HR: 0830h
AN: T41D-0259    [PDF]
TI: Impact of tectonic stresses on compaction in the toe thrust region of a Tertiary Delta
AU: * Fitts, T G
EM: tina.g.fitts@exxonmobil.com
AF: ExxonMobil Upstream Research Company, 3120 Buffalo Speedway, Houston, TX 77252-3189 United States
AU: Welton, J
EM: joann.welton@exxonmobil.com
AF: ExxonMobil Upstream Research Company, 3120 Buffalo Speedway, Houston, TX 77252-3189 United States
AU: DeGraff, J M
EM: james.mdegraff@exxonmobil
AF: ExxonMobil Exploration Company, P.O.Box 4778, Houston, TX 77210-4778 United States
AB: Increased mean and shear stresses during toe-thrusting can accelerate compaction within thrust sheets, even away from bounding faults. Tectonic compaction in the toe-thrust regime is inferred when thrusted sediments appear to be anomalously consolidated compared to the same materials sampled from undeformed sections. Elevated mean stresses within thrust sheets can be estimated from the degree of overconsolidation of thrusted sediments relative to those compacted in near-uniaxial and neutral tectonic settings. Core data (sands) and well logs (shales) along a set of toe-thrusts of a Tertiary Delta have been used to describe the mechanism for compaction and estimate the magnitude of deviation from the normal trend in undeformed areas. Compaction mechanisms within thrust sheets appear to be dominated by grain rearrangement rather than cataclasis, which appears to occur only locally in thrust fault zones based on core data. Estimates of horizontal/vertical stress ratios ($<$1.5) compare favorably with estimates based on the low thrust angle and mechanical rock property ranges assuming relatively weak rocks in this shale-prone section. Results based on physical properties provide a narrower stress range than would be derived from the potential range of mechanical properties and structure inputs alone.
DE: 3000 MARINE GEOLOGY AND GEOPHYSICS
DE: 3022 Marine sediments--processes and transport
DE: 3675 Sedimentary petrology
DE: 5114 Permeability and porosity
DE: 8020 Mechanics
SC: Tectonophysics [T]
MN: 2003 Fall Meeting