Paleokarst Reservoirs of the Lower Carboniferous (Mississippian) Madison Group and Jura-Cretaceous Success
Formation, West-Central Saskatchewan.
Dan Kohlruss
Saskatchewan Geological Survey
Ministry of Energy and Resources
Outline
• Study Area and Methods
• Regional Geological Setting
• Karst Facies
• Karst Facies Associations (Model)
• Facies Associations Maps
• Trapping Models
• Expanding the Play
• Conclusions
Outline
• Study Area and Methods
• Regional Geological Setting
• Karst Facies
• Karst Facies Associations (Model)
• Facies Associations Maps
• Trapping Models
• Expanding the Play
• Conclusions
Modified from Kohlruss 2017
Sub-CretaceousUnconformity
Sub-JurassicUnconformity
Birdbear
Sask
Gp
Dev
on
ian
Up
per
Pal
eozo
ic
Outline
• Study Area and Methods
• Regional Geological Setting
• Karst Facies
• Karst Facies Associations (Model)
• Facies Associations Maps
• Trapping Models
• Expanding the Play
• Conclusions
Modified from Hayes et al., 1994
315Ma
From Blakey, NAU Geology 1996
End Mississippian
195Ma
From Blakey, NAU Geology 1996
Early Jurassic
180Ma
From Blakey, NAU Geology 1996
Middle Jurassic
140Ma
From Blakey, NAU Geology 1996
Late Jurassic
Modified from Poulton et al., 1994
F’
F
Modified from Richards et al., 1994
Modified from Kohlruss 2017
Modified from Kohlruss 2017
Outline
• Study Area and Methods
• Regional Geological Setting
• Karst Facies
• Karst Facies Associations (Model)
• Facies Associations Maps
• Trapping Models
• Expanding the Play
• Conclusions
Loucks, 1999
Paleokarst-brecciaClassification
Facies and Facies Associations
F1: Mudstone grading to matrix supported chert-pebble conglomerate
F2: Matrix-rich, clast supported chaotic chert and sandstone Breccia
F1 F2
Loucks, 1999
111/09-04-030-28W3805.7m 802.5m
Facies 2 Thin section examples:
05-04-30-28W3: 789m 05-04-30-28W3: 792.5m 05-04-30-28W3: 793.4m
F3: Crackle Breccia
F3
Loucks, 1999
101/08-12-030-28W3
F4: Mudstone
F5: Chaotic Mud and Chert Rubble Breccia/ Conglomerate
F4 F5
Loucks, 1999
111/09-22-031-27W3820.9m
111/15-08-030-26W3854.0m
Loucks, 1999
111/09-22-031-27W3820.9m
F6
F6: Matrix-supportedChaotic Breccia
Outline
• Study Area and Methods
• Regional Geological Setting
• Karst Facies
• Karst Facies Associations (Model)
• Facies Associations Maps
• Trapping Models
• Expanding the Play
• Conclusions
Modified from Kohlruss 2017
FA1: Collapsed Cave(reservoir)
Loucks, 1999
FA2: Preserved Cave Roof
Modified from Kohlruss 2017
Loucks, 1999
FA3: Epikarst(Reservoir)
Modified from Kohlruss 2017
Loucks, 1999
FA4: Soil Breccia/Karst Paleosol
Modified from Kohlruss 2017
Loucks, 1999
Outline
• Study Area and Methods
• Regional Geological Setting
• Karst Facies
• Karst Facies Associations (Model)
• Facies Associations Maps
• Trapping Models
• Expanding the Play
• Conclusions
Modified from Kohlruss 2017
Collapsed
Upper MadisonIsopach
A’
A
B
B’
Modified from Kohlruss 2017
Collapsed
Collapsed CaveIsopach
A’
A
B
B’
Modified from Kohlruss 2017
Preserved Cave RoofIsopach
A’
A
B
B’
Modified from Kohlruss 2017
EpikarstIsopach
A’
A
B
B’
Modified from Kohlruss 2017
EpikarstStructure
A’
A
B
B’
Modified from Kohlruss 2017
Soil Breccia/Karst Paleosol
Isopach
A’
A
B
B’
Outline
• Study Area and Methods
• Regional Geological Setting
• Karst Facies and Facies Associations (Model)
• Facies Associations Maps
• Trapping Models
• Expanding the Play
• Conclusions
A’
AOil Cut =
B
B’
Gas Production = 1st 90 days gasProduction <300 e m 3 3
1st 90 days oil
1st 90 days oil + water
Reservoirs and TrappingModel
Epikarst Traps
Epikarst: pinch-out Trap
A’A
Epikarst Collapsed Cave Madison and Cave Roof
40-100% Oil CutPaleosol
Modified from Kohlruss 2017
EpikarstIsopach
A’
A
B
B’
Epikarst Traps
’
Modified from Kohlruss 2017
A’
A
B
B’
Epikarst Traps
B
B’
Modified from Kohlruss 2017
A’
A
B
B’
Pinch-outAgainst Madison
Highs
Epikarst Traps
Modified from Kohlruss 2017
A’
A
B
B’
Epikarst is thick , high and
Pinched-out by Mannville mudstones
Epikarst Traps
Modified from Kohlruss 2017
A’
A
B
B’
Anticline trap created by roll-over underlying
Madison high
Epikarst Traps
A’
AOil Cut =
B
B’
Gas Production = 1st 90 days gasProduction <300 e m 3 3
1st 90 days oil
1st 90 days oil + water
Reservoirs and TrappingModel
Collapsed Cave: Anticline and Pinch-out Trap
South North
Epikarst Collapsed Cave Madison and Cave Roof
40-100% Oil CutPaleosol
B B’
B’
B
Modified from Kohlruss 2017
A
A’
Collapsed Cave Traps
Outline
• Study Area and Methods
• Regional Geological Setting
• Karst Facies and Facies Associations (Model)
• Facies Associations Maps
• Trapping Models
• Expanding the Play
• Conclusions
Targets:• Epikarst:
• up-dip pinch-out on Madison “highs”• “highs” and roll-over edges (anticline)• Pinch-out against Mannville mudstones• Pinch-out against paleosol
• Collapsed cave:• over Madison highs (anticlines) • “pinch-outs”
• How?
Expanding the play
Epikarst Structure Madison StructureSub-Cretaceous Unconformity
Sub-Cretaceous Unconformity Westgate Structure
B’
B
Sawatzky 1966 Composite Seismic Map:
Near the top of thePaleozoic Surface
A
A’
B
Sawatzky 1966 Composite Seismic Map:
Near the top of thePaleozoic Surface
Positive features
B’
A
A’
Sub-Cretaceous Unconformity Westgate Structure
Modified from Poulton et al., 1994
Westgate Structure
Modified from Christopher, 2003
Success oil show
Success zero edge
Madison zero edge
Modified from Sawatzky, 1966; and Christopher, 2003
Westgate positivesfeatures
Success oil show
Success zero edge
Madison zero edge
141/06-23-031-23W3
38% por76.1 mD
36% por51.1 mD
40% por70.1 mD
Paleosol
Epikarst
Roof
Collapsed Cave
U. Madison
Outline
• Study Area and Methods
• Regional Geological Setting
• Karst Facies and Facies Associations (Model)
• Facies Associations Maps
• Trapping Models
• Expanding the Play
• Conclusions
Conclusions• Success Formation is a product of karsting of the Madison Group• Two karst reservoirs:
• Collapsed cave• Epikarst
• Oil and gas traps:• Structural highs - anticline traps(cave and epikarst )• Stratigraphic pinch-out traps (cave and epikarst)
• Expand play by:• Karst facies association mapping• Structure mapping• Identifying highs on the Sub-Cretaceous Unconformity:
• Using seismic (old or new)• Using Westgate as a substitute in the absence of deeper data
• Evidence for further development beyond study area• Don’t Forget - Stacked reservoir potential!
Thank You