Abstract

Assessment of slope stability and seabed risk using individual disciplines can produce uncertain results because of generic solutions. The integration of disciplines allows a more robust solution and increases confidence in the prediction of long-term risk levels ahead of detailed field design. The Baobab field lies on the continental slope offshore Côte d'Ivoire, West Africa, where a preliminary field layout within a complex canyon system led to considerable concern about the long-term integrity of the development. A coring programme was planned to establish the timing of slope failure and activity at the seafloor. Biostratigraphic and sedimentological analyses of the late Pleistocene and Holocene section added high value to the assessment of the stability of the slopes under the modern regime. They were particularly useful in assessing the influence of the present-day bottom currents in terms of risk due to erosion and redeposition of seabed sediments.

1. Introduction

The exploration of deepwater canyon systems for hydrocarbons presents short- and long-term concern for drilling and stability of seabed infrastructure. There is a general perception that canyons are, by their nature, unstable and therefore represent a risk to seabed infrastructure. However, understanding the broader geological evolution and modern sedimentary regime facilitates management of this risk by determining what processes are acting on the slope that may contribute to slope instability. It suggested that the angle of slope where failure was more likely was significantly less than the present-day situation. The canyon walls sustain slopes of more than 30°, therefore a different approach was applied to the problem - biostratigraphy. Biostratigraphic studies can support slope stability assessments and provide a means to assess presentday activity and risk, not just historic seabed activity. They enable the assessment of the present-day sedimentary regime and determination of the amount and source of redeposited sediments.

This content is only available via PDF.
You can access this article if you purchase or spend a download.