RESEARCH INTERESTS
Seismic Imaging of Fractured Rock
Uncertainty associated with large geophysical models and joint inversion
Proper assessment of the uncertainty associated with geophysical and other scientific results is crucial to decision makers in the formulation of effective assessment both the safety and financial risk pertaining to planning decisions regarding hydrocarbon exploration, mining, and construction in the vicinity of earthquake zones.
Of great benefit in assessing structural uncertainty is the ability to combine understanding from multiple kinds of datasets, rather than relying on that obtained from a single method or technique. The JIBA (Joint Inversion with Bayesian Analysis) project was a collaboration between researchers in the Earth Sciences and Mathematics departments at Durham University and Geomar, Germany, as well as industrial partners. It was focused on creating both deterministic and statistical methods for the joint inversion of seismic, gravity and magnetotelluric (MT) datasets.
My role in the project, and a subject of ongoing interest, was the development of a prototype emulator-based very fast Monte Carlo screening method for a large loosely-coupled joint model space. The result is a rock probability map for the region of earth of interest. The method has been applied to the imaging of a salt dome structure, as featured in Geophysics, 2016.
CO2 injection into low pressure gas reservoirs
Deep Crustal Seismic Imaging
From the safety monitoring of stimulated hydrofracturing ("fracking") operations to maximising the yield from an existing subsurface reservoir, being able to understand subsurface rock fracture systems is of major relevance and importance. Most fracturing is well below the scale of a typical seismic wavelength and so understanding the impact of fracturing on the seismic wave-field is of great interest. With co-workers at Geospatial Research Limited (GRL), work is being undertaken, through simulation, the effect of fracturing on the seismic wave-field with a view to making more informed inference from seismic data as to the subsurface structure. Publication of our results is currently in progress.
It is becoming increasingly commonplace for CO2 produced from industrial processes to be injected into depleted oil and gas reservoirs. Such targets are advantageous for a number of reasons, in particular because the geological structural traps are already known to exist. Most injection schemes currently deployed are done so under conditions where the depleted reservoirs are still at relatively high pressure. In many depleted reservoirs, however, the pressure is very low. Under low pressure, the phase behaviour of CO2 is complicated, and the rapid expansion can cause rapid cooling and the production of hydrates, which can drastically impede injectivity.
Conventional CFD reservoir simulator codes have been designed with a primary purpose in mind of simulating high pressure behaviour of heavy oils, and using them to simulate CO2 injection under low pressure conditions is to push the boundaries of their design specification. Working with colleagues at Durham University, CMG (Computer Modeling Group), and Centrica, we investigated the effectiveness of current industry-standard Equation of State Modeling code to handle such settings, as well as worked on the development of an analytical model.
Understanding the nature of the deep crustal structure is important for the constraint of heat and mantle flow models. The iSIMM (integrated Imaging and Modelling of Margins) project is a major Earth Sciences research project funded jointly by government and the petroleum industry. The primary collaborators in the project were the Universities of Cambridge and Liverpool, along with Badleys and Schlumberger Cambridge Research. It was part of the NERC/DTI Ocean Margins (Link) Programme and ran from 1st October 2001 until 30th September 2005, however work has continued to be published based on the data recorded, including in Nature (March, 2008). The primary aim of iSIMM is to develop a new quantitative model for the development of rifted continental margins, supported by the acquisition of new seismic data from the UK Atlantic margin targeted specifically to address this objective. A secondary aim was to investigate seismic survey source design as a means to optimise the potential for imaging through basalt.
As a PhD student and subsequently as a post-doc on the project, I was responsible for the development of a full crustal P-wave velocity model for a 375km 2D seismic line across the Continent-Ocean Transition near to the Faroe Islands, and combining information obtained from this with that from a 12 km co-linear Q Streamer line shot by WesternGeco, build new understanding as to the nature of high velocity material at the base of the crust near the transition, as well as the volume of extruded and intruded melt and the processes involved in mantle upwelling in the vicinity of the Iceland hot spot around the time of continental breakup. Results were published in Geophysical Journal International, 2009.
Geophysics, 2016
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