First EAGE Workshop on the Triassic and Jurassic Plays in Northwest Europe

For decades, the Triassic interval of the North Sea remained inadequately understood and, therefore poorly explored. This was due to the combination of structural, burial depth, overpressure, and sedimentological variability related primarily to the depositional environment, halokinesis, post-depositional erosion and diagenesis. In both UK and Norwegian sectors of the Central North Sea, the Triassic interval comprises the mainly Early Triassic Smith Bank Formation, represented by fluvio-lacustrine and aeolian rocks, and the Middle-Late Triassic Skagerrak Formation, consisting of sandstone and mudstone rocks deposited as part of a series of distributive fluvial systems. This study focuses on a portion of the Norwegian North Sea and integrated seismic, well and core data. It revealed the presence of two stable main sediment input points in the area throughout the Triassic time and demonstrated that sedimentation in this time occurred without interference from the local topography. This implies that the Triassic movements of the late Permian Zechstein salt did not affect the topography, thus channels were free to migrate. This part of the study represents a groundbreaking result as it extends the area of subsurface exploration above the salt structures since the sandstones of the channel deposits display the best reservoir properties.

Following the first UK carbon storage license round in September 2022, SLB initiated a fast-track reprocessing project to support license awardees and boost carbon storage investment in the Solepit basin, Southern North Sea. This project aimed to enhance data quality using modern processing techniques, creating a merged volume that reduces uncertainty in storage site screening caused by legacy data. The Solepit area, covered by 26 vintage surveys, had limitations in the acquired data, making regional subsurface evaluation challenging. This reprocessing project produced an integrated regional image and velocity model over the entire area, focusing on two main carbon storage intervals: the shallow Triassic Bunter sandstone and the deeper Permian Leman sandstone. This case study addresses challenges of data pre-conditioning, using techniques like survey matching, adaptive deghosting, and demultiple. Legacy velocity models were merged and pre-conditioned for tomography inversion, resulting in a consistent regional model. The improved imaging techniques enhanced shallow resolution, aiding overburden evaluation, and provided clearer images of geological features, reducing uncertainty in the interpretation of the Bunter sandstone reservoir and the deeper Permian Leman sandstone for carbon storage site assessments.

Spatio-temporal evolution and paleogeographic reconstructions along rifted margins result from the integration of structural architecture based on magnetics, gravity and log offset 2D seismic, in addition to source-to-sink models based on 3D seismic, well logs, cores, and provenance studies. However, sedimentary records of early rift phases are commonly incomplete due to uplift and erosion, poor preservation due to subsequent deformation and burial, or simply data availability. This research project investigates rift initiation along the Norwegian Continental Margin in two successive time intervals including the Permo-Triassic and Upper Triassic-Lower Jurassic. Detailed tectono-stratigraphic evolution of the Permo-Triassic rifting, including the re-activation of deep inherited structures and the deposition of the Triassic salt has played an important role in controlling the basin morphology and associated depositional systems during the Upper Triassic-Lower Jurassic. Regional, high-resolution seismic tectono-stratigraphy and seismic geomorphology studies are instrumental in developing data-driven models within a regional context. They bring new insights into paleogeographic reconstruction during rift initiation. This holistic approach not only fills the gaps left by incomplete sedimentary records but also offers a predictive framework for future exploration and development.

The multiphase rifting of the mid-Norwegian continental margin resulted in a complex architecture of the post-Caledonian basins. The earliest rifting period took place in the Permo-Triassic and led to the breakup of the Greenland-Norway conjugate margins. In response to the rifting, a series of mixed siliciclastic-evaporite-carbonate basins developed within the proximal and necking domains of the mid-Norwegian continental margin. This study focuses on the spatio-temporal development of the mid-Norwegian continental margin, structural events, and related depositional patterns. Investigations of the tectonostratigraphic framework of these understudied basins provide knowledge on the evolution of depositional depocenters, rifting character, and growth of intrabasinal highs. While the Jurassic evolution and rifting have been thoroughly investigated for hydrocarbon exploration, the early rifting phases have been poorly documented due to limited data of relative poor quality. Recent advances in seismic acquisition and imaging have greatly enhanced seamless structural and stratigraphic mapping providing a consistent regional framework to support multidisciplinary studies from the regional scale down to the finer details. This project synthesizes previous studies, integrates them, and compares with modern, high-resolution seismic data, new exploration wells, and drill cores.

This study presents a comparison of integrated palynostratigraphy from two significant Triassic successions: the Bunter Sandstone storage complex in the Southern North Sea and the Sassendalen and Kapp Toscana groups on the Barents Shelf. Each study region serves distinct purposes—CO2 storage in the Southern North Sea and hydrocarbon exploration on the Barents Shelf—yet both require refined stratigraphic frameworks for effective resource development. For the Southern North Sea, analysis of 500 samples from 14 wells led to the establishment of a new palynozonation, addressing a critical gap in regional biostratigraphy and improving cross-border correlation between the UK and Dutch sectors. On the Barents Shelf, palynological and macrofossil data were integrated with sequence stratigraphy across 42 localities, refining chronostratigraphy and knowledge of the spatio-temporal distribution of reservoir sands. Our findings highlight how climate and environmental shifts influenced Triassic vegetation and sedimentation, with species turnover paralleling major marine transgressions and/or global climatic changes. The frameworks developed offer broader relevance, with potential applications to other Triassic successions, including those in the East Irish Sea Basin and Central and Northern North Sea.

Unlocking the enormous geothermal potential in the South Permian Basin is not without challenges.

Urban data acquisition, drilling and development of production facilities is required in cities where district heating infrastructure is already established and where there is a need for new heat production away from conventional fossil fuel production. A pre-requisite for a geothermal project to be developed is that the subsurface in the urban setting contains a hydrothermal reservoir. One of the main challenges, however, in understanding the risk and uncertainties related to these hydrothermal reservoirs as the subsurface evaluations are usually based on historic subsurface data (acquired for O&G exploration). These legacy data is usually scarce and of poor quality and usually absent in urban settings making the subsurface evaluations prone to high range of uncertainties.

The Northern North Sea is a complex, underexplored region with significant potential for hydrocarbon exploration. The Mesozoic rift basin has proven rich in hydrocarbons for the Jurassic and younger stratigraphic succession. Nevertheless, a comprehensive understanding of the Triassic stratigraphy and its potential for reservoir quality and CO2 storage is still lacking in the literature. The study area is at the limits between the Central North Sea and the Northern North Sea, and the Utsira High has played a key role in shaping the region’s stratigraphic evolution. This study aims to improve our understanding of the Triassic sedimentological evolution and palaeogeography of the Utsira High area throughout the Triassic rifting. By integrating seismic data, wireline logs, and core data, this work identified and mapped intra-Triassic packages and their lateral variations. The analysis presented here has been performed by integrating stratigraphic and biostratigraphic analysis, creating the basis for further and necessary understanding of the region. The results provide new insights into the long-standing nature of the Utsira High and its influence on sediment distribution. This study contributes to a better understanding of the North Sea Rift System’s evolution and has implications for reservoir development and CO2 storage

Accurate subsurface characterization requires detailed, continuous data to understand reservoir heterogeneity. Advanced digital core analysis techniques, such as CoreDNA™, enable high-resolution, non-destructive core logging, while modern laboratory technologies like QEMSCAN (Quantitative Evaluation of Minerals by Scanning Electron Microscopy) provide precise mineralogical insights. This study presents a case from Well 15/12-20 S in the Norwegian Central North Sea, demonstrating how CoreDNA™ data supports subsample selection and upscaling to produce continuous property distributions along the core, effectively bridging the gap between field-scale observations and laboratory-scale measurements in Middle Jurassic Sleipner and Triassic Skagerrak Formations.

The Jurassic Pentland Formation in the Central North Sea is is regionally placed in a humid upper delta to alluvial plain setting and is known for its heterolithic facies. There have been a limited number of economically successful hydrocarbon field developments and there have been some sizeable discoveries, e.g. the Kessog field, that have not been developed. At the HPHT Culzean field the Pentland Formation has relatively favourable petrophysical properties compared to nearby fields. It been on production for 4 years with and delivered gas at high initial production rates and demonstrated economically significant connected volumes. Further development of the Pentland has been derisked through pulsed neutron log acquisition and executed adding perforation to existing Triassic production wells. Again excellent production rates and connected volumes have been proven following perforation. The production performance of the Pentland Formation at Culzean is a case study demonstrating the economic viability of the middle Jurassic play in the Central North Sea. Follow up potential to further increase recovery from the Pentland Formation exists at Culzean as well as there being exploration targets in the middle Jurassic in the acreage surrounding Culzean