A Deterministic Evaluation of eismic Fidelity using Velocity Modeling ...

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northern Gulf margin provides insights into the local structures in areas such as Vinton Dome. Structures that developed in the stratigraphic interval from the Upper Jurassic through the Cenozoic formed resulting from sediment-driven gravity loading resulting from salt displacement and resulting from gravity spreading. Many of these structures have been imaged with 2-D seismic and interpreted from well data to include listric normal downto-basin growth faults, roll over structures, en echelon faults, counter regional faults, and localized radial faults. Salt displacement has been modeled to be primarily driven by vertical sediment movement and is characterized by withdrawal and diapirism on the shelf and upper slope and by canopy emplacement and withdrawal on the middle to lower slope. Manifesting basinward gravity spreading is by large-scale updip growth faulting and downdip contraction (Peel, et al., 1995). Growth faults are listric normal faults that show an expansion or thickening of basin fill in their hanging walls as loading continues and the fault becomes displaced. Identification of the displacement resulting from growth faults in the northern Gulf of Mexico Basin is by different contraction features at the base of the continental margin. Toe thrust-faults, fold belts, salt canopies, and salt deformations are the principal contraction features. 18
Dividing the Gulf of Mexico Basin into four provinces is the method of describing the structural components (Figure 8). Division of provinces is according to the timing of extension (Peel, et al., 1995). Vinton Dome falls within the Central Province, dominated by isolated structural systems such as fault compartments and radial faulting associated with diapirs surrounded by areas of relatively simple structures such as extensional normal faults. Understanding the relationships between salt flow and listric normal faults is essential in deciphering the complex structure of Vinton Dome. Pressure gradients resulting from the weight of overlying sediments are the source for salt flow in nonorogenic environments. Basinward movement of sediments above some decollement surface generates listric normal faults. In the Gulf of Mexico Basin, salt flow is a function of either differential sediment loading or the creation of a density gradient produced by denser sediments on top of less dense salt resulting in buoyant salt rise. Differential loading refers to the situation that occurs when two adjacent vertical columns of sediment of different mass cover a common level of salt and result from depositional variations. If sediments are less dense, then salt will tend to move out from under the salt high into the adjacent salt. Equal salt and sediment densities result in no salt movement. Higher sediment densities drive salt out of the salt bed into the salt high (Figure 9). Lateral extension will spread the salt and sediment layers over a larger area (Nelson, 1991). 19
Page 1 and 2: Chapter 1 Introduction 1.1 Summary
Page 3 and 4: 1.2.1 Geology Vinton Dome is a pier
Page 5 and 6: layer in land data that in extreme
Page 7 and 8: logs as being an effective approach
Page 9 and 10: Chapter 2 Geology of Vinton Dome 2.
Page 11 and 12: The Gulf of Mexico Basin contains U
Page 13 and 14: developed from repetitive episodes
Page 15 and 16: of the upper Frio. Overlying the lo
Page 17: structures form by the differential
Page 21 and 22: 2.6 Geologic Modeling Historically,
Page 23 and 24: 2.6.1 Vinton Geology Analysis of se
Page 25 and 26: surface and a number of small subma
Page 27 and 28: established the Mississippi delta a
Page 29 and 30: Figure 2. Outline of the extents of
Page 31 and 32: Figure 6. Salt sediment contacts us
Page 33 and 34: Figure 10. Fault pattern representa
Page 35 and 36: Figure 14. Stratigraphic column of
Page 37 and 38: Top Hackberry Sand Hackberry Base N
Page 39 and 40: Figure 18. Structure map contoured
Page 41 and 42: Gyroidina scalata Outer shelf Gyroi
Page 43 and 44: Upper Frio Sands A Sand base B Sand
Page 45 and 46: Top Anahuac Middle Shelf Heterosteg
Page 47 and 48: Miocene sands Figure 27. Spontaneou
Page 49 and 50: Vinton Dome Figure 30. Late Miocene
Page 51 and 52: 3.1 Introduction Chapter 3 Processi
Page 53 and 54: 3.3 Processing My primary objective
Page 55 and 56: 38-42). For QC I would brute stack
Page 57 and 58: Another significant issue was to id
Page 59 and 60: Table 2 Final processing flow Input
Page 61 and 62: Number of stacked traces 12.5km 12.
Page 63 and 64: TWT seconds a 12.5km TWT seconds b
Page 65 and 66: TWT seconds 12.5km Figure 38. Brute
Page 67 and 68: TWT seconds 12.5km Figure 40. Brute
Page 69 and 70:
TWT seconds 12.5km Figure 44. Brute
Page 71 and 72:
Chapter 4 Velocity Modeling and Pre
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quality motivated a reassessment of
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The layer-based approach is much mo
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of seismically derived velocities.
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To test differences between seismic
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ased data, indicating higher fideli
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4.5 Conclusions and Discussion I co
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By using sonic logs the velocities
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Figure 50. Velocity cube of the sed
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Velocity in ft/sec Figure 52. Prest
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Depth in kilo-feet a. b. Figure 56.
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Figure 59. Graphic user interface s
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Truncation of sediment onto salt a
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s 1 s 1 S e C 0 1 O W 34 M M 0 C a
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Prestack time migrated velocity mod
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Salt on PSTM Prestack time migrated
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Time in seconds Bright spot 12.5km
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PSTM prestack time well-based migra
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attributes also provided me with an
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types of coherence. The first type
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comparisons, those at the same dept
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Identifying reduced fidelity in the
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Faults Channel Figure 72. PSTM cohe
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Depth slice of coherence cube from
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Compartmentalized faults 5895 feet
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Well-based PSDM - faults traced fro
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Channel Radial faults 3985 feet a C
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Well-based PSDM Prestack time migra
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Well-based PSDM Faults imaged with
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structure and they must complement
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Imaged poorly was a fault identifie
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interpretation of the high angle gr
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Inline 1391 well-based PSDM Inline
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Figure 83. Interpretation showing t
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Channel nnen a Channel b Figure 85.
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yet there are several issues regard
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7.2.3 Attributes I used attributes
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seismic data provided a more detail
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educed the noise in the field data
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PSDM data to evaluate velocity mode
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10, Society of Exploration Geophysi
Page 153 and 154:
Marfurt, K. J., Kirlin, R. L., Farm
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