BOEM's 3DX-Based Regional Bathymetric Data Set, Deepwater Gulf of Mexico: Automated Seafloor Characterization, Geohazards Assessment, and Engineering Planning

An electronic navigational chart is a major source of information for the navigator. The component that contributes most significantly to the safety of navigation on water is the information on the depth of an area. For the purposes of this article, the authors use data obtained by the interferometric sonar GeoSwath Plus. The data were collected in the area of the Port of Szczecin. The samples constitute large sets of data. Data reduction is a procedure to reduce the size of a data set to make it easier and more effective to analyse. The main objective of the authors is the compilation of a new reduction algorithm for bathymetric data. The clustering of data is the first part of the search algorithm. The next step consists of generalisation of bathymetric data. This article presents a comparison and analysis of results of clustering bathymetric data using the following selected methods:K-means clustering algorithm, traditional hierarchical clustering algorithms and self-organising map (using artificial neural networks).

Download Full-text

Global distribution of photosynthetically available radiation on the seafloor

Earth System Science Data ◽

10.5194/essd-12-1697-2020 ◽

2020 ◽

Vol 12 (3) ◽

pp. 1697-1709

Author(s):

Jean-Pierre Gattuso ◽

Bernard Gentili ◽

David Antoine ◽

David Doxaran

Keyword(s):

Surface Area ◽

R Package ◽

Global Distribution ◽

Optical Data ◽

Photosynthetically Available Radiation ◽

Pixel Size ◽

Net Community Production ◽

Data Set ◽

Bathymetric Data ◽

Surface Areas

Abstract. A 21 year (1998–2018) continuous monthly data set of the global distribution of light (photosynthetically available radiation, PAR, or irradiance) reaching the seabed is presented. This product uses ocean color and bathymetric data to estimate benthic irradiance, offering critical improvements on a previous data set. The time series is 4 times longer (21 versus 5 years), the spatial resolution is better (pixel size of 4.6 versus 9.3 km at the Equator), and the bathymetric resolution is also better (pixel size of 0.46 versus 3.7 km at the Equator). The paper describes the theoretical and methodological bases and data processing. This new product is used to estimate the surface area of the seafloor where (1) light does not limit the distribution of photosynthetic benthic organisms and (2) net community production is positive. The complete data set is provided as 14 netCDF files available on PANGAEA (Gentili and Gattuso, 2020a, https://doi.org/10.1594/PANGAEA.910898). The R package CoastalLight, available on GitHub (https://github.com/jpgattuso/CoastalLight.git, last access: 29 July 2020), allows us (1) to download geographical and optical data from PANGAEA and (2) to calculate the surface area that receives more than a given threshold of irradiance in three regions (nonpolar, Arctic, and Antarctic). Such surface areas can also be calculated for any subregion after downloading data from a remotely and freely accessible server.

Download Full-text

Red Snapper: Ecology and Fisheries in the U.S. Gulf of Mexico

Red Snapper: Ecology and Fisheries in the U.S. Gulf of Mexico ◽

10.47886/9781888569971.ch3 ◽

2007 ◽

Keyword(s):

Gulf Of Mexico ◽

Red Snapper ◽

Lutjanus Campechanus ◽

Nursery Areas ◽

Side Scan Sonar ◽

Bathymetric Data ◽

Habitat Effect ◽

Inner Continental Shelf ◽

The U.S ◽

Trawl Surveys

Abstract.—Trawl surveys were conducted to measure patterns of habitat use by newly settled red snapper Lutjanus campechanus at three natural banks on the inner continental shelf of Texas. Digital side-scan sonar and multibeam bathymetric data were used to define inshore (mud), ridge (shell), and offshore (mud) habitats for Freeport Rocks, Heald Bank, and Sabine Bank. Otter trawls were conducted July through September in 2003 (Heald Bank, Sabine Bank) and in 2004 (Freeport Rocks) during the settlement period of red snapper. Freeport Rocks had markedly higher densities of red snapper (91 ha⁻1) in 2004 than Heald Bank (6 ha⁻1) or Sabine Bank (<1 ha⁻1) in 2003. A significant habitat effect was observed at Heald Bank and densities were higher at offshore mud habitats; no habitat effect was detected for Freeport Rocks or Sabine Bank. Growth rates varied from 0.86 mm‧d⁻1 at Sabine Bank up to 1.12 mm‧d⁻1 at Freeport Rocks, and rates were higher on inshore and offshore mud than ridge habitats. Otolith-based estimates of age indicated that settlers were first detected at 22–28 d and the majority of individuals were 30–60 d. Hatch dates peaked from early June to early July in both 2003 and 2004. Results from this study indicate that both shell and inshore and offshore mud habitats associated with these natural banks serve as settlement habitat of red snapper, and all three habitats have the potential to function as nursery areas of this species.

Download Full-text

Warping least-squares inversion for 4D velocity change: Gulf of Mexico case study

Interpretation ◽

10.1190/int-2018-0145.1 ◽

2019 ◽

Vol 7 (2) ◽

pp. SB23-SB31

Author(s):

Chang Li ◽

Mark Meadows ◽

Todd Dygert

Keyword(s):

Gulf Of Mexico ◽

Least Squares ◽

Synthetic Data ◽

Inversion Method ◽

Velocity Change ◽

Data Set ◽

Phase Constraints ◽

Free Case ◽

Velocity Changes

We have developed a new trace-based, warping least-squares inversion method to quantify 4D velocity changes. There are two steps to solve for these velocity changes: (1) dynamic warping with phase constraints to align the baseline and monitor traces and (2) least-squares inversion for 4D velocity changes incorporating the time shifts and 4D amplitude differences (computed after trace alignment by warping). We have demonstrated this new inversion workflow using simple synthetic layered models. For the noise-free case, phase-constrained warping is superior to standard, amplitude-based warping by improving trace alignment, resulting in more accurate inverted velocity changes (less than 1% error). For synthetic data with 6% rms noise, inverted velocity changes are reasonably accurate (less than 10% error). Additional inversion tests with migrated finite-difference data shot over a realistic anticline model result in less than 10% error. The inverted velocity changes on a 4D field data set from the Gulf of Mexico are more interpretable and consistent with the dynamic reservoir model than those estimated from the conventional time-strain method.

Download Full-text

A practical workflow using quantitative interpretation of seismic amplitudes to derisk infill wells in deepwater Gulf of Mexico: The Auger example

The Leading Edge ◽

10.1190/tle38100754.1 ◽

2019 ◽

Vol 38 (10) ◽

pp. 754-761 ◽

Cited By ~ 1

Author(s):

Liqin Sang ◽

Uwe Klein-Helmkamp ◽

Andrew Cook ◽

Juan R. Jimenez

Keyword(s):

Gulf Of Mexico ◽

Time Lapse ◽

Quantitative Interpretation ◽

Efficient Manner ◽

Data Set ◽

Seismic Amplitude ◽

Imperfect Data ◽

Avo Inversion ◽

Fluid Saturation ◽

Single Well

Seismic direct hydrocarbon indicators (DHIs) are routinely used in the identification of hydrocarbon reservoirs and in the positioning of drilling targets. Understanding seismic amplitude reliability and character, including amplitude variation with offset (AVO), is key to correct interpretation of the DHI and to enable confident assessment of the commercial viability of the reservoir targets. In many cases, our interpretation is impeded by limited availability of data that are often less than perfect. Here, we present a seismic quantitative interpretation (QI) workflow that made the best out of imperfect data and managed to successfully derisk a multiwell drilling campaign in the Auger and Andros basins in the deepwater Gulf of Mexico. Data challenges included azimuthal illumination effects caused by the presence of the Auger salt dome, sand thickness below tuning, and long-term production effects that are hard to quantify without dedicated time-lapse seismic. In addition, seismic vintages with varying acquisition geometries led to different QI predictions that further complicated the interpretation story. Given these challenges, we implemented an amplitude derisking workflow that combined ray-based illumination assessments and prestack data observations to guide selection of the optimal seismic data set(s) for QI analysis. This was followed by forward modeling to quantify the fluid saturation and sand thickness effects on seismic amplitude. Combined with structural geology analysis of the well targets, this workflow succeeded in significantly reducing the risk of the proposed opportunities. The work also highlighted potential pitfalls in AVO interpretation, including AVO inversion for the characterization of reservoirs near salt, while providing a workflow for prestack amplitude quality control prior to inversion. The workflow is adaptable to specific target conditions and can be executed in a time-efficient manner. It has been applied to multiple infill well opportunities, but for simplicity reasons here, we demonstrate the application on a single well target.

Download Full-text

Investigation of deep-water Gulf of Mexico subsalt imaging using anisotropic model, data set and RTM — Tempest

Geophysics ◽

10.1190/geo2011-0043.1 ◽

2011 ◽

Vol 76 (5) ◽

pp. WB21-WB26 ◽

Cited By ~ 1

Author(s):

Fatmir Hoxha ◽

Jacqueline O’Connor ◽

Jeff Codd ◽

David Kessler ◽

Alex Bridge ◽

...

Keyword(s):

Gulf Of Mexico ◽

Deep Water ◽

Model Building ◽

Earth Model ◽

Anisotropic Model ◽

Model Data ◽

Data Set ◽

Depth Imaging ◽

The Tempest ◽

Time Migration

Performing accurate depth-imaging is an essential part of deep-water Gulf of Mexico exploration and development. Over the years, depth-imaging technology has provided reliable seismic images below complicated salt bodies, and has been implemented in workflows for both prospect generation as well as reservoir development. These workflows include time domain preprocessing using various multiple elimination techniques, anisotropic model building, and depth-imaging using anisotropic reverse time migration (RTM). However, the accuracy of the depth-migrated volumes is basically unknown because they are tested only in the locations where a well is drilled. In order to learn about the accuracy of anisotropic deep water Gulf of Mexico model building, and depth-imaging tools which are used for processing and imaging of field acquired data, we created a 3D vertical transverse isotropic (VTI) anisotropic earth model and a 3D seismic data set representing subsalt Gulf of Mexico geology. The model and data set are referred to as the Tempest data set, the original being created several years ago. The recent model and data set were created incorporating upgraded technology to reflect recent developments in data acquisition, model building and depth-imaging. Our paper presents the new Tempest anisotropic model, data set, and RTM prestack depth-migration (PSDM) results. The Tempest RTM PSDM is being used to learn about the differences between the exact geological model and the RTM PSDM image, helping in the interpretation of real RTM prestack depth-migrated data.

Download Full-text

Relationships between salt diapirism, faulting, and sedimentation on a Gulf of Mexico 3‐D data set

10.1190/1.1889782 ◽

1989 ◽

Author(s):

Robert D. Walters

Keyword(s):

Gulf Of Mexico ◽

Data Set ◽

Salt Diapirism

Download Full-text

Characterization of layered anisotropic media from prestack PS-wave-reflection data

Geophysics ◽

10.1190/1.2335419 ◽

2006 ◽

Vol 71 (5) ◽

pp. D171-D182 ◽

Cited By ~ 7

Author(s):

Jason E. Gumble ◽

James E. Gaiser

Keyword(s):

Gulf Of Mexico ◽

Seismic Data ◽

Equivalent Model ◽

Time Shift ◽

Layer By Layer ◽

Converted Wave ◽

Data Set ◽

Fracture Characterization ◽

Anisotropic Models ◽

Hti Media

Anisotropy and fracture characterization in individual layers is realized through iterative layer stripping corrections of four, converted-wave (PS-wave) synthetic reflection seismic data sets, generated from azimuthally anisotropic (HTI and TTI) models, and a four component (4-C) data set from the Teal South, Gulf of Mexico. The corrections were applied on a layer-by-layer basis to evaluate the efficacy of constant polarization rotation and time-shift operators. Equivalent isotropic models were compared to anisotropic models after layer-stripping corrections using rms amplitude and shear-wave-splitting time-difference maps to quantify and identify inherent errors in estimating seismic polarization parameters. For HTI media radial and transverse components of PS data that have had layer-stripping corrections applied, exhibit incorrect symmetry and orientations. This may adversely affect inversion and/or amplitude-variation with angle offset (AVO) and amplitude versus azimuth (AVA)analysis. Layer-stripping corrections applied to fast and slow ([Formula: see text] and [Formula: see text], respectively) components exhibit the correct symmetry and orientation. Time differences between PS1 and PS2 are computed using crosscorrelation. Previous studies have addressed some of the problems associated with layer-stripping corrections for the case of vertical fractures (HTI media) and poststack layer-stripping analyses. This study includes an equivalent model with dipping fractures (TTI media) and extends the scope to encompass the effects of anisotropy on prestack data. The results from an application of the same technique are also applied to a limited set of 4-C data from the Teal South project in the Gulf of Mexico. Results are consistent with those of previous studies involving solely poststack 4-C rotation analysis in terms of average, or zero offset, time differences and symmetry orientation. Offset and azimuth amplitude/traveltime variations, however, indicate that there is more information contained in prestack seismic data than 4-C rotation can comprehend.

Download Full-text

AVO inversion of a Gulf of Mexico bright spot—A case study

Geophysics ◽

10.1190/1.1444652 ◽

1999 ◽

Vol 64 (5) ◽

pp. 1480-1491 ◽

Cited By ~ 5

Author(s):

Patrice Nsoga Mahob ◽

John P. Castagna ◽

Roger A. Young

Keyword(s):

Gulf Of Mexico ◽

Poisson’S Ratio ◽

Poisson's Ratio ◽

Bright Spot ◽

Inversion Algorithm ◽

Seismic Line ◽

Data Set ◽

The Real ◽

Hydrocarbon Saturation ◽

Initial Starting

An iterative and linearized inversion algorithm carried out in the x-t domain has been applied to a prestack seismic data set from the central Gulf of Mexico, offshore Louisiana. Sonic and density curves from a well located close to the seismic line are used to generate the initial starting models for the inversion. We tested the geologically realistic hypothesis that the starting models have an accurate impedance structure outside of the potential pay zone and that the prospective pay zone will have mechanical properties consistent with the presence or absence of hydrocarbons. The inversion, performed with starting models with pay zones with a Poisson’s ratio appropriate for 100% brine saturation or with a Poisson’s ratio intermediate between expected values for full brine and hydrocarbon saturation, does not converge to the real seismic gather. However, with a starting model having a Poisson’s ratio appropriate for hydrocarbon saturation in the target zone, there is convergence from the initial to the real seismic gather.

Download Full-text