added 3 research items
Longyearbyen CO2 Lab
The Wilhelmøya Subgroup (Norian-Bathonian) is considered as the prime storage unit for locally produced CO 2 in Longyearbyen on the Arctic archipelago of Svalbard. We here present new drillcore and outcrop data and refined sedimentological and sequence-stratigraphic interpretations from western central Spitsbergen in and around the main potential CO 2-storage area. The Wilhelmøya Subgroup encompasses a relatively thin (15-24 m) siliciclastic succession of mudstones, sandstones and conglomerates and represents an unconventional potential reservoir unit due to its relatively poor reservoir properties, i.e., low-moderate porosity and low permeability. Thirteen sedimentary facies were identified in the succession and subsequently grouped into five facies associations, reflecting deposition in various marginal marine to partly sediment-starved, shallow shelf environments. Palynological analysis was performed to determine the age and aid in the correlation between outcrop and subsurface sections. The palynological data allow identification of three unconformity-bounded sequences (sequence 1-3). These sequences record intermittent deposition in the Early Norian, Early-Middle Toarcian, and Late Toarcian-Aalenian, interrupted by extended periods of erosion, bypass and/or non-deposition. The stratigraphically condensed development of the Wilhelmøya Subgroup in western central Spitsbergen is interpreted to be the result of very low subsidence rates coupled with a physiographic setting characterised by a very gentle depositional gradient. This facilitated rapid shoreline shifts in response to even relatively modest variations in relative sea level with considerable influence on the resulting depositional patterns. We present a revised depositional model for the regionally distinct Brentskardhaugen Bed at the top of the Wilhelmøya Subgroup involving condensation and partial reworking of a series of Upper Toarcian-Aalenian, high-frequency sequences. Coarse-grained extraformational fractions observed within conglomerates of the Wilhelmøya Subgroup are suggested to have been supplied from uplifted and exposed margins to the west (northern Greenland) and north (northern Svalbard).
On Svalbard (Arctic Norway), a pilot-scale research project has been established to investigate the feasibility of storing locally produced CO 2 in geological aquifers onshore. Drilling, geophysical and geological data acquisition and water-injection tests confirm the injectivity and storage capacity of the naturally fractured and compartmentalised siliciclastic storage unit that is located at c. 670-1000 m depth below the proposed injection site in Adventdalen, Central Spitsbergen. Excellent outcrops of the reservoir-caprock units 15 km from the planned injection site allow for detailed sedimentological and structural studies, and complement 2D seismic data acquired onshore and offshore. In this contribution, we focus on small-scale (metre-scale displacement) normal faults present in both reservoir and caprock to quantify their seismic detectability. We generate synthetic seismic sections of structural models based on high-resolution virtual outcrop models populated with elastic parameters from wireline log data. We address a number of geological scenarios, focusing on CO 2 migration within the compartmentalised reservoir, its baffling by normal fault zones and migration of CO 2 along a hypothetical fault in the caprock. Our results indicate that while the small-scale faults are unlikely to be imaged on conventional 2D seismic data, the fluid effect associated with CO 2 migration along the fault zone will generate considerable reflectivity contrasts and should result in good definition of the extent of the CO 2 plume even in such structurally confined settings.
The Upper Triassic to Middle Jurassic Wilhelmøya Subgroup forms one of the more suitable reservoir units on the Norwegian Arctic archipelago of Svalbard. The target siliciclastic storage unit, which is encountered at approx. 670 m depth at the potential injection site in Adventdalen, central Spitsbergen, is a severely under-pressured (at least 35 bar), tight and compartmentalised reservoir with significant contribution of natural fractures to permeability. In this contribution, we characterise the 15-24 m-thick Wilhelmøya Subgroup storage unit using both borehole and outcrop data and present water-injection test results that indicate the presence of fluid-flow barriers and the generation of new, and propagation of pre-existing natural fractures during injection. Whole core samples from drillcores and outcrops were sampled for pore network characterisation and analysed using high-resolution X-ray computed tomography (Micro-CT). We demonstrate that heterogeneities such as structural discontinuities, igneous bodies and lateral facies variations, as examined in well core and equivalent outcrops, will strongly influence fluid flow in the target reservoir, both by steering and baffling fluid migration. Many of these heterogeneities are considered to be subseismic, and their detailed characterisation is important to predict subsurface CO 2 storage potential and optimise injection strategy.
As part of the Longyearbyen CO2 laboratory, carbon dioxide may be captured from the local coal burning plant and injected into a siliciclastic Upper Triassic-Lower Jurassic reservoir located 700 to 1000m below the surface. The targeted reservoir is unconventional and affected by compaction and cementation caused by deep burial. However, fluid flow is facilitated by extensive fracturing. Extensive water injection tests show there are flow barriers in the reservoir which this study credits to the presence of impermeable faults too small to be imaged by seismics. We have further investigated the identified faults outcropping in river sections at Deltaneset, 15km northeast of Longyearbyen. These extensional deformation features have been related to the latest phase of the Tertiary Fold and Thrust Belt affecting Svalbard where the elevated fold complex began to collapse or alternatively relate to the onset of the Norwegian-Greenland Ocean opening. The faults exposed at Deltaneset exhibit varied deformation styles within an envelope adjacent to the fault core which varies depending on the lithological properties of the host rock. Baffling capacity of faults is determined to be significant owing to consistent clay gouge within fault cores. Gouge-displacement ratios are notably high facilitated by the argillicoeus nature of the pro-delta deposits characteristic of the Late Triassic to early Jurassic. Shale smearing is also present on faults with small (less than 1 meter) displacement. Extensional structures have a limited upward propagation and usually dissipate within the early most Jurassic strata, this is likely due to the presence of a regional sub-horizontal decollement structure in the upper Agardhfjellet Fm. Kinematic indicators preserved within fault zones reveal a strong component of oblique slip on faults while many minor slip surfaces are dominated by lateral displacement. Sub-vertical fracture concentration, especially in coarser units is significantly increased immediately adjacent to faults whereas finer grained units display a zone of brecciation.
Both thermogenic and biogenic gas were encountered during scientific drilling on Svalbard, Arctic Norway. The thermogenic gas has been encountered in an interval at 650-703 m depth, spanning both the lower part of the caprock, an organic-rich shale unit with subordinate siltstone intervals, and the upper part of the siliciclastic reservoir targeted for CO2 storage. Both water injection tests and gas flow tests were conducted to establish the formation injectivity and production capability of this interval. In this contribution, we investigate the organic rich shale interval in detail, integrating well data with direct observations on outcrop analogues, to present a conceptual model of the reservoir-cap rock interface.
In this study we characterize the natural fracture network in the two lowermost members (i.e. Oppdalen and Lardyfjellet Mbs.) of the Agardhfjellet Formation in order to quantify its architecture and predict the fluid flow pathways. We conducted manual fracture mapping on 90 m of continuous drill core to quantify the vertical distribution of predominantly sub- horizontal and low angle fractures. Field data (i.e. scanlines) were used to quantify horizontal distribution and orientation of the sub-vertical fractures. Wireline logs, including an acoustic televiewer, supplemented those data. In addition, ground and drone-based photogrammetry was applied to generate 3D models of laterally and vertically extensive outcrops for both stratigraphic and structural correlations. About 1500 fractures from cores and 1000 fractures from the field were obtained and pro-cessed.