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Spear-fishing in central Newcastle

We were overwhelmed with the national (and then international) press response to our project when we decided to open the site to journalists on Monday 27th June. We knew there was plenty of interest, of course, after the terrific response to the first press day we held back in February, when the first rig was on site.

But partly because we’d had more coverage than we ever dreamt of back then, we really thought there would be limited interest this time – how wrong we were! It was brilliant dealing with the press. I now really admire the spines of steel the journalists have, to do live broadcasts to news programmes every day: one day was nerve-wracking enough for me!

Just for the record, we have known for ages that the climate in what’s now Newcastle was tropical back in the Carboniferous Period, 300 million years ago – we were just showing our visitors from the press some particularly nice fossil corals we’d found and explaining how this means it used to be like the sea around the Bahamas round here, way back then.

I think they thought this was the first time this had been realised, so a story of ‘Newcastle used to be like the Bahamas’ spread rapidly in the press – even, so I’m told, winning the prize for weirdest news item of the day (or something like that) on Chris Evans’ Radio 2 show on Tuesday 28th.

The real occasion of this week’s press event was nowt to do with fossils, but with present-day reality: we had finally got an unequivocal heat signal in the water that’s pumped from the borehole to wash the drill cuttings to surface. At that point the bottom of the borehole was just about at 1500m (1485m to be precise), and we estimate the bottom-hole temperature there to be about 55 degrees Celsius.

The overall mix of water from the full depth of the borehole was 42 degrees – impressively warm to the touch, and impressively ‘steaming’ off the shakers (the devices that separate drill cuttings from mud) at the back of the rig. What this means is that we are confident the temperature at our final target depth (2000m) will be in the 70s – certainly high enough to be usable for space heating and cooling of at least one decent-sized building.

Whether it will be able to supply more than that depends on how permeable the sandstones in the lower parts of the borehole will be – that’s the next frontier for us.

After all the fuss and euphoria on Monday, the site was returning to normal on Tuesday, with a routine insertion of a new drill bit into the borehole. Then calamity struck – the rods couldn’t proceed beyond about 1100m, and we later discovered that this was because, inexplicably, the new bit had detached itself from the bottom of the down-hole hydraulic motor we use to maximise the rotation of the special diamond-impregnated bits (PDCs), which we use for deep sedimentary strata.

There then began a lengthy episode of what we in the drilling business call ‘fishing’ – trying to retrieve the loose item from the borehole. As you might imagine, retrieving a six-inch diameter object from a six-inch diameter borehole more than a kilometre below ground is not easy. Despite the difficulties, Jim Dawson and his team did manage to pick the bit up on the end of the drill rods – only for it to detach itself again before it could be safely landed at surface.

This time it fell all the way to the bottom. Special tools had to be tried next, included a giant thread-cutting tool known as a ‘spear’, which can bore into a metal object and grip it. So there we were: spear-fishing in central Newcastle. Spear-fishing is, of course, something you can also indulge in today in the sea around the Bahamas, and I think all of us would have preferred that variety!

Sadly, the spear didn’t catch our fish, so we had another go with the mother of all magnets. It was just at 7:45 this morning (Saturday 2nd July) that we discovered that the magnet had not done the business either. The bit must be stuck like an egg in a pan. So we are now preparing the borehole for the ultimate solution: side-tracking. In this operation, we plug the bottom 100m or so of the borehole with cement, then, after that has set, re-enter with our drilling tools, set up to deviate slightly away from the present line of the borehole.

We will drill through the wall of the original borehole, by-pass the section where the bit will hereafter be forever entombed, then continue on down towards our target depth. As it happens, the borehole had already deviated a few degrees from the vertical, just because of the refraction that happens when the drill bit passes from soft layers into hard layers.

So when we’re done by-passing, we’ll probably be closer to the vertical again anyway. Wish us luck as we manoeuvre our way onward and downward!

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