Thursday, December 4, 2014

DFDP-2 @ 828 m, wireline logging, schools and locals

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

A lovely morning with drilling progressing smoothly.  2/12/14.  Photo R. Sutherland.

We made solid progress over the last week. Our plan was to stop and set steel casing at 800 m depth, but we always knew that a detailed analysis of rock cuttings would be needed to confirm the depth of the fault. We reached 828 m depth after dinner yesterday.

The cuttings geology team is telling us that we should drill a bit deeper before we cement casing into the borehole, but we took a break from drilling last night for several reasons:
(1) drilling equipment needs to be checked and maintained;
(2) we wanted to survey the orientation and state of the borehole; and
(3) geophysical measurements made deep in the borehole today will inform our decision about what to do next.

Geophysical instruments (sondes) are lowered into the borehole on a wire rope from a special winch that precisely measures depth. Cables inside the wire transmit data to a computer at the surface. This process is called ‘wireline logging’.

Wireline logging sonde.  Photo J. Thomson

There are many different types of sonde. Today we will be measuring: electrical conductivity and temperature of the mud in the hole; seismic wave-speeds and electrical conductivity of the rock; natural rock radioactivity; borehole orientation; borehole shape; and images of the borehole wall that reveal rock fabrics and fractures.

This video gives a bit of an explanation of some of the wireline logging tools we use:

We have had several open days recently with lots of locals and two schools coming to visit.

Carolyn Boulton explains rock cutting and crushing to Hokitika High students. 4/12/14 Photo J. Townend

Jennifer Eccles explains earthquake sensors to Hokitika High students in the rain. 4/12/14 Photo J. Townend

DFDP-2 is funded by: the International Continental Scientific Drilling Program (ICDP); the Royal Society of New Zealand Marsden Fund; GNS Science; Victoria University of Wellington; University of Otago; NZ Government (MBIE); UK Government (NERC).