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.

39

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