Seismic Geomorphological Analysis Research Articles

3D seismic geomorphological analysis of Eocene to Miocene depositional system transition and background tectonics in the Sanriku-oki forearc basin: changes from bay head deltas, continental rivers to deep marine slopes caused by unconformity events

3D seismic geomorphological analysis of Eocene to Miocene depositional system transition and background tectonics in the Sanriku-oki forearc basin: changes from bay head deltas, continental rivers to deep marine slopes caused by unconformity events

Seismic geomorphological analysis of deepwater gravity-driven deposits on a slope system of the southern Colombian Caribbean margin

Gravity-driven processes are important agents for transporting sediments downslope into deep-marine environments. The Pliocene to Holocene offshore succession of the Colombian Caribbean margin and its stratigraphic distribution, have been affected by faulting and mud diapirism, and have been characterized using 3D seismic data. Nine stratigraphic intervals were characterized within the study, and are interpreted to consist of a range of seismic geomorphologies, including slumps and debrites. Nine gravity-driven deposits were defined within the study area, interpreted to have been transported to the north and northwest. Slumps display high-amplitude, high continuity, elongated, stratified, lobate and confined morphologies, while debrites have a reflection-free pattern or show discontinuous, low-amplitude and chaotic reflections. Mixed slumps-turbidites-debrites deposits are composed by a succession of laterally and vertically interfingered slumps, debrites and turbidites. These deposits are morphologically lobate and broadly scattered. In addition, erosional features such as basal small scours, megascours, linear scours and rafted blocks were used as kinematic indicators within the gravity-driven deposits. There are several candidates triggering mechanism, including over-steepening of slope (related to high sediment supply or slope tectonism). In the study area, confined slumps and debrites with a main transport direction from south to north have been observed, while transport direction of the mixed slumps-turbidites-debrites was toward northwest. Additionally, the fact that slumps and debrites are found in depocenters between periclines suggests a confined environment of deposition. Finally, mixed slumps-turbidites-debrites are unconfined without evident structural control. We suggest that local intraslope sub-basin margin become over-steepened as a result of mud diapirism in the subsurface. In this situation, the paleobathymetry was sufficient to trap the resultant gravity-driven deposits within the sub-basins, suggesting a local origin. Seismic evidence of BSR (Bottom Simulating Reflector) suggests the presence of gas hydrate in the study area, and is taken as an additional potential mechanism to provide instability of slope and generate gravity-driven deposits.

Seismic geomorphological analysis and hydrocarbon potential of the Lower Cretaceous Cromer Knoll Group, Heidrun field, Norway

The Heidrun field, located on the Halten Terrace of the mid-Norwegian continental shelf, was one of the first giant oil fields found in the Norwegian Sea. Traditional reservoir intervals in the Heidrun field lie within the Jurassic synrift sequence. Most Norwegian continental shelf fields have been producing from these Jurassic reservoirs for the past 30 yr. Production has since declined in these mature fields, but recently, exploration for new reservoirs has resurged in this region. The Jurassic rifted fault blocks form a narrow continental shelf in Norway, thereby greatly reducing the areal extent for exploration and development within existing fields. As the rift axis is approached farther offshore, these Jurassic reservoirs become very deep, too risky to drill, and uneconomical. This risk has prompted exploration in more recent years of the shallower Cretaceous, postrift stratigraphic succession. Cretaceous turbidites have been found in the Norwegian and North Seas, and the discovery of the Agat field in the Norwegian North Sea confirms the existence of a working petroleum system capable of charging Cretaceous reservoirs. These Cretaceous reservoirs were deposited as slope- and basin-floor fans within a series of underfilled rifted deeps along the Norwegian continental shelf and are thought to be sourced from the localized erosion of Jurassic rifted highs. We use three-dimensional seismic and well data to document the geomorphology of a deep-water, Lower Cretaceous wedge (Cromer Knoll Group) within the hanging wall of a rift-related half graben formed on the Halten Terrace offshore mid-Norway. Seismic attribute extractions taken within this Lower Cretaceous wedge reveal the presence of several lobate to elongated bodies that seem to cascade over fault-bounded terraces associated with rifted structures. These high-amplitude, elongated bodies are interpreted as deep-water sedimentary conduits that are time equivalent to the Cretaceous basin-floor fans in more distal parts of the basin to the west. These half-graben fills have the potential to contain high-quality Cretaceous sandstones that might represent a potential new reservoir interval within the Heidrun field.

東部南海トラフ海域のメタンハイドレート探査における堆積学的手法の適用

An integrated sedimentological workflow was applied to the methane-hydrate exploration project in the eastern Nankai Trough area, central Japan, as a useful tool to investigate the distributions and actual volume of methane hydrates. Since previous research revealed that most of the methane hydrates in the eastern Nankai Trough area occur in matrix pores of submarine-fan turbidite sandstones, the facies distribution of turbidite sandstones may be one of the important keys to evaluate the occurrence of methane hydrates. Accordingly, this study conducted a) core facies analysis, b) log facies analysis mainly using FMI, c) depositional sequence division, d) seismic facies analysis on the 2D/3D seismic sections, and e) seismic geomorphological analysis on the 3D seismic survey data to map submarine-fan turbidite facies distributions for 17 depositional sequence horizons in the targeted Pleistocene interval. The obtained facies maps reveal that submarine-fan depositional styles changed throughout Pleistocene from a braided channel type, through small radial fan, trough-fill fan, and muddy sheet fan types, to a channel-levee system type. As the next step, the facies maps of each depositional sequence were overlaid with bottom simulating reflector (BSR) distributions as a proxy of methane hydrates. The overlaid maps indicate that the BSRs occur on feeder channels, distributary channels, and proximal lobes of submarine fans, suggesting that methane hydrates selectively occur in coarser grained portions of a submarine fan. The facies maps were also used for calculation of average net-to-gross ratio of the methane hydrate occurrence zones, as the maps provide information on the spatial distributions of seismic facies class, which has individual value of net-to-gross ratio. Finally, this study analyzed reservoir-scale geologic bodies, such as depositional lobes and braided channels of a submarine fan, using 3D seismic survey data, and constructed a detailed geologic model for simulations of methane-hydrate generation and production.

三次元サイスミック地形学 (seismic geomorphology) 手法による貯留層のイメージングと分布解析

This paper attempts to review the historical background, petroleum geological significance, major contributions and basic methodology of “seismic geomorphology”, which has recently been developed as an integration of 3D seismic technology/3D visualization technique and sedimentology/sequence stratigraphy. Seismic geomorphology may be defined as the study of sediment body morphology and properties using 3D seismic data, and is expected to be indispensable for future sedimentology and hydrocarbon exploration/development, since seismic geomorphology provides detailed information on the sediment morphology, distributions and depositional processes. From the sedimentological aspect, seismic geomorphology clarifies detailed internal structures of depositional elements, and improves general depositional models of various depositional systems. From the petroleum geological aspect, seismic geomorphology plays an important role to bridge over sedimentology, geophysics and reservoir engineering in an integrated reservoir characterization workflow.In a seismic geomorphological analysis procedure, basic sequence stratigraphic framework should be constructed, first, and reconnaissance survey over 3D seismic data should be conducted, next. Subsequently, targeted reservoir rock bodies are displayed in detail by slicing, horizon surface displaying, volume attribute analysis and trace shape (seismic facies) analysis on the 3D seismic data. Finally, sedimentological interpretation is conducted for the displayed sediment body to determine depositional elements, processes and facies distributions. It is regarded that proper pattern recognition and blend of spatial seismic geomorphology and temporal seismic stratigraphy are the keys to obtain effective solutions in the seismic geomorphological analysis.

Clastic depositional systems at the base of the late Miocene evaporites of the Levant region, Eastern Mediterranean

Abstract This study investigates the evidence for the presence of clastic sediments at the base of the distal Messinian evaporites in the Levant region (Eastern Mediterranean). Seismic geomorphological analysis of three-dimensional seismic data clearly reveals the occurrence of a well-imaged clastic body composed of two closely spaced channel-mouth lobe deposits, within the basal part of the Messinian evaporites. Comparable seismic facies observed at the same stratigraphic level point to the occurrence of additional clastic deposits and allows their correlation with the El Arish and Afiq canyon systems. The seismic characteristics of the clastic bodies and the analogy with other coeval deposits in the Mediterranean Basin suggest that they deposited in a submarine (shallow- or deep-water) setting. Knowledge of the occurrence and distribution of these clastic deposits has considerable impact on the interpretation of the depositional environment of this basinwide evaporitic system.