Norwegian Geotechnical Institute (NGI) Digital Archive
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A study of the effects of early diagenesis on the geotechnical properties of carbonate sediments (North West Shelf, Australia)
Get PDFCarbonate sediments are often regarded as problematic in geotechnical engineering due to the high variability of their properties. Understanding and quantifying this variability will become increasingly critical in the years ahead, notably with respect to upcoming developments in offshore renewable energy, for which limited in-situ data are typically available to characterise large areas. Here, six intervals from the North West Shelf of Australia, each composed of similar carbonate grains but accumulated in different environments, are investigated to better understand how the post-depositional cementation, alteration and dissolution of sediments, known as diagenesis, impact their geotechnical properties. Intervals are primarily affected by mineralogy-driven meteoric diagenesis, comprising in-situ dissolution of metastable grains and subsequent precipitation of cement that occurred when the shelf was exposed during lower sea-levels, and by marine diagenesis. In both cases, increased diagenesis results in a higher cement-to-solid ratio and compressive strength. However, while marine diagenesis is associated with a reduction in void ratio, this is not initially observed with mineralogy-driven meteoric diagenesis. Additionally, for a similar cement-to-solid ratio, microcrystalline cement results in higher compressive strength than sparite cement. The data further reveal that the level of meteoric cementation and the compressive strength increase as a function of the duration of exposure and of the regional climate, along with a reduction of the specific gravity related to the replacement of aragonite by calcite. However, increased meteoric diagenesis also leads to the formation of macro-scale heterogeneities such as calcrete layers and karsts that can affect the holistic geotechnical behaviour of such deposits.A study of the effects of early diagenesis on the geotechnical properties of carbonate sediments (North West Shelf, Australia)publishedVersio
Site specific avalanche warning for settlements in Northern Norway: Twenty years of the Northern Norway Avalanche Surveillance Program
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The Luna Analog Facility testbeds (ESA, EAC): contemporary characterization work of highland (lunar) and mare (EAC-1) lunar regolith simulants
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Permanent tunnel support with reinforced shotcrete arches and forepoling in over-consolidated till and weathered rock. A case study based on the construction of the Bergås tunnel, Norway
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Deliverable 3.6 Report on Experimental derived porosity and permeability models
Get PDFThis report details the experimental results of a study on defining porosity and permeability in reservoir and caprocks during complex stress histories, conducted as part of the ACT SHARP Project. The multinational SHARP consortium has the overall objective to improve understanding on:
“Stress history and reservoir pressure for improved quantification of CO2 storage containment risks”
SHARP Storage is a research project funded under the ERA-NET ACT programme for accelerating Carbon Capture and Storage (CCS). The overall aim is to improve the accuracy of subsurface CO2 storage containment risk management through the improvement and integration of subsurface stress models, rock mechanical failure and seismicity observations.
One aim of the SHARP project was to further develop on the initial understanding of changes of porosity and permeability as a result of stress changes, as outlined in this report.European CommissionpublishedVersio
The impact of biochar's physicochemical properties on sorption of perfluorooctanoic acid (PFOA)
Get PDFTo better characterize properties governing the sorption of per- and polyfluoroalkyl substances (PFAS) to biochar, twenty-three diverse biochars were characterized and evaluated as sorbents for perfluorooctanoic acid (PFOA). Biochars were produced at various temperatures, using two different technologies, and made from sewage sludge, food waste reject, wood wastes, and one reference substrate (wood pellets). The biochars were characterized in terms of surface area, pore volume and pore size distributions, elemental composition, leachable elements, ash content, pH, zeta potential, condensed aromatic carbon (ConAC) content (determined by benzenepolycarboxylic acid (BPCA) markers), and their -OH functional group content (infrared spectroscopy). PFOA sorption isotherms were determined using Polanyi-Dubinin-Manes (PDM) and Freundlich models. The sludge-based biochars [Freundlich coefficients (log KF) between 2.56 ± 0.11 and 6.72 ± 0.22 (μg/kg)/(μg/L)nF; fitted free energy of adsorption (E) and pore volume (Vo) from the PDM model between 13.27 and 17.26 kJ/mol, and 0.50 and 523.51 cm3/kg] outperformed wood biochars [log KF between 1.02 and 4.56 ± 0.22 (μg/kg)/(μg/L)nF; E between 9.87 and 17.44 kJ/mol; Vo between 0.21 and 7.16 cm3/kg] as PFOA sorbents. Multivariate statistical analysis revealed that the sorption capacity was mainly controlled by pore volume within the pore diameter region that could accommodate the molecular size of PFOA (3–6 nm). Hydrophobic interactions between PFOA and aromatic carbon rich regions controlled sorption affinity, especially in the wood biochars.publishedVersio
Deliverable 3.5: Report on stress dependent rheology
No full textCO2 geosequestration through injection in porous subsurface reservoirs is a critical step to reduce atmospheric carbon content. However, injection of CO2 can cause stress imbalances in the reservoir, resulting in leakage and irreversible deformation of the reservoir or caprock. In order to prevent these unwanted consequences and ensure permanent disposal of CO2, monitoring subsurface stress conditions play a pivotal role. However, monitoring stress in such a closed system, deep in the subsurface is extremely difficult and operators resort to expensive geophysical survey to infer stress conditions. In this deliverable report as part of the SHARP project, we demonstrate with reservoir coreplugs from the North Sea, in laboratory scale, how acoustic waves are sensitive to stress conditions in the subsurface due to continuous evolution of mechanical property of the rockmass, and in specific cases can even forecast change in deformation mechanism in the reservoir. We specifically explore the change in P and S wave velocity and corresponding amplitude and propose a tentative traffic-light scenario based on changes in wave attributes. We believe this will lay the foundation for successful use of active acoustic monitoring in CCS operations to ensure safe stress condition in a cost-effective way.publishedVersio
Deliverable 5.4: Workflow for reliability assessment
No full textThis report presents a workflow for probabilistic fault stability assessment in CO2 storage, emphasising uncertainty quantification, parameter ranking, and Bayesian updating for critical inputs. Using North Sea's Horda platform cases, including the Vette fault zone in Smeaheia, this study demonstrates the value of the suggested methods. This study highlights the usefulness of the probability of failure (Pf) as a reliable measure for stability assessment, particularly when traditional methods present conflicting results. It also highlights the effectiveness of the Sobol sensitivity analysis for input ranking and understanding parameter interactions, which is crucial for resource prioritisation and monitoring strategy in early field development. Furthermore, the report illustrates how the Bayesian approach can enhance the accuracy of stress prediction by leveraging data from geologically similar sites and acknowledging site-specific heterogeneity, significantly aiding in geomechanical risk assessments.European CommissionpublishedVersio
