Testing has yielded good results; but the traffic light system is slowing the process down.
The Bowland Shale in the UK has lived up to expectations with the potential to be a significant source of gas, according to flow tests done so far. There is a rich reservoir of recoverable high quality natural gas present where UK explorer Cuadrilla has been working in the Preston New Road exploration site in Lancashire, it said February 6.
It had flow-tested the UK’s "first ever horizontal shale gas exploration well, drilled through the shale rock more than 7,500 feet" and said the results were excellent.
CEO Francis Egan said: “We have also confirmed that the Bowland shale formation fractures in a way that, from US experience, is typical of an excellent shale gas reservoir. A complex fracture network was generated in the shale and sand injected into the fractures has stayed in place during flow back. Also the natural gas flowing to surface from the shale has a very high methane content, which means it could be delivered into the local gas grid for the benefit of local consumers with minimal processing required.”
An intentionally conservative micro-seismic operating limit during hydraulic fracturing, set at just 0.5 on the Richter Scale, had however severely constrained the volume of sand that could be injected into the shale rock. There have been calls for the thresshold to be raised, with Ineos yesterday calling the system "unworkable".
Egan added that despite only partial testing and only a fraction of the intended sand injected, "the natural gas still flowed back from the shale at a peak rate of over 200,000 ft3/day and a stable rate of some 100,000 ft3/day."
Based on similar experience from the US, where the technology is advanced, Cuadrilla estimates that it could extract between 3mn ft3 and 8mn ft3/day.
“This is a highly encouraging result and great news for the UK which continues to import gas in ever increasing quantities by ship and long distance pipeline and has seen record demand for gas during the recent cold weather. The natural gas beneath Preston New Road could help secure our domestic gas supply and flow directly into the local grid, reducing CO2 emissions associated with importing LNG in tankers from around the world, including shale gas from the US, or piping gas to the UK over thousands of miles,” he said.
Cuadrilla confirmed that it has requested the upstream regulator Oil & Gas Authority (OGA) to urgently review the traffic light system (TLS) to enable the Preston New Road exploration wells to be properly tested and produced effectively, without compromising safety or environmental protection.
Subject to the outcome of such a review Cuadrilla plans to complete hydraulic fracturing of the first Preston New Road well, fracture the second well there and carry out flow testing of both wells later this year.
Egan said: “We have acquired almost 40,000 micro-seismic data points during hydraulic fracturing operations on the PNR1-z well. We believe this to be the most comprehensive microseismic data set ever collected at a shale gas well anywhere in the world. The data has been shared with the OGA and the British Geological Survey and we believe that there is more than ample evidence to justify an expert technical review of the TLS and, based on the outcome of that review, a revision at the PNR site, without compromising on safety.”
Egan said: "We look forward to completing the job. All we ask now is that we are treated fairly, with comparable seismic and ground vibration levels to similar industries in Lancashire and elsewhere in the UK who are able to work safely but more effectively with significantly higher thresholds for seismicity and ground vibration.” Cuadrilla has now shut in the well and will monitor build-up as it continues to assess the results.