HR: 0800h
AN: G11A-1202    [Abstracts]
TI: Modeling Surface Subsidence from Hydrocarbon Production and Induced Fault Slip in the Louisiana Coastal Zone
AU: * Mallman, E P
EM: emallman@pangea.stanford.edu
AF: Stanford University, Department of Geophysics 397 Panama Mall, Stanford, CA 94305 United States
AU: Zoback, M D
EM: zoback@pangea.stanford.edu
AF: Stanford University, Department of Geophysics 397 Panama Mall, Stanford, CA 94305 United States
AB: Coastal wetland loss in southern Louisiana poses a great threat to the ecological and economic stability of the region. In the region of interest, wetland loss is a combination of land subsidence along with eustatic sea level rise, sediment accumulation, erosion, filling and drainage. More than half of the land loss in coastal Louisiana between 1932 and 1990 was related to subsidence due to the complicated interaction of multiple natural and anthropogenic processes, including compaction of Holocene sediments in the Mississippi River delta, lithospheric flexure as a response to sediment loading, and natural episodic movement along regional growth faults. In addition to these mechanisms, it has recently been suggested that subsurface oil and gas production may be a large contributing factor to surface subsidence in the Louisiana Coastal Zone. We model the effect of fluid withdrawal from oil and gas fields in the Barataria Bay region of the Louisiana Coastal Zone on surface subsidence and its potential role in inducing fault slip on the region's growth faults. Along the western edge of Barataria Basin is a first-order leveling line to constrain our model of land subsidence. The rates for this leveling line show numerous locations of increased subsidence rate over the surrounding area, which tend to be located over the large oil and gas fields in the region. However, also located in the regions of high subsidence rate and oil and gas fields are the regional normal faults. Slip on these growth faults is important in two contexts: Regional subsidence would be expected along these faults as a natural consequence of naturally-occurring slip over time. In addition, slip along the faults can be exacerbated by production such that surface subsidence would be localized near the oil and gas fields. Using pressure data from wells in the Valentine, Golden Meadow, and Leeville oil and gas fields we estimate the amount of compaction of the various reservoirs, the resulting surface subsidence, and the potential for induced fault slip. The estimated subsidence related to reservoir compaction and inªduced fault slip can then be combined with subsidence related to natural compaction of Holocene sediments, lithoªspheric flexure, and eustatic sea level rise to produce a spatially variable, comprehensive model of land subsidence in the Barataria Bay region of the Louisiana Coastal Zone.
DE: 1211 Non-tectonic deformation
DE: 1299 General or miscellaneous (1709)
SC: Geodesy [G]
MN: Fall Meeting 2005