Impact of drilling activities in warm sea: seabed re-colonization

Abstract

From the Abstract: “Since the onset of offshore drilling, the drill cuttings and their disposal have received much attention in the oil and gas industry. Numerous studies performed in the laboratory on the foreseeable fate of cuttings have led to the search for new formulations with the objective of achieving lower toxicity and better intrinsic biodegradability.

The study of the marine environmental impact associated with the discharge of OBM (oil base muds) drill cuttings has already given rise to numerous works and surveys related to the North Sea, but it is clear that knowledge is still limited. Further information is required on the monitoring of sediments polluted with OBM cuttings, especially in warm sea conditions.

On this topic, a research project was conducted in 2002 and 2003 in Congo (Africa) in order to study the modes of regeneration of the benthic fauna and the recolonization of the seabed after the discharge of OBM cuttings. Previous sampling and analyses were performed in 1995 (after the first step of drilling) and 2000 (one year and a half after the stop of cuttings discharge). In 2002, a systematic study of the abundance and diversity of the benthic fauna was conducted. In addition, a methodology based on classical physical chemical analyses on sediment, tests of toxicity, biodegradability and lixiviation was applied, in order to explain the evolution of the recolonization by the benthic fauna (SPE 77471). In the more general context of the environmental constraints of oil industry, our work demonstrated the containment of the impacted zones, the absence of significant risks of modification of the adjacent ecosystems and the possible application to other discharge sites.

We present here the results related to the last phase of sampling carried out in 2003. It is noteworthy that the whole results confirm the main evolutions observed in the previous survey.”