Tuesday, 7 November 2017

Corinth Active Rift Development: petrophysical measurements in the first borehole

IODP Expedition 381
View 4: looking forwards to the first downhole logging

The petrophysical measurements that are taken offshore include both petrophysical measurements on the recovered core and measurements taken in situ in the borehole by downhole tools. The core measurements on the first hole of the expedition are well underway and we are excited that the first logging is due to take place fairly soon. The next blog post will contain news from offshore on this!

The last blog post introduced the Geotek™ Multi-Sensor Core Logger (MSCL), which is a piece of equipment that EPC staff and those scientist who operate it offshore become very familiar with, and on Corinth Active Rift Development: IODP Expedition 381, EPC’s Laurence and Abah from the science party are working in opposite 12 hour shifts. The MSCL has sensors measuring magnetic susceptibility, electrical resistivity, P-wave velocity, gamma density, and natural gamma radiation, each of which have their own special ways in which they contribute to the expedition aims. Offshore these measurements are also helpful in providing the petrophysics team with some prior understanding of the borehole before downhole logging commences.

Laurence Phillpot introducing Abah Omale to the expedition MSCL logsheets. (credit: E. Le Ber)

The downhole logging measurements plan and operation is coordinated by the Expedition Petrophysics Staff Scientist, Erwan, requiring detailed discussions offshore with the operational team, the Expedition Co-chief Scientists and the logging engineers. In a perfect formation, in a perfect hole, logging is straightforward and each tool can be run in open hole down to the bottom and measure all parts of the borehole. That can and does happen! By this phase of the operation, analysis of the MSCL measurements and observation of the lithologies recovered can help to inform the logging program in this first hole. Where parts of the hole are anticipated to be less than perfect (which also can and does happen!), the logging team consider options such as logging the hole in more than one phase. Again, watch for the next blog post to find out more about the first downhole logging from Corinth Active Rift Development: IODP Expedition 381 …………. or if you can’t wait for that, check out the recent articles on the Expedition 381 blog!

Laurent Brun and Erwan Le Ber testing logging tools. (credit: L. Phillpot)


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