Marriott recently completed a three-year comprehensive exploration programme for York Potash, a subsidiary of Sirius Minerals, in North Yorkshire. This world-class exploration programme utilising heavy duty mining wireline systems to core the evaporate deposits included seven geological exploration boreholes to depths up to about 1700 m. Two boreholes were also drilled down the centres of the two proposed deep mine shafts to investigate the ground conditions for shaft construction.
Notable is that eight side-tracks, typically from 1250 m, in the exploration holes were carried out successfully with inclinations up to 42o allowing additional coring to measured depths up to 1690 m to determine the geometry of the various evaporate layers to assist in the mine planning. In three boreholes, two sidetracks from the ‘mother’ borehole were achieved.
Three rigs were initially employed on this programme reducing to one for the final phase of the project.
This successful application of the use of heavy duty mining wireline systems illustrates the value of this approach for geological characterisation for such projects as well as investigations for radioactive waste disposal facilities, coal bed methane, mineral mine development and geoscience with coring strings available for exploration to depths up to 5000 m.
Marriott has also been involved recently in milling casing in the shaft centre boreholes in North Yorkshire to allow the shaft construction to proceed.
