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SEISMIC PREDICTION AND OPERATIONAL RESULTS FOR GULF OF MEXICO WELLS IN Previous HitGASNext Hit-HYDRATE AREAS

Michael A. Smith*, William Kou, Adnan Ahmed, and Robert Kuzela
*Minerals Management Service, New Orleans, LA

Although more than 500 exploration wells have been drilled through the zone of hydrate stability in the deepwater Gulf of Mexico, Previous HitgasNext Hit hydrate has not been documented as a serious drilling hazard. Seafloor hydrate mounds associated with active Previous HitgasNext Hit vents are commonly found at the edges of minibasins and, like chemosynthetic communities, are avoided during drilling operations. There is considerably less available information on the distribution, concentration, reservoir properties, and stability of subsurface hydrate. Acquisition parameters and survey design of 3D exploration seismic are not optimized for shallow sediments and do not allow accurate characterization of naturally occurring hydrate. At some Gulf of Mexico locations, a bottom-simulating reflector (BSR) may indicate the base of the hydrate stability zone. As geohazard assessment geophysicists become more aware of the potential of Previous HitgasNext Hit hydrate to cause seafloor or wellbore instability, detailed delineation of Previous HitgasNext Hit-hydrate zones and their relationship to free Previous HitgasNext Hit pockets will become more common.

Our understanding of Previous HitgasNext Hit-hydrate settings is further limited because the shallow section is drilled riserless as a large diameter hole with returns deposited on the seafloor. This drilling methodology makes it impossible to acquire samples of hydrated sediment and only a few Measurement While Drilling log curves are obtained. MMS and seven major oil and service companies in the Department of Energy Gulf of Mexico Previous HitGasNext Hit Previous HitHydratesNext Hit Joint Industry Project (JIP) have developed protocols, models, and laboratory tests designed to improve seismic imaging of Previous HitgasNext Hit hydrate zones. The JIP has selected locations near sampled seafloor hydrate mounds in the Atwater and Keathley Canyon areas for drilling, logging, and coring several 1,000- to 2,000-ft deep stratigraphic test wells through the hydrate deposits in Spring 2005. These wells will allow the first real calibration of geophysical data for characterizing buried Previous HitgasNext Hit Previous HithydratesTop and will provide critical data on the impact of hydrate drilling and production on seafloor stability.