Data from fracking at Cuadrilla’s fracking site in Lancashire last year has been published by the industry regulator, the Oil & Gas Authority.
Cuadrilla had previously disclosed that it fully fracked only two of the proposed 41 stages during the operation – the first to work under the traffic light system for fracking-induced earth tremors.
The new material confirmed that fracking at the Preston New Road site stopped prematurely four times because of seismicity which exceeded the limit in the regulations of 0.5 local magnitude (ML).
Regulators were informed about these and another five seismic events.
The disclosures include previously unreleased “key learnings” on the fracking operation, carried out between October and December 2018.
The hydraulic fracturing report said:
“the microseismic data collected demonstrates a relationship between injection activities and induced micro-seismicity”.
The report said there were a total of 38,383 microseismic events.
Of the nine events reported to regulators under the traffic light system, six happened during fracking:
- 3 amber events during pumping where seismicity exceeded 0.0ML
- 3 red events during pumping where seismicity was 0.5ML or above
- 3 trailing events after pumping where seismicity was 0.5 or above
The report said only 17 of the planned 41 injection sleeves were hydraulically stimulated with either a mini and/or a main fracking. The volume of fluid used at each fracking stage was well below the 765m3 maximum proposed by the company.
Interpretation of microseismic data had identified two additional faults, the company also reported.
Reservoir and gas composition
The report said data from drilling and fracking revealed that the Bowland shale had “good reservoir and completion properties”.
It said 96% of the gas analysed from the well was methane. 1.6% was ethane, 0.2% propane and 0.02% isobutane. Hydrogen sulphide was 0%, according to the report.
Other information disclosed includes daily records, pumping data, records of seismic events, hydraulic fracturing images and details on sleeve depths.
Some of this information was already in the public domain following freedom of information requests. (See earlier DrillOrDrop article)
The Oil & Gas Authority said its analysis of Cuadrilla’s data was now underway. This was not, the OGA said, a review of the traffic light system, which has been requested by the shale gas industry.
The OGA said it had appointed lead scientists for four different areas of analysis:
- British Geological Survey – forecasting distribution and magnitude of seismicity
- Dr Ben Edwards – impacts of ground motion from seismicity
- Nanometrics Inc – real time forecasting to mitigate effects of seismicity
- Outer Limits Geophysics – induced seismicity and potential subsurface mechanisms
Cuadrilla has submitted a hydraulic fracturing plan for its second well at Preston New Road, PNR-2. This has to be approved by the Environment Agency and Oil & Gas Authority.
The company said it would be publishing an operational update in the next month.