Subsurface Characterisation of a Saline Aquifer Cited for Commercial Scale CO2 Disposal

Abstract

The Yorkshire & Humber area contains some of the biggest CO2 emitters in the UK. The UK Southern North Sea (SNS) contains a number of gas fields and saline aquifers which could provide storage for some of that CO2. National Grid Carbon (NGC) has plans to connect these sources and sinks via a shared 24” pipeline in a hub & spoke arrangement called “The Humber Cluster Project”. After several years of high level study using multi-client seismic surveys and a database of released well data, an anticlinal structure of around 25 km length and 8 km width with a 275 m thick Bunter sandstone formation (saline aquifer) was selected for detailed analysis. Two crestal wells in the structure called 5/42 were drilled in 1970 and 1990 looking for hydrocarbons but only brine was found. Basic formation evaluation logs were acquired in both wells. Limited core and pressure data were acquired in the 1990 well. No record of any water analysis is available and the core and log coverage was limited. As of mid-2012 some uncertainties remained with respect to the suitability of 5/42 for CO2 disposal. Little was known about the strength & permeability of the cap rock which consists of 10-12 m of shale overlain by about 80 m of halites and mudstones. Although the structure seems well defined and no major faulting was seen in the Bunter sandstone there was little reservoir permeability data, especially vertical permeability. In addition no flow test, production or injection, had been undertaken in 5/42. To address these issues, the company applied for and was awarded the UK's first Carbon Storage licence from the UK Government in November 2012 which permitted the drilling of appraisal well 42/25d-3 in the summer of 2013 with generous financial support from the European Commission (through their EEPR scheme) and the UK Energy Technologies Institute (ETI).