Paleokarst Reservoirs of the Lower Carboniferous ... files/pdfs... · Paleokarst-breccia...

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

Modified from Kohlruss 2017

Sub-CretaceousUnconformity

Sub-JurassicUnconformity

Birdbear

Sask

Gp

Dev

on

ian

Up

per

Pal

eozo

ic

Outline



• Karst Facies



• Trapping Models


• Conclusions

Modified from Hayes et al., 1994

315Ma

From Blakey, NAU Geology 1996

End Mississippian

195Ma


Early Jurassic

180Ma


Middle Jurassic

140Ma


Late Jurassic

Modified from Poulton et al., 1994

F’

F

Modified from Richards et al., 1994

Outline



• Karst Facies



• Trapping Models


• 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



• Karst Facies



• Trapping Models


• Conclusions


FA1: Collapsed Cave(reservoir)

Loucks, 1999

FA2: Preserved Cave Roof


Loucks, 1999

FA3: Epikarst(Reservoir)


Loucks, 1999

FA4: Soil Breccia/Karst Paleosol


Loucks, 1999

Outline



• Karst Facies



• Trapping Models


• Conclusions


Collapsed

Upper MadisonIsopach

A’

A

B

B’


Collapsed

Collapsed CaveIsopach

A’

A

B

B’


Preserved Cave RoofIsopach

A’

A

B

B’


EpikarstIsopach

A’

A

B

B’


EpikarstStructure

A’

A

B

B’


Soil Breccia/Karst Paleosol

Isopach

A’

A

B

B’

Outline



• Karst Facies and Facies Associations (Model)


• Trapping Models


• 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


EpikarstIsopach

A’

A

B

B’

Epikarst Traps

’


A’

A

B

B’

Epikarst Traps

B

B’


A’

A

B

B’

Pinch-outAgainst Madison

Highs

Epikarst Traps


A’

A

B

B’

Epikarst is thick , high and

Pinched-out by Mannville mudstones

Epikarst Traps


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


A

A’

Collapsed Cave Traps

Outline





• Trapping Models


• 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





• Trapping Models


• 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

Paleokarst Reservoirs of the Lower Carboniferous ... files/pdfs... · Paleokarst-breccia...

Documents

Transcript of Paleokarst Reservoirs of the Lower Carboniferous ... files/pdfs... · Paleokarst-breccia...