Showing papers by "Andy Wilkins published in 2021"
TL;DR: In this paper, the authors introduce a physics module for non-isothermal, multicomponent, multiphase flow in porous media, as part of the open-source multiphysics simulation framework MOOSE.
11 citations
TL;DR: RHEA as discussed by the authors is an open-source, fully coupled, finite-element application capable of including element-resolution hydro-geomechanical properties in coupled simulations, which can be used for the assessment of many hydrological and geotechnical applications.
Abstract: . Realistic modelling of tightly coupled hydro-geomechanical processes is relevant for the assessment of many hydrological and geotechnical applications. Such processes occur in geologic formations and are influenced by natural heterogeneity. Current numerical libraries offer capabilities and physics couplings that have proven to be valuable in many geotechnical fields like gas storage, rock fracturing and Earth resources extraction. However, implementation and verification of the full heterogeneity of subsurface properties using high-resolution field data in coupled simulations has not been done before. We develop, verify and document RHEA (Real HEterogeneity App), an open-source, fully coupled, finite-element application capable of including element-resolution hydro-geomechanical properties in coupled simulations. To extend current modelling capabilities of the Multiphysics Object-Oriented Simulation Environment (MOOSE), we added new code that handles spatially distributed data of all hydro-geomechanical properties. We further propose a simple yet powerful workflow to facilitate the incorporation of such data to MOOSE. We then verify RHEA with analytical solutions in one and two dimensions and propose a benchmark semi-analytical problem to verify heterogeneous systems with sharp gradients. Finally, we demonstrate RHEA's capabilities with a comprehensive example including realistic properties. With this we demonstrate that RHEA is a verified open-source application able to include complex geology to perform scalable, fully coupled, hydro-geomechanical simulations. Our work is a valuable tool to assess challenging real-world hydro-geomechanical systems that may include different levels of complexity like heterogeneous geology and sharp gradients produced by contrasting subsurface properties.
8 citations
TL;DR: In this paper, the authors used a convolutional neural network (CNN) to estimate the recovery efficiency of a single-well aquifer thermal energy storage (ATES) system with injection temperatures as high as 300 ∘ C.
6 citations
TL;DR: In this paper, the authors investigated the performance of vertical goaf drainage holes during underground long-wall coal extraction by using 3D finite element modeling and 2D discrete element simulation techniques.
Abstract: During underground longwall coal extraction, overburden strata deformation may result in vertical goaf drainage holes, which are drilled in advance of mining for tail gate gas management, to fail. The performance of these vertical goaf drainage holes is controlled by mine design parameters and local geomechanical properties. This paper investigates the use of advanced 3D finite element modelling and 2D discrete element modelling simulation techniques to understand the fundamentals of vertical goaf drainage hole failure mechanism due to strata shear at a currently operating gassy Australian mine site. Finite element modelling is used to investigate the location of high shear in the overburden strata at the vertical goaf gas drainage hole region during longwall mining and the discrete element modelling is used to examine connectivity from the goaf region to the goaf-gas drainage system.
4 citations
TL;DR: The CO2CRC Otway Stage 3 project is developing low-impact methods for near-continuous monitoring of storage sites as discussed by the authors, including the deployment and use of distributed acoustic sensors on casing, and baseline injections and interpretation of pressure tomography.
Abstract: The CO2CRC Otway Stage 3 project is developing low-impact methods for near-continuous monitoring of storage sites. This paper reports on the design, drilling, instrumenting, and early results from an array of an injector and five monitoring wells, spread over a km2. Highlights include the deployment and use of distributed acoustic sensors on casing, and baseline injections and interpretation of pressure tomography.
3 citations
TL;DR: In this article, a geotechnical model has been developed to compare the conceptualized goaf-hole failure mechanism with the simplified representative model, and the effect of geo-mechanical properties and panel widths on shear development has also been investigated.
Abstract: Most of the published research on goaf-hole failures are performed using 2D numerical analyses. However, 2D analyses of the goaf-hole failure mechanism, which is truly a 3D problem, often do not provide a full picture of strata movement and stress change effect. In particular such 2D models completely fail to capture the longitudinal deformation and associated shear component yielding a false sense of goaf-hole stability. This paper uses advanced 3D numerical modelling to understand the fundamentals of goaf-hole shear failure mechanism and conceptualize the transverse, longitudinal and total shears developments during longwall extraction. A mine specific geotechnical model has been developed to compare the conceptualized goaf-hole failure mechanism with the simplified representative model. The effect of geo-mechanical properties and panel widths on shear development has also been investigated. The analysis is based on a case study; however, it is expected that the results presented in this paper will be applicable to other mines with similar geological environment or will at least highlight the need for a 3D modelling to capture the true three-dimensional strata deformation behaviour and goaf-hole shearing mechanism enabling safe and stable vertical drainage hole design. In the modelled scenario, the shear increased as the face advanced, and large shears would be experienced behind 50–100 m of the face. The longitudinal shear was dominant towards the centre of the panel and the transverse shear was dominant towards the panel edges. The layered seam appeared to generate lesser shear compared to the solid seam; this could be attributed to the dissipation of shear in the layer strata of the material.
2 citations
TL;DR: In this paper, the authors used the MOOSE software to analyze the geomechanical response of a reservoir to nonisothermal, multi-phase fluid injection, which has been used in studies of CO 2 sequestration.
1 citations
TL;DR: In this article, the spread and persistence of a population-modifying gene drive system in these subspecies across sub-Saharan Africa, by simulating introductions of genetically modified mosquitoes across the African mainland as well as on some offshore islands, was investigated.
Abstract: Malaria is one of the deadliest vector-borne diseases in the world. Researchers are developing new genetic and conventional vector control strategies to attempt to limit its burden. To be deployed responsibly and successfully, proposed novel control strategies require detailed safety assessment. Anopheles gambiae sensu stricto (s.s.) and Anopheles coluzzii, two closely related subspecies within the species complex Anopheles gambiae sensu lato (s.l.), are among the dominant malaria vectors in sub-Saharan Africa. These two subspecies readily hybridise and compete in the wild and are also known to have distinct niches, each with spatially and temporally varying carrying capacities driven by precipitation and land use factors. We model the spread and persistence of a population-modifying gene drive system in these subspecies across sub-Saharan Africa, by simulating introductions of genetically modified mosquitoes across the African mainland as well as on some offshore islands. We explore transmission of the gene drive between the subspecies, different hybridisation mechanisms, the effects of both local dispersal and potential wind-aided migration to the spread, and the development of resistance to the gene drive. We find that given best current available knowledge on the subspecies9 life histories, an introduced gene drive system with typical characteristics can plausibly spread from even distant offshore islands to the African mainland with the aid of wind-driven migration, with resistance taking over within a decade. Our model demonstrates a range of realistic dynamics including the effect of prevailing wind on spread and spatio-temporally varying carrying capacities for subspecies. We thus show both the plausibility and importance of accounting for a wide range of mechanisms from regional to continental scales.
1 citations