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 Sub-Cretaceous Unconformity

Sub-Jurassic

Unconformity Gp

Upper Paleozoic Upper Birdbear

Devonian Sask 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 Modified from Hayes et al., 1994 315Ma End Mississippian

From Blakey, NAU Geology 1996 195Ma Early Jurassic

From Blakey, NAU Geology 1996 180Ma Middle Jurassic

From Blakey, NAU Geology 1996 140Ma Late Jurassic

From Blakey, NAU Geology 1996 F’

F Modified from Poulton et al., 1994 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 Facies and Facies Associations Paleokarst-breccia Classification

Loucks, 1999 111/09-04-030-28W3 805.7m 802.5m

Loucks, 1999

F1: Mudstone grading to matrix supported chert-pebble conglomerate F2: Matrix-rich, clast supported chaotic chert and sandstone Breccia

F1 F2 Facies 2 Thin section examples:

05-04-30-28W3: 789m 05-04-30-28W3: 792.5m 05-04-30-28W3: 793.4m 101/08-12-030-28W3

Loucks, 1999

F3: Crackle Breccia

F3

111/09-22-031-27W3 111/15-08-030-26W3 820.9m 854.0m

Loucks, 1999

F4: Mudstone

F5: Chaotic Mud and Chert Rubble Breccia/ Conglomerate

F4 F5

111/09-22-031-27W3 820.9m

Loucks, 1999

F6: Matrix-supported Chaotic Breccia

F6 Outline

• Study Area and Methods • Regional Geological Setting • Karst Facies • Karst Facies Associations (Model) • Facies Associations Maps • Trapping Models • Expanding the Play • Conclusions FA1: Collapsed Cave (reservoir)

Loucks, 1999

Modified from Kohlruss 2017 FA2: Preserved Cave Roof

Loucks, 1999

Modified from Kohlruss 2017 FA3: Epikarst (Reservoir)

Loucks, 1999

Modified from Kohlruss 2017 FA4: Soil Breccia/ Karst Paleosol

Loucks, 1999

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 C o l l a p A’ s e Upper Madison d A Isopach

B’

B

Modified from Kohlruss 2017 C o l l a p A’ s e Collapsed Cave d A Isopach

B’

B

Modified from Kohlruss 2017 Preserved Cave Roof Isopach

A’

A

B’

B

Modified from Kohlruss 2017 Epikarst Isopach A’

A

B’

B

Modified from Kohlruss 2017 Epikarst Structure A’

A

B’

B

Modified from Kohlruss 2017 Soil Breccia/ Karst Paleosol Isopach A’

A

B’

B

Modified from Kohlruss 2017 Outline

• Study Area and Methods • Regional Geological Setting • Karst Facies and Facies Associations (Model) • Facies Associations Maps • Trapping Models • Expanding the Play • Conclusions Epikarst Traps

Reservoirs and Trapping Model

A’

1st 90 days oil Oil Cut = A 1st 90 days oil + water B’

Gas Production = 1st 90 days gas B Production <300 e3 m 3 Epikarst: pinch-out Trap A A’

Epikarst Collapsed Cave Madison and Cave Roof

Paleosol 40-100% Oil Cut Epikarst Traps

Epikarst Isopach A’

A

’B’

B

Modified from Kohlruss 2017 Epikarst Traps

A’

A

B’

B

Modified from Kohlruss 2017 Epikarst Traps

A’

A Pinch-out Against Madison B’ Highs B

Modified from Kohlruss 2017 Epikarst Traps

A’ Epikarst is thick , high

and A Pinched-out by B’ Mannville mudstones

B

Modified from Kohlruss 2017 Epikarst Traps

A’ Anticline trap created by roll-over underlying A Madison high B’

B

Modified from Kohlruss 2017 Reservoirs and Trapping Model

A’

1st 90 days oil Oil Cut = A 1st 90 days oil + water B’

Gas Production = 1st 90 days gas B Production <300 e3 m 3 Collapsed Cave: Anticline and Pinch-out Trap

B B’ South North

Epikarst Collapsed Cave Madison and Cave Roof

Paleosol 40-100% Oil Cut Collapsed Cave Traps

A’

A

B’

B

Modified from Kohlruss 2017 Outline

• Study Area and Methods • Regional Geological Setting • Karst Facies and Facies Associations (Model) • Facies Associations Maps • Trapping Models • Expanding the Play • Conclusions Expanding the play

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? Epikarst Structure Sub-Cretaceous UnconformityMadison Structure Sub-Cretaceous Unconformity Westgate Structure Sawatzky 1966 Composite Seismic Map: B’ Near the top of the B Paleozoic Surface A’

A Sawatzky 1966 Composite Seismic Map: B’ Near the top of the B Paleozoic Surface A’ Positive features A Sub-Cretaceous Unconformity Westgate Structure Modified from Poulton et al., 1994 Westgate Structure

Success oil show

Success zero edge

Madison zero edge

Modified from Christopher, 2003 Westgate positives features

Success oil show

Success zero edge

Madison zero edge

Modified from Sawatzky, 1966; and Christopher, 2003 141/06-23-031-23W3 Paleosol 40% por 70.1 mD

Epikarst

Roof 36% por 51.1 mD

38% por Collapsed 76.1 mD 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