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Modules
with Guided Exercises
The
modules below are tied to lectures, movies and exercises that
can be accessed from this web site and used for academic and
educational purposes. They have been organized so the user can
start with little understanding of sequence stratigraphy but
through systematically following the modules in order can improve
vocabulary, understanding and experience. Initial materials
and exercises are introductory in character but as one moves
through the modules, their materials become more sophisticated
and challenging. Once the modules have been completed you should
have a good understanding of sequence stratigraphy and should
be able to use well, seismic and outcrop data to make mature
interpretations of the sedimentary sections you might study.
An additional intent of the web site is that it becomes a ready
reference to the complex world of sequence stratigraphy!!
Click
on the highlighted short cut to the listing of printable exercise
images and exercise solutions should you need them quickly
but if you want to know more about the exercises the best path
to retrieve them from are the modules listed below.
Rational
for Sequence Stratigraphic Exercises
Earth scientists
involved with reservoir characterization and hydrocarbon
exploration in carbonate and/or clastic lithofacies use
sequence stratigraphy to construct better reservoir models
and predict hydrocarbon plays more accurately. This technique,
combined with seismic and well log interpretation, make
the models built by reservoir geologists more accurate and
reduces the risk associated with reserve estimation and
secondary production.
Without the application
of sequence stratigraphy to carbonate and/or clastic reservoirs,
the interpretation of seismic and well data can be flawed.
This is because the thickness of the reservoir interval
is often below the vertical resolution of the seismic wavelet
and the lateral continuity of the reservoirs lithologic
layers tied between wells is often below the horizontal
resolution of the well logs. Sequence stratigraphy provides
a logical framework of layers in which bounding and internal
surfaces and lithologies are tied to depositional models
that presuppose the lateral continuity of lithologies, their
reservoir character and their relationship to relative seal
level. Thus predictions of lateral and vertical reservoir
properties have their risk reduced when sequence stratigraphy
is applied to interpreted seismic and well data.
This framework
of layers, coupled to their character and origin is at the
heart of reservoir modeling. The identification of the appropriate
layering geometry is crucial to the construction of 3D static
reservoir model and one must take care not to apply the
rules of sequence stratigraphy by rote without necessarily
understanding them. The ensuing stratigraphic grid becomes
the template for distribution of clastic and/or carbonate
facies, their diagenetic alterations, their associated petrophysical
properties, and final input for flow simulation. Poor clastic
and/or carbonate models are often the result of misunderstanding
of the rules and terminology of sequence stratigraphy as
well as the principles and workflows for building stochastic
models.
The above rational
provides the major reasons that exercises below should help
those who build reservoir models. The exercises should clarify
the rules of sequence stratigraphy for clastic and/or carbonate
settings. The medium of this site with its exercises, lectures,
and descriptive text can be used to retrieve critical reservoir
sequence stratigraphic models for professionals while teaching
principles of sequence stratigraphy based reservoir characterization
to novitiates. The accompanying text on the site ties relevant
data including images, text links, and movies of sedimentary
simulations.
Concepts
that may be learnt from the Exercises
In the exercises
below you will learn how:
• Sequence stratigraphy subdivides the sedimentary
section into geometric packages bounded by unconformities
and internal surfaces
• Sedimentary geometries are related to changes in
base level (sea level and/or tectonic movement) and rates
of sedimentation
• To predict the extent and character of these sedimentary
geometries
• Sequence stratigraphy is a powerful geological tool
that has economic implications in that it can be used to
make predictions as to the extent and character of the rocks
containing hydrocarbon and water resources
The exercises demonstrate how the above inferences and sequence
stratigraphic analyses is largely based on the interpretation
of
• Seismic cross-sections
• Well logs
• Outcrop studies of sedimentary rocks and are used
to predict the continuity and extent of their lithology.
The exercises show how
• Seismic cross-sections can provide regional control
on the geometries of sequences
• Well logs can be used to determine the lithology of
these geometries
• Outcrop studies provide an even more detailed understanding
of the lithology of these geometries.
• The best of interpretations are preferably made with
a tie between local outcrops, local wells and local seismic.
• If one or two of these data sources are missing the
resulting models may be diminished by their absence.
The exercises using seismic cross-section display how
• To determine the sequence stratigraphy of a basin
from discontinuity surfaces that coincide with seismic reflector
terminations
• Those surfaces that form the sequence boundaries are
correlated
• The enveloped system tracts are correlated
• Both sequence boundaries and system tracts are traced
from line to line to establish the sedimentary architecture
of the basin and infer the origins of the system tracts
• Clinoform geometries can be used to show evidence
of delta switching, slumping and migration and related to
the shifting of the source areas
• The effects of variable rates of sediment supply in
the area of study can be examined
• To determine evidence for widespread changes in base
level
• To locate basin floor fans, slope fans and incised
valleys and find evidence to demonstrate that these latter
were produced during changes in base level
The exercises using well log character show how well logs
can be used to:
• Correlate parasequence sets at the scale of feet to
tens of feet
• Determine the depositional setting of the component
system tracts
• Determine the sequence stratigraphy of the section
being studied
• Parasequences are identified and correlated from well
log character, particularly when planktonic or palynologic
biostratigrapic markers are restricted to only a few vertically
dispersed shale horizons
• The resulting parasequences are often at the same
scale as the components of local hydrocarbon reservoirs
• Find, map and exploit these reservoirs more effectively
by relating them to eustatic events
The exercises using outcrops indicate how:
• Outcrops are the ultimate ground truth to the correlation
of parasequences
• Major surfaces that include transgressive surfaces
(TS), maximum flooding surfaces (mfs), and sequence boundaries
(SB) facilitate this process.
• Stacking patterns of parasequences help determine
the continuity of the reservoir quality & depositional
setting of the sediments they bound.
• The high-frequency "cycle" or "parasequence"
is the smallest set of genetically related facies deposited
during a single base-level cycle.
• Cycle boundaries mark the turnaround from base-level
fall to base-level rise (a period of time during which sea
level rises from a highstand position, through a lowstand,
and returns to a highstand).
• Cycles can be mapped across multiple facies tracts
and include multiple vertical facies successions (VFS) and
chronostratigraphic units (Kerans & Tinker, 1997 and Mitchum
& Van Wagoner, 1991).
• The commonest parasequence is the shoaling upward
cycle, with finer deeper water facies at their base and coarser
better-sorted facies towards their top.
• Parasequence sets identified in outcrop can be used
to identify potential acquifers, aquicludes, hydrocarbon source
rocks, reservoirs and seals.
1•
Introduction
to sequence stratigraphy: the critical stratigraphic
surfaces used sequence
stratigraphy with their relationship to the exercises
briefly outlined.
2•
Basics:
introduction to sequence stratigraphy with a Real Time
lecture describing the ideal ‘sequence' of Vail et al
1977 and its associated terminology.
3•
Clastic Sequence Hierachies:
uses a movie to show the clastic sedimentary response
to changing sea level and rates of sedimentation focusing
on the hierachies of geometry found in clastic sequences.
4•
Carbonate
Sequence Hierachies: examines the hierarchy of scales expressed by carbonate
strata and provides movies that track the fill of basins
and shelves by carbonate sediment.
5•
Mixed
Carbonate & Clastic Basin: a movie of the fill of a sided sedimentary basin with
carbonate and clastic sediment reviewed.
Exercises
Chronostratigraphy
1•
Exercise
1 - Chronostratigraphy: construction
of a chronostratigraphic chart with the support of a movie
that tracks an evolving chronostratigraphic chart and the
fill of the associated sedimentary basin.
Seismic
Sequence Stratigraphy
a) Objectives
& Data: seismic used to determine the geometric
relationship of sequences, delta migration, local and regional
tectonics, and the eustatic signal.
b) Geological
Setting: Colville "foreland" Basin initiated in the
Jurassic and filled by prograding clinoforms of siliciclastics
through the Cretaceous and Tertiary.
c) Class
Answer - Sequence
Stratigraphy of Lower Cretaceous:
slow and constant rate of subsidence with a steady inflow
of clastics responding to second and third order eustatic
signals in the Cretaceous section with localized higher-frequency
(4th order?) events related to delta migration.
a) Objectives
& Data: carbonate sequence stratigraphy of the
shelf, reef crest, slope and down slope basin floor fans
related to local changes in base level and the Haq et al
(1987) sea level chart.
b) Seismic
Line: Cretaceous and Tertiary carbonate sediments
of the western Great Bahamas Bank reflect the effects of
changes in sea level.
c) Class
Answer – The tie of Sequence Stratigraphy
of the Neogene Section to Eustasy:
A slow and constant rate of subsidence, and steady flux
of carbonates sediments onto the Great Bahamas Bank caused
a close balance between aggradation and progradation, while
small changes in the rate of relative sea level movement
and/or carbonate accumulation causing immediate switches
from aggradation to progradation at the margin.
Outcrop
Sequence Stratigraphy - Gateway
Outcrop
Sequence Stratigraphy - Clastics
Outcrop
Sequence Stratigraphy - Carbonates
Well
Log Sequence Stratigraphy - General Preamble
1•
Introduction
to Sequence Stratigraphy with Well Logs: the first steps in the use of well logs to build sequences
stratigraphic models of depositional system.
2•
Well
Log Suites: brief description of how different types of well log
are used to interpret sedimentary geology.
3•
Well
Log Response Character: explanation of the use of the shapes of well log curves
to track changes in mineral content, and grain size and
so interpret sedimentary geology.
4•
Well
Log Stacking Patterns: explanation of how aggradational, retrogradational and
progradational stacking patterns identified on well logs
can be used to interpret sedimentary depositional settings.
Well
Log Sequence Stratigraphy - Clastic High-Frequency Signals
1•
The
Geologic setting of the La Pascua Formation - Guarico
Sub-Basin: general geological setting of
the nearshore clastics of the Lower Oligocene La Pascua
Formation of the Las Mercedes Field in the West Guarico
Block, Venezuela, their lithology, relationship to sea
level and plate tectonic setting.
2• Introduction
to Sequence Stratigraphy of the La Pascua Formation -
Guarico Sub-Basin: first steps in the use of well logs to build sequences
stratigraphic models of clastic shoreline depositional
systems for the Lower Oligocene La Pascua Formation of
the Las Mercedes Field in the West Guarico Block, Venezuela.
3• Exercise
1 - Well log correlation using SP & RES logs:
interpretation of local north eastern Venezuelan clastic
stratigraphy using three wells (W-1, W-2, W-3) that penetrate
the Lower Oligocene La Pascua Formation of the Las Mercedes
Field in the West Guarico Block.
4•
Exercise
2 - Well log correlation using SP & RES logs:
interpretation of local north eastern Venezuelan stratigraphy
and identification of a clastic sequence in an incised
valley using 10 wells (W-1 to W-10) that penetrate the
Lower Oligocene La Pascua Formation of the Las Mercedes
Field in the West Guarico Block.
5•
Exercise
3 - Well log correlation using SP & RES logs:
interpretation of local north eastern Venezuelan stratigraphy
and identification of a clastic sequence of an incised
valley, and its relationship to sea level from 22 wells
(W-1 - W-22) that penetrate in the Lower Oligocene La
Pascua Formation of the Las Mercedes Field in the West
Guarico Block.
6•
Exercise
4 - Well log correlation using SP
& RES logs: interpretation of local north eastern Venezuelan stratigraphy
and identification of a clastic sequence of an incised
valley, and its relationship to sea level from 5 Wells
(me333, me296, me428,
me313 and me 486) within
the central portion of the Northern Strike Line that penetrate
in the Lower Oligocene La Pascua Formation of the Las
Mercedes Field in the West Guarico Block.
7•
Exercise
5 - Well log correlation using SP & RES logs:
interpretation of local north eastern Venezuelan stratigraphy
and identification of the clastic coastal and incised
valley sequences, and their relationship to sea level
from wells that penetrate in the Lower Oligocene La Pascua
Formation of the Las Mercedes Field in the West Guarico
Block on a North-South Dip line , a Northern Strike Line
and a Southern Strike Line.
8•
Solutions
for Exercise 1, 2, 3, 4 and 5: interpretation
of well log cross-sections of coastal sedimentation and
incised valley fill explained with a movie of the evolving
clastic sequences.
9•
References:
References for the interpretation of Well logs and References
for the Guarico Sub-Basin geological framework and regional
stratigraphy.
Core&
Well Log Sequence Stratigraphy - Carbonate High Frequency
Signals
1)
Introduction
to high frequency carbonate sequence stratigraphy:
an explanation of why cycles and parasequences are used
to study ancient carbonate systems
2)
Exercises
that introduce high frequency carbonate sequence stratigraphy
with an "hypothetical" example:
Introduction to use of well log interpretation of carbonates
using awell-log section across the imaginary Ordovician
carbonate margin of the "Beltzaren
Lurraldean Field in NW Syldavia"
(After Hergé 1939)
Exercise
1
Introduction to parasequence identification using well
logs to identify the major stratigraphic surfaces and
cycle (and/or parasequence) stacking patterns tied from
well to well.
Exercise 2
Well logs correlated using a combination of well logs
and cores to identify the major stratigraphic surfaces
and cycle (and/or parasequence) stacking patterns that
are tied from well to well.
Under
Development) EXERCISE:- Well log section
of Upper Jurassic of the "Pearl
Banks offshore Abu Dhabi Basin"
(After xxx & xxx, 2002)
Exercise 1
Introduction to parasequence identification on the basis
eight well logs to identify the major stratigraphic surfaces
and cycle (and/or parasequence) stacking patterns tied
from well to well.
Exercise 2
Eight well logs correlated using a combination of well
logs, seismic and strontium isotope ages to identify the
geometry of major stratigraphic surfaces and cycle (and/or
parasequence) stacking patterns that are tied from well
to well.
EXERCISE:-
A well log cross-section across the margin of "NE
shelf of the Delaware Basin of the Permian Basin"
in New Mexico and the NW flank of the Central Basin Platform
(After Harris & Saller 1999).
Exercise 1
Introduction to cycle (and/or parasequence) identification
on the basis well logs to identify the major stratigraphic
surfaces and cycle (and/or parasequence) stacking patterns
tied from well to well.
Exercise 2
Well logs correlated using a combination of well logs
and seismic tied to synthetic to identify the geometry
of major stratigraphic surfaces and cycle (and/or parasequence)
stacking patterns that are tied from well to well.
Exercise
3
Fill in details of lithofaceis on partly interpreted well
log section with information gleaned from interpreted
seismic and establish cycle (and/or parasequence) stacking
patterns that are tied from well to well.
3)
Correlation
of cycles and/or parasequences; cycles and/or parasequence
sets; and systems tracts in the Hanifa
Formation: based on stacking patterns
& log character. A description of the surfaces that
bound and subdivide parasequences and how they are identified
on well logs. How to construct Fischer Diagrams.
Exercise
1
Introduction to parasequence identification on the basis
of the lithologies within cored wells. Well # 1 penetrates
a shallow shelf region and Well # 2 a deeper region.
Exercise
2
Four well logs correlated using a combination of well
logs and cores to identify the major stratigraphic surfaces
and parasequence stacking patterns that are tied from
well to well.
Exercise
3
The use of 14 (Fourteen) well logs to make a regional
sequence stratigraphic interpretation of facies geometries
by identifying major surfaces, establishing the lithofacies,
building a Fisher diagram.
Exercise
4
Improve high frequency cycle correlation using the Fischer
Diagram.
References
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