Overview of Geological and Geotechnical Conditions of Northern Gulf of Mexico with Emphasis on the Clastic Shelf - An Offshore Wind Energy Development Perspective

Abstract

We present a geological and geotechnical assessment of the outer continental shelf (OCS) of northern Gulf of Mexico, relevant to prospective offshore wind energy developers for identifying geohazards and developing a reconnaissance level understanding of foundation zone geotechnical conditions. The information provided in this paper is considered helpful in designing appropriate geophysical and geotechnical site investigation campaigns, and in preliminary evaluations of suitability of various foundation concepts for offshore wind infrastructure during the planning stage of lease area development. The generalized assessment of site conditions was conducted using an integrated approach that involved review of various published geological and geomorphological studies on shallow sediment distribution and shallow stratigraphy along with relevant published geotechnical information and in-house experience with geotechnical conditions in Gulf of Mexico. Published geological maps showing distribution of seafloor sediments with different characteristics, as well as maps and digital data on geohazards and geomorphic features associated with various depositional or erosional processes have been evaluated. Relevant stratigraphic information was synthesized in relation to geotechnical characteristics of various soil layers encountered at geotechnical investigation locations. This process culminated in the development of a map showing distribution of potential geohazards in the study area, as well as a map illustrating various soil provinces which represent areas of likely similar geotechnical conditions within the foundation zone. In addition to a regional overview, special emphasis is placed in this paper on the geological and geotechnical assessment of site conditions for the clastic shelf portion of the northern Gulf of Mexico. The assessment revealed that the entire clastic shelf west and east of Mississippi Delta is favorable for offshore wind energy development. The shelf within the present-day Mississippi Delta appears as less favorable. Geotechnical assessment of foundation zone conditions within the clastic shelf of Northern Gulf of Mexico culminated into three soil provinces characterized by distinct generalized soil profiles displaying the variation in thickness of individual soil units within each soil province. Representative ranges of geotechnical parameters for each soil unit are also presented and discussed.