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

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the coherence cube after about one second. Based on this observation I used coherence to qualitatively assess the fidelity of data to determine the most accurate velocity model. My objective was to assess the value of attributes as a QC tool. 1.2.6 Interpretation I used the interpretation of the well-based PSDM to gain a better understanding of the geology. One of my objectives was to verify improved fidelity by providing a more detailed interpretation and to gain new insights into the geologic processes associated with Vinton Dome. I used well ties and synthetics to assess the accuracy of interpretations. Coherence also aided in my interpretation of salt and faults, and as a QC tool. Improved resolution of the Vinton Dome 3-D surface seismic data demonstrates the value of PSDM using a well-based velocity model in 3-D land surveys with piercement salt domes to provide a greater understanding of geology. Improved resolution translates to better interpretations that are necessary for understanding the evaluation of salt tectonics, structural details, and complex stratigraphy. 1.3 Conclusions and Discussion Assessing and improving the spatial fidelity of seismic imaging through a deterministic evaluation of surface seismic data with velocity modeling and attribute analysis was the goal of this study. I demonstrated a novel approach to modeling velocities using well 6
logs as being an effective approach to PSDM where the flanks of the dome were the primary imaging objective. I evaluated the effectiveness of the approaches used on the fidelity of the data. I used various data such as well logs and attributes to aid in the interpretation of the seismic data. Benchmarks to determine the effectiveness were the ability to improve imaging close to the salt flanks, the ability to image small compartmentalized fault blocks, detailed faults, and stratigraphic features such as stream channels that were not imaged using PSTM. To achieve the stated goal of this study I fulfilled objectives in processing, velocity modeling, interpretation and use of attributes as a QC tool. My conclusions are that using well logs to derive an initial sediment velocity model used for a PSDM provided greater fidelity in 3-D surface seismic land surveys with strong lateral velocity variations. I also concluded that the higher fidelity resulted in a greater signal to noise ratio, and improved interpretations over PSTM and standard PSDM. I used the enhanced fidelity for a more accurate interpretation to improve the understanding of the Vinton Dome geology. 7
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: layer in land data that in extreme
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 and 18: 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
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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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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
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Marfurt, K. J., Kirlin, R. L., Farm
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