The UK’S leading onshore shale gas exploration operator Cuadrilla today dismissed claims diminishing the potential of the Bowland Shale and said: “Wait for our results!”
The operator, which resumed fracturing at the UK’s only operational shale exploration site in Preston New Road, Lancashire, last week, was responding to information published by Nottingham University today (Tuesday, August 19, 2019).
Chief Executive of Cuadrilla Francis Egan said: “Those involved in publishing this should be embarrassed. We hold more data and technical experience of the Bowland Shale than anyone else in the UK yet not once did anyone from this research group or Nottingham University contact us for our view or input.
“For the University to make the definitive claim in its press release that they have ‘determined the capacity of UK shale reserves’ strains credibility beyond breaking point. Cuadrilla is getting on with determining the capacity of UK shale reserves by the only means possible which is to drill, hydraulically fracture and test the flow rate of gas from real world wells drilled into the shale rock. Our early results are very encouraging.”
Cuadrilla resumed hydraulic fracturing at its second horizontal well at the shale exploration site in Preston New Road, Lancashire, in August. The first five stages of the programme have been successfully completed as designed, with no breaches of the intentionally conservative upper limits of the micro-seismic regulations.
In February, Cuadrilla announced results from flow-testing of the UK’s first ever horizontal shale gas exploration, which confirmed a high quality natural gas resource in the Bowland Shale, previously estimated at around 1,300 tcf by the British Geological Survey. The initial exploration programme also confirmed that the Bowland Shale formation fractures in a way that is typical of an excellent shale gas reservoir. A complex fracture network was generated in the shale and sand injected into the fractures stayed in place during flow back.
Francis added: “We’ll continue the current operational program to fracture the remaining stages of PNR2 well and then we’ll be flow-testing it. Then let’s make some statements about the reserve potential of the Bowland Shale!” Cuadrilla’s main issues with the findings of the report include:
- The paper presents a relatively new pyrolysis technique, with analysis on a couple of small rock samples from Grange Hill-1z and Rempstone-1 wells, being extrapolated to make a statement on the GIIP (gas initially in-place) for the entire Bowland Shale Formation, which extends for more than a few thousand km2, and in places is in excess of 1500m thick. Obviously, this methodology does not take into account the variability, heterogeneity and sweet spots of the Bowland Shale Formation.
- Note that the XRCT analysis was performed on very few samples of 0.5mm size and grossly underestimated the importance of upscaling. Apparently, the analysis employs various key parameters such as porosity and TOC which do not agree with Cuadrilla’s extensive internal data.
- Besides making a grossly inaccurate statement on GIIP, the paper casually applies a 10% recovery to arrive at a gas supply of less than 10 years. Recovery factors for unconventional shales in the US are typically much higher than quoted and dependent on petrophysical/reservoir parameters such as gas overpressure, which is present in the Bowland.
- The reliability of new techniques like the High Pressure Water Pyrolysis should be assessed through their application on shales that are established with a production history over a decade old, such as the Barnett Shale or the Marcellus where there are thousands of wells for validation. We do not think the application of such new techniques can be reliably applied to basins with a few exploration wells and no long term production history.
- Cuadrilla appreciates the development of potential new geochemical analysis methods. However, the methodology and experimental procedures described in the paper is difficult to follow and deserves a more thorough peer review.