Depositional environment and aquifer properties of the Sherwood Sandstone Group in the Cleveland Basin based on investigations at Woodsmith Mine

A major mining project by Anglo American plc at Woodsmith Mine is targeting deep polyhalite deposits in the Cleveland Basin of North Yorkshire. The mine shaft design included hydrogeological assessment of the full 1600 m hydrostratigraphic sequence to be intersected. Of this sequence the most significant aquifer that will be intersected is the Sherwood Sandstone Group (SSG), which will be encountered at depths of between 800 and 1050 m below surface. Deep exploratory cored boreholes were completed at the site to allow both laboratory and field testing. The methods used to determine the aquifer characteristics comprised geotechnical laboratory testing of rock core and oilfield downhole wireline technology. Geotechnical triaxial tests were used to determine the horizontal and vertical permeability of rock core recovered from deep exploration boreholes. Wireline Elementary Log ANalyses (ELAN) and Modulation Dynamic Testing (MDT) were used to determine hydraulic conductivity and porosity of the SSG sequence encountered. Formation Micro Imager (FMI) was used to determine sedimentary depositional features. This paper presents a review of the ground investigation data collected to characterize anisotropy between horizontal and vertical flow within the SSG in this part of the Cleveland Basin. Thematic collection: This article is part of the Hydrogeology of Sandstone collection available at: https://www.lyellcollection.org/cc/hydrogeology-of-sandstone