PhD Research Fellow in mathematically oriented geophysics - VISTA Center for Modeling of Coupled...

The Department of Earth Science  has a vacancy for a PhD position in mathematically oriented geophysics with start date between 1 April and 1 November. The position is part of the recently established VISTA Center for Modeling of Coupled Subsurface Dynamics (VISTA CSD , https://www.uib.no/en/vista-csd ). VISTA is a basic research programme financed by Equinor and executed in close cooperation with The Norwegian Academy of Science and Letters. The center involves approximately 40 people, including faculty, researchers, postdocs and PhD and master students. The position is for a fixed-term period of 3 years with the possibility of a 4 th year with compulsory other work (e.g., teaching duties at the Department).

Production of hydrocarbons and geothermal energy, extraction of groundwater, subsurface energy storage, CO2 sequestration and wastewater disposal all involve massive subsurface extraction and/or injection of fluids. This affects the thermal, hydraulic, mechanical and chemical (THMC) state at depth, resulting in strongly coupled THMC processes. In recent years, the surface manifestations fluid injection and production have become increasingly apparent.

To improve engineering operations and avoid unacceptable environmental impact, there is a need to understand how fluid injection and extraction effects the mechanics of the geological formation to cause deformation of porous rocks as well as slip, opening and propagation of fractures and faults. These processes can be studied by a combination of data analysis and mathematical modeling and simulation.

VISTA CSD’s primary objective is to develop fundamental knowledge and educate next generation researchers to understand how subsurface fluid injection and extraction results in deformation, fault reactivation and fracturing. The center thus targets critical and fundamental research questions through mathematical and numerical modeling and data analysis.

The method under study in this project represents a generalization of Dix’ classic method for estimating local (interval) wave velocities from their corresponding root-mean-square (RMS) velocities. The generalization is foreseen implemented as a fully data-driven process for estimation of local wave velocities and their mapping from time to depth in three dimensions.

The overall goal of the project is to demonstrate that the generalized Dix method can be useful in the context of monitoring micro-earthquakes and mapping/imaging of seismic diffractions in the subsurface. This will involve 1) to develop a new generalized Dix reconstruction with improved stability and a regularization approach, 2) to replace this reconstruction using an artificial neural network (ANN), and 3) to study the dynamics in the Dix data by means of an ANN architecture.