The Fall, Rise, & Fall of an Ocean Rig's Marine Community

Approximately 28% of global gas and 37% of global oil production comes from rigs operating offshore.  Each rig is created on land, brought out to the ocean, sometimes in pieces, and put in place where they will extract as much hydrocarbon from the Earth as possible.   From birth until death, a rig becomes inextricably tied to the ocean in which it lives – for better and for worse.

A rig’s ocean life gets into full swing once it arrives at its destination – the reserve that that it will tap. One of the important jobs a rig has is to stay in place.  There are a number of different strategies to do this, but the vast majority of rigs achieve this by being attached to the sea floor.   Even floating platforms typically employ anchoring systems to help keep them in place.  Some rigs are accompanied with cables and pipes linking wells together, and some even with their own pipelines to export the precious commodity back to land.  Contact with the bottom inevitably impacts the animals that live on and within the seabed.  Animals and plants may be trapped under or crushed by the weight of structures, cables, anchors, and pipelines that lay across the seafloor, whilst sediment plumes smothering, suffocating, and damaging other animals and plants living nearby.  The noise generated may disturb and harm marine mammals – and potentially fishes and invertebrates.  To what extent this is a problem is an area of ongoing research.

Once drilling starts, life remaining around the site has a new suite of problems to deal with.  Drill cuttings – essentially fragments of rock from the sea floor – are pushed onto the surface around the well.  Accompanying these cuttings is drill mud – typically a mixture of seawater and chemicals designed for a range of different functions, like keeping the drill cool and clean, and providing hydrostatic pressure.  As the drilling continues, this combined toxic debris forms ‘cutting piles’ which can expand hundreds of meters out from the well being created.  Eventually the well is capped with a blowout preventer and riser, and any subsequent debris processed and released nearer the surface of the sea. 

This article was written for (and can be read in full in) The Marine Professional - a publication of the Institute of Marine Engineering, Science & Technology (IMarEST)