Lithological features analyzed by Pressure Core and Wireline Logging Data of the 2nd Offshore Gas Production Test Site, NE-Nankai Trough, Japan
Abstract
For the purpose of grasping the lithology of the gas hydrate reservoir of test site, the MH21 consortium, the Japanese national gas hydrate research program, planned drilling operation to retrieve core sample and wireline logging. Two wells, CW1 and CW2, were planned to acquis core/logging data, to reveal the reservoir heterogeneities and to clarify the reason of uncertainties of fluid conductivity. The CW1 was placed between the monitoring well and gas production well, 10m off from the CW1 for obtaining effects of gas production test. The CW2 for studying primary sediment properties was about 20m off from the production well toward west. From March to April, 2018, we drilled these two holes to carry out the pressure-core sampling, and wireline logging in the same borehole. The coring was successfully carried out and wireline logging measurements were obtained using borehole formation micro-imager, sonic tool, and nuclear magnetic resonance tool. The image of borehole taken by formation micro-imager, had enough qualities to compare with the pressure cores, which have the better resolution than images we had been taken before. We now progress core data and logging data comparison.
Preliminary results are mentioned as follow. Heterogeneity distribution of gas hydrate was confirmed again. Movable water confirmed by nuclear magnetic resonance (NMR) nearby CW1 was greater than those of CW2. The T2 distributions throughout CW1 well showed the longer than those of CW2 well, i.e., larger pore space existence. The CW2 showed shorter T2 distribution, i.e., little volume of pores filled with movable water. The tendency of resistivity peaks throughout CW2 was larger than those of CW1. These features means that CW2 was consisted of sand and mud alternation layers with higher gas-hydrate saturation than those of CW1. On the basis of the grain size analysis, water bearing zone had been mentioned as the muddy layers from the previous study but it was clarified in the alternation of sand and mud layers after completion the acquisition.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFMOS23D1653S
- Keywords:
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- 3004 Gas and hydrate systems;
- MARINE GEOLOGY AND GEOPHYSICS