University of King
Abdulaziz
Faculty
of Earth Sciences
Department
of Petroleum Geology and Sedimentology
Final second Term Exam (1430/2009): (445GX) (sequence
stratigraphy and basin analysis)
Date of Exam. …/06/1430 (……day) ………. morning
I. Define the following: (12 marks)
1. Incinced Valley
2. Parasequence
3. Sequence Boundary (SB)
4. Depositional sequence
5. Sequence
stratigraphy
6. Systems Tracts
II.
Complete the following: (30 marks)
1. Parasequence stacking pattern are ………………….……………………..
and
…………………………………………...
2. Parasequence types include are …………………………………, and……...
…………………….. .
3. The main types of systems tracts are ………………………….,
……………
…………
,…………………….., …………………… and ………………….
4. The main bodies of lowstand systems tracts are
……………….., ………….
…………………,
…………………, ….………… and ……………………..
5. Condensed section is ……………………………………………………….
6. The sedimentary basin is …………………………………………………….
…………………………………………………………………………………
………………………………………………………………………………..
7. Basin components include ……………, …………………, …………….
………………………,……………………………,…………………………. ………………………, …………………………and ……………………….
8. The main basins controls are
………………………, ……………………
……………………………………….and ……………….............................
9. Upstream in the sequence
stratigraphy of the fluvial systems include .
……………………,
………………………, …………………………….,
…………………………………., and
…………………………………
10.
Down stream in the sequence
stratigraphy of the fluvial systems
include…………………………………., and …………………………
11. flooding surfaces include ……………………. and …………………….
12. The sequence stratigraphic approach in the seismic stratigraphy is based
on …………………………………………………………………
13 Types of sequence boundaries are ………., and …...…..
14. The main carbonate
depositional environments according to settings,
supply and climate are ………………..,
………………………………,
…………………………...,
…………………………., …………………..
………………, and
……………………………………………………..
15. The main controls of carbonate deposition are ………………………,
…………………………., ……………………………..,
………………..
……………….., ……………………………..,
…………………………,
and
………………………………………………………………..
III. Write the terminology of numbers for each of the following models:
(33 marks)
1.
Components on the EXON model for sequence stratigraphy
2. Seismic bed forms beside.
3. Components of the
depositional sequence.
4. Components of the following sequence model.
5. Components of the following
sequence model.
6. Write the components of the
following sequence model.
7. Components of the following
seismic sequence.
8. Components of Peter Vail
and Robert Mitchum seismic sequence model.
9. Stacking
pattern for the following parasequence sets.
IV.
Draw only Sketch for the following: 15 marks)
1. Stages of Rift Formation.
2. Compare between rift basins and
passive margins.
3. Sub-duction related basin.
4. The passive margin basins.
5.
The transform fault (pull apart) basins.
V. Write
short note on the Stratigraphic Control on Oil and Gas Accumulations in Saudi Arabia. (10 marks)
University of King
Abdulaziz
Faculty
of Earth Sciences
Department
of Petroleum Geology and Sedimentology
Final second Term Exam (1430/2009): (445GX) (sequence
stratigraphy and basin analysis)
Date of Exam. …/06/1430 (……day) ………. morning
III. Define the following:
1. Define the Incinced
Valley
Incised valleys are entrenched fluvial systems extending their
channels basinward and eroding into underlying strata in response to a relative
fall in sea-level.
2. Define the Parasequence
Relatively conformable depositional units bounded by
surfaces of marine flooding, surfaces that separate
older strata from younger and show an increase in water depth in
successively younger strata. Relatively conformable (that is,
containing no major unconformities), genetically related succession of beds or
bedsets bounded by marine-flooding surfaces or their correlative surfaces.
3. Define Sequence
Boundary (SB)
The sequence boundary
is an unconformity updip and a correlative conformity downdip.
4. Define the depositional sequence
Stratigraphic unit bounded at its top and base by
unconformities or their correlative conformities, and typically embodies a
continuum of depositional environments, from updip (continental) to downdip
(deep marine).
5. Define Sequence
stratigraphy
A framework of
genetically related stratigraphic facies geometries and their bounding surfaces
used to determine depositional setting in terms of time and space.
6. Define the Systems Tracts
Subdivisions of
sequences that consist of discrete depositional units that differ in geometry
from other systems tracts and have distinct boundaries on seismic data. Different systems tracts are
considered to represent different phases of eustatic changes.
IV.
Complete the following
1. Parasequence stacking pattern are ………………….……………………..
and …………………………………………...
progradational stacking, aggradational Stacking,
retrogradational stacking
patterns
2. Parasequence types include are …………………………………, and……...
…………………….. .
Coarsening
(swallowing) upward, and fining (deepening) upward parasequences
3. The main types of systems tracts are ………………………….,
……………
…………
,…………………….., …………………… and ………………….
Falling Stage Systems Tract (FSST) , Lowstand Systems Tract (LST), Transgressive Systems Tract
(TST), Highstand Systems Tract (HST), and
Regressive System Tract (RFST).
4. The main bodies of lowstand systems tracts are
……………….., ………….
…………………,
…………………, ….………… and ……………………..
Lowstand fans,
basin floor fans, lowstand wedge, mid fans and distal fans
5. Condensed section is ……………………………………………………….
A thin marine stratigraphic
interval characterized by very slow depositional rates (<1-10 mm/yr).
6. Define the sedimentary basin.
A geologically depressed area with thick
sediments (sedimentary rocks) in the interior and thinner sediments at the
edges. A depression, created as a consequence of subsidence, that fills with
sediments.
7. Basin components include ……………, …………………, …………….
………………………,……………………………,…………………………. ………………………, …………………………and ……………………….
Backarc basins, Forearc basins, passive
margin basins, Epicontinental basins, Extensional basins, subduction realated
basins, rift basins, foreland basins (peripheral) and transform
fault (pull apart) basins.
8. The main basins controls are
………………………, ……………………
……………………………………….and ……………….............................
sediment supply, regional tectonics, sea
level changes and climate
9. Upstream
in the sequence stratigraphy of the fluvial systems include .
……………………, ………………………, …………………………….,
…………………………………., and
…………………………………
Climatic discharge,
geology load, tectonic tilting, faulting and drainage basin.
10.
Down stream in the sequence
stratigraphy of the fluvial systems include…………………………………., and …………………………
Eustasy and
subsidence rate.
11. flooding surfaces include …………………….
and …………………….
trangressive surfaces [ts] and maximum flooding surfaces [mfs]
12. The sequence stratigraphic approach
in the seismic stratigraphy is based on …………………………………………………………………
recognition of unconformity-bound sequences
using geometry and termination patterns of seismic reflectors which follow time
surfaces rather than facies impedance boundaries.
13 Types of sequence boundaries are
………., and …...…..
Type-1 sequence boundary and Type-2 sequence
boundary
14. The main carbonate depositional environments according to settings,
supply
and climate are ………………..,
………………………………,
…………………………...,
…………………………., …………………..
………………,
and ……………………………………………………..
Humid carbonate rimed shelves, Humid carbonate-siliciclastic rimed
shelves, Arid carbonate-evaporite-siliciclastic rimed shelves, Detached humid
rimed platforms, Humid carbonate ramp and Arid carbonate-evaporite-siliciclastic
ramp.
15. The main controls of carbonate
deposition are ………………………,
…………………………., ……………………………..,
………………..
……………….., ……………………………..,
…………………………,
and
………………………………………………………………..
Carbonate factory (Organic and Inorganic
carbonate production), Highstand shedding, Carbonate platform drawning,
Sea-level changes, Continental terrestrial supply, Tectonics
(uplift/subsidence), Oxic/ anoxic water conditions.
III. Write the terminology of numbers for each of the following model:
3.
Components on the EXON model for sequence stratigraphy.
2. Seismic bed forms beside.
3. Components of the depositional
sequence.
4. Components of the following
sequence model.
5. Components of the following
sequence model.
6. Write the components of the following
sequence model.
7. Components of the following
seismic sequence.
8. Components of Peter Vail and Robert Mitchum seismic
sequence model.
9. Stacking pattern for the following
parasequence sets.
V.
Draw only Sketch for the following:
2. Stages of Rift Formation.
2. Compare between rift basins and passive margins.
3. Sub-duction related basin.
4..
The passive margin basins.
5.
The transform fault (pull apart) basins.
54.
Write short note on the Stratigraphic Control on Oil and Gas Accumulations
in Saudi Arabia
1. Thickness of Sedimentary Sequence:
In Saudi Arabia
the thickness of sedimentary section ranges from 4500 m to 14,000 m. General
trend of thickening away from the interior homocline, in both NE and E. The
possibility for oil and gas discovery seems remote where the sequence is less
than 3500 m thick.
2. Reservoir Rocks:
The sedimentary
sequence of Saudi Arabia
characterized by the presence of multiple, stacked reservoirs characterized by
well-sorted, medium to coarse-grained calcareous or arenaceous sands. These
reservoir rocks are present mainly in the upper Paleozoic and Mesozoic part of the stratigraphic section.
They characterized by effective porosity and excellent permeability, and some
time secondary porosity. Example of reservoir rocks is the sand-size carbonate
grainstones and dolomites of Arab-D reservoir. This reservoir is best developed
where calcarenite is greater than 25%. Other examples Arab-C, Wasia Group,
Unayzah and Khuff Formation.
3. Source Rocks:
Example of the source
rocks for oil in the upper Jurassic reservoirs of Arab Formation are the source
facies dark gray to black, organic rich, carbonate silts of the Tuwaiq Mountain
and Hanifa Formations, where oil generated and has migrated upwards through
fractures in 300 m tight carbonates and passed around the evaporate caprocks of
the Arab members to be most completely sealed by thick anhydrites of Hith
Formation.
Oil within the upper
Fadhili reservoir, below the Tuwaiq Mountain Formation may have migrated down,
while oil of Middle Jurassic Lower Fadhili, Sharar and Faridah may have been
derived from source rocks within the more argillaceous Lower Dhruma Formation.
Source rocks for the
Middle Cretaceous reservoirs are proposed to have originated in Jurassic source
rocks and to have migrated vertically along fractures.
Although the possible
source rocks for Jurassic and Middle Cretaceous rocks of Arabia
can be explained, it is more difficult to explain the huge gas reserves and oil
contained in the Permian Khuff and Dalan Formations. Because these Formations
rest on a widespread unconformity with truncated older Paleozoic beds below.
However the Berwath Formation Shales are possibly the source-rock and also the
dark Shales within Jouf Formation. Moreover the Silurian Shales such as Qusaiba
shale may be of regional significance as source rocks in the Arabian
Peninsula.
4. Seals or Cap rocks:
The presence of
impermeable seals is very important. The most significant of these seals
are:the extensive, evaporates of the Hith anhydrite at the top of the
upper Jurassic. It serves as a seal to the underlying, Arab formation
carbonates. Anhydrites within the Jilh Formation n subsurface act as the seal
for gas at ain Dar and to the west of the Summan Plateau.
Shales seals
are also great important especially with regard to the Mid-Cretaceous Wasia
Group. In Kuwait
the very permeable Burgan sandstone reservoir is capped by a thin seal of
Ahmadi shale. The same situation is present in the supergiant Safaniyah and
Khafji fields. Interlayer dense carbonates, limestone, Also act to form
seals as in the almost continuous ascending limestone sequence from the top of
Marrat Formation through the Dhurma and Jubila Formations.
5. Dolomitization
Usually
dolomitization associated with volume reduction which increases the porosity
and Permeability. But some time dolomitiztion of carbonate grains may continue
without leaching, so that an interlocking crystal develops and forming
impermeable seal. Example of such is in Khuff Formation where, cap of gas
reservoirs in both Bahrain
and Dammam Dome is present with some anhydrites.
Pressure solution
surfaces or stylolites. They reduce and tight intervals between
porous. Example of such seal is present
in Thamama Group limestone (Abu Dhabi) and may
be Shaybah (Saudi Arabia).
Tar seals are
unusual in Saudi Arabia.
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