HR: 1330h
AN: G43A-05    [Abstracts]
TI: The Role of Hydrocarbon Production on Subsidence and Fault Slip in the Louisiana Coastal Zone
AU: Chan, A W
EM: Alvin.W.Chan@shell.com
AF: Department of Geophysics, Stanford University, Stanford, CA 94305 United States
AU: Chan, A W
EM: Alvin.W.Chan@shell.com
AF: Shell International Exploration & Production Inc., P.O.Box 481, Houston, TX 77001-0481 United States
AU: * Mallman, E P
EM: emallman@pangea.stanford.edu
AF: Department of Geophysics, Stanford University, Stanford, CA 94305 United States
AU: Zoback, M D
EM: zoback@pangea.stanford.edu
AF: Department of Geophysics, Stanford University, Stanford, CA 94305 United States
AB: Pore pressure reductions and the associated stress changes due to subsurface hydrocarbon production can lead to reservoir compaction and fault reactivation. These deformations may result in a significant vertical elevation drop on the land surface. When elevation change occurs in a sensitive environment, such as a coastal wetland, the impact of hydrocarbon production cannot be ignored. Using a simple analytical solution and a numerical model, the impact of reservoir compaction and fault slip on surface subsidence is investigated. The Lapeyrouse field in southern Louisiana is chosen as the study site due to its relatively complete pressure data and structural maps. A releveling survey, showing elevation changes for a 30-year period transects the field, is used as a quantitative comparison between the model predictions and observed subsidence. Despite using stress and rock mechanics data from offshore oil fields to compensate for the absence of such data in Lapeyrouse, the degree and extent of subsidence estimated from the analytical method generally agrees with the order of magnitude of elevation drop measured from the releveling survey. Using different constitutive rheological laws to describe the producing sand formation changes the predicted magnitude of subsidence as expected. While the general trend and magnitude of subsidence predicted generally matches the observed there is one notable exception at the northern end of the releveling line adjacent to the Golden Meadow Fault. Numerical models allow for investigation of the impact of compaction-induced slip along the Golden Meadow Fault, located north of the Lapeyrouse field, on surface subsidence. When incorporating the Golden Meadow Fault, the subsidence pattern changes when the fault is allowed to slip freely as a response to deformation associated with reservoir compaction. The magnitude and location of slip along the Golden Meadow Fault are estimated due to reservoir compaction in the Lapeyrouse field. Subsidence predicted through analytical and numerical methods in this study do not take into account contributions of natural subsidence and other human activities, however, the magnitude of induced subsidence and fault slip suggest that hydrocarbon production can have an impact on land subsidence on a local scale. We suggest that production-induced land subsidence is one of the many mechanisms that should not be ignored when evaluating subsidence and land loss in the Louisiana Coastal Zone.
DE: 1200 GEODESY AND GRAVITY
DE: 1208 Crustal movements--intraplate (8110)
DE: 1299 General or miscellaneous
DE: 8164 Stresses--crust and lithosphere
SC: Geodesy [G]
MN: 2005 Joint Assembly