A micropalaeontological biofacies analysis of the Lower Cretaceous and latest Jurassic in Kuwait : the Ratawi, Minagish and Makhul formations.

1. Results: Biofacies – Outer Ramp (deep water carbonate setting)
Textularinids
Cyclamminids
Everticyclamminasp.
Pseudocyclammina
Rotaliids
Agglutinants
Miliolids
Cuneolina
Nautiloculina
Charentiaspp
Trocholina
Neotrocholinaspp
Bramkampella
Praechrysalidina
Ammobaculites
Chofatella
Pfenderinaspp
Nezzazatinellids
Orbitolinopsis(conicalagglut)
Lenticulinaspp
Undiffforaminifera
Planktonicforaminifera
Rudists
Corals
Stromatoporoids
Molluscs
Gastropods
Bivalves
Ostracods
Brachiopods
GreenAlgae
Lithocodium
Bacinella
Oncoids
Codiaceans
Dasyclads
Echinoderms
Bryozoans
Serpulids
SpongeSpicules
Calpionellids
Calcispheres
VeryShallow
Shallow
Innerramp
Corefacies
Microfacies(Wilson1975)
Mudstone
Wackestone
Packstone
Grainstone
Boundstone
Floatstone
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R R VR C M C R C C M
A M M R A M M C P
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M R C? M R C C M VR VR W/P
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M M R? M C A M C R W
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M R C M R C VR? M
M R? R R M M
C R R M C M VR C M
M VR? R? VR C C R R M M
C M M VR M VR R R M M
C VR R C M
C R VR M R C M M9702.10 R
9472.40
9475.00
9659.70
9668.20
9686.70
9371.50
9379.30
9382.70
9389.30
9406.00
9419.00
9432.00
9435.00
9450.50
Minagish
9066.90
9096.40
9153.50
9157.80
9175.70
9184.20
9299.10
Middleramp
9306.70
9314.40
9322.10
9334.80
9338.50
9368.90
9190.90
9202.50
9205.00
9241.50
9250.50
9277.60
9289.70
9462.30
DistalOffshore(Basinal)
Facies TS Textures (Dunham)
TS Depth
ME-01 Core Thin Section Bio-components Inner Ramp
DistalOuterRamp
ProximalOuterRamp
A/C
Micriticpeloids
M
R
R
R
R
R
Results: eg. Biostratigraphy Models
Preliminary Biofacies studies of
the Ratawi, Minagish and
Makhul formations, Kuwait
Stephen Crittenden and Maha Al-Baghli
Introduction
The Tithonian stage of the Late Jurassic with the Berriasian and
Valanginian stages of the Lower Cretaceous in Kuwait comprise a
proven hydrocarbon bearing interval.(Ref. 1)
• Producing hydrocarbons in Kuwait since mid-20th Century.
• Fields are „giants‟ and include Minagish Field (1958/9) (Ref. 2), Uum Gudair
Field (1962) (Ref. 3) and Wafra Field (1953). (Ref. 4)
• Large structural 4-way closure Traps at multiple stratigraphical levels. (Ref.
5)
• Predominantly shallow marine platform carbonate reservoirs (Ref. 1, 2 & 3)with
minor clastic reservoirs – secondary (eg. Sabriyah Field).(Ref. 5)
• Three conventional lithostratigraphical units: Ratawi, Minagish and Makhul
formations. (Ref. 6)
• Hydrocarbon shows in the three formations regionally in Kuwait. (Ref. 5)
OBJECTIVE: Evaluate lithostratigraphy and biostratigraphy
data. Establish a predictive Holistic Stratigraphy framework (eg.
Ref. 7 & 8)
useful in the subtle trap exploration play concept.
A: Biostratigraphical / Biofacies Data
Source and collect existing “in-house” well & outcrop data.
Search published literature. (eg. Ref. 1)
Evaluate existing Lithostratigraphy, Biostratigraphy,
Chronostratigraphy data and frameworks.(eg. Ref. 9)
Generate new data: biostratigraphy, biofacies, sedimentology,
lithofacies, petrography.(eg. Ref. 10)
Evaluate, Integrate & Interpret all data sets.
B: Holostratigraphy
Develop a Biostratigraphy and Chronostratigraphical Model.
Establish age-dating of the reservoirs and formations.
Calibrate to regional chronostratigraphy – time lines.
Palaeoenvironment of reservoirs and formations.
Develop a Depositional Sequence Stratigraphy Model.
Correlate wells (iterative process).
Prediction of potential Source and Reservoir intervals.
Selected References
1. Al-Fares, A. A., M. Bouman and P. Jeans, 1998, A new Look at the Middle-Lower Cretaceous Stratigraphy, Offshore Kuwait. GeoArabia, v. 3, pp. 543 -
560.
2. Youash, Y. Y. & Mukhopadhyay, A., 1982, Geology of Minagish Oil Field, Kuwait. AAPG 66 (5), pp. 645.
3. Davies, R., Hollis, C., Bishop, C., Gaur, R. & Aziz Haider, A., 2000. Reservoir geology of the Middle Minagish Member (Minagish Oolite), Umm Gudair
Field, Kuwait. In: Middle East Models of Jurassic / Cretaceous Carbonate Systems. SEPM Special Publication No. 69, pp. 273 – 286.
4. Longacre. S. A. and Ginger, E. P. 1988. Evolution of the Lower Cretaceous Ratawi Oolite reservoir Wafra Field, Kuwait-Saudi Arabia Partitioned
neutral Zone. in Lomando, A., and Harris, P. M., eds., Giant Oil and Gas fields: SEPM, Core Workshop 12, pp. 273-331.
5. Carman, G., 1996. Structural elements of Kuwait. GeoArabia, v.1, pp. 239 – 266.
6. Owen, R. M. S. & Nasr, S. N. 1958. The Stratigraphy of the Kuwait- Basra area. In: Habitat of Oil, AAPG Memoir, 1252 – 1278.
7. Sharland, P., et al. 2001. Arabian Plate Sequence Stratigraphy. GeoArabia Spec Publ. 2
8. Davies, R. B., Casey, D. M., Horbury, A. D., Sharland, P. R. and Simmons, M. D. 2002. Early to Mid Cretaceous mixed carbonate-siliciclastic shelfal
systems: Examples, issues and models from the Arabian Plate. GeoArabia, v. 7, 3, pp. 541-598.
9. Al-Rifay, I. A. & Lemone, D. 1987. Calpionellids and the late Jurassic and early Cretaceous stratigraphy of Kuwait and the Gulf Region. Marine
Micropalaeontology, 12, pp. 383-388.
10. Banner, F. T. and Simmons, M. D. 1994. Calcareous algae and foraminifera as water – depth indicators: an example from the Early Cretaceous
carbonates of northeast Arabia. In Simmons, M. D. (ed.). Micropalaeontology and Hydrocarbon Exploration in the Middle East. British
Micropalaeontology Society Publication Series. pp. 243 – 252.
11. Al-Husseini, M. & Matthews, R. K., 2008. Jurassic-Cretaceous Arabian orbital stratigraphy: The AROS-JK Chart. GeoArabia, v. 13, pp. 89 – 94.
12. Hughes, G. W. G. 2005. Calcareous Algae of Saudi Arabian Permian to Cretaceous Carbonates. Rev. Esp. de Micropal. V. 37, 1 pp. 131-140.
13. Sharland , P., et al. 2004. Chrono-Sequence Stratigraphy of the Arabian Plate. GeoArabia, v 9, 1, Enclosure 1.
Acknowledgments: This poster is presented with the
approval of the Ministry of Oil of the state of Kuwait and the
Kuwait Oil Company. The encouragement, assistance and
advice is acknowledged of all members of the Exploration
Studies Team of KOC. Some primary data has been gleaned
from proprietary “vintage” service company reports held in
the archives of KOC authored by: Dr Osman Varol, Dr Peter
Morris, Dr Mike Simmons, Fugro Robertson, Halliburton,
Corelab , Weatherford and Badley Ashton.
Concluding Remarks
The keys to well based sequence stratigraphy
modelling for exploration are:
• A robust biostratigraphical model generated from
integrated well data sets.
• Evaluate “old” biostratigraphical data gives value.
• Biostratigraphical control and identification of time
lines eg. FS, = Chronostratigraphy.
• Beware of “shoe-horning” data to fit a preconceived
model. A model is a guide only.
• The ”holistic approach” to stratigraphy has a
predictive use for exploring new play concepts.
• Data from High Resolution Field Reservoir case
studies contribute to development of a regional well-
based predictive sequence stratigraphy.
Results:
• provide an enhanced understanding of the
distribution of Lowermost Cretaceous reservoir
potential lithologies eg. Shoal barriers.
• add value to an exploration strategy seeking the
subtle stratigraphical trap - Risk Reduction.
This poster introduces some initial results from a
biostratigraphical methodology that embraces well
material generated data (both vintage and new) and
models, to assist in evaluating the prospectivity of the
lowermost Lower Cretaceous in Kuwait.
Materials and Method
Results:Biofacies–Inner Ramp shoal & Outer Ramp(eg. Ref.10)
Results: Biostratigraphy - Biofacies
Haq *
Sharland et
al
2005 2004
139ma 136ma K30 Valanginian
141ma 138ma K20 Berriasian
144ma 143ma K10 Berriasian
147ma 147ma J110 Tithonian
* calibrated to GTS of Gradstein et al 2004
MegasequenceAP8
Intra Ratawi Lst
Intra Minagish Lst
Intra Makhul Fm
Intra Lower Makhul
Late Jurassic Unconformity (SB 149.0 Ma)
3rd Order MFS Position
Sharland et al 2004Stage
Major
MFS
Late Valanginian Unconformity
EARLYCRETACEOUSEPOCH
STAGE
LITHOLOGY
Middle-Late
Tithonian
Berriasian
Berriasian-
Valanginian
Early
Valang-
inian
Stratigraphy and simplified lithology of the Makhul, Minagish and
Ratawi formations
Group
Formation
Member
LATE
JURASSIC
RatawiLstRatawiSh.
Carbonates
with
grainstone
shoals
Muddy
carbonates
Transitional
evaporites
THAMAMA(pars)
MAKHULMINAGISHRATAWI
SHAQRA
(pars)
HITH
EAGE 2nd Exploration Workshop, Cairo. Dec 2010.
EXPO419
3rd Order Maximum Flooding Scheme for the latest
Jurassic - earliest Cretaceous (Ref. 7)
Lowermost Cretaceous Conventional Stratigraphy Model (Ref. 6)
?? Possible 3rd Order Flooding Event, perhaps
equivalent to K20 fs of Sharland et al., 2001, 2004.
Difficult to reconcile due to lack of / or sparse, age
diagnostic fossils.
Cyclical deposition in a relatively deep water distal part of a large carbonate ramp during an
overall transgressive to highstand sea-level. These cycles are interpreted as high order changes in
relative sea level that in a more proximal situation may result in greater lithological diversity eg.
“oolitic / grainstone” shoals.
Outer ramp, 25 – 70m water
depth indicator
Common Lithocodium 10 –
30m water depth indicator.
(Ref. 12)
Calpionellids: characterise deep water, low
energy environment. Mostly within
argillaceous rich, laminated calcareous
mudstones and wackstones. Proximal and
distal outer ramp setting. These pelagic,
calcareous unicellular organisms are studied
in thin section hence re-study of
petrographical thin sections provides good
data. They are however prone to diagenetic
obliteration and reworking (in clasts).
Chronostratigraphy: Integrated Biostratigraphy uses all available data from all groups
studied: eg. calcareous nannofossils, dinoflagellate cysts, spores and pollen,
calpionellids, radiolaria, ostracods, calcareous algae and foraminifera. All have been
used to date the well sections, either in isolation or in an integrated fashion depending
on data available. The proviso is that all are facies dependent / controlled – diachronous
nature of local stratigraphical ranges within a shallow marine environment, and a
detailed high resolution chronostratigraphic biozonation is not possible.
9454 ft FDO Abundant Calpionellids, plus
Calpionella alpina
Candidate high order SB from core at top of cleaning-up cycles
The model acts as a broad guide. Observed data
should not be “shoe-horned” to fit the model. The
biostratigraphical data should be used to modify the
model if necessary.
Well F (Ref. 1) Calc Nanno
FloodingsurfacesasinterpretedbySharlandetal.2004
Surfacesfrom“in-house‟KOCdata
?
PS = Polycostella senaria 13360ft
A maximum flooding based stratigraphy of Sharland et al indicates four
3rd order depositional sequences within the 2nd order sequence
(duration 16 my). Evaluation of data indicates up to six 3rd order
depositional sequences may be present as implied by AROS (Ref. 11).
Maximum flooding “intervals”: either deeper water outer shelf shales
or shallow water limestones.
Well F is in an outer ramp deep water carbonate setting. The Minagish
Formation is developed as non-reservoir facies.
2ndOrderSequence
Calcareous nannoplankton: Due to shallow water
palaeoenvironments and post depositional diagenesis, nannofossil
assemblages in samples from the studied wells are of low
abundance, low diversity and usually poorly preserved. Many of
the expected stratigraphical marker species commonly reported in
deep-sea sediments of Lower Cretaceous age are absent or only
occur sporadically. Semi-quantitative analysis provides a means
for assisting in the identification of marine flooding intervals –
floral acme / abundance.
FDO (extinction) of Polycostella senaria: is it a correlatable Time-
event (local extinction level) in shallow water shelf carbonates? PS
Results:Palaeoenvironment Models
Major SB
Major SB
A
?
?
B
Polycostella senaria 9064ft
PS
PS
PS
Microfossils and biofacies
associations for the Makhul,
Minagish and Ratawi formations
indicate depositional environments
ranging from shallow marine to
deeper shelf / basin. An
environmental history for the
carbonate deposition can be
determined that can help assist i)
the resolution of layering /
stratigraphical tiering in a
reservoir and ii) regional
correlation. Some biota events are
interpreted as transgressive pulses
that may equate to time lines.
These constrain the reservoir
lithofacies sequence stratigraphy
interpretation.
Integrated Biostratigraphical Model - numerous fossil groups.
Diachronous stratigraphical ranges of key taxa in shallow marine
carbonates – environmental control.
Biofacies from prepared Petrographic thin sections.
Correlate wells (iterative process).
? Palaeogeographical Mapping.
Identification of potential Source and Reservoir intervals.
Offshore Kuwait
Minagish Fm as non reservoir facies
Minagish Fm as Oolitic / grainstone shoal reservoir facies
Well B Well A
Exploration Play Concept.
The depositional regime for
prospective reservoir
development is the shoal
barrier environment of the inner
ramp in well B.
South Kuwait