Isabelle Lecomte

University of Bergen | UiB · Department of Earth Science

Sills play a leading role in the transport of magma in sedimentary basins. The contact between sills and host rocks reflects the acting emplacement processes during sill propagation and evolution. Recent studies have shown that the propagation of sills and dykes is strongly influenced by the lithology of the host rocks, but none have detailed docum...

Sand injection complexes are important components of petroleum systems. They form sub-vertical and sub-horizontal networks of permeable sandstone reservoirs, which often contain commercial hydrocarbons. In the subsurface, defining the geometry and distribution of sandstone intrusions and their reservoir quality is challenging, and constitutes a hig...

Faults with throws that fall below vertical seismic resolution are challenging to identify in reflection seismic datasets. Nevertheless, such small-scale faults may still affect the seismic images, and in this study, we build seismic models of outcrop analogues to investigate how. Using photogrammetry from faults affecting Oligocene to Miocene carb...

Seismic resolution and illumination issues are sources of challenges in the detailed imaging and detection of subsurface fault architecture and fluid migration. Improved constraints on resolution can provide input into monitoring requirements and detectability of CO2 leakage, and fault-sealing properties during subsurface visualization of migration...

Dahlin et al. (2020) shows the first digital outcrop model from the high Arctic Island of Bjørnøya. The model of the Landnørdingsvika cliff in SW Bjørnøya highlights a spectacularly exposed outcrop of the Mid-Late Carboniferous Landnørdingsvika and Kapp Kåre Formations. The succession shows the interplay between mid-late Carboniferous sea-level flu...

Faults are characterized by a complex internal architecture. In carbonates, the geometry, attitude, and distribution of fault-related fractures and subsidiary faults can largely affect the petrophysical properties and hydraulic behavior of the fault zone. This work investigates the footwall damage zone of a seismic-scale normal fault (throw ∼ 300 m...

The Covid-19 pandemic occurred at a time of major revolution in the geosciences – the era of digital geology. Digital outcrop models (DOMs) acquired from consumer drones, processed using user-friendly photogrammetric software and shared with the wider audience through online platforms are a cornerstone of this digital geological revolution. Integra...

Small-scale (< 20 m), non-resolvable sand injectites can constitute a large part of the net-to-gross volume and affect fluid flow in the reservoir. However, they may also cause challenges for well placement and reservoir development because they are too small to be reliably constrained by reflection seismic data. It is therefore important to better...

We analyze data from passive and active seismic experiments conducted in the Adventdalen valley of Svalbard in the Norwegian Arctic. Our objective is to characterize the ambient wavefield of the region and to investigate permafrost dynamics through estimates of seismic velocity variations. We are motivated by a need for early geophysical detection...

Seismic migration commonly yields an incomplete reconstruction of the Earth model due to restricted survey aperture, band‐limited frequency content, and propagation effects. This affects both illumination and resolution of the structures of interest. Through the application of spatial convolution operators commonly referred to as point‐spread funct...

Seismic mapping of subsurface faults is hampered by factors such as seismic resolution, velocity control for depth conversion and human bias. Here, we explore the challenges and pitfalls related to interpreting normal faults by comparing objective and subjective uncertainties. A panel of 20 interpreters, with different geoscientific backgrounds, in...

The Covid-19 pandemic occurred at a time of major revolution in the geosciences – the era of digital geology. Digital outcrop models (DOMs) acquired from consumer drones, processed using user-friendly photogrammetric software and shared with the wider audience through online platforms are a cornerstone of this digital geological revolution. Integra...

Paleokarst originate from collapse, degradation and infill of karstified rock, and typically feature spatially heterogeneous elements such as breakdown products, sediment infills and preserved open cavities on all scales. Paleokarst may further contain aquifer or hydrocarbon reservoirs as well as pose a drilling hazard during exploration. Seismic c...

Understanding and predicting architecture and facies distribution of syn-rift carbonates is challenging due to complex control by climatic, tectonic, biological and sedimentological factors. CarboCAT is a three-dimensional stratigraphic forward model of carbonate and mixed carbonate-siliciclastic systems that has recently been developed to include...

Paleokarst are products of carbonate cave deactivation, collapse and burial. The cave geometry and most of the petrophysical properties are preserved and could act as petroleum reservoirs. In this study, test flow simulations were done on a porous media with dimensions of 614 x 100 x 30 m3 and cells of 2 x 2 x 2 m3. The cave diameter is varied from...

Forward seismic models of outcrop analogues are used in hydrocarbon exploration to generate more coherent geological-geophysical models that provide an important scale link between outcrops and seismic survey data. Exploration within slope carbonate plays can be problematic with uncertainties about the reservoir geometries, distribution and volumes...

The high Arctic is a remote place, where geoscientific research and teaching require expensive and logistically demanding expeditions to make use of the short field seasons. The absence of vegetation facilitates the use of modern photogrammetric techniques for the cost-effective generation of high-resolution digital outcrop models (DOMs). These geo...

We investigate the correlation between rock properties and seismic expression in sand-injectite complex within shallow depositional systems. We first upscale 1D microstructural observations to a 3D geological-scale model, and then perform 3D seismic forward modeling. Using an existing theoretical rock-physics investigation in brine-and gas-saturate...

Shear zones are common strain localization structures in the middle and lower crust and play a major role during orogeny, transcurrent movements and rifting alike. Our understanding of crustal deformation depends on our ability to recognize and map shear zones in the subsurface, yet the exact signatures of shear zones in seismic reflection data are...

Flow pattern controls in Paleokarst Reservoirs

Shear zones play an important role in localizing crustal deformation during rifting, continental break up and passive margin formation. Because shear zones change physical rock properties relative to the surrounding undeformed rocks, we can image them in seismic reflection data. The exact seismic signature of shear zones is however still largely un...

Sandstone intrusions form large bedding-discordant sandstones that intruded into finer grained, less permeable host strata. They form naturally sand-propped hydraulic fractures that constitute a connected network of permeable conduits through which fluids escape to the Earth's surface. Saucer-shaped sandstone intrusions are among the largest volume...

Characterizing and modelling reservoirs hosted in karstified formations is highly challenging. Overprinting of initial depositional facies architectures by pre-and/or post-burial solution features can create substantial, but often spatially unpredictable, secondary porosity. Infilling of larger cavities by cements and sediments, ranging from lamina...

Karst is a type of landscape formed by dissolution of soluble rocks such as carbonates. Caves are common subsurface karst features and develop where water percolates through the host rock and creates cave-passages through dissolution. With time and burial, the cave-passages may collapse or fill in with sediments, but drill bit-drops indicating open...

On Svalbard (Arctic Norway), a pilot-scale research project has been established to investigate the feasibility of storing locally produced CO 2 in geological aquifers onshore. Drilling, geophysical and geological data acquisition and water-injection tests confirm the injectivity and storage capacity of the naturally fractured and compartmentalised...

Seismic petrofacies characterisation in low net‐to‐gross reservoirs with poor reservoir properties such as the Snadd Formation in the Goliat field, requires a multidisciplinary approach. This is especially important when the elastic properties of the desired petrofacies significantly overlap. Pore fluid corrected end‐member sand and shale depth tre...

Interpretation of seismic data has played a major role in recent advances in the studies of igneous sill complexes. Seismic modelling studies based on field analogues represent a promising tool to close the scale gap between observations from outcrops and seismic data and support seismic interpretation. Virtual outcrop models are commonly used to i...

Application of 3D seismic reflection data to igneous systems in sedimentary basins has led to a revolution in the understanding of mafic sill complexes. However, there is considerable uncertainty on how geometries and architecture of sill complexes within the subsurface actually relates to geometries in seismic reflection data. To provide constrain...

Application of 3D-seismic reflection-data to igneous systems in sedimentary basins has led to a revolution in the understanding of mafic sill-complexes. However, there is considerable uncertainty on how geometries and architecture of sill complexes within the subsurface relates those imaged in seismic reflection-data. To provide constraints on how...

An integrated innovative multidisciplinary approach has been used to estimate effective porosity (PHIE), shale volume (Vsh) and sand probability from prestack angle gathers and petrophysical well logs within the Lower Triassic Havert Formation in the Goliat Field, SW Barents Sea. A rock physics feasibility revealed the optimum petrofacies discrimin...

This paper focuses on modelling the seismic response to a theoretical CO2 injection into the upper reservoir at the Longyearbyen CO2 Lab site in Svalbard, Norway. The modelling aims to assess the monitoring potential of a carbon capture and storage site. We demonstrate the effect of reservoir porosity and CO2 concentration on seismic reflection amp...

An integrated multidisciplinary workflow has been implemented for quantitative lithology and fluid predictions from prestack angle gathers and well-log data within the Realgrunnen Subgroup in the Goliat Field, southwestern Barents Sea. We have first performed a qualitative amplitude-variation-with-angle (AVA) attribute analysis to assess the spatia...

The sequestration of CO2 in subsurface reservoirs constitutes an immediate counter‐measure to reduce anthropogenic emissions of CO2, now recognised by international scientific panels to be the single most critical factor driving the observed global climatic warming. To ensure and verify the safe geological containment of CO2 underground, monitoring...

The mid-Norwegian Margin is regarded as a type-example of a volcanic rifted margin, formed prior to, and during, Paleogene break-up of the NE Atlantic. The area is characterized by the presence of voluminous basaltic complexes such as extrusive lava and lava delta sequences, intrusive sills and dikes, and hydrothermal vent complexes. We present a d...

Relay ramps can act as conduits for fluid flow in producing hydrocarbon reservoirs, but the two bounding faults are often at the limit of seismic resolution. To study the impact of relay ramps and their fluid composition on seismic data, we present an integrated workflow combining flow simulation in a geomodel of an outcrop relay ramp, forward seis...

Fault activity and sandstone-body geometries and spread, all bear significant weight to understanding the potential hydrocarbon systems on the NW Barents Shelf. Synthetic seismic modelling of onshore sedimentary successions provides insight into the seismic resolution and expression of various sedimentological features on Edgeøya: (i) sandy growth...

This study describes a successful multidisciplinary work flow for quantitative lithology prediction from prestack angle gathers and petrophysical well log data within the Realgrunnen Subgroup in the Goliat Field, Norwegian Barents Sea. An amplitude-versus-angle (AVA) qualitative attribute analyses was performed to assess the spatial distribution of...

Seismic modelling is necessary to understand elasticwave propagation in the subsurface. Modelling is costeffective and insightful, as long as adequate methods are used. An ideal seismic-modelling strategy is to generate complete synthetic seismograms for realistic earth models, then process them as performed with real seismic data. These complete s...

In hydrocarbon exploration the characterization of the petroleum play at sub-seismic scale is an issue. Moreover, seismic responses of carbonates are very problematic. Within platform-to-slope carbonate systems in which resedimented slope deposits represent the oil-bearing target reservoir, an accurate sub-seismic scale reconstruction of the reserv...

Often, interpreters only have access to seismic sections and, at times, well data, when making an interpretation of structures and depositional features in the subsurface. The validity of the final interpretation is based on how well the seismic data are able to reproduce the actual geology, and seismic modeling can help constrain that. Ideally, mo...

Using an integrated workflow from an outcrop model in the Arches National Park, Utah, fluid flow simulation to seismic modelling, we intend to study the impact of a relay ramp system and its fluid composition on seismic images. Faulting in porous sandstone is associated to deformation bands that decrease the porosity and permeability locally. Based...

Seismic models of outcrops can contribute effectively to the interpretation of seismic data. In fact, they are essential for qualifying petroleum targets, because they bridge a critical gap in both resolution and scale between architectural geometries observed in outcrops and in seismic data. Synthetic seismic reflectivity models were generated fro...

This study shows the importance of incorporating outcrop analogs in the analysis of subsurface reservoirs. Within this context, the detailed study of outcropping surface analogues combined with the Geologic model building and validation of the geological sections, brings fundamental constraints in performing reservoir modelling, thus providing more...

Seismic images are often provided to interpreters as the only element to work with, besides well logs. However, the possible geological complexity of both overburden and reservoir, as well as survey, wavelet, and processing are all parameters affecting seismic images. An ideal seismic modelling would be using full-waveform methods to generate compl...

Methods based on the seismic P-wave, seismic surface wave, and apparent resistivity are commonly used in the solution of several near-surface problems. However, the solution nonuniqueness and the intrinsic limitations of these methods can cause inconsistency in the final results. Dispersion curves of surface waves, P-wave traveltimes, and apparent-...

The Trias North project targets the evolution of the Triassic to early Jurassic Barents Shelf, covering many aspects of the shelf's infrastructure. Growth-faults and their interaction with marginal marine deposits is one of the project targets. Southern Edgeøya, Svalbard, offers outstanding exposures of extensional faults bounding half-grabens fill...

Although typically interpreted as 2D surfaces, faults are 3D narrow zones of highly and heterogeneously strained rocks, with petrophysical properties differing from the host rock. Here we present a synthetic workflow to evaluate the potential of seismic data for imaging fault structure and properties. The workflow consists of discrete element model...

The capability to correctly interpret microseismic datasets depends strongly on the completeness of the event catalogue and reliability of measurements. Location accuracy of a microseismic event is strongly controlled by azimuthal coverage defined by the source-receiver geometry. Furthermore, the detection limit is determined by the noise level and...

A seismic survey involving two distinct acquisition setups, with vertical and horizontal component geophones, has been carried out along the same line on a site presenting a simple vertical structure (peat, quick clays and bedrock) and no strong lateral variations. SH-wave refraction tomography and Rayleigh-wave dispersion inversion provided the sa...

Quick-clay landslides are a known hazard in formerly glaciated coastal areas. Some of Norway’s most densely populated areas are located in potential quick-clay zones and, hence, large efforts are devoted to map the distribution of quick clays. Here, we focus on one particular Norwegian site (Hvittingfoss, 100 km south-west of Oslo), which was remed...

Marine clay deposits in coastal, post-submarine areas of Scandinavia and North America may be subjected to quick clay landslides and hence significant efforts are being taken to map their occurrence and extent. Recently, considerable efforts by a number of researchers have been made to investigate areas of sensitive clay using a range of geophysica...

Quick-clay landslides are a known hazard in formerly glaciated coastal areas; hence, large efforts are devoted to map the distribution of quick clays. In this paper, we focus on one particular Norwegian site (Hvittingfoss, 80 km south-west of Oslo), which was remediated against potential landsliding in 2008. A set of geophysical methods including E...

As part of the world’s needs for CO2-injection test sites, the city of Longyearbyen in Svalbard is an interesting location for testing technologies related to carbon capture and storage (CCS) in a vulnerable arctic environment, being a closed energy system with a coal-fuelled power plant. Therefore, the University Centre in Svalbard (UNIS) establis...

Faults are 3D narrow zones of highly and heterogenously strained rocks, with petrophysical properties differing from the host rock, and are primary controls on fluid flow in reservoirs. We present a synthetic workflow to assess the potential of seismic data for imaging fault structure and internal properties. The workflow is based on a discrete ele...

Quick clay is a known hazard in formerly-glaciated coastal areas in e.g., Norway, Sweden and Canada. In this paper, we review the physical properties of quick clays in order to find a suitable, integrated and multi-disciplinary approach to improve our possibilities to accurately identify the occurrence of quick clay and map its extent both vertical...

This paper presents a novel approach to predict long-term settlement in the Trondheim harbour, mid Norway, from high-resolution shear-wave seismic reflection data, complemented with cone penetration test results (CPTU) and index soil properties from nearby boreholes in this reclaimed coastal area. The data enables sub-surface geo-characterisation i...

Complex velocity models, limitations in acquisition geometry and frequency bandwidth, give rise to distortions in prestack depth migrated (PSDM) images. Such distortions can be modelled as the 2D convolution between the actual reflectivity and a resolution function. In the case of Born scattering, the resolution function is referred to as point spr...

A combined record of onshore, high-resolution, shear-wave seismic and marine, P-wave seismic data shows the near-shore stratigraphic organisation of a fjord-valley fill at Trondheim, central Norway. The overall stratigraphy shows a typical fjord-valley fill of up to 160 m in thickness that is composed of glaciomarine and fjord-marine sediments over...

Sørfjord outside the village of Finneidfjord has a history of landsliding throughout the Holocene. The 1996 landslide -the focus of this study - has many characteristics typical of submarine landslides (well-developed slip plane, outrunner blocks, peripheral thrusting and lateral spreading). Due to its sheltered and accessible location, Finneidfjor...