Monday, December 8, 2014

892 m, decision time, steel casing

Rupert Sutherland, GNS Science and Victoria University of Wellington
John Townend, Victoria University of Wellington
Virginia Toy, University of Otago

The view downstream. It is 600 m to the bridge. 4/12/14.  Photo J. Townend.
We reached a very important decision point today. At 8 a.m. this morning at 892 m depth, we decided to stop drilling and to cement casing into the hole. A bunch of things now have to happen so that we are ready to start the collection of rock core.

We first have to clear the borehole of rock chips and cool it by circulating mud. The mud emerges at 52°C. How hot would it be if we weren’t drilling? We will know in the next week or so.

Before we cement PWT steel casing (5.5 inch = 140 mm diameter pipe) into the hole, we will use wireline tools to log the hole. This is our last look at the borehole wall before steel and cement get in the way. Logging will start about midnight tonight.

New PWT casing is ready to go. Photo J. Townend.

The process of putting casing in the hole is fairly complicated. It has to get down and around the J-bend in one piece. The bottom of the hole is now 250 m horizontally towards the road bridge and away from the drill site (see our last blog). Next, we have to run another smaller steel pipe next to it – this is going to be a tight fit. Then, we have to insert a fibre optic cable down the second pipe. Finally, we have to pump 25 cubic metres of cement down the inside and back up the outside of the casing without it leaking into the rock or setting hard before we are finished.

If all that happens without a hitch, then we will be hoping to collect our first core this weekend.

View from the geologists’ cage.  J. Townend.