GOLD MINING UNDERGROUND

Successfully logging multiple inclined bore holes in difficult space and application positioning

Using a high resolution acoustic televiewer(HRAT) to log data to assist management with mineralisation modelling, development planning and extraction projections; the application was used to identify and characterise stacked veins, fault breccia, mineralisation zones, foliation characteristics, secondary micro-faults, fractures and fault patterns. it required 9 boreholes to be logged during site visits staged over 3 months. The boreholes were 400 through 500m deep and typically inclined at 35 to 45 degrees, core drilled with an OD of 76mm.

Underground logging at angles in small outside diameter boreholes required a chamfered cable head to be developed with a method of retrieving probes through an inclined hole of 75mm OD into 45mm iD of drill pipe, a tight tolerance between pipe and the 42mm probe.

The logging rig had to be modified for each location within the mine and adapted to suit the positioning and available space. By installing into the mine roof drill rig pulley wheels or suspended lightweight sheave wheels, access was gained for all the required boreholes. The boreholes were logged in stages to minimise the increased risk of collapse of the inclined holes. to gain maximum data coverage the drill pipe was left in the hole to a point just beyond known areas of suspect ground with logging achieved at this depth, then more pipe removed with the overlap logged in the newly exposed open hole.

The Acoustic televiewer was deployed with 100% reliability and the mapping of faults and fractures was successfully completed. WellCAD? software was used for data handling, processing and presentation of data as image log and tabulated format.

Surface equipment was a 2,000m winch with a 4 core cable connected to a Micrologger system. the winch was modified for underground working and in line with HSE guidelines include a fully lockable guard on the drum, cable and moving parts, conversion of the operating voltage to 110v and skid mounting for ease of use underground.