Unraveling Reservoir Architecture of Complex Low Net: Gross Red-Bed Fluvial Sequence Using Palaeosoils and Chemostratigraphy* Andrea Moscariello1 Search and Discovery Article #50173 (2009) Posted April 27, 2009 *Adapted from oral presentation at AAPG International Conference and Exhibition, Cape Town, South Africa, October 26-29, 2008. 1
Dept of Geotechnology, Delft Technical University, Delft, Netherlands (
[email protected])
Abstract The lack of stratigraphical markers and microfossils in continental, fluvial, low net-to-gross red-bed sequences, make conventional elog based interwell correlations particularly challenging. Effective reservoir modeling and development of such reservoirs therefore rely on application of sedimentological concepts that set the basis for a robust correlation framework. This paper presents a case study located offshore UK, where the sedimentary characteristics and reservoir architecture of a fluvial reservoir were re-evaluated by applying a multidisciplinary approach including pedofacies analysis and chemostratigraphy. This study developed an independent chronostratigraphic framework based on chemostratigraphy related primarily to a careful description and interpretation of “nonreservoir” facies. The innovative use of shear sonic to detect palaeosols in uncored sections was also used for modeling channel distribution. This approach ultimately allowed the identification of meaningful stratigraphic units characterised by changes in the sequence of vertical stacking of pedofacies types. The latter were interpreted as the result of different depositional environments, hence reservoir architecture and connectivity. The application of the pedofacies concept, the use of shear logs, associated with heavy-mineral analysis, allowed an independent validation of the chemostratigraphic correlation scheme, and provided a framework for more sophisticated reservoir modeling. In particular, the recognition of the overall style of fluvial behaviour that may influence the style of channel sand-body stacking provided a predictive model to assess reservoir lateral and vertical connectivity. Also, indication of proximity to channel belts enabled identification of stratigraphical which are likely to be laterally connected to channels not penetrated in the wellbore.
Unraveling reservoir architecture of complex low net:gross red-bed fluvial sequence using palaeosoils and chemostratigraphy. Andrea Moscariello AAPG Cape Town, October 2008
Outline ■
Introduction
■
The Barren Red Measures Group: ■
■
The case study: Schooner and Ketch Fields SNS, UK ■ ■ ■ ■ ■
■
Palaeogeography, Stratigraphy, Climate and Tectonic
Sedimentology First Lithostrat. Correlation & Conceptual geological model Field Performance Second Chemostrat. Correlation and Paleosoils Impact of new integrated approach and results
Conclusions & Learnings Slide 1
Outline ■
Introduction
■
The Barren Red Measures Group: ■
■
The case study: Schooner and Ketch Fields SNS, UK ■ ■ ■ ■ ■
■
Palaeogeography, Stratigraphy Climate and Tectonic
Sedimentology First Lithostrat. Correlation & Conceptual geological model Field Performance Second Chemostrat. Correlation and Paleosoils Impact of new integrated approach and results
Conclusions & Learnings Slide 2
Challenges of distal fluvial systems GR (API) 50
150
250
12800
■
Distal fluvial sandstone associated with red-beds/barren sedimentary successions are common HC-bearing reservoirs worldwide (e.g. Unaizah Fm, Gharif Fm, TAGI, Bunter Sst FM, Silverpit Fm, etc.)
12900
13000
13100
■
Understanding reservoir architecture and sand connectivity is key to establish effective predictive models
13200
13300
■
■
Correlation is challenging because of the difficulty to apply common chronostratigraphic methods (e.g. biostrat)
13400
13500
Even more complicate in endoreic basins where the fluvial system is located away from sea/lacustrine flooding.
13600
Slide 3
Outline ■
Introduction
■
The Barren Red Measures Group: ■
■
The case study: Schooner and Ketch Fields SNS, UK ■ ■ ■ ■ ■
■
Palaeogeography, Stratigraphy, Climate and Tectonic
Sedimentology First Lithostrat. Correlation & Conceptual geological model Field Performance Second Chemostrat Correlation and Paleosoils Impact of new integrated approach and results
Conclusions & Learnings Slide 4
Palaeogeography – Westphalian C
Mid North Sea High
IRL
Barren Red Measures Group •Upper Carboniferous continental fluvial system •Variscan foreland basin
UK
Silver Pit Basin
•Southern Margin of the foreland bulge (Mid North Sea High)
Variscan front
Slide 5
Stratigraphy, Climate and Tectonic STAGES
Age Ma
SAKMARIEN
ASSELIEN
Depositional environment
desert playa lake
Climate
Tectonic
arid wetting upwards
subsiding basin
295
305
WESTPHALIAN D
WESTPHALIAN C 311
Coal Measures Group
WESTPHALIAN
SILESIAN
308
WESTPHALIAN B
Variscan deformation
Saalian Unconf.
Barren Red Measures Group Boulton Ketch Fm Fm
STEPHANIAN
CARBONIFEROUS
Formation Rotliegend Group Silver Pit Claystone
SER IES
AUTUNIAN
SUB SYS TEM
UPPER
PERMIAN
SYSTEM
WESTPHALIAN Stratigraphic Subdivisions A of the British Carboniferous.
low gradient fluvial plain dominated by low sinuosity braided rivers
coastal delta plain dominated by low sinuosity meandering rivers
warm and humid; drying upwards
subsiding southern flank of the Mid North Sea High early Variscan deformation
warm and humid
Foreland of Variscan thrust zone
315
(Moscariello, 2003)
Slide 6
Outline ■
Introduction
■
The Barren Red Measures Group: ■
■
The case study: Schooner and Ketch Fields SNS, UK ■ ■ ■ ■ ■
■
Palaeogeography, Stratigraphy Climate and Tectonic
Sedimentology First Lithostrat. Correlation & Conceptual geological model Field Performance Second Chemostrat. Correlation and Paleosoils Impact of new integrated approach and results
Conclusions Slide 7
Study area Location
Mid North Sea High
IRL
UK Silver Pit Basin
Variscan front
Distance from Mid North Sea High: ca. 120 km
Slide 8
GR (API) 50
150
250
12800
12900
GR (API)
13000 0
50
100
12800
13100 12900
13200
Well A
Depth (ft, MDAH)
12450
12500
50
100
150
13300
13400
Depth (ft, MDAH)
GR (API) 0
Depth (ft, MDAH)
13000
12550
13100
13200
12600
13500
12650
13300
13600
Well A
Well G 13400
13700
13800
Well B 13900
Slide 9
The Ketch Formation ■ Correlation Methods for a Subsurface Formation ■ ■ ■ ■ ■ ■ ■
Seismic: very deep and below salt Biostratigraphy: barren Magneto-stratigraphy: too short time of deposition Tuff layers (tephra): no volcanic activity Vertebrate taphonomy: no too many around Coals: absent Litho-stratigraphy: vertical packages based on wireline logs and extrapolated laterally (distinct N:G intervals)
■ Sequence stratigraphy ? ■ Palaeosoils ? ■ Chemo-stratigraphy ? Slide 10
Reservoir Sedimentology - Facies Based on sedimentological core analysis and wireline log. Facies
Composite channels Single channels Proximal crevasse splay Fine-grained lacustrine and overbank deposits Sols
Grain-size
Gravel 10-15% Coarse to medium sand 35-40% Fine sand 20-30% Silt 30-40% Clay 5 -10%
N:G
30 %
Slide 11
Reservoir facies 1 - Fluvial channel Stacked/amalgamated channel fills with fining upward trend. Planar and trough cross bedding
Vertically aggraded and laterally coalesced low sinuosity braided channel complex
Pebble conglomerate/lag Cross bedded sets typically developed at the base of sand body
Low sinuosity braided channel bar complex deposited during high stage flood conditions
Pebble conglomerate dominated by Qz clasts. Abrupt changes to finer grained Sandstone
Slide 12
Non-Reservoir facies 2 - Flood Plain Bedded very fine grained sandstone with interbedded silt-claystone Fining upward trend Ripple-cross and planar lamination
Proximal overbank deposits. Sheetfloods, crevasse splays with interbedded floodplain deposits
Massive very fine sandstone Interfluvial/flood plain with soft sedimentary deposits relatively well deformation drained
Haematitic reddish/brown silt/claystone with rootlet/plant remains and pedogenic fabric
Palaesois
Pedogenic/mottled/churned clay/peds rich/siltstone with calcretes Slide 13
Conceptual Geological model Depositional environment of the Barren Red Measures - Upper Carboniferous SNS
Low sinuosity, sandy, braided river belts
Inland source area
Large interfluves with well layered mud, siltstone and ephemeral lacustrine deposits.
Slide 14
Model 1: Litho-stratigraphic correlation across the Schooner Field (flattened at Ketch Formation base ) SA01/03S1 True Vertical Depth Sub Sea none MD KB none FEET facies
TVD SS 0 CGR_01R 140 none MD KB 0 FLOWUP 100 FEET CGR_01R none FEET facies No fil Plus Minus
SA04/08 True Vertical Depth Sub Sea
44/26-3 True Vertical Depth Sub Sea
TVD SS 0 GR_00J 140 none 0 FLOWUP 100 MD KB none FEET FEET GR_00J facies No fil Plus Minus
TVD SS 0 GR_00J 140 45 CNL_00J -15 none MD KB FEET FDC_00J none FEET GR_00J facies No fil No fil Plus Minus Plus Minus
1 3 5 0 0
1 3 2 5 6 1 3 3 8 8
1 3 2 9 6 .9
1 4 0 0 0
1 4 2 5 4
1 4 0 9 6
1 2 5 0 0 1 2 6 8 5 .3
1 4 0 0 0
1 5 0 0 0 1 5 0 0 6 .5 1 5 0 0 0
1 3 0 7 5 1 3 0 0 0
1 3 7 3 0
1 3 6 3 8 .8
1 4 6 8 6 .4 1 4 7 7 5
1 3 0 7 5 1 3 0 0 0 1 3 1 3 1 .5
1 4 5 0 0
1 3 9 4 3 .3
1 3 2 6 6 .1
1 4 4 2 3
1 2 6 8 7 .2
1 3 5 0 0
1 4 5 0 0
1 2 5 0 0
1 3 5 0 0
1 3 5 0 0
1 2 7 8 9 .6
1 3 5 0 0 1 3 6 9 5 .3
1 3 3 3 1
1 2 9 2 3 .8 1 3 0 7 5 .1 1 3 0 0 0
1 2 7 9 4 .2
1 3 6 1 3 1 3 7 8 9
1 3 1 6 5
1 3 0 0 0
1 3 0 0 0
1 2 5 0 0 1 3 5 3 6 1 3 5 0 0
1 2 0 6 6 .7 1 2 0 0 0 1 2 1 2 1 .5 1 2 2 4 7 .2
1 7 5 0 0 1 8 0 0 0
1 8 8 1 0 .4 1 9 0 0 0
1 7 9 7 4 .1
COAL MEASURES
1 3 5 0 0
1 8 0 0 0
1 3 0 7 5 .1 1 3 0 0 0
1 3 1 6 8 .1
1 3 0 7 5 .1 1 3 0 0 0
1 3 0 0 0
1 3 0 7 5 1 3 0 0 0
1 7 5 0 0
1 3 0 0 0
1 8 5 0 0
1 8 4 6 0
1 2 8 4 7 .8
1 7 3 5 8
1 2 7 7 3
1 2 6 5 3 .2
1 2 5 0 0
1 2 5 0 0 1 2 6 8 0 .2
1 2 9 0 6 .2 3 1 3 2 0 5 .1
1 2 5 0 0 1 7 0 0 0
1 2 5 0 0
1 6 9 7 8 .5 9
1 2 3 7 6 .5 8
1 2 4 3 8 7 .5 9
1 1 2 2 4 4 0 0 9 9 ..8 5 4
1 1 7 7 7 7 9 9 1 0 .3 5
1 6 5 0 0
1 2 0 0 0
1 2 0 0 0
1 2 3 4 5 4 .9 3 2
1 2 5 0 0 1 2 5 0 0 1 2 7 7 6 .2 3
FWL
Coal Measures
1 3 0 7 5 .1 1 3 0 0 0
FWL
BRA
FWL
FWL
BRB
FWL
1 2 8 3 8
1 2 0 0 0 1 2 0 0 0
1 2 0 0 0
Saalian Unconformity
COAL MEASURES
BRC
1 2 4 4 9 .3
1 2 0 0 0
1 2 2 1 6
1 3 3 7 8
1 3 0 0 0
1 7 0 0 0
1 6 0 0 0
1 2 7 6 2
TVD SS 0 GRS_00J 140 LDEN_01R FEET GRS_00J CNL_01R No fil No fil Plus Minus Plus Minus
SE
1 3 1 6 6 .1
SA02/05 True Vertical Depth Sub Sea
TVD SS 0 GR_00J 100 none MD KB none FEET FEET GR_00J facies No fil Plus Minus
Well G
1 2 6 7 1
SA03/07 TVD SS
TVD SS 0 GRIC_00J 80 none MD KB FEET GRIC_00J none FEET facies No fil Plus Minus
Well F
Well E
1 1 9 1 5
1 1 7 8 5 .1
SA05/01 TVD SS
TVD SS 0 depthGR 140 45 CNL_00J -15 none MD KB FEET depthGR FDC_00J none FEET No fil No fil Plus Minus Plus Minus
Well D
1 3 0 7 5 .1 1 3 0 0 0
44/26-2 True Vertical Depth Sub Sea
Well C
1 2 5 0 0
44/26-4 True Vertical Depth Sub Sea TVD SS 0 GR_00J 140 45 CNL_00J -15 none MD KB FEET GR_00J FDC_00J none FEET No fil No fil Plus Minus Plus Minus SILVERPIT CLAYSTO
Well B
Well A
NW
Slide 15
Model 1: Sequence stratigraphy approach
Well G
Unit C: Finer sediments indicating increased rates of BL rise. Great floodplain storage of accommodation
Well E
Well D
Unit B: Non reservoir Well A
Unit A: Aggradation at early base level rise and valley infill caused by backstepping
1996 model:
Width range: 250-4000 m; T:W range: 1:9 - 1:500 Slide 16
Field Production Performance
Gas flow rate
Well 2
Well 4 Well 5 Well 3 Well 6
Well 1
Year 1/10
Year 2/4
Year 2/10
Year 3/4
e.g. Well 4 actual vs. planned
Year 3/10
Time
Slide 17
Model 2: Chemo-stratigraphic correlation across Schooner Field (flattened at Ketch Formation base ) SA02/05 True Vertical Depth Sub Sea
TVD SS 0 GR_00J 100 none MD KB none FEET FEET GR_00J facies No fil Plus Minus
TVD SS 0 GRS_00J 140 LDEN_01R FEET GRS_00J CNL_01R No fil No fil Plus Minus Plus Minus
Well F
Well E SA01/03S1 True Vertical Depth Sub Sea
none MD KB none FEET facies
Well G
SA04/08 True Vertical Depth Sub Sea
TVD SS 0 CGR_01R 140 none MD KB 0 FLOWUP 100 FEET CGR_01R none FEET facies No fil Plus Minus
TVD SS 0 GR_00J 140 45 CNL_00J -15 none MD KB FEET GR_00J FDC_00J none FEET facies No fil No fil Plus Minus Plus Minus 1 2 6 7 1
1 3 0 0 0
1 3 5 0 0
1 3 1 6 6 .1
MD KB FEET
12761
12670
12600
12217.3
12200
12217.3 12200
12800 12630.8
12600
12810.8
13000
12630.8 12600 12810.8 12800
13200
13675
FWL
13200
13166
13075
13342
13293
13400 13595
B 13600
13074.7 13125.7
13503.9
13074.7 13125.7
14408 14400
13800
12600
18360 18443 18400
12677.1
12782.9 12836.8 12800
13400
13489
13397.9
12981.7 13000
12981.7 13000
13725 13695.2 13894
13600
13098 13075 13228.2 13200
14237 14200
13384
13536
13200
12800
13400
12802.4 12800 12951.8 13000
14069
14000
13937
12352.7 12561.7
18195 18200
17400
17200
12600 0
12445.6 12400
18006 18000 12600
17125.1 17357.5 17331.1
12676
12481 12652.8 12633.7 12600
12568 1273312713
12553.6
16981.4 17000
12378.5 12400
12438 12400
12345.3 12400 12475.3
Unit 2 Unit 1
12640.2 12620.2 12600
13800
17788 17800
12407.8 12400
Unit 4 16800
12200
12200
12200
Top Unit 4
12165.7
16600
17600
13600
13000
12902
12993
12491.6
12491.6
13086
12620.1 12600
13000
12800
12400
13400
12400
12453.6
12844 12800
12400
13200
COAL MEASURES
13532
1 3 7 3 0
12063.8
12000
17400 12200
TVD SS 0 GR_00J 140 45 CNL_00J -15 none none FEET GR_00J FDC_00J facies No fil No fil Plus Minus Plus Minus
Unit 3
12200
44/26-3 True Vertical Depth Sub Sea
TVD SS 0 GR_00J 140 none 0 FLOWUP 100 TVD SS none FEET FEET GR_00J facies No fil Plus Minus 12600
1 3 5 0 0
11800
1 3 5 0 0
17200
1 3 6 3 8 .8
1 5 0 0 0
16400 12000
1 5 0 0 6 .5 1 5 0 0 0
12000
1 3 0 7 5 1 3 0 0 0
1 9 0 0 0 1 8 0 0 0
TVD SS 0 CGR_01R 140 none 0 FLOWUP 100 MD KB none FEET FEET CGR_01R facies No fil Plus Minus
12600
1 3 2 5 6
17000
1 3 3 8 8
1 3 2 9 6 .9
1 4 0 9 6 1 4 2 5 4
1 4 5 0 0 1 4 6 8 6 .4
12000
1 4 7 7 5
1 3 0 7 5 1 3 0 0 0
16200
1 3 1 3 1 .5
12000
1 3 0 0 0 1 3 1 6 8 .1
1 3 0 7 5 .1 1 3 0 0 0
Top Unit 5
Saalian Unconformity
1 3 5 0 0
FWL
SA04/08 True Vertical Depth Sub Sea
SA01/03S1 True Vertical Depth Sub Sea
none MD KB none FEET facies 13000
1 3 0 7 5 .1 1 3 0 0 0 1 3 1 6 5
1 4 0 0 0
1 2 5 0 0
1 2 6 8 5 .3 1 2 7 8 9 .6
1 3 5 0 0
1 3 5 0 0
11800
1 4 5 0 0
1 3 9 4 3 .3
1 3 2 6 6 .1
1 4 4 2 3
FWL
Well G
FWL
TVD SS 0 GRS_00J 140 LDEN_01R FEET CNL_01R GRS_00J No fil No fil Plus Minus Plus Minus
1 3 6 9 5 .3
11800
16000
1 3 3 3 1
1 3 7 8 9
1 2 9 2 3 .8
1 4 0 0 0
1 3 0 7 5 .1 1 3 0 0 0
1 2 5 0 0
11800
1 2 6 8 7 .2
1 8 4 6 0 1 8 8 1 0 .4
1 3 0 0 0
1 3 0 0 0
1 2 5 0 0 1 3 6 1 3
1 2 7 9 4 .2
1 2 2 4 7 .2
1 1 7 7 7 7 9 9 1 0 .3 5 1 8 0 0 0
TVD SS 0 GR_00J 100 none MD KB none FEET FEET GR_00J facies No fil Plus Minus
1 7 5 0 0
1 3 0 0 0
1 8 5 0 0
1 2 8 4 7 .8
1 7 3 5 8 1 7 9 7 4 .1
1 3 0 7 5 1 3 0 0 0
1 2 6 5 3 .2 1 3 0 7 5 .1 1 3 0 0 0
1 2 7 7 3
1 2 5 0 0
1 2 5 0 0 1 2 6 8 0 .2
1 2 9 0 6 .2 3
TVD SS 0 GRIC_00J 80 none MD KB none FEET FEET GRIC_00J facies No fil Plus Minus
Well F
Unit 4
1 3 2 0 5 .1
1 2 5 0 0 1 7 0 0 0
1 2 5 0 0
1 6 9 7 8 .5 9
1 2 3 7 6 .5 8
1 2 4 3 8 7 .5 9
1 2 5 0 0
1 2 3 4 5 4 .9 3 2
1 2 5 0 0
SA02/05 True Vertical Depth Sub SeaFWL
Well E
Unit 5
1 2 7 7 6 .2 3
SA03/07 TVD SS
SA05/01 TVD SS
Coal Measures
FWL
Well D
BRA
1 3 0 7 5 .1 1 3 0 0 0
TVD SS 0 depthGR 140 45 CNL_00J -15 none MD KB none FEET FEET depthGR FDC_00J No fil No fil Plus Minus Plus Minus
SE
Well C
BRB
1 1 2 2 4 4 0 0 9 9 ..8 5 4
44/26-2 True Vertical Depth Sub Sea
COAL MEASURES
Well B
1 3 5 3 6 1 3 5 0 0
1 2 0 6 6 .7 1 2 0 0 0
1 7 5 0 0
1 6 5 0 0
Well A
1 2 1 2 1 .5
Saalian Unconformity
1 2 8 3 8
1 2 0 0 0 1 2 0 0 0
1 2 0 0 0
1 2 0 0 0
1 2 0 0 0
NW
BRC
1 2 4 4 9 .3
1 2 0 0 0
1 3 3 7 8
1 2 2 1 6
1 7 0 0 0
1 6 0 0 0
SE
44/26-3 True Vertical Depth Sub Sea
TVD SS 0 GR_00J 140 none 0 FLOWUP 100 MD KB none FEET FEET GR_00J facies No fil Plus Minus
1 2 7 6 2
Well D
SA03/07 TVD SS
TVD SS 0 GRIC_00J 80 none MD KB FEET GRIC_00J none FEET facies No fil Plus Minus
1 1 9 1 5
1 1 7 8 5 .1
Well C
SA05/01 TVD SS
TVD SS 0 depthGR 140 45 CNL_00J -15 none MD KB FEET depthGR FDC_00J none FEET No fil No fil Plus Minus Plus Minus
1 2 5 0 0
44/26-2 True Vertical Depth Sub Sea
TVD SS 0 GR_00J 140 45 CNL_00J -15 none MD KB FEET GR_00J FDC_00J none FEET No fil No fil Plus Minus Plus Minus SILVERPIT CLAYSTO
Well B
Well A
NW 44/26-4 True Vertical Depth Sub Sea
FWL
Slide 18
Challenge ■ Reservoir performance, connected HC, doesn’t seem to
honour the 1st correlation and related geological conceptual model. ■ The new, 2nd correlation and associated reservoir
connectivity, might be right but is largely inconsistent with 1st geological model. ■ How can we ensure the new correlation is right ?
■ No alternatives: Back to the rocks and give a better look also at the non-reservoir intervals. Slide 20
P edofacies types Type 1
Primary sedimentary structures (bedding, soft sed. deformation, etc..) preserved, no (or very rare) occurrence of bioturbation and/or rootlets. Some hematite nodules occur. Interpretation: high sedimentation rate and high aggradation; channel or frequently feed alluvial plain
Type 2
Primary sedimentary structures are preserved but can be locally disturbed by bioturbation or rootlets which make up 10-20 % of the fabric. Interpretation: moderate aggradation sediments Slide 21
Pedofacies types Type 3
Rare preservation of primary sedimentary structure up to 30-50% of fabric disturbed by bioturbation and rootlets. Interpretation: low aggradation sediments
Type 4
No primary structure preserved, original fabric completely churned up, heavy bioturbaion, ferriginous features (pisolites) and siderite nodules, salt (barite ?), pedorelicts. Interpretation: mature paleosoil, (ultisol, tropical podzol, calcrete) intense redox and illuviation processes, wet/dry cycles very low or absent aggradation rate (long sub-aerial exposure). Slide 22
Pedofacies at the microscope
Pedofacies 1: Undisturbed lamination picked out by aligned mica and hematite-rich clay
Pedofacies 3: Cluster of opaque nodules showing separation from the groundmass (outlines around grains); stress cutans also present
Pedofacies 2-3: Anisotropic, parallel alignment of clay minerals, also with a parallel extinction pattern; grain coatings present (arrowed)
Pedofacies 4: Multiple-stress cutans and Opaque clay filled fine brecciation
cracking, developing through soil fabric from larger cracks
Increased evidence of clay movement, the presence of better developed soil fabrics and an intimation of the existence of a soil structure in pedofacies 4
Slide 23
Pedofacies distribution on the Upper Carboniferous alluvial plain: Ketch Formation
Pedofacies 4
Pedofacies 3
Pedofacies 2
Pedofacies 1
levee
channel
water table
distal floodplain
proximal floodplain
Pedofacies models: M. Kraus et al… Slide 24
1 3
1
4
1
Pedofacies cyclicity
3 3
13500
1
4
4 3 1
4
3
2
3
4
13550
1 13600
2 2
1 1
4
1
13650
13700
2 4
1
13750
1 13800
13850
Slide 25
Pedofacies stratigraphy 2 3
Pedofacies
GR (API) 0
2
100
200
1
2
3
4
Thickness (ft) 0
5
10
15 20
1
pedofacies 2 type 1 2 1 2
13500
stratigraphic log
13600
13700
4 3 2 1
13800
13900
Slide 26
Recognition of Pedofacies in uncored wells Shear Sonic
Pedofacies type
(microsec/ft)
Feet AH
80
120
160
13500
13500
13550
13550
13600
13600
13650
13650
13700
13700
13750
13750
13800
13800
13850
13850
1
2
3
4
Correlation between shear sonic log and pedofacies from core data. Pedofacies 1 (i.e. nonpedogenised facies) to 4 (strongly pedogenised facies) indicate high and low sedimentary aggradation, respectively.
Slide 27
Well E 12800
Depth (ft, MDAH)
12900
Well G
GR (API)
Pedofacies
Thickness (ft)
50 150 250
1 2 3 4
0 5 10 15 20
5
0
12800
12900
13000
13000
13100
13100
13200
4
13300
13400
3
GR (API) 50 100
Pedofacies
Thickness (ft)
1 2 3 4
5 4
13200
13300
3
13400
2
Reservoir anatomy based on pedofacies vertical and lateral distribution Well G Well E
?
Upper Ketch Fm
13500
13600
2
13700
13800
1
13900
chemostratigraphic units
Pedofacies/ aggradation relationship 1: high 2: moderate 3: low 4: very low
Unit 4-5
Well A
Well G
Lower Ketch Fm Unit 1-2-3 channel
palaeosol
flood plain
(Moscariello, 2003)
Example of lateral correlation and pedofacies distribution for 2 wells in the Silver Pit Basin (Barren Red Measures, Westphalian C) Slide 28
Impact on Reservoir Prediction Sequence Stratigraphy old model Fluvial architecture
Relative change in base level, wetness and available accommodation space
Unit C Unit B Unit A
Slide 29
Sequence stratigraphy
Unit C
new model Fluvial architecture
Units 4,5
Unit B Unit A Lithostratigraphy
Units 1,2,3
Foreland subsidence
old model Fluvial architecture
Relative change in base level, wetness and available accommodation space
Chemostratigraphy & Pedofacies Slide 30
Impact on Reservoir Modeling and Field Performance Prediction
New Geological Conceptual Model
Alternative Reservoir Analogue (Keighley et al, 1998)
Reliable prediction capabilities
Revised aspect ratio
Update geo-cellular model Slide 31
Outline ■
Introduction
■
The Barren Red Measures Group: ■
■
The case study: Schooner and Ketch Fields SNS, UK ■ ■ ■ ■ ■
■
Palaeogeography, Stratigraphy Climate and Tectonic
Sedimentology First Lithostrat. Correlation & Conceptual geological model Field Performance Second Chemostrat Correlation and Paleosoils Impact of new integrated approach and results
Conclusions & Learnings Slide 32
Conclusions ■ Flood plain composition and vertical evolution in low
N:G systems are intimately linked to channel sand distribution and reservoir architecture ■ Use of multiple and independent approaches (N:G
distribution, pedofacies, chemostratigraphy) allowed us to: ■define an alternative evolutionary model of the sedimentary basin
which resulted to be more consistent with the regional tectonic evolution of the basin (sequence stratigraphy approach helps but is correlation driven !!) ■better constrain the static and dynamic model by using
appropriate analogue data (i.e. reservoir performance prediction). Slide 33
Learnings 1. Limitation of using lithostratigraphic subdivision based on wireline log in isolation. 2. Shear sonic together with GR can be successfully utilised to identify pedofacies vertical patterns in uncored wells. 3. Chemostratigraphy can be efficiently used as a tool to assist definition of a reliable correlation framework, hence connectivity. 4. Importance of palaeosoils/pedofacies in characterising internal reservoir architecture in low N:G, barren fluvial reservoirs also in the subsurface. Slide 34
THANK YOU
Slide 35
References Kraus, M.J., and T.M. Wells, 1999, Recognizing avulsion deposits in the ancient stratigraphic record, in Fluvial Sedimentology VI: International Association of Sedimentologists Special Publication, v. 28, p. 251-268. Kraus, M.J., and A. Aslan, 1993, Eocene hydromorphic paleosols: significance for interpreting ancient floodplain processes: Journal of Sedimentary Petrology, v. 63, p. 453-463. Krause, M.J., and D. M. Uhlir, 1989, Paleosols as exploration tool for fluvial reservoirs: AAPG Bulletin, v. 73/3, p. 374. AAPG Datapages. Web Accessed 30 March, 2009 http://search.datapages.com/data/bulletns/1988-89/data/pg/0073/0003/0350/0374c.htm Keighley, D., R.K. Pickerill, 1998, Mudstone-clastiform conglomerates and trough-shaped depressions from the Pennsylvanian Lower Port Hood formation of Eastern Canada: Occurrences due to soft-sediment deformation: Journal of Sedimentary Research, Section A: Sedimentary Petrology and Processes, V. 68/5, p. 901-912. AAPG Datapages. Web Accessed 30 March, 2009 http://search.datapages.com/data/sepm/journals/v66-67/data/068/068005/0901.HTM Moscariello, A., B. Besly, T.J. Pearce, S.B. Marriott, C.R. Hallsworth, A.C. Morton, and D. McLean, 2005, Fluvial architecture of complex low net: gross red-bed sequence, Upper Carboniferous, southern North Sea: 8th International Conference on Fluvial Sedimentology, Delft, Netherlands, 7-12 August 2005. Moscariello, A., 2003, The Schooner Field, blocks 44/26a, 43/30a, UK North Sea: Geological Society, London, Memoirs, v. 20, p. 811-824. DOI: 10.1144/GSL.MEM.2003.020.01.68 Moscariello, A., 2000, Pedofacies in reservoir modelling of low net to gross, barren fluvial sequences: Schooner Fm, Carboniferous SNS: Proceedings of the EAGE 62nd Conference and Technical Exhibition, Glasgow Scotland, 29 May – 2 June, 2000, X-10. Pearce, T.J., D.S. Wray, K.T. Ratcliffe, D.K. Wright, and A. Moscariello, 2005, Chemostratigraphy of the Upper Carboniferous Schooner Formation, southern North Sea, in Carboniferous hydrocarbon geology, the southern North Sea and surrounding onshore areas: Yorkshire Geological Society Occasional Publication, v. 7, p. 147–164.
Pearce, T.J., D. McLean, D.S. Wray, D.K. Wright, C.V. Jeans, and E.W. Mearns, 2005, Stratigraphy of the Upper Carboniferous Schooner Formation, southern North Sea: chemostratigraphy, mineralogy, palynology, and Sm-Nd isotope analysis, in Carboniferous hydrocarbon geology, the southern North Sea and surrounding onshore areas: Yorkshire Geological Society Occasional Publication, v. 7, p. 165–182. Stone, G., and A. Moscariello, 1999, Integrated Modelling of the Southern North Sea carboniferous barren red measures using production data, geochemistry and pedofacies cyclocity: Offshore Europe, v. 99, 7-10 Sept 1999, Aberdeen Scotland, SPE 56898, 8 p.
