Hydraulic Fracturing in Bowland Shale Lancashire, UK July. 2 nd ,2013 ISC Quarterly Meeting
Feb 22, 2016
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
Slide 6 /14
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
Slide 7 /14
Stage 2
(Cuadrilla, 2011)
5 Fracking stages
The strongest event: 10 hours after shut-in
6 Minifrac stages
Treatments
Slide 8 /14
• 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
Slide 9 /14
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)
Slide 10 /14
• B-value map shows insufficient no. of recorded events for convergence.
B-value Prediction
Work Done
Slide 11 /14
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
Slide 12 /14
• 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!