Geophysical and Geotechnical Investigations of the Sea Floor Sediments for Offshore Subsea Facility Installation in “EMOBS” Oil Fields, Western Niger Delta Nigeria

Abstract

The investigation reveals the stratigraphic sub-division of the site within the depth explored. Basically, though at some depths the lithology is similar, they are different sediments as revealed by the laboratory tests. Essentially, the site consists of silty clay on the surface that is soft in consistency and weak in shear strength. However, the consistency and the strength of the clay improve down depth from 14.50m where it becomes soft-firm. At 30.00 m depth, the clay becomes very firm as some shell fragments (mostly calcareous shells of gastropods and mollusks) occurred within it. Below this clay unit at about 45.00 m depth, a dense to very dense Sand unit of about 10.00m -12.00m thick occurs. The sand is poorly to moderately graded.  Below this sand unit at about 57.0m depth, another firm clay unit occurs. This clay unit becomes intercalated with sand at 60.50m and continues to about 62.50m where it grades into firm clay and continues to the termination depth at 66.00m. Based on the findings, a number of recommendations have been formulated for the safe and cost effective development of this Oil Field.