Sediment dispersal and redistributive processes in axial and transverse deep-time source-to-sink systems of marine rift basins: Dampier Sub-basin, Northwest Shelf, Australia

Morphological scaling relationships between source‐to‐sink segments have been widely explored in modern settings, however, deep‐time systems remain difficult to assess due to limited preservation of drainage basins and difficulty in quantifying complex processes that impact sediment dispersals. Integration of core, well‐logs and 3‐D seismic data across the Dampier Sub‐basin, Northwest Shelf of Australia, enables a complete deep‐time source‐to‐sink study from the footwall (Rankin Platform) catchment to the hanging wall (Kendrew Trough) depositional systems in a Jurassic late syn‐rift succession. Hydrological analysis identifies 24 drainage basins on the J50.0 (Tithonian) erosional surface, which are delimited into six drainage domains confined by NNE‐SSW trending grabens and their horsts, with drainage domain areas ranging between 29 and 156 km2. Drainage outlets of these drainage domains are well preserved along the Rankin Fault System scarp, with cross‐sectional areas ranging from 0.08 to 0.31 km2. Corresponding to the six drainage domains, sedimentological and geomorphological analysis identifies six transverse submarine fan complexes developing in the Kendrew Trough, ranging in areas from 43 to 193 km2. Seismic geomorphological analysis reveals over 90‐km‐long, slightly sinuous axial turbidity channels, developing in the lower topography of the Kendrew Trough which erodes toe parts of transverse submarine fan complexes. Positive scaling relationships exist between drainage outlet spacing and drainage basin length, and drainage outlet cross‐sectional area and drainage basin area, which indicates the geometry of drainage outlets can provide important constraints on source area dimensions in deep‐time source‐to‐sink studies. The broadly negative bias of fan area to drainage basin area ratios indicates net sediment losses in submarine fan complexes caused by axial turbidity current erosion. Source‐to‐sink sediment balance studies must be done with full evaluating of adjacent source‐to‐sink systems to delineate fans and their associated up‐dip drainages, to achieve an accurate tectonic and sedimentologic picture of deep‐time basins.publishedVersio

Targeting reserve growth opportunities in the northern Gulf of Mexico Basin: transferring secondary gas recovery technology to the offshore environment - book 2

The Bureau of Economic Geology's (BEG) Offshore Secondary Gas Recovery is a multi-fiscal-year project funded by the U.S. Department of Energy, whose goal is to research new techniques for defining the structure, stratigraphy, and hydrocarbons in a mature area in the northern Gulf of Mexico and to utilize those multidisciplinary methods to identify additional gas resources, as well as predict regional trends in hydrocarbon accumulation. Phases 1 and 2 of the project work plan (Project Preparation and Data Gathering and Loading, respectively) are completed. Phase 3 of the plan (Data Analysis) is 65 percent completed, with all third- and fourth-order key surfaces mapped in the log data. Sixty fourth-order and twelve third-order sequences have been defined using well data, and key flooding surfaces have been mapped in the seismic volume. Structural mapping of 13 key horizons is completed and provides a structural framework within which to look at production and reservoir development. The sequence framework is complete within and immediately between the two fields and provides a basis for examining hydrocarbon occurrence and distribution. Structural slices of the seismic amplitude data volume have been completed at 4-ms intervals through the data, providing detailed maps of amplitude anomalies associated with quality reservoirs. The process of transforming the seismic attribute volume into a three-dimensional petrophysical volume is progressing, and the addition of an engineer in FY 2001 will initiate development of a fourth-order-level reservoir-flow model within a carefully chosen subset of the data volume.Bureau of Economic Geolog

Targeting reserve growth opportunities in the northern Gulf of Mexico Basin: transferring secondary gas recovery technology to the offshore environment Book 1

The Bureau of Economic Geology's Offshore Secondary Gas Recovery project is a multi-fiscal-year project funded by the U.S. Department of Energy, whose goal is to identify additional natural gas resources in a major field in the northern Gulf of Mexico Basin through multidisciplinary field and reservoir characterization study. Phases 1 and 2 of the project work plan (Project Preparation and Data Gathering and Loading, respectively) are nearly complete and scheduled to be completed by the end of October 1999. Phase 3 of the plan (Data Analysis) is well underway, and a list of preliminary leads is currently being compiled to convey to our industry partner. Reservoir tops have been spotted to facilitate production evaluation and recompletion opportunity. Key regional sequence surfaces have been identified in well logs and seismic, and mapping is being completed in the seismic dataset. Some of these surfaces have provided horizons to initiate a continuity processing of the seismic data volume for mapping depositional architecture. Well log interpretation of stacking patterns and systems tracts is well underway. Correlation surfaces have been compiled, and cross sections have been generated and interpreted for depositional elements. These data are being integrated with seismic data via Landmark® software. The project is on track within its projected timeframe, and additional personnel are being added as per the technical analysis plan. The key objective in the next fiscal year is to do the bulk of the technical analysis, focusing on generating a prioritized portfolio of infill and exploration prospects. Direct hydrocarbon indicator (DHI) modeling and analysis, continuity and impedance analysis, a general attribute interpretation of the seismic data, continued log-facies and parasequence interpretation, fault-seal analysis, and rigorous petrophysical analysis of well data are critical components of this objective.Bureau of Economic Geolog

The interactions of volcanism and clastic sedimentation in rift basins: Insights from the Palaeogene-Neogene Shaleitian uplift and surrounding sub-basins, Bohai Bay Basin, China

Although volcanism is an important process in the evolution of rift basins, current tectono-sedimentary models largely neglect its impact on sediment supply, transport pathways, and depositional systems. In this paper, we integrate core, well logs, and 3D seismic data from the Palaeogene-Neogene Shaleitian (SLT) uplift and surrounding sub-basins, Bohai Bay Basin, China, to investigate the sedimentology and geomorphology of a volcanic rift basin. Results of this study show that the spatial distribution of extrusive centres was strongly controlled by basement-involved intra-basin normal faults. During the early part of the syn-rift stage, the SLT uplift supplied sediments to transverse fan deltas and braided-river deltas that fringed the adjacent syn-rift depocentres. Volcanic deposits mainly occurred as relatively thin lava flow and pyroclastic facies that partially filled fault-controlled topographic lows, reducing topographic rugosity, and enhanced breaching of basement highs between syn-rift depocentres. Integration of drainage to the syn-rift depocentres and development of through-flowing axial depositional systems was enhanced. During the later part of syn-rift and in early post-rift stages, the SLT uplift was progressively inundated, reducing sediment supply to the fringing transverse depositional systems. In contrast, axial braided-river deltas became the main depositional systems, sourced by large hinterland drainage from the Yanshan fold-belt to the northwest. Volcanism in the late syn-rift and early post-rift occurs as thick lava flow and pyroclastic facies that infill rift topographic lows and locally blocked axial fluvial systems creating isolated lakes. Within hanging wall depocentres, volcanic topographic highs split and diverted axial fluvial and deltaic systems. Furthermore, volcanism supplied large volumes of volcanic sediment to the rift resulting in increased sedimentation rates, and the development of unstable subaerial and subaqueous slopes and deposits, increasing the occurrence of landslides. Based on the observations of this study we update tectono-sedimentary models for rift basins to include volcanism.publishedVersio

Sediment dispersal and redistributive processes in axial and transverse deep-time source-to-sink systems of marine rift basins: Dampier Sub-basin, Northwest Shelf, Australia

Morphological scaling relationships between source‐to‐sink segments have been widely explored in modern settings, however, deep‐time systems remain difficult to assess due to limited preservation of drainage basins and difficulty in quantifying complex processes that impact sediment dispersals. Integration of core, well‐logs and 3‐D seismic data across the Dampier Sub‐basin, Northwest Shelf of Australia, enables a complete deep‐time source‐to‐sink study from the footwall (Rankin Platform) catchment to the hanging wall (Kendrew Trough) depositional systems in a Jurassic late syn‐rift succession. Hydrological analysis identifies 24 drainage basins on the J50.0 (Tithonian) erosional surface, which are delimited into six drainage domains confined by NNE‐SSW trending grabens and their horsts, with drainage domain areas ranging between 29 and 156 km2. Drainage outlets of these drainage domains are well preserved along the Rankin Fault System scarp, with cross‐sectional areas ranging from 0.08 to 0.31 km2. Corresponding to the six drainage domains, sedimentological and geomorphological analysis identifies six transverse submarine fan complexes developing in the Kendrew Trough, ranging in areas from 43 to 193 km2. Seismic geomorphological analysis reveals over 90‐km‐long, slightly sinuous axial turbidity channels, developing in the lower topography of the Kendrew Trough which erodes toe parts of transverse submarine fan complexes. Positive scaling relationships exist between drainage outlet spacing and drainage basin length, and drainage outlet cross‐sectional area and drainage basin area, which indicates the geometry of drainage outlets can provide important constraints on source area dimensions in deep‐time source‐to‐sink studies. The broadly negative bias of fan area to drainage basin area ratios indicates net sediment losses in submarine fan complexes caused by axial turbidity current erosion. Source‐to‐sink sediment balance studies must be done with full evaluating of adjacent source‐to‐sink systems to delineate fans and their associated up‐dip drainages, to achieve an accurate tectonic and sedimentologic picture of deep‐time basins

Targeting Reserve Growth Opportunites in the Northern Gulf of Mexico Basin: Transferring Secondary Gas RecoveryTechnology to the Offshore Environment

The Bureau of Economic Geology's Offshore Secondary Gas Recovery program is a multi-fiscal year project funded by the U.S. Department of Energy, whose goals are to research new techniques and methods in defining the structure, stratigraphy, and hydrocarbon character in a mature area in the northern Gulf of Mexico and to utilize those multidisciplinary techniques and methods to identify additional gas resources, as well as predict regional trends in hydrocarbon accumulation. PHASES 1 and 2 of the project work plan (PROJECT PREPARATION and DATA GATHERING AND LOADING, respectively) have been completed. PHASE 3 of the plan (DATA ANALYSIS) is ongoing. All key chronostratigraphic surfaces have been mapped in logs, cross sections have been generated, and total thickness and is lith maps have been completed for all systems tracts in the reservoir units within the study area. Targets for resource additions have been identified and classed into target types, and preliminary resources have been calculated for these targets. Root-mean-squared amplitude maps have been used to better define opportunities within the internal architecture of larger stratigraphic features. Seven play types recognized within the study area have had their architecture and anatomy detailed. Previous work in the Offshore Gulf of Mexico (Hentz and others, 1997; Seni and others, 1997) defines the regional distribution of these same plays.Bureau of Economic Geolog

Targeting Reserve Growth Opportunities in the Northern Gulf of Mexico Basin: Transferring Secondary Gas Recovery Technology to the Offshore Environment

The Bureau of Economic Geology's Offshore Secondary Gas Recovery research program was a 4-year project funded by the U.S. Department of Energy. Its goals were to research new techniques in defining the structure, stratigraphy, and hydrocarbon character in mature areas in the northern Gulf of Mexico, to utilize those multidisciplinary techniques to identify additional gas resources, and to predict regional trends in hydrocarbon accumulation. By the latest estimates, Miocene-age strata of the northern Gulf of Mexico shelf are thought to contain 12.7 Tcf of remaining gas, representing 41 percent of the total remaining proven recoverable reserves. A study area was chosen in the Vermilion Block 50 and South Marsh Island Areas of offshore Louisiana. This area included two major producing fields, Starfak and Tiger Shoal, that provided more than 150 logging suites, detailed rock-property measurements, and whole and sidewall core, all of which were integrated with a high-quality 3-D seismic survey to construct a detailed sequence-stratigraphic framework for the study area. Analyses were done within the context of this framework for researchers to better understand stratigraphic and structural controls on resource distribution and to plan the pursuit of new opportunities.Bureau of Economic Geolog

The interactions of volcanism and clastic sedimentation in rift basins: Insights from the Palaeogene-Neogene Shaleitian uplift and surrounding sub-basins, Bohai Bay Basin, China

Although volcanism is an important process in the evolution of rift basins, current tectono-sedimentary models largely neglect its impact on sediment supply, transport pathways, and depositional systems. In this paper, we integrate core, well logs, and 3D seismic data from the Palaeogene-Neogene Shaleitian (SLT) uplift and surrounding sub-basins, Bohai Bay Basin, China, to investigate the sedimentology and geomorphology of a volcanic rift basin. Results of this study show that the spatial distribution of extrusive centres was strongly controlled by basement-involved intra-basin normal faults. During the early part of the syn-rift stage, the SLT uplift supplied sediments to transverse fan deltas and braided-river deltas that fringed the adjacent syn-rift depocentres. Volcanic deposits mainly occurred as relatively thin lava flow and pyroclastic facies that partially filled fault-controlled topographic lows, reducing topographic rugosity, and enhanced breaching of basement highs between syn-rift depocentres. Integration of drainage to the syn-rift depocentres and development of through-flowing axial depositional systems was enhanced. During the later part of syn-rift and in early post-rift stages, the SLT uplift was progressively inundated, reducing sediment supply to the fringing transverse depositional systems. In contrast, axial braided-river deltas became the main depositional systems, sourced by large hinterland drainage from the Yanshan fold-belt to the northwest. Volcanism in the late syn-rift and early post-rift occurs as thick lava flow and pyroclastic facies that infill rift topographic lows and locally blocked axial fluvial systems creating isolated lakes. Within hanging wall depocentres, volcanic topographic highs split and diverted axial fluvial and deltaic systems. Furthermore, volcanism supplied large volumes of volcanic sediment to the rift resulting in increased sedimentation rates, and the development of unstable subaerial and subaqueous slopes and deposits, increasing the occurrence of landslides. Based on the observations of this study we update tectono-sedimentary models for rift basins to include volcanism

Near the Brink: An Example of a Weak Layer in the Tuaheni Landslide Complex, Hikurangi Margin, New Zealand

International audienceWeak layers in submarine margins are often cited to explain landslide occurrence or reactivation, but little is known about the origin of these weak layers, and it is not always clear if the weak layer existed prior to the landslide or resulted from the failure process. IODP Expedition 372 logged, cored, and sampled Site U1517 to gain deeper insight into the interaction of gas hydrate and submarine landslides. Using physical data and core from Site U1517, we identify and characterize a weak layer in Tuaheni Landslide Complex (TLC) in the Hikurangi margin, New Zealand. The TLC is believed to behave in a creeping mode. We hypothesize that this weak layer could have been the result of deformation during failure (e.g., strength weakening) or the result of inherent weakness in the sediments. The identified weak layer in the TLC has an anomalous reduction in shear strength, porosity, and permeability that cannot be attributed to normal consolidation or composition changes. Furthermore, this weak layer could act as a potential slip plane for future creeping (i.e., reactivation) in the presence of a minor change in the stress or pressure field (e.g., earthquake). Based on scanning electron microscopic imaging of core samples, we conclude that the properties in the weak layer could be the result of mechanical rearrangement of clay particles that form “clay bridges” around framework grains. The measured low strength of the weak layer is approximately equal to the downslope gravitational stresses suggesting that the landslide is at or near failure— which may explain the creep-like behavior attributed to this landslide. Based on the physical properties from the TLC, we estimate the factor of safety and run numerical simulations using Plaxis software. We finally create sensitivity analysis to test likely scenarios that could reactivate this landslide. This study and methodology are relevant for many other underwater margins around the world where submarine landslides may be at or near the brink of failing