high resolution seismic stratigraphy using sub-bottom...
TRANSCRIPT
1. Motivation
High resolution seismic stratigraphy using sub-bottom profiler
Use sub-‐bo)om profiler data to create a HR seismic stra6graphic framework for a study
area in the deepwater Gulf of Mexico
2. Study Area
3. Sub-bottom Profiler
DEFINITIONS
The terminology of salt tectonics can be confusing;the modern study of salt tectonics (aided by high-resolution 3-D seismic reflection data) is still evolv-ing, and the established terminology for the northernGulf of Mexico, being focused principally on al-lochthonous salt and minibasins, needs updatingand clarifying as attention shifts to subsalt settings.This process is slow because much of the newer data(wide-azimuth seismic and advancedpre–stack depthmigrations) remain proprietary and closely guardedby a petroleum exploration community that is un-derstandably reluctant to share information onwhatis currently one of themost competitive exploration
arenas in North America. A useful glossary of salttectonic terminology can be found in Jackson andTalbot (1991), and additional definitions are pro-videdby Jackson (1995),Rowan (1995), andRowanet al. (1999); however, the following additional orexpanded definitions are applied in this study.
Primary Basin
A sedimentary depocenter formed directly on theautochthonous salt layer with little or no strati-graphic omission. Therefore, primary basins con-tain a continuous stratigraphic sequence from theLouann Salt below to the allochthonous salt or seafloor above (Figure 2). Throughout much of the
Figure 1. Location map for the northern Gulf of Mexico. The bathymetric map (public domain National Oceanic and AtmosphericAdministration and National Geophysical Data Center 3 Arc-Second Coastal Relief Model) illustrates the extent of shallow allochthonoussalt and the associated secondary minibasins. The basinward limit of the canopy is marked by the Sigsbee Escarpment, which has abathymetric relief of up to 1000m (3300 ft). The blue outline indicates the study area of approximately 100,000 km2 (38,600 mi2), coveringparts of Mississippi Canyon (MC), Atwater Valley (AT), Green Canyon (GC), Walker Ridge (WR), Garden Banks (GB), and KeathleyCanyon (KC) protraction areas. Coastal Louisiana and Texas are shaded gray. The location of New Orleans (NO) is highlighted in red.
Pilcher et al. 221
Study Area
4. Representative Data 6. Methods
5. Processing
7. Additional Work
8. References & Acknowledgments
Jordan Myers, The University of Oklahoma
Figure 1. Fledermaus 3-D seafloor perspective view looking toward the north. Vertical exaggeration is 6x.
A A’
B B’
C C’
A A’
B B’
C C’
Step 2: Create Complex Signal by combining the cross-‐correlated signal (Correlate) with the Hilbert Transform of the cross-‐correlated signal. -‐This creates a signal made up a Real and an Imaginary part.
Step 3: Complex Modulus is created by taking the square root of the sum of the squares of the Complex Signal. This becomes the Envelope or instantaneous amplitude. -‐The Envelope has the same length and sample interval as the Correlate but contains only posi6ve numbers and no longer has any phase informa6on. The result is much lower in frequency and can be displayed in a manner much more similar to conven6onal seismic.
Step 1: Cross-‐correlate, deconvolve or match filter the raw data with outgoing sweep signal. -‐This results in a signal more similar to conven6onal seismic signal and is done by the sub-‐bo)om profiler.
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
Chirp Sub-Bottom Profiler Processing-A ReviewPaul HenkartSea Technology; Oct 2006; 47, 10; ProQuest Environmental Science Journalspg. 35
38
D
1 5
0 0
Dip (ms/m)
D`
Channel-Lobe Complex
MTC A
MTC B
MTC C
Mass Transport Complex
Unconformity
Parallel to sub-parallel Reflections
Channel-like features
MTC D
Salt
STUDY AREA SW NE
(b)
(c)
(a)
2.3 -
2.1 -
2.0 -
1.9 -
1.8 -
1.7 -
SECS 4500 m
150 m
MTC B
MTC A
SW NE
MTC CMTC D
Channel-likeFeatures
Channel-Lobe Complex
D D`
Figure 21: (a) Seafloor dip map showing the study area (blue polygon) (b) Seismic line showing mapped seismic facies. Description is based on seismic reflectivity, event continuity, and external geometry (c) Geologic interpretation of seismic line DD`. Observe the Influence of salt withdrawal on deposition and the prevalence of MTC packages above the channel-lobe complex.
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vertically restricted to the lower positions of each sequence and are systematically
positioned inside valleys, without any evidence of fluvial floodplain aggradation outside
those “containers”. Figure 2B illustrates this distinctive degradational stacking pattern,
which shows that the LST and TST are only preserved within the valleys, whereas the
overall aggradation is strictly limited to the marine mudstones of the HST. The controls
that affect these stacking patterns will be discussed in the following section.
Figure 14: Time-slice and cross-section across the valley showing 3 discrete valley-fill stages: A) point bar accretion during active fluvial deposition (lowstand), B) transgressive deposits passively onlapping the valley walls, and C) open marine highstand sediments capping the entire incised valley complex (schematic block diagrams and landscape photos, courtesy of H. W. Posamentier). Refer to Figure 8 for location of time slice.
• Henkart, P., 2006, Chirp Sub-‐Bo)om Profiler Processing – A review: Sea Technology, v.47, p. 35-‐38. • Kleiner, A., 2004, Run Silent, Run Deep – U.S. Military Missions for the Hugin UUV: Unmanned Systems, March/April 2004, p. 32-‐35. • Mann, R.G., Bryant, W.R., and Rabinowitz, P.D., 1992, Seismic Facies Interpreta6on of the Northern Green Canyon Area, Gulf of Mexico: American Associa6on of Petroleum Geologists, Memoir, v. 53, p. 343-‐360. • Oyodele, O., 2005, 3D High Resolu6on Seismic Imaging of Middle-‐Late Quaternary Deposi6onal Systems, Southeast Green Canyon, Sigsbee Escarpment, Gulf of Mexico: MS Thesis, University of Houston. • Reijenstein, H., 2008, Seismic Geomorphology and High-‐Resolu6on Stra6graphy of Inner Shelf Fluvial, Deltaic and Marine Sequences, Gulf of Thailand: MS Thesis, University of Houston. • Pilcher, R.S., Kilsdonk, B., and Trude, J., 2011, Primary basins and their boundaries in the deep-‐water northern Gulf of Mexico: Origin, trap types, and petroleum system implica6ons: American Associa6on of Petroleum Geologists, Bulle6n, v. 95, p. 219-‐240.
A special thanks to BP for providing the sub-‐bo)om profiler data and to Dr. Kurt Marfurt for his tremendous assistance.
Frequency Modulated between 2-‐10 kHz Total Record of 300 ms
Hugin 3000 AUV with EdgeTech Chirp Sub-‐bo)om Profiler
Maximum Depth = 3,000 m Run6me = up to 50 hours Real-‐6me data feedback
Combined imaging of 2D HR seismic lines and 6me slices from 3D conven6onal seismic
Apply seismic facies for conven6onal seismic specific to the Green Canyon area to HR sub-‐bo)om profiler data in order to iden6fy elements of deepwater stra6graphy
Holstein Field, Blocks 644 & 645 of the Green Canyon Area, Gulf of Mexico