PhD: Unravelling Clogging Mechanisms in Porous and Fractured Rocks

In the energy transition many technologies rely on the injection and extraction of energy carriers, like geothermal heat, CO2 and hydrogen. Repeated fluid pumping could lead to clogging of fluid pathways. Are you ready to dive into the how, using cutting-edge imaging techniques? Then the Department of Earth Sciences is looking for you! We would welcome a highly motivated and ambitious applicant for a PhD position to contribute to our research theme Sustainable Use of the Subsurface. Your job Clogging in geological formations poses critical challenges for subsurface applications from geothermal energy to CO₂ and hydrogen storage. While individual clogging mechanisms have been studied extensively, the dynamic interplay between physical particle deposition, chemical precipitation, and deformation-induced particle remobilisation remains poorly understood. These processes vary fundamentally across rock types – from porous sedimentary to fractured crystalline systems, with volcanic and altered crystalline rocks presenting unique intermediate cases. Recent advances in operando micro-computed tomography (µCT) enable unprecedented real-time visualisation of these processes, yet systematic investigation across diverse rock types and integration with predictive models remains lacking. In this PhD study, you will be performing experiments and numerical simulations to understand and predict the clogging evolution in a range of geological media by:

• Quantifying physical and chemical clogging dynamics across a spectrum of rock types (porous sedimentary, porous volcanic, altered crystalline, and fractured crystalline rocks) using 4D µCT imaging
• Establishing the role of deformation in particle remobilisation and preferential flow path creation that controls clogging patterns
• Developing predictive digital rock physics and permeability evolution models from µCT data using machine learning and computational tools (PuMA/CHFEM/MOOSE) validated against experimental observations
• Bridging scales from pore-level processes (µm) to sample-scale behaviour (cm) through integrated experimental-numerical approaches

To achieve this, you will be doing in-situ experiments using our state-of-the-art in-house Zeiss Versa 610 µCT-scanner equipped with custom flow-through cells to capture clogging evolution. In addition, we will apply for beamtime at a synchrotron facility across Europe for critical experiments requiring very high imaging rates or ultra-high resolution. These experiments will be coupled with large- and small-scale flow-through experiments, using capabilities available at the High Pressure and Temperature Laboratory (in collaboration with Dr Suzanne Hangx) and the Porous Media Lab (in collaboration with Dr Amir Raoof) at the Department of Earth Sciences, to examine particle mobilisation thresholds, and how stress-induced deformation remobilises particles, creates new flow pathways, and redistributes clogging zones. Your experimental data and observations will be used to upscale from pore-scale physics to continuum behaviour. If you are thrilled to dive deep into the world of real-time imaging for sustainable energy solutions, this is a great opportunity for you! This position offers you the chance to explore your passion for understanding the impact of subsurface activities and boost your career with high-impact research in a field that is rapidly growing. The main supervisor of the study is Dr Roberto Rizzo. Training A personalised training programme will be set up reflecting your training needs and career objectives. About 20% of your time will be dedicated to this training component, which includes following courses and/or workshops (some of which are mandatory), as well as training on the job in assisting in the bachelor’s and master’s degrees programmes of the department at Utrecht University. Through interactions with the various scientists and stakeholders, you will be exposed to potential career paths in both academia and industry, helping you guide your future. Your qualities The successful applicant will hold an MSc in Earth Sciences, Geology, Physics, or related field by the time the position starts. Good quantitative skills and programming experience (Python/MATLAB/Julia) are essential. Ideally, you will have experience with acquisition and processing of tomographic images, rock mechanics, machine learning and/or numerical modelling. Given the highly diverse nature of the research groups that you will be working with, excellent communication (written and spoken English) and interpersonal skills are essential. In return, you will be part of an international team in an inspiring environment. If you already have a PhD degree, then we unfortunately cannot consider you for this position. Do you feel that you are a good match for the position but feel you do not meet all of our requirements, or have questions regarding the skills you may need? Then get in touch with us, so we can explore how you potentially can learn and grow in this position. Our offer We offer:

• a position (1.0 FTE) for 1 year, with an extension to a total of four years upon a successful assessment in the first year, and with the specific intent that it results in a doctorate within this period;
• a working week of 36 - 40 hours and a gross monthly salary between € 3.059 and €3.881 in the case of full-time employment (salary scale P under the Collective Labour Agreement for Dutch Universities (CAO NU));
• 8% holiday pay and 8.3% year-end bonus;
• a pension scheme, partially paid parental leave and flexible terms of employment based on the CAO NU.

In addition to the terms of employment laid down in the CAO NU, Utrecht University also offers a range of its own schemes for employees. This includes arrangements for professional development, various types of leave, and options for sports and cultural activities. You can also tailor your employment conditions through our Terms of Employment Options Model. In this way, we encourage you to keep investing in your personal and professional development. For more information, please visit Working at Utrecht University. About us A better future for everyone. This ambition motivates our scientists in executing their leading research and inspiring teaching. At Utrecht University, the various disciplines collaborate intensively towards major strategic themes. Our focus is on Dynamics of Youth, Institutions for Open Societies, Life Sciences and Pathways to Sustainability. Sharing science, shaping tomorrow. Utrecht University’s Faculty of Geosciences studies the Earth: from the Earth’s core to its surface, including man’s spatial and material utilisation of the Earth – always with a focus on sustainability and innovation. With 3,400 students (BSc and MSc) and 720 staff, the faculty is a strong and challenging organisation. The Faculty of Geosciences is organised in four Departments: Earth Sciences, Human Geography & Spatial Planning, Physical Geography, and Sustainable Development. The Department of Earth Sciences conducts teaching and research across the full range of the solid Earth and environmental Earth sciences, with activities in almost all areas of geology, geochemistry, geophysics, biogeology and hydrogeology. Our key research themes are Earth & Planetary Processes, Sustainable Use of the Subsurface, Planetary Health & (the) Environment, and Climate & Life. The department hosts a highly international tenured staff of over 50 scientists and more than 110 PhD students and postdoctoral researchers. We house or have access to a wide variety of world-class laboratories, among which are UU’s Electron Microscopy Centre, the Geolab, and the Earth Simulation Lab. We also have excellent High- Performance Computing facilities. About Utrecht The department and its facilities are located at Utrecht Science Park. Utrecht is the fourth largest city in the Netherlands with a population of nearly 360,000 and forms a hub in the middle of the country. Its historical city centre and its modern central station can easily be reached from the Science Park by public transport or by a 15-minute bicycle ride. Utrecht boasts beautiful canals with extraordinary wharf cellars housing cafés and terraces by the water, as well as a broad variety of shops and boutiques. More information For additional information (not for application!) please contact Dr Roberto Rizzo via r.e.rizzo@uu.nl, or Dr Suzanne Hangx via S.J.T.Hangx@uu.nl. Candidates for this vacancy will be recruited by Utrecht University. Apply now As Utrecht University, we want to be a home for everyone. We value staff with diverse backgrounds, perspectives and identities, including cultural, religious or ethnic background, gender, sexual orientation, disability or age. We strive to create a safe and inclusive environment in which everyone can flourish and contribute. You can only apply via our online procedure using the 'apply now' button. E-mail applications cannot be accepted. Include the following information in your application:

• a letter of motivation, using the attached template;
• your curriculum vitae, including any courses taken that are relevant for the position;
• academic credentials (mark sheets and degree statements), as far as already available.

No reference letters need to be submitted in your initial application. If you are short-listed, we will contact you for referees. We aim for a quick selection procedure after the application deadline of December 14th, 2025. We aim for a quick selection procedure after the deadline. The position is already available from February 1st, 2026, or preferably as soon as possible thereafter. Note that international candidates that need a visa/work permit for the Netherlands require at least four months processing time after selection and acceptance. This will be arranged with help of the International Service Desk (ISD) of our university. Finding appropriate housing in or near Utrecht is your own responsibility, but the ISD may be able to advise you therewith. In case of general questions about working and living in The Netherlands, please consult the Dutch Mobility Portal. Online screening may be part of the selection. Commercial response to this ad is not appreciated.