Since September 14th several thousands of shots along three lines from the surface have been done and registered by geophones inside the borehole and along the lines. The measurements are definitely on schedule.
The ICDP OSG logging team performed a downhole measurement campaign in the borehole COSC-1 on September 9 to 12, 2014. Afterwards the OSG logging team and members of the GFZ Scientific Drilling platform prepared the geophone chain for a longer VSP experiment in COSC-1. These measurements will last until October 9, completed by a final downhole logging campaign beginning on October 10, 2014.
The last drill core is up. Everything happened very quickly during the last days. There wasn’t the expected 16+ hours break to change the drill bit - it lasted for 290 m until all “good” drill pipes were in the drill hole and the drill rig was at the edge of its capacity under the present technical circumstances. End of drilling. It takes some time to comprehend. Some numbers: COSC-1 TD is 2495.8 m (driller’s depth). According to the scientific documentation, we drilled 2393.1 m and recovered 2396.5 m of core + c. 2.5 m of documented core loss, both starting at 103 m (lower end of the conductor casing). The most likely explanation for the difference in TD/drilled length and depth according to documented core recovery (2502 m) is stretching of the drill pipes under their own weight in the drill hole, i.e. we have a core recovery of 100.14 %, despite of 2.5 m documented core loss. So where are we? Somewhere around 2500 m below the drill site and probably somewhere between 150 and 200 m besides it (a rough estimation based on the logged deviation at 1616 m and the angle measured by the Devicore BBT in the lower part of the well until we get precise data from logging). Geology: still present at the bottom of the drill hole. Mylonites, mylonites, mylonites. With garnets. But now mostly in meta-arkoses. Further studies will check this up and, hopefully, tell us more about the position in the tectonostratigraphy. Good to know that drill hole didn’t make a U-turn towards Åreskutan and the thrust zone below the Upper Sever Nappe! It’s far too early for conclusions, but some thoughts at the end of the drilling operations, after several months on-site: Completing the COSC-1 drill hole at about 2.5 km is a huge achievement, in particular with regard to the technical circumstances. A huge THANK YOU to drilling and technical teams! The rock quality in the area contributed to the amazing core recovery (never seen before by the drillers, not even in a shallow drill hole), although it seemed to eat drill bits in the Seve Nappe rocks. The on-site science was a huge effort - about 5 man-years (rough calculation). We never could have done this without the help of all the volunteers. A huge THANK YOU to the on-site science team, and in particular to all volunteers! About geology: We got an exceptional section through a high-grade metamorphic nappe and into the underlying thrust zone of a major mountain belt. The thrust zone has an unexpected thickness and, thus, hasn’t been penetrated completely. This is a pity, but the recovered material is unique and has a huge potential for subsequent detailed research by the COSC science team. A drill hole in such good rock seems to be ideal for the up-coming downhole studies of the geophysics and geothermal working groups (although we know that anything can happen to a drill hole). Continue to follow this page at least in the coming month to learn more about their research. Those researchers whose research is based (at least partly) on water conducting fractures and porosity, i.e. the hydrogeologists and microbiologists, were less lucky. We have seen very little of it. But who knows, maybe there are other interesting aspects in or despite it. And finally a unscientific conclusion, based on statistically not confirmed material: As soon as a microbiologists enters the drill site, the drill rig will most likely break down, or there will be another reason why drilling has to be stopped. No offence meant - we really enjoyed their company during the waiting time! And we sampled for them until the very last core run (core with water-conducting, calcite filled fractures!). And the show must go on … What’s next? The driller’s are presently pulling out the drill strings in preparation for the downhole measurements. The “leftovers” of the on-site science team close down the facilities, pack boxes, 2400 m of drill core have to be shipped, etc. etc. etc. During the autumn, we have to compile the data that were acquired during the operations, write an operational report, prepare the sampling party for the COSC science team … amongst others. In other words: It’s not that we don’t know what to do with our lives now
Did I write that we soon will leave the thrust zone behind us? Ah weeeeeeeellllllll … surprises are part of life! Yesterday night, before we (i.e. the "day"-shift) left the drill site, we got m-thick white and green quartzites, almost pure, only pervaded by some minor mylonite bands - Särv or Jämtlandian nappes? We didn’t know what of the two possibilities and hoped to find out tonight - but what we got instead in the first core run was 6 m of mylonite! What a surprise! And not the last one (surprise and mylonite). The next six meters were not much different - except that the lower part of the core run was stuffed with garnets, partly growing in and partly growing across the foliation. Garnet growth late during deformation(?), and the same with amphiboles. A completely different (and much less funny) surprise was to find that one of the tarp-covers for the drill core boxes was leaking. In the present weather it meant completely flooded core boxes with a diverse and colourful fungi population. Fortunately, it was only one stack with 12 boxes. We put all of them in the logging container for drying. The smell will soon decrease and conditions for geological logging will become acceptable again. Then the last core of the day came up at 23:00 - another 6 m of mylonites! Thanks to the Devicore BBT tool (at the drill site by courtesy of Devico for testing) all of the core through the mylonite zone is oriented - a real asset for subsequent studies on the drill core. Depth of the drill hole around midnight: c. 2425 m. The surface of the drill core shows first undulations after about 220 m with the same drill bit - one indication that the life of the drill bit is approaching its end.
Soon we will leave the Seve Nappe rocks behind us - that’s at least what we hope after studying the last couple of core runs. First signs of less strained and less metamorphosed sediments appear, after drilling almost 150 m through mylonites/mylonite zones - what we think is the central part of the thrust zone below the Seve Nappe. Looking backwards (or upwards), we can state that the thrust zone most likely already began somewhere between 2000 and 2050 m - i.e. has a thickness of about 300 m until now and we are not through it yet! That’s the conclusion from the drill site - the real work to define, study and characterise the thrust zone in detail will of course follow off-site. At present we really have the thrill to drill - what will we find below? Särv oder Jämtlandian Nappe(s) rocks?
6 m of drill core were lost in the hole (empty core barrel) last Thursday, before the round trip during which the gear box and rotation unit broke down. The drill core was standing at the bottom of the drill hole as whole, or more likely in pieces, and it was inevitable to over-drill the drill core with the new drill bit to catch it - with the risk that loose, rotating pieces of the lost core damage the drill bit. 3.5 m of the lost core could be retrieved. The missing 2.5 m are the first core loss in the COSC-1 drilling, at 2.2 km depth! The core pieces look really bad - oval, incised, with clear sign that large forces were acting on it. Thus, it wasn't a big surprise that the drill bit didn't last for more than 3 core runs.
Two days ago, just after midnight, drilling operations were just about to commence after the drill bit was replaced, when the operations stopped with a terrible sound. The gear box of the drill rig was broken beyond repair. Unfortunately, some broken pieces of a bearing dropped into the rotation unit and a major service is necessary to clean it out and get the unit running again. The technical/drilling team and an external expert worked hard to fix the problem, got a replacement shipped to the drill site and mounted it on the drill rig today. Thank you very much for this effort! Drilling started again today during the evening.
The last two days are a big improvement. Today 42 m of drill core were retrieved from the drill hole, drilling of another 6 m are almost finished. Thus, the present drill bit lasts already more than 100 m, which is a huge improvement over the previous ones - the result of the most recent adjustments by the drilling team.
Core drilling commenced just before midnight on the 8th August, with adjustments to several drilling parameters (amongst others lower rate of penetration & fluid flow), in a new attempt to compensate for the problems created by the drill string (high friction, low rotational speed). Until now we are very satisfied - 48 m of drill core were recovered during the last 24 hours, the present hole depth is 2088 m.
Delight, more & more delight, 2000 m DRILLER’S DEPTH and the atmosphere of a funeral - what happened? During the last two days, the old drill string was replaced by a new one. When we started drilling nobody could believe it - almost 1000 rpm while drilling at c. 1970 m. Fantastic, delight, only smiling faces at the drill site. With the new drill string we also employed Devico’s new DeviCore BBT system that COSC was allowed to borrow from the company for testing purposes (thank you very much!). In the night we gained a first experience while retrieving two core barrels with oriented core (more delight!). Drilling went well and fast, and 2000 m driller’s depth were passed at about 6 o’clock in the morning (& more delight!). But in the morning something happened - the rotational speed dropped significantly. A déjà-vu? No, unfortunately not. Another core run or two, and the drill bit was worn out, after about 41 m. A round trip … this clearly killed the show. But it could be worse - and it was worse: the drill pipes that came out of the drill hole didn’t seam to be as straight as when they went in some hours earlier. Thus, by midday, the mood at the drill site reminded very much of a funeral. Presently, a new drill bit is being tripped in, and of course we hope that all this was just a bad dream. The only thing we ask for now is hundreds of meters of nice oriented core, nothing more - at least the DeviCore core-orientation tool seemed to work very well the short time we were able to use it. We’ll keep you updated!
Presently, the hole depth is 1954 m. Two days ago, the drill bit was changed after 180 m, and everybody was very happy. The crooked drill string (the same problem as with the HQ drill string - bad quality) causes high friction and the drill bit can only be rotated with about a third to half of the design-rpm. But unfortunately, it didn't go that well this time. After only 24 m of drilling, the core barrel got stuck in the downhole assembly. After several fruitless attempts to retrieve the core barrel with the wireline, the drill string was tripped out yesterday and today. This time it will take longer than usual, because the (hopefulle straight) new drill pipe that arrived at the drill site recently will be installed instead of the crooked one that we use now - which implies breaking the -old- drill string into 3 m pieces and assembling the new one from 3 m pieces (instead of stands of 3 pipes=9 m during a normal round trip). Today in the morning the core barrel was retrieved, and it was jammed in the drill string by parts of the mud pump (see photos).
Two days since the last post and one round trip later. A core barrel was stuck and the only way to get it to the surface was to pull the drill pipe out of the drill hole. Later it was discovered that the bolt that joins the locking-mechanism to the core barrel was broken and, thus, the overshot couldn't grip it.Another discovery during the unwanted round trip was the shape of the drill pipe. Our new -high quality- Canadian NRQ V-Wall drill pipes went from -nearly straight- to the shape of cooked spaghetti (almost) after only 27 m of drilling - with the result of high friction and rotational speeds that are (very) far below the desired value for the drill bit. Despite these problems we still get very good core: good drillers can, apparently, drill with everything. Cheers for them! Depth of the drill hole at midnight: 1662 m. During the evening we did another test core run with plastic liner - this time to test the possibility to attach a plastic bag with tracer at the opening of the core barrel. Here the intention is that the core punctures the bag and that the tracer is swept around the drill core while it enters the core barrel. The results are very promising, and now everything for -sharp- microbiology sampling is set.
Yesterday evening's attempts to employ the wireline packer were unfortunately in vain. Thus, it was decided to go ahead and prepare for N-size core drilling. During the night the HQ drill string was tripped out and, after replacement of the drill bit by a "shoe", tripped in again as a temporary casing. Then the HQ drill string was sealed against the borehole wall to prevent the sedimentation of cuttings between the drill string and the borehole wall, which could render attempts to retrieve the drill string as planned after the end of drilling impossible. Presently, 1616 m of NQ drill string is assembled from 3 m pieces and tripped in - and this will take a while. If everything goes well, the first NQ drill core is expected at the surface tomorrow around lunch time.
This morning, the drillers were fishing. It's always nice with a barbecue and fresh food - but unfortunately, this time it wasn't about salmon in a nearby river. Somehow the pressure-temperature recorder was missing in the downhole assembly when the latter was recovered from the borehole after the last logging run - lost in the drill hole. After unsuccessful fishing with a magnet, it was decided to get it up by drilling. Therefore, we broke the Swedish depth record in HQ drilling today (again ) - the drill hole is now 1616 m and the lost recorder was recovered without damage in the core barrel. In the meantime, OLGA (On-Line GAs monitoring) wasn't particularly happy either. With temperatures of 30°C at the drill site and the analytical equipment in an air-conditioned container, our laboratory lady was really asking for condensation problems - and got it. Disassembling and drying the flooded gasflow-regulator helped just for a few minutes, and, thus, a second condensation trap had to be installed (the other protecting the mass-spectrometer). Now OLGA is doing fine again. But since a drill site without problems would be boring, it continued with the packer tests. The intention was to pack off the lower part of the drill hole at different depth levels for inflow/permeability measurements. Thus, the drill string was tripped out until the first target depth (about 1200 m) was reached and the wireline packer deployed. But instead of latching in its place at the lower end of the drill string, it got stuck at only 30 m depth. Back at the surface, it wasn't clear why this happened. A test of the packer before new deployment revealed also that a valve is broken and presently attempts to repair the instruments are on-going.
What would the COSC on-site science team do without the football world championship? Watching football (or watching the watchers) seems to be a good distraction during five days of downhole logging and testing. Well, we are not completely lazy, no no. Hunting mosquitoes and horse-flies of varying (ball pen dot to helicopter) size is very appreciated. But also sweating in hot containers while processing MSCL data and checking for and correcting mistakes in the scientific documentation is a favourite. For those of us who want to get a really bad cold, the climatised BugLab is the first choice, attending to the OLGA on-line gas monitoring system, data processing, etc. But since a week or so we have to share the microbiology container with about 5 tons of microbiology(!) equipment and all is really one big mess. But we have a couple of days to fix it (when we are not watching football, I mean, or eating ice cream to keep ourselves from overheating). And here some facts: Wire-line logging was finished earlier today, presently the wireline fluid sample is in the borehole to get a sample from best water-conducting zone at about 1250 m (although the total inflow to the borehole is in the order of dl/min). Then the HQ drill string will be tripped in and some pump-tests performed with wireline packers. After the HQ drill string has been installed and sealed against the borehole wall (as a temporary casing), the NQ drill string will be assembled and tripped in. We hope that core drilling will start again sometimes during the weekend.
Core drilling started again in the morning with a new drill bit, and it became clear that yesterday's second core loss was a misunderstanding. What really happened was that the drill bit got damaged, probably while drilling over the "first" core loss (the core that really was lost in the drill hole). On the core logger we can see how the diameter of the drill core increases by 4 mm within 1.5 m just before the drill bit failed, with heavy abrasion of drill bit matrix on the core. And this was about the last thing we've seen on the core logger before the electronic steering unit decided to make fun of us: Electrical motors moved only one way until a (previously damaged) ball bearing in the transducer holder gave up. After a change to a spare transducer holder first the same thing happened again, and then the steering unit gave up completely. A complete restart of the whole system could revive the electronics rack and we were happy! - for an hour or so, until we discovered that the magnetic susceptibility measurements weren't transferred correctly => find the right cable amongst 20-30 others, reconnecting in confined space without pulling others, without success, ..., ... => 6 hours after the first fault, the MSCL was back and logging. We'll see how the results are. Present depth of the drill hole: 1328 m. Terrible weather.
Yesterday, the wireline core barrel got stuck in the drill pipe during retrieval - so hard that it had to be cut out of the drill pipe with an angle grinder. In the course of the round trip the drill bit was replaced and core drilling proceeded this morning. Fresh snow on the mountains, snow and rain showers at the drill site, some sun - midsummer: somewhere in the middle between winter and summer! But beautiful. Then, in the afternoon, the core barrel lost the drill core twice! The first time the drill core apparently was left unbroken and attached to the bottom of the drill hole and, luckily, could be retrieved with another core barrel. The second time, with another core barrel/catcher setup, it did not go so well. A short piece of drill core that made it to the surface showed that the drill bit didn't keep the correct diameter and, thus, the drilling team is presently working on the third round trip in four days. Let's hope for better luck tomorrow!
Today, drilling proceeded well until quite recently - during the core run to 1295 m something went wrong and a round trip seems to be inevitable. Happy microbiologists asked us yesterday to sample a piece of the micro karst - unfortunately it was too late, we had passed the calcite-rich gneisses and didn't encounter more cavities. !But! we still have open fractures - two samples are waiting in the freezer for a happy microbiologist.
Last night the drill bit was changed after 87.5 m and core drilling continued this morning. Good progress during the day, 75 - 80 min per core run and we passed 1250 m driller's depth. More micro-karst - and the microbiologists are happy. We began with swap sampling on the surfaces and cavities, and simultaneous sampling of drilling mud in sterile sample vessels. However, to correlate the two is not so easy: we don't know in advance at what driller's depth we can do swap sampling, the lag time in the mud circulation (the time it takes to pump the drilling mud from the drill bit to the surface) is now about 35 minutes, and there's no circulation during core retrieval. But we do our best ... it's part of "the thrill to drill"!
The present depth of the drill hole is about 1230 m and after a 4 hour break this morning, to remove some damaged wireline from the winch, drilling continues at a speed of about 1 core run (3 m) in 90 minutes. Good! Still no big changes in lithology, but finally we got into a very steep fracture zone with “micro-karst” development in the calcareous gneisses. It’s not big, but still it must be good news for the microbiologists - finally something different than massive, unfracturated gneiss and amphibolite. We’ll see how it continues and keep you updated. The weather? It’s almost midsummer - this means strong winds, almost freezing at night, up to 8 or 9°C during the day and low clouds with variable amounts of rain.
Yesterday the drill hole reached 1000 m, today we ate 1000 m cake - I mean the "1000 m cake", not thousand metres of cake. The drill bit was now drilling for 80 m and still seems to be ok, but who knows - everything can happen, good or bad, at any time. It's a drilling project! When everything goes well then drilling is fast. Midnight to midnight 55 m, with 3 m core barrels at the present depth of the drill hole - we are very satisfied. It's shift changing time - a big thank you to those who go home and spend their time for the project, and welcome to the new on-site scientists.
1000 m! Today at 17:00 we crossed the 1000 m mark, unfortunately the core from 1000 m driller's depth is crushed, completely. Due to triple tube drilling: still 100 % recovery, even of the crushed parts. Presently, we assume that the fracturing is induced, and we will learn more about the rock quality in the next core runs. But we also encountered some altered surfaces with "loose material" that we sampled for the microbiologists. Some adjustments to the drill rig were made today, and we learned that replacement drill pipes for the crooked ones we have to drill with are on the way - from Canada! I hope the ships are fast …
The day began with a beautiful half-moon over the mountain and a drill bit change. Then the rain came to drown us for a couple of hours. But just after noon, reaming was finished and core drilling could continue. Today and tomorrow, Åre hosts the spring meeting of FAB, Föreningen för aktiva i borrbranschen (a driller's association, www.fab.w.se), with lectures about COSC science, technology and the Caledonides in general (Henning Lorenz, Jan-Erik Rosberg and David Gee). This very interested group visited the drill site in the afternoon, and discussions about scientific and drilling equipment were very stimulating. Furthermore, we came across the first water-conducting fractures at 986 m and began the DNA and ATP screening for the microbiologists. As you can see, we are approaching 1000 m driller's depth - most likely Iwona, Barbro & Tristan will be the lucky ones to handle this core.
A great day at the drill site: sunshine, a warm day in beautiful mountains, (still) no mosquitoes, nice drill core, OLGA is running fine (although we suspect that all gas peaks are related to the drilling) and Atlas Copco was here to fix the rig. The evening was productive, and we hope it will continue like this for some time.
We put the OLGA degasser back again, just in time for another change of a worn out drill bit. This gave us time to get started on mud sampling and mud measurement procedures, some adjustments to the DIS system and other small things that have to be done. Core drilling was continued around midnight.
Depth of the COSC-1 drill hole at midnight: 851 m - that's 51 m of perfect core in 24 hours, despite the still not solved technical problems with the drill rig and crooked drill pipes that cause extra friction while drilling. This is fantastic!
The logging was finished Wednesday, without measuring the drill hole with an orientation tool - the probe did unfortunately not work. Today, the drill pipe was tripped back into the hole, and another relative deviation measurement conducted in the drill string, with a tool from the drilling company: About 25 m at 700 m depth. After mud mixing, core drilling continued at about 9 o’clock and during the day we got more than 30 m of drill core, reaching 800 m depth at 23:00 (starting from 767 m). The drill core is still top quality, 100 % core recovery from the very beginning of the drilling, and beautiful - marbles, gneisses, ductile deformation with folds etc. cut out by the drill in 3 dimensions. During the day we were able to replace the OLGA degasser’s motor, with help of the technical and drilling team - they were warming the shaft with a 600°C heat gun while battering it off with a sledge hammer. Thing can’t get more useless than useless, the situation could only improve. Tomorrow, Johan, the on-site engineer, will connect it and OLGA will be running again! Presently, the mood is high and we hope it will continue in such a way for some time.
More the two days of logging (natural gamma, temperature, full waveform sonic, 3-arm caliper, resistivity, density) and a very tired logging team - presently, measurements while pumping are done for the hydrogeologists. The on-site science team has caught up on the core logging and is now in the process of switching groups, just in time for the start of core drilling operations tomorrow.
On the morning of Sunday, 25th May 2014, the COSC-1 drilling reached a driller’s depth of 767 m. The driller’s then rinsed the drill hole and removed the drill string in preparation for down-hole logging operations that were scheduled to start on Sunday night. Per-Gunnar Alm and his team from Lund University came in the evening and started setting up their things. A problem with connection to the electrical grid delayed the operations, which will be started up with generator power as soon as possible. Because there is no drilling activity, on-site science team switched to having 2 persons in 8 hour shifts (from 3 persons in 12 hour shifts), so that some people can catch up on well needed rest. We will finish the multi-sensor core logging on all existing core during Monday if everything goes according to plan and then we’ll see what needs to be done and what we can do while waiting for the loggers to finish.
We are testing the placement of Olga, the online gas monitoring system. This system will be used to measure potential gases transported from the borehole with the drilling fluids. So far it looks like a suitable solution. We will soon switch it on and check if it works. The drill bit wore out after only 55 m, the drill pipes were measured and seem to be deformed, and we are still waiting for adjustments to the drill rig.
Group 1 of the on-site science team has taken over again, and is presently finishing the documentation of the last boxes of drill core from today. Present depth: 554 m. Now the drilling crew changes and there will be some time to re-log the very first cores on the MSCL, from the time before we discovered all secrets of calibrating and operating the machine. In the late afternoon, we had a presentation about the project for the public at Fröå Gruva, with a subsequent visit to the drill site. 16 people attended and, we think, are now thinking positive about the project.
Today, core drilling started again. Better to continue instead of just letting the time (and the money for the daily costs) pass by. Supermix, a biodegradable additive to the drilling mud, will from now on lubricate the drilling (and make the drill cores slimy and stinking ... well, it could be worse,e.g. getting no cores at all!). Drilling will be slow until the other problems are fixed and it is decided how we go on. Still, we get about one 3 m core run per hour. Thus, we reached 500 m today. Now it's time for group 2 to go home, and group 1 will take over, again. Many thanks to everybody for the good work!
Reaming of the drill hole after the last drill bit change was finished and we got some meters of drill core in the early morning, before the drillers performed a deviation measurement in the drill hole - something is wrong, the rig doesn't deliver the power and rpms that are necessary for proper operation and, obviously, there are problems with the drill hole. Maybe the latter is a result, in part, of the former, and then there is geology. The results from the deviation measurements are not very encouraging: about 11 m at 465 m depth. The on-site science team used the break to re-log the drill core we missed while the p-wave sensors were missing from the MSCL, and we had time to think about OLGA, the on-line gas monitoring. Core drilling will continue later this night or in the morning.
The Core Logger is multi-sensor again, with a lot of tape and loctite. Drilling problems give room to think, although they aren't really favourable for the project. The hero of the day is Tina Kollaske from BGR - she reminded me how the MSCL at BGR works and how to instruct the instrument to lift the upper transducer - exactly what Bjarne remembered from our visit at BGR. Apparently, rolls are not for rolling, at least not on rock. Lifting the transducer from the rock surface is important for the transducer rolls’ survival! So now the sensors are mounted back on the MSCL, the only undamaged transducer is the rolling one in the lower holder (keep on rolling!), and the new-but-already-damaged transducer is, completely covered with electrical isolation tape, in the upper holder. Fixed with more tape against rolling it should always come in contact with the core at the same spot, and, thus, any effects of the tape should be accounted for by the calibration. Now we have to see how long this arrangement will last - 5 minutes or 5 months? I assume the oil will leak through the tape again sooner or later, probably sooner. But if we just get the refurbished transducer from Geotek in time we might be fine!
Today, the Multi-Sensor Core Logger lost the "multi" - now there are only two sensors left. More p-wave transducers broke during the day and we had to remove the p-wave/core-thickness deviation arrangement. I learned that the rubber-roll-transducers are only for soft-sediment cores in plastic liners and not for hard-rock cores (these are too abrasive). And that Geotek would readily deliver the correct sensors for 15000 € (+ 5000 € delivery and training) ... ... ... ah, well, we can do without them.
Some days aren't as good as others. It began with printing problems in the DIS - a minor thing, but it upset the whole workflow and, thus, produced stress. If drilling goes well, then there is no time to fix things. And just as we got used to it, the new p-wave transducer of the MSCL got punctured. But last time this happened, we also got spares from an old core logger. Yesterday, we had exchanged some mechanical parts. Today we took also the transducer. We can only hope that it will last. Once we got help with the DIS (thank you, Ronald) and had fixed the core logger, the drill bit was worn down and drilling stopped at 10 a.m. (after 30 m of top quality core since midnight!). The bit is now changed, but again, as last time, the drillers have to ream up the hole before they can continue with core drilling. Maybe there's something wrong with the material? Presently, (18.00) we are waitung for the core drilling to continue.
Today we reached almost 400 m depth while we could celebrate core run number 100. What we find in the cores? Migmatites, migmatites, migmatites. And migmatites of course.
After a break because of a mishap with the core catcher, drilling continued at about 2 pm, and in the following 14 hours we got about 40 m drill core. The geological documentation is really difficult, to find an appropriate balance between speed and detail. The rocks are complicated and our discussions could be long while we get three metres of new core about every 45 min. Thus, we just continue logging - a field description is not a laboratory study .. The present depth of the drill hole is c. 340 m and core-recovery about 100 %.
The first drill bit wore out after about 180 m of drilling, 284 m depth of the COSC-1 drill hole. Something is not optimal with the lowermost part of the drill hole and the drillers have to ream/"redrill" in order to reach the former depth with the new bit. This gave us some time to catch up with the core documentation, to take the first samples for the study of (time-dependent changes in) thermal conductivity, to get the necessary non-scientific tasks done. And to almost be idle ... but we have now experienced how things can changes very fast from one extreme to the other. Soon the race will start again!
Today, drilling around the clock began. Drilling goes faster than everyone expected, about 45 min for a 3 m core run. The on-site science team just changed and the new people are not yet accustomed to operations. But in any case, the on-site science team would not be able to keep pace. Drilling depth at 18: ca 260 m. Core recovery about 100 % in every core run today!
Finally, the multi-sensor core logger is running and we are confident that we get meaningful data. We replaced a power supply, got some calibration pieces done at a local workshop, brought in an oscilloscope from Uppsala - and used the combined brain-power of our geophysicists!
The depth of the drill hole today: 149 m.. Drilling is very fast at shallow depth, and once core is produced it is impossible to keep pace with the documentation and logging. Presently, it is an advantage that drilling is only daytime. The on-site science team can catch up during night. The geologists were amazed to find the first garnets at c. 135 m (see photo). The first group of drillers went home and a new group will come and be intrtoduced to the drill rig and project. We expect 24/7 drillling to commence in the middle of next week
Core drilling commenced after the concrete of yesterdays cementing work had cured, and after some adjustments at the drill rig and the MWD system setup. 6 new core runs were retrieved, hole depth about 125 m.
The first core in the COSC drilling project was retrieved - everybody at the drill site is happy, including the drillers who battled the concrete of last year's cementing of the surface casing. Today the remaining c. 10 m of concrete above the casing shoe of the surface casing was drilled through with the inner casing. Then diamond core-drilling commenced for two core runs (3 m each) before drilling was suspended to pressure-test the surface casing and installations.
Finally, the diamond core-drilling rig is exactly in place above the conductor casing and the drillers began to install the inner casing (of the same inner dimension as the core hole) in preparation for the core-drilling operations. We hope that we get started tomorrow. About 20 m of concrete plug from the cementing of the conductor casing before we will reach the bedrock.
The upper p-wave transducer and core diameter sensor of the MSCL got punctured during testing. Spares are rare, or more precisely, expensive. Waiting for a solution ...
