Exploration Drilling Techniques

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1 Exploration Techniques Why do we need natural resources? average increase in demand: 5 % per year How do we find new resources? How do we find new resources? Fun! Geological methods: In my view the greatest value is added by the geologist who starts with nothing other than some ideas and goes out into the desert and finds an orebody. Systematic exploration of larger areas Exploration in geological environment found to be similar to known deposits Improved geological interpretation and analysis of existing data J.K. Ellis, Chairman of BHP, Australia 1998 Reality is: hard work! Development of exploration model based on geological, geochemical and geophysical parameters How do we find new resources? Pre-study How do we find new resources? Reconnaissance exploration What is beneath our feet? Detailed follow-up exploration Evaluation 1

2 Example: Example: Geothermal Energy Project St. Gallen Geothermal Energy Project St. Gallen Pre-study: Pre-study: Seismic Field Campaign Interpretation of seismic measurements Example: Geothermal Energy Project St. Gallen Oil field rig Exploration: Start of drilling: Monday March 4, Mud tank 4. Mud pump 7. Winch 14. Derrick/mast 16. Drill rods 20. Rotary table Deep water wells (Palestine) 23./24. BOP 26. Drill bit 2

3 Rotary table with opening for the kelly Drill bit (Trycone) Drive mechanism Some details Modern drill rig for deep drilling Schematic sketch of modern drill rig for deep drilling Top drive instead of rotary table 3

4 250m³/h 250m³/h 300m³/h chute with 1,5% incline 300m³/h M M M Pipe handler Mud flow 2mm M M M 0,10mm 100m³/h 0,10mm 100m³/h 0,10mm 100m³/h M 0,02mm 15m³/h M M M 15m³/h 0,02mm Spindle drive Spindle drive Mud flow in borehole no need to be very big! Pumped down the drill string Raises in the annulus Cooling of the drill bit Carries the cuttings to the surface Prevents from blocking the string (thixotropy) 4

5 Directional drilling ms.php?pagename=61 &moviequality=hq&sid= 4403c274e1c7f695bfe f36 The drill string becomes flexible when drilling very deep boreholes direction cannot be maintained A downhole motor (positive displacement motor PDM) is used for driving the drill bit The mud flow drives the PDM MWD (measurement while drilling) allows continuous directional control of the drill bit Allows drilling of several wells from 1 drill site (most often applied in off-shore drilling) Reverse Circulation (RC) Reverse Circulation (RC) A pneumatic reciprocating piston (hammer) drives the a tungsten-steel drill bit Working with large air compressors, the drilling produces dry rock cuttings Dual wall drill rods are used to inject air and to produce cuttings through the drill string Air is blown down the rods (annular space) and air, water and cuttings are lifted inside the inner tube Air passes through a cyclone for separation of cuttings Reverse Circulation (RC) Reverse Circulation (RC) Iron ore exploration (Western Australia) Down-the-hole-hammer drilling (also Rotary Air Blast drilling RAB) Pneumatically reciprocating pistondriven hammer Cuttings raise in the annulus Efficient drilling technique Used in exploration, blast-hole drilling, water wells, geotechnics 5

6 Down-the-hole-hammer drilling (also Rotary Air Blast drilling RAB) Commonly used drilling technique for ground heat pumps Depth is limited by maximum pressure of compressor Auger drilling in unconsolidated ground, in soil or in weathered rock e.g. for bauxite exploration Diamond core drilling Diamond core drilling Wireline core drilling (gold exploration, Quebec, Canada) Drill core growths inside inner tube Retrieve the entire drill string to recover inner tube with the core Core lifter case at bottom end of inner tube prevents the core from falling out Diamond core drilling Diamond core drilling Wireline core drilling (iron ore exploration, Cameroon) Drill bits for diamond coring 6

7 Wireline coring Wireline coring Drill core grows inside inner tube Inner tube with latch head A overshot tool is lowered on the wireline to unlatch the inner tube from the core barrel Overshot tool Retrieve the inner tube with the core Wireline coring Diamond core drilling Inner tube Overshot tool Drill cores in core boxes Accident in Mina San José August 5, 2010 Raise bore technique 1. of a pilot hole 7

8 Raise bore technique Raise bore machine 2. of a shaft Raise bore head Down-bore technique Shaft sinking from top Rescue of Chilean miners Rescue of Chilean miners after 69 days October 13,