Date

Group

Speakers

Summary

1-12

Evert Slob

Title: Obtaining linear system responses from recorded field fluctuations

Starting from the principle of reciprocity, it can be shown that the response, or Green's, function can be retrieved for a wide class of linear systems that are described either by scalar or vector fields. 
Relevant examples of such systems in exploration geophysics include the pore pressure in reservoirs or aquifers, propagation of electromagnetic and seismic waves, diffusive electromagnetic fields and coupled electromagnetic and elastic wave fields in dissipative porous media (the subsurface).
For sources of the field fluctuations that are confined to a closed surface around a lossless medium, the cross correlation of recorded fields at two receivers results in the medium response between these receivers. In contrast, for sources of the field fluctuations that are confined to a closed surface around a dissipative medium, additional sources must be distributed throughout the volume to compensate for the dissipation. For strongly dissipative media we propose multidimensional deconvolution as an alternative that does not require sources throughout the volume.
For both methods advantages and disadvantages for practical applications are given and illustrated with examples from seismic, GPR, diffusive electromagnetic fields and electroseismic fields.

1-19

S-Team

Jae

Title: Uncertainty analysis for the integration of seismic and CSEM data

Summary:

Geophysical inverse problems consist of three stages: the forward problem, optimization, and appraisal. We study the appraisal problem for
joint inversion of seismic and controlled source electro-magnetic (CSEM) data and utilize rock-physics models to integrate these two disparate
data sets. The appraisal problem is solved by adopting a Bayesian model and we model four representative sources of uncertainty. These
uncertainties are related to uncertainties in (1) seismic wave velocity, (2) electric conductivity, (3) seismic data, and (4) CSEM data. The resulting uncertainties are quantified by a posterior random sampling in the model space of porosity and water saturation of a marine one-dimensional structure. We study the relative contributions from the four individual sources of uncertainty by performing several statistical experiments. The uncertainty in the seismic wave velocity and electric conductivity plays a more significant role on the overall uncertainty variation than does the seismic and CSEM data noise. The numerical
simulations also show that the assessment of porosity is most affected by the uncertainty related to seismic wave velocity and the assessment of water saturation is by the uncertainty related to electric conductivity. These results suggest different ways of accomplishing the uncertainty reduction, depending on whether our interests focus on porosity or water saturation.

1-26

A-Team

Praj & Hossein

Title: 2D Shear Wave VSP Imaging in the Presence of Azimuthal Anisotropy in Rulison Field, Colorado

The reservoir zone in Rulison Field comprises of thin sands whose lateral extent, geometry and hence connectivity is not well understood. The acoustic impedance (Vp*density) contrast between the sandstone and the encasing shale and the sub-resolution thickness of sandstone does not allow them be detected by the P-wave sources. However, the shear impedance contrast (Vs* density) between the sand-shale interfaces is more thus giving a better chance for their detection using a shear wave VSP survey. In the presentation I would discuss how to image the subsurface using shear waves recorded by multilevel 3C geophones in a walkaway VSP survey shot with collocated orthogonal horizontal vibrators. The current work describes a 2D imaging exercise that can, eventually, be extended to a 3D workflow.

Title: Effect of anisotropy on long offset time-lapse seismic

How the maximum amplitude offset shifts as a result of reservoir changes? How the critical angle changes in a compacting reservoir? I will talk about my work on these problems.

2-2

I-team

http://sites.google.com/site/cwpiteam/

2-9

C-Team

Dave

Title: Structure-oriented semblance

Semblance is commonly used as a measure of alignment or coherence because it is an amplitude-independent measure of the similarity of sample values in a sequence or image. Semblance is typically computed along linear or planar trajectories of samples in some window of an image, giving all samples in the window equal weight and those outside the window zero weight. I instead compute semblance along image structure, which need not be linear or planar, using locally weighted sums that smoothly and seamlessly taper weights to zero. We might also tune weights in semblance computations for specific problems. For example, in velocity analysis we might assign higher weights to samples at farther offsets, thereby increasing resolution in velocity.

2-16

President day

2-23

S-Team

Xia(Rosie) Qin

Title: Monitoring the Subsurface with Quasi-Static Deformation

We are exploring a technology that is based on using low-frequency strain data to monitor changes in fluid saturation conditions in porous media. Laboratory experiments have shown that strain data can reveal changes in complex moduli, which are caused by hysteresis in meniscus movement (changes in surface tension, wettability) when a pore containing two fluids is stressed at very low frequencies (< 10 Hz). 

Tidal tilts have maximum amplitudes of less than ± 100 nano-radians. We resolve tilts down to 1 nano-radian (1 micron over 1 km). Long-term tilts (many months) resulting from the relaxation of the instrumented wells are on the order of 100 micro-radians, those from routine agricultural activities, such as nearby irrigation, are as large as ± 5 microns and an Earthquake in Alaska on November 3^rd, 2002 caused a permanent tilt offset of 1 micro-radian. The tidal tilt signals are hidden in this large background noise. Special care is taken in the removal of this background noise.

3-2

A-Team

Mamoru, Bharath, Yongxia

Title: Estimation of Shear-wave interval anisotropic attenuation coefficients from mode converted data

Title: Influence of lateral heterogeneity on P-wave velocity analysis for transversely isotropic media

Title: First-order ray tracing in VTI media

3-9

Spring break

3-16

I-Team

http://sites.google.com/site/cwpiteam/

3-23

C-Team

Andrzej Szymczak, Clement Fleury, Derek Parks

Title: A Categorical Approach to Contour, Split and Join Trees with Application to Airway Segmentation

Title: Review of an ultrasound experiment: application to geophysics?

Title: Test driven development

3-30

S-team

Roel Snieder

Title: How to give an excellent presentation?

4-7

Talk rehearsals

4-14

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