Stuart Duncan Christopher Walsh

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Verified

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• PhD Applied Mathematics
• Professor (Associate) at Monash University (Australia)

The global energy transition will drive increased demand for a broad range of mined minerals.40 Australia is well positioned to support the global energy transition, given its mature mining sector41 and rich and diverse mineral resources. The potential growth in the mining sector represents an42 economic opportunity, however, navigating the associa...

The global push towards decarbonisation may disrupt existing steelmaking supply chains. While this presents opportunities for Australia, it remains an open question as to what the country’s role should be within new international value chains. Here, we examine green steel production and export strategies between Australia and Japan, comparing diffe...

There is an increased international focus on achieving high environmental, socio-economic, and governance (ESG) outcomes within mineral supply chains, in addition to delivering positive economic results. Mineral exploration and development projects must balance these disparate objectives to the satisfaction of separate stakeholders. However, the ch...

Steelmaking value chains are economically important to Australia, but the need to decarbonise traditional steel-making processes could disrupt existing supply lines. Hydrogen-based iron and steel production offers one pathway for reducing the carbon intensity of steel. The opportunities and challenges presented by this technology, for Australia, ar...

Integration of 5D Building Information Modeling (BIM) into large rail projects has the potential to significantly enhance cost management and control. Nevertheless, 5D-BIM implementation has encountered difficulties stemming from technical, functional, and governance-related factors. This paper builds a conceptual framework to support financial dec...

This paper presents an approach for developing Reduced Order Models (ROMs) of complex geomechanical systems from high-fidelity numerical simulations. The approach uses proper orthogonal decomposition of the state variables for the model reduction, combined with long short-term memory neural networks to update the simulations in response to changing...

Integration of 5D Building Information Modelling (BIM) into large rail projects has the potential to significantly enhance cost management and control. Nevertheless, 5D-BIM implementation has encountered difficulties stemming from technical, functional, and governance-related factors. This paper builds a conceptual framework to support financial de...

Australia has ambitions to become a major global hydrogen producer by 2030. The establishment of Australia’s and the world’s hydrogen economy, however, will depend upon the availability of affordable and reliable hydrogen storage. Geological hydrogen storage is a practical solution for large scale storage requirements ensuring hydrogen supply can a...

Voxel grids are an increasingly common enabler for pathfinding in 3D spaces. Currently in this area there exists only a limited number of publicly available benchmarks. This makes it difficult to establish state-of-the-art performance and to compare the strengths and weaknesses of competing search techniques. In this work, we introduce three new an...

Mega projects delivering rail infrastructure are constantly seeking cost-effective and efficient technologies to sustain the growing population. Building information modeling (BIM) and BIM for cost management (5D-BIM) have shown great potential in the building industry and have been adopted widely. However, 5D-BIM implementation in rail infrastruct...

Green steel, produced using renewable energy and hydrogen, presents a promising avenue to decarbonize steel manufacturing and expand the hydrogen industry. Australia, endowed with abundant renewable resources and iron ore deposits, is ideally placed to support this global effort. This paper's two-step analytical approach offers the first comprehens...

Offshore wind farms are a current area of interest in Australia due to their ability to support its transition to renewable energy. Climate reanalysis datasets that provide simulated wind speed data are frequently used to evaluate the potential of proposed offshore wind farm locations. However, there has been a lack of comparative studies of the ac...

Green ammonia has received increasing interest for its potential as an energy carrier in the international trade of renewable power. This paper considers the factors that contribute to producing cost-competitive green ammonia from an exporter’s perspective. These factors include renewable resource quality across potential sites, operating modes for...

Clean hydrogen offers a pathway to deep decarbonisation of the global economy. Historically it has been cheaper to produce clean hydrogen using fossil fuels (pre 2022 prices) with carbon capture and storage (blue hydrogen) compared to using renewable energy with electrolysis (green hydrogen), but this gap is predicted to narrow over the coming deca...

The fractures in brown coal influence fluid flow and deformation in these materials. These fractures display highly heterogeneous characteristics in the distributions of their apertures, separations and orientations. While discrete fracture models have previously been used to analyse the effects of fractures, such models are not feasible for the sc...

Green ammonia has received increasing interest for its potential as an energy carrier in the international trade of renewable power. This paper considers Australia’s prospects for green ammonia production from an exporter’s perspective by highlighting Australia’s competitive advantage in renewable resource quality and seasonal complementarity to it...

In this paper, we consider two Adaptive Mesh Refinement (AMR) methods to simulate flow through fractures using a novel multiphase model. The approach represents the fluid using a two-dimensional parallel-plate model that employs techniques adapted from lattice-Boltzmann simulations to track the fluid interface. We discuss different mesh refinement...

This paper considers the influence of geometry and flow conditions on the relative permeability of wetting and non-wetting components of multiphase flows through fractures. Using an explicit immiscible two-phase fracture-flow model, 945 multiphase flow simulations were conducted on artificially-generated fracture geometries. These simulations accou...

Australian iron ore is predominantly exported and used for steelmaking internationally. However, steelmaking is an energy-and carbon-intensive heavy industry, and its electrification in the coming decades will likely disrupt the existing iron ore-steel value chains. Green steel-produced using hydrogen and electricity from renewable energy sources-p...

The ability to quickly compute shortest paths in 3D grids is a technological enabler for several applications such as pipe routing and computer video games. The main challenge is how to deal with the many symmetric permutations of each shortest path. We tackle this problem by adapting Jump Point Search (JPS), a well-known symmetry breaking techniqu...

The task of managing petroleum projects is often cumbersome and complex, as these projects involve a vast number of activities that are often conducted in remote and potentially dispersed locations. In addition, petroleum projects must reconcile the many transactions that occur between multiple stakeholders, including the developer and their contra...

Green steel – produced using hydrogen and electricity from renewable en-ergy sources – provides both the means to decarbonize steel manufacturing,and a way to facilitate growth of the international hydrogen industry. Aus-tralia, with its abundant renewable resources and ample iron-ore deposits,is in an excellent position to participate in this oppo...

The stability of open-pit brown-coal mines is affected by the manner in which water is transmitted or retained within their slopes. This in turn is a function of the in-situ fracture network at those mines. Fracture networks in real mines exhibit significant degrees of heterogeneity; encompassing a wide range of apertures, inter-fracture separation...

In this paper, we consider two Adaptive Mesh Refinement (AMR) methods to simulate flow through fractures using a novel multiphase model. The approach represents the fluid using a two-dimensional parallel-plate model that employs techniques adapted from lattice-Boltzmann simulations to track the fluid interface. Here, we discuss different mesh refin...

Silica sol gels have the potential to act as sealing agents to reduce leakage risks associated with long-term CO2 storage. This study considers the effects of brines of varying chemical composition on the formation of sol gels, their viscosity, and their long term stability. The gelation times of sol–gel solutions were measured for different concen...

Fully coupled hydro-mechanical simulations of fractured media require sophisticated non-linear solvers to capture the complex relationship between fluid flow and a material’s mechanical response. Such simulations may involve detailed meshes comprising millions of degrees of freedom. As a result, modelling these systems can be quite onerous, with th...

Multilateral wells promise cost savings to oil and fields as they have the potential to reduce overall drilling distances and minimize the number of slots required for the surface facility managing the well. However, drilling a multilateral well does not always increase the flow rate when compared to two single-horizontal wells due to competition i...

This paper describes a novel strategy to optimize the drilling time of three-dimensional (3D) directional wellbore trajectories using a vector-based approach subject to drilling and geological constraints. Many existing well-path models require manual entry for certain geological constraints such as formation dip or kick-off limit. In contrast, thi...

Assessments of hydrogen project viability typically focus on evaluating specific sites for development, or providing generic cost-estimates that are independent of location. In reality, the success of hydrogen projects will be intimately linked to the availability of local energy resources, access to key infrastructure and water supplies, and the d...

Fractures along interfaces between host rock and wellbore cement have long been identified as potential CO2 leakage pathways from subsurface CO2 storage sites. As a consequence, cement alteration due to exposure to CO2 has been studied extensively to assess wellbore integrity. Previous studies have focused on the changes to either chemical or mecha...

Cost and schedule overruns are endemic problems for offshore oil projects. This can be partly attributed to weather delays, resource limitations, and scheduling risks. The problem is further compounded because of the large number of interdependent activities, such as drilling and platform installation, typically involved in the buildup period of oi...

Assessments of hydrogen project viability typically focus on evaluating specific sites for development, or providing generic cost-estimates that are independent of location. In reality, the success of hydrogen projects will be intimately linked to the availability of local energy resources, access to key infrastructure and water supplies, and the d...

Borehole breakout initiation stress is critical for mining and geotechnical engineering as it indicates horizontal stress magnitudes and rock quality in a specific layer. This stress can be significantly intensified under laboratory conditions where the borehole size is small, although the specimen sizes in previous studies varied. This may result...

Flow through rock fractures is frequently represented using models that correct the cubic law to account for the effects of roughness and contact area. However, the scope of such models is often restricted to relatively smooth aperture fields under small confining stresses. This work studies the link between fracture permeability and fracture geome...

Critical Minerals Assessment (CMA) is concerned with the mineral inputs to a system (such as an economy or industry), the risks of a disruption to supply occurring, and the impacts that such a disruption would have on the system. Take for example Rare Earth Elements (REEs), which are presently considered to be critical minerals from the perspective...

This paper presents an integrated approach to planning wellbore trajectory, submarine pipeline networks, routes and production for offshore shallow-water oil and gas fields. The method integrates the optimization of realistic drilling well paths, platform location and well allocation using a combination of Constrained Optimization by Linear Approxi...

The Australian landscape is affected by abandoned mines that pose environmental, public health and safety risks. To promote the beneficial reuse, rehabilitation and/or remediation of these sites and understand their spatial arrangement, we compiled, classified and analysed a country-wide geospatial database of all known inactive hard rock mine site...

Plain Language Summary Representative elementary volumes or REVs are defined as the smallest volume of the rock sample that encompasses the region of local heterogeneities for the length scale and property being investigated. X‐ray micro‐computed tomographic (micro‐CT) images capture the rock structure as different gray‐level intensities. Tradition...

Thermal spallation drilling is a contact-less means of borehole excavation that works by exposing a rock surface to a high-temperature jet flame. In this study, we investigate crucial factors for the success of such thermal drilling operations using numerical simulations of the thermomechanical processes leading to rock failure at the borehole surf...

This is a White Paper from the Critical Minerals Consortium on Critical Minerals Assessment from an Australian perspective.

Mineral exploration ideally involves researching geological potential within the constraints of economic feasibility. Nevertheless, explicit consideration of economic factors is often delayed until late in the exploration cycle. This is not ideal. Like mineral prospectivity, projected economic feasibility can be used to refine the search space and...

Depleted oil reservoirs are considered a viable solution to the global challenge of CO2 storage. A key concern is whether the wells can be suitably sealed with cement to hinder the escape of CO2. Under reservoir conditions, CO2 is in its supercritical state, and the high pressures and temperatures involved make real-time microscopic observations of...

Frontier mineral exploration is often exclusively focused on assessing geological potential without consideration for the economic viability of resource development. This strategy may overlook potentially prosperous zones for more geologically-favoured but financially-disadvantageous regions, or conversely, may introduce implicit biases against pot...

Electropulse stimulation provides an energy-efficient means of excavating hard rocks through repeated application of high voltage pulses to the rock surface. As such, it has the potential to confer significant advantages to mining and drilling operations for mineral and energy resources. Nevertheless, before these benefits can be realized, a better...

Electropulse treatments employ a series of high-voltage discharges to break rock into small fragments. As these methods are particularly suited to fracturing hard brittle rocks, electropulse treatments can serve to enhance or substitute for more traditional mechanical approaches to drilling and processing of these materials. Nevertheless, while the...

The oil and gas industry is moving towards the use of non-metallic pipeline material, such as reinforced thermoplastic and flexible piping, for applications in offshore fields. However, these materials have certain pressure and diameter constraints that require careful analysis prior to deciding on the appropriate piping material to be installed. T...

Artificial Islands are often an effective strategy to develop shallow-water fields. However, their layout and design are affected by numerous drilling and surface facility constraints, such as water depth, number of wells, proximity to shore, and well spacing. When these constraints cannot be honored, conventional offshore wellhead platforms must b...

Slope stability of open cut brown-coal mines depends upon the permeability of the fracture network within the coal seam. In this paper, we provide a detailed analysis of the role of the fracture distribution on the permeability of brown-coal slopes and outline a model to capture this behaviour. Brown coal is relatively impermeable, but heavily frac...

Electropulse treatments employ a series of high-voltage discharges to break rock into small fragments. As these methods are particularly suited to fracturing hard brittle rocks, electropulse treatments can serve to enhance or substitute for more traditional mechanical approaches to drilling and processing of these materials. Nevertheless, while the...

Frontier mineral exploration is often exclusively focused on assessing geological potential without consideration for the economic viability of resource development. This strategy may overlook potentially prosperous zones for more geologically-favoured but financially-disadvantageous regions, or conversely, may introduce implicit biases against pot...

Frontier mineral exploration is often exclusively focused on assessing geological potential without consideration for the economic viability of resource development. This strategy may overlook potentially prosperous zones for more geologically-favoured but financially-disadvantageous regions, or conversely, may introduce implicit biases against pot...

The aim of this paper is to develop a novel specimen configuration optimised for developing and validating structure-property relationships for textile carbon fibre reinforced polymers (CFRPs). The specimen is designed to be imaged non-destructively using X-ray Microtomography (μCT), but is also optimised for in- and ex-situ mechanical testing. The...

Analytical solutions of near-borehole stress–strain responses are often based on simple elastic-perfectly plastic constitutive models. However, such models are incapable of capturing rock softening, and thus often disagree with observed failure patterns. Therefore, in this study, we present a set of closed-form solutions to estimate the stress–stra...

Advancements in drilling capabilities and the need to reduce the capital costs of field developments have led to increased interest in the exploitation of existing platforms to drill new wells. Although maximizing the use of existing assets is often advantageous as they offset the high cost of installing new facilities, employing these existing str...

Following the discovery of an offshore oil or gas field, extensive facilities must be built to drill, produce and transport the hydrocarbon from the reservoir to a plant for processing. Selecting the site, number and size of these facilities is one of the most crucial decisions in developing the field -- impacting not only the total investment, but...

Offshore oil and gas field developments are capital-intensive projects that require extensive facilities to drill, produce and transport the hydrocarbon from the reservoir to the processing plant. Determining the site, number and size of these facilities are amongst the most important decisions impacting a project's success. Here, we present a nove...

Wellbore integrity is a critical component of long-term carbon storage. Depleted reservoirs that are potential CO 2 storage sites, typically contain several wells. Due to years of operations and abandonment, these wells can have cracks in the cement, cement-casing interface, and/or cement-formation interface. During CO 2 injection, changes in tempe...

Wellbore leakage tops the list of perceived risks to the long-term geologic storage of CO2, because wells provide a direct path between the CO2 storage reservoir and the atmosphere. In this paper, we have coupled a two-phase flow model with our original framework that combined models for reactive transport of carbonated brine, geochemistry of react...

Table 2 and Eq. 3 of the original article are reported incorrectly. The correct Table 2 and Eq. 3 are shown.

We investigate how subsurface fluids of different compositions affect the electricity generation of geothermal power plants. First, we outline a numerical model capable of accounting for the thermophysical properties of geothermal fluids of arbitrary composition within simulations of geothermal power production. The behavior of brines with varying...

This work studies the roughness characteristics of fracture surfaces from a crystalline rock by analyzing differences in surface roughness between fractures of various types and sizes. We compare the surface properties of natural fractures sampled in situ and artificial (i.e., man-made) fractures created in the same source rock under laboratory con...

Wells are considered to be high-risk pathways for fluid leakage from geologic CO2 storage reservoirs, because breaches in this engineered system have the potential to connect the reservoir to groundwater resources and the atmosphere. Given these concerns, a few studies have assessed leakage risk by evaluating regulatory records, often self-reported...

Wellbore integrity is critical to long term carbon storage. During CO2 injection, changes in temperature may result in large stress variations that can damage the well, threatening its integrity. The different materials comprising the wellbore and near-wellbore environment (namely the casing, cement and surrounding rock) possess different thermal p...

This work investigates the possibility of replication of natural rock specimens, which can be used to analyze rock mechanical behavior by subjecting a number of identical specimens to tensile tests and a variety of analysis methods. We compare the properties of fractures generated in artificial sandstone specimens to those generated in natural sand...

Incorporating coupled Thermal-Hydro-Mechanical-Chemical (THMC) processes in lithospheric deformation models is a research frontier in the study of lithosphere dynamics. In this study we present a fundamental theoretical analysis on the important lithosphere deformation mechanism of creep enhanced by fluid-release reactions. This mechanism features...

Contact between wellbore cement and carbonated brine produces reaction zones that alter the cement's chemical composition and its mechanical properties. The reaction zones have profound implications on the ability of wellbore cement to serve as a seal to prevent the flow of carbonated brine. Under certain circumstances, the reactions may cause rese...

Proppant is a vital component of hydraulic stimulation operations, improving conductivity by maintaining fracture aperture. While correct placement is a necessary part of ensuring that proppant performs efficiently, the transport behavior of proppant in natural rock fractures is poorly understood. In particular, as companies pursue new propping str...

In this paper, we describe a method to non-invasively study the movement of proppant packs at the sub-fracture scale by applying three-dimensional digital image correlation techniques to X-ray tomography data. Proppant movement is tracked in a fractured core of Marcellus shale placed under a series of increasing confining pressures up to 10,000 psi...

This paper describes a fully coupled finite element/finite volume approach for simulating field-scale hydraulically driven fractures in three dimensions, using massively parallel computing platforms. The proposed method is capable of capturing realistic representations of local heterogeneities, layering and natural fracture networks in a reservoir....

Among the various risks associated with CO2 storage in deep geologic formations, wells are important potential pathways for fluid leaks and groundwater contamination. Injection of CO2 will perturb the storage reservoir and any wells that penetrate the CO2 or pressure footprints are potential pathways for leakage of CO2 and/or reservoir brine. Well...

Injection of supercritical CO2 into storage reservoirs causes thermally induced expansion and contraction inside the wellbore, potentially leading to the creation of leakage pathways. Determining a safe operating range for temperature and assessment of thermal stresses during CO2 injection is essential to ensure wellbore integrity. Although failure...

Double-emulsion microfluidic techniques can produce small spherical capsules, hundreds of microns or less in diam-eter, capable of containing a wide variety of materials. By carefully selecting the outer shell material, microcapsules can be created that release their contents (i.e., are “triggered”) under specific thermal or chemical conditions. As...

We investigate the flow-channeling phenomenon caused by thermal drawdown in fractured geothermal reservoirs. A discrete fracture network-based, fully coupled thermal–hydrological–mechanical simulator is used to study the interactions between fluid flow, temperature change, and the associated rock deformation. The responses of a number of randomly g...

Laboratory and field studies have demonstrated a strong correlation between the volume of proppant deployed in hydraulic-fracturing operations and subsequent reservoir productivity. In recent years, the desire to improve proppant performance has led to the development of new generations of exotic proppants, as well as new propping strategies. Never...

Solvent-free polymer-grafted nanoparticle fluids consist of inorganic core particles fluidized by polymers tethered to their surfaces. The attachment of the suspending fluid to the particle surface creates a strong penalty for local variations in the fluid volume surrounding the particles. As a model of such a suspension we perform Brownian dynamic...

Many challenging fluid-structure interaction problems in nuclear engineering remain unresolved because current CFD methodologies are unable to manage the number of computational cells needed and/or the difficulties associated with meshing changing geometries. One of the most promising recent methodologies for fluid dynamics modeling is the lattice-...

This paper describes the relationship between spall-size and aspect ratio observed in particles collected from a thermal spallation drilling field test conducted in Sierra white granite. Analysis of the particles reveals a decrease in spall aspect ratio with decreasing spall size -- a factor previously unconsidered in large-scale models of thermal...

The development of accurate, predictive models for use in determining wellbore integrity requires detailed information about the chemical and mechanical changes occurring in hardened Portland cements. X-ray computed tomography (XRCT) provides a method that can nondestructively probe these changes in three dimensions. Here, we describe a method for...

This paper investigates the effects of carbonated brine induced reaction zones on the mechanical and hydraulic properties of fractures and interfaces in wellbore cement. We present results from a suite of core flood experiments in which carbonated brine was introduced into artificial fractures separating wellbore-cement and tight-sandstone half-cor...