This twelfth entry was published originally by JSHarris on the 19th August 2013 and received 1,249 views on the closed forum
I just knew I shouldn’t have made that quip about fracking last week. It was stupid. In fact so stupid that it’s deeply offended the gods who look after our environment (who clearly don’t have a sense of humour). They’ve decided to teach me a lesson………….
Just after posting the last entry I had a call from the drillers. A neighbour had reported air bubbles blowing up through the bed of the millstream, some distance from the borehole. The drillers were using compressed air to blow the cuttings out and it seems that down at around 15m or so they hit a fault in the gault clay, a fault that’s hydraulically connected to the stream, most probably through a subterranean spring that normally flows water into the stream bed. It seems this compressed air overcame the water pressure at this depth and forced its way up through the stream bed, some 30 to 50m from the borehole position.
The drillers thought they could fix the problem by sticking more casing down the hole (only costs me £35/m……). We thought this had worked, but today when the drill rig started up the stream turned black with liquefied gault clay being blown through the fault. This has caused us to abandon this borehole at a depth of 21m and take the best part of £3k in lost cost.
The plan now is to bring a bigger rig on to site tomorrow or Wednesday and drill a new borehole in a different location, one that will (hopefully) not be hydraulically connected to the stream. We’re moving further away from the stream, to a location where we’re hopeful that there won’t be any springs underground. The bigger rig will be able to sink a longer length of casing in the bore, though, so even if we do hit problems the hope is that the casing will seal off any leaks.
The other hit we’re taking is by having to abandon the water pipe duct we’ve put in under the foundation. The new borehole location is the other side of the site, so we’ll need to dig a new trench and stick another length of ducting in.
Still, the good news is that the new brickie and renderer I’ve found are a fair bit cheaper than the original quote, so I’ve saved a bit on this that’ll help cover the extra borehole cost.
It’s a bit like Russian roulette this drilling game………………..
Shah 21 Aug 2013 04:39 PM :
Sorry to hear that JSH. That is building work. **** happens the moment you mention the project is running smoothly.
jsharris 21 Aug 2013 06:04 PM :
Thanks, I’m now expecting the worst, and planning for what might happen if the second borehole fails as well……………..
The bigger drill rig is now on site, set up and drilling, so the critical time will be around mid-morning tomorrow when it hits the depth where the other rig had problems. The first borehole was over by the right-most pole in the photo of the model at the top of this blog, the stream runs along by the tall hedge at the bottom. The new borehole is up by the retaining wall, towards the back of the garage base, so a lot further away from the millstream.
ProDave 22 Aug 2013 07:36 PM :
So did you make progress today? or did you have further trouble?
jsharris 22 Aug 2013 08:30 PM :
The drilling’s going slower than hoped, but so far there’s no blow through to the stream. The drillers are chucking extra casing down as a preventative measure, but this slows drilling down, as they have stop every couple of metres, pull the whole drill string out, swap the drill string for a length of casing, which means unscrewing each length of drill pipe to separate them into short lengths, then threading another length of casing on to that already down the hole, then pushing the casing down to drilled depth, then dropping the drill string down again, threading all the lengths of drill pipe on one by one.
The rig will drill at a rate of a metre every ten minutes or so, but it takes at least 4 or 5 times as long to keep pulling the string, sticking more casing down and then dropping the string back down the hole (if you’ve watched “Black Gold” on TV then you’ll have a feel for the process – this is pretty much the same, except we have to stop and add casing every couple of metres).
jsharris 23 Aug 2013 06:20 PM :
An update. Our luck (and that of the drilling company) seems to be following it usual course of things going wrong. The drill rig broke earlier, and needs a replacement valve from Italy, which has a ten week lead time. These things happen, though, and it’s no one’s fault, just bad luck. They’ve taken the defective parts off site and are going to see what they can do to fix things next week, but there won’t be any further drilling for at least a week, maybe longer, whilst they sort out an alternative way of drilling our hole.
It looks as if I will have to delay the house delivery until I can be reasonably sure that the rig is going to be off site, not really a problem, as we’re not in any great rush to finish the house, just a bit of an exercise in replanning the programme and sorting out things like a temporary water supply for the guys who will still be working on site. I rang around to see what the cost of a hired water bowser would be – they are silly money for what they are, like around £130 a week. As I can buy 25 litre containers for around a fiver, that’s what I’m doing. It’s no hardship to just lug five or six of these over to the site in the back of the car every time I go over and I reckon the guys I have doing some stone work and rendering should be able to get by on 100 to 150 litres of water a day.
Looks like I need to keep the fingers of both hands crossed from now on.