Norwegian Geotechnical Institute (NGI) Digital Archive
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Geophysical early warning of salt precipitation during geological carbon sequestration
Get PDFSequestration of industrial carbon dioxide ( CO 2) in deep geological saline aquifers is needed to mitigate global greenhouse gas emissions; monitoring the mechanical integrity of reservoir formations is essential for effective and safe operations. Clogging of fluid transport pathways in rocks from CO 2-induced salt precipitation reduces injectivity and potentially compromises the reservoir storage integrity through pore fluid pressure build-up. Here, we show that early warning of salt precipitation can be achieved through geophysical remote sensing. From elastic P- and S-wave velocity and electrical resistivity monitoring during controlled laboratory CO 2 injection experiments into brine-saturated quartz-sandstone of high porosity (29%) and permeability (1660 mD), and X-ray CT imaging of pore-scale salt precipitation, we were able to observe, for the first time, how CO 2-induced salt precipitation leads to detectable geophysical signatures. We inferred salt-induced rock changes from (i) strain changes, (ii) a permanent ~ 1.5% decrease in wave velocities, linking the geophysical signatures to salt volume fraction through geophysical models, and (iii) increases of porosity (by ~ 6%) and permeability (~ 7%). Despite over 10% salt saturation, no clogging effects were observed, which suggests salt precipitation could extend to large sub-surface regions without loss of CO 2 injectivity into high porosity and permeability saline sandstone aquifers.publishedVersio
Microplastic accumulation by tube-dwelling, suspension feeding polychaetes from the sediment surface: A case study from the Norwegian Continental Shelf
Get PDFSediment samples (0–1 cm) and tube-dwelling polychaetes from the Norwegian Continental Shelf and the Barents Sea were collected, including areas close to oil and gas installations and remote locations. Microplastics (≥45 μm) were found in quantifiable levels in 27 of 35 sediment samples, from 0.039 to 3.4 particles/gdw (dw = dry weight); and 9 of 10 pooled polychaete samples, from 11 to 880 particles/gww (ww = wet weight). Concentrations were significantly higher in tube-dwelling polychaetes than sediments from the same locations (p < 0.0097) by orders of magnitude. We introduce a Biota-Sediment Particle Enrichment Factor (BSPEF) to quantify this factor increase in polychaetes, which ranged from 100 to 11000 gdw/gww (280–31000 gdw/gdw). Higher microplastic levels were observed in polychaete tube than in soft tissue (n = 4). The feeding behavior and life cycle of tube-dwelling polychaetes could have an important influence on the transport, distribution and food-chain dynamics of microplastics on the seafloor.publishedVersio
Centrifuge study of p-y curves for vertical-horizontal static loading of piles in sand
Get PDFPile foundations for offshore structures are subjected to vertical-horizontal load combinations. The current design method separately analyzes horizontal and vertical responses of piles without considerations of the combined effect of the loads on soil-pile interaction. However, there is experimental and numerical evidence that lateral behavior of a pile-soil system can be affected by both axial compression and tension load on the pile. In this study, two single-pile and two tripod-pile centrifuge model tests under different loading conditions were analyzed to investigate the influence of combined loads on the lateral response of soil-pile system. The displacement and the bending moment were measured and analyzed to highlight the behavior of pile-soil system under different loading conditions. The p-y curves for the different tests were calculated and compared to reveal the influence of axial load component on the lateral behavior of soil-pile systems. It is concluded that compared with pure lateral loading, the p-y curves of piles under compression are steeper because of soil densification effect, while the opposite is observed under tension load that is the p-y curves are gentler.acceptedVersio
Field and laboratory test results Halden
Get PDFHalden silt site is property of Halden municipality and it is known locally as Rødsparken.
As part of the characterization of Halden silt site during NGTS project, two main reports
are prepared: 1) a factual report (20160154-04-R) and 2) an interpretation report
(20160154-05-R) (see figure in the next page). The present report (20160154-04-R)
presents a factual summary of all laboratory and in situ testing carried out for the NGTS
project between May 2015 and March 2019.
Site specific tests and methods are described in the present report. Standard methods for
laboratory and in situ tests that apply for all NGTS sites are detailed in the general reports
NGTS Report 02 (20160154-02-R) and NGTS Report 03 (20160154-03-R),
respectively.publishedVersio
Digital Drill Core Models: Structure-from-Motion as a Tool for the Characterisation, Orientation, and Digital Archiving of Drill Core Samples
Get PDFStructure-from-motion (SfM) photogrammetry enables the cost-effective digital characterisation of seismic- to sub-decimetre-scale geoscientific samples. The technique is commonly used for the characterisation of outcrops, fracture mapping, and increasingly so for the quantification of deformation during geotechnical stress tests. We here apply SfM photogrammetry using off-the-shelf components and software, to generate 25 digital drill core models of drill cores. The selected samples originate from the Longyearbyen CO2 Lab project’s borehole DH4, covering the lowermost cap rock and uppermost reservoir sequences proposed for CO2 sequestration onshore Svalbard. We have come up with a procedure that enables the determination of bulk volumes and densities with precisions and accuracies similar to those of such conventional methods as the immersion in fluid method. We use 3D printed replicas to qualitatively assure the volumes, and show that, with a mean deviation (based on eight samples) of 0.059% compared to proven geotechnical methods, the photogrammetric output is found to be equivalent. We furthermore splice together broken and fragmented core pieces to reconstruct larger core intervals. We unwrap these to generate and characterise 2D orthographic projections of the core edge using analytical workflows developed for the structure-sedimentological characterisation of virtual outcrop models. Drill core orthoprojections can be treated as directly correlatable to optical borehole-wall imagery data, enabling a direct and cost-effective elucidation of in situ drill core orientation and depth, as long as any form of borehole imagery is available. Digital drill core models are thus complementary to existing physical and photographic sample archives, and we foresee that the presented workflow can be adopted for the digitisation and digital storage of other types of geological samples, including degradable and dangerous ice and sediment cores and samples.publishedVersio
Granular viscosity from plastic yield surfaces: The role of the deformation type in granular flows
Get PDFNumerical simulations of granular flows with Navier–Stokes type models emerged in the last decade, challenging the well established depth-averaged models. The structure of these equations allows for extension to general rheologies based on complex and realistic constitutive models. Substantial effort has been put into describing the effect of the shear rate, i.e. the magnitude of the velocity gradient, on the shear stress. Here we analyse the effect of the deformation type. We apply the theories of Mohr–Coulomb and Matsuoka–Nakai to calculate the stresses under different deformation types and compare results to the theory of Drucker–Prager, which is formulated independently of the deformation type. This model is particularly relevant because it is the basis for many granular rheologies, such as the –rheology. All models have been implemented into the open-source toolkit OpenFOAM® for a practical application. We found that, within the context of these models, the deformation type has a large influence on the stress. However, for the geometries considered here, these differences are limited to specific zones which have little influence on the landslide kinematics. Finally we are able to give indicators on when the deformation type should be considered in modelling of landslides and when it can be neglected.publishedVersio
Calibration foundation models for the WAS-XL monopile
Get PDFThis technical note documents the calibration of REDWIN foundation model 2 and distributed p-y springs for the WAS-XL monopile in clay with a length over diameter ratio (L/D) of 5. The calibration files will be used by the OC6 Phase II participants to verify the correct implementation of foundation models
ACT4storage - Acoustic and Chemical Technologies for environmental GCS monitoring. D4 - Recommended guidelines report
Get PDFCarbon capture and storage (CCS) is a promising tool for accelerating decarbonization and reaching international climate goals. The process involves capturing CO2 from energy-intensive industries such as waste-to-energy plants, fertilizer production, and fossil fuel combustion, and injecting it into suitable geological formations for safe and permanent storage instead of releasing it into the atmosphere. A dedicated monitoring plan is required to verify that the CO2 is safely stored over time and to detect and quantify leakage if it should occur. For offshore carbon storage, the primary monitoring is based on seismic methods and in-well monitoring, complemented by marine monitoring targeting the seabed and the water column above the storage reservoir. This report is intended to provide support for parties involved in the design of a marine monitoring program for offshore CCS sites. ...publishedVersio
Fracture attribute scaling and connectivity in the Devonian Orcadian Basin with implications for geologically equivalent sub-surface fractured reservoirs
Get PDFFracture attribute scaling and connectivity datasets from analogue systems are widely used to inform sub-surface fractured reservoir models in a range of geological settings. However, significant uncertainties are associated with the determination of reliable scaling parameters in surface outcrops. This has limited our ability to upscale key parameters that control fluid flow at reservoir to basin scales. In this study, we present nine 1D-transect (scanline) fault and fracture attribute datasets from Middle Devonian sandstones in Caithness (Scotland) that are used as an onshore analogue for nearby sub-surface reservoirs such as the Clair field, west of Shetland. By taking account of truncation and censoring effects in individual datasets, our multiscale analysis shows a preference for power-law scaling of fracture length over 8 orders of magnitude (104 to 104 m) and kinematic aperture over 4 orders of magnitude (106 to 102 m). Our assessment of the spatial organization (clustering and topology) provides a new basis for up-scaling fracture attributes collected in outcrop- to regional-scale analogues. We show how these relationships may inform knowledge of geologically equivalent sub-surface fractured reservoirs.publishedVersio
Assessment of building damage due to excavation-induced displacements: The GIBV method
Get PDFThis paper presents an original methodology for the rapid assessment of “potential” building damage caused by an excavation. The combination of the Ground-work Impact (GI), in terms of induced greenfield displacements, and the Building Vulnerability (BV) form the basis for the GIBV damage assessment method. Both short- and long-term displacements are considered in the impact evaluation. In addition to short-term displacement due to undrained shear deformations, groundwater drawdown can result in significant consolidation settlements at considerable distance from the excavation site. In the proposed method for soft soil ground conditions, the short-term excavation-induced settlement is derived using empirical expressions and long-term displacement is estimated by coupling empirically-derived relationships for excavation-induced groundwater drawdown with a soil stratification model and consolidation theory. The building vulnerability is assessed by considering different physical characteristics and conditions of the buildings. The GIBV method has been implemented in a GIS tool to predict damage classes for buildings exposed to excavation-induced settlements. Two different case studies in Norway were used to test the reliability of the predictions of the tool and validate the methodology. A comparison between the predicted damage classes with the back-calculated ones shows a relatively high accuracy of the methodology. Moreover, the coupled model, which considers both impact and vulnerability for the damage assessment of buildings, has a higher accuracy and lower overestimation rate compared to the results obtained by just considering the impact.publishedVersio