource estimation methodology. There are strong similarities between the exploration and development of hydrocarbon resources and storage resources, and hence between the PRMS and SRMS. A notable difference is the additional requirement to demonstrate an expectation of long-term containment of the injected CO2 for a storage resource. A resource could not be classified as a discovered contingent resource until the expectation of a competent seal (to contain the injected CO2) is demonstrated (with direct supporting evidence) over the entire reservoir area where the injected CO2 plume might migrate in the long-term. The predicted pressure footprint may be permitted to extend beyond the discovered seal area. Many estimates in the literature take the pore volume of a formation and multiply this by a storage efficiency, but they do not critically assess the storage efficiency factor with containment in mind, in particular the containment of a migrating CO2 plume. The OGCI has reviewed publicly available CO2 storage resource assessments for the Captain Sandstone formation (UK Central North Sea), against the SRMS framework of principles. The potential classification of the storage resource estimates reviewed (both regional and site-specific) are discussed based on the available information. This focuses on allocating the resource estimates to either the discovered contingent resource class, or the undiscovered prospective resource class, through application of the SRMS principles for resource discovery. This review has triggered key questions, such as: How large an area can a single well ‘discover’? and, what is required to discover an open store (where injected CO2 is free to migrate laterally) versus CO2 storage resources utilizing a ‘trap’ which prevents lateral migration? Which are also discussed.