fraccing and shale gas - gloucester
TRANSCRIPT
Fraccing and Shale Gas
P.H.Velzeboer, M.Sc, C.Eng
Introduction
• Graduated as a Mining Engineer 1965 from Royal School of Mines, Imperial College
• Joined Shell as a Petroleum Engineer and worked internationally in:-
– Brunei, Nigeria, Sarawak, New Zealand, The Netherlands, Egypt, Syria, Scotland
• Last 10 years worked as a consultant Well Engineer on Coal bed methane, Shale gas and Well Reliability/Integrity
Overview
• Introduction
• Fraccing – What is it?
– Why do we need this?
– How do we Frac?
– Fracturing Issues • Fraccing induced seismicity
• Water table pollution
• Environmental impact
Overview (cont)
• Shale Gas Development – Shale gas development issues
– USA experience
– Europe/Africa potential
– Technical challenges • Wellcosts, drilling and Fraccing
• Environmental/Land access
– UK Development
• Conclusions
http://www.youtube.com/watch?v=VY34PQUiwOQ&feature=player_detailpage
Ultimate frac?? A permanent stable cavity caused by the detonation on an
underground nuclear test in 1961.
Fraccing issues
• Seismicity
• Pollution
• Environmental Impact
Fraccing Issues-Seismicity
Seismicity
Seismic acitivity has been recorded around the fraccing operations, M=~2.0
• At this level natural seismicity is quite common in the UK
Fraccing Issues-Seismicity
Seismic activity in the UK during the last six month.
3- Felt by few 4- Felt mainly indoors, Windows and doors rattle 5- Felt mainly indoors, small objects fall down 6- People run outside in alarm 7- Moderate damage, chimney pots fall, cracks in walls However the frac process does create many microsiesmic events, a characteristic used by the industry to monitor the growth of the fracs
Fraccing Issues - Pollution
• All fluids/chemicals used are benign – KCL
– Guar gums
• In order to reduce cost all fluids are increasingly recycled.
• Low risk of ground water pollution – Fracced zones are well below any potential
aquifers
– Dual barrier (casings) system in place
Fraccing Issues - Pollution
European practices need two independent barriers between the Hydrocarbon layer and atmosphere. These barriers are to be tested at regular intervals
Conclusion. Fracced wells are no more dangerous than Conventional oil/gas wells, probably less so because of the very low risk during drilling vis a vis blowouts
Fraccing Issues – Environmental impact
• Locations land requirement
• During drilling phase, transportation
• During frac operation, noise levels
• Noise levels during drilling and compressor activity can be made negligible
• Installation of pipeline/Power line infra structure
Shale gas development
Increasingly up beat press reports regarding shale gas reserves in the UK.
• Current potential estimate >400tcf
(annual gas consumption in UK 3tcf)
• As more exploration projects get underway this will initially get more up beat.
However
None of the exploration wells have been tested so the above can not be regarded as reserves
Shale gas development
What are the unknowns in UK shale gas development.
• Production performance…reserves
– Recovery is typically ~15%
• Availability of well sites (footprint)
• Competition from euro/US gas resources
Shale gas development
Shale gas and tight gas wells all experience sharp production declines.
Shale gas development
• Development will be from multiple well locations
• All wells are likely to be horizontal
• Each horizontal section will have multiple fracs
• The benefit for this approach is limit the locations required and reuse of fluids.
17
Shale gas development
12 1/4" hole 9 5/8” csg
8 1/2" hole 7” csg
2400 ft
10,900 ft AH,
5 7/8" hole 4 ½” Liner
5,000 ft KOP
4000 ft horizontal length stimulated at 500 ft intervals
8 stage frac
6 - 9o/100 turn
• No shallow mine hazard
• 2 7/8” completion tied into 4 ½” liner top
Typical development well
Shale gas development US experience
Shale gas development
Shale gas development
Shale gas development
Shale gas development
Frac requirements are considerable. Per well we would typically require:-
• Up to 25 stages
• 8000 – 10,000lbs per stage of proppant
• 70,000 – 100,000glns of water
• Pumping pressure ~9000psi
• 12000HHP required
Shale gas development
Shale gas development
Shale gas development
Shale gas development – will it happen?
A ‘back of the envelope’ calculation Caudrilla claim to require 100 locations for full development:- At 6 wells per location, infers 600 wells At 3 months drilling per well, infers 150 rig years 5 year development would require 20 land rigs Total drilling cost £10x106 per well, £6x109 Pipelines/Compressors etc ??? GIIP 200tcf, rec ~30tcf…0.02p/cf ~ 2p/Therm Current price at the Henry Hub ~$0.3/Therm
Conclusion
Technically possible, But:-
– UK Reserves have not yet been demonstrated
» Will offset North sea gas decline
» Will decrease reliance to imported gas
– Drilling and completion costs are about 3 X more expensive
– Population density is much higher
– Land owners may not benefit directly
Conclusion One last comparizon with the states
Fraccing – Intro
Fraccing requires a good understanding of the formation(rock) strength
Units (British Standard Units)
• Relate to a London Transport double decker (HP, length, weight) and Nelsons column (height)
Height 169ft
Length 30ft Height 14.3ft Volume 429 cuft Weight 7.35Tons Power 115hp
Fraccing – Why do we need it? Reservoir permeabilty dictates the completion type.
For Shale gas reservoirs permeability usually well below 0.1mD
Fraccing – Typical permeabilities
Fraccing – Why?
• Primarily to increase the flow area into the wellbore
Fraccing – How do we frac? Typical Shale gas well
Shale gas development-Leaking Wells
UK Shale gas headlines
Fracking will mean lower energy bills, Cuadrilla vows
Shale could fuel UK for 10 years, say experts