Other
Scientific paper
Dec 2005
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2005agufmos31d..02c&link_type=abstract
American Geophysical Union, Fall Meeting 2005, abstract #OS31D-02
Other
3004 Gas And Hydrate Systems, 3036 Ocean Drilling
Scientific paper
The downhole logging while drilling (LWD) and conventional wireline (CWL) logging operations on the Gulf of Mexico Gas Hydrate JIP Cruise were designed in part to obtain data needed to assess the occurrence and concentration of gas hydrates at several key sites within the Gulf of Mexico. LWD and CWL operations were conducted in two different offshore lease areas, Atwater Valley 13/14 and Keathley Canyon 151, in water depths ranging from 1280 to 1330 m. LWD tools measure in-situ formation properties with instruments located in the drill collars immediately above the drill bit. The LWD tools (on 6-3/4 inch collars) used during the GOM-JIP drilling program included the resistivity-at-the-bit GeoVision tool (GVR6), the EcoScope tool (DVD with APWD), the TeleScope MWD tool (TeleScope), a magnetic resonance while drilling tool (MWD-ProVision), and the azimuthal density neutron (VDN) tool. The only CWL tool deployed on this cruise was the FMS-sonic tool string, which consisted of the Formation MicroScanner (FMS), a general purpose inclinometer tool (GPIT), and the dipole shear sonic imager tool (DSI). The vertical seismic imager tool (VSI) was also deployed during the GOM-JIP drilling program. As noted above, LWD operations were conducted in the Atwater Valley 13-1 and 14-1 wells, and in the Keathley Canyon 151-2 well. Conventional wireline logging operations included the deployment of a dipole shear sonic imager tool (DSI) logging string and a vertical seismic imager tool in the Keathley Canyon 151-3 well. The downhole well log data from all four wells surveyed showed some evidence of gas hydrates. A review of the well log data from the two Atwater Valley wells shows little evidence of significant gas hydrate occurrences, other than several thin, possibly stratigrahically controlled gas-hydrate-bearing intervals. The LWD logs from these wells further suggests the presence of a complex pore water fluid regime, with variable well log inferred pore water salinities. It is important to highlight, however, that the well log and seismically inferred fluid salinity and possible free-gas feature associated with the Atwater 14-1 site is limited in spatial size and likely exhibits only local influence on gas hydrate stability conditions. LWD gamma ray measurements suggests that the Keathley Canyon 151-2 well penetrated mostly a fine-grained clay dominated sedimentary section, except for one thick sand section at 95-110 mbsf. There are also several other sand rich sections deeper in the well. The most notable characteristic of the Keathley Canyon 151-2 well is a high resistivity interval within the section from about 220 mbsf to 300 mbsf, which probably indicates the occurrence of gas hydrates. LWD derived resitivity-at-bit images from this high resistivity interval, also reveals the presence of numerous steeply dipping gas-hydrate filled fractures throughout this section. The well log data from the Keathley Canyon 151-2 well again shows that the occurrence gas hydrates is strongly influenced by the presence of reservoir type sediments, such as sand. In the case of the Keathley Canyon 151-2 well, we apparently found a fractured controlled gas hydrate occurrence.
Collett Tim S.
Conte Alberto
Goldberg David S.
Hoong H. F.
Loh L. L.
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