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Controls of Cenozoic Mass Transport Deposits on Hydrocarbon Prospectivity of the Mexican Ridges Fold-Belt, Western Gulf of Mexico

Abstract

The Mexican Ridges fold-belt (MRFB) of the western Gulf of Mexico (GOM) is a 600-km-long, deep-water, passive margin fold-belt along the continental margin of Mexico that formed by Miocene to Recent gravity-driven deformation and detaching at the top of shale-rich Paleogene mass transport deposits (MTDs). A 20,000 km grid of 2D depth-converted industry seismic data, tied to 3 wells, was used to map 8 MTD events of Paleogene age and 12 of Neogene age. In order to assess the impact of MTD’s on hydrocarbon migration and trapping, the Paleogene and Neogene MTD’s were classified based on: 1) lithofacies and mud vs. sand content from well data, 2) seismic facies, including upper and lower contacts, 3) syn-depositional structure, and 4) depositional environment. The main characteristics of Paleogene MTD’s include: areal extent of < 30,000-km², run-out lengths < 300-km, and < 1,400-m in thickness. Deposition of the regionally extensive Paleogene MTD events is interpreted to be a result of Paleogene tectonic activity and uplift along the adjacent Sierra Madre Oriental orogenic front known from previous thermochronological studies. In contrast, characteristics of Neogene MTDs include areal extents of < 100-km², lengths of < 20-km, and < 400-m thickness. The less extensive Neogene MTDs are interpreted as slides from over-steepened, thrust-cored fold structures during late Pliocene to Recent fold-belt development. Controls of Paleogene MTDs on hydrocarbon prospectivity include forming: 1) a strong, 100-1200-m-thick regional seal horizon for underlying Paleogene reservoirs, 2) a migration barrier to overlying Miocene reservoirs from Mesozoic sourced hydrocarbons, 3) a fluid-rich matrix that promotes overpressure that in turn controls the structural development of the overlying fold-belt. Hydrocarbon controls of Neogene MTDs include: 1) localized, mud-rich seal horizons, 2) traps where MTD’s overlap with fold-structures and Miocene channel-fan reservoirs, and 3) depositional extent of MTD events controlled by the structural development of the underlying fold-belt.