East Midlands Seismic Survey

We have launched a three dimensional (3D) seismic survey as part of our plans to develop the nation’s shale gas resources across a 250km2 area of the East Midlands. The data from this extensive survey will provide a clear image of the underground rock structure and assist us in determining our future drilling activities.

Starting in June 2017, the data acquisition phase will take about six months for the whole 250 km2 area, starting in the north west of the survey area near Harthill and finishing in the south east near Kings Clipstone.

How it works

For 3D acquisition, data is acquired from a grid or ‘patch’ of survey lines covering a specific area of land. This provides a multi directional image beneath the surface.

A controlled seismic source, positioned on or near surface, is used to generate a reflection signal which passes through the various underground rocks. At changes in rock type and density, part of this signal is reflected back to surface where a series of microphones (geophones) receive its return. By recording this ‘two way’ time, the depth, extent and characteristics of rocks can be determined and imaged.

Pegging out

Ahead of the data acquisition, surveyors accompanied by an ecologist and an agricultural liaison officer walk the survey area to determine the precise placement of receivers and energy sources. Walking the land gives us an accurate record of the condition of the land to ensure it is restored appropriately once operations are finished. It also identifies stand-off distances from buildings, buried utilities, hedges, trees, nesting birds, environmental and other restrictions, and determines whether the energy source at each location should be created by a group of up to three vibroseis machines (each about the size of a bin lorry) or in a small number of cases, by setting off a small charge buried up to ten metres below ground.

"Geophones" commonly called receivers

These passive listening devices are placed in fields and road verges. Between placement and recovery of the receiver, the only likely activity will be a technician changing the battery.

Vibroseis Trucks

These vehicles will usually operate in groups of three and will be the most obvious sign of a survey taking place as some surveying is done on roads. There are likely to be some short term localised traffic delays as the survey progresses through an area.

Shot hole drilling

In some circumstances, a small charge is used to generate the signal. A tractor mounted drill is used to drill a narrow hole approximately 10 cm in diameter and about 10 m in depth. The charge (source) is placed at the bottom of the hole and the hole is back filled with earth. When the charge is detonated, a dull thud can sometimes be heard. in close proximity to the source point. The shot cord and other equipment is removed from the shot hole after detonation and the hole is backfilled and restored. The charge used will not damage the soil or groundwater and shot holes will not be drilled where drinking water supplies are present (groundwater protection zones).

Info on the East Midlands Seismic Survey

A5-pp6-East Midlands Booklet-WEB-07JUNE.PDF