WP4

Seismological investigations of deformation and rheology

Coord.: C. Thomas (WWU) & J.M. Kendall (UBRIS) 

The 3 projects that compose this WP have in common the use of seismic anisotropy to indirectly study the deformation and the rheology in the Earth.

ESR11 . Anisotropy and structure of the D” region. Supervisors: C. Thomas (WWU). Secondments: Univ. Bristol & GMuG
Objectives: Objectives: Constrain the convective flow pattern and the rheology at the base of the lower mantle (D” layer) via a systematic search for reflectors from/within D” using recently developed array techniques and source- and receiver arrays. Interpretation of the amplitude, polarity, and frequency content of the reflections from different azimuths sampling one region through calculated reflectivity based on mineral physics constraints and geodynamical models.
Expected Results: Map of D” anisotropy and flow pattern for several regions and knowledge of influence of mantle convection on development of anisotropy. Constraints on D” mineralogy through detected anisotropy.

ESR13 . Development of seismic anisotropy in deforming salt bodies. Supervisors: J.Wookey (UBRIS). Secondments: Univ. Bristol & GMuG
Objectives: Objectives: The precise location of salt bodies by seismic methods is fundamental in petroleum exploration, as oil and gas accumulate below or along their flanks. Rocksalt has very different properties from surrounding sediments; it is generally higher in seismic velocity, lower in permeability and lower in density and viscosity, what leads to upward mobility in the form of sheets and diapirs. Flow results, however, in seismic anisotropy, which has to be considered in the treatment of the seismic data. The aim of this project is to develop multiscale models for predicting crystal preferred orientations produced by rocksalt deformation in sedimentary basins and the resulting seismic anisotropy.
Expected Results: Better seismic imaging of salt bodies, which often form oil and gas traps .

ESR14 . Seismic methods to estimate the strength of cracks and fractures. Supervisors: J.M. Kendall, J.P. Verdon (UBRIS). Secondments: UCL & Reykjavij Geothermal
Objectives: Objectives: Use of seismic anisotropy to monitor the evolution of cracks and fractures and the resulting secondary  porosity and fluid flow in reservoirs. The ESR will will develop methods for fracture characterisation using measurements of seismic anisotropy and attenuation and apply these methods for analysing recently collected microseismic datasets from two distinct settings: an oil reservoir where hydraulic fracture stimulation has been monitored; a naturally fractured geothermal reservoir on a deforming volcano, where microseismic events have been located and calibrated. A specific interest is in recently developed methods to estimate fracture compliance, which is a key indicator of permeability in these settings.
Expected Results: New methods for monitoring the spatial and temporal the evolution of cracks and fractures and its effect on the secondary porosity and fluid flow in reservoirs.

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