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

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integrate stratigraphic interpretations into the geologic model to begin to piece together events related to salt tectonics. 6.3 Interpretation 6.3.1 Seismic I was able to identify small, compartmentalized faults in the area identified by the operator on the well-based PSDM volume. A comparison of the well-based PSDM with the prestack time migrated velocity model PSDM data shows the higher resolution achieved with the well-based model (Figure 81). To determine which of the two is the proper placement I used electronic well logs to compare well ties. The well-based PSDM consistently placed the salt picked with well logs at the high acoustic impedance boundary on the surface seismic data while the prestack time migrated velocity model PSDM placed the salt pick from well logs below the high acoustic impedance boundary. Wells tie in the inline, crossline, and depth slices with the well-based data (Figure 82). Based on the correct placement of salt in the x, y, and z directions it is apparent that the prestack time migrated velocity model is too slow and the fidelity of the well-based PSDM is higher. I was able to enhance resolution along the salt flanks with depth migration. Using sediment layers to determine where they truncate next to the salt flank, a complex geometry begins to emerge. Interpretations show the salt body is mainly a cylindrical shape with various protuberances, salt wedges, and overhangs (Figure 83). 130
Imaged poorly was a fault identified in the western half of the survey in the PSTM, but was focused with detail in the well-based data (Figure 84). The large fault is a normal fault clearly dipping to the north. Based on this interpretation a counter regional fault is the controlling fault for Vinton Dome. 6.3.2 Coherence I used coherence data to identify several channels (Figure 85). These channels are at a depth that corresponds to the Miocene. To gain a better understanding of the depositional history around the dome needs further interpretation and integration of these data. Details of the depositional history help to guide a better understanding of the sediment load that in turn impact the salt tectonics. 6.4 Conclusions and Discussion To provide the detail needed to image structures and stratigraphy near Vinton Dome required PSDM, more precisely a PSDM migrated with a well-based sediment velocity model. Demonstration of the improved fidelity achieved through a well-based PSDM was in the details revealed in small faults and the details imaged in sediments near the salt dome. I interpreted three areas with a higher degree of accuracy than was previously available, the salt, stratigraphy, and structure. 131
Page 1 and 2:
Chapter 1 Introduction 1.1 Summary
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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
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Dividing the Gulf of Mexico Basin i
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2.6 Geologic Modeling Historically,
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2.6.1 Vinton Geology Analysis of se
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surface and a number of small subma
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established the Mississippi delta a
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Figure 2. Outline of the extents of
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Figure 6. Salt sediment contacts us
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Figure 10. Fault pattern representa
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Figure 14. Stratigraphic column of
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Top Hackberry Sand Hackberry Base N
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Figure 18. Structure map contoured
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Gyroidina scalata Outer shelf Gyroi
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Upper Frio Sands A Sand base B Sand
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Top Anahuac Middle Shelf Heterosteg
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Miocene sands Figure 27. Spontaneou
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Vinton Dome Figure 30. Late Miocene
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3.1 Introduction Chapter 3 Processi
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3.3 Processing My primary objective
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38-42). For QC I would brute stack
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Another significant issue was to id
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Table 2 Final processing flow Input
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Number of stacked traces 12.5km 12.
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TWT seconds a 12.5km TWT seconds b
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TWT seconds 12.5km Figure 38. Brute
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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.
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
Page 121 and 122: Well-based PSDM - faults traced fro
Page 123 and 124: Channel Radial faults 3985 feet a C
Page 125 and 126: Well-based PSDM Prestack time migra
Page 127 and 128: Well-based PSDM Faults imaged with
Page 129: structure and they must complement
Page 133 and 134: interpretation of the high angle gr
Page 135 and 136: Inline 1391 well-based PSDM Inline
Page 137 and 138: Figure 83. Interpretation showing t
Page 139 and 140: Channel nnen a Channel b Figure 85.
Page 141 and 142: yet there are several issues regard
Page 143 and 144: 7.2.3 Attributes I used attributes
Page 145 and 146: seismic data provided a more detail
Page 147 and 148: educed the noise in the field data
Page 149 and 150: PSDM data to evaluate velocity mode
Page 151 and 152: 10, Society of Exploration Geophysi
Page 153 and 154: Marfurt, K. J., Kirlin, R. L., Farm
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