OR/17/048 Further work

Fellgett, M W, Kingdon, A, Williams, J D O, and Gent, C M A. 2017. State of stress across UK regions. British Geological Survey Internal Report, OR/17/048.

Compiled information on the UK stress field shows differences of up to two MPakm^-1 in S_v and S_hmin between areas of Cheshire, Lancashire and East Yorkshire North Nottinghamshire. Data from Cheshire and Lancashire region have provided estimates of S_v pore pressure and Shmin near the Proposed UKGEO southern site. Pore pressure is likely to be between 10.19 and 10.8 MPakm^-1, S_v between 23–25 MPaKm^-1 and S_hmin has been estimated using leak-off test data to have a value of 17.4 MPakm^-1.

The conclusions of this report are based on the integration of published legacy data and information from the BGS archives. Locally it has allowed characterisation of the stress field and in particular S_v, S_hmin and P_p. There are no locations within the regions studied which contain sufficient data to study trends or variations in: S_v, S_hmin or S_HMax with depth, with the exception of studies at Preese Hall and Sellafield (Baker Hughes, 2011: Nirex, 1997).

The UKGEO project provides a unique opportunity to study the relationships between S_v, P_p, S_hmin and S_HMax at a variety of depths at a single locality in the UK subsurface. It could also provide an example of how these stresses affect borehole stability over an extended period of time.

Collecting drill core, XLOT’s, wireline RFT, borehole imaging and density logs from surface would allow detailed investigation of the stress field at the site. This would then form the basis for a geomechanical model, which aid the design and implementation of innovative subsurface energy technologies.