C2FN : Centre de Carottage et de Forage National

Ocean Research & Developments

Cinema Program

Through collaboration with Patrice Woerther and Jean-François Bourillet (IFREMER), a new coring approach has been developed, based on the observation that piston core samples used to be stretched, as a result of the stretching of the main cable that lifts up the piston while the corer falls down, creating an over-depression that distorts the sediment layers. Sensors has been developed to log the cinematic of the coring operations, and a software has been designed to model the stretching of the cables, and to give accurate settings for the core no to be distorted. The last version of this software – Cinema V3.0 – is now operational on both IFREMER and C2FN coring vessels, and gives exceptional result, optimizing the recovery rates : cores takes more layers (of a better quality) than they used to, and go back longer in time (2 million years).

Calypso IV Project

A new corer generation is being designed by the C2FN : a giant corer with an instrumented triggering system. An altimeter is integrated on the down side of the core head, and it communicates with a heavy load acoustic releaser through a communication electronic system housed in a pressure tube. There is no “classic” mechanical triggering system and no pilot weight. There multiple advantages :

• A much better free fall height control and a feed back that did not exist before as the altimeter logs its signal.
• A link with the Cinema software which allows a much more accurate level correction, then a very good evaluation of the core quality.
• A much faster and more secured handling. It saves a lot of “shiptime” and then optimizes the campaigns.

Security Jaw

A new system has been designed to secure the corers, and prevent them from staying stuck in the sediment. It is made of a mechanical steel jaw coupling the pipes to the core head, kept closed by an acoustic releaser that can triggered on an command sent from the ship.

As the core head tends to be more and more instrumented with expensive equipment, it is becomes a priority to secure it and prevent its loss. This system is now fully operational after a 3 years development.

It is also an advantage for scientists, as they use not to dare giant length in unknown sediments, fearing to lose the corer and to penalize the campaign, they can now try safely to take as long sample as the winch can extract, optimizing their results.

Instrumentation

The giant corer is now equipped with loggers that enrich a single core operation with simultaneous CTD cast and water sampling. Currently, the corer is implemented with :

• A CTD probe (RBR – XR620). It logs temperature, pressure and conductivity during the whole operation. It is also equipped with a fluorometer.
• A 1,7l Niskin bottle mounted on a triggering system that closes the bottle when the corer falls in the sediment. The sample of interface water taken is very interesting for cores studies.
• Other instrumentation projects are under development. For example, an interface corer that would trigger when lifting up the Calypso, additional samplers for water or plankton, etc.

Ropes and cables studies

New textile cable technologies are studied to replace steel cables. Easier to use, lighter, and often stronger, they are already in use for so-called “oceanographic” cables (several thousand metres long cables operating the equipment), and are now in use for the “pilot” cables (holding the counter weight of the Calypso).

Trials are carried out to replace the steel “piston” cable of the Calypso with HMPE ropes.

In parallel, studies have been published comparing HMPE and Aramid, regarding the special requirement of piston coring. It will lead to the development of a new coring cable in the CLIMCOR Equipex project (see further).

Acoustically released Multicore

A study is actually carried out to implement on a multicore a new structure to welcome an acoustic releasing system and a video camera.

The mechanic system used to be problematic at big depths or when the sea is rough, because of the high sensitivity of the multicores. An acoustic triggering system would prevent these problems.

This small corer is not subject to big shocks or heavy handling, and it could easily welcome a camera. It would help knowing better the site’s sediment. This adaptation is under development.

Sampling and Logistics

C2FN-Ocean is also looking after sampling and logistic tools ; it has already developed handling facilities, laboratories in containers, sampling devices, etc.

It works in close link with Geotek to update and improve its Multi Sensor Core Logger.

More generally, C2FN is in charge of the whole coring logistic of the R/V Marion Dufresne and purchases and/or creates any kind of sampling or handling tools needed.

The CLIMCOR Project 2012 – 2019

(ANR-II-EQPX-0009-CLIMCOR)

The French Government has allocated special budgets to “scientific equipment of excellence” and chose, among others, the C2FN CLIMCOR project of coring equipment improvements.

Regarding the C2FN-Ocean, the CLIMCOR project is based on two major work packages :

• The development of a new coring cable stronger and much stiffer, specially adapted to the coring operations requirements.
• The upgrading of the coring winch of the R/V Marion Dufresne, to adapt it to the new cable and to its working loads.

For more information about CLIMCOR, please visit : http://climcor-equipex.dt.insu.cnrs.fr