BEGIN:VCALENDAR VERSION:2.0 PRODID:-//Memento EPFL// BEGIN:VEVENT SUMMARY:MEchanics GAthering –MEGA- Seminar: Ascent and movement of buoya nt fluids in the lithosphere DTSTART:20231019T161500 DTEND:20231019T173000 DTSTAMP:20260925T203555Z UID:472e2e3db169bfe2e5622d082c06e374b5eab46a91c732a1e94cb888 CATEGORIES:Conferences - Seminars DESCRIPTION:Andreas Möri (GEL\, EPFL)\nAbstract\nHydraulic fractures are driven by an internal fluid pressure exceeding the minimum compressive str ess\, propagating\nin a direction perpendicular to the latter. This class of tensile fractures has gained interest over the last fifty years due\nto the development of multiple engineering applications. Among these industr ial applications are well-stimulation\ntreatments by hydraulic fracturing used in the oil and gas industry to enhance the permeability of tight rese rvoirs.\nThe same technique is used in geothermal systems to increase prod uction. It has become of increased interest\nrecently in the discussion ab out the energy transition thanks to the idea of orange hydrogen production \, carbon\ncapture and sequestration\, and the use of the underground for fracture thermal or elastic energy storage. But buoyant\nhydraulic fractur es occur not only due to anthropogenic actions but also naturally. The mos t dramatic manifestation\nof such fractures is the process of magma migrat ion at a large scale in so-called dikes and sills. Generally\, the ascent\ nof geothermal fluids in subduction zones or at hot spots can also be rela ted to such processes.\nMost anthropogenic applications are performed in s edimentary basins. In these geological formations\, the minimum\ncompressi ve stress is usually horizontal and increases with depth. As a result\, hy draulic fractures grow along\nvertical planes. Because the density of the fluid and solid are generally different\, a buoyant force between the\nhyd rostatic pressure gradient and the background stress emerges. This force c auses the fracture to deviate from\nits initially radial propagation towar ds an elongated growth in the direction of gravitational acceleration. Onc e\ninitiated\, it is essential to note that this propagation is self-susta ined\, meaning that with no further source of external\nenergy\, the fract ure will continue to propagate. Such propagation is notably dangerous if d irected upwards\, as\npotentially sensitive aquifers could be infiltrated. In our work\, we quantify this elongated propagation and study\nhow this relates to the dominant energy dissipation mechanisms (viscous flow of the fluid in the fracture against the\nenergy used for fracture surface creat ion.\nIn the first part\, we have studied the emergence and propagation of such fractures from a linear elastic fracture\nmechanics (LEFM) viewpoint using scaling analysis and numerical simulations. We could notably show t hat the\nentire history of such fractures can be related to only two dimen sionless numbers combining the properties of the\nsolid (density\, elastic ity\, fracture resistance)\, the fracturing fluid (density\, viscosity)\, and the fluid release (rate\,\nrelease time). We could characterize the po ssible emergence and the various self-similar solutions of buoyant\nhydrau lic fractures. Lately\, we have started investigating the effects of heter ogeneities and other mechanisms\, like\nfluid mass changes\, on the propag ation of hydraulic fractures. At the current state of our research\, we co ntinue\nto investigate various aspects to increase the comparability of ou r results and findings with industrial and natural\noccurrences of buoyant hydraulic fractures.\n\nBiography\nAndreas Möri is currently a post-doc in the Geo-Energy Laboratory (GEL) in the Civil Engineering Department\nat EPFL. He obtained his Bachelor’s and Master’s degrees in Civil engine ering from EPFL with a specialization\nin geotechnical construction and eq uivalent credits in structural engineering. During his studies\, his inter est was\ndirected toward the localization of deformation\, respectively fr acturing\, of geomaterials coupled with fluid flow\ninside localized fract ures and the bulk. During his Master’s project\, he focused on shear loc alization as the initiation\nmechanisms of landslides and investigated a c reeping landslide in the Swiss pre-alps. He performed early work on\nhydra ulic shear fractures\, studying the remote nucleation of aseismic slip due to the stress transfer caused by an\naseismic shear fracture. In his Ph.D .\, he shifted towards opening mode hydraulic fractures and notably invest igated\nthe influence of gravitational forces on their propagation\, emerg ence\, and arrest. During his thesis in the GEL lab\, he\nbecame an expert on buoyant hydraulic fractures. He could relate previously existing late- time and two-dimensional\nsolutions to such fractures’ full\, three-dime nsional planar propagation. Thanks to his expertise in the scaling\nanalys is and numerical validation of fundamental physical processes in fully cou pled hydromechanical problems\, he\nfurther laid the basis for studying va rious additional mechanisms related to different occurrences of such fract ures.\nThese mechanisms include heterogeneities\, size-dependent effects\, and fluid mass losses. Additionally\, he has been\npassionate about study ing poroelastic effects on hydraulic fracture propagation\, where he is cu rrently finishing some\nprojects started during his thesis. He obtained hi s Ph.D. from EPFL in September 2023 before switching to a\npost-doc positi on in the same lab. This project-based position is sought to validate the feasibility of fracture thermal\nenergy storage through lab experiments. H e currently performs experiments with circulating high-temperature fluids\ nin previously created hydraulic fractures in large-scale rock specimens. In the project’s further development\, he will\ntry to create multiple f ractures in such samples\, including a subsequent charge and discharge of the designed thermal\nbattery. LOCATION:MED 2 2423 https://plan.epfl.ch/?room==MED%202%202423 https://epf l.zoom.us/j/67432145299?pwd=RXo4dHBQaFhFbktzYVdIa2xGOEhqUT09 STATUS:CONFIRMED END:VEVENT END:VCALENDAR