The Origin of Matrix and Fracture Mega- Porosity in a Carbonate Bitumen Reservoir, Grosmont Formation, Saleski, Alberta T 85 R 19W4M

The Origin of Matrix and Fracture Mega- Porosity in a Carbonate Bitumen Reservoir, Grosmont Formation, Saleski, Alberta T 85 R 19W4M Kent Barrett, Dr John Hopkins, Ken Wilde and Marnie Connelly Oct 2/07

Grosmont Bitumen Resource 2 Not all of Alberta s bitumen resource is in sands Significant bitumen reserves in Devonian subcrop underlying Cretaceous deposits Grosmont contains most significant Bitumen resource in carbonates 318 Billion barrels of bitumen resource in place Laricina has acquired a significant land position in the heart of the deposit and drilled 5 delineation wells last winter

What are Mega-Porosity Zones? 3 >25% High perm (>10 Darcies) Key factor in bitumen recovery

Grosmont Bitumen Resource 4 T100 T90 Saleski Net Bitumen Pay 6-12m 12-18m 18-24m Fifth Meridian T80 24-30m Alberta Energy and Utilities Board, 1990 T70

10-26-85-19W4 Grosmont Upper Devonian Grosmont D Direton Direton_ Pa y Dgrosmont Dgrsmnt_d1 Dgrsmnt_d2 Ireton 5 4 Subdivisions Dgrsmnt_d3 Shallowing upwards cycles Grosmont C Dgrsmnt_c Dgrsmnt_c1 Dgrsmnt_c2 Grosmont B Dgrsmnt_b Dgrsmnt_a Grosmont A

Upper Grosmont Petrophysics 6 Neutron-Density Porosity Resistivity Sonic >20% Ф >100Ω 300 μ sec D 50m C 500 100 10-26-85-19W4

Post Depositional Events 7 1. Dolomitization: probably during late Devonian or Mississippian 2. Uplift, Tilting and Erosion: Jurassic to Early Cretaceous related to the Larimide Orogeny 3. Oil Migration: Cretaceous to Oligocene 4. Oil Degradation to Bitumen: Tertiary

Caveats 8 Well logs and core examination Bitumen stain a problem Porosity development has obscured and commonly obliterated sedimentary textures Core analyses of high porosity zones are problematical

Direton Grosmont Facies Laminite Dgr osmont 325 Grosmont D Mixed Laminite Mixed >100Ω >20% Ф 350 Dgr smnt_c Grosmont C Laminite Vuggy Dolomite Argillaceous Dolomite Ф 375 Dgr smnt_b 400 Dgr smnt_a 9

Direton Argillaceous Dolomite Ireton Dgr osmont Lithology: bioturbated argillaceous dolomite Fossils: Vertical burrows, brachiopods Depositional Environment: Subtidal Non-Reservoir (locally vuggy) D Dgr smnt_c C Argillaceous Dolomite Dgr smnt_b B Dgr smnt_a 10

10-22-85-19W4 Subvertical burrowing 11 Brachiopod beds

Direton 10-26-85-19W4 Ireton >20% Ф Dgr osmont 325 D 350 Dgr smnt_c Vuggy Dolomite Ф 375 C Dgr smnt_b B 400 Dgr smnt_a >100Ω 12

Facies 2- Vuggy Dolomite Massive carbonate Locally laminated Textures obscured/obliterated by vug development Fossils: some horizontal burrows, scattered corals Sedimentary Environment:? Sandwiched between tidal flat and subtidal unit Porosity: Excellent vuggy and fracture porosity, locally cavernous (can exceed 35% porosity/ 10 Darcy prem) 10-30-85-19W4 13

Bioturbation 14 CT Scan of Grosmont C at 7-26-85-19W4 Cretaceous outcrop analogue: Wabiskaw bioturbation Saleski 7-26-85-19W4 375m Cretaceous burrows

Facies 3- Laminated Dolomite Lithology: Laminated lime mudstones and grainstone. Occasional fenestral texture (U intertidal to supratidal indicator). Fossils: Occasional stromatolitic intervals (10-20 cm thick) Sedimentary Environment: Low Energy Tidal Flat (Tidal to Supratidal) Reservoir: Best matrix porosity. Typically intra-particle and intercrystalline porosity. Thick intraformational breccias with interbreccia clast porosity. Breccia Zones: 25-40% porosity/ 1-10 Darcy perm 15

Direton 10-26-85-19W4 Ireton >20% Ф Dgr osmont 325 D Laminated Dolomite 350 Dgr smnt_c C Ф 375 Dgr smnt_b B 400 Dgr smnt_a >100Ω 16

Dololaminite Textures Laminite Fenestral Fabric Stromatolite 17

Direton 10-26-85-19W4 Ireton >20% Ф Dgr osmont 325 D Mixed Lithology 350 Dgr smnt_c C Ф 375 Dgr smnt_b B 400 Dgr smnt_a >100Ω 18

Facies 4- Mixed Lithology Lithology: Green siliciclastic shale, dolomudstone and Amphipora floatstone. Sedimentary Structures: fenestral fabric, mud cracks, irregular bedding. Fossils: Occasional Amphipora beds (1-2m thick) Facies: Supratidal to lagoonal (Low energy with possible elevated salinities). Porosity and Permeability: Marginal reservoir (12-20%). Amphipora facies is generally vuggy (.1-.5 cm dia). Patchy intraparticle porosity. 19

20

Mud Cracks Profile 21 Top View

Amphipora Facies 22

23 Origin of Mega- Porosity Zones

Mega Porosity Zones High Porosity: 25 to >40% Found in Laminated and Vuggy Facies of Grosmont C & D Product of selective leaching of individual beds in Grosmont C & D Appearance: angular dolomite breccia clasts floating in bitumen 24

Brecciated Lower Grosmont D Laminite 25 Top Bottom 10-22-85-19W4

Closeup of brecciated Grosmont D 26

27 325 Evolution of a Mega Porosity Zone Grosmont C 350 Core 375 400 425

C Zone Breccia Zone Evolution 1. 2. 3. 4. Vuggy Reservoir Increased leaching and fracturing Vug collapsecrumble breccia Bitumen rich breccia zone Triple porosity system: Vugs, matrix and fractures 28

Chemistry of Carbonate Dissolution 29 Limestone solubility is highest at low temperature Limestone is most easily dissolved by fresh water Rain water is best (weakly acidic due to carbonic acid content) Solubility: Calcite (limestone) >>Dolomite

Grosmont Porosity Model 1. Early Dolomitization (5-10% porosity) 2. Fresh water leaching occurred during PreCretaceous erosional event Fresh water aggressively dissolved calcite Dolomitization is commonly incomplete Early dolomite provided rigid framework allowing preservation of cavernous porosity No cement: saturated brines discharged at surface? Laminite and Vuggy facies developed best porosity Some dolomite has been dissolved too 30

Fresh Water Diagenesis 31 Pre-McMurray Erosional Surface Fresh Water Flow

Evidence for Limestone Leaching Model Grosmont dolomites are calcite free: 1. High grain density: 2840kg/m3 (core & log data) 2. XRD data: absence of calcite/dominance of dolomite 3. Textural: dolomite rhomb micro-porosity 32

33 Calcite

Floating Dolomite Crystals- Evidence of Dissolution 34

35 SEM Photo: Corrosion of dolomite Xls due to fresh water leaching

Mega Porosity Zones Inter-breccia clast, vuggy and matrix porosity Found in Laminated and Vuggy Facies Laminated facies: Dissolution along bedding planes Vuggy Facies: Dissolution linked vugsvertical flow bias 36

37 What Role Does Karst Play?

Aspects of Karst Processes Vertical/not surface flow of groundwater Dissolution of limestone by fresh water Subterranean drainage system Caves/cave sediments/cave collapse Central France 38

Mega Porosity Reservoirs These are not caves This is good news Caves are narrow and unpredictable High porosity/permeability zones are regional stratigraphic layers Based on well control and seismic evidence 39

40 10-35 10-26 7-26 10-23 10-14-85-19W4 D Mega Ф Zones C Mega Ф Zone Cross-section emphasising the stratigraphic nature of high perm zones

So What? Predictability High Porosities/Permeabilities Grosmont bitumen at Saleski is 100,000+ centipoise Unconventional means are needed for recovery Laricina feels that it can be exploited in a scalable manner using the right recovery method 41

Bitumen Covered Core Barrel 10-27-85-19W4 42

Acknowledgements I wish to thank the Management of Laricina and our partner, OSUM for permission to present this paper 43