The rods are turning again at last!
It's been two months since I last had anything interesting to report, but they've not been idle months for us.
We had always anticipated a gap of a few weeks between completion of the first phase of the borehole and the start of the main phase. When Drilcorp completed the first section of the borehole to 245.5m ahead of schedule, that made it look like we'd have four or five weeks to wait, while we finalised contractual arrangements with the specialist sub-contractors for the deeper reaches of the borehole. That job turned out to be a lot more challenging than we'd bargained for.
At the best of times, there are relatively few large onshore drilling rigs in the UK. However, with the price of oil having been so high lately, those few rigs have been in heavy demand. That not only means that rigs are hard to book - the prices are also high, as companies sell their services to the highest bidders. For the likes of us, with only one borehole to drill and a strictly finite budget, it's difficult to interest a company that might have an offer of a series of deep boreholes for a major oil and gas company. At one stage, we thought the only rig we'd be able to get would have to be hired from the south of France - although the costs of mobilising everything from there would have been really high. Various twists and turns in the negotiations then ensued, and there were times I wondered if we'd still be trying to get a rig on site come Christmas!
Thankfully, we finally managed to book an ideal rig - the one I'd most fancied all along, having seen it in action up in Scotland about three years ago, when it was drilling for coalbed methane near Stirling. The rig is operated by Geometric Drilling Ltd, and to a hydrogeologist like me it is a sight to behold. With a mast standing 18m high, and a hydraulic hoisting capacity of more than 100 tonnes - enough to lift, say, fifty normal-size cars at once!
Of course the rig is only part of the package - even more important is the skilled and dedicated crew who operate it. Here we are truly fortunate - the team from Geometric Drilling are excellent, and have entered fully into the spirit of our venture. We have also been really fortunate in attracting further support from the British Geological Survey. Not only have they added £150,000 to our drilling budget - which certainly increases our chances of affording to continue drilling all the way to our ideal target depth of 2,000m - they also bring a huge wealth of scientific expertise and enthusiasm to bolster our existing team from Newcastle and Durham Universities.
Geometric Drilling began setting the rig up on Tuesday 31st May, and at 16:30 on Saturday 4th June the set-up was complete and work began on pressure-testing the existing borehole, to make sure that all the safety equipment would function as planned in the unlikely event we hit any problems, such as unanticipated pockets of natural gas or oil at pressure. Between the drilling platform and the top of the borehole is a large red steel structure - an array of powerful valves and chambers - known as the BOP (blow-out preventer). This is rated to withstand far more than the most outlandish worst-case scenario for unexpected gas surges.
After all of the tests had been successfully completed, the rods were turning again, first installing a shallow borehole (known as the "mousehole") next to the main borehole, which is simply designed to make it easier to prepare lengths of casing (steel tubing) for installation in the main borehole. Then drilling began again in the main borehole.
The first task was to drill through a metre of cement that had been left in the toe of the casing at 244m below ground. It was right around noon on Sunday 5th that the drill bit cleared the last of the cement and entered virgin rock strata again: gray, fine-grained sandstone, which bodes well for rapid drilling in the next week or so.
Below is some footage from our downhole CCTV which we recorded at the end of March, before the steel casing was installed, which show some of the amazing rock fractures 160m or so below the City.