Date of Award
Program or Major
Doctor of Philosophy
Larry A Mayer
The location and distribution of near-surface gas in continental margins is of particular interest for oil exploration and development programs. The presence of gas seepages can be evidence of the possible existence of subsurface hydrocarbon reservoirs. Gas is also a potential hazard for offshore facilities, as it decreases the strength of unconsolidated sediments increasing the risk of seafloor failures and slumps.
Acoustic remote sensing systems such as multibeam and sidescan sonars can be used for mapping and detection of near-surface gas in marine sediments. These systems provide a realistic depiction of the seafloor by means of the simultaneous acquisition of co-registered high-resolution bathymetry and calibrated seafloor backscatter. The recognition of gas signatures in acoustic remote sensing data depends on the proper modeling of the acoustic backscatter response. In this thesis, a high frequency backscatter model that takes into account the amount of free gas in the sediments is proposed. Inversion of this model is used to estimate the distribution of near-surface gas in the sedimentary basin Additionally, analysis of backscatter images and detailed bathymetry reveals anomalous seafloor features, which are associated with gas expulsion.
The acoustic remote sensing data is analyzed in conjunction with other layers of information available in the exploration region, including a core database, structural maps, location of wells, geochemical data and geophysical data. This analysis attempts to link anomalous acoustic backscatter on the seafloor to sub-surface structures, a necessary step toward the understanding of the stratigraphic or tectonic control of seafloor seepages. New visualization techniques, which take advantage of 3D tools and GIS integration, are used to help analyze and understand these complex relationships in a natural and intuitive manner.
Fonseca, Luciano Emidio Neves da., "A model for backscattering angular response of gassy sediments: Applications to petroleum exploration and development programs" (2001). Doctoral Dissertations. 52.