Bottom Hole Assembly

About 10 days ago, drilling was stopped at the Alpine Fault drill site so that geophysical measurements could be made down the borehole, and the bit could be replaced.

This involved lifting all of the drill rods out one by one and stacking them next to the rig.

Next to come up was the bottom hole assembly (BHA) comprising these thick steel pipes that Rupert Sutherland is describing to the camera in this image.

Last to appear was the business end of the drill string including the drill bit itself.





This photo shows the bit being replaced using some impressive sized hand tools:

The view looking down into the top of the borehole - 400 metres deep and filled with mud.

Here is the video of Rupert explaining the Bottom Hole Assembly:
Once the geophysical measurements were taken down the hole (more about these later), the Bottom Hole Assembly was put back together and lowered back down the borehole. Unfortunately disaster struck when the wire snapped and 7 tonnes of unattached BHA dropped down the hole. To cut a long story short, this delayed progress for about a week, until finally the detached parts were fished out of the hole using a variety of highly specialised methods. You can read a little more about these events here in Rupert's Blog:
1.The Calamity.  
2. Landing the Fish