OR/19/052 Appendix 3d - Array 4 Borehole descriptions
|Kingdon, A, Fellgett, M W, and Spence, M J. 2019. UKGEOS Cheshire Energy Research Field Site - Science infrastructure. British Geological Survey Internal Report, OR/19/052.|
Contributors: Midgley, J, Elsome, J W, Dearden, R A, Chapman, C, Burke, S P, Hough, E, Luckett, R R, and Bianchi, M.
|Array 4: Multi-scale array||Description|
|Scientific Objective:||Multi-scale experimental site for quantification of groundwater properties and geological characterisation of the Permo-Trias succession. This will include: identifying the location of the intersection of the Dungeon Bank Fault and the Role of faults as a barriers/pathways to fluid/gas migration|
|No of Sites||1|
|Expected Lithostratigraphy at TD||Quaternary/Triassic Sherwood Sandstone Group (SSG) for 50 m boreholes, SSG for 100 m boreholes, Upper Carboniferous (Warwickshire Group or Pennine Upper Coal Measures Group) for 600 m boreholes|
|Boreholes per site||8 x 50 m, 12 x 100 m, 3 x 600 m|
|Casing Installed||Steel casing installed in top section of 600 m boreholes|
|Expected end use||Multi-scale experimental site|
|Samples available during drilling||Drill cuttings collected sporadically|
|Cored Boreholes||1 x 600 m 3 x 100 m|
|Geophysical logs: Run 1||1 x 600 m well: near-oilfield log suite (Density-neutron-spectral-gamma, P&S wave sonic, resistivity, SP), 2 x 600 m well : gamma ray-caliper (borehole diameter)|
|Borehole Imaging: Run 1||Medium-high resolution resistivity logging in core 600 m well or acoustic imaging in 1 x 600 m boreholes|
|Geophysical logs: Run 2||1 x 600 m well: near-oilfield log suite (Density-neutron-spectral-gamma, P&S wave sonic, resistivity, SP), 2 x 600 m well : gamma ray-caliper (borehole diameter) + casing inspection tools ( Cement bond long + ultrasonic imager)|
|Borehole Imaging: Run 2||Medium-high resolution resistivity logging in core 600 m well or acoustic imaging in 1 x 600 m boreholes|
|Drilling parameters||Potentially recording of drilling parameters|
|Geomicrobiology sampling||Standard geomicrobiology sampling protocol: 1 sample per 10 m of core in cored boreholes|
|Gas testing during drilling||None Planned|
|Fluid testing during drilling||None Planned|
|Fluid Testing Post Drilling||Baseline conditions & after pressure injection experiments|
|Pump Testing||Multiple cycles planned for experimental array, details to be confirmed|
|Permanently installed equipment||Cross-borehole and surface-borehole 2D and 3D geoelectrical imaging (electric resistivity tomography) array; Time-lapse imaging of fluid processes in the near surface including natural and induced changes|
Components of array 4
The multi-scale array will enable hydrogeological and hydrogeophysical characterisation of the rock mass from surface to experimental borehole depth. It will allow subsequent investigation of hydraulic, geophysical and geochemical processes at multiple scales (space and time), particularly in response to changes induced by controlled experiments.
Whilst drilling will be completed in Array 4 during the delivery phase of CERFS, this array is intended to continue to operate for an extended period allowing multiple future opportunities for the hydrogeology to be characterised by repeated hydrogeochemical and geophysical sampling.
Data acquisition in array 4
Data, primarily wireline and core data, will be collected through the drilling and construction process. Electrical Resistivity Tomography (ERT) sensor cables as well as DAS/DTS fibre optic cables will be installed down the back of the casing. The metal casing will require electrical isolation from the lithology. The purpose of the fibre optic cables will be to obtain high resolution temperature data to help calibrate ERT electrical imaging data.
The well will be completed to allow future installation of various downhole probes, including but not limited to seismic, pressure and temperature sensors. Screened casing sections may be incorporated to provide hydraulic access to permeable geological units for future hydrogeological and hydrogeophysical experimentation.
|Location||50 m||100 m||Up to 600 m||Cored|
Repeated water sampling and pump testing is intended for Array 4 into the future but precise protocols are yet to be defined so sampling opportunities of these materials cannot be provided at this time.