Transcript Slide 1
Whitings – Source of
Black Gold?
-
UAE Algal mats & lime muds
A link to Middle East carbonate source rock
potential
C.G.St.C. Kendall, Xavier Jenson &
Eugene Shinn
Departments of Geological Sciences, University of South Carolina,
Jackson School of Geology, University of Texas Austin,
and Marine Science Center, University of South Florida
Outline of Presentation
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The Hypothesis
Overview of Arabian Gulf Reserves
Geological setting of Arabian Gulf
Modern lime mud & cyanobacteria generation of
Arabian Gulf
Bahamian Whitings Productivity, Sequestration &
Organic Matter
Geological setting of Arabian Gulf Oil Fields & tie
of hydrocarbon sequestered cyanobacterial
remains in geologic section
Significance of Russian source rock study
Conclusions
Hypothesis
• Significant Holocene accumulations of
cyanobacteria & lime mud in Arabian Gulf axis & tidal
zones
• These sediments have source rock potential
• Similar sediments have accumulated since Triassic
• Ancient carbonate muds are source of significant
petroleum reserves of Arabian Gulf region
• The present is the key to the past!
Current Middle East Reserves
Crude Oil(BB) - Natural Gas (TCF)
•Saudi Arabia
•Iraq
•UAE
•Kuwait
•Iran
•Oman
•Yemen
•Qatar
•Syria
•Bahrain
•TOTAL
263.5 bbls 204.5 Tcf – 8 Years
112 bbls 109 Tcf
97.8bbls 212 Tcf
96.5 bbls 52.7Tcf
89.7 bbls 812.3Tcf
5.3 bbls 28.4 Tcf
4.0 bbls 16.9 Tcf
3.7 bbls
300.0 Tcf
2.5 bbls 8.5 Tcf
0.1 bbls
3.9 Tcf
675.1 bbls 1,748.2 Tcf
MIDDLE EAST FIELDS
Location of
Middle
Eastern Oil
Fields
Oil Production - Arabian Gulf
Productive hydrocarbon section older to West
[Paleozoic] & younger at Arabian Gulf Coast [Mesozoic]
& youngest in East in Zagros Mts [ Upper Tertiary].
West to East production includes:
•Infra-Cambrian Salt
•Silurian and Ordovician clastics – Unaizah
•Permian clastics & carbonates – Khuff
•Upper Jurassic Carbonates - Arab & Tuwaik Mt Grp
•Lwr Cretaceous Carbonates – Shuaiba & Thammama
•Middle Cretaceous – Mishrif
•Tertiary - Asmari
Mesozoic through Tertiary-Lime Mud Source
Proposed Concept
• Arabian Gulf Holocene cyanobacteria & mud
accumulations significant in axis & tidal zones
• These sediments have source rocks potential
• 4000 meters of similar sediments have
accumulated here since Triassic
• Sequestered ancient carbonate muds are
source of the significant petroleum reserves
of Arabian Gulf region
• The present is the key to the past!
Structural Provinces - Arabian Gulf
Mesozoic to Tertiary
Foreland Basin
4,000 meters of
Mesozoic to Tertiary
Sediment sequestered
NASA Image
in Foreland Basin!
Analysis of Crude Oils find
Alkanes & Isoprenoids
• The alkane/acyclic isoprenoid fraction is the
main constituent of most crude oils
• A large number of crude oils and rock extracts
from Timan-Pechora basin (Russia) suggest
this fraction is direct product of liquefaction of
biological debris preserved essentially
unaltered till oil generation.
• Result is the primary biological provenance of
this fraction is preserved in the oil fraction.
Hydrocarbon Source
• Collister, Ehrlich, Mango, & Johnson (AAPG, 2004) propose
primary organic materials convert to oil as dispersed
alkanes & isoprenoids in rocks
• Low TOC source or undermature rocks generate significant
oil if source carries sufficient special kerogen derived
from biological membranes is unchanged till liquefaction
• Observations & experiments, mostly French labs, show
resistant organic membranes in form of biopolymers play
this role.
• Stable over a large range of conditions, survive early
secondary bacterial attack & late-stage breakdown with
increasing thermal stress.
Evidence
• Significant Holocene accumulations of
cyanobacteria & lime mud in Arabian Gulf axis & tidal
zones
• These sediments have source rocks potential
• Similar sediments have accumulated since Triassic
• Ancient carbonate muds are source of significant
petroleum reserves of Arabian Gulf region
• The present is the key to the past!
Carbonate Provinces - Arabian Gulf
Ramp
Open
Shelf
Basin
Restricted
Shelf
Satellite scenes SW, to West coast of
Arabian Gulf 12 July 2006, MODIS Rapid
Response system site, Nasa
http://rapidfire.sci.gsfc.nasa.gov
Dust and Whiting response
Weather Station Data
Temperatures - pink & MPH windspeed - black.
Windspeeds over 25mph coincide with regional "Whiting" blooms.
Arabian Gulf
Factory producing
carbonates & storing
products of cyanobacteria
since Permian
NASA Image
A big day for a bloom!!
Organics in the Gulf!
Nasa Image
Whitings common to-day
and common back in the
Triassic!
Organics in the Gulf!
Nasa Image
Wells and Illling - 1965
• Among 1st to report ” Whitings” offshore from
Qatar precipitated in Persian Gulf.
• Ascribed whitings to CO2 removal by
photosynthesis of phytoplankton.
• Groot (1964) lab analysis of suspended
sediment offshore was 70% Aragonite, 10%
Calcite, 15% Mg Calcite, 5% Quartz & 5%
Dolomites.
• Lab experiments used NaCO3 to remove CO2
pptated aragonite from Gulf, but rates did not
match instantaneous formation of “Whitings” but
took 2 to three weeks.
NASA satellite scene with very localized
& diminished ‘Whitings’ off UAE on Pearl
Bank, offshore East Qatar, north flank of
Bahrain shoal, and offshore from
Saudi/Kuwaiti border
Local Whiting Occurrences!
PG Gulf
Major Source
Direct
Precipitation
Persian Gulf Facies Distribution
After Wilkinson & Drummond, 2004
Persian Gulf Mud Distribution
After Wilkinson & Drummond, 2004
Lime Mud Sequestered in Basin Axis
& Tidal Flats
The mud probably forms less than 1% of sediment signal since
Mesozoic but forms a formidable source for hydrocarbons of Gulf
Facies of UAE
Lime muds
& organics
sequestered
in axial trough
& tidal flats
Axial
Muds
Skeletal
Sands
Reefs &
Coralgal
Sands
Ooid
Tidal Deltas
Coastal
Sabkha
Cyanobacterial mats
Lime mud
& organics
sequestered
in Mangrove
swamp
tidal flats
Shoaling Upward Inner Shelf Cycle
Shoaling Up
Cycle
Abu Dhabi – Mud Flats
Abu Dhabi – Mud Flats
High Intertidal
Cyanobacterial
Flats
Earlier High
Energy Beaches
Supratidal
Sabkha
Evaporites
Intertidal
Carbonate
Flats
Tidal Ponds
Tidal Pond
SURFACE
ANHYDRITE
POLYGONS
HALITE POLYGONS
MICROTOME OF
CYANOBACTERIAL
MATS
Modern Sources of lime mud
• Isolated seas – Arabian Gulf
• Wide platforms in nutrient deserts of
tropical seas – Bahamas
Bahamian Organic Productivity
• Whitings precipitate 1.35 metric tons per year
• 25% of Whiting is organic matter – mostly
cyanobacteria and microalgae
• As much as 1.6% of surface sediment may
contain organic matter
• Subsurface sediments preserve 1% TOC (up to
4%)
• 7Be (half-life 53 days) found in Whitings but
absent in resuspended bottom sediment
Bahamas Ocean Drilling Transect
Kramer, Swart, DeCarlo & Schosvbo, 2005
Modern Sources of lime mud
• Isolated seas – Arabian Gulf
• Wide platforms in nutrient deserts of
tropical seas – Bahamas
LIME MUD
ACCUMULATES
ON BANK, OFF BANK
& TIDAL FLATS
Aragonite Needles
2.5mm Long
& 0.25 mm Wide
MAJOR SOURCE
OF LIME MUD IN
BAHAMAS IS
WHITINGS!
Sequestration in Downslope wedge
Sequestration on Tidal Flat
Bahamas – shoals source of mud
Rates of Accumulation
• Short-lived isotopes determin accumulation rates
(Shinn et al., 2000).
• Samples analyzed within 20 days of collection using
high-resolution gamma ray spectrometer for shortlived isotopes Be-7 & Th-234 with respective half lives
of approx. 53 & 23 days.
• Active billowing Whitings had Be-7 & Th 234 but
bottom sediment depleted.
• None of bottom sediment stirred by storms contained
short-lived isotopes.
• Radiogenic elements adsorbed on sediment surface,
or if epitaxial growth occurred, these short-lived
isotopes would be present.
Bahamian Whitings Instant Precipitates
• Whitings vivid white while water outside them is clear!
• Instantaneous chemical &/or biochemical aragonite precipitates.
• Many Whitings drift back & forth with tides over time continually
raining sediment to bottom with no documented dispersal or end.
• Wane in intensity at slack tide to strengthen when tide reverses.
• Cloud (1961) followed a single Whiting for 48 hours while Shinn et
al. (1989) followed Whitings for 24 hrs.
• Some persisted for 24 hrs over hard pellet sands with no mud
stirred into suspension. Shinn et al. (1989) returned to same
Whitings still drifting over pellet sand 2 days later & Robbins et al.
(1997) documented persistence from satellite images.
• Artificial Whitings of stirred up bottom settled within 6 hours
• Nearby natural Whitings persisted and did not dissipate
• Whiting water pumped to settling tanks aboard boat settled in 6
hrs.
Whiting Mud Sequestration
• Hurricanes & winter storms export vast quantities of lime mud over bank edge.
• 7 weeks after Hurricane Andrew (1992), lime mud collected as layers up to 5 cm
thick over shallow ooid sands near bank edge (Shinn et al., 1993). Layers from
slurries of lime mud exiting bank to Florida Straits & Tongue of Ocean.
• An up to 90m thick wedge of Holocene sediment at base of Bahama Bank slope
(Wilber et al.,1990) represents 40 to 80% by volume of mud presently
sequestered for entire bank.
• Vertical and lateral progradation rate of wedge is 11-15 m/ka and 80-110 m/ka,
respectively (Wilber et al., 1990). Measures amount accumulated during last 68 ka and does not consider Whiting mud carried northward in Gulf Stream to
distant locations and/or to dissolution.
• Ball et al. (1967) and Perkins and Enos (1968) report significant off-bank
sediment transport in Florida following Hurricanes Donna and Betsy. Similar
observations made and photographed in Florida by Shinn following Hurricane
Andrew in 1992.
• Lime mud-laden sediment continues to spill off the platform for weeks
following a hurricane. The Bahamian Bank has been submerged for the past 68 ka and is affected by a hurricane every 6 to 10 years. Overproduction,
possibly far greater than 280%, is necessary to account for what is presently
on the bank.
Organic Matter
• Phytoplankton nucleae are cores to cells
• Viable phytoplankton cyanobacterial cells in Whitings not observed
in bottom sediment - deteriorate quickly after deposition (Robbins
and Blackwelder, 1992) .
• Aragonite needles adher to surface of living planktonic
cyanobacteria indicates rapid precipitation within water column
(Robbins & Blackwelder, 1992; Yates & Robbins, 1998; 1999; 2001).
• 25% of the 1.3 million metric tons ppted & suspended each year in
Bahamas is organic matter, dropping to 1.8% of surface sediment. .
• Bahamian Bank Whitings & associated organic matter cover more
limited areas swept off bank into deep water. Cores through Neogene
western platform slope sediments preserve 1% TOC up to 4% (Kramer,
Swart.
Bahamas
Morphology
Rim
Restricted
Shelf
Basin
Open
Shelf
Carbonate Mud Settings
• Carbonate muds common through earth history
• Carbonates signaled by thick sections adjacent
to margins of recently pulled apart continental
plates &/or in compressional terrains of colliding
margins
• Carbonate muds collect in:
– Lower portions of updip shallow water cycles
– Lower portions of downdip restricted basins &
basin slopes
Organic matter <1%
weight of Holocene
tidal flats &
axial trough !
Carbonate Mud Accumulation Sites
of Ancient Arabian
• Late Paleozoic to Early Mesozoic behind
Structural & Depositional Barriers
• Punctuated by limited access to sea &
repeated arid climatic events favoring
cyanobacterial preservation
• Now trapped beneath Arabian Gulf
Hydrocarbon Source, Seal, Reservoir
• Source Rocks
– Permian Khuff - Saudi Arabia
– Lw Jurassic Tuwaiq Mt. Group - Saudi Arabia
– Lw Cretaceous Maudud Fm. of UAE
• Seals
– Usually with playa and sabkha evaporites
• Reservoirs
–
–
–
–
–
Deep Ghawar
Berri, Ghawar
Zakum Field, UAE Thamama I, II, and III, Shaybah
Mishrif
Asmari
Arabian Gulf Basin
Traces complex history of plate tectonic & sedimentary fill:
•Pre Cambrian to Infra-Cambrian - Continental interior
•Silurian and Ordovician clastics – Continental interior
•Permian clastics & carbonates – Trailing margin
•Upper Jurassic carbonates – Trailing margin
•Lower Cretaceous carbonates – Trailing margin
•Middle Cretaceous – Compression & Zagros Mts initiated
•Tertiary carbonates & clastics - Compressional margin
Evolution of Arabian Gulf
Foreland Basin
Compression &
Foreland Basin
Extensional margin
Extensional margin
Interior Sag
After Kingston et al, 1983
Hydrocarbon
Production
in
Arabian plate
Stratigraphic
section
Section
represents approx
2,438.5m in 200 my
Accumulation
Rate 1.22 mm per 1 Ky
Lime
Source
PERMIAN KHUFF FM DEPOSITIONAL SETTNG (Al-Jallal, 1995)
Restricted
Entrance
To Sea
Permian Khuff
Saudi Arabia
Oman & UAE
Structural &
Depositional
Barrier over
Hercynian
Horst Blocks
Arid Tropics Air System
Wide Shadow from Adjacent Continents
% WORLD’S SOURCE ROCKS
Carbonate
Mud
Source
Rocks
After Baum, & Kendall
Geological Setting of Jurassic Oil
Seal
Seal
Reservoir
Reservoir
Intrashelf
Basin
Intrashelf
Basin
Lime
Source
GOTNIAN DEPOSITIONAL SETTING (Al-Sharhan & Kendall, 1986)
Lime
Source
Restricted
Entrance
To Sea
Upper Jurassic
Saudi Arabia
Kuwait, Iran
& UAE
Depositional
Barrier over
Hercynian
Horst Blocks
Tropical Air System !
Wide Shadow from Adjacent Continents
After Dennis Tassa
Zagros Fold Mountains - Iran
NASA Image
Lower Cretaceous
Stratigraphic cross-section of Cretaceous
Eastern Arabia (Alsharhan & Nairn 1986)
Tertiary
Lime
Source
Stratigraphic cross-section of Neogene
Arabian Gulf (Alsharhan & Nairn 1986)
From International Petroleum Encyclopedia
Lime
Source
ORGANIC MATTER HYPOTHESIS
• The Arabian Gulf a sink of organic matter since Triassic
• As with modern Gulf much of this organic matter related to
multiple organic blooms through geological time
• Organic matter trapped in intertidal flat & basinal muds
• Dispersed organic matter in form of biological membranes,
have simple chemical composition & structure, & so liquefy
at a threshold temperature & do not require time &
temperature history for maturation.
• A burst of oil generation produces transient overpressures
resulting in liberation of oil by microfracturing and longrange migration through the resulting fractures.
• This ensures that large volumes of oil could be generated
over a short time.
CONCLUSIONS
• Arabian Gulf Holocene cyanobacteria & mud
accumulations significant in axis & tidal zones
• These sediments have source rocks potential
• Similar sediments accumulated since Triassic
• These ancient carbonate muds are source of
the significant petroleum reserves of Arabian
Gulf region
• The present is the key to the past!
Now to
lunch!
West of Dhabaiya – Mangrove Swamp
Holocene tidal flats
are sequestering >1%
of weight as organic matter!
Bahamas
Deep water
of
marginal
zone
Shallow
tidal flats
Bahamas
Bahamas
Mud
transported
by
hurricanes
settle
in high
energy
channels
Bahamas – Shoals are a
source of mud!
Bahamas – shoals source of mud
Bahamas – shoals source
of mud
Bahamas – shoals source of mud
Bahamas – shoals source
of mud
Bahamas – shoals source
of mud
Bahamas – shoals source of mud
Bahamas – shoals source of mud
Bahamas – shoals source of mud
Bahamas – shoals source of mud
Appalachians
Ordovician Isolated Foreland Basin
Appalachians
Ordovician
Appalachians - Ordovician
Appalachians - Ordovician
Appalachians - Ordovician
Appalachians - Ordovician
Appalachians - Ordovician
Appalachians Ordovician
Appalachians - Ordovician
Appalachians - Ordovician
deepening up from
grains to mud
Appalachians Ordovician
Appalachians
Ordovician
Murray Basin
Murray Basin
Lime muds
& organics
sequestered
in axial trough
& tidal flats
Pellets &
Grapestones
Skeletal
Sands
Ooid
Tidal Deltas
Reefs &
Coralgal
Sands
Coastal
Sabkha
Cyanobacterial
mats
Cyanobacterial
mats
Lime mud
& organics
sequestered
in Mangrove
swamp
tidal flats
Intertidal Sand
& Mud Flats
Tidal Channels
Cyanobacterial
Mats
Sabkha
Geologic Cross-Section - Arabian Gulf
Gas
Paleozoic
Stratigraphic
Column
Arabia
Gas
Lime
Source