PHD PROJECT:  UNCERTAINTY QUANTIFICATION OF GEOMECHANICALLY SENSITIVE RESERVOIRS USING PHYSICS-INFUSED MACHINE LEARNING

What is the problem?

When we use the subsurface to store CO2 or Hydrogen, the rocks can deform inelastically as the reservoir conditions change – processes well described in geomechanics. But this permanent strain can lead to significant leakage and to induced seismicity risks during operation and/or long term storage. At worst, these risks pose a substantial threat to property and health – so much so that regulators and investors may halt projects before they start as we can’t correctly estimate the geomechanically-derived risks.

The key technical challenge for most storage reservoirs is to accurately quantify uncertainties and risks associated with geomechanical property changes from a few computer model forecasts. Geomechanical simulation software is complex and data-intensive, each run taking many hours to days. Such long run times make statistically thorough methods to quantifying uncertainty impractical. In most circumstances, we can’t afford the thousands of required model realisations. So such risks may be misestimated or even missed.

The longest model run times occur when we couple simulations of fluid flow (production and injection) with geomechanical simulations to predict how a development plan may alter the reservoir rocks properties and how this will impact fluid movement and field operations. To solve the system of equations for fluid flow and geomechanics together, we need to connect very different modelling approaches, the differences in the solvers typically precluding full coupling. Instead, the packages interact by running separately but simultaneously and passing data back and forth between iterations. This is a technically monumental challenge and the run times of the models are far longer than the combined times of each model run separately.

To accurately quantify uncertainties in geomechanically sensitive reservoirs we must run many more models than we do today, exploring a more diverse set of geological scenarios. But to run more models, we must significantly improve the efficiency of coupling fluid flow and geomechanical simulations. Machine learning provides one solution: once trained on an appropriate data set it can capture complex, non-linear systems very rapidly.

PhD position available at the Unit of Geotechnical Engineering of the University of Innsbruck in our doctoral program ‘Natural Hazards in Mountain Regions’. More details under:

https://www.uibk.ac.at/geotechnik/staff/schneider-muntau/job_advertisement_phd_dp_natural_hazards.pdf

We are looking forward to the applications of motivated people!

Applications are invited for a PhD student at the University of Liège, to work on Unsaturated soil mechanics – Experimental and constitutive focus on desiccation cracking in fine-grained soils.

The PhD candidate will also take part in teaching activites related to soil and rock mechanics courses. The research and teaching assistant position is granted for a first term of two years, renewable for up to 2 further periods of 2 years.

Project description

The mechanics of desiccation cracking is a complex hydro-mechanical process, induced by soil drying in partially or totally strain-constrained conditions. Desiccation cracks may affect significantly the hydro-mechanical properties of fine-grained soils (strength weakening, increased compressibility, increased permeability), leading to potential geotechnical issues (landslide triggering, soil erosion, leakage of impermeable barrier, …).

In the framework of unsaturated soil mechanics, this study will investigate the conditions of desiccation cracks triggering, their propagation and their aperture evolution, from experimental and constitutive approaches. Suction control techniques, image analysis and tensile strength testing will be developed. A particular attention will be devoted to the determination of tensile strength criterion at various suctions, through innovative experimental developments

The experimental characteristics will then be encapsulated in constitutive laws and implemented in a finite element code. The numerical simulations will incorporate the modelling of water evaporation, the hydro-mechanical response of soil upon drying, the tensile strength criterion and the impact on the presence of the crack mechanical and hydraulic response of the ground. Finally, the methodology will be applied to study the conditions of occurrence of desiccation cracking in full-scale problems (earthfill dike, nuclear waste disposal gallery, landfill waste disposal, agricultural soils, …).

Requirements and application procedure

The position is open to graduated students (Master degree) in Civil Engineering, Geosciences or related disciplines.

Applicants should have a high level of proficiency in written and spoken English. The successful candidate is also expected to learn French during his first two years.

Applications must be sent by email to Prof. Frédéric Collin (F.Collin@uliege.be). It should include a motivation letter, a CV and a short abstract of the Master thesis. Please contact Prof. Frédéric Collin if you need more information.

Applications are welcome before 12^th July 2021. The starting date is at the latest the 1^st October 2021.

Applications are welcomed for a joint PhD position KULeuven-UCLouvain starting October 1, 2021.

The objective of the project is to develop a better understanding of the soil-structure interaction during the installation and operational use of piles installed by vibratory driving for Offshore wind turbines. Semi-analytical and numerical models will be developed and calibrated using cyclic triaxial tests in conditions characteristic for offshore environments. The results of the models will be compared to reduced scale experiments of impact and vibratory driving for the installation and the extraction, but also the mechanical behavior of the pile subjected to cyclic loading under wind and wave loading. The developed methodology will be applied to actual case studies, aiming at a characterization of the soil-pile interaction and providing design guidelines.

To apply and get more detailed information, please see https://www.kuleuven.be/personeel/jobsite/jobs/60029856?hl=en

The Nottingham Centre for Geomechanics (NCG) is currently undertaking two large multi-disciplinary projects related to investigating the behaviour of coal-mining spoil materials with a focus on the geotechnical, sustainability, environmental, socio-economic and long-term management challenges. NCG brings together expertise from the worlds of civil, geotechnical, and mining engineering as well as mathematics and material sciences to solve all forms of soil and rock-related design and construction problems. The projects are funded by the European Commission Research Fund for Coal and Steel (RFCS) and include project partners from across Europe. We seek a highly motivated researcher to join our team to work on this challenging project.

We are looking to recruit a post-doctoral researcher who will support the work of these RFCS projects as well as support the wider work of the research group. We would consider any candidate with a strong fundamental geotechnical background.

Candidates should be inquisitive, with a strong interest in applied research, and the personality and drive to interact effectively with industry and project partners. They will have a first degree in Civil Engineering or cognate subject and will have been awarded a PhD (or have submitted their thesis for examination), ideally in an area of Geotechnical Engineering. The successful candidate will have good presentation and report writing skills. A good publication record will be an advantage but its absence should not hinder applications from those who have recently submitted their theses.

For application details see https://www.nottingham.ac.uk/jobs/currentvacancies/ref/ENG196421

Further information about the work of the Nottingham Centre for Geomechanics is available on www.nottingham.ac.uk/ncg/

Applications are invited for a PhD student at Delft University of Technology, to work on the development, implementation and application of a multiscale numerical testing environment for geomaterials.

For further details, please see the attached document or visit https://www.tudelft.nl/over-tu-delft/werken-bij-tu-delft/vacatures/details/?jobId=3083

« Fluid phase change simulation in porous and cracked media based on multimodal full-field measurements»

Project summary

The performance of reinforced concrete containment structures is analysed with respect to their ability to prevent a fluid from percolating through the wall barier. For concrete structures, the leaks break down into two flows, one of which passes through the porous networks of the cement matrix and the other passes through eventual cracks and crack network space. Conventionally, the fluids used to experimentally test the tightness are either liquid water or a neutral gas. In reality, the percolating fluid could be more complex, consisting of a multiphase mixture of air and hot water vapour.

The present project aims to pursue towards the quantitative experimental analysis and numerical multi-physics modelling of the two-phase (hot steam and air) flow and condensation processes during injection into fractured concrete material. Indeed, first ever experiments of in-situ quantitative visualization of vapour condensation in cracked concrete through high-speed neutron radiography have been performed revealing a complex interplay between pressure and sorption flow phenomena and a significantly different behaviour between dry and saturated sample.

Project summary

The project aims at studying numerically the rheological properties of suspensions of hard to soft spheres, dispersed in a Newtonian fluid, which are found in many industrial and geophysical processes. Using a DEM approach, and a recently developed model of lubricated contact, we will study the role of particle deformability, an essential ingredient which is usually overlooked in existing simulations. Deformability is crucial to regularize the divergence of the lubrication forces at contact, but its effects on the suspension rheology remain to be investigated in depth.

Our recently developed model of lubricated contacts [Chevremont et al., Powder Tech. 2020] produced new results related to the role of contact friction [Chevremont et al., Phys. Rev. Fluids 2019] and led to a complete set of constitutive relations for dense suspensions [Chevremont et al., arxiv.org/abs/2103.03718]. This model is implemented in the open source code yade-dem.org. We are now able to tackle efficiently the case of slightly deformable particles, for which lubrication, friction and deformability are strongly coupled.

At a macroscopic level, these effects are ignored by the established “μ(Iv)” constitutive model of hard sphere suspensions, as there is a new dimensionless number characterizing the ratio of viscous stresses to particle stiffness, the capillary number Ca. One goal of this project is to extend the μ(Iv) rheology to a phenomenological μ(Iv,Ca) rheology, which we will characterize by DEM simulations with systematic variations of the particle deformability, in a large range of volume fractions and shear rates.

We will also focus on viscous resuspension, which occurs when an external force field (typically gravity) is exerted on a flowing buoyant suspension, leading to gradients of volume fraction. This phenomenon is closely related to particle migration and the study of the transient regime from a homogeneous (non flowing) suspension to the re-suspended steady state will lead to improve existing continuum models by determining expansional viscosity.

This numerical project will be conducted in close relation to an ongoing experimental study.

The University of Bath is inviting applications for the following PhD project commencing in October 2021:

“Untangling the mechanical behaviour of grass-rooted soil layers for sustainable infrastructure construction”

For more detailed information, please see https://www.findaphd.com/phds/project/untangling-the-mechanical-behaviour-of-grass-rooted-soil-layers-for-sustainable-infrastructure-construction/?p130622

About the position: We have a vacancy for a 3-year R&D project within computational geomechanics at BAW Bundesanstalt für Wasserbau Federal Waterways Engineering and Research Institute Department of Geotechnical Engineering in Karlsruhe, Germany. The R&D-position’s main objective is to improve open source geomechanical analysis tools and to qualify the candidate for research positions.

Duties of the position: The R&D project aims at the validation and further development of poroMechanicalFoam, an openFOAM based FVM-model for hydro-mechanical analysis of flow-structure-soil interactions considering variable soil saturation. Based on analytical solutions and experimental data the impact of spatial and temporal discretization on robustness and accuracy shall be determined. The model performance shall be tested based on case studies from the geotechnical engineering practice at BAW considering representative aspects among others anisotropy of the mechanic and/or hydraulic properties, advanced soil material models (bounding surface plasticity), variable saturation and gas entrapment below the phreatic surface. In the final stage predictable failure mechanisms are to be addressed within the framework of the second order work concept. If desired, there is possibility for laboratory tests for characterization of soil properties and or/ identification of aspects yet not properly captured in poroMechanicalFoam.