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Santos’ CSM Activities
Steve Taylor
27 August 2004
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Main WalloonCSM Fairway
Main BaralabaCSM Fairway
Fairview -Durham RanchCSM Fairway
"Santos Operated Permits
Other Permits
MoranbahCSM Area 50 0 50 100 km
Denison TroughExploration
RomaShallow Gas
Scotia
Santos CSM Activities
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CSM Exploration
• Predominantly conventional gas in ATP 337P (Santos/Origin); northern area farmed out to Comet Ridge Ltd. for CSM exploration
• Flank of Comet anticline has shallow Rangals Coal Measures (200 – 250m) with a thick Pollux seam (7m)
• Two core holes drilled in April with moderate gas content and indications of free gas
• Anticipated future exploration comprises one test well and additional core holes to further evaluate area
Northern Denison Trough
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CSM Appraisal
• Long established conventional gas asset with infrastructure
• Similar depths and coal thickness to Walloons pilot gas projects to east
• Pleasant Hills-8a drilled in 1969 as replacement for Pleasant Hills 8 following blow-out over the Injune Creek Beds
• Well completed in 1988
• Production performance indicates gas is being produced from the adjacent coals
Roma
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CSM Production - Scotia Field
Bowen Basin Area
Eastern Queensland
Coal Seam Methane
Project Areas
148° 150°
26°
24°
26°
24°
148° 150°
Bandanna / BaralabaOutcrop Edge
Burunga Anticline
PlanetDowns
Santos Operated
CookSouth Blackwater
Blackwater
Curragh
Moura Mine Site
Emerald
Springsure
Rolleston
Blackwater
FairviewDuffers Ck
DurhamRanch
Moura/Dawson RiverProject (OCA)
Scotia Project(Santos)
Fairview/Durham Ranch
Project(Tristar/Transfield)
Moura
0 25 50
Kilometres
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Scotia Exploration HistoryGeological Background• Structural setting: Burunga Anticline, Bowen Basin
• Reservoir: Permian Baralaba Coal Measures
- three to four coal seam reservoirs
- reservoir depth: 650 to 900 m
- naturally fractured
- fracture stimulated to improve productivity
• Gas productive coals: immediate gas flow from coal seams with nil to minimal dewatering
• Gas content approx. 11 m3/t; permeability 0.1 to 15 md
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Scotia Exploration HistoryScotia Field
• Initial activity target gas in sandstones and volcanics
• Scotia coal seam methane exploration commenced in 1996 following Peat discovery in 1994
• Scotia 3, 4 and 5 drilled between 1996 and 1999 to investigate coal seam methane potential of Scotia Area
• Scotia 6 and 7 drilled in 2000 to confirm reserves for CS Energy gas contract
• Multi-well appraisal and development drilling/frac programme completed in 2001 (Scotia 8 to 16)
• Production startup May 2002
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Scotia – Schematic cross-sectionStructural style: anticlinal structure in compressive stress regime
N S
Coal Seam Methane Gas Cap AccumulationBurunga Anticline
Scotia Field
200
400
600
800
PrecipiceSandstone
RewanFormation
Upper BaralabaCoal Measure
Mid BaralabaCoal Measure
Lower BaralabaCoal Measure
DEPTHSS (m)
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Scotia – West-Seismic line
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2D Seismic Section
East West
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Scotia 4 Well Log Section
UPPER BARALABA
COAL MEASURES
•Drilled 1997 to obtain coal cores for gas desorption and reservoir characterisation
•C2 seam fracture stimulated in 1999
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Fracture Characterisation• Cleat system, microfractures (base permeability)
• Natural Fractures (enhanced permeability)
• Faults (stress distribution)
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Scotia Coal Seam Reservoir Characteristics
SEM Image of bright coal showing unmineralised cleat development
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Scotia Image Log - Coal Seam Fracture
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Scotia Image Log – Interseam Fracture
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Australian stress map
• σHmax~ 30 degrees• complex stress regime, at
cusp between strike slip and reverse:σv<σh<<σH
σh<σv<<σH
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Fracture Distribution, Reservoir
Three orientations, each consisting of a conjugate set
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Scotia• Geomechanical modelling
conducted to predict fracture distribution
• Fracture sets in Scotia are
- fold-related
- NW and NE conjugate sets
- intensity related to curvature due to local faulting
•Stress distribution modelled using stress tensor from wells
150 05 00 E
25 55 00 S
205000M E 210000M E
7125000M N
7130000M N
7135000M N
150 01 25 E 150 07 00 E26 00 00 S
25 51 50 S
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C2 CoalDepth Structure Map (mSS)
April 2004
PL 176
3ST
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5
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108
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1415
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Depth mSS280
1000
350400450500550600650700750800850900950
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Conclusions
Reverse stress geometry, high mean stress, poor stimulation
Strike-slip stress geometry, low mean stress, successfully stimulated
• In-Situ stress varies over field
- Variations due to presence of small faults
• Poor stimulation/production in areas of reverse stress regime regardless of:
- Mean & deviatory stress
- Natural fracture density
• In-situ stress tensor is the controlling factor
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• Stress regime affects stimulation efforts• Stimulation and draw-down induced faulting
Mechanical Issues
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Good Scotia Well - 7.8 MMcf/d
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