Unconventional “Shale Plays” in MT · Unconventional “Shale Plays” in MT A Look at the...
Transcript of Unconventional “Shale Plays” in MT · Unconventional “Shale Plays” in MT A Look at the...
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Unconventional “Shale Plays” in MT
A Look at the Geology & Development of the Bakken and Heath Formations
Jay Gunderson
Montana Bureau of Mines and Geology
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Why Shales?
• Traditional “Source Rocks” – Mostly clays - often high organic content – Little pore space and no permeability
• Kerogens are baked into oil & gas; migrate out of the shale and
into conventional traps
• New technology has turned these traditional source rocks into reservoir targets
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Horizontal Drilling & Frac’ing
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Bakken has been the “Proving Ground”
Most is from the Bakken (600,000 bopd)
Current estimates of recoverable oil from the Bakken/ThreeForks range from 3-24 Billion bbls
Oil from Shale now ~16% of US Production
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Requirements for Shale Resource Plays
• Large area of organic-rich source rock
• Heat, pressure, and time to mature
• Expulsion of HC from source rocks into adjacent rocks
• Trapping of HC in overlying and underlying reservoirs that are porous, but low permeability
• Technology to extract HC using natural or artificial fractures
Lynn Helms, ND DMR
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Sappington?
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Williston Basin Stratigraphy
Bakken Three Forks
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The Bakken “Petroleum System”
~120 ft
Southwest (MT) Northeast (ND)
Source beds
DEPTH: 9,000-11,000 feet
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Burial & Oil Generation
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1953 Discovery Well
The Early Years
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Elm Coulee Field
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The Shift to ND
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Geology dictates where the rigs go
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The “Boom” has Passed
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Current Activity
• Rigs are trickling back into MT – 10-15 rigs to drill & hold leases
• Still some Elm Coulee infill wells
• Geopressured area
• South edge - upper shale
• Marginal production to the north
• No economic production NW of Brockton-Froid FZ yet
Sidney
Plentywood
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Glacier Co., MT • Maybe a dozen wells in
last 3 years • < 50 bopd max • no pressure?
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There will continue to be Bakken drilling in Elm Coulee and to the north (?),
but probably not elsewhere in the State …..at least for now.
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Heath Formation
Wyoming Shelf
Alberta Shelf
Depth: 0 to 5000’ Some in Judith Basin
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600 my
250 my
65 my
Central Montana
Stratigraphy
EROSION
FAULTED/FOLDED
Not simple layer-cake
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Heath Formation – Complex Mix of Lithologies
Brittle, fractures – especially on structure
SHALE +/- Coal, gypsum, DM, LS
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TOC ≈ 2.8%
TOC ≈ 10.5%
LS ≈ 9% vuggy φ
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Complex Geology: folded & faulted Oil Migrated into Permeable Rocks & Conventional Traps
Heath 200-300’
From AAPG-RMS 1972
Over 40 oil fields in Central MT Most are Amsden-Tyler Cumulative oil production 110-140 MMBO (sourced from Heath)
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Exploration Status?
• We just don’t know that much yet; few wells drilled
• Since 2009 – ~ 10 vertical wells drilled
• Coring: oil shows, fractures, water/oil saturation, porosity, etc
– ~15 horizontal wells drilled • Operators testing drilling and completion techniques • Only 2-3 on production
• 1 rig currently running
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Cabot 100,000 acres Fidelity 80,000 acres Central MT Resources Cirque Resources Voyager 33,500 acres Endeavor 75,000 acres
Cabot O&G Fidelity E&P Central MT Resources Cirque Resources True Oil LLC
EOG Bakken ‘08
V
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Cabot 100,000 acres Fidelity 80,000 acres Central MT Resources Cirque Resources Voyager 33,500 acres Endeavor 75,000 acres
Cabot O&G Fidelity E&P Central MT Resources Cirque Resources True Oil LLC
EOG Bakken ‘08
V
Firefoot (H11) 1 BO / 8 BW
Shadowfax (H11) IP 10 BO / 36 BW <1 BO / <1 BW
Asfaloth (H11) 0 / 50 BW
Snowmane (H11) 1B (H11) 1 BO / 1 BW 2 (D11) 1 BO / 30 BW 3 (V11) 0 BO / 60 BW 4 (V11) 10 BO / 50 BW
Garnet (H10) DH
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Cabot 100,000 acres Fidelity 80,000 acres Central MT Resources Cirque Resources Voyager 33,500 acres Endeavor 75,000 acres
Cabot O&G Fidelity E&P Central MT Resources Cirque Resources True Oil LLC
Schmidt (H12) IP? 250 BO / 65 BW
Rock Happy (H12) IP 271 BO/428 BW
Hit Parade (H12) IP 93 BO / 368 BW 40 BO / 100 BW
V
Firefoot (H11) 1 BO / 8 BW
Shadowfax (H11) IP 10 BO / 36 BW <1 BO / <1 BW
Asfaloth (H11) 0 / 50 BW
Snowmane (H11) 1B (H11) 1 BO / 1 BW 2 (D11) 1 BO / 30 BW 3 (V11) 0 BO / 60 BW 4 (V11) 10 BO / 50 BW
Garnet (H10) DH
EOG Bakken ‘08
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So, is it another Bakken?
We probably won’t know for a while yet……..“wait & see”
• The potential is certainly there: Both have – Organic rich black shales of similar age
– Low porosity, low perm shales, high TOC
– Both in oil window – thermally mature
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Heath is a little more Complex
• Oil has migrated out of the system – Juxtaposition with conventional reservoirs – Faults may provide pathways
• Central MT is structurally complex: faulted / folded, erosional unconformities
• Testing different zones – which is the “Reservoir”?
• Reservoir Pressure – can production be sustained?
……but remember, it took ~50 years for the Bakken to become what it is today
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Impact on Groundwater?
• Potential for leakage of Frac fluid into groundwater aquifers
• At depth due to frac’ing
• Surface spills
• Operators do not want to frac into water-bearing fms
• Water consumption • 2-mile lateral uses ~2 million gal of water for frac job.
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MBOG Rules Adopted 2011
• Pressure test casing & equipment
• Report constituents in Frac fluid
• Trade secrets protected unless health care emergency demands disclosure
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www.fracfocus.org
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Estimated Water Use in MT in 2000
Frac needs: about 1 million gal/day
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It’s all about reservoir contact & drainage
• Patterns to drain efficiently
• Longer laterals
• Natural Fractures (SW-NE)
• Hydraulic Fractures
• Reservoir Pressure
Northwestern Elm Coulee
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Rig Count
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Summary – Bakken Petroleum System
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Return on Investment: 3-5 times Cost Recovery: 2-3 years
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Middle Bakken: Large Area, Complex Depositional Env., Multiple Reservoir Targets
~270 MMBOE Recoverable
~300 MMBOE Recoverable
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Horizontal Drilling
• Horizontal drilling not new…1980’s
• But the ability to land it in a thin zone and stay there
– Rotary steerable bit
– LWD/MWD logging
• Increase length to contact more reservoir
• Intercept as many natural fractures as possible
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Fractures
• Permeability
• Early days – find structures & depo edges
• Natural Fractures created by tectonics (stress fields)
• Micro Fractures created by increased pressure from fluid expansion as kerogens go to oil generation (increased volume)
• Artificial: hydro-fracturing
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• Hydrofracturing is also not new (late 1940’s)
• Pressurize to exceed fracture gradient, crack the rocks & prop the cracks open
• Create pathways for fluid flow (permeability)
• Frac fluid is ~99% water and sand (or ceramics); 1% things to worry about.
Hydrofracturing (“fracking”)
Fracking has not caused any earthquakes
Water contamination can be mitigated; water conservation may be a bigger issue
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Original Oil in Place (OOIP)
• At 10.5 gal/ton (good stuff); 2.8 gal/ton (rest)
• Estimates of Heath OOIP: • ~3 MMbbls per mi2 (Cox only)
– But we could add another 10 MMbbls if we assume another 75’ of lower TOC rocks
• Cirque suggests ~20 MMbbls per mi2
• Compare to Bakken commonly taken to be about 5 MMbbls per mi2
…………but is it still there?
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Expulsion & Migration
• Oil generated at depth • Expansion – Pressure – Fractures? • Forced into nearby tight rocks OR migrates out
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Two recently completed wells have reported production
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This is the big deal Oil from Shale now ~16% of US Production
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Heath Shale: Central Montana Trough Big Snowy Group
Wyoming Shelf
Alberta Shelf
Depth: 0 to 5000’ Some in Judith Basin
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Geology can be Complex: complicated by erosional surfaces, lateral facies changes &
later folding
Heath 200-300’
From AAPG-RMS 1972
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Oil Migrated into Permeable Rocks & Conventional Traps
Sumatra Field
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But remember – it took ~50 years for the Bakken to become what it is today