Cuadrilla is currently exploring the Bowland shale rock in Lancashire for natural gas. The gas trapped within this rock is no different to the natural gas which we all use every day in our homes, businesses and communities.
Hydraulic fracturing – or fracking as it is sometimes called – is the long established process of creating fractures in rock formations to release the natural gas trapped inside. Hydraulic fracking has been taking place safely in the UK for decades both onshore and offshore, mostly in different kinds of rock formations rather than shale rock. Regardless of the kind of rock however, the actual hydraulic fracking process is the same. Our site in Elswick in Lancashire was fractured in 1993 and generated around 1MW of electricity seven days a week in its early life. Hydraulic fracturing is common in the North Sea, where it has been performed thousands of times.
How does Hydraulic Fracturing Work?
Fracturing takes place in a series of stages along the length of a well. Each stage is between 15m and 50m in length with the first stage located at the end of the well. Successive fracturing stages are pumped working along the horizontal well from its end to its beginning. The tiny fractures in the shale rock are caused by pumping a mixture of water, sand and a chemical called polyacrylamide, under high pressure, from the horizontal well into the surrounding shale rock.
Polyacrylamide is assessed by the Environment Agency as non-hazardous to groundwater and is used to reduce friction as the water passes through the wellbore, and forms just 0.05% of the frack fluid. It is a commonly used chemical in the UK, for example in garden products, water treatment and contact lenses. Learn more about how the Environment Agency regulates us here.
Once the gas is released in the tiny fractures, held open by the grains of sand, the gas travels up the well to surface. When the hydraulic fracturing is completed the flow rate of natural gas produced from each well is tested over period of approximately six months.
Our comprehensive environmental monitoring of our Preston New Road site is ongoing, and you can continue to keep up to date with the latest data via our ePortal, this will also include daily seismicity monitoring during hydraulic fracturing operations. You can view the ePortal here.
The mineralogy of the Lancashire Bowland shale has been analysed in detail using X-ray diffraction of shale core samples and cuttings taken from the Preese Hall well. This analysis has confirmed that both the Upper and Lower Bowland shales are very well suited to hydraulic fracturing as they are formed from a highly siliceous matrix with consistently low overall clay content and not reactive clays.
How much gas will the wells produce?
The purpose of exploration is to establish exactly how much gas a well could produce. Cuadrilla retained Anderson Thompson, a team of reservoir engineers, geoscientists and hydraulic fracturing specialists, to undertake analytical research on likely gas recovery volumes from horizontal wells to be drilled in the Lancashire Bowland shale. Anderson Thompson has broad international basin experience and specialist knowledge of the Permian, Eagle Ford, Bakken, Marcellus and Montney shale plays in North America.
Using input data from the Lancashire Bowland exploration wells that Cuadrilla has drilled to date, including the Preese Hall well, which was hydraulically fractured and flow tested in 2011, Anderson Thompson modelled potential gas recoveries from a 2.5km horizontal well. The results of this modelling forecast that, over a 30 year period, a most likely volume of 6.5 billion cubic feet (Bcf) of gas would be produced from a 2.5km horizontal Bowland shale well.
Expected Gas Production For a 2.5km Horizontal Well Over a 30 Year Period