International Continental Scientific Drilling Program
April 21, 2017 update
Distribution of perfluorocarbon tracer added to drilling mud in 3 freeze-shoe cores collected in the DES yard in Salt Lake City in March 2017. The level of contamination is expressed as the fraction of drilling mud contained in pore water extracted at multiple intervals from the edge of the core, close to the liner, and in the center of the core. Not surprisingly, contamination of pore water with ~10% (10^-1) drilling mud is observed near the top of two of the cores, at 15 cm depth in ALN Hole 2 Core 1 and 2 cm in HPC Hole 2 Core 2. The lowest levels repeatedly detected in the center of both HPC Hole 2 Core 2 and Core 4 are on the order of 0.01% (10^-4) and probably represent cross-contamination during processing of the core samples (cutting, dragging of a spatula across horizons, sub-sampling, etc.) rather than actual contamination while coring. Data from HPC Hole 2 Core 2 shows comparable levels of drilling mud along the edge and in the center of the core, whereas HPC Hole 2 Core 4 was clearly much less contaminated in the center. ALN Hole 2 Core 1 was more contaminated than either HPC core, but failed to freeze at the bottom on this particular deployment and may therefore not be representative of normal working conditions. These preliminary results (a more detailed error analysis is underway) confirm that this extremely sensitive method, proposed for deployments in West Bengal, India, provides a very useful constraint on core sample integrity and that the freeze-shoe tools can collect sediment material with minimal if any contamination with drilling mud. The sampling and analyses were carried out by Arthur Spivack, Kira Homola, and Dennis Graham from the University of Rhode Island.
March 17, 2017 update
Three cores were recently recovered in the DES yard in Salt Lake City, Utah, and sampled for a fluorocarbon tracer that was added to the drilling mud as a test for contamination. Two of these had frozen plugs at the bottom and were recovered using the freeze shoe-modified HPC FS 1.5M. The core barrel of this new version of the HPC FS has the same dimensions as the original HPC. The tip of the freeze shoe-modified ALN was not frozen on this occasion, but the same device successfully recovered a frozen plug several time from a depth of up to 200 m in March 2016. The total of 97 tracer samples collected from the 3 cores, along with drilling-mud monitoring samples, are being analyzed by gas chromatography at the University of Rhode Island and the results will be posted as soon as they become available, most likely before the end of March. Participants in the most recent field work included Brian Grzybowski and the drilling team from DES, Art Spivack and Kira Homola from URI, and David Schlottenmier from Bridger Scientific.
ALN FS: 0.6 m of clay (9.8-10.4 m below ground)
HPC FS A: 1.5 m of sand (10.4 -11.9 m)
HPC FS B: 0.9 m of sand (12.5-13.4 m)
Combined with previous tests conducted at a different site near Salt Lake City in March 2016, these results confirm that liquid carbon dioxide released in situ can be used to recover aquifer sediments with a frozen plug at the bottom from a depth of at least 200-m.
Photo 1. Extraction of inner assembly from drill rods with HPC 1.5 m FS extended on the rod.
Photo 2. Temperature at the frozen core tip with the HPC FS 1.5M hanging in a vertical position on the wireline, after extraction from the drill rods (-1.1 °C).
Photo 3. Measurement of core tip temperature after placement in the mouse-hole with dry ice and removal of the core from the too.
Photo 4. Kira Homola and Art Spivack from the University of Rhode Island sampling a core for the fluorocarbon tracer.
Background: Columbia University and partner institutions have been conducting since 2000 field work to determine the health effects of exposure to arsenic contained in well water, the mechanism of the release of arsenic to groundwater, and ways to effectively reduce exposure of the Bangladesh population. This on-going program, supported primarily by NIEHS and NSF, was supplemented in March 2004 with a grant from the Earth Clinic of the Earth Institute at Columbia University (http://www.earthinstitute.columbia.edu/) to develop mobile-phone technology for accessing a spatial interpretation of an existing database of 5 million well tests at the village level.
Achievements: The SMS-based version of the “Welltracker” technology is operational and has been tested in Columbia’s study area of Araihazar. A dedicated computer at the University of Dhaka connected to a mobile phone receives requests for a particular village, queries the database, runs a simple algorithm, and returns a text message that lists the “start depth” for drilling to groundwater that meets the WHO guideline for As as well as a probability estimate that the start depth is correct (see illustration). For other villages, the text message indicates that a “start depth” cannot be determined from the depth distribution of arsenic in existing wells. The database currently includes 30,000 tests from Araihazar provided by the Bangladesh government and an additional 270,000 tests in other areas made available by UNICEF. A web-based emulator is available at http://www.ldeo.columbia.edu/welltracker/. The World Bank office in Dhaka has engaged the Bangladesh government in a discussion to make the entire database accessible through Welltracker.
Click here to watch 18 min. video describing the well drilling procedure and the use of cell phones in Bangladesh. The video was produced by Franck Dubois (http://www.bleu.net/)
Click here to download Amy Schoenfeld's 2005 MS thesis entitled “Area, Village, and Household Response to Arsenic Testing and Labeling of Tubewells in Araihazar, Bangladesh”.