Carbon capture and storage (CCS) is an essential technology that will play a major role in transitioning toward net-zero carbon emissions. CCS is the only group of technologies that reduces emissions in key energy and industrial sectors directly but also reduces CO2 to balance emissions in sectors difficult to abate. Offshore CCS offers most of the CO2 storage opportunities to achieve the growth required in storage capacity beyond the feasible onshore storage. Geomechanical screening of potential CCS sites for safe and efficient CO2 injection in deep geological formations is still a substantial challenge, especially over large areas with hundreds of drilled structures and fields, such as the shallow water Gulf of Mexico (GOM). In this study, we collect existing geophysical and petrophysical logs, drilling data (e.g., mud weight, leak-off test), pore pressure (MDT) and temperature data from 123 wells to evaluate potential CO2 leakage via the caprock due to gas injection-induced fault reactivation or fracturing. For this, we develop pore pressure and 1D mechanical Earth models for six wells, strategically distributed throughout the study area with all the required data, and map Shear Stress Levels (SSL) and Pressure Rooms (PR) for all potential storage formations. We further develop stress polygons based on friction equilibrium and poroelastic failure criteria for gas injection-induced shear failure. We characterize the contemporary state of stress in GOM by normal faulting (NF) stress, which is consistent with the predominantly extensional regime in the western intraplate North America. Using the World Stress Map (WSM) database, we find a mean SH orientation of N98° (±47°) based on 79 borehole breakouts with an overall length of 1241 m in 23 offshore wells in GOM. Stress orientations are locally affected by salt bodies and faults. We observe a pore pressure transition from hydrostatic at a shallow depth (i.e., wide PR) to an extreme overpressure zone (i.e., narrow PR), which makes deep reservoirs more sensitive to tensile fracturing during CO2 injection. We show that SSL is less than 0.4 in all reservoirs and seals in the GOM area, and PR decreases northwest of the study area. Furthermore, we reveal that the critical pressure and temperature limits for shear failure are far beyond the PR limit. Hence, following the PR limit, gas injection-induced reservoir failure and fault reactivation is unlikely in the study area, providing confidence that caprock mechanical leakage is a low-risk issue for long-term CO2 storage.

Abstract A tectono-stratigraphic analysis of a broadband 3D seismic survey over the outer slope of Côte d'Ivoire margin, west Africa, revealed that Cenomanian and younger strata seal well-developed rift fault blocks up to 15 km across. Growth strata indicate that these were formed during rifting that culminated in seafloor spreading in the late Albian, challenging existing plate reconstructions for the opening of the equatorial Atlantic ocean. A previously unrecognized system of volcanic edifices linked at depth to a network of sill complexes has also been identified. These are aligned along a NE–SW trend, concordant with kilometre-wide ridges, interpreted as folds formed by steep, crustal faults with an oblique-slip component. These trends are similar to those of fracture zones in the region and indicate that the Côte d'Ivoire was a transform margin in the late Albian. These results highlight the potential of offshore Côte d'Ivoire for deep-water rift plays with large traps formed by extensional fault blocks together with prospective Albian reservoirs ponded in their hanging walls. In addition, the volcanoes and ridges generated seabed relief along the newly created transform margin, forming confined basins for potential deposition of Turonian and younger turbidites and the generation of stratigraphic traps.

Abstract The Timor Orogen comprises the island of Timor, a narrow offshore area to the north and a wider offshore fold-and-thrust belt to the south. This orogen formed by jamming and subsequent collision of the Banda Sea subduction system by the Australian Plate. The BandaSeis seismic survey has revealed excellent images of the deep-water fold-and-thrust belt. Seismic interpretation of the dataset demonstrated structural and tectonic features not previously described, including regional geological features on the Australian continental crust and two regional NE–SW sinistral strike-slip faults, and a prominent Middle Permian palaeogeographical high (Timor Plateau). Moreover, since the Middle–Late Triassic and Middle Jurassic, the two NE-trending strike-slip faults governed the formation of the West Timor and Cova-Lima sub-basins. The location along the Australian margin plays a dominant role in controlling the structural style and shaping of the Timor Orogen. Vertical loading and the southerly motion of the orogenic wedge are the main driving forces responsible for its building, illustrating a thin-skinned tectonic framework. Thrust faults nucleate in a forward-breaking sequence in the motion of thrust transport, with younger thrusts developing in front of older thrusts. Most of the collisional deformation has been classified into two styles: shallow thin-skinned and deep-seated deformation.

The complicated geology of the Banda region results from complex collision between the Eurasia, Australia and Pacific plates, ongoing in the region since the Late Oligocene but particularly in the study area since the Middle Miocene (from 15 Ma). Regional 2D broadband seismic data have provided improved imaging of Mesozoic and Cenozoic sedimentary successions in the region. The region comprises the deep and ultra-deep Banda Sea enclosed by a magmatic inner arc and an outer deformed zone, comprising a series of orogens. This outer orogenic zone comprises islands with extended and sometimes hyperextended continental crust, a series of marginal foredeeps and intervening fold-and thrust belts. This paper illustrates how the offshore fold-and-thrust belts that bound the fore-deeps change in size, shape and degree of basement reactivation in a clockwise sense around the Banda Arc.

Having produced oil since 1957, Gabon has several proven petroleum systems, both onshore and offshore. Over the last decade interest has moved towards the deep offshore area where a number of early exploration wells have been successful in finding hydrocarbons, but also highlighted the need to answer questions about trap formation, source maturation and timing of charge in this new area. Following this exploration trend, and aiming to answer these key questions, a recent 3D broadband seismic survey was acquired in conjunction with shipborne gravity and magnetic data in the southern deep offshore area of Gabon. Understanding the tectonic evolution of the basin and its impact on the petroleum systems, requires the integration of seismic with the concurrently acquired gravity and magnetic data. Potential fields data provide deep crustal information where it may be challenging for seismic to resolve deep geological features, and vice versa for the shallower sedimentary section. One of the key objectives of the potential fields study was to model crustal types and thicknesses for input into basin modelling. Upper and lower crust ratios, as well as the crustal characteristics and processes in the continental-oceanic transition zones, are important for understanding the temperature regimes undergone by potential source and reservoir rocks. Knowing the distribution of lower- or higher-density crust, and zones of higher susceptibility, provides insight into the characteristics and timing of formation/deformation of the crust along the margin.

By combining sea surface seep data derived from synthetic aperture radar imagery and 2D seismic acquired by CGG’s Multi-client New Ventures, a seeps to seismic workflow has been developed which allows the linking of interpreted surface seeps with features on the seabed and within the subsurface related to seepage. The project combines these data sources in order to create hotspot maps which describe the quality and frequency of these seep related features, be it direct hydrocarbon indicators, possible migration pathways, fluid escape features or seabed features. By combing these maps with the surface seeps, localised points of hydrocarbon generation, migration and escape are able to be identified. 3D modelling software is utilised to link these hot spots within the seismic along strike and identify the most important and continuous structures. By identifying and understanding the geology where hydrocarbons are reaching the surface it is possible to better identify potential locations where the same hydrocarbons may instead be properly trapped. This allows the efficient identification of prospects within a basin.

Velocity model building is one of the most difficult aspects of the seismic processing sequence. But it is also one of the most important: an accurate earth model allows an accurate migrated image to be formed, which allows the geologist a better chance at an accurate interpretation of the area. In addition, the velocity model itself can provide complementary information about the geology and geophysics of the region. Full-waveform inversion (FWI) is a popular, high-end velocity model-building tool that can generate high-resolution earth models, especially in regions of the model probed by the transmitted (diving wave) arrivals on the recorded seismic data. The history of the South Gabon Basin is complex, leading to a rich geologic picture today and a very challenging velocity model-building process. We have developed a case study from the offshore Gabon area showing that FWI is able to help with the model-building process, and the resulting velocity model reveals features that improve the migrated image. The application of FWI is made on an extremely large area covering approximately 25,000 [Formula: see text], demonstrating that FWI can be applied to this magnitude of survey in a timely manner. In addition, the detail in the FWI velocity model aids the geologic interpretation by highlighting, among other things, the location of shallow gas pockets, buried channels, and carbonate rafts. The concept of actively using the FWI-derived velocity model to aid the interpretation in areas of complex geology, and/or to identify potential geohazards to avoid in an exploration context, is applicable to many parts of the world.

Recovering the remaining and bypassed hydrocarbons in mature areas requires well-informed decision-making supported by good data. A great deal of seismic exploration has taken place within the North Sea, using a variety of acquisition configurations including the latest broadband solutions. Most surveys in this mature area have been processed and reprocessed multiple times as techniques have evolved and, every so often, significant advances in technology warrant the application of these new approaches in a wholesale way. The Central North Sea (CNS) still contains many oppor¬tunities and is notoriously challenging to image with seismic. Fuelled by the need for greater accuracy of deep imaging and structural interpretation, for both prospect discovery and field development, there has been a steady increase in the number of pre-stack depth migration (PSDM) projects. The majority of these projects have focused on small areas, primarily restricted by the high work effort involved in integrating all available data (wells, horizons, vertical seismic profiles, etc.) into the velocity model, combined with the lengthy timescales required to update the model using traditional, interpretation-heavy workflows and tomography methods. Recent advances in multi-layer tomography (Guillaume et al., 2012) now allow us to complete complex PSDM projects within a significantly reduced timescale while at the same time achieving improved image quality. In addition, advances in deghosting and demultiple processing technolo¬gies have enabled us to extract even more value from vintage conventional flat-towed streamer datasets. We describe how these technologies have been applied to integrate 37 acquisi¬tion phases covering more than 35,000 km2 in the CNS to generate a unique and contiguous high-quality broadband PSDM dataset which sets new standards for regional datasets in mature basins.

A new regional 2D seismic survey was completed in Timor-Leste water in 2014 using CGG’s BroadSeis technology. Early geological interpretation of these broadband data shows tremendous seismic image improvements revealing new information about the subduction margin. The additional low frequencies penetrate deep below the Timor Island accretionary prism to image what happens to the subducted Australian Plate. Furthermore, good quality high frequencies have enabled geologists to interpret in greater detail the Triassic-Holocene section of the Australian plate along with the inner structure of the Timor Island accretionary wedge. Deep beneath the accretionary prism, the seismic data reveal the behaviour of horsts and grabens from the Australian Plate under-going subduction. We observe a general thinning of the Mesozoic section towards the NE leading to think there was a prevalent monocline ramp in Late Permian. In addition, a large normal fault trending NNW-SSE with up to 2300m vertical offset splits the Timor-Leste offshore in two distinct sub-basins. This fault bounds the SW flank of a regional paleo-high, which was clearly active during Cretaceous times with visible thickening of the sediments in the hanging wall. This paleo-high probably acts as an obstacle for subduction giving rise to collision-like features at depth such as inverted faults and thrust duplexes below the regional decollement. Spatial relationship between the overriding and subducting plates suggests uplift and isostatic rebound due to slab detachment also proved by P-wave tomography models. These observations have multiple implications on the potential existence of petroleum systems in the Timor-Leste Offshore acreage.

Boosted by recent discoveries, Côte d’Ivoire has seen renewed interest in its deepwater offshore basin over the last few years. Up until 2011, not a single well had been drilled beyond the 2,000m water depth line of Côte d’Ivoire, but ten wells have been drilled over the last three years. Several technical discoveries, which are not necessarily commercial for the time being, were made, including Saphir in Block CI-514, Morue in Block CI-516, Buffalo in Block CI-205, Paon/ Autruche in Block CI-103, Ivoire in Block CI-100 and Capitaine East in Block CI-101 (Figure 2). Nearer shore, the basin has been explored since 1972 when the first offshore well IVCO-1 was drilled. Subsequent discoveries were made that highlighted the presence of a working hydrocarbon system in the Lower Cretaceous syn-rift/transition sequence, but it was not until the new play-opener Jubilee discovery in 2007, found in What Lies Beneath the Deepwater Tano Basin?

PreviousNext No Access13th International Congress of the Brazilian Geophysical Society & EXPOGEF, Rio de Janeiro, Brazil, 26–29 August 2013Offshore solutions: Brazil broadband case studyAuthors: Jaswinder MannGregor DuvalJaswinder MannCGGSearch for more papers by this author and Gregor DuvalCGGSearch for more papers by this authorhttps://doi.org/10.1190/sbgf2013-008 SectionsAboutPDF/ePub ToolsAdd to favoritesDownload CitationsTrack CitationsPermissions ShareFacebookTwitterLinked InRedditEmail Abstract This paper presents broadband seismic data acquired in the deep waters of the Santos Basin, using CGG's new curved variable depth streamer technology. A descriptive and illustrated account has been carried out from the multi-client Phase 6-B survey displaying the benefits of broadband data for seismic interpreters. Phase 6-B is located offshore in the Santos Basin and covers the post-salt Atlanta and Oliva discoveries. It extends over the Phase 6-A conventional survey area, which contains the multi-billion barrel oil field Libra. A shallow to deep approach is taken through the dataset demonstrating the benefits of broadband seismic data for the end-user. Comparison examples are taken from Phase 6-B (broadband, variable depth streamer data) and Phase 6-A (constant depth streamer). Keywords: South America, case history, seismic, shallow, stratigraphyPermalink: https://doi.org/10.1190/sbgf2013-008FiguresReferencesRelatedDetails 13th International Congress of the Brazilian Geophysical Society & EXPOGEF, Rio de Janeiro, Brazil, 26–29 August 2013ISSN (online):2159-6832Copyright: 2013 Pages: 2001 publication data© 2013 Published in electronic format with permission by the Brazilian Geophysical SocietyPublisher:Society of Exploration Geophysicists HistoryPublished Online: 09 Jan 2014 CITATION INFORMATION Jaswinder Mann and Gregor Duval, (2013), "Offshore solutions: Brazil broadband case study," SEG Global Meeting Abstracts : 34-37. https://doi.org/10.1190/sbgf2013-008 Plain-Language Summary KeywordsSouth Americacase historyseismicshallowstratigraphyPDF DownloadLoading ...