4 - Subsea Surveying, Positioning, and Foundation

Abstract

This chapter provides minimal functional and technical requirements for the subsea soil issue. The subsea survey is described as a technique that uses science to accurately determine the terrestrial or 3D space position of points and the distances and angles between them in the seabed area for subsea field development. Geophysical and geotechnical surveys are conducted to evaluate seabed and subsurface conditions in order to identify potential geological constraints for a particular project. The base survey covers the whole subsea field development, which includes the infield pipelines, mobile offshore drilling unit (MODU) footprints, pipeline end manifolds (PLEMs), manifolds, Christmas tree, umbilicals, etc. As part of the planned field development, a detailed geophysical and geotechnical field development survey and a soil investigation based on the survey results are to be performed. The purpose of the survey is to identify potential man-made hazards, natural hazards, and engineering constraints when selecting a subsea field area and also flowline construction; to assess the potential impact on biological communities; and to determine the seabed and sub-bottom conditions.