Development of a numerical workflow based on μ-CT imaging for the determination of capillary pressure-saturation-specific interfacial area relationship in 2-phase flow pore-scale porous-media systems: A case study on Heletz sandstone

In this case study, we present the implementation of a finite element method (FEM)-based numerical pore-scale model that is able to track and quantify the propagating fluid–fluid interfacial area on highly complex micro-computed tomography (μ-CT)-obtained geometries. Special focus is drawn to the relationship between reservoir-specific capillary pressure (pc), wetting phase saturation (Sw) and interfacial area (awn). The basis of this approach is high-resolution μ-CT images representing the geometrical characteristics of a georeservoir sample. The successfully validated 2-phase flow model is based on the Navier–Stokes equations, including the surface tension force, in order to consider capillary effects for the computation of flow and the phase-field method for the emulation of a sharp fluid–fluid interface. In combination with specialized software packages, a complex high-resolution modelling domain can be obtained. A numerical workflow based on representative elementary volume (REV)-scale pore-size distributions is introduced. This workflow aims at the successive modification of model and model set-up for simulating, such as a type of 2-phase problem on asymmetric μ-CT-based model domains. The geometrical complexity is gradually increased, starting from idealized pore geometries until complex μ-CT-based pore network domains, whereas all domains represent geostatistics of the REV-scale core sample pore-size distribution. Finally, the model can be applied to a complex μ-CT-based model domain and the pc–Sw–awn relationship can be computed

Modelling of CO2 storage in geological formations with DuMux, a free-open-source numerical framework. A possible tool to assess geological storage of carbon dioxide in Romania

Geological storage of carbon dioxide represents a viable solution to reduce the greenhouse gases in the atmosphere. Romania has initiatives to build a large-scale integrated CO2 capture and storage demonstration project and find suitable on-shore and off-shore CO2 storage locations. Numerical simulators are essential tools helping the design process. These simulators are required to be capable to represent the complex thermo-hydro-mechanical-chemical and biological phenomena accompanying the geological CO2 storage such as, multi-phase flow, compositional effects due to dissolution of CO2 into the brine, non-isothermal effects due to cold CO2 injection, geomechanical effects, mineralization at the reservoir-scale. These processes can be simulated accurately and efficiently with DuMux (www.dumux.org), a free- and open-source simulator. This article presents and reviews briefly these mathematical and numerical models

Modelling of kinetic interface sensitive tracers reactive transport in 2D two-phase flow heterogeneous porous media

Fluid-fluid interfacial area plays an important role for mass- and energy-transfer processes across the interface which is relevant in several hydrogeological and engineering applications, e.g. enhanced oil-gas recovery, CO2 storage in geological formations, unconventional geothermal systems, contaminant removal, etc. Kinetic interface sensitive tracers were designed to determine the size of the interface between two fluids by undergoing hydrolysis at the fluid-fluid interface. This study investigates by means of numerical modelling the influence of heterogeneity on the KIS tracer breakthrough curves in six idealized scenarios (S1-S6). It is an extension of the previous work conducted in “one-dimensional” column experiments by Tatomir et al. (2018) [1]. The changes in interfacial area are created by inclusion of heterogeneities at the Darcy-scale. The results show that KIS tracers can be used in two-dimensional experimental setup and can provide information about the size and dynamic evolution of interfacial area. Therefore, this is a first step for the dimensioning of an experimental flume

Conceptual model development using a generic Features, Events, and Processes (FEP) database for assessing the potential impact of hydraulic fracturing on groundwater aquifers

<p>Hydraulic fracturing for natural gas extraction from unconventional reservoirs has not only impacted the global energy landscape but has also raised concerns over its potential environmental impacts. The concept of <q>features, events and processes</q> (FEP) refers to identifying and selecting the most relevant factors for safety assessment studies. In the context of hydraulic fracturing we constructed a comprehensive FEP database and applied it to six key focused scenarios defined under the scope of FracRisk project (<a href="http://www.fracrisk.eu" target="_blank">http://www.fracrisk.eu</a>, last access: 17 August 2018). The FEP database is ranked to show the relevance of each item in the FEP list per scenario. The main goal of the work is to illustrate the FEP database applicability to develop a conceptual model for regional-scale stray gas migration.</p

Capturing the state-of-knowledge in EURAD knowledge management

Knowledge about a wide variety of aspects is fundamental for the safe management and disposal of radioactive waste. This importance of Knowledge Management (KM) is also recognised by EURAD, the European Joint Programme on Radioactive Waste Management (RWM), which brings together over 100 organisations from different countries and backgrounds (Waste Management Organisations, Technical Support Organisations, and Research Entities). This vast resource of expertise and experience feeds into several dedicated EURAD KM programme activities. One of these activities, led by Work Package 11 State-of-Knowledge (WP11 SoK), is capturing experts’ views on the current State-of-Knowledge on topics relevant to RWM and making this knowledge accessible through dedicated documents. For this, EURAD has developed the “Goals Breakdown Structure” (GBS), which provides a framework in which topics are structured thematically, as well as a hierarchy of documents that allows accessing knowledge on different levels of detail (see EURAD Roadmap). To make this knowledge available, EURAD is currently developing a Wiki (i.e., a web-based resource that allows access to knowledge and collaborative interactions) and is drafting a sustainable Knowledge Management System and other supportive KM-IT tools while already feeding the tools with content. This article gives an insight into the general EURAD KM concept, the approaches used, and the results obtained until EURAD’s mid-term, after 2.5 years

Heletz experimental site overview, characterization and data analysis for CO2 injection and geological storage

International audienceThis paper provides an overview of the site characterization work at the Heletz site, in preparation to scientifically motivated CO2 injection experiments. The outcomes are geological and hydrogeological models with associated medium properties and baseline conditions. The work has consisted on first re-analyzing the existing data base from ∼40 wells from the previous oil exploration studies, based on which a 3-dimensional structural model was constructed along with first estimates of the properties. The CO2 injection site is located on the saline edges of the Heletz depleted oil field. Two new deep (>1600 m) wells were drilled within the injection site and from these wells a detailed characterization program was carried out, including coring, core analyses, fluid sampling, geophysical logging, seismic survey, in situ hydraulic testing and measurement of the baseline pressure and temperature. The results are presented and discussed in terms of characteristics of the reservoir and cap-rock, the mineralogy, water composition and other baseline conditions, porosity, permeability, capillary pressure and relative permeability. Special emphasis is given to petrophysical properties of the reservoir and the seal, such as comparing the estimates determined by different methods, looking at their geostatistical distributions as well as changes in them when exposed to CO2

Von diskreten zu kontinuumsbildenden Strömungskonzepten in geklüfteten porösen Medien

As more and more engineering applications require the correct simulation of flow and transport processes in porous media, and while many of these media present a certain degree of fracturing, this work deals with the development of numerical models that can simulate two-phase flow in large-scale fractured reservoirs. Among the applications which these models are addressing to, there are the estimation of contaminant spreading and removal, the reservoir exploitation, or more recently the CO2 sequestration, the geothermal reservoir exploitation, and the nuclear waste repositories. Fractured systems are ubiquitous around the world and can occur on avariety of lengths and scales which makes difficult the development of a general model that can handle easily all of them. The overall purpose of this work is to improve the understanding over the concepts of the multiphase flow and processes in the fractured porous media and develop a conceptual model that allows the study of two-phase flow in fractures of arbitrary size, orientation and shape. The flow models have been roughly classified in discrete fracturemodels (DFM), continuum fracturemodels (CFM) and hybrid. The DFMs consider the fractures explicitly and thereforerequirehuge computation power,whereas CFMs require the determination of arepresentative elementary volume (REV), the appropriate effective parameters and transfer functions between continua. For alarge scale problem, like aCO2 storage reservoir,there can be millions of fractures which might have to be considered and could be a formidable task for a DFM simulator.In this sense a continuum model, which is in this case in the form of a generalized dual-porosity representation, does not require the fine discretization of a DFM and the detailed fracturecharacterization during simulations. Thus, another goal of this work is to build areliable large scale multiphase flow simulator based on the continuum approach. Two flow simulators, 2pDFM and 2pMINC,have been developed and tested based on the two different fracture model concepts. Both simulators are implemented in the numerical toolbox DuMux.The 2pDFM model simulates the two-phase flow in fractured porous media using aDFM approach, with a lower dimensional representation for the fracture network (DFM-L). The model is capable to account for storage in the fractures. The 2pMINC model simulates two-phase flow in fractured porous media using the multiple interacting continua (MINC) method with an improved upscaling technique. The complex transient behavior of the flow processes in fractured porous media is captured by subgridding the coarse blocks in nested volume elements which have effective properties calculated from the detailed representation of the fracturesystem. In this way,the physically based approach is kept, the accuracy of the model is preserved ,the common use of empirically derived transfer functions is avoided and the complexity of the problem is considerably reduced which is reflected in the speedup factors up to 1000. This research extends the applicability range of the upscaling procedure to include entry pressure effects. Moreover,a general workflow has been developed for the numerical simulation of the two-phase flow in large-scale fractured porous media. The results are verified, validated and tested in a fully comprehensive way for both models. To test the behaviour of the simulator for field scale problems they are applied to an idealized medium with periodic fracture pattern and to areal, naturally fractured reservoir from the Bristol Channel. The evaluation shows that the extended MINC model is able to reproduce both, the large-scale permeability and the dynamics of the fracture-matrix mass transfer,correctly. The extended MINC method and the simulation procedure is flexible as it allows choosing the accuracy of the solution, the computation speed, and allows working with spatial information about the fracture system of various complexity and detail.Kluftsysteme sind auf dieser Welt allgegenwärtig und werden seit mehr als 60 Jahren in unterschiedlichen Bereichen, wie der Hydrologie, der Erdölförderung oder der geothermalen Energie untersucht. Für eine Vielzahl von Anwendungsbereichen sind prädiktive Simulationen der Mehr-phasenströmung und des Transports in geklüfteten porösen Medien von großem Interesse, z.B. bei der Erschließung von Wasserspeichern zur Wasserversorgung, bei der Sanierung wasserführender Schichten (Aquifere) (Berkowitz [2002],Niessner et al.[2005]), bei der Erschließung von Erdölspeichern (Lemonnier and Bourbiaux [2010], Kazemi [1976]), bei der Erschließung geothermaler Speicher,der Wärmespeicherung, bei Prozessen in Bergbau und Mineralisierung (lokale Extraktion und Bestimmung von Erzvorkommen), bei der CO2 Speicherung in geologischen Schichten (Carneiro [2009], Kopp [2009]), bei der Atommülllagerung (Bodvarsson et al. [1999], Reichenberger et al. [2003]) usw.. All diese Anwendungen können mittels Gestaltung und Überwachung durch Computermodelle besser verstanden werden. Rechnergestützte Modellierung ist der Prozess der Entwicklung mathematischer Repräsentationen einer echten oder hypothetischen Situation, um diese besser zu untersuchen, und um einen Einblick in die Funktionsweise und Handhabung dieser Systeme zu erhalten. Im Falle der Endlagerung radioaktiven Mülls müssen die unterirdischen Anlagen eine Sicherheitsgarantie von hunderten oder gar tausenden von Jahren bieten. Daher liegt der Schlüssel zum Verständnis mehrphasiger Prozesse und zur Vorhersage über das Verhalten des Reservoirs in der Erstellung eines genauen Modells. Einige der größten Herausforderungen bei der Erstellung von Mehrphasen-Strömungsmodellen in geklüfteten porösen Medien stellen die großen Unterschiede der Klufteigenschaften und der Eigenschaften des umgebenden Gesteins, sowie die unterschiedlichen Zeitmaßstäbe der Strömungsprozesse dar. In dieser Arbeit werden mathematische Modelle und numerische Simulationswerkzeuge für geklüftete poröse Medien entwickelt, die eine wichtige Rolle bei der Untersuchung unterirdischer Reservoirs, bei der Gestaltung und Untersuchung von Feldversuchen und bei der Verbesserung und Optimierung der Handhabung geologischer Reservoirespielen

Modeling of methane migration from gas wellbores into shallow groundwater at basin scale

Methane contamination of drinking water resources is one of the major concerns associated with unconventional gas development. This study assesses the potential contamination of shallow groundwater via methane migration from a leaky natural gas well through overburden rocks, following hydraulic fracturing. A two-dimensional, two-phase, two-component numerical model is employed to simulate methane and brine upward migration toward shallow groundwater in a generic sedimentary basin. A sensitivity analysis is conducted to examine the influence of methane solubility, capillary pressure–saturation relationship parameters and residual water saturation of overburden rocks, gas leakage rate from the well, tilted formations, and low-permeability sediments (i.e., claystones) on the transport of fluids. Results show that the presence of lithological barriers is the most important factor controlling the temporal–spatial distribution of methane in the subsurface and the arrival time to shallow groundwater. A pulse of high leakage rate is required for early manifestation of methane in groundwater wells. Simulations reveal that the presence of tilted features could further explain fast-growing methane contamination and extensive lateral spreading reported in field studies.Horizon 2020 http://dx.doi.org/10.13039/501100007601Georg-August-Universität Göttingen (1018

Modelling of CO

Geological storage of carbon dioxide represents a viable solution to reduce the greenhouse gases in the atmosphere. Romania has initiatives to build a large-scale integrated CO2 capture and storage demonstration project and find suitable on-shore and off-shore CO2 storage locations. Numerical simulators are essential tools helping the design process. These simulators are required to be capable to represent the complex thermo-hydro-mechanical-chemical and biological phenomena accompanying the geological CO2 storage such as, multi-phase flow, compositional effects due to dissolution of CO2 into the brine, non-isothermal effects due to cold CO2 injection, geomechanical effects, mineralization at the reservoir-scale. These processes can be simulated accurately and efficiently with DuMux (www.dumux.org), a free- and open-source simulator. This article presents and reviews briefly these mathematical and numerical models