Center for Marine Environmental Sciences MARUM
Prof. Dr. Gerhard Bohrmann
Prakla Bohrtechnik GmbH
Prof. Dr. Reiner Homrighausen
Clausthal University of Technology, Institute of Petroleum Engineering
In the frame of subproject A3 drilling tools are to be equipped with autoclave technology and used for sampling of hydrate deposits.
To evaluate the quality of gas hydrate deposits, while considering hydrate distribution and concentration to be determined within the occurrences, application of drilling technology is essential. Since gas hydrates decompose while decompressed or heated during drilling and the gas released is lost, a combined autoclave drilling technology is necessary to preserve the in situ pressure. Using this approach accurate quantification of gas hydrate is possible.
Two lines of development using autoclave technology, which allow for recovery of gas hydrate bearing drilling cores under in situ pressure, are pursued in the framework of SUGAR. The lines aim on different operating conditions.
In the first line an autoclave technology is to be developed and integrated into the transportable sea floor drill rig (MeBo) developed at the MARUM in Bremen. The MeBo, which can be launched from conventional ships without boring platform into water depths of up to 2000 m, is used to recover cores from unconsolidated sediments and rocks of 50 m length, so far.
The second line aims on the development of an autoclave system with associated drilling technology, for sampling of soft sediments and gas hydrates. This system is not limited with respect to water depth and thickness of sediments to be sampled. The employment of this system will be restricted to drilling ships.
Both approaches provide new technologies, which can be adapted to specific conditions and requirements of sediments to be drilled during gas hydrate sampling.
A prerequisite for investigations of natural gas hydrates under in situ conditions, is the maintenance of pressure and temperature conditions as present at and within the seafloor during recovery. The processing of pressure cores after recovery includes:
- Non-destructive visualization of the sediment by means of computer tomographic visualization
- Controlled gas release for quantification of the natural gas inventory
- Sampling of the gas released for subsequent analyses
|Abegg, F., Hohnberg, H.J., Pape, T., Bohrmann, G. & Freitag, J.||Development and application of pressure-core-sampling systems for the investigation of gas- and gas-hydrate-bearing sediments||2008||Deep-Sea Research Part I-Oceanographic Research Papers|
Vol. 55(11), pp. 1590-1599
|Dickens, G.R., Paull, C.K. & Wallace, P.||Direct measurement of in situ methane quantities in a large gas-hydrate reservoir||1997||Nature|
Vol. 385(6615), pp. 426-428
|Heeschen, K., Haeckel, M., Hohnberg, H.-J., Abegg, F. & Bohrmann, G.||Pressure coring at gas hydrate-bearing sites in the eastern Black Sea off Georgia||2007||Geophysical Research Abstracts|
|Heeschen, K.U., Hohnberg, H.J., Haeckel, M., Abegg, F., Drews, M. & Bohrmann, G.||In situ hydrocarbon concentrations from pressurized cores in surface sediments, Northern Gulf of Mexico||2007||Marine Chemistry|
Vol. 107(4), pp. 498-515