Azimuthal Anisotropy at Valhall: the Helmholtz Equation Approach.

Aurélien Mordret, Nikolaı M. Shapiro, Satish Singh, Philippe Roux, Jean-Paul Montagner, Olav. I. Barkved.

Thursday 11 April 2013, by briandx // Publications

Azimuthal Anisotropy at Valhall: the Helmholtz Equation Approach.

Aurélien Mordret, Nikolaı M. Shapiro, Satish Singh, Philippe Roux, Jean-Paul Montagner, Olav. I. Barkved.

GEOPHYSICAL RESEARCH LETTERS.

Abstract

We used 6 hours of continuous vertical records from 2320 sensors of the
Valhall
Life of Fields Seismic
network to compute 2 690 040 cross-correlation
functions between the full set of sensor pair combinations. We applied the
’Helmholtz tomography’ approach combined with the ambient noise corre-
lation method to track the wave front across the network with every station
considered as a virtual source. The gradient of the interpolated phase travel
time gives us an estimate of the local phase speed and of the direction of wave
propagation. By combining the individual measurements for every station,
we estimated the distribution of Scholte’s wave phase speeds with respect
to azimuth. The observed cosine pattern indicates the presence of azimuthal
anisotropy. The elliptic shape of the fast anisotropy direction is consistent
with results of previous shear wave splitting studies and reflects the strong
seafloor subsidence due to the hydrocarbon reservoir depletion at depth and
is in good agreement with geomechanical modeling

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