Our response to the Channel 4 segment on gas extraction in the Netherlands
13 November 2018
Responding to the Channel 4 news segment on Monday 12th November, a spokesperson from UK Onshore Oil and Gas (UKOOG) said:
"UK research authorities have consistently warned about extrapolating experiences from other countries and applying them to the UK, where the geology and regulatory system is completely different. Unfortunately, on Monday Channel 4 made a number of inaccurate comparisons between shale gas operations in Lancashire and onshore production in the Netherlands, and these now must be cleared up as a matter of public record.
"Firstly, the geology. The Groningen gasfield lies in a in a highly porous (15 to 20%) 300m layer of sandstone. When the gas is extracted, the sandstone compresses (because of the high porosity). Compaction on its own does not result in seismicity, however. The Groningen field is affected by numerous faults and these faults can lead to strong local variations in compaction. If material on one side of a fault compacts more than the other side, shear stresses on the fault build up and at some stage the strength of material at the fault (a zone of weakness) is overcome after which an earthquake can occur.
"UK shale geology is very different. In particular, the porosity is much lower - around 3-6 % (i.e. the holes in the rock are much smaller) and the rocks contain minimal amounts of clay making them highly suited for exploration. Both of these facts mitigate against subsidence and therefore this does not lead to the compaction seen in the Netherlands.
"Secondly, the regulation. The UK seismic traffic light system which operators must adhere to is set at an extremely low level, causing operators to pause when the top light is reached. This level is significantly lower than that imposed on other industries that are known to cause seismicity such as the geothermal, quarrying and construction sectors. The levels of seismicity currently being recorded in Lancashire are at many orders of magnitude below which would be ever felt at the surface and normally would not have been recorded, indeed, the highest recent event in Blackpool of 1.1ML is over 11,000 times weaker and 500 times smaller than the 3.8 quake that hit Grimsby in June, which itself caused no damage or injuries. The presence of large numbers of highly sensitive seismic meters at the site mean that seismic events below 1 are being recorded. There are many thousands of these tiny events estimated to occur in the UK every year."
“UK research authorities have consistently warned about extrapolating experiences from other countries and applying them to the UK, where the geology and regulatory system is completely different. Unfortunately, on Monday Channel 4 made a number of inaccurate comparisons between shale gas operations in Lancashire and onshore production in the Netherlands, and these now must be cleared up as a matter of public record.
“Firstly, the geology. The Groningen gasfield lies in a in a highly porous (15 to 20%) 300m layer of sandstone. When the gas is extracted, the sandstone compresses (because of the high porosity). Compaction on its own does not result in seismicity, however. The Groningen field is affected by numerous faults and these faults can lead to strong local variations in compaction. If material on one side of a fault compacts more than the other side, shear stresses on the fault build up and at some stage the strength of material at the fault (a zone of weakness) is overcome after which an earthquake can occur.
“UK shale geology is very different. In particular, the porosity is much lower - around 3-6 % (i.e. the holes in the rock are much smaller) and the rocks contain minimal amounts of clay making them highly suited for exploration. Both of these facts mitigate against subsidence and therefore this does not lead to the compaction seen in the Netherlands.
“Secondly, the regulation. The UK seismic traffic light system which operators must adhere to is set at an extremely low level, causing operators to pause when the top light is reached. This level is significantly lower than that imposed on other industries that are known to cause seismicity such as the geothermal, quarrying and construction sectors. The levels of seismicity currently being recorded in Lancashire are at many orders of magnitude below which would be ever felt at the surface and normally would not have been recorded, indeed, the highest recent event in Blackpool of 1.1ML is over 11,000 times weaker and 500 times smaller than the 3.8 quake that hit Grimsby in June, which itself caused no damage or injuries. The presence of large numbers of highly sensitive seismic meters at the site mean that seismic events below 1 are being recorded. There are many thousands of these tiny events estimated to occur in the UK every year.”
