Tight oil, also known as shale oil or light tight oil (LTO), is petroleum which is trapped in low permeability rocks; often shale or tight sandstone/ carbonates (even when not with the shale source rock it is usually very closely associated with). The fundamental difference between this unconventional oil and conventional oil, is that it is trapped in the rock formation itself, rather than being contained within a permeable rock formation by an overlying layer of impermeable rock. Tight oil usually requires similar extraction techniques to shale gas; the drilling of long horizontal laterals, massive hydraulic fracturing, and most importantly, the drilling of a densely spaced patterns of wells (up to 8 per square mile). It is therefore included within what is colloquially known as fracking.
Tight oil possesses almost all the negative impacts of shale gas extraction plus a few unique ones. Generic fracking impacts include water contamination, air pollution, industrialisation of the countryside and the production of massive amounts of toxic and radioactive fracking waste. Unlike shale gas where pipelines are build to move the product, the possibility of moving the oil in road and rail tankers leads to an additional level of chaos. The development of the Bakken Shale in North Dakota, in an area where there are few pipelines (as is the case in the UK), has lead to a massive proliferation of highly explosive loads on “bomb trains”.
Half a million tanker cars per year of crude oil have flooded onto railways in North America, a large part of which are driven by the production of Bakken Shale oil. The results have been devastating with numerous train derailments resulting in spills and explosions. The worst disaster so far occurred in the Canadian town of Lac-Megantic, Quebec when a Bakken Shale oil train derailed and exploded, laying waste to the centre of the town and killing 47 people (as well as leaving more lingering toxic effects). The US Department of Transportation is projecting 14 tanker train derailments per year, over the next few years.
In Britain, the main area threatened with tight (shale) oil extraction is the Weald Basin in South East England. The area around the small conventional Formby Oil Field to the north of Liverpool has also been mentioned as a possibility. The first tight oil exploration well in Britain was the Balcombe well drilled by Cuadrilla Resources over the Summer of 2013, in the face of massive community opposition. While Cuadrilla appear to have refocused their efforts on shale gas extraction in Lancashire, other players have emerged in the Weald. A plan by Celtique Energy to drill wells at Wisborough Green and Fernhurst in West Sussex, has at least temporarily foundered in the face of mass community opposition.
More recently a well drilled by UK Oil and Gas Investments (UKOG) at Horse Hill in Surrey, resulted in claims that there are billions of barrels of oil in the Kimmeridge Clay shale formation. Only a small fraction of this could possibly be extracted, but even for a typical recovery of around 5 percent, this would require the drilling of thousands of wells across the region. UKOG has been threatening to return to continue testing at Horse Hill, but has yet to announce any details. A well planned by Europa Oil & Gas near Leith Hill in Surrey would also target the Kimmeridge Clay and has been described as a tight oil ‘proof of concept’ by UKOG.
In the US, the main regions where tight oil extraction is happening are the Bakken Shale in North Dakota (9,000 wells drilled), the Eagle Ford Shale in South Texas (10,000 wells drilled) and the Permian Basin (Wolfcamp/Sprayberry, etc.), also in Texas. While in Canada thousands of wells have also been drilled into the Bakken, Cardium and Viking formations in Saskatchewan and Alberta. As with shale gas, there is general push to expand exploitation of tight (shale) oil beyond North America. Globally, particularly threatened areas include the Bazhenov Formation of West Siberia in Russia, and the Vaca Muerta formation in Argentina, as well as areas in Europe.