In mid-February 2011, Drilcorp mobilized to the Science City site which was the old Newcastle Brewery Site adjacent to Newcastle’s St. James Stadium.
The objective is to drill a borehole to a depth of 2000 metres beneath the site to explore for hot water which, if found, will be used to supply the future energy needs of the site and possibly the surrounding area.
The drilling of the borehole will present several technical challenges and for that reason the construction has been split into 2 phases.
Phase 1: Drilling and Lining of the Coal Measures.
The top 300mtr of the borehole consists of the Lower Coal Measures strata. This sequence of rocks contains many coal seams, several of which were historically mined. When drilling in mined areas, extreme care must be taken. Flushing medium may be lost into the workings and this can cause the collapse of the borehole or the drilling bit to become stuck in the borehole. If flush is lost then steps must be taken to recover it.
Cement grout must be pumped into the voided section to seal up fractures. This may need to be repeated until all voids are filled and circulation can be regained in order to advance the borehole deeper. Other hazards relating to drilling through mine workings include the possible presence of man-made materials such as roof girders and railway lines. Timber chocks, extensively used in the mining industry, are also very difficult to drill through.
Once all seams are effectively penetrated the borehole will be lined with a heavy duty steel casing. The annulus between the casing and the borehole wall will be fully grouted and pressure tested. Phase one of the works may continue to approximately 500 metres before a more powerful drilling rig is used to complete the works. A 20 ton drilling rig will drill phase one using a closed-circuit polymer mud flush system.
Phase 2: Deep Drilling
This phase of the works will be carried out by a 100 ton drilling rig, the specification being decided by the amount of drilling equipment the machine can pull out of the ground. This rig will also use a mud flush and will drill at about 8.5” diameter.The challenge of this section of the borehole will be depth and the possibility of finding hydrocarbons such as natural gas or oil. Drilling at these depths requires specialist knowledge and a highly-specialised deep drilling engineer will be employed to oversee this phase of drilling. The borehole will need well control and will therefore be fitted with a blowout preventer.
