HR: 09:15h
AN: OS31D-05    [Abstracts]
TI: Results of Wellbore Stability Modeling for the Gulf of Mexico Joint Industry Project on Hydrates Leg I
AU: * Birchwood, R
EM: rbirchwood@slb.com
AF: Schlumberger Data and Consulting Services, 1325 South Dairy Ashford Road, Houston, TX 77077 United States
AU: Noeth, S
EM: snoeth@houston.oilfield.slb.com
AF: Schlumberger Data and Consulting Services, 1325 South Dairy Ashford Road, Houston, TX 77077 United States
AU: Sayers, C
EM: csayers@houston.oilfield.slb.com
AF: Schlumberger Data and Consulting Services, 1325 South Dairy Ashford Road, Houston, TX 77077 United States
AU: Hooyman, P
EM: hooyman@houston.oilfield.slb.com
AF: Schlumberger Data and Consulting Services, 1325 South Dairy Ashford Road, Houston, TX 77077 United States
AU: Jones, E
EM: ejones@chevrontexaco.com
AF: Chevron Corporation, 2811 Hayes Road, Houston, TX 77082 United States
AB: Pre- and post-drill wellbore stability models for sediments containing gas hydrates were constructed for wells drilled in Atwater Valley and Keathley Canyon, Gulf of Mexico. The wells were drilled in April and May of 2005 under the auspices of the Joint Industry Project on Hydrates co-sponsored by industry and the U.S. Department of Energy. Wellbore stability was evaluated using a semi-analytical 2D elastoplastic model and borehole temperatures were simulated to ensure that conditions for hydrate dissociation would not occur during drilling. Since very little offset well data was available, predrill models were constructed using pseudo-well logs derived from seismic data. In order to estimate the properties required by these models, methods for deriving mechanical and thermal properties from seismic data were developed. These methods were based partly upon the results of mechanical tests conducted on THF hydrates by the Georgia Institute of Technology. Ocean current velocities in the Gulf of Mexico were also synthesized for temperature modeling. Before constructing pre-drill models for Atwater Valley and Keathley Canyon, the procedures outlined above were validated by comparing model predictions with observations from wells drilled in sediments containing hydrates during the ODP Leg 204 expedition to offshore Oregon. Good agreement was found between the predicted and modeled borehole breakouts. Models were then built for Atwater Valley and Keathley Canyon. The results of these models were used to formulate guidelines for managing downhole temperatures, borehole stability, and overpressured zones. Borehole logs and temperature surveys acquired during and subsequent to drilling were used to update the predrill predictions. Pre-drill mechanical failure models were found to be reasonably accurate, however boreholes were somewhat cooler than expected due possibly to uncertainties in predrill ocean current velocity estimates.
DE: 3004 Gas and hydrate systems
DE: 3022 Marine sediments: processes and transport
DE: 3902 Creep and deformation
DE: 5120 Plasticity, diffusion, and creep
DE: 5134 Thermal properties
SC: Ocean Sciences [OS]
MN: Fall Meeting 2005