Hydraulic Fracturing in Bowland Shale Lancashire, UK

1. Hydraulic Fracturing in Bowland Shale Lancashire, UK ISC Quarterly Meeting July. 2nd,2013

2. Objectives • Analyzing Data • Correlating the fracking job and seismicity • Improved microseismic imaging • Developing a predictive model based on geophysical data

3. Summary • Background • GemechanicalStudy of BowlandShale Seismicity • Academic Review • Work Done

4. Background Preese Hall 1 well (PH1) Bowland Shale • Area of Low Seismicity • ML=4.4 near Lancaster (1835) • Cuadrilla: 200 trillion cubic feet of gas-in-place • The first unconventional shale gas well in the UK http://www.dartgas.com/page/Europe/United_Kingdom/UK_Shale/ http://maps.lynxinfo.co.uk/UKOGL_LIVEV2/main.html# From: UK Onshore Geophysical Library

5. Seismic Events http://www.bgs.ac.uk/research/earthquakes/blackpoolMay2011.html 48 non-felt events: -1.5<ML<1.4 31 March to 27 May 2011

6. Gemechanical study of Bowland Shale seismicity (Cuadrilla, 2011) PH1 Thick Anhydrite Craven Fault system Thistleton Fault Thistleton fault mapped by seismic Numerous wellbore failures: strike-slip faulting stress regime (σHmax > σV > σHmin ) Carboniferous rocks overlain by Permian and Triassic strata Pendle Fault system The seismicity caused by a type A fault σHmax≈1.25 psi/ft

7. Treatments 5 Fracking stages 6 Minifrac stages Stage 2 The strongest event: 10 hours after shut-in (Cuadrilla, 2011)

8. Conclusion of the study • No certainty about the seismicity mechanism / Timing of the seismicity & Similar signals • Strike-slip stress regime • Events: present in stages 2&4 / absent in stages1,3, &5 • Worst case vertical fluid migration: 2000 ft / Thick impermeable formation on top of the Bowland shale as well as the anhydrite layer • Seismicity unlikely to happen in next wells • Proppant: hard for slurry to enter a fault • PH 1: fluid entrance into a fault => unlikely to occur again

9. Academic review Plausible Cause • Direct fluid Injection into adjacent fault zone -Fault intersected the wellbore OR Fluid was able to flow into fault through bedding planes. • Critically stressed faults in the region Finding • Reduction in normal stress on fault causing it to fail repeatedly in a series of small events.(Strike –Slip Stress regime) • Reservoir is overpressurized and fluid leakoff is unusually high (Green, et. al,2012)

10. Work Done B-value Prediction • B-value map shows insufficient no. of recorded events for convergence.

11. Work Done Trend b/w ∆BHP and Seismic Events Stage II

12. Work Done • Co-relation between Qi,BHP and magnitude of events. -Injection Data for stage IV and Stage V. • Prediction of Time lag b/w ∆BHP and seismic events. -Accurate data for all stages. Future Work and Limitations

13. References • British Geologic Survey • Commodities Now, ‘Fracking 'probable' cause of Lancashire quakes,’ Nov., 2011 • Davies,R, et. al.,’ Shale Gas: The Rocks Matter,’ • CuadrillaResources,’Geomechanical study of the Bowland Shale seismicity,’ 2011 • Green, C.,A., et. al.,‘Preese Hall Shale Gas Fracturing Review & Recommendations for Induced Seismic Mitigation,’2012

14. Thank You!