Hydraulic Fracturing in Bowland Shale Lancashire, UK

July. 2nd,2013

ISC Quarterly Meeting

Slide 2 /14

• Analyzing Data

• Correlating the fracking job and seismicity

• Improved microseismic imaging

• Developing a predictive model based on geophysical

data

Objectives

Slide 3 /14

• Background

• Gemechanical Study of Bowland Shale Seismicity

• Academic Review

• Work Done

Summary

Slide 4 /14From: UK Onshore Geophysical Library

NUMBER WELLSORTABLE DEV COUNTY SPUD COMPLETED Latitude LongitudeLJ/06- 5 LJ/06- 005 V LANCS 16-Aug-10 16-Apr-11 53.821946 -2.949049

http://maps.lynxinfo.co.uk/UKOGL_LIVEV2/main.html#

Preese Hall 1 well (PH1)

http://www.dartgas.com/page/Europe/United_Kingdom/UK_Shale/

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

Background

Slide 5 /14

http://www.bgs.ac.uk/research/earthquakes/blackpoolMay2011.html

48 non-felt events: -1.5<ML<1.4 31 March to 27 May 2011

Seismic Events

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Numerous wellbore failures:

strike-slip faulting stress regime

(σHmax > σV > σHmin )

σHmax≈1.25 psi/ft

Craven Fault

system

Pendle Fault

system

(Cuadrilla, 2011)

Thick Anhydrite

Thistleton fault mapped by seismic

The seismicity caused by a type A fault

Thistleton Fault

PH1

Carboniferous rocks overlain by Permian and

Triassic strata

Gemechanical study of Bowland Shale seismicity

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Stage 2

(Cuadrilla, 2011)

5 Fracking stages

The strongest event: 10 hours after shut-in

6 Minifrac stages

Treatments

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• 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 wellso Proppant: hard for slurry to enter a fault o PH 1: fluid entrance into a fault => unlikely to occur again

Conclusion of the study

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Plausible Causeo Direct fluid Injection into adjacent fault zone-Fault intersected the wellbore OR Fluid was able to flow into

fault through bedding planes.o Critically stressed faults in the regionFindingo Reduction in normal stress on fault causing it to fail

repeatedly in a series of small events.(Strike –Slip Stress regime)

o Reservoir is overpressurized and fluid leakoff is unusually high

Academic review

(Green, et. al,2012)

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• B-value map shows insufficient no. of recorded events for convergence.

B-value Prediction

Work Done

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Trend b/w ∆BHP and Seismic Events Stage II

8 10 12 14 16 18 20 22 24 26 28

-2000

0

2000

4000

6000

8000

10000

-0.5

0

0.5

1

1.5

2

2.5

∆BHP

Events

Time in hrs.

∆BHP

Mag

nitu

de

Work Done

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• 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

Work Done

Slide 13 /14

• British Geologic Survey• Commodities Now, ‘Fracking 'probable' cause of Lancashire

quakes,’ Nov., 2011 • Davies,R, et. al.,’ Shale Gas: The Rocks Matter,’ • Cuadrilla Resources,’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

References

Thank You!