Community group challenges Cuadrilla’s view of geology at fracking site

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190617 PNR2 fracking plan 1

Map of faults near PNR2. Extract from Cuadrilla’s hydraulic fracturing plan for PNR2, 17 June 2019.

People living near Cuadrilla’s Lancashire fracking site have said there are “serious and fundamental errors” in the company’s interpretation of local geology.

Preston New Road Action Group, which opposes operations at the site near Blackpool, has sent a lawyer’s letter to the Environment Agency (EA) about its concerns.

The EA is currently considering Cuadrilla’s hydraulic fracturing plan for the second well at Preston New Road, PNR-2. Cuadrilla said last week it expected to begin fracking this well by the end of August.

The group challenged a previous version of the hydraulic fracturing plan for PNR-2 in November 2018. But it said the Environment Agency did not respond beyond an acknowledgement. Cuadrilla later withdrew the document.

Barrister Estelle Dehon, acting for Preston New Road Action Group (PNRAG), has now asked the EA to confirm by 16 July 2019 that it will consider concerns about the revised version of the plan before any decision is taken on it.

She has also asked the EA to provide any disagreement with the assessment of geology submitted by the group within 28 days.

Fracking plans

PNR2 section Cuadrilla Resources

Section of the PNR-1, PNR-1z and PNR-2 wells. Source: Cuadrilla Resources hydraulic fracturing plan for PNR-2

Cuadrilla drilled PNR-2 to a depth of 2,100m. The well then extends horizontally for 750m into the Upper Bowland shale formation.

The hydraulic fracturing plan for PNR-2 sets out procedures for fracking, data on nearby faults, expected size of fractures and measures to control induced earth tremors.

Since submission of the original version of the plan, new data has been made publicly available. Cuadrilla also fracked the first well at the site, PNR-1z, into the deeper Lower Bowland shale.

Despite this new information and the original PNRAG challenge, the group said there were “only insignificant amendments” to the geological interpretation in the revised version of the hydraulic fracturing plan.

PNRAG said important assumptions made by Cuadrilla about the geology had been shown to be incorrect and the group’s earlier concerns still stood.

A spokesperson for PNRAG said:

“Concerns regarding the understanding of the geology around the Preston New Road Site presented in the previous version of the Frack Plan were raised with the EA.

“Since then the industry regulator, the Oil & Gas Authority, has released information which gives further clarity of the geology and also the data from fracking well 1, which all raise more questions.

“The majority of the concerns raised have not been addressed in the current version of the Frack Plan and to date we have not had a response from the EA.

“We want to ensure that the issues raised have been fully investigated prior to any approvals to frack being given. If the geology is not properly understood we face the risks of further seismic events and potential groundwater contamination”.

Key issues

A key issue centred on the presence or absence of Millstone Grit. Cuadrilla had predicted from its 3D seismic survey that this rock formation would be above the Upper Bowland shale at the PNR-1 pilot hole. But the formation turned out to be absent. Cuadrilla said this was because of geological faulting but it would be present above the PNR-2 well.

PNRAG used a report by David Smythe, emeritus professor of geophysics at University of Glasgow, to argue that Cuadrilla had misinterpreted the seismic survey data.

Professor Smythe said it would be “geologically unrealistic” to say that Millstone Grit would be present above PNR-2 when it was not above PNR-1. The company’s argument was not supported by 3D seismic survey data, he said, and cast doubt on Cuadrilla’s interpretation of the subsurface geology.

New concerns

Professor Smythe has also reviewed new data available from the Oil & Gas Authority (OGA). PNRAG said this raised new concerns about potential pathways for fluids:

  • Cuadrilla and the OGA identified many small seismic discontinuities in the Upper Bowland shale near the wellbores
  • Many near-vertical faults cut the Top Sherwood Sandstone Group and Mercia Mudstone Group extend to the near-surface and may feed ponds and sumps near the wellsite
  • The Mercia Mudstone Group is not a homogenous low-permeability barrier to upward flow
  • The PNR-1 fault, mapped as a single fault by Cuadrilla and the OGA, is actually set of faults cutting the Lower Bowland and into the Upper Bowland, some of them cutting the wellbores

The group added that fracture modelling had not been revised in the light of what was observed in fracking PNR-1z.

The letter concluded:

“We remain confident that a proper consideration of the concerns raised by Professor Smythe will lead to the EA refusing to approve the HFP [hydraulic fracture plan) for PNR-2.”

  • DrillOrDrop invited Cuadrilla to respond to PNRAG’s legal letter to the Environment Agency. This article will be updated with any response from the company.

This content was originally published here.

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