Research

Linked-seismic and geomechanical modelling of petroleum reservoirs

The seismic properties of a rock-mass are controlled not only by the elasticity of the rock frame, but also by other factors such as pore-fluid properties, or stress- aligned microcracks. For a petroleum reservoir, many of these properties will change over time as a result of production. Much of my work at Bristol involves combining the output of coupled fluid-flow and geomechanical simulations with appropriate rock physics models to estimate aggregate dynamic-elastic properties. Such models can be used to predict how seismic observables (such as travel times, reflection amplitudes, or shear-wave splitting) will evolve in response to changes in stress or fluid properties, facilitating their use as diagnostic tools for reservoir monitoring.

Fracture characterization using seismic anisotropy

As many conventional gas reserves are being depleted there is an increasing interest in developing nonconventional “tight” gas reserves characterized by a very low permeability host-rock. Such reservoirs rely heavily on the presence of fractures to locally enhance permeability and increase production, thus a clear understanding of the natural fracture patterns is of crucial importance. One of the focuses or my current work is to use shear-wave splitting analysis of microseismicty data to detect and quantify seismic anisotropy within reservoirs. These data can then be coupled with effective medium models to invert for fracture system properties (e.g. mean fracture orientation and density). I am especially interested in the use of frequency dependent shear-wave splitting as a means to discriminate between microcrack- and fracture-induced anisotropy.

Seismotectonics of continental interiors

Although plate tectonics provides a clear explanation for the localization of the vast majority of worlds seismicity, earthquake activity within the “stable” continental interiors remains enigmatic. Our lack of understanding is in part caused by an incomplete record of long-term earthquake distribution. Consequently earthquakes often occur in unexpected locations where no historic seismicity has been observed. An improved understanding of the structural and stress controls on intraplate seismicity is necessary to adequately assess seismic hazard. I approached this problem in my PhD work, which focused on the Charlevoix seismic zone in Quebec. The region was chosen because it is a seismically active zone containing both continuous background seismicity, and large historic events, and contained relatively complex, but well understood structural features. I used geomechanical models to explore the possible structural controls in the distribution and partitioning of seismicity. Many of the patterns that I observed and explained in Charlevoix can also be observed in other seismically active regions, such as the eastern Tennessee seismic zone. Thus there is considerable scope to expand these ideas in order to better understand intraplate seismicity in general.