Subject : Colônia drilling
Brazil, SP, Sao Paulo, Pareilheiros, Colônia crater (23.874°S - 46.705°W)

PI : Marie-Pierre Ledru, IRD, ISEM (Institut des Sciences de l’Evolution Montpellier), UMR 5554
CNRS staff for DT-INSU, C2FN : Laurent Augustin and Alain de Moya

For Colônia drilling, a support from C2FN-DT-INSU was required in 2017. But initial solicitation started in 2011 with providing an offer for a 50m drilling with a recovery core. In the mid time scientific project and drilling request did change several times. In 2014 the project became an ICDP project and a workshop was financed to evaluate the feasibility of 2 drilling 450m and 500m depth in order to reach bed rock and collect sample indicated meteorite impact traces possible origin of the crater. Simultaneously to the workshop, a one day hand drilling reached 15m with a recovery core with C2FN support.
In 2016, with ICDP refusal, PI decided to switch to the original project and got a LEFE and a BNP Paribas grant and an official support from DT-INSU for a 50m drilling and its recovery core.

C2FN support

Two kinds of support :

• Feasibility and drilling requirement writing and the search of a local subcontractor.
• Supervising in situ drilling operation and bringing expertise and knowhow.

Drilling operation start

Acheminement du matériel / Equipment transportation on site

Drilling operation started end of July beginning of August. After a reconnaissance penetration test, performed beginning of July, SONDOSOLO, the subcontractor, decided to drill with a hammering and pushing corer with tubing.

First part : hammering with tubing

SONDOSOLO arrived on site with one day of delay and an equipment not similar to the one described on the offer. After the tests performed beginning of July, we decided to be confident and to leave the company to drive his task as they indented with the equipment brought: A tripod with hand hammering system. Without any handling means, all equipment was carried by hand to the site and one day was necessary to set up all the equipment.

Tripode et battage / Tripod and hammering

Immediately it appeared that the tripod was not high enough to handle 3m rods. After 2 days, a first drilling abort at 3m and a few modification on the drill, the second drilling was interrupt at 13.5m for lack of penetration.
By Friday 4/08 at 14:00, we intimate the company to bring, on site, by the days after at 8:00, a drilling equipment similar to the one described on the offer, if not contract will be break off…

The day after a new equipment was on site with the promise of a new drilling team for Monday 07/08.

Carottier SONDOSOLO / SONDOSOLO pushing drill

Arrivée de la sondeuse rotative 6T / 6T new drill rig on caterpillar

Second part : pushing with rotary tubing

Installation des équipements / Drill pad setting up

Drilling operation restated really on Monday after mid-day. All Saturday was needed for drilling pad setting up. Tuesday evening, 30m depth was reached and a 51m core completed by Thursday noon with some difficulties.

Préparation et mise au point / Preparation and strategy briefing

Travail nocturne aux phares de voiture / Night time working with car light

Drill rig was moved by a few meters to start the duplicate core at the first time on Friday. 30.80m depth was reached Friday evening and 45.80m by Saturday evening. On Monday by mid-afternoon, duplicate core was achieved at 50.30m under PI supervision. C2FN staff was already in the retrograde plane on Sunday 13/08 as initially planed.

Marquage des carottes / Core labelling

Collection de carottes / Core collection

La carotte des 51 m / 51m depth core

Entre les deux sondages / Drill pad in between the two cores

Results

Initial goal is reached with a 51m core and a 50.30m duplicate core completed with a recovery rate over 95%. This give a 50m long sediment continuous sequence.

Lesson learned

• SONDOSOLO, in spite of penetration tests performed ahead of the drilling, underestimated penetration strength and make a wrong choice for the equipment the first week. Drilling team never performed continuous sampling before. Continuous sampling require a specific work and a lot of carefulness in work execution. We did teach SONDOSOLO team a lot.
• In spite of drilling requirement and detailed technical specifications, bad surprises occurred. A visit to the company workshop seems to be indispensable to check equipment status, but seems very delicate to implement, before the company selection.
• The drill designed by the SONDOSOLO, especially for this drilling, is very interesting in spite of few things not optimized. C2FN got inspired by this design to implement it on conventional wire line rotary corer.

Acknowledgements

• A big thanks to Marie-Pierre Ledru, program PI, for her confidence in C2FN for the preparation of his mission, the search and the selection of a local subcontractor and the drilling supervision.
• Thanks again to Marie-Pierre for her kindness and daily organization carefulness (airport pick-up, on site transportation and lodging).

Reach out

Financed by BNP Paribas, this drilling operation was widely covered by the media :

• One photographer from Magnum agency spend 5 days with us to cover the event and the area around : https://we.tl/BdByZTMSvc
• Sao-Paulo regional TV and Brazilian National TV cover the event for the daily journal (3min in Brazilian) : http://g1.globo.com/sao-paulo/sptv-...

Paper

Ledru, M.P., Reimold W.U., Ariztegui, D., Bard E., Crósta, A.P., Riccomini, C., Sawakuchi A.O. (2015) Why drilling deep in the Colônia Basin (Brazil). Scientific Drilling. 20, 33-39.

Contact

Laurent Augustin