Fifty shades darker: integrating .... 50. 12.5 km. ´. Duvernay B Carbonate Isopach. B Carbonate. (m). 0 - 2. 3 - 4. 5 - 6 ... dark brown matrix and pale brown to grey.
Stefan Walter Krista Beavis Courtney Whibbs Sean Stricker Adam Preston Jim Jenkins Fran Hein
Recognizing Duvernay B-Carbonate Distribution and Its Potential Implications on Resource and Reserve Estimations
Alberta Energy Regulator Suite 1000 250 – 5th Street SW Calgary, AB www.aer.ca
Background
Geological Framework
What are the B Carbonate’s Properties?
Summary
The Upper Devonian (Frasnian) Duvernay Formation of the Woodbend Group is a geological formation found over most of central Alberta. Since 2009, the Alberta Energy Regulator (AER) has seen a sharp increase in the number of operators targeting this liquids-rich shale resource, particularly in the Fox Creek area.
• Recognizing the B carbonate is important as it needs to be removed from estimates of gross formation thickness for credible in-place resource estimates.
The AER characterized the petrophysical properties of the three Duvernay members to assess the reservoir quality of each. The following B carbonate parameters were investigated:
• The Duvernay has been classified into three end-member rock types: highly siliceous organic-rich mudstones, argillaceous mudstones, and nonreservoir carbonates (Dunn & Humenjuk, 2014). The B carbonate is equivalent to those nonreservoir carbonates, which are usually limestones (Hein, 2012).
• Porosity was calculated from density and typically ranges from 0 to 4%.
The Duvernay formation is a prolific shale resource in central Alberta. Due to the fact that the shale members are the source and reservoir for hydrocarbons, and the B carbonate is determined to be nonreservoir, the presence and thickness of the B carbonate member can impact a given well’s production.
Twp 80 Twp 75 Twp 70 Twp 65
Duvernay Fox Creek
Twp 60 Twp 55
Duvernay Innisfail
Twp 50 Twp 45 Twp 40 Twp 35 Twp 30
Alberta
Edmonton Calgary
CANADA
• The distribution of the B carbonate suggests that it’s controlled by paleotopography and paleobathymetry. The sharp break in the B carbonate isopach in the east is intriguing and may represent deeper tectonostratigraphic control on paleobathymetry, perhaps even basement-related structures. R6
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Duvernay Gross Isopach
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T80 T79 T78 T77
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Duvernay B Carbonate Isopach
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T79 T78 T77
T66 T65
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T75
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Duvernay Play Areas
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T93 T92 T91 T90 T89
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(m)
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ld Go
T65 T64
La
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ke
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Duvernay Fox Creek
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on
fall
Sim
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Redw
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st
T54
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T53
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T50 T49
Ancient Wall
T48 T47 T46
T52
Duvernay Innisfail
T51
T51
T41
T46
T39
11 - 12
45 - 46
79 - 80
47 - 48
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T40
19 - 20
53 - 54
87 - 88
T39
59 - 60
93 - 94
T35
27 - 28
61 - 62
95 - 96
T34
29 - 30
63 - 64
97 - 98
31 - 32
65 - 66
99 - 100
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R2
R1W6
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12.5
25
50 km
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x ple
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B Carbonate
35 - 36
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0-2
37 - 38
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3-4
39 - 40
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5-6
41 - 42
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7-8
43 - 44
9 - 10
45 - 46
11 - 12
47 - 48
(m)
13 - 14
53 - 54
T40
19 - 20
55 - 56
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25 - 26
61 - 62
T35
27 - 28
63 - 64
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29 - 30
65 - 66
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37 - 38
T47
3-4
39 - 40
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5-6
41 - 42
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7-8
43 - 44
T43
9 - 10
45 - 46
T42
11 - 12
47 - 48
T41
13 - 14
49 - 50
15 - 16
51 - 52
T41
17 - 18
53 - 54
T40
T40 T39
T38
T36
12.5
25
50 km
T34
55 - 56
T39
21 - 22
57 - 58
T38
T37
23 - 24
59 - 60
T36
25 - 26
61 - 62
T35
27 - 28
63 - 64
T34
29 - 30
65 - 66
31 - 32
67 - 68
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19 - 20
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0
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12.5
25
50 km
Duvernay petrophysical properties (regional).
Duvernay geomechanical properties, Fox Creek area.
References
Implications on Reserves Estimates
Anderson, D.M., Nobakht, M., Moghadam, S. and Mattar, L. (2010): Analysis of production data from fractured shale gas wells; SPE Unconventional Gas Conference, February 23–25, Pittsburgh, Pennsylvania, doi:10.2118/131787-MS.
• A long-duration linear flow model was used to characterize linear flow and validate production data points (Anderson, 2010) .
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• Deterministic declines were created for wells with suitable data. • Monte Carlo simulation was used to apply the decline characteristics to the remaining wells.
er rri m lla Ki d an ee
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• Current production has not yet been normalized to operator conditions. After completing the estimated ultimate recoverable (EUR) predictions across a set area, the results were plotted and compared to the location and thickness of the B carbonate. There appears to be a correlation between the gas EUR of wells in the Duvernay Formation and the presence and thickness of the B carbonate member. This becomes evident when the P50 gas EUR is plotted over the net shale thickness with the carbonate removed.
´
aw
08-28-061-18 W5M
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Ba
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sh
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R
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T44
T38
T37
31 - 32 R4
35 - 36
T42
17 - 18
59 - 60
(m)
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T43
51 - 52
57 - 58
33 - 34
T44
15 - 16
23 - 24
A & C Shales
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T41
T49
T48
T46
49 - 50
21 - 22
T36
T49
33 - 34
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fC
T27
T50 T50
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om
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pl ex
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Ba
eC Fair h
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olm
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om
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* Water saturation was not calculated for the A and C shale members. The range of values shown is from discussions with operators.
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0
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25 - 26
We would like to thank Kevin Parks, Yangchen Sheka, Hilary Corlett, Dean Rokosh, Shauna Miller, Catherine Yeon, and Laifeng Song for their support in creating this poster.
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91 - 92
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B Carbonate Versus Other Carbonate-Rich Zones
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Acknowledgements
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omple
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9 - 10
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airn C
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Duvernay isopach series.
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ater
on
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57 - 58
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73 - 74
55 - 56
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23 - 24
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ette
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5-6
´
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21 - 22
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71 - 72
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69 - 70
37 - 38
13 - 14
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35 - 36
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Cross-section location
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2-4
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Duvernay A & C Shales Isopach
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33 - 34
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Duvernay
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Based on the petrophysical properties calculated for the B carbonate, it was determined to be nonreservoir.
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• Brittleness index was calculated from Poisson’s Ratio and Young’s Modulus for the Fox Creek area and ranges from 25 to 73%.
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• Total organic carbon was calculated using Passey’s method and was typically 0% to trace amounts.
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The Duvernay formation in both play areas was deposited in a shallow marine basin resulting in similar lithologies. The reservoirs within each play area are overpressured. The play areas differ in produced fluid type and AER resource type classification. Within the Duvernay Fox Creek play, oil and gas are produced from shale zones, whereas in the Duvernay Innisfail play area, primarily oil is produced from both shale and low-permeability carbonate zones.
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The AER has identified two Duvernay play areas: Duvernay Fox Creek in the west and Duvernay Innisfail in the east.
• Water saturation was calculated using Simandoux’s method and ranged from 25 to 55%.
• The B carbonate is thickest in the east, while the organic-rich shales are thickest to the west in the Fox Creek area.
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Duvernay depositional extent in central Alberta, Canada.
• Permeability was not measured for this project but was observed in core to vary across the study area and was generally noted to be low.
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01-18-061-17 W5M
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Section from the Alberta Table of Formations indicating vertical placement of Duvernay (see red circle).
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Gas P50 EUR vs. Duvernay B Carbonate Isopach
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466.2 - 1,000
(MMscf)
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1000.1 - 2000.0
1000.1 - 2000.0 2000.1 - 3000.0
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6000.1 - 7000.0
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Duvernay gas P50 estimated ultimate recoverable.
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Duvernay gas P50 estimated ultimate recovery versus B carbonate thickness.
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8,000.1 - 9,000 0
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6000.1 - 7000.0
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5000.1 - 6000.0
4,000.1 - 5,000
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4000.1 - 5000.0
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3000.1 - 4000.0
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431.8 - 1000.0
2000.1 - 3000.0
1,000.1 - 2,000
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Gas EUR
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Gas EUR (MMscf)
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Gas EUR (MMscf)
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Legend
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Legend
Legend T58
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This series of images identifies the Duvernay B carbonate from Leduc reef talus.
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Leduc reef talus is often brecciated, with a dark brown matrix and pale brown to grey reef fragments when observed in core. Stromatoporoids are sometimes observed. On wireline logs, Leduc reef talus appears blocky on the gamma-ray log.
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A challenge to mapping the B carbonate is to distinguish it from other carbonate-rich sections on logs. For example, one important difference was observed between Leduc reef talus and B carbonate. From log analysis alone, it can be difficult to differentiate between the two, especially where the B carbonate immediately offsets Leduc reefs.
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Gas P50 EUR vs. Duvernay A & C Shale Isopach T64
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Dolostone
20 km
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Bituminous Shale
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Limestone and Dolostone
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Beaverhill Lake
Shale
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Duvernay A Majeau Lake
Duvernay Gas P50 EUR
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Leduc
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Limestone
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Duvernay C Duvernay B
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The Duvernay B carbonate is typically fine-grained, pale grey, crystalline limestone when observed in core. Fossil fragments are also commonly observed. On wireline logs, the B carbonate often appears coarsening upwards, with thin shale breaks on the gamma-ray log.
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Schematic cross-section showing the Ireton, Duvernay, Majeau Lake, Beaverhill Lake, and Leduc depositional relationships.
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Cross-section A location.
NE
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The Duvernay A and C shales are easily distinguished from the carbonate zones in core and on wireline logs. In core, the shales appear as dark brown to black, with visible oil staining. Fossils and bioturbation are occasionally observed. On wireline logs, the shales appear high on the gamma-ray log scale.
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SW
Windfall Reef
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Informal lithostratigraphic members include the A shale, the B carbonate (also referred to as the middle carbonate), and the C shale. The B carbonate is recognized to be nonreservoir.
09-03-060-14 W5M 18
Duvernay play areas.
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Dunn, L.A. and Humenjuk, J.A. (2014): Fifty shades darker: integrating sedimentology, sequence stratigraphy, chemostratigraphy and geophysics to identify sweet spots the liquids-rich Duvernay shale play, Kaybob Alberta; GeoConvention 2014: FOCUS, May 12–16, Calgary, Alberta, URL [February 2016].
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Duvernay gas P50 estimated ultimate recovery versus A and C shale thickness.
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Hein, F.J. (2012): Core descriptions of the Duvernay Formation in the East Shale, West Shale, and Kaybob/Wild River basins; in Duvernay workshop spring 2012 guidebook: core presentations, R. Wust, D. Rokosh, and J. Pawlowicz (ed.), unpublished workshop program, 36 p.
