Top right of the picture is a sand screen. In the pit are cuttings and spent drilling fluids from a very long way down in the earth. The thick mud was spread to land safely and in an entirely environmentally friendly way supervised by the Environment Agency.
What comes out of the hole is, hopefully, mostly gas. Before that happens, and indeed for the life of the well, lots of other things come out. Much of the other stuff is probably not environmentally unfriendly.
Firstly, the shaft will be bored through a range of strata, some of which may contain elements or compounds which might be toxic in some way. The drilling fluids which are used to carry the drill cuttings out of the well as it is bored (the “flowback”), will also bring out these other materials – if they are there. Secondly, the high pressure water used in volume to create the hydraulic fracturing will also dissolve materials from the shale, especially Sodium chloride – common salt. Anyone who dismisses these potential dangers is, at best, irresponsible, and at worst, criminal.
There are two possible approaches to dealing with these “arisings” out of the well. Firstly, it is important to note that in the UK (and indeed all of the EU) these arisings are legally a Controlled Waste and that means subject to regulation – of which there is plenty and the Environment Agency knows that they will be watched every step of the way by a lot of aggressive people (some emotional, not very well informed and motivated by overseas interests).
The first way of dealing with the arisings is to isolate them in a restricted area. That could be in a lagoon or enclosed space and left there forever. In such a case, IF there is any risk, it is called a “point risk” and is always at its maximum. Alternatively, the cuttings could be used in, say, the construction of sea wall and flood defence work. It is likely that our regulators will favour this route because it is relatively easy for those drafting the regulations to identify the risks and write the regulations to contain the risks – even if it means permanently. The disadvantage of this route, hover, is that if there is a concentration of a material which might be toxic, it is still there as a “point risk”.
The second way is to remember that nature is remarkably resilient and, given time and enough spreading out, will deal with almost anything and to its sustainable advantage. This known as a “dispersed risk”. The route is likely to be favoured by environmental scientists with the right training and experience because it provides for the identification, management and the sustainable elimination of the risks by creating an environmental benefit. There advantage of this route is that if (again “if”) there is a concentration of a material which might be toxic, then a “dispersed risk” can be identified and managed by competent people and processed out of existence.
This area of discussion will be very interesting to watch. It revolves around whether the arisings are seen as “wastes” (a word with negative implications) or a “resource” (a word which implies benefit and sustainability) i.e. not to be lightly lost or left un-used.
The Sunday shale gas blog from Bill Butterworth 30 February 2016