HR: 13:45h
AN: NS13A-02    [Abstracts]
TI: Shallow Water Flow in the Deepwater Gulf of Mexico: 20-Year Overview of a Near-Surface Geologic Hazard
AU: * Smith, M A
EM: michael.smith@mms.gov
AF: Minerals Management Service, 1201 Elmwood Park Blvd., MS 5222, New Orleans, LA 70123-2394 United States
AU: Ahmed, A
EM: adnan.ahmed@mms.gov
AF: Minerals Management Service, 1201 Elmwood Park Blvd., MS 5222, New Orleans, LA 70123-2394 United States
AB: Since 1984, shallow water flow occurrences have been reported in about 100 Gulf of Mexico lease blocks covering 80 oil and gas fields or lease blocks. These sands were deposited as continental slope/fan sequences during upper Pleistocene progradation. They include prodelta debris flows with a chaotic seismic character and, in some cases, rotated slump blocks. High sedimentation rates and an impermeable mud or clay seal from a condensed section are critical factors contributing to overpressures in shallow water flow sands. With a few exceptions, water flow incidents occur at water depths exceeding 1500 ft with a mean value at about 3800 ft of water. Water flow problem sands typically occur from 750 to 2000 ft below the seafloor. In the Mississippi Canyon and southern Viosca Knoll area, some of the shallower channel sands can be identified as part of a particular distributary system such as the old Timbalier channel, Southwest Pass canyon, or Einstein levee/channel system. Integration of high-resolution multichannel and reprocessed conventional 2D and 3D seismic data for the top-hole section is widely used to identify sand bodies with moderate or high shallow water flow potential. With the development of new geophysical technology and a better understanding of the controlling geological factors, instances of shallow water flow in recent years have been less severe and mitigating approaches to this geologic hazard have been successful in most cases.
DE: 3025 Marine seismics (0935)
DE: 5100 PHYSICAL PROPERTIES OF ROCKS
SC: Near-Surface Geophysics [NS]
MN: 2005 Joint Assembly