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

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12.5km 12.5km a b Figure 46. Sections comparing the processing flows with minimal processing Table 1(a) and more aggressive processing as described in Table 2 (b). 12.5km 12.5km 12.5 km a b Figure 47. Depth slices used for comparing the processing flows with minimal processing (a) and as described in Table 2 (b). 70
Chapter 4 Velocity Modeling and PreStack Depth Migration (PSDM) 4.1 Introduction Pre-stack depth migration (PSDM) has been widely used for large, 3-D seismic marine surveys. As a result the methods used to develop velocity models for the PSDM have been primarily based on marine data. Many of the same problems observed and mitigated in marine seismic data using PSDM exist in 3-D land surveys, but differences in 3-D marine data and 3-D land data warrant a reevaluation of methods used to generate velocity models for land data. Reexamining the methods for deriving velocity models for land PSDM has the potential for establishing a different paradigm for velocity modeling of 3-D land seismic data. Problems resolved by PSDM in marine seismic data are observed in the pre-stack time migrated (PSTM) data in the 3-D Vinton Dome seismic survey. Misplaced salt, poor well ties and the inability to image small fault blocks are problems resulting from low fidelity of the Vinton Dome PSTM seismic data. Two primary reasons for these problems are strong lateral velocity variations caused by salt, and the related structures in the sediment section related to salt movement, and anisotropy mainly occurring in the shale bodies. PSDM using an accurate interval velocity model can generate high fidelity subsurface images in the presence of lateral velocity variations. Therefore, estimation of an accurate interval velocity model is key to improving the fidelity of the subsurface image at Vinton Dome (Fagin, 1999). 71
Page 1 and 2:
Chapter 1 Introduction 1.1 Summary
Page 3 and 4:
1.2.1 Geology Vinton Dome is a pier
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layer in land data that in extreme
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logs as being an effective approach
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Chapter 2 Geology of Vinton Dome 2.
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The Gulf of Mexico Basin contains U
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developed from repetitive episodes
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of the upper Frio. Overlying the lo
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structures form by the differential
Page 19 and 20: Dividing the Gulf of Mexico Basin i
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: TWT seconds 12.5km Figure 44. Brute
Page 73 and 74: quality motivated a reassessment of
Page 75 and 76: The layer-based approach is much mo
Page 77 and 78: of seismically derived velocities.
Page 79 and 80: To test differences between seismic
Page 81 and 82: ased data, indicating higher fideli
Page 83 and 84: 4.5 Conclusions and Discussion I co
Page 85 and 86: By using sonic logs the velocities
Page 87 and 88: Figure 50. Velocity cube of the sed
Page 89 and 90: Velocity in ft/sec Figure 52. Prest
Page 91 and 92: Depth in kilo-feet a. b. Figure 56.
Page 93 and 94: Figure 59. Graphic user interface s
Page 95 and 96: Truncation of sediment onto salt a
Page 97 and 98: s 1 s 1 S e C 0 1 O W 34 M M 0 C a
Page 99 and 100: Prestack time migrated velocity mod
Page 101 and 102: Salt on PSTM Prestack time migrated
Page 103 and 104: Time in seconds Bright spot 12.5km
Page 105 and 106: PSTM prestack time well-based migra
Page 107 and 108: attributes also provided me with an
Page 109 and 110: types of coherence. The first type
Page 111 and 112: comparisons, those at the same dept
Page 113 and 114: Identifying reduced fidelity in the
Page 115 and 116: Faults Channel Figure 72. PSTM cohe
Page 117 and 118: Depth slice of coherence cube from
Page 119 and 120: 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
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Marfurt, K. J., Kirlin, R. L., Farm
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