Recent years have witnessed an alarming increase in quick-clay landslides in Nordic countries, such as in Alta (Norway), Gjerdrum (Norway), and Stenungsund (Sweden), resulting in substantial damages and loss of lives. This study focuses on the application of geophysical methods, particularly the Controlled-source Radio-magnetotelluric (CSRMT) technique, to understand the characteristics and model the geometry and possibly dynamics of quick clay in these regions. The CSRMT method, combines Radio-magnetotelluric (RMT) and Controlled-source Magnetotelluric (CSMT) techniques and offers an innovative approach for investigating the electrical resistivity of subterranean structures, crucial for identifying quick clay zones. The Rissa region in Norway provides a unique opportunity for this research due to its historical context and existing infrastructure for geophysical studies. The catastrophic Rissa landslide of 1978 led to an extensive national quick clay mapping initiative, forming the basis for this study. We have also collected Distributed Acoustic Sensing (DAS) data at Rissa, intending to integrate it with CSRMT data for comprehensive analysis. Borehole analyses at the Rissa site reveal a relatively simple stratigraphy with a flat terrain and a marine clay stratum about 20 meters thick. Quick clay layers, identifiable due to their higher electrical resistivity compared to marine clays, are sandwiched in borehole samples. Our study utilizes (CS)RMT to model these layers and assess the impact of seasonal variations on their characteristics. Data collection involved a 250-meter long CSRMT profile with a 10-meter station spacing conducted in both summer and winter seasons. The EnviroMT instrument from Uppsala University was used for data acquisition. This time-lapse approach was critical to study the resistivity differences due to seasonal variation at the quick clay site. Results from modelling the CSRMT data show a four-layer model including L1-L4. L2 appeared thicker in winter, possibly due to reduced freshwater. Conversely, in some locations, L2 appeared thicker. These findings show that CSRMT data can distinguish resistivity differences at a quick-clay site due to seasonal variations. This research offers significant insights into the modelling of seasonal variations of the resistivity related to changes in the water content which in turn might lead to development of areas with quick clays. The integration of CSRMT and DAS data presents a novel approach to studying these phenomena, potentially aiding in better understanding and predicting quick-clay landslide triggering. The findings are not only crucial for academic research but also have profound implications for infrastructure planning and disaster management in regions prone to quick-clay landslides.

Climate change is impacting the Arctic faster than anywhere else in the world. As a response, ecosystems are rapidly changing. As a result, we can expect rapid shifts in whale migration and habitat use concurrent with changes in human patterns. In this context, responsible management and conservation requires improved monitoring of whale presence and movement over large ranges, at fine scales and in near-real-time compared to legacy tools. We demonstrate that this could be enabled by Distributed Acoustic Sensing (DAS). DAS converts an existing fiber optic telecommunication cable into a widespread, densely sampled acoustic sensing array capable of recording low-frequency whale vocalizations. This work proposes and compares two independent methods to estimate whale positions and tracks; a brute-force grid search and a Bayesian filter. The methods are applied to data from two 260 km long, nearly parallel telecommunication cables offshore Svalbard, Norway. First, our two methods are validated using a dedicated active air gun experiment, from which we deduce that the localization errors of both methods are 100 m. Then, using fin whale songs, we demonstrate the methods' capability to estimate the positions and tracks of eight fin whales over a period of five hours along a cable section between 40 and 95 km from the interrogator unit, constrained by increasing noise with range, variability in the coupling of the cable to the sea floor and water depths. The methods produce similar and consistent tracks, where the main difference arises from the Bayesian filter incorporating knowledge of previously estimated locations, inferring information on speed, and heading. This work demonstrates the simultaneous localization of several whales over a 800 km area, with a relatively low infrastructural investment. This approach could promptly inform management and stakeholders of whale presence and movement and be used to mitigate negative human-whale interaction.

A detailed 120 km deep electromagnetic joint inversion model for the ultra-slow Mohns Ridge was constructed combining controlled source- and magnetotelluric data. About one third of mid-ocean ridges have a spreading rate less than 20 mm/yr1, but due to lack of deep imaging, factors controlling melting and mantle upwelling, depth to the lithosphere – asthenosphere boundary (LAB), crustal thickness and hydrothermal venting are not well understood for this class of ridges. Modern electromagnetic data have significantly improved understanding of fast-spreading ridges, but have not been available for the ultra-slow ridges. The new inversion images show mantle upwelling focused along a narrow, oblique and strongly asymmetric zone coinciding with asymmetric surface uplift. Though the upwelling pattern shows several of the characteristics of a dynamic system, instead it likely reflects passive upwelling controlled by slow and asymmetric plate movements. Upwelling asthenosphere and melt are enveloped by the 100 Ωm contour denoted the electrical LAB (eLAB). This transition may represent a rheological boundary defined by a minimum melt content. We also find that a model where crustal thickness is directly controlled by the melt-producing rock volumes created by the separating plates can explain the thin crust below the ridge. Fluid convection extends for long lateral distances exploiting high porosity at mid crustal levels. The magnitude and long-lived nature of such plumbing systems could promote venting at ultra-slow ridges. Further, active melt emplacement into ca 3 km thick oceanic crust culminates in an inferred crustal magma chamber draped by fluid convection cells emanating at Loki´s Castle hydrothermal field.

The North Sea has arguably the most extensive geophysical data coverage of any glacier-influenced sedimentary regime on Earth, enabling detailed investigation of the thick (up to 1 km) sequence of Quaternary sediments that is preserved within the North Sea Basin. At the start of the Quaternary, the bathymetry of the northern North Sea was dominated by a deep depression that provided accommodation for sediment input from the Norwegian mainland and the East Shetland Platform. Here we use an extensive database of 2D and 3D seismic data to investigate the geological development of the northern North Sea through the Quaternary. Three main sedimentary processes were dominant within the northern North Sea during the early Quaternary: 1) the delivery and associated basinward transfer of glacier-derived sediments from an ice mass centred over mainland Norway; 2) the delivery of fluvio-deltaic sediments from the East Shetland Platform; and 3) contourite deposition and the reworking of sediments by contour currents. The infilling of the North Sea Basin during the early Quaternary increased the width and reduced the water depth of the continental shelf, facilitating the initiation of the Norwegian Channel Ice Stream.

The Veslemoy High is located in the southwestern sector of the Barents Sea and its geological evolution is strictly linked to the geodynamic development of the Norwegian region. The tectonic evolution of the Veslemoy High and several other structural elements of the Barents Sea remains poorly understood mostly because of a general lack of stratigraphic control, high-quality data and the complex interplay of geodynamic episodes, which has prevented the structures and ages of several stratigraphic units to be correctly constrained.This study used 3-D and 2-D seismic reflection data, integrated with well data to reconstruct the geological history of the Veslemoy High area. The methods here used include seismic interpretation of several horizons and faults, seismic-well data calibration (well 7219/8-1S) and well data (7216/11-1S; 7218/11-1; 7218/8-1; 7219/8-1S). Such an investigation led to the definition of several compressional andextensional tectonic phases, which affected the area most especially in pre-Cenozoic time. The oldest compressional phase here documented is Late Cretaceous and is marked by large-scale anticlines and synclines (about 10 km wavelength). Following this tectonic phase, the study area was affected by a system of mainly west dipping normal faults, creating several half graben structures. In some cases, these grabens display evidences of slight positive inversion. Analysis of the Late Cretaceous sequence provides interesting markers of sediments infilling patterns, erosional surfaces, uplift, tilting, faulting, extensional and contractional structures. All these structures point to a complex interplay of Pre-, Syn- and Post-Late Cretaceous tectonic activities. Importantly, the Lower Regional Unconformity (LRU), Upper Regional Unconformity (URU), stratigraphic terminations, and faults are significant tectonic markers in the Veslemoy High area and in surrounding basins. Tectonic structures documented here are characteristics of the Mesozoic and Cenozoic geological framework of the NE Atlantic margin.

Summary Conventional methods for positioning of the well bore during drilling are based on using down hole logging. Measurements from these tools are used to compute the well path. To get an understanding of where the well is in the subsurface the well path is projected onto the seismic image from the particular area. This procedure is, in general, problematic as there are uncertainties in the measurements, the seismic image and methods, and differences in accuracy between the methods in use. The surface seismic while drilling (SSWD) method is a new method that uses surface seismic to image well paths. The advantage of SSWD is that no down hole tools are needed to image the well. There is also no need for stopping the drilling operations to image the well. We discuss the SSWD and conventional methods for well bore positioning and show examples on how the SSWD method is used to home-in a relief well to stop a blowing well.

Diffractions from boreholes can be made visible using surface seismic data, subject to certain favorable conditions. This makes diffraction processing and imaging a more natural complement to the Surface Seismic monitoring While Drilling (SSWD) method than traditional reflection processing, which suffers from limitations in illumination and resolution. We discuss the SSWD method in combination with diffraction imaging and demonstrate its potential on a field data set. Presentation Date: Wednesday, October 19, 2016 Start Time: 8:50:00 AM Location: 168 Presentation Type: ORAL

Summary Borehole diameters are typically much smaller than the dominant seismic wavelength and near-vertical borehole geometries do not favor reflection response at a surface acquisition. For these reasons - resolution and illumination - we study the diffraction response from boreholes on surface seismic data. Diffractions from boreholes are observable on surface seismic data under certain relatively mild conditions (sufficient frequency content, signal-to-noise and impedance contrast between the borehole and surrounding rock), and can be used to trace its trajectory. This is the objective of Surface Seismic monitoring While Drilling. In particular, we show that organizing the diffraction imaging in a time-lapse and target-oriented fashion can result in a very efficient and accurate way of monitoring the borehole during drilling.

Magmatic activity during the Cenozoic break-up and the opening of the Norwegian-Greenland Sea is preserved in the Jan Mayen Microcontinent. As the emplacements of magmatic rocks on continental margins have implications for both petroleum and mineral exploration. This work is aimed at interpreting evidence of magmatic activity from seismic reflection data and how it influences the geodynamic evolution of the study area. Igneous rocks are interpreted as positive, high amplitude reflections which are also characterized by complex geometries, abrupt terminations in adjacent sediments, and local transgression across stratigraphy levels. In the study area, they are acoustically hard and are either concordant or discordant to sedimentary bedding. The two major seismic facies interpreted in the study area are a) irregular, bedding discordant, intrusive rock, i.e., dikes, saucer-shaped, and bowl-shaped intrusions and b) horizontal, layered, and bedding parallel positive reflections e.g., pillow basalts and tabular sills. The Jan Mayen microcontinent is delimited by these igneous rocks into a western margin rich in extrusive rocks and an eastern region characterized by intrusive igneous rocks. Volcanic sills in the study area can be mapped independently on seismic profiles. They are often associated with post-depositional deformation of the Paleocene rocks. Individual sills exhibit complex fragmentation and are found in close proximity of faults. Base on their interaction with volcanic sills, faults in the study area can be grouped as deep-seated and hard-linked faults, intermediate and shallow faults. The important piece of information from this work is that magmatic intrusions influenced configuration of faults and are sued as the major control on structural reactivation in the study area. The volcanic rocks in Jan Mayen microcontinent were emplaced in Early Eocene during the opening of the southern Greenland Sea. A second phase of volcanic emplacement is related to re-configuration of plate orientation and motion in Oligocene times

Summary Outcrop models are an invaluable help to calibrate seismic imaging techniques and assess their impact on interpretation of exploration and production targets. We investigate reservoir models based on an outcrop at Kvalhovden, east-Spitsbergen, and evaluate images obtained by regular migration and diffraction imaging. Diffraction images demonstrate the potential to enhance image resolution to beyond the traditional Rayleigh criterion and reveal considerable more structural detail. The use of high-frequency and high-resolution data modeling makes these investigations relevant for both production and exploration. The objective of this paper is to increase the awareness of the interpretation community of enhanced resolution capabilities of seismic imaging.

Magnetic survey methods are used to locate the blowing wellbore when drilling a relief well. If no magnetic material is present in the openhole section of the blowing well, the last set casing shoe is the deepest possible intersection point. A deeper intersection point will increase the hydrostatic head, increase the frictional pressure drop and allow a lower density kill fluid to be used. A new potential method called surface seismic while drilling (SSWD), could make it possible to intersect the blowing well below the casing shoe. This method is not dependent of any casing or steel tubular present in the well to identify the relative wellbore positions. The SSWD method is based on a surface seismic source generator and a receiver array located on the seabed. Preliminary simulations indicate that it is possible to locate the wellpaths of the two wells on the seismic data. This method will allow real-time seismic monitoring of the well paths without interfering with the drilling operation. This can allow for more precise relative wellbore positioning. To investigate the benefits of a deeper intersection, a simulation model was prepared. A vertical offshore well consisting of 2000 meters of casing, and a 1000-meter openhole section were used. The well was killed dynamically by circulating seawater at high rates into the blowing wellbore. Compared to a casing shoe intersection, simulations show that a bottom hole intersection would reduce the flow rate and pump pressure by approximately 48% and 55%, respectively. The required kill mud weight was reduced by 24 %. The seismic method may also be used in conventional well killing operation to provide additional information of the position of the two wellbores and potentially reduce the time needed to drill the relief well. This paper presents the SSWD method and the potential improvements in relief well drilling and well killing. Introduction A blowout is by far the most severe consequence of loss in well control. Because of the tremendous powers at play, a blowout can rapidly become a disastrous event. Large volumes of hydrocarbons and toxic gasses can be released to the surface, potentially causing huge environmental damage and put human lives at jeopardy. Considering the resources required to stop the blowout, penalties imposed on the liable, reduction in share values, lost hydrocarbon resources, and destroyed reputation of companies involved, a blowout often becomes a dramatic and costly ordeal. If loss in well control escalates to a blowout, it is important that the well is brought under control fast and safely, and in a terminal manner. This might require a relief well to be drilled to intersect the blowing well at a certain depth, and kill it by pumping liquid into the blowing wellbore until overbalance is retained. Modern relief wells are drilled to directly intersect the blowing wellbore. The target is often smaller than 10 inches and the depth can be several thousand meters. Conventional surveying techniques do not offer the accuracy needed to accomplish this, and for that reason ranging tools that home in on steel tubular in the blowing well is used once the relief well is close enough. This often means that the last set casing shoe is the deepest point available for a relief well. If an extended openhole section

Magnetic survey methods are used to locate the blowing wellbore when drilling a relief well. If no magnetic material is present in the openhole section of the blowing well, the last set casing shoe is the deepest possible intersection point. A deeper intersection point will increase the hydrostatic head, increase the frictional pressure drop and allow a lower density kill fluid to be used. A new potential method called surface seismic while drilling (SSWD), could make it possible to intersect the blowing well below the casing shoe. This method is not dependent of any casing or steel tubular present in the well to identify the relative wellbore positions. The SSWD method is based on a surface seismic source generator and a receiver array located on the seabed. Preliminary simulations indicate that it is possible to locate the wellpaths of the two wells on the seismic data. This method will allow real-time seismic monitoring of the well paths without interfering with the drilling operation. This can allow for more precise relative wellbore positioning. To investigate the benefits of a deeper intersection, a simulation model was prepared. A vertical offshore well consisting of 2000 meters of casing, and a 1000-meter openhole section were used. The well was killed dynamically by circulating seawater at high rates into the blowing wellbore. Compared to a casing shoe intersection, simulations show that a bottom hole intersection would reduce the flow rate and pump pressure by approximately 48% and 55%, respectively. The required kill mud weight was reduced by 24 %. The seismic method may also be used in conventional well killing operation to provide additional information of the position of the two wellbores and potentially reduce the time needed to drill the relief well. This paper presents the SSWD method and the potential improvements in relief well drilling and well killing. Introduction A blowout is by far the most severe consequence of loss in well control. Because of the tremendous powers at play, a blowout can rapidly become a disastrous event. Large volumes of hydrocarbons and toxic gasses can be released to the surface, potentially causing huge environmental damage and put human lives at jeopardy. Considering the resources required to stop the blowout, penalties imposed on the liable, reduction in share values, lost hydrocarbon resources, and destroyed reputation of companies involved, a blowout often becomes a dramatic and costly ordeal. If loss in well control escalates to a blowout, it is important that the well is brought under control fast and safely, and in a terminal manner. This might require a relief well to be drilled to intersect the blowing well at a certain depth, and kill it by pumping liquid into the blowing wellbore until overbalance is retained. Modern relief wells are drilled to directly intersect the blowing wellbore. The target is often smaller than 10 inches and the depth can be several thousand meters. Conventional surveying techniques do not offer the accuracy needed to accomplish this, and for that reason ranging tools that home in on steel tubular in the blowing well is used once the relief well is close enough. This often means that the last set casing shoe is the deepest point available for a relief well. If an extended openhole section exists below the casing shoe, this cannot be utilized during the killing operation.

Abstract Magnetic survey methods are used to locate the blowing wellbore when drilling a relief well. If no magnetic material is present in the openhole section of the blowing well, the last set casing shoe is the deepest possible intersection point. A deeper intersection point will increase the hydrostatic head, increase the frictional pressure drop and allow a lower density kill fluid to be used. A new potential method called surface seismic while drilling (SSWD), could make it possible to intersect the blowing well below the casing shoe. This method is not dependent of any casing or steel tubular present in the well to identify the relative wellbore positions. The SSWD method is based on a surface seismic source generator and a receiver array located on the seabed. Preliminary simulations indicate that it is possible to locate the wellpaths of the two wells on the seismic data. This method will allow real-time seismic monitoring of the well paths without interfering with the drilling operation. This can allow for more precise relative wellbore positioning. To investigate the benefits of a deeper intersection, a simulation model was prepared. A vertical offshore well consisting of 2000 meters of casing, and a 1000-meter openhole section were used. The well was killed dynamically by circulating seawater at high rates into the blowing wellbore. Compared to a casing shoe intersection, simulations show that a bottom hole intersection would reduce the flow rate and pump pressure by approximately 48% and 55%, respectively. The required kill mud weight was reduced by 24 %. The seismic method may also be used in conventional well killing operation to provide additional information of the position of the two wellbores and potentially reduce the time needed to drill the relief well. This paper presents the SSWD method and the potential improvements in relief well drilling and well killing.

In sequence stratigraphic interpretations, the key premise is that stratal surfaces effectively represent geologic timelines. When applied to seismic sections, the fundamental assumption is that primary reflections generally mimic stratigraphic timelines. The main objective of this study was to test how well key reflectors in a seismic section couple to timelines. To achieve the high level of ground control needed for such testing, we combined photogrammetry and traditional sedimentologic fieldwork to optimize the geologic model. We relied further on petrophysical analysis to derive anumerical model suitable for the simulation of seismic data. In spite of laterally discontinuous vertical-impedance contrasts (VICs), false seismic continuity was created, and we observed frequent decoupling of seismic reflectors and stratigraphic timelines. These observations demonstrate how the low-frequency seismic method fails to image normal complexity in a stratigraphic unit. A seismic correlation test showed that the interpreters made numerous mistakes and that such mistakes are very difficult to avoid. The failure of a fundamental assumption, as illustrated here, creates serious problems for the sequence stratigraphic concept when applied to detailed correlation analysis on seismic sections.

Marine controlled source electromagnetic (MCSEM) survey termed as Seabed Logging (SBL) can be used for detection of deeply buried hydrocarbons. The method has been verified on known hydrocarbon fields offshore Angola and Norway. Here we present SBL data across an offshore arch in the Norwegian Sea. A horizontal electric dipole source induced increased SBL responses (up to 250% gain in MVO) measured at the south-western part of the study area compared to south-eastern part. This finding satisfies the existence of strong seismic reflectors representing sills with ~300 øm resistivity within the depth range between ~1100 and 2500 m below the seafloor. Remote detection of high-resistivity strata shows fairly good agreement with forward 3-D SBL modelling simulation results. A comparatively better match between modelled and measured data was achieved by introducing a moderately high resistive (10 øm) layer correspond to moderately strong seismic reflector 1000 m below the seafloor at the central part of the structure. Likely candidates for this layer could either be a HC layer or a thin, highly fractured and discontinuous sill. However this resistivity for the sill layer (10 øm) is probably unrealistically low. If the resistivity is kept at 300 μÙm, the sill must be very thin and possibly not visible on the seismic section. It therefore, suggests that the measured SBL response cannot be fully explained by the simplified geological model with sills alone.

P058 A SEA BED LOGGING (SBL) CALIBRATION SURVEY OVER THE ORMEN LANGE GAS FIELD Introduction 1 Remote resistivity sensing of buried resistive layers in conductive sediments a concept called Sea Bed Logging (SBL) has been demonstrated both theoretically by Kong et al. (2002) and Eidesmo et al. (2002) and in practice by a survey over a known oil field offshore Angola in November 2000 (Ellingsrud et al. 2002). The Angola survey was run over an area which is ideal for the SBL technique mainly due to large water depth and shallow reservoir. In November 2002 ElectroMagnetic GeoServices (emgs) established by

Remote resistivity sensing of buried resistive layers within conductive sediments, a concept called Sea Bed Logging (SBL), has been proven successfully by several surveys. A survey carried out offshore Angola proved to be ideal for the SBL technique due to large water depths, short distances from the sea floor to the reservoirs and high resistivity contrasts between the overburden and the hydrocarbon bearing zones. Another survey over the Ormen Lange gas field, offshore Norway, demonstrated that the technique has high potential also in more adverse areas with rough sea floor topography, rather large distance from the seafloor down to the reservoir and relatively low hydrocarbon saturation (low resistivity).

D-08 REMOTE DETECTION OF HYDROCARBON FILLED LAYERS USING MARINE CONTROLLED SOURCE ELECTROMAGNETIC SOUNDING 1 T. EIDESMO 1 S. ELLINGSRUD 1 L.M.MACGREGOR 3 S. CONSTABLE 2 M.C.SINHA 3 S. JOHANSEN 4 H. WESTERDAHL 5 and F.N.KONG 5 Introduction Measurements of sub-seafloor electrical resistivity obtained by wire line logging of wells have traditionally played a crucial role in hydrocarbon exploration and reservoir assessment and development. However there are clear advantages to developing non-invasive geophysical methods capable of providing similar information albeit at a lower vertical resolution. The vast saving in terms of avoiding the costs of drilling test wells into structures that