Use of ROVs for Deepwater-Biodiversity Assessment: Case Study, Offshore Nigeria
Authors: Denney Dennis 
Published: February 2015

This article, written by Senior Technology Editor Dennis Denney, contains highlights of paper SPE 146439, ’Using Industrial Remotely Operated Vehicles in Standby Time for Deepwater-Biodiversity Assessment: A Case Study Offshore Nigeria,’ by Daniel Jones, National Oceanography Centre; Charles Mrabure, SPE, Total E&P Nigeria; and Andrew Gates, National Oceanography Centre, prepared for the 2011 SPE Annual Technical Conference and Exhibition, Denver, 30 October-2 November. The paper has not been peer reviewed.

Very limited information is available on the deepwater biodiversity offshore Nigeria. Detailed information on seabed communities is vital for effective environmental management of offshore-drilling disturbance, but collection of environmental data usually requires a dedicated research vessel with associated high costs. An environmental-survey approach was developed that used remotely operated vehicles (ROVs) already in place on survey/supply boats during standby time in drilling operations for low-cost and high-quality operations.

Introduction

There is little information on the mega-benthic communities of the waters in the region of the Gulf of Guinea. Most studies focused on the Canary region to the north. The Benguela region to the south of the Gulf of Guinea also has received some attention, particularly on the shelf, slope, and the abyss. The Gulf of Guinea region is heavily exploited for natural resources, primarily hydrocarbon resources and fish, and is subject to high levels of anthropogenic effect from pollution. The environmental information is collected mostly by oil and gas companies and is not available in scientific literature. Baseline quantitative environmental information is needed for successful management of this increasingly exploited ecosystem.

Typically, environmental-assessment surveys do not quantify the larger epibenthic megafauna, which are important in benthic processes. Megafauna have a valuable role in the ecosystem, particularly in dispersing and redistributing organic matter and sediment, which may be important in the recovery of benthic systems from disturbance. Deep-sea megabenthic ecology traditionally has relied on semiquantitative sampling with trawls and sledges; more-recent advances used imaging methods to obtain quantitative data. Imaging studies enable a nondestructive fine-scale survey of megabenthic abundance, diversity, and distribution and can have a much larger spatial coverage than is possible with conventional macro faunal sampling. Recent advances and application of detailed navigation technology for deep-sea studies, coupled with increasing availability of high-resolution spatially accurate acoustic data on submarine topography and sediment properties, allow the first attempts at linking fine-scale patterns in biology to the broad-scale patterns in habitat type and subsea landscape. Given the sheer size and difficulties of accessing the deep-sea environment, accurate extrapolation of the fine-scale observations with information on the important physical controls for distribution is vital to describe the important broad-scale patterns in benthic biology.