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Gas Shales: Brittleness
Fracturing is effective and production can be achieved if shales are brittle
Key parameters� Mineralogy
� High Silica content � High Carbonatic content� Low Clay content
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� Geomechanics� Strenght properties� Elastic properties
Gas Shales: Well Production Profiles
18
� Total Porosity : 3 -15% - Permeability: nanodarcies� Initial production is due to the free gas contained in the pore space and in fractures� With the pressure depletion a flow contribution comes from the “desorbed” gas; lower but long lived� There is no production plateau - The production life can be >50 years
Source: Scotia Woterous
Gas Shale: has turned upside down the natural gas market in US
� Unconventional Gas by 2012 will account
for approximately half of US natural gas
production
� US total technically recoverable gas
resources are 1,700-2,200 Tcf, more than
30-40 years of production at current level
� Gas Shale is the fastest growing
unconventional play
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� Several basins and new shale gas formations are being developed thanks to the technology improvement
� By 2011 most new reserves growth will come from unconventional shale gas reservoirs
� Concepts and technologies can be exported to similar basins outside North America
Gas Shale: main US Plays
Main
Emerging
Hist
2020
ALLIANCEQuicksilver – eni
Joint Venture
No two Shale Gas Plays are alike! Every play requires a strategy of exploration and development
Gas Shale: main US Plays
� Most of the plays are within
simple or slightly deformed basins
� Targets correspond to “old” and
“brittle” organic-rich source rocks
� Commonly source rocks had
sufficient burial to reach the gas
window, avoiding over-maturity
2121
window, avoiding over-maturity
� Basin rejuvenation brought them
at relatively shallow depth
� Mainly Paleozoic plays in foreland
basins
� Mainly Jurassic-Cretaceous plays
in passive margin related systems
Gas Shale – The most famous analogous: Barnett Shale
6400
6500
BARNETTBARNETTSHALESHALE
OrganicOrganic--richrich marine marine shelfshelf depositdeposit
withwith naturalnatural fracturesfractures partiallypartially sealedsealed
2222
6600
6700
VIOLA LSTVIOLA LST
ELLENBURGERELLENBURGER
Gunn Mountain 1Gunn Mountain 1Somervell CountySomervell County
Barnett South AreaBarnett South Area
Gas shale: Well Logs Response
23
Source: Newfield
Barnett Shale Expansion
OLDER THAN 19851986 - 19901991 - 19951996 - 20002001 - 20052006 - 2008
Alliance – eni 27.5%
• The limits of the producing Barnett Shale have been defined by drilling activity
• In “Conventional” terms the Barnett Shale gas area should be considered as a large
Fort Worth
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producing Gas Field
• No “Exploration” risk is present in the Alliance area
• Alliance represents a portion of the Field Under Development
Fort Worth
Source: Quicksilver Resources
US Gas Shale Expansion
� The technology development and commercial favorable conditions have determined an
extremely rapid surge of activity in the Barnett shale
� The “learning time” in other basins is now extremely shortened
25
Gas Shale – Depth Range, well cost
� Low costs for drilling and completion is a key factor in the US gas shale expansion
� Competitive market for material and services and optimisation of D&C solutions are key
factors
26
Gas Shale – Key Technologies
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Source: Scotia Waterous
Gas Shale – Cluster horizontal drilling
� Wells are drilled horizontally in
clusters
� Pads can contain up to 24 wells
� Rigs are skid mounted
� Overall surface footprint is minimised
250’
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Alliance B#11 Wellhead
Gas Shale – Multistage Hydraulic Fracturing in Horizontal wells
� Effective fracture length is the key
objective
� It requires sufficient fracture
conductivity to allow effective
fracture fluid clean-up
� Novel hybrid slick-water fracture design has been effective, allowing placement of
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� Novel hybrid slick-water fracture design has been effective, allowing placement of
large-diameter high-conductivity proppant in fractures
� A balance between increased number of stages and increased costs is required for the
optimal solution (each shale is different – different natural fracture system and stress
regime)
- Increase Recoverable Reserves - Increase Production
100 ft
Vertical Well
2000 ft
Horizontal Well
100 ft
Vertical Well 150 ft frac
2000 ft
Hor Well with ten fracs of 75 ft
Maximize Reservoir Contact
30
222 ft2
Of Contact
20 times
Vertical example
270 times Vertical Example
13,5 times Horizontal Example
1013 times Vertical Example
50 times Horizontal Example
Multi Fracturing Branches
Extreme Reservoir Contact
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3079 times Vertical Example
152 times Horizontal Example