Lambda-Rho Processing - A tool to Reveal Full Hydrocarbon Potentials

Regional analysis of a 5,716 well log database from the Gulf of Mexico allows prediction of AVO response, as well as prediction of velocities useful to processing geophysicists. Regional trends are derived from depth profile plots of well sand / shale velocity histograms. Four major sub-regions were delineated, based on these profiles: 1.Lower and Middle Miocene Shelf, 2.Upper Miocene through Pleistocene Shelf, 3.Upper to Middle Slope, and 4.Lower Slope. Strong velocity inversion is common in the geopressured Miocene in the deep Lower and Middle Miocene Shelf region. The present deep water areas shows a slower velocity increase with depth throughout the lithologic section than is seen on the shelf above geopressure, but has a much narrower range in variation than is seen on overpressured rocks on the deep shelf. The Lower Slope appears to have a greater spread in sand and shale P-wave velocities than are seen in the Upper to Middle Slope areas. This analysis also allows prediction of the velocities which should be seen by the processing geophysicist. Some features of the velocity functions seen are those usually associated with multiple reflections, and as such, often discounted by the processor.