Optimising CO2 storage in geological formations; a case study ofshore Scotland - CO2 MultiStore project

Abstract

Carbon capture, transport and storage (CCS) is considered a key technology to provide a secure, low-carbon energy supply and reduce the greenhouse gas emissions (DECC, 2014) that contribute to the adverse effects of climatic change (IPCC, 2014). Commercialisation projects for the permanent storage of carbon dioxide (CO2) captured at power plants are currently in the design stage for the Peterhead, White Rose, Caledonia Clean Energy (DECC, 2013, 2015) and Don Valley projects. Storage of the CO2 captured by these projects is planned in strata deep beneath the North Sea in depleted hydrocarbon fields or regionally extensive sandstones containing brine (saline aquifer sandstones). The vast majority of the UK and Scotland's potential storage resource, which is of European significance (SCCS, 2009), is within brine-saturated sandstone formations. The sandstone formations are each hundreds to thousands of square kilometres in extent and underlie all sectors of the North Sea. The immense potential to store CO2 in these rocks can only be fully achieved by the operation of more than one injection site within each formation. Government, university and research institutes, industry, and stakeholder organisations have anticipated the need to inform a second phase of CCS developments following on from a commercialisation project in Scotland. The CO2MultiStore study, led by Scottish Carbon Capture and Storage (SCCS), investigates the operation of more than one injection site within a storage formation using a North Sea case study. The Captain Sandstone, within the mature oil and gas province offshore Scotland, contains the Goldeneye Field, which is the planned storage site for the Peterhead CCS project. Previous research (SCCS, 2011) was augmented by data from offshore hydrocarbon exploration and detailed investigation of the Goldeneye Field for CO2 storage (Shell, 2011a-i). The research was targeted to increase understanding and confidence in the operation of two or more sites within the Captain Sandstone. Methods were implemented to reduce the effort and resources needed to characterise the sandstone, and increase understanding of its stability and performance during operation of more than one injection site. Generic learning was captured throughout the CO2MultiStore project relevant to the characterisation of the extensive storage sandstones, management of the planned injection operations and monitoring of CO2 injection at two (or more) sites within any sandstone formation. The storage of CO2 can be optimised by the operation of more than one injection site in a geological formation by taking a regional-scale approach to site assessment. The study concludes that at least 360 million tonnes of CO2 captured over the coming 35 years could be permanently stored using two injection sites in the Captain Sandstone. Confidence in the planned operation of two or more injection sites in a storage formation is greatly increased by the use of existing information, knowledge and data acquired during hydrocarbon exploitation. Widespread pressure changes should be expected by the injection of CO2 at more than one site. Assessment, management and monitoring of pressure changes on a regional scale will optimise the storage capacity, ensure security of storage and prevent adverse effects to existing storage and hydrocarbon operations. The vast offshore potential across all sectors of the North Sea could be made accessible and practical for storage of CO2 captured from European sources by the operation of two or more sites in a storage formation by following the approach taken in CO2MultiStore.