Regional 2D Seismic Lines Research Articles

New insights into the structural and stratigraphic evolution of the Malay Basin using 3D seismic data: Implications for regional carbon capture and storage potential

AbstractThe Malay Basin is a mature hydrocarbon province currently being re‐assessed for CO2 storage. Selecting an appropriate storage site requires a comprehensive understanding of the structural and stratigraphic history of the basin. However, previous studies have been limited to observations from either regional 2D seismic lines or individual 3D seismic volumes. In this study, we access and utilise a basin‐wide (ca. 36,000 km2) 3D seismic and well database to describe the structural and stratigraphic features of the basin, particularly those within the uppermost ca. 4 km (Oligocene to Recent) and gain new insights into the basin's evolution. E–W transtensional rift basins first developed due to sinistral shear across an NW‐SE strike‐slip zone. The NW‐SE basin morphology seen today was generated during the late Oligocene–early Miocene, during which time dextral motion across marginal hinge zones created en‐echelon antithetic, extensional faults and pull‐apart basins, especially well preserved along the western margin of the basin. Collisional forces to the southeast during the early to middle Miocene resulted in the shallowing of the basin, intermittent connection to the South China Sea and a cyclic depositional pattern. Around 8 Ma (late Miocene), a significant uplift of the basin resulted in a major unconformity with up to 4.2 km of erosion and exhumation in the southeast. In the centre and northwest of the basin, the inversion of deeper E–W rifts resulted in the folding of Miocene sequences and the formation of large anticlines parallel to the rift‐bounding faults. The Pliocene to Pleistocene history is more tectonically quiescent, but some extensional faulting continued to affect the northwest part of the basin. Larger glacio‐eustatic sea‐level fluctuations during this time resulted in major changes in sedimentation and erosion on the Sunda Shelf, including the formation of a middle‐Pliocene unconformity. These structural events have created a variety of hydrocarbon traps across the basin of different ages, including transpressional anticlines, rollover anticlines and tilted fault blocks. Each of these has discrete and distinct trap elements with important implications for their CO2 storage potential.

Petroleum System Modeling of a Fold and Thrust Belt: A Case Study from the Bannu Basin, Pakistan

This study focused on analyzing the petroleum system of the Bannu Basin, which is the foreland basin of the Himalayan fold and thrust belts in Pakistan. The objectives of this study were achieved by dividing the study area into three zones, namely, the Southwestern zone, Southeastern zone, and Northeastern zone. The regional 2D seismic lines and well log data, including the bore hole temperature (BHT) and petrophysical and geochemical data, were integrated. The seismic interpretations and geohistory plots indicate higher levels of sedimentation and abrupt sedimentation from the Miocene until the Recent era due to the initiation of Himalayan orogeny. The thermal modeling indicates that potential source rocks are present in the basin, whereas the local faults in the Southwestern and Southeastern zones act as potential traps for the preservation of hydrocarbons. It is assumed that the Tredian Formation and Lumshiwal Formation are the potential reservoir rocks in the Southwestern zone, whereas the Warcha Formation and Tredian Formation are the economic reservoirs in the Southeastern zone. However, in the Northeastern zone, no major accumulation is present. The significant sedimentation of post-Miocene formations was the major event for the generation of hydrocarbons and a critical moment for the accumulation of hydrocarbons in the study area.

Tectono‐stratigraphic evolution of the rift and post‐rift systems in the Northern Campos Basin, offshore Brazil

AbstractThe Campos and Santos Basins have been a focus of subsurface studies since the discovery in 2006 of large accumulations of hydrocarbons in the Early Cretaceous rift and post‐rift strata below Aptian evaporites. In this study, regional 2D seismic lines, a 3D seismic survey and well data were interpreted to reconstruct the tectono‐stratigraphic evolution of the rift and post‐rift stages in the northern sector of the Campos Basin. Detailed 3D seismic interpretation and geological modelling were used to subdivide the pre‐salt sedimentary record. This revealed a diachronous strain distribution along the Guriri Fault System (GFS), a roughly NE‐SW striking fault‐bounded horst that was a focus of rift‐related deformation. The syn‐rift succession is interpreted to be the product of two episodes of rifting (RP1 and RP2) with contrasting fault activity patterns and lithostratigraphy. Volcaniclastics and coarse siliciclastics of RP1 were deposited under WNW‐ESE transtension that formed discontinuous half‐grabens followed by extensive erosion and tectonic inversion. Structurally controlled bioclastic rudstones and hybrid deposits characterize RP2 and were deposited in elongated half‐grabens that delimit the GFS horst, which developed under an NW‐SE extension. Deposition under increasingly less tectonically active transitional and post‐rift stages dominated by thermal subsidence gradually led to the healing of the rift‐related structural relief. Selective reactivation of rift faults testifies active tectonic inversion through compression from immediate post‐rift throughout evaporite deposition. These interpretations are put into the context of recent geochronological data of onshore dyke emplacement and the new age constraints for the end of deposition of the pre‐salt sequence. Therefore, we propose an earlier onset on rifting in the Campos Basin, at the Berriasian.

Crustal structure of the central sector of the NE Brazilian equatorial margin

Abstract The central equatorial Brazilian margin is divided into the Amazon and Barreirinhas divergent segments separated by the Pará-Maranhão transform segment. Analysis of regional 2D seismic lines allowed the definition of the crustal architecture of the margin. In the study area, the Barreirinhas segment has a proximal domain with a 30–35 km-thick continental crust, a 20–40 km-wide necked domain where the crust thins to 10 km, and an outboard domain with hyperextended continental crust. The Pará-Maranhão and Amazon segments consist of exhumation domains and their transition to ocean crust. Their structural styles indicate that this is a magma-poor passive margin with oceanic crust formed in a slow spreading centre. The Pará-Maranhão segment is bounded by two branches of the Saint Paul Fracture Zone that displace crustal domains with structures that document the transition from the distal part of a transform margin to an oceanic fracture zone. Two groups of post-rift volcanic complexes have been identified in the exhumation and oceanic domains, and whose distribution is controlled by the fracture zones. Late Cretaceous–Recent gravitationally-driven slide systems and mass-transport deposits indicate long-lived margin collapse and sediment redistribution fundamentally controlled by the underlying crustal structure of this part of the northeastern Brasilian passive margin.

Evolution of “Tres Hombres” - A Mid-crustal Dome Structure within the Jurassic Northern Beagle Sub-basin Western Australia: An Integrated Geophysical Investigation

The Tres Hombres structure is a large mid-crustal structural feature that that underlies the Permian – Late Jurassic mega-sequences of the Northern Beagle Sub-basin, Western Australia. Originally identified on regional 2D seismic lines, the Tres Hombres structure has now, for the first time, been fully imaged by high quality, deep record modern 3D seismic data. The area is also covered by gravity and magnetic datasets which were acquired together with the 3D seismic survey. Seismic mapping reveals a dome-like structure with a diameter of more than 30km, and with vertical relief of over 5km. This paper integrates seismic and potential fields datasets to explore the origins of this intriguing structure. Mechanisms considered for the emplacement of this feature include; basement cored compression, reactivated extensional basement faulting, remnant Palaeozoic topographic relief, salt-related diapirism, or plutonic/igneous intrusive activity. The actual mechanisms responsible for the evolution of Tres Hombres have obvious implications for adjacent and overlying petroleum systems within the Beagle Sub-basin. Detailed mapping of new 3D seismic datasets enables structural and stratigraphic restorations to be generated, which provide valuable insights into the timing of the Tres Hombres feature. Variations in the thicknesses of overlying sequences show the influence that this structure had on the stratigraphic evolution of the basin. Gravity and magnetic datasets have also been integrated into this study, and provide valuable controls on potential lithologies within the core of the Tres Hombres feature. These in turn have important implications as to the origin of this structure, and relationships to the tectonic evolution of the Beagle Basin.

The Stratigraphic Architecture, Distribution and Hydrocarbon Potential of the Organic Rich Kyalla and Velkerri Shales of the Upper Roper Group (McArthur Basin)

Recent exploration studies on the stratigraphic framework, depositional environment and tectonic setting of the Mesoproterozoic Roper Group in the McArthur Basin, have led to an improved understanding of the highly prospective organic-rich shales of the Velkerri and Kyalla Formations. From a review of open file drill core and well logs, several major regressive-transgressive (R-T) cycles have been identified within the Roper Group. The R-T cycles show sedimentary features typical of deposition within a clastic dominated marine deltaic setting and show marked lateral variation in facies and thicknesses. The lateral thickness variations are particularly noticeable across regional 2D seismic lines. Seismic interpretation and well correlation confirm the extensive and relatively undeformed nature of the Velkerri and Kyalla Formations in the subsurface, they appear thickest in the southeast of the Greater Beetaloo Basin.

The stratigraphic architecture, distribution and hydrocarbon potential of the organic-rich Kyalla and Velkerri shales of the Upper Roper Group (McArthur Basin)

Recent exploration studies on the stratigraphic framework, depositional environment and tectonic setting of the Mesoproterozoic Roper Group in the McArthur Basin, have led to an improved understanding of the highly prospective organic-rich shales of the Velkerri and Kyalla Formations. From a review of open-file drill core and well logs, several major regressive–transgressive (R–T) cycles have been identified along with four key facies associations within the Roper Group. The R–T cycles show sedimentary features typical of deposition within a clastic-dominated marine deltaic setting and show marked lateral variation in facies and thicknesses. The lateral thickness variations are particularly noticeable across regional 2D seismic lines. Seismic interpretation and well correlation confirm the extensive and relatively undeformed nature of the Velkerri and Kyalla Formations in the subsurface, they appear thickest in the south-east of the Beetaloo Sub-Basin.

3D seismic analysis of gravity-driven and basement influenced normal fault growth in the deepwater Otway Basin, Australia

We use three-dimensional (3D) seismic reflection data to analyse the structural style and growth of a normal fault array located at the present-day shelf-edge break and into the deepwater province of the Otway Basin, southern Australia. The Otway Basin is a Late Jurassic to Cenozoic, rift-to-passive margin basin. The seismic reflection data images a NW-SE (128–308) striking, normal fault array, located within Upper Cretaceous clastic sediments and which consists of ten fault segments. The fault array contains two hard-linked fault assemblages, separated by only 2 km in the dip direction. The gravity-driven, down-dip fault assemblage is entirely contained within the 3D seismic survey, is located over a basement plateau and displays growth commencing and terminating during the Campanian-Maastrichtian, with up to 1.45 km of accumulated throw (vertical displacement). The up-dip normal fault assemblage penetrates deeper than the base of the seismic survey, but is interpreted to be partially linked along strike at depth to major basement-involved normal faults that can be observed on regional 2D seismic lines. This fault assemblage displays growth initiating in the Turonian-Santonian and has accumulated up to 1.74 km of throw.Our detailed analysis of the 3D seismic data constraints post-Cenomanian fault growth of both fault assemblages into four evolutionary stages: [1] Turonian-Santonian basement reactivation during crustal extension between Australia and Antarctica. This either caused the upward propagation of basement-involved normal faults or the nucleation of a vertically isolated normal fault array in shallow cover sediments directly above the reactivated basement-involved faults; [2] continued Campanian-Maastrichtian crustal extension and sediment loading eventually created gravitational instability on the basement plateau, nucleating a second, vertically isolated normal fault array in the cover sediments; [3] eventual hard-linkage of fault segments in both fault arrays to form two along-strike, NW-SE striking fault assemblages, and; [4] termination of fault growth in the latest Maastrichtian. We document high variability of throw along-strike and down-dip for both fault assemblages, thereby providing evidence for lateral and vertical segment linkage. Our results highlight the complexities involved in the growth of both gravity-driven normal fault arrays (such as those present in the Niger Delta and Gulf of Mexico) and basement-linked normal fault arrays (such as those present in the North Sea and Suez Rift) with the interaction of an underlying and reactivating basement framework. This study provides an excellent example of spatial variability in growth of two normal fault assemblages over relatively short spatial scales (∼2 km separation down-dip).

Introducing the Sylvester Graben, a ?Neoproterozoic depocenter on the eastern flank of the Toko Syncline, southern Georgina Basin, Queensland

Regional 2D seismic lines acquired in 2013 along the eastern edge of the Toko Syncline in Queensland have imaged a complexly faulted, northwest–southeast trending graben below subcropping Cambrian carbonates. At its deepest, this depocenter contains some 3,500 m of sediments that are inferred to be of Neoproterozoic age, if not older at depth. Surface outcrops of this succession are mapped as the Sylvester Sandstone. Shallow core holes confirm that the uppermost ~1,000 m of sediments are of fluvioglacial, glacio lacustrine and glacial origin, overlain by a thin carbonate of Lower Cambrian age based on the occurrence of archaeocyathids. Unconformably underlying this succession is an internally reflective sedimentary section that is up to 2,500 m which has not been drilled to date. Although the localised development of Neoproterozoic depocenters below Cambrian carbonates in the Toko Syncline has been inferred previously based on vintage seismic and gravity data, such features were not imaged as clearly as on the newly acquired seismic. Inferred sediments in this faulted graben may be correlatives of the Neoproterozoic succession in the Amadeus Basin and could be prospective for hydrocarbons as well as ore deposits.

Structural and stratigraphic evolution of the Connemara discovery, Northern Porcupine Basin: significance for basin development and petroleum prospectivity along the Irish Atlantic Margin

ABSTRACT A detailed seismic stratigraphic interpretation of a previously unpublished, well-calibrated 3D seismic volume and regional 2D seismic lines in the Northern Porcupine Basin, west of Ireland has provided significant insights into the basin development, sedimentary fill and petroleum prospectivity within this area of the Irish Atlantic continental margin. The results of the seismic interpretation presented here provide a detailed description of the evolution of the Connemara discovery and have resulted in a revised model for the tectonic development and stratigraphic evolution of the fault block structure containing the oil accumulation. The new seismic stratigraphic analysis also provides the basis for an alternative interpretation of Early Cretaceous ‘clinoform’ features based on the results of the 3D seismic interpretation which supports a genesis through structural rotation of onlapping horizons rather than depositional downlap favoured by previous interpretations. This new-found structural and stratigraphic understanding not only has significant implications for determining the main controls on the Connemara discovery, but also provides a basis upon which to place other prospective structures in their regional context, including the identification and risking of exploration plays and prospects in the area.

Athabasca oil sands: reservoir characterization and its impact on thermal and mining opportunities

Abstract The heavy oil deposits of Canada are a large resource with an estimated 1.7×10 12 barrels of bitumen in place. The Lower Cretaceous McMurray Formation in the Athabasca area of northern Alberta contains about 900×10 9 barrels of bitumen in place. This resource can be developed through surface mining and thermal in situ techniques. This paper examines the size of this resource in a global context and highlights its position relative to the North American market. The regional geology of the Western Canada Sedimentary Basin and the Athabasca area will also be reviewed. Understanding the regional reservoir distribution of the McMurray Formation is critical to understanding oil sands opportunities. Fluvial estuarine point bar reservoirs are a large portion of the resource that can be developed. Examples will be shown from the type outcrop location, where the stratigraphy can be organized into a hierarchy that subdivides channel-fills into bedsets, storeys, bars and barsets. Inclined heterolithic strata (IHS) surfaces can be identified. Considerable resource delineation drilling has occurred in the basin. The regulator for the Athabasca area specifies minimum drilling densities before project approvals are granted. Regional 2D seismic lines and project-specific 3D and 4D seismic datasets have also been acquired, to reduce the reservoir uncertainty and improve resource definition in this complex depositional environment. These techniques provide a unique opportunity to analyse a complex depositional system with abundant well and core control, outcrop data and seismic information. To determine preliminary deposition environments, software techniques have been successfully used to interpret large datasets quickly. Laser imaging of mine faces has also been used to record stratigraphy and determine the mined volume of ore. The importance of detailed reservoir characterization studies and their impact on thermal in situ recovery mechanisms will also be discussed. Understanding reservoir facies distributions and lateral relationships affects any recovery process, but has an even greater significance in a heavy oil reservoir.