Structural instrumentation and monitoring of the Block Island Offshore Wind Farm

publishedVersio

Offshore Wind Turbine Foundations State of the Art

The huge growth and intense development in the European offshore wind power sector over the last decade have created significant achievements within the wind turbine foundation technology. The state of the art focusing on geotechnical design aspects for Offshore Wind Turbine (OWT) foundations and important aspects for installation are presented in this paper. In place operational experience based on structural health monitoring campaigns and future trends are also discussedpublishedVersio

Offshore Wind Turbine Foundations State of the Art

The huge growth and intense development in the European offshore wind power sector over the last decade have created significant achievements within the wind turbine foundation technology. The state of the art focusing on geotechnical design aspects for Offshore Wind Turbine (OWT) foundations and important aspects for installation are presented in this paper. In place operational experience based on structural health monitoring campaigns and future trends are also discusse

Field verification tests of the newly developed flow cone tool—In-situ measurements of hydraulic soil properties

Hydraulic soil properties, and in particular the hydraulic conductivity, is important in a number of geotechnical design cases. However, attention is often drawn towards the method of analysis rather than the quality and validity of the hydraulic properties used as input. Intact samples of sand or silt are difficult or impossible to obtain, and prediction of hydraulic soil properties from available in-situ tools represents a challenge. With the aim of quick and reliable in-situ measurements of hydraulic properties of sands and silts, NGI developed a prototype tool referred to as the flow cone. The tool combines the widely used cone penetration test with an add-on pumping system that allows water to flow into the surrounding sediments during cone penetration and stand-still. By measuring flow rates and pore water pressures, the hydraulic properties of the surrounding soil can be estimated. The flow cone prototype was tested at the NGTS sand site (Øysand, Norway) in September 2018. The aim of this paper is to present the measured and interpreted results. The results are evaluated within the context of available data from the sand site including cone penetration tests, in-situ falling head tests, grain size distributions and constant head tests from laboratory. Recommendations for further work and potential applications in engineering practice are discussed.Field verification tests of the newly developed flow cone tool—In-situ measurements of hydraulic soil propertie

Field verification tests of the newly developed flow cone tool—In-situ measurements of hydraulic soil properties

Hydraulic soil properties, and in particular the hydraulic conductivity, is important in a number of geotechnical design cases. However, attention is often drawn towards the method of analysis rather than the quality and validity of the hydraulic properties used as input. Intact samples of sand or silt are difficult or impossible to obtain, and prediction of hydraulic soil properties from available in-situ tools represents a challenge. With the aim of quick and reliable in-situ measurements of hydraulic properties of sands and silts, NGI developed a prototype tool referred to as the flow cone. The tool combines the widely used cone penetration test with an add-on pumping system that allows water to flow into the surrounding sediments during cone penetration and stand-still. By measuring flow rates and pore water pressures, the hydraulic properties of the surrounding soil can be estimated. The flow cone prototype was tested at the NGTS sand site (Øysand, Norway) in September 2018. The aim of this paper is to present the measured and interpreted results. The results are evaluated within the context of available data from the sand site including cone penetration tests, in-situ falling head tests, grain size distributions and constant head tests from laboratory. Recommendations for further work and potential applications in engineering practice are discussed.Field verification tests of the newly developed flow cone tool—In-situ measurements of hydraulic soil propertie

CCS Leakage Detection Technology - Industry Needs, Government Regulations, and Sensor Performance

Reliable CCS monitoring is vital in order to confirm that injected CO2 stays in the reservoir as intended, and that any occurring leakage is promptly detected allowing corrective actions to be initiated. Motivations for implementing monitoring strategies beyond the legal minimum required by government regulations, can be divided into economic, environmental and reputational factors, where the latter is significant; adequate monitoring is important for attaining public acceptance. CCS monitoring methods can be divided into deep focused (reservoir, overburden) and shallow focused (seabed, water column) methods. Shallow monitoring methods include acoustic and chemical sensors placed in the water column. For the CCS application, these sensor technologies are complementary; acoustic sensors are sensitive to CO2 in gas phase and chemical sensors can detect water-dissolved CO2 or formation fluids. We discuss the motivations for CCS monitoring, and offer a structured overview of acoustic and chemical technologies for CCS monitoring at the seabed and in the water column. Each technology is evaluated in terms of its applicability to CCS monitoring, highlighting its strengths and limitations for detection, quantification and characterization of CCS related leakage. We conclude that while state of the art sensor technology is sufficient to meet government requirements, there is potential for improved integrated monitoring through optimal use and combination of technologies. The concept of integrated monitoring where different sensor types measure different parameters is emerging as a promising monitoring strategy

Monitoring CO2 Storage Sites Onshore and Offshore using InSAR Data and Strain Sensing Fibre Optics Cables

A key requirement for geological CO2 storage is site integrity management and monitoring during operation through to the post decommissioning period. This paper focuses on monitoring deformation of the ground surface and seabed as a proxy for overall deformation in the reservoir and surrounding layers. The objective is to inform, based on deformation data, on how the reservoir is responding to CO2 injection and to ensure any issues with regard to storage integrity are rapidly detected. The magnitude and pattern of deformation at the surface reveals geomechanical/hydromechanical processes that occur in reservoir due to CO2 injection. We acquired deformation data from the In Salah CO2 injection site and from four additional study cases during the course of this study; one in the onshore UK, the other a combined campaign onshore Norway and offshore Germany, and the third in onshore Japan. Significant developments in measurement techniques, processing tools and interpretation algorithms were developed through this project. Models were then developed to simulate the observed data and to couple surface deformation to displacement in the subsurface. The results show millimeter-scale deformations in the subsurface have a signature at the surface that can be captured by the tools and workflows developed in this project. These deformations, particularly the patterns, are important factors to consider when monitoring a CO2 storage site

Assuring Integrity of CO2 Storage Sites Through Ground Surface Monitoring (SENSE)

Monitoring of geological CO2 storage is crucial for large-scale injection to gain public acceptance. Monitoring plans for large-scale operations need to include both the injection and post-injection phases to assure CO2 is safely stored permanently. The SENSE project aims to develop reliable, continuous, and cost-efficient monitoring based on ground movement detection combined with geomechanical modeling and inversion, utilizing new technology developments, data processing optimization, and interpretation algorithms. The proposed research activities include: • demonstration of continuous monitoring of surface deformation and subsurface pressure distribution using satellite data, water pressure sensors and fiber optics; • quantitative characterization of critical geomechanical and hydraulic parameters and automatization routine for data processing and interpretation; • optimization of sampling arrays in order to offer storage site operators a cost-effective monitoring option as part of an effective site assurance program. The SENSE project brings together experts from 14 international institutions of nine different countries to solve challenges in CO2 storage site monitoring and to provide solutions for safe and successful injection and post-closure phases of site operation. The project is organized in five Work Packages (WPs); WP1: Quantification of ground movement, WP2: Geomechanical modeling and rock strain assessment, WP3: History matching inversion and coupled flow-mechanics, WP4: Integration of results for cost-effective monitoring and WP5: Project management. The ultimate goal of SENSE is to offer storage site operators a cost-effective monitoring option that can form part of an effective site assurance/monitoring program and feed into workflows for an early alert system to detect unexpected changes in the subsurface. The SENSE project has four demonstration sites for monitoring technologies and developing concepts and procedures. These sites are both onshore and offshore. The onshore sites include In Salah (Algeria) and Hotfield Moors (UK). For these sites, the project will use satellite data to explore the response of the surface to pressure changes in the subsurface. Algorithms for automatic satellite data processing to facilitate quick access to ground elevation data for site operators are under development at the British Geological Survey (BGS) and Norwegian Geotechnical Institute (NGI). The offshore sites include Bay of Mecklenburg (Germany) and the Gulf of Mexico (USA). In addition, the SENSE partners have requested access to data from the Troll Gas Field, the North Sea, to study its subsidence due to production-related pressure reduction. The Troll Gas Field is located next to the storage site considered for the Norwegian Long Ship project, and its data will provide a good understanding of the geomechanics of the area. In this paper, we present the work on the In Salah and the Bay of Mecklenburg sites. New InSAR data from the In Salah are used to evaluate the ground movement during the post-injection period and thus to assess the behaviour of the storage site after completion of the injection phase. Bay of Mecklenburg is an offshore site for field experiment to inject a gas underground, build-up pressure, uplift the seafloor and measure the resulted uplift. The first field campaign at the Bay of Mecklenburg was completed in late 2019. It provided both gravity cores from the seabed and geophysical data acquisition for characterizing the shallow subsurface layers. The gravity cores were characterized for physical and mechanical properties. The material properties were used for simulating injection and response of the seafloor to induced pressure. Geomechanical 2D and 3D simulations show that the reservoir may sustain very low overpressure before it fails. Hence, this magnitude of overpressure may create a seafloor uplift of about a few millimeters to a couple of centimeters. The monitoring techniques are therefore being designed to capture uplift in this order of magnitude during the injection operation

Monitoring CO₂ storage sites onshore and offshore using InSAR data and strain sensing fibre optics cables

A key requirement for geological CO2 storage is site integrity management and monitoring during operation through to the post decommissioning period. This paper focuses on monitoring deformation of the ground surface and seabed as a proxy for overall deformation in the reservoir and surrounding layers. The objective is to inform, based on deformation data, on how the reservoir is responding to CO2 injection and to ensure any issues with regard to storage integrity are rapidly detected. The magnitude and pattern of deformation at the surface reveals geomechanical/hydromechanical processes that occur in reservoir due to CO2 injection. We acquired deformation data from the In Salah CO2 injection site and from four additional study cases during the course of this study; one in the onshore UK, the other a combined campaign onshore Norway and offshore Germany, and the third in onshore Japan. Significant developments in measurement techniques, processing tools and interpretation algorithms were developedthrough this project. Models were then developed to simulate the observed data and to couple surface deformation to displacement in the subsurface. The results show millimeter-scale deformations in the subsurface have a signature at the surface that can be captured by the tools and workflows developed in this project. These deformations, particularly the patterns, are important factors to consider when monitoring a CO2 storage site