Norwegian Geotechnical Institute (NGI) Digital Archive
Not a member yet
1356 research outputs found
Sort by
Comparison of three quantification methods used to detect biochar carbon migration in a tropical soil: A 4.5-year field experiment in Zambia
Full text linkpublishedVersio
Potential for 50% Mechanical Strength Decline in Sandstone Reservoirs Due to Salt Precipitation and CO2–Brine Interactions During Carbon Sequestration
Full text linkPredictive modeling of CO2 storage sites requires a detailed understanding of physico-chemical processes and scale-up challenges. Dramatic injectivity decline may occur due to salt precipitation pore clogging in high-salinity aquifers during subsurface CO2 injection. This study aims to elucidate the impact of CO2-induced salt crystallization in the porous medium on the geomechanical properties of reservoir sandstones. As the impact of salt precipitation cannot be isolated from the precursor interactions with CO2 and acidified brine, we present a comprehensive review and discuss CO2 chemo-mechanical interactions with sandstones. Laboratory geochemical CO2–brine–rock interactions at elevated pressures and temperatures were conducted on two sandstone sets with contrasting petrophysical qualities. Interaction paths comprised treatment with (a) CO2-acidified brine and (b) supercritical injection until brine dry-out, salt crystallization, and growth. Afterward, the core samples were tested in a triaxial apparatus at varying stresses and temperatures. The elastic moduli of intact, CO2-acidified brine treated, and salt-affected sandstones were juxtaposed to elucidate the geochemical–geomechanical-coupled impacts and identify the extent of crystallization damages. The salt-affected sandstones showed a maximum of 50% reduction in Young’s and shear moduli and twice an increase in Poisson’s ratio compared to intact condition. The deterioration was notably higher for the tighter reservoir sandstones, with higher initial stiffness and lower porosity–permeability. We propose two pore- and grain-scale mechanisms to explain how salt crystallization contributes to stress localization and mechanical damage. The results highlight the potential integrity risk imposed by salt crystallization in (hyper)saline aquifers besides injectivity, signaling mechanical failure exacerbated by pressure buildup.Potential for 50% Mechanical Strength Decline in Sandstone Reservoirs Due to Salt Precipitation and CO2–Brine Interactions During Carbon SequestrationpublishedVersio
State-of-the-art: parametrization of hydrological and mechanical reinforcement effects of vegetation in slope stability models for shallow landslides
Full text linkpublishedVersio
Evaluating undrained shear strength and sensitivity in soft sensitive clay using piezocone and field vane tests
Full text linkpublishedVersio
Undrained triaxial test stress path shape as an indicator of sample quality
Full text linkpublishedVersio
Characterization of intermediate soils by innovative in-situ testing procedures using Medusa DMT
Full text linkpublishedVersio
Final Report December 2024
Full text linkThe geomechanical response to CO2 injection is one of the key uncertainties in assessing containment risk for proposed storage sites. The SHARP project introduces a geomechanical readiness level (GRL) to help evaluate the need for geomechanical data collection and modelling within a project. Key developments for the project include to: develop basin-scale geomechanical models that incorporate tectonic and deglaciation effects, and use newly developed constitutive models of rock/sediment deformation (WP1); improve knowledge of the present-day stress field in the North Sea from integrated earthquake catalogues and a comprehensive database of earthquake focal mechanisms (WP2); quantify rock strain and identify failure attributes suitable for monitoring and risk assessment using experimental data (WP3); develop more intelligent methods for in situ monitoring of rock strain and failure, and fluid pressure and movement (WP4); quantify containment risk using geomechanical models and observations from the field and laboratory (WP5); communicate technology development on containment risk to industry and regulators (WP6).
SHARP project results include regional and site-specific data, models from case studies, updated workflows and methodologies and recommendations:
• Updated North Sea bulletin with the most homogeneous representation of North Sea seismicity available to date.
• Updated borehole stress database with new supplements to the World Stress Map 2016 database and improving in-situ stress characterization from seismic analysis.
• Evaluation of regional stress drivers including ridge push, burial and exhumation, glaciation and stress decoupling due to weak layers using comprehensive analysis of regional stress data and novel correlation methods based on mineralogy.
• New site-specific rock mechanical data on samples from Northern Lights Eos well, Aramis site, Lisa Structure, Bunter sandstone analogue and field case in India.
• Stress estimates for CO2 storage using seismic anisotropy and shear wave splitting
• Method development and demonstration for uncertainty quantification, failure probability, probabilistic seismic hazard assessment and quantitative risk assessment applying new data
• Demonstration of pre-cursors for failure in velocity data at laboratory scale
• Outlining and discussing the potential for fibre optic monitoring for detection of seismicity and subsurface pressure changes and deformation.
• Stable seismic event analysis, localisation, estimates of stress orientations and discrimination of natural and induced seismicity requires better offshore seismic resolution with near-source observations
Selected case studies in the North Sea and India have been matured during the project period: the Northern Lights CO2 storage project in the Horda Platform area (N); emerging storage prospects in the Greater Bunter Sandstone area, which encompass the Endurance site (UK); the Lisa structure (DK). The North Sea projects have benefited from transferring knowledge from pioneering and more mature work in the Horda Platform area. Furthermore, new geomechanical data has been collected and evaluated for well-characterised offshore depleted oil and gas fields, like Aramis (NL) and Nini (DK), accelerating their transformation into viable and safe CO2 storage sites. All the sites in the North Sea have benefited from the regional studies and matured their geomechanical readiness level (GRL) during the SHARP project period, whereas India has started initial screening for identification and characterization of potential storage sites.European CommissionpublishedVersio
Deliverable 4.4 Optimizing Fibre-Optic Monitoring: A case study in the Norwegian North Sea
Full text linkThis report provides an overview of monitoring technologies for CO2 storage being considered in the ACT SHARP Project. SHARP 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 to a level acceptable to both commercial and regulatory interests”.
Within the SHARP project, Work Package 4 (WP4) has the overall goal of developing more intelligent methods for monitoring rock strain and fluid pressure. To focus on this effort, we set up a more specific objective to ‘Design improved monitoring schemes using right-time and right-place detection.’ The initial tasks in WP4 were to understand the rock failure risks for each case study site (Deliverables 4.1 and 4.2). These studies form the basis for the monitoring parts of WP4.
Depending on the storage site at hand, CO2 storage monitoring might involve various techniques and methods such as seismic data acquisition, utilizing pressure and temperature sensors, gravity and magnetic surveys, electro-magnetic surveys, and/or well logging tools. This report provides an overview of novel fibre optic (FO) monitoring technologies and focus on how FO monitoring systems might be optimized combined with conventional technologies. We use examples from the Norwegian North Sea case study area to show how a ‘right-time and right-place detection’ system could work, utilizing both conventional data but especially new emerging FO sensing technologies.
The primary focus of this report is on monitoring for containment risk management. Conventional approaches to CO2 storage site monitoring often focus on monitoring the migration of the CO2 plume (i.e. saturation monitoring) which is an essential part of both containment and conformance monitoring. Here we shift the focus to how the rock system responds to CO2 injection, specifically monitoring of pressure, strain and temperature. As CO2 injection proceeds, changes in fluid pressure will result in various geomechanical effects, including elastic deformation and potentially permanent deformation (e.g. in-elastic strains and fractures). If several storage sites are located in the vicinity of each other, they might impact each other’s stress field due to changes in fluid pressure. There is a need for monitoring and handling this potential interaction. Initial assessments of stress and pore pressure effects can be done by rock mechanical testing (see SHARP WP3), but we also need to monitor how the rock system responds to pressure changes. This can be achieved using a combination of microseismic monitoring and downhole measurements of pressure, strain and temperature. It is important to emphasize that while monitoring of fluid displacement is usually a primary objective, in this report we mainly focus on monitoring the effects of geomechanical changes.
Containment risk management encompasses leakage risk management, but it is broader than that, with seismicity monitoring playing a crucial role. Seismic monitoring is also essential for public perception. In the case of significant seismic activity (e.g., events with magnitudes above 2), it is vital to distinguish between CO2 injection-induced events and natural seismicity. Operators must localize such seismic events and determine, for example, if they occur within the reservoir or beneath it. Therefore, reducing depth uncertainty is a crucial risk mitigation step for maintaining public trust and regulatory approval.
The report demonstrates the benefits of integrating existing offshore installations, such as Permanent Reservoir Monitoring (PRM) systems and telecom and power cables, into the monitoring technology to reduce the depth uncertainty in seismic event localization.
A Norwegian North Sea case study illustrates how earthquake detection and seismic monitoring capabilities of the Norwegian National Seismic Network (NNSN) improve with the integration of additional monitoring technologies. Selected stations from two PRM systems streaming data to the NNSN in near real-time significantly enhance earthquake location accuracy. Incorporating the HolsNøy Array (HNAR) and the concept of array processing into this integrated system can reduce seismic location uncertainties by about 50%. Furthermore, the integration of Distributed Acoustic Sensing (DAS) technology utilizing surface optical fibers in submarine telecom infrastructure further reduces depth uncertainty to about 2 km, compared to approximately 10 km uncertainty using the NNSN alone.
In general, the utilisation of FO sensing as a CO2 storage monitoring solution is emerging fast and can include fibres both at surface and downhole. FO sensing can be used in several ways: (a) changes in temperature can be measured using distributed temperature sensing (DTS), (b) direct changes in rock strain can be recorded downhole using distributed strain sensing (DSS) and distributed acoustic sensing (DAS); (c) passive detection of microseismic events can be done using FO DAS cables, as well as (d) active seismic monitoring and seismic imaging.
We aim to illustrate with examples from published research and field trials from various regions worldwide, how combining these various monitoring technologies can create an enhanced monitoring scheme that provides a holistic understanding of subsurface dynamics in the Norwegian North Sea region.
Focusing on the feasibility of DAS and its detectability, it was demonstrated in a field trial in Canada that microseismic events with magnitudes lower than -0.6 are detectable at distances exceeding 10 km when the DAS fiber was deployed in an injection well cemented behind casing. Experience from the geothermal sector show that utilizing low-frequency DAS downhole allows for the direct observation of microseismic events linked to fracture openings, with observed strain changes of about 0.5 nanoStrain. Current DAS technologies measure strain changes with picoStrain resolution, enabling the detection of these fracture openings and other signals related to CO2 injection when deployed in a well. The overall strains which occur in response to CO2 injection are about 2 milliStrain in formations and typically in microStrain range when the fiber is deployed in or cemented between formation and casing.
Additionally, DAS in surface fibers can measure seismic anisotropy and by this infer stress field changes. This capability was demonstrated by measuring icequake-induced seismic events in Antarctica. It is shown that DAS surface fibre can image the arrival of both fast and slow shear waves, and thus the delay time can be measured with high temporal and spatial accuracy (e.g., with a slowness resolution of about 0.1 s/km)
Permanent Reservoir Monitoring (PRM) systems provide high-resolution measurements capable of detecting subtle changes, such as variations of approximately 200 microseconds time shift, indicative of pressure, strain, and temperature alterations. Additionally, stress field estimates utilizing shear wave anisotropy provide crucial inputs for stress field estimations updating geomechanical models, facilitating the development of preventative monitoring strategies.
The primary advantage of FO monitoring lies in its continuous real-time monitoring and high-resolution measurements, facilitating the early detection of subsurface changes. Although real-time monitoring is valuable since it enables prompt decision-making, changes in the stress field may also result in delayed fault reactivation, which is not immediately evident in the real-time data. This means that merely including FO as advanced monitoring solution as such is not sufficient. It is important to monitor the right parameters at the right time and place to record important input parameters for predictive geomechanical modelling.
For instance, various studies demonstrate that human activities, such as fluid injection or withdrawal, can trigger earthquakes. This poses risks in industries like geothermal energy production where it was observed that horizontal stresses were shifting by tens of mega Pascals, potentially leading to prolonged induced seismicity even after operations cease. Emphasized in the report by Williams et al. (2022) are the stress history, seismicity, and rock mechanics parameters, which serve as crucial inputs for geomechanical modelling and predictive analysis. It is imperative to complement real-time monitoring with preventative monitoring to identify potential risks before their manifestation in real-time data.
The data obtained from FO monitoring can be integrated into geomechanical modelling workflows, providing calibration and ground truthing of models as projects develop. This will enable a more comprehensive understanding of the subsurface behaviour. Such predictive geomechanical modelling empowers operators to devise proactive strategies, enables early identification of potential issues and enables the implementation of preventive measures to mitigate adverse events.
Furthermore, as technological advancements in CO2 storage and monitoring continue to evolve, especially the use of FO sensing, there is a growing recognition that existing regulations may need to be updated to incorporate these innovations. Integrating fiber optic technologies into regulatory frameworks can significantly enhance the accuracy and reliability of monitoring efforts.European CommissionpublishedVersio
Deliverable 2.3b: Stress-induced seismic anisotropy: a promising tool to assess reservoir proprieties and caprock integrity
Full text linkThis deliverable assesses the potential of seismic anisotropy to measure stress within the CO2 storage complex, primarily the reservoir and overburden. Using onshore passive seismic and stress data for the UK, we test the potential for shear-wave splitting to be used to monitor the stress field in and above CO2 storage sites. We focus on four regions: Northeast England, Northwest England, Southeast England and South Wales. Stress-induced anisotropy is observed in all regions and is particularly clear in Northwest England and Southeast England.
We also show, for the first time, that shear-wave splitting can be measured using seismicity recorded by offshore Permanent Reservoir Monitoring Systems (PRMs). Shear-wave splitting is measured at select PRM stations at the Snorre field using data recorded from the 21st March 2022 MW 5.1 Tampen Spur earthquakes and subsequent microseismic aftershocks (0.1 < $ML < 2.6). These results show that offshore sensors, such as PRM systems, are suitable for measuring shear-wave splitting for microseismic data even in relatively sparse deployments if the sensors are deployed above CO2 storage projects. This makes shear-wave splitting an important potential added value that should be considered when planning offshore passive seismic monitoring of CO2 storage projects.European CommissionpublishedVersio