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Seismic'imaging'of'fault'zones'

1.#Relevance#relative#to#the#call#for#proposals#This project addresses the “Exploration and Reservoir Characterization” topic of the

call. It does so by proposing a modelling approach to better understand fault zone evolution and seismic response. Improved understanding of these two processes can lead to the development of principles for the seismic characterization of fault zones. This can contribute to a better representation and forecasting of reservoirs in the many areas in which fault zones have impact such as drilling, sealing and leaking in hydrocarbon and CO2 systems, and hydrological and geothermal flow.

2.#Aspects#relating#to#the#research#project##2.1.'Background'and'status'of'knowledge''

Faults play a major role in restricting or enhancing fluid flow in reservoirs (Knipe et al., 1998; Sorkhabi and Tsuji, 2005). Although usually interpreted as simple surfaces offsetting the stratigraphy, faults are not discrete planes, but rather zones/envelopes of more or less deformed rock with a complex 3D geometry and internal structure, at a wide range of scales of observation (Figure 1). The internal structure and resulting distribution of petrophysical properties inside the fault envelopes act as primary controls on fluid flow in faulted reservoirs and determine fault-sealing capacity over geological and production time scales. This has major implications in areas such as hydrocarbon exploration and production (e.g. Wibberley et al., 2008), CO2 sequestration (e.g. Nelson et al., 2009; Dockrill and Shipton, 2010), hydrologic and geothermal systems (e.g. do Nascimento et al., 2004; Majer et al., 2007), and drilling (e.g. Stewart and Holt, 2004).

Figure 1. Fault zones at different scales of observation. a. Metre and b. Decametre size fault zones in Western Sinai. c. Hectometre size fault zone in the Visund field, northern North Sea (Færseth et al. 2007). Fault zones in a and b are subseismic, while fault zone in c is large enough to be imaged on seismic.

Despite of the awareness of the impact of fault zones on reservoir connectivity, we still lack the sufficient understanding to fully represent fault zones in reservoir models. The conventional approach is to consider fault zones as 2D membranes, which hinders a representation of 3D fault zone internal structure and fluid flow (Manzocchi et al. 2008). Recent initiatives to include fault zones as 3D volumetric entities (e.g. Petromaks-funded

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“Fault Facies” project. Tveranger et al., 2008) have resulted in a more detailed representation of the structure and fluid flow of fault zones, and an improved understanding of their associated uncertainty (Soleng et al. 2007; Fredman et al. 2008; Fachri et al. in press). However, a main challenge in these studies is the derivation of fault zone geometry and internal structure from the fault network and its displacement distribution. Fault zones are complex and highly heterogeneous, and there is no simple way of systematically describing or predicting their geometry and content. Part of the problem is that there is a lack of truly quantitative data on fault zone internal structure (Manzocchi et al. 2010). Most of the data are 2D outcrops of limited size (centimetres to decametres fault displacement, Figure 2). Furthermore, for specific combinations of lithology and fault displacement there are a limited number of outcrops, thus causing difficulties in the statistical handling of the data for generic purposes. This, together with the large spread of the data (fault zone thicknesses can vary as much as 3 orders of magnitude for a given fault displacement, Figure 2) and the fact that fault zone geometry and internal structure can vary considerably in 3D (Childs et al., 1996), make impossible to derive a systematic understanding of fault zones for reservoir characterization. These limitations introduce significant uncertainties in fault seal analysis and prediction of reservoir behaviour (Færseth et al., 2007; Manzocchi et al. 2010).

Figure 2. Childs et al. (2009) compilation of a. Fault Rock (Fault Core), and b. Fault zone thickness versus fault displacement data. The red dotted line indicates the transition between the subseismic and seismic scales. Most data are in the subseismic scale. Red dots are the few large, seismic scale faults described by Færseth et al. 2007. Notice that axes are logarithmic.

Interestingly enough 3D seismic data, which sample larger (100 to 1000 m) fault displacements (Figure 2) and have wider areal coverage, have not been used much to determine the 3D geometry and internal structure of fault zones. During the last two decades, 3D seismic interpretation has been the main tool for characterizing reservoirs. Major improvements have been developed, mainly focused on fault delineation and seismic attributes to understand lateral continuity of horizons and sedimentary facies. Fault interpretation has been focused on techniques enabling identification and visualization of faults, but despite ubiquitous seismic examples that illustrate the volumetric nature of faults (Figure 3), faults are still analyzed and handled as surfaces.

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Figure 3. a. Seismic example of a fault zone. Red lines are the standard interpretation of faults as surfaces. Green polygon is a more accurate interpretation of a fault zone as a volume. b. Close-up of rectangular region in a. Lateral changes in continuity and amplitude illustrate the complexity of the fault zone.

One of the first studies emphasizing the value of 3D seismic data to extract information about fault zones is Townsend et al. (1998). These authors document amplitude reductions close to faults, with the greatest reductions in the largest faults. We obtained similar results in the analysis of 3D seismic data from the Askeladd field in the Barents Sea (Nicolaisen, 2009; Figure 4). Since Townsend et al. (1998) very little has been published further exploring these ideas. Two works in the last years are worthy exceptions: Dutzer et al. (2009) use a seismic anomaly based, automatic region growing algorithm to define fault zones from a pre-identified fault skeleton. Long and Imber (2010) use an apparent dip attribute to determine the spatial distribution of fault related deformation, and thus the extent of fault zones. These works are the state of the art in fault interpretation, and illustrate the volumetric nature of faults. Delimiting fault zones, however, is not straightforward. Fault zones are at the limit of seismic resolution and the extracted volumes and their content vary according to the attribute used, and the nature and level of deformation (Dutzer et al., 2009).

Figure 4. RMS amplitude on the Base Cretaceous horizon showing changes across a normal fault zone in the Askeladd field (Barents Sea). a. Amplitude map. Lines indicate the location of sections 1 to 4. b. Amplitude anomalies. Dashed, red lines indicate the fault zone. c. Distribution of throw along the fault. 1 to 4 refer to the sections in a and b. Notice that amplitude anomalies correlate with fault throw. From Nicolaisen (2009).

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Figure 4 and the studies mentioned above highlight the potential of using 3D seismic

for the characterization of fault envelopes. However, several questions remain; for example, what is the general applicability of these results? Can we actually map the geometry and internal structure of fault zones using standard 3D seismic? Or if not, what sort of variations in acquisition parameters and processing we need in order to image these structures? Also, if we can map fault zones, what is the significance of their associated seismic anomalies? Can we correlate them with changes in petrophysical properties? Can the porosity and permeability structure of a fault envelope be inferred from its seismic anomalies?

The answers to these questions will only come from a clear understanding of the physics of fault zone evolution, and the propagation of seismic waves in fault zones. From a physical point of view, the seismic anomalies in fault zones result from changes in the grain and pore system and fluid pressures due to large plastic strains. Finite strain produces changes in porosity, density, seismic velocity, and therefore acoustic impedance (Couples et al., 2007). 2D seismic imaging of geomechanical fault zone simulations, with acoustic impedance derived from finite strain, shows that strain has significant impact on the resulting seismic image (Couples et al., 2007). Thus, there is potential for extracting information about the internal structure and properties of fault zones from their seismic response, by relating variations in seismic attributes to strain-induced changes in rock properties. This correlation is the driving argument of our project. Realistic 2D and 3D geomechanical simulations of faults (under different tectonic/stress regimes, lithologies, boundary conditions, etc.), and seismic modelling/imaging of the mechanical analogues, will be conducted to better understand the impact of different fault zone expressions on the resulting seismic image. Likewise, for a particular fault zone expression, different values of the acquisition parameters (offsets, frequencies, etc.) will be tested to establish the values required to image the fault zone. The results from this work can help to develop principles for the seismic characterization of fault zones. 2.2.'Approaches,'hypotheses'and'choice'of'method'# 3D seismic observations, in particular within fault zones, are limited to seismic imaging and quality, vertical and horizontal resolution of the data, type of reservoir, and deformation style (e.g. wide or narrow fault zone). To take into account all these variables, we propose an integrated approach that includes (Figure 5): (1) Geomechanical modelling of fault zone evolution and its effect on reservoir properties, (2) Seismic modelling of the geomechanical analogues using strain to estimate the distribution of acoustic properties in the model, and (3) A feasibility study on the interpretation of fault zones in real 3D seismic data.

Figure 5. Proposed research tasks and their integration

This approach will help us answer questions such as (1) The acquisition and processing parameters necessary to resolve the internal structure of fault zones (lateral and vertical resolution needed to image fault zones), (2) The effect on fault zone structure and its seismic response of variations in overburden, stress regime, lithology, fault geometries, and fault displacement fields, and (3) The correlation of seismic attributes in the fault zone with strain (and associated rock properties) and the attributes that best depict the internal structure of the fault zone. All these observations will provide guidelines for the seismic interpretation

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of fault zones. Part 3, the feasibility study, will allow us to verify the principles from the mechanical/seismic modelling in real, standard 3D seismic data. 2.2.1.'Geomechanical'modelling'of'fault'zones'' A realistic geomechanical model of faulting should include fault initiation, propagation, and linkage under any particular tectonic/stress regime. The model should be able to capture the extent of damage around fault zones and the transition from faulting to folding. We propose to use a discrete-element technique (DEM) to model these processes. This technique depicts the sedimentary rocks as an assemblage of spheres that obey Newton’s equations of motion and that interact with elastic forces under the influence of gravity (Hardy et al., 2009). Unlike continuum techniques, the DEM uses simple particle interactions, and therefore offers the ability to realistically and naturally simulate large deformations, fracturing, and fault development without complex re-meshing and/or artificial internal boundary conditions. Mechanical stratigraphy is handled with ease and complicated boundary conditions such as step-like velocity discontinuities at master faults are easy to implement.

The DEM code we propose to use is open and non-commercial, and most importantly, it was developed by a geologist (Stuart Hardy) with geologic problems in mind. The code has been extensively tested and applied to structural problems as varied as contractional and extensional fault propagation folding (Finch et al., 2003, 2004; Hardy and Finch 2006, 2007; Hardy, in press), detachment folding (Hardy and Finch, 2005), doubly vergent thrust wedges (Hardy et al., 2009), and the evolution of calderas (Hardy, 2008). In all these cases, the results bear a striking resemblance to fault deformation seen in the field and seismic.

2D and 3D implementations of the code exist, with convenient triaxial and angle of repose routines for the correct calibration of the particle assemblage. These programs allow spatial and temporal variations of rock properties and fault displacements, and the introduction of stress histories (e.g. overconsolidation), erosion, and syntectonic sedimentation. The influence of all these variables on fault zone structure will be tested in the project. Problematic details of the DEM are that fault zone width is a function of particle size, but in principle there is no lower limit on particle sizes or number of particles. The main limitation is run-times. This will not be a problem in the project since the code has been parallelized. For the simulations, we will use nine high-end 8 core MacPros running in parallel. This will allow us to run simulations with millions of particles. For a fault with 100-1000 m fault throw, particle sizes can be as small as 10-30 m, which is at the limit of seismic resolution and will be sufficient to capture the details of the fault zone.

The DEM allows a wealth of information (e.g. stress and strain) to be extracted in both space and time, such that the evolution of faulting is easily tracked. Figure 6 shows a 3D simulation of normal faulting using the proposed code. Map view (Figure 6a) and vertical slices along the fault slip direction (Figure 6b) are shown. Figure 6 illustrates a strategy to transfer the information from the geomechanical model to the seismic model. Particles displacements can be used to compute strain in a regular grid (Cardozo and Allmendinger, 2009). The 3D distribution of strain can then be used to condition the change of acoustic impedance in the seismic model.

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Figure 6. a. Horizontal, and b. vertical slices parallel to fault slip, of a 3D DEM simulation of normal faulting. Colours are incremental shear strain. Strain was computed in a grid using a grid-nearest-neighbour routine (Cardozo and Allmendinger, 2009). White dashed lines in horizontal slices show location of vertical slices below, and vice versa. Notice how active faulting varies along strike and in the vertical.#'2.2.2.'Seismic'modelling/imaging'of'geomechanical'models' Faults are difficult to image in seismic. Faults may not be associated with high impedance contrasts, but rather with weak diffractions that decay more rapidly in amplitude and frequency with increasing travel time than the normally reflected wave front (Townsend et al., 1998). One of the questions we want to answer in the project is: What is the impact of fault zone internal structure on the resulting seismic image? To answer this question, we need to use a model that correctly reproduces the wave scattering effects of the fault zone.The best method is a full-wave approach such as finite difference (FD) modelling (e.g. Virieux, 1986). However, this method is very costly, particularly in 3D and in elastic mode. In addition, the modelling grid is often coarse due to memory/time limitations, which restricts the value of the highest frequency. Although FD still needs to be used for benchmarking, more efficient approaches are available. One approach is to use hybrid modelling, which limits the use of FD to the targeted zones (e.g. HybriSeis technology; Lecomte et al., 2004). This method combines ray-tracing (RT) technology and FD. In the HybriSeis method, the computation gain is potentially high. However, this method - like FD modelling - produces synthetic data that need to be processed. The cost of modelling and processing may therefore still be too high. We propose the use of a more efficient approach that makes use of RT technology, but in a different manner. The method is called SimPLI (Simulated Prestack Local Imaging; Lecomte, 2008). SimPLI is a Prestack Depth Migration (PSDM) simulator using ray-based generated point-spread functions (PSFs) which are the image response of point scatterers. The technique can be thought as the 3D spatial convolution of a reflectivity cube with 3D PSFs (Lecomte, 2008). 3D PSDM cubes are thus generated without simulating synthetic recordings and processing them as in the FD and HybriSeis methods. Such simulation resembles the industry standard 1D convolution or trace-modelling approach. However, as opposed to1D convolution, SimPLI handles properly 3D effects in resolution (lateral reflector continuity) and illumination (survey geometry). Figure 7 shows a SimPLI simulation of a planar fault. From so-called ray-based illumination vectors, PSDM filters are generated, and from these, PSFs for, e.g., 0-km and 4-km offset acquisition. Notice that the resultant seismic image is different in terms of resolution and illumination. Both images, however, give a good idea of

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lateral resolution and position of the fault. More complexity can be expected if the detail of the fault zone is introduced in the input model.

Figure 7. SimPLI model of a simple, planar fault. From illumination vectors, PSFs and simulated PSDM are generated for 0-km and 4-km offset selections. Differences in resolution and illumination are function of offset (no illumination of the fault at 4-km offset). SimPLI is part of NORSAR’s SeisRoX modelling software. SeisRoX allows import/generation of reflectivity cubes at different resolutions, as well as volumes with 3D property distributions (geological and reservoir parameters) from which to condition reflectivity/scattering (rock physics). SimPLI is fast and therefore allows the user to perform sensitivity studies such as the effect of survey geometry, reservoir parameters, fault zone structure and frequency content on the resultant seismic image. Taking into account the described methods, we propose the following lines of research: • Adaption of SeisRoX rock physics technology to derive from the strain of the

geomechanical models, acoustic impedance and reflectivity/scattering for the seismic models. The functional relationship between finite strain and acoustic impedance is not known, so we will have to consider several possibilities (see Couples et al., 2007; their Figure 4).

• Seismic modelling of geomechanical fault zone analogues with comparisons between the FD/HybriSeis and SimPLI methods. This will help to identify the advantage and drawbacks of the SimPLI method, as well as define improvements.

• With benchmarked FD/HybriSeis models, ray-based imaging prototypes (Lecomte et al., 2005), will be applied to produce reference seismic cubes. In addition, the seismic imaging technology will be reviewed to better account for potentially complex wave-scattering effects in the fault zone. Novel techniques in seismic imaging (e.g. Landa, 2007) allow dealing with the diffracted energy in a separate manner, avoiding the dominating reflections. Re-thinking seismic imaging in a “side-scan” manner may help to catch more scattered energy.

• If the SimPLI-simulated 3D PSDM cubes proved to be valid at fault zones, the corresponding synthetic recordings can be obtained by applying modelling by demigration (Kaschwich and Lecomte, 2010). The obtained seismograms will include diffractions, contrary to standard RT (Kaschwich et al., 2010).

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2.2.3.'Feasibility'study'on'real'3D'seismic'data' Although the focus of the project is on mechanical and seismic modelling, we will pursue a feasibility study on real 3D seismic data. We will choose a reservoir with good 3D seismic and well data, and presence of large faults. Many fields in the North Sea fit this requirement, as for example the Troll field. Tools such as Landmark, Geoprobe, GeoTeric, TrapTester, RMS and Petrel can be tested. The aim is to see if we can use seismic attributes to (1) Map fault zone envelopes, and (2) Map fault zone internal structure. Principles from the modelling part will be critical for this evaluation. 2.3.'The'project'plan,'project'management,'organisation'and'cooperation''2.3.1'Project'organisation'and'management' The team is composed of experts in structural geology, geomechanical modelling, seismic modelling/imaging and interpretation. The project is envisaged as cooperation between three institutions and its success relies on integrated multidisciplinary work. The University of Stavanger (UiS) will coordinate the project. One scientist at this institution will act as project leader. The scientists involved in the project and their roles are included below: Dr. Nestor Cardozo UiS Project leader/coordinator

Geomechanical modelling Dr. Alejandro Escalona UiS Seismic interpretation Dr. Isabelle Lecomte NORSAR Seismic modelling/imaging Dr. Stuart Hardy ICREA/GGAC Geomechanical modelling One PhD, Charlotte Botter (MSc Nancy, France), joined the project in January 2012. Charlotte is located at UiS, although she travels frequently to Barcelona and Oslo to work with Dr. Hardy and Dr. Lecomte. 2.3.2'International'cooperation' Agreements for academic cooperation on this project have been established with ICREA (Institució Catalana de Recerca i Estudis Avançats), and GGAC, Facultat de Geologia, Universitat de Barcelona, Catalonia, Spain. 2.3.3'Progress'plan'H'milestones' The project started in January 2012 and it will run for three years. Charlotte Botter from ENSG, Geology school in Nancy, France, has been appointed as a Ph.D. in the project. Below is a project chronogram:

TASK 2012 2013 2014 Geomechanical modelling Implementation of model prototypes and techniques to transfer results to seismic model

x x x x

Fine tuning of models x x x x Evaluation of tectonic/stress regime, rock properties, and BCs on faulting

x x x x x x x x

Seismic modelling Import of mechanical models and change of acoustic impedance from strain

x x x x

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Implementation of model prototypes x x x x Fine tuning of models x x x x Impact of fault zone structure and acquisition parameters on seismic image. Establishment of control parameters for seismic interpretation

x x x x x x x x

Feasibility study on real 3D seismic Seismic interpretation and analysis of fault zones

x x x x

2.4. Costs incurred by each research partner

All quantities are in KNOK UiS ICREA/GGAC NORSAR Personnel 900 PhD 2553 Equipment 100 Administration and indirect costs 200 100 100 Direct costs, travel 200 100 100 Sum 2953 300 1100

The total cost of the project is 4.353 MNOK. PhD costs are 851 KNOK per year

(Research Council of Norway). Direct costs include travelling, conferences, as well as publication costs. 2.5.'Financial'contribution'by'partners' The Norwegian Research Council (NFR, Petromaks program) has awarded us funding for 70% of the project costs. This funding covers Ph.D. costs and some of the personnel and indirect costs above. We are looking for an industry partner to cover the remaining 30% of the costs. Industry funding will cover mainly personnel costs at NORSAR, which are essential to develop the seismic imaging part of the project. Details of the costs incurred by each research partner, and of the financial contribution by partners are given in the following table.

Contributors Annual amount (KNOK) Total amount (KNOK) Norwegian Research Council 1015.7 3047.1 Industry partner 435.3 1305.9 Sum 1451 4353

3.##Key#perspectives#and#compliance#with#strategic#documents##3.1.'Compliance'with'strategic'documents''

For the University of Stavanger (UiS), the project is a unique opportunity to build a special competence in the area of reservoir characterization, which will be beneficial to support ongoing research (e.g. EOR, mechanical and chemical reservoir behaviour, drilling optimization), as well as to establish new academic and industry collaborations.

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3.2.'Relevance'and'benefit'to'society'' The project can contribute to improved description and characterization of faulted reservoirs, which allow more precise forecasting of subsurface reservoir behaviour. In practical terms this translates to improved risk assessment, more efficient and safer: (i) Well planning and drilling of reservoirs targeted for production and/or injection, (ii) CO2 sequestration, and (iii) Enhanced geothermal systems. 3.3.'Environmental'impact'' No direct environmental impact is foreseen from the project work. In the long term, project results may contribute towards improved risk assessment of CO2 leakage through faults, drilling induced environmental damage, and induced seismicity associated with drilling or enhanced geothermal systems. 3.4.'Ethical'perspectives'' Project results and their exploitation thereof are not expected to raise ethical questions. 3.5.'Gender'issues'(Recruitment'of'women,'gender'balance'and'gender'perspectives)'''

We will give preference to female applicants for the PhD/Postdoc position, if equally qualified.'

4.'Dissemination'and'communication'of'results'''

4.1'Dissemination'plan''Publication of project results will take place throughout the project period and beyond.

We envisage a minimum of 5 peer-reviewed papers in international journals. Project results will also be presented at international and national conferences. The cross-disciplinary nature of the project facilitates dissemination of results through a broad range of specialist forums.

We have presented a proof or our methodology in 2D at the 2012, EAGE Fault and

Top Seals conference in Montpellier (Botter et al., 2012). An extended abstract of this work is included. '4.2'Communication'with'users''' Annual, progress update meetings will be hold with the industry partner. References'

Botter, C., Cardozo, N., Hardy, S., Lecomter, I. and Escalona, A. 2012. Seimic imaging of Fault Zones. EAGE Fault and Top Seals conference, Montpellier, France.

Cardozo, N. and Allmendinger, R.W. 2009. SSPX: A program to compute strain from displacement/velocity data. Computers and Geosciences 35, 1343-1357.

Childs, C., Watterson, J. and Walsh, J.J. 1996. A model for the structure and development of fault zones. Journal of the Geological Society of London 153, 337-340.

Childs, C., Manzocchi, T., Walsh, J.J., Bonson, C.G., Nicol, A. and Schӧpfer, M. 2009. A geometric model of fault zone and fault rock thickness variations. Journal of Structural Geology 31, 117-127.

Couples, G., Ma, J., Lewis, H., Olden, P., Quijano, J., Fasae, T. and Maguire, R. 2007. Geomechanics of faults: impacts on seismic imaging. First Break 25, 83-90.

do Nascimento, A.F., Cowie, P.A., Lunn, R.J. and Pearce, R.G. 2004. Spatio-temporal evolution of induced seismicity at Açu reservoir, NE Brazil. Geophys. J. Int. 158, 1041-1052.

Dockrill, B. and Shipton, Z.K. 2010. Structural controls on leakage from a natural CO2 geologic storage site: Central Utah, USA. Journal of Structural Geology 32, 1768-1782.

Dutzer, J.F., Basfor, H. and Purves, S. 2009. Investigating fault sealing potential through fault relative seismic volume analysis. Petroleum Geology Conference. The Geological Society, London 2009.

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Fachri, M., Tveranger, J., Cardozo, N., Pettersen, Ø., Espedal, M. In press. The impact of fault envelope structure on fluid flow. American Association of Petroleum Geologists Bulletin.

Finch, E., Hardy, S. and Gawthorpe, R. 2003. Discrete element modeling of contractional fault-propagation folding above rigid basement fault blocks. Journal of Structural Geology 25, 515-528.

Finch, E., Hardy, S. and Gawthorpe, R. 2004. Discrete element modeling of extensional fault-propagation folding above rigid basement fault blocks. Basin Research 16, 467-488.

Fredman, N., Tveranger, J., Cardozo, N., Braathen, A., Soleng, H., Røe, P., Skorstad, A. and Syversveen, A.R. 2008. Fault facies modeling: Technique, and approach for 3D conditioning and modeling of faulted grids. American Association of Petroleum Geologists Bulletin 92, 1457-1478.

Færseth, R.B., Johnsen, E. and Sperrevik, S. 2007. Methodology for risking fault seal capacity: Implications of fault zone architecture. American Association of Petroleum Geologists Bulletin 91, 1231-1246.

Hardy, S. and Finch, E. 2005. Discrete-element modeling of detachment folding. Basin Research 17, 507-520. Hardy, S. and Finch, E. 2006. Discrete element modeling of the influence of cover strength on basement-involved

fault-propagation folding. Tectonophysics 415, 225-238. Hardy, S. and Finch, E. 2007. Mechanical stratigraphy and the transition from trishear to kink-band fault-

propagation fold forms above blind basement thrust faults: A discrete-element study. Marine and Petroleum Geology 24, 75-90.

Hardy, S. 2008. Structural evolution of calderas: Insights from two-dimensional discrete element simulations. Geology 36, 927-930.

Hardy, S., McClay, K. and Anton Muñoz J. 2009. Deformation and fault activity in space and time in high-resolution numerical models of doubly vergent thrust wedges. Marine and Petroleum Geology 26, 232-248.

Hardy, S. In press. Cover deformation above steep, basement normal faults: Insights from 2D discrete element modeling. Marine and Petroleum Geosciences.

Kaschwich, T. and Lecomte, I., 2010, Improved ray-based seismograms by combining modeling by demigration with a prestack depth migration simulator, Expanded Abstracts, EAGE Annual Meeting, Barcelona.

Kaschwich, T., Gjøystdal, H., Lecomte, I. and Iversen, E., 2010, Reflection, Diffraction and Resolution. 14th Annual Report of the Wave Inversion Technology (WIT) consortium, pages 153–163.

Knipe, R.J., Jones, G. and Fisher, Q.J. 1998. Faulting, fault seal and fluid flow in hydrocarbon reservoirs: an introduction. In: Jones, G., Knipe, R.J. and Fisher, Q.J. (Eds) Faulting, Fault Sealing and Fluid Flow in Hydrocarbon Reservoirs. Geological Society of London, Special Publications 147, vii-xxi.

Landa, E., 2007. Beyond Conventional Seismic Imaging. Education Tour Series CIS, EAGE Publications. Lecomte, I., Gjøystdal, H., Drottning, Å., Maaø, F.A., Johansen, T.A. and Bakke, R. 2004. Efficient and flexible

seismic modeling of reservoirs: A hybrid approach. The Leading Edge 23, 432-437. Lecomte, I., Hamran, S.E. and Gelius, L.J. 2005. Improving Kirchhoff migration with repeated Local Plane-Wave

imaging? A SAR-inspired signal-processing approach in prestack depth imaging. Geophysical Prospecting 53, 767-785. Lecomte, I. 2008. Resolution and illumination analyses in PSDM: A ray-based approach. The Leading Edge 27,

650-663. Long, J.J. and Imber, J. 2010. Geometrical coherent continuous deformation in the volume surrounding a

seismically imaged normal fault-array. Journal of Structural Geology 32, 222-234. Majer, E.L., Baria, R., Stark, M., Oates, S., Bommer, J., Smith, B. and Asanuma, H. 2007. Induced seismicity

associated with enhanced geothermal systems. Geothermics 36, 185-222. Manzocchi, T., Heath, A.E., Palananthakumar, B., Childs, C. and Walsh, J.J. 2008. Faults in conventional flow

simulation models: a consideration of representational assumptions and geological uncertainties. Petroleum Geoscience 14, 91-110.

Manzocchi, T., Childs, C. and Walsh, J.J. 2010. Faults and fault properties in hydrocarbon flow models. Geofluids 10, 94-113.

Nelson, S.T., Mayo, A.L., Gilfillan, S., Dutson, S.J., Harris, R.A., Shipton, Z.K. and Tingey, D.G. 2009. Enhanced fracture permeability and accompanying fluid flow in the footwall of a normal fault: The Hurricane fault at Pah Tempe hot springs, Washington County, Utah. Geological Society of America Bulletin 121, 236-246.

Nicolaisen, E. M. 2009. Seismic characterization of fault zones for use in fault facies reservoir models. Master thesis. University of Stavanger, Norway.

Soleng, H., Syversveen, A.R., Skorstad, A. and Tveranger, J. 2007. Flow through inhomogeneous fault zones. Society of Petroleum Engineers 110331.

Sorkhabi, R. and Tsuji, Y. 2005. The place of faults in petroleum traps. In: Sorkhabi, R. and Tsuji, Y. (Eds) Faults, Fluid Flow, & Petroleum Traps. American Association of Petroleum Geologists Memoir 85, 1-31.

Stewart, S.A. and Holt, J. 2004. Improved drilling performance through integration of seismic, geological and drilling data. In: Daview, R.J., Cartwright, J.A., Stewart, S.A., Lappin, M. and Underhill, J.R. (Eds) 3D Seismic Technology: Application to the Exploration of Sedimentary Basins. Geological Society of London, Memoirs 29, 303-310.

Townsend, C., Firth, I.R., Westerman, R., Kirkevollen, L., Harde, M. and Andersen, T. 1998. Small seismic-scale fault identification and mapping. In: Jones, G., Fisher, Q.J. and Knipe, R.J. (Eds) Faulting, Fault Sealing and Fluid Flow in Hydrocarbon Reservoirs. Geological Society of London, Special Publications 147, 1-25.

Tveranger, J., Cardozo, N., Kjeldaas, G.C., Nøttveit, H. and Røe, P. 2008: Volumetric fault zone modelling using fault facies. Fault zones: structure geomechanics and fluid flow conference. The Geological Society, London 2008.

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Virieux, J. 1986. P-SV wave propagation in heterogeneous media: velocity-stress finite-difference method. Geophysics 51, 889-901.

Wibberley, C.A.J., Yielding, G. and Di Toro, G. 2008. Recent advances in the understanding of fault zone internal structure: a review. In: Wibberley, C.A.J., Kurz, W., Imber, J., Holdsworth, R.E. and Collettini, C. (Eds) The Internal Structure of Fault Zones. Geological Society of London, Special Publications 299, 5-33.