Omar Akbar…..2005Omar Akbar…..2005
Thesis CommitteeThesis Committee
Mostofa Sarwar ..Laura Serpa ...Matthew Totten ..
AgendaAgenda
IntroductionIntroduction Location Deposition Thesis Objective Thesis Significance
MethodologyMethodology
Data AnalysisData Analysis Observations Hypothesis
ResultsResults Structural Interpretation Stratigraphical Interpretation Result Comparison
ConclusionConclusion
LouisianaLouisiana
Introduction: Introduction: LocationLocation
GB -191GB -191
Gulf of Mexico 160 miles Gulf of Mexico 160 miles
southwest of Lafayettesouthwest of Lafayette
Water depth of 700 ftWater depth of 700 ft
Between Texas-Louisiana Between Texas-Louisiana
outer shelf and Texas-outer shelf and Texas-
Louisiana upper slopeLouisiana upper slope
Garden Bank, block number Garden Bank, block number
191191
Introduction: Introduction: DepositionDeposition
Two Pleistocene sands (4500-ft Two Pleistocene sands (4500-ft and 8500-ft) were deposited and 8500-ft) were deposited during relatively regressive sea during relatively regressive sea levellevel
The Sands were transported to The Sands were transported to the area from some deltas to the area from some deltas to the north of GB-191the north of GB-191
These shelf edge deltas are 10-These shelf edge deltas are 10-15 miles to the north of GB-191 15 miles to the north of GB-191 ((West Cameron 638 and 643West Cameron 638 and 643))
(Fugitt et. al., 2000)
Introduction: Introduction: Thesis ObjectiveThesis Objective
The objective of this thesis is to study the 4500-ft
and 8500-ft sands accumulations in GB-191, and to
examine how they were impacted by salt tectonics. I
believe that this study would lead to a better
understanding of hydrocarbon traps by integrating
both geological and geophysical data within the area.
Some results this thesis will be presented as time and
amplitude maps. Also, this thesis will reconstruct a
wave-theoretical model that describes sand
accumulation and its relationship to salt evolution.
Introduction: Introduction: Thesis SignificanceThesis Significance
Provide comprehensive analysis of the Pleistocene Provide comprehensive analysis of the Pleistocene sands depositionsands deposition
Provide clues to potential prospects and leads in the Provide clues to potential prospects and leads in the areaarea
Maintain the seed interpretation Maintain the seed interpretation seismic attribute seismic attribute analysis, quality enhancement and time to depth conversionanalysis, quality enhancement and time to depth conversion
Offer an integrated data set in format ready to be used Offer an integrated data set in format ready to be used under the GeoFrame environmentunder the GeoFrame environment
Provide a knowledge database posted on the Provide a knowledge database posted on the supervisor’s webpage supervisor’s webpage ((area history, geological area history, geological interpretation, previous studies, well information, and interpretation, previous studies, well information, and production historyproduction history)) Such information is essential for any similar Such information is essential for any similar study in the futurestudy in the future
Enrich our understanding of GB191 geological historyEnrich our understanding of GB191 geological history
Methodology: Methodology: StepsSteps
Study and Evaluation of the AreaStudy and Evaluation of the Area
Data CollectionData Collection
Geological InterpretationGeological Interpretation Data PreparationData Preparation Log CorrelationLog Correlation Map GenerationMap Generation
Geophysical InterpretationGeophysical Interpretation Geological & Geophysical Data IntegrationGeological & Geophysical Data Integration Salt Diapir PickingSalt Diapir Picking Major Fault PickingMajor Fault Picking Major Sands PickingMajor Sands Picking Fault Boundary CreationFault Boundary Creation Final Map GenerationFinal Map Generation Amplitude Anomaly Map GenerationAmplitude Anomaly Map Generation
Methodology: Methodology: DataData
3D Seismic data in time domain3D Seismic data in time domain
Sonic, density, resistivity, spontaneous Sonic, density, resistivity, spontaneous potential (SP) and gamma ray (GR) well logspotential (SP) and gamma ray (GR) well logs
Well coordinatesWell coordinates
Well headers (total depth, water depth, run Well headers (total depth, water depth, run date, kelly bushing and well status).date, kelly bushing and well status).
Paleo-reports and perforated intervals.Paleo-reports and perforated intervals.
Directional survey points.Directional survey points.
Velocity surveys.Velocity surveys.
Wells productions.Wells productions.
Data AnalysisData Analysis
SomeSome times are needed to set aside and times are needed to set aside and
scroll through the seismic in vertical and scroll through the seismic in vertical and
horizontal orientation in order to get a sense horizontal orientation in order to get a sense
of which direction the structures are trending of which direction the structures are trending
and where future interpretation problem and where future interpretation problem
areas may exist areas may exist
ObservationsObservations HypothesisHypothesis InterpretationInterpretation
Data Analysis: Data Analysis: ObservationsObservations
Xline 600Horizontal Scale: 1:30,000 Vertical Scale: 2.5 in/sec
GB-191GB-191
Show strata dipping to Show strata dipping to the north. the north.
Strata are expected to Strata are expected to be deposited during the be deposited during the Cenozoic era on Cenozoic era on southward dipping southward dipping slope. slope.
Clear on X-lines to the Clear on X-lines to the left side of the block. left side of the block.
Data Analysis: Data Analysis: ObservationsObservations
Inline 111023Horizontal Scale: 1:60,000 Vertical Scale: 2.5 in/sec
GB-191GB-191
Differences Differences in tectonic in tectonic activity activity applied on applied on each side of each side of the salt. the salt.
SaltSalt
Asymmetric Asymmetric structure structure ((steep Vs. steep Vs. gentlegentle).).
Data Analysis: Data Analysis: ObservationsObservations
Inline 111023Horizontal Scale: 1:60,000 Vertical Scale: 2.5 in/sec
GB-191GB-191
SaltSalt
Data Analysis: Data Analysis: ObservationsObservations
Inline 111023Horizontal Scale: 1:60,000 Vertical Scale: 2.5 in/sec
GB-191GB-191
Faults Faults facilitated the facilitated the movement movement and put extra and put extra pressure on pressure on the left flankthe left flank
SaltSalt
Left beds were Left beds were uplifted and uplifted and rotated due to rotated due to salt diapirismsalt diapirism
Data Analysis: Data Analysis: ObservationsObservations
Inline 111023Horizontal Scale: 1:60,000 Vertical Scale: 2.5 in/sec
GB-191GB-191
A major A major normal fault normal fault played a played a significant significant role in role in triggering and triggering and controlling controlling the shape of the shape of the salt the salt structure. structure.
This major This major fault bounded fault bounded the right side the right side of the of the upgoing salt upgoing salt body.body.
SaltSalt
Data Analysis: Data Analysis: ObservationsObservations
Inline 111023Horizontal Scale: 1:60,000 Vertical Scale: 2.5 in/sec
GB-191GB-191
Evidences Evidences show show sediments sediments continuity in continuity in prediapiric prediapiric areaarea
8500’ Sand
4500’ Sand
Dating 4500-Dating 4500-ft and 8500-ft ft and 8500-ft sands relative sands relative to salt to salt diapirism is diapirism is important important
Data Analysis: Data Analysis: HypothesisHypothesis
Imaginary DatumImaginary Datum
PleistocenePleistocene SandsSands
SaltSalt
Imaginary DatumImaginary Datum
SaltSalt
Data Analysis: Data Analysis: HypothesisHypothesis
Pleistocene SandsPleistocene Sands A major normal fault played a A major normal fault played a significant role in triggering significant role in triggering and/or facilitating the movement and/or facilitating the movement
The 4500-ft and 8500-ft sands The 4500-ft and 8500-ft sands are prediapiric; deposited prior to are prediapiric; deposited prior to salt evolutionsalt evolution
Data Analysis: Data Analysis: HypothesisHypothesis
A major normal fault played a A major normal fault played a significant role in triggering significant role in triggering and/or facilitating the movement and/or facilitating the movement
Imaginary DatumImaginary Datum
PleistocenePleistocene SandsSands
MigrationMigration
The 4500-ft and 8500-ft sands The 4500-ft and 8500-ft sands are prediapiric; deposited prior to are prediapiric; deposited prior to salt evolutionsalt evolution
The major fault caused a The major fault caused a differential pressure within differential pressure within salt sheet. salt sheet.
SaltSalt
Structural depression on the Structural depression on the downthrown drove salt to migrate downthrown drove salt to migrate upwardupward
Data Analysis: Data Analysis: HypothesisHypothesis
Sediments overlaying salt to the Sediments overlaying salt to the left side of the bounding fault left side of the bounding fault were uplifted and rotated were uplifted and rotated
Imaginary DatumImaginary Datum
SaltSalt
Pleistocene
Pleistocene
SandsSands
Imaginary DatumImaginary Datum
SaltSaltPleisto
cene
Pleistocene
SandsSands
Secondary faults influenced Secondary faults influenced the salt formation; caused the salt formation; caused pressure gradient over salt left pressure gradient over salt left flank. flank.
Sediments, however, to the Sediments, however, to the right moved downward as right moved downward as salt was withdrawn from salt was withdrawn from beneath (beneath (asymmetric asymmetric structurestructure).).
Results: Results: Structural Interpretation Structural Interpretation
Salt Salt DiapirDiapir
FaultsFaults
Results: Results: Structural Interpretation Structural Interpretation
Salt Salt DiapirDiapir
FaultsFaults
Results: Results: Structural Interpretation Structural Interpretation
Salt Salt DiapirDiapir
FaultsFaults
Results: Results: Structural Interpretation Structural Interpretation
Salt Salt DiapirDiapir
FaultsFaults
In-line 111013 Horizontal Scale: 1:60,000 Vertical Scale: 2.5 in/sec.
Time MapTime Map
Results: Results: Stratigraphical InterpretationStratigraphical Interpretation
4500-ft4500-ft
8500-ft8500-ft
Results: Results: Stratigraphical InterpretationStratigraphical Interpretation
4500-ft4500-ft
8500-ft8500-ft
Amplitude MapAmplitude Map
Results: Results: Stratigraphical InterpretationStratigraphical Interpretation
4500-ft4500-ft
8500-ft8500-ft
Depth Map (4500-1)Depth Map (4500-1)
-5152
-4847
-4694
-4471
A5
A6
A9
A10
GB191
2000’
-4500
0’
-5000
NN
-4500-5000
Results: Results: Stratigraphical InterpretationStratigraphical Interpretation
4500-ft4500-ft
8500-ft8500-ft
Geophysical Vs. Geological InterpretationGeophysical Vs. Geological Interpretation
-5152
-4847
-4694
-4471
A5
A6
A9
A10
GB191
2000’
-4500
0’
-5000
NN
-4500
-5000
Results: Results: Stratigraphical InterpretationStratigraphical Interpretation
4500-ft4500-ft
8500-ft8500-ft
Time MapTime Map
Results: Results: Stratigraphical InterpretationStratigraphical Interpretation
4500-ft4500-ft
8500-ft8500-ft
Amplitude MapAmplitude Map
Results: Results: Stratigraphical InterpretationStratigraphical Interpretation
4500-ft4500-ft
8500-ft8500-ft
Depth MapDepth Map
-9252-8678
-8181
-900
0
-800
0
A2ST1A4
A7
GB191
4000’
NN
0’
Results: Results: Stratigraphical InterpretationStratigraphical Interpretation
4500-ft4500-ft
8500-ft8500-ft
Geophysical Vs. Geological InterpretationGeophysical Vs. Geological Interpretation
-9252-8678
-8181
-900
0
-800
0
A2ST1 A4
A7
GB191
4000’
NN
0’
There is only one published interpretations for GB-191.There is only one published interpretations for GB-191.
The interpretations were published in SEG, The The interpretations were published in SEG, The Leading Edge April 2000. Leading Edge April 2000.
The study was done by Chevron group The study was done by Chevron group (Fugitt, et. al., (Fugitt, et. al.,
2000)2000). .
Results ComparisonResults Comparison
This thesis study differs than Chevron This thesis study differs than Chevron work by paying more attention to salt work by paying more attention to salt evolution in the area. The influence of evolution in the area. The influence of salt dynamics on overlaying beds and salt dynamics on overlaying beds and their direct relationship with the fault their direct relationship with the fault system is the core element of this system is the core element of this thesis.thesis.
The conclusion of my thesis about The conclusion of my thesis about sand-sand-depositional-modeldepositional-model and its related and its related interpretationsinterpretations differ from those by Chevron group.differ from those by Chevron group.
Results ComparisonResults Comparison
Chevron group concluded:Chevron group concluded:
1)1) The 8500-ft sand is a localized The 8500-ft sand is a localized channel in a small withdrawal channel in a small withdrawal basin just north of the salt. basin just north of the salt.
2)2) The salt mobilized before sands The salt mobilized before sands deposition in the Pleistocene.deposition in the Pleistocene.
3)3) The main fault system cuts the The main fault system cuts the block from east to west.block from east to west.
Results Comparison: Results Comparison: (1) 8500-ft Limitation(1) 8500-ft Limitation
GB-191BaseMap
8500’ Sand
4500’ Sand
The previous two The previous two seismic sections seismic sections doubt the idea of doubt the idea of sand limitation to sand limitation to the north part of the north part of GB-191. GB-191.
Results Comparison: Results Comparison: (1) 8500-ft Limitation(1) 8500-ft Limitation
GB-191BaseMap
SaltSalt
8500’ Sand
4500’ Sand
Results Comparison: Results Comparison: (2) Relative Dating(2) Relative Dating
Strata, within the uplifted area, can help in Strata, within the uplifted area, can help in determining the thickness of layers deposited before determining the thickness of layers deposited before salt evaluation. salt evaluation.
Slope System
SaltSalt
Uplifted
Thrusted
Uplifted Vs. thrusted layersUplifted Vs. thrusted layers
Results Comparison: Results Comparison: (2) Relative Dating(2) Relative Dating
In Texas-Louisiana shelf and slope, an overburden In Texas-Louisiana shelf and slope, an overburden thickness of about 5000 ft is required for salt to start thickness of about 5000 ft is required for salt to start rising rising (Nelson, 1991)(Nelson, 1991). .
According to the velocity model in the area, 5000 ft is According to the velocity model in the area, 5000 ft is about 1.3 seconds (about 1.3 seconds (average velocity of 1200 m/saverage velocity of 1200 m/s). ).
Slope System
SaltSalt
> 5000 ft> 5000 ft
Results Comparison: Results Comparison: (2) Relative Dating(2) Relative Dating
Therefore, at least 1.3 seconds of uplifted sediments Therefore, at least 1.3 seconds of uplifted sediments should lie below the 4500-ft sand to prove that the salt should lie below the 4500-ft sand to prove that the salt diaper predated the sand depositiondiaper predated the sand deposition
Slope System
SaltSalt
> 5000 ft> 5000 ft4500’ Sand
8500’ Sand
Results Comparison: Results Comparison: (2) Relative Dating(2) Relative Dating
This also can be justified if an unconformity in-between the This also can be justified if an unconformity in-between the 4500-ft sand and the salt peak can be found4500-ft sand and the salt peak can be found
(b)
Slope System
SaltSalt
< 5000 ft< 5000 ft4500’ Sand
8500’ Sand
UnconformityUnconformity
Unfortunately, seismic doesn’t prove this unconformity and Unfortunately, seismic doesn’t prove this unconformity and lines show only a thin section of less than a second in-lines show only a thin section of less than a second in-between the salt high and the 4500-ft sand. between the salt high and the 4500-ft sand.
This challenges depositional model of Fugitt, et. al. This challenges depositional model of Fugitt, et. al.
My Interpretation
Results Comparison: Results Comparison: (3) Fault System(3) Fault System
That fault separates between salt withdrawal area to the That fault separates between salt withdrawal area to the north and salt added area to the south. north and salt added area to the south.
My bounding fault runs from north-west to south-eastMy bounding fault runs from north-west to south-east
Fault A
Fault B
Chevron
A normal fault cuts the block from east to west and trap A normal fault cuts the block from east to west and trap the sand to the north. the sand to the north.
Results Comparison: Results Comparison: (3) Fault System(3) Fault System
Map ViewMap View
SaltSalt
YY
Section XSection X
Map ViewMap View
Perpendicular to the strike
(Uplifted strata)
Parallel to the strike
(Limit of the uplifted strata)
SaltSalt
XX
Section YSection Y
Results Comparison: Results Comparison: (3) Fault System(3) Fault System
Uplifted Area
Salt
Parallel to the strike
SaltSalt
Section XSection X
(Limit of the uplifted strata)
Results Comparison: Results Comparison: (3) Fault System(3) Fault System
Uplifted Strata
Salt
Perpendicular to the strike
SaltSalt
Section YSection Y
(Uplifted strata)
Results Comparison: Results Comparison: (3) Fault System(3) Fault System
My Interpretation
Fault A
Chevron
1)1) The 8500-ft sand is a localized The 8500-ft sand is a localized channel in a small withdrawal channel in a small withdrawal basin just north of the salt. basin just north of the salt.
2)2) The salt mobilized before sands The salt mobilized before sands deposition in the Pleistocene.deposition in the Pleistocene.
3)3) The main fault system cuts the The main fault system cuts the block from east to west.block from east to west.
ConclusionConclusion
The salt diapir is still in its active stage. It splits the The salt diapir is still in its active stage. It splits the block into two zones, east and west. East zone strata block into two zones, east and west. East zone strata are gently dipping while west zone strata are rotated, are gently dipping while west zone strata are rotated, uplifted, and faulted.uplifted, and faulted.
A bounding fault that controls the overall structure A bounding fault that controls the overall structure separates the two zones. Downthrown-strata are separates the two zones. Downthrown-strata are slightly modified and pierced by the salt. Upthrown-slightly modified and pierced by the salt. Upthrown-strata, however, are uplifted and rotated but not strata, however, are uplifted and rotated but not pierced by the salt.pierced by the salt.
Other secondary faults are located to the left of the Other secondary faults are located to the left of the bounding fault in the west zone. These faults bounding fault in the west zone. These faults accommodated the uplift in strata within the region. As accommodated the uplift in strata within the region. As a result, they reduced the tension within the uplifted a result, they reduced the tension within the uplifted strata and introduced a new pressure over the salt-strata and introduced a new pressure over the salt-west-flank.west-flank.
The 4500-ft and 8500-ft sands are prediapiric; The 4500-ft and 8500-ft sands are prediapiric; deposited prior to salt evolution.deposited prior to salt evolution.
The 8500-ft sand is not localized in a small basin to The 8500-ft sand is not localized in a small basin to the north of GB-191. Some evidences show a the north of GB-191. Some evidences show a possible continuation to the south of the block.possible continuation to the south of the block.
ConclusionConclusion
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