Anita Torabi

University of Oslo

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Behzad Alaei

University of Oslo

Haakon Fossen

University of Bergen

Elin Skurtveit

Norwegian Geotechnical Institute

Alvar Braathen

University of Oslo

R. Alikarami

Uni Research (Norway)

Dmitriy Kolyukhin

Institute of Petroleum Geology and Geophysics

Francisco C.C. Nogueira

Universidade Federal de Campina Grande

David L. Vasconcelos

Universidade Federal de Campina Grande

Eivind Bastesen

NORCE Norwegian Research Centre

Francisco H.R. Bezerra

Universidade Federal do Delta do Parnaíba

Cooperative Institutions

University of Oslo

University of Bergen

Uni Research (Norway)

Centre National de la Recherche Scientifique

NORCE Norwegian Research Centre

Sols, Solides, Structures, Risques

Laboratoire des Écoulements Géophysiques et Industriels

Universidade Federal do Rio Grande do Norte

University of Bari Aldo Moro

Institute of Geosciences and Earth Resources

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Impact of Faults on the Mechanical and Petrophysical Properties of Sandstone Reservoirs - An Implication for CO2 Storage

Proceedings (2012)

R. Alikarami Anita Torabi Elin Skurtveit

To assess reliable candidate reservoirs/aquifers for CO2 storage, enhanced understanding of the structure and the mechanical and petrophysical properties of strain localization zones in comparison to the surrounding undeformed rock is essential (Torabi 2007). To understand the possible effect of deformation structures on CO2 storage, a fieldwork was performed in the Navajo and Entrada sandstones in southeastern Utah to investigate the elastic and petrophysical properties of a fault core and damage zone. Deformation structures, air permeability and rock hardness have been logged along scan-lines perpendicular to the fault. In the foot-wall fractures are observed just within distance of three meters from the fault, but deformation bands are spread to about hundreds of meters. In the hangingwall fractures are observed in a distance of more than seventy meters, while deformation band have been concentrated within forty meters from the fault. Our preliminary results show a strong correlation between deformation structures intensity and distance from the fault, but weak correlation between Schmidt Hammer rebound and mini-perm values versus deformation pattern. The spread in the measured data might be related to variation in internal layering in the sand dunes, the orientation and weathering of the surface used for testing or other structural effects.

Petrophysics

Deformation bands

Layering

10.3997/2214-4609.20143824

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Citations (0)

GeoFault: A well-founded fault ontology for interoperability in geological modeling

Computers & Geosciences (2023)

Yuanwei Qu Michel Perrin Anita Torabi Mara Abel Martin A. Giese

Geological modeling currently uses various computer-based applications. Data harmonization at the semantic level using ontologies is essential to make these applications interoperable. Since geo-modeling is part of several multidisciplinary projects, interoperability requires semantic harmonization to exchange information between geological applications and integrate other domain knowledge at a general level. Therefore, domain ontologies that describe geological knowledge must be based on a sound ontological background to ensure this knowledge is integrable. Faults are essential for understanding and solving structural problems but are complex to model because the concept of fault includes a group of geological entities with a distinct ontological nature. A fault can correspond to thin, deformed rock volumes or spatial arrangements resulting from the displacement of geological blocks, but at a broader scale, geologists describe faults as surfaces or components of complex fault arrays. Our work intends to harmonize these views by presenting a domain ontology, GeoFault, resting on the Basic Formal Ontology (BFO) and the GeoCore ontology. GeoCore and GeoFault support the parametric description of geological sites as a preliminary step for quantitative and qualitative analysis. We have proposed GeoFault after systematically revising the literature and several knowledge-acquisition sessions with expert structural geologists. The ontology formalizes a vocabulary for fault "sensu stricto," excluding ductile shear deformations. It covers the regional to outcrop scales, excluding structures at the microscopic, orogenic, and tectonics scales, and it avoids interpretive language associated with geological processes as far as possible. Extending the BFO and GeoCore ontologies allows the fault concept to be related to formal ontological classes in a consistent semantic-rich framework. The ontology artifact is implemented in OWL 2, validated by competency questions with two use cases, and tested using an in-house ontology-driven data entry application. The GeoFault ontology is publicly available and provides a solid framework for clarifying fault knowledge and a foundation for many applications.

10.1016/j.cageo.2023.105478

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Citations (7)

Normal fault geometric attribute variations with lithology: examples from the Norwegian Barents Sea

Geological Society London Special Publications (2019)

Audun Libak Anita Torabi Behzad Alaei

Abstract The geometry of faults exposed in the field is at least partly controlled by host-rock lithology. However, little work has been published on the effect of lithology on the geometry of very large faults imaged in seismic data. This paper presents such a study for seismic-scale faults in the Norwegian Barents Sea. Gamma-ray data are used to extract clay volumes of the host rock. These clay volume logs are used to populate 3D seismic cubes with lithology information. Finally, the clay volume cubes are co-rendered with seismic coherence cubes using opacity blending. This makes it possible to visualize both lithology information and fault geometries in the same volume. Intervals of different lithologies are studied in order to compare fault geometries. The results show some differences between claystone-rich intervals and the more sandstone-dominated intervals. The fault zone is more segmented and wider in the claystones, while the sandy intervals are narrower and more localized with less segmentation. Larger displacement faults penetrate into deeper stratigraphic levels than smaller displacement faults, and their basal tips are unrelated to lithological decoupling.

Lithology

Petrophysics

10.1144/sp495-2018-164

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Citations (4)

Deformation of Porous Sandstone and its Implication for CO2 Storage

Proceedings (2014)

Anita Torabi

The mechanics and mechanism of deformation in sandstone reservoirs and the influence of deformation structures (e.g. faults, deformation bands, fractures) on the characteristics and quality of such reservoirs are investigated. The study has a particular implication for reservoirs that are either candidates for or are already subjected to CO2 storage. The aim is to increase our understanding of the processes and products of faulting in porous sandstone in order to forecast the distribution and impact of faults and their associated deformation structures on reservoir performance and seal properties. For this to be achieved, an integrated and interdisciplinary research method using geological fieldworks, geomechanical experiments and numerical geomechanical models is employed.

Deformation mechanism

10.3997/2214-4609.20140113

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Fault Zone Development with Temporal Impact on Fluid Flow - Example from Navajo Sandstone, Utah

Proceedings (2014)

Elin Skurtveit Anita Torabi Alvar Braathen R. Alikarami

This work presents a field study of deformation structures found in a fault within the Navajo Sandstone in the San Rafael Swell, Utah. The main objective of this work is to describe the structural characteristics of the fault and identify different deformation episodes and their impact on fluid flow in the fault zone. Field analogues can be a useful tool for describing the hydo-mechanical coupling within fault zones and provides important knowledge of fault architecture and structural characteristics within faults. The studied faults are found to contain cataclastic deformation band later overprinted by fracturing and with calcite cement indicating fluid flow along the fault.

Cataclastic rock

Navajo

Extensional fault

Deformation bands

10.3997/2214-4609.20140091

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Review of Modeling Approaches to Groundwater Flow in Deformed Carbonate Aquifers

Ground Water (2020)

G. Medici Luca Smeraglia Anita Torabi Chartlotte Botter

We discuss techniques to represent groundwater flow in carbonate aquifers using the three existing modeling approaches: equivalent porous medium, conduit network, and discrete fracture network. Fractures in faulted stratigraphic successions are characterized by dominant sets of sub-vertical joints. Grid rotation is recommended using the equivalent porous medium to match higher hydraulic conductivity with the dominant orientation of the joints. Modeling carbonate faults with throws greater than approximately 100 m is more challenging. Such faults are characterized by combined conduit-barrier behavior. The barrier behavior can be modeled using the Horizontal Flow Barrier Package with a low-permeability vertical barrier inserted to represent the impediment of horizontal flow in faults characterized by sharp drops of the piezometric surface. Cavities can occur parallel to the strike of normal faults generating channels for the groundwater. In this case, flow models need to account for turbulence using a conduit network approach. Channels need to be embedded in an equivalent porous medium due to cavities a few centimeters large, which are present in carbonate aquifers even in areas characterized by low hydraulic gradients. Discrete fracture network modeling enables representation of individual rock discontinuities in three dimensions. This approach is used in non-heavily karstified aquifers at industrial sites and was recently combined with the equivalent porous medium to simulate diffusivity in the matrix. Following this review, we recommend that the future research combines three practiced modeling approaches: equivalent porous medium, discrete fracture network, and conduit network, in order to capture structural and flow aspects in the modeling of groundwater in carbonate rocks.

Electrical conduit

Classification of discontinuities

Network model

Groundwater model

Aquifer test

10.1111/gwat.13069

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Citations (60)

Evaluating Economic and Human Impacts of Varying Earthquake Scenarios Through Multi-Method Analysis: An Example for Oslo, Norway

Federica Ghione Sergio Molina Anita Torabi Volker Øye

10.2139/ssrn.4979331

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Fault geometric and seismic attributes – an integrated study with focus on the Barents Sea

First Break (2016)

Anita Torabi Behzad Alaei Dmitriy Kolyukhin R.H. Libak R. H. Gabrielsen

A full fault analysis assessing the influences of faults on (hydrocarbon) prospects and fluid communication includes analysis of the fault geometry, the fault architecture and segment linkage, assessment of petrophysical properties as well as establishment of the time-related geological development. It is also crucial to realize that faults are three-dimensional rock bodies, rather than surfaces (Chester and Logan, 1986; Caine et al., 1996; Gabrielsen and Braathen, 2014; Gabrielsen et al., 2016a). Basic data for such study are commonly derived from seismic interpretation and drilling, although studies that combine dedicated fault imaging (Lindanger et al., 2004; Botter et al., 2014) and field data (e.g. Walsh and Watterson, 1991; Childs et al., 2009; Davatzes and Aydin, 2005; Bastesen et al., 2013; Gabrielsen et al., 2016a) has lately become feasible. It is therefore necessary to enhance the tools and capacity for utilizing reflection seismic data in fault analysis, particularly because inaccurate interpretation and mapping of faults could cause incorrect trap definition, leading to the drilling of dry wells and causing misinterpretation of influence of faults on fluid transport. Research efforts by the seismic community have focused much on the use of advanced algorithms (e.g. Chopra and Marfurt, 2007), but has to a lesser extent utilized results from outcrop studies of faults carried out by structural geologists.

Petrophysics

Outcrop

Fault block

10.3997/1365-2397.34.5.84453

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Citations (10)

Sequential growth of deformation bands in carbonate grainstones in the hangingwall of an active growth fault: Implications for deformation mechanisms in different tectonic regimes

EarthArXiv (California Digital Library) (2017)

Atle Rotevatn Elin Thorsheim Eivind Bastesen Heidi Fossmark Anita Torabi

Deformation bands in porous sandstones have been extensively studied for four decades, whereas comparatively less is known about deformation bands in porous carbonate rocks, particularly in extensional settings. Here, we investigate porous grainstones of the Globigerina Limestone Formation in Malta, which contain several types of deformation bands in the hangingwall of the Maghlaq Fault: (i) bed-parallel pure compaction bands (PCB); (ii) pressure solution-dominated compactive shear bands (SCSB) and iii) cataclasis-dominated compactive shear bands (CCSB). Geometric and kinematic analyses show that the bands formed sequentially in the hangingwall of the evolving Maghlaq growth fault. PCBs formed first due to fault-controlled subsidence and vertical loading; a (semi-)tectonic control on PCB formation is thus documented for the first time in an extensional setting. Pressure solution (dominatingSCSBs) and cataclasis (dominating CCSBs) appear to have operated separately, and not in concert. Our findings therefore suggest that, in some carbonate rocks, cataclasis within deformation bands may develop irrespective of whether pressure solution processes are involved.We suggest this may be related to stress state, and that whereas pressure solution is a significant facilitator of grain size reduction in contractional settings, grain size reduction within deformation bands in extensional settings is less dependent on pressure solution processes.

Cataclastic rock

Deformation bands

Pressure solution

Overburden pressure

10.31223/osf.io/8gsqw

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Citations (1)

Heterogeneity Within Deformation Bands In Sandstone Reservoirs

46th U.S. Rock Mechanics/Geomechanics Symposium (2012)

Anita Torabi R. Alikarami

Deformation bands

Source

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Citations (10)