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CWP Seminars - 2012 Fall

CWP seminars discuss topics pertaining to our broad areas of research interests. These seminars are led by CWP faculty, students and, on occasion, by guest presenters. CWP seminars are held every Monday at 4 p.m. in the Green Center on the Colorado School of Mines campus.

Note: To view weekly seminar schedules of individual CWP teams, click a link below:

A-Team seminars

C-Team seminars

iTeam seminars

Steam seminars

 

Fall 2012 CWP seminars

Date Speaker(s) Title Abstract
12/17 - 1/9/13

CSM Winter Break - no seminar

12/10

CSM final exams - no seminar

12/3

Pengfei

Pengfei Cai

Joint migration velocity analysis of PP- and PS-waves for VTI media

Combining PP-waves with mode-converted PS reflections in migration velocity analysis (MVA) can help build more accurate VTI (transversely isotropic with a vertical symmetry axis) velocity models. To avoid problems caused by the moveout asymmetry of PS-waves and take advantage of efficient MVA algorithms designed for pure modes, we suggest to generate pure SS-reflections from PP and PS data using the PP+PS=SS method. Then the residual moveout in both PP and SS common-image gathers is minimized during iterative velocity updates. The objective function also includes the differences between the migrated depths of the same reflectors on the PP and SS sections and a regularization term. The algorithm is first tested on several synthetic models and then applied to a 2D section from 3D OBS data acquired at Volve field in the North Sea.

11/26

Nori

Nori Nakata

Monitoring a building by applying deconvolution interferometry to ambient-noise data

Although deconvolution interferometry is a useful technique to monitor a building, most of studies are using earthquake data. In this study, I use ambient-noise data. By using noise data, I can obtain other information (velocity and attenuation) which I cannot estimate from earthquake data. I will show you the relationship of mathematics, numerical computation, and real-data analysis to estimate velocity and attenuation.

11/19

Natalya

Natalya Patrikeeva

Wide-azimuth angle gathers: theory and application to the Volve data

Natalya will present the theory of 3D angle gather construction, compare the main methods currently used to extract angle information and show some results with the real Ocean Bottom Seismic (OBS) data set.

11/12

TimKeho

CWP group

Highlights from the 2012 SEG annual meeting

The CWP group will highlight and present summaries of presentations/conversations relevant to CWP research from the 2012 SEG annual meeting.

11/5

CWP attending SEG Annual Meeting - no seminar

10/29

Yong

Yong Ma

Wave-equation reflection traveltime inversion with dynamic warping

In reflection seismology, full waveform inversion (FWI) can generate high-wavenumber subsurface velocity models but often suffers from an objective function with local minima caused mainly by the absence of low frequencies in seismograms. These local minima cause cycle skipping when the low-wavenumber component in the initial velocity model for FWI is far from the true model. To avoid cycle skipping, we propose a new wave-equation reflection traveltime inversion (WERTI) to update the low-wavenumber components of the velocity model, while using FWI to only update high-wavenumber details in the model. We implement the low- and high-wavenumber inversions in an alternating way.

In WERTI, we use dynamic image warping (DIW) to estimate the time shifts between recorded data and synthetic data. When compared with correlation-based techniques often used in traveltime inversion, DIW can avoid cycle skipping and thereby reduce errors in the estimated time shifts. The alternating combination of WERTI and FWI mitigates the velocity-depth ambiguity and can recover subsurface velocities using only high-frequency reflection data.

10/22

TimKeho

Timothy Keho, Aramco Services Company

Geophysical challenges in Saudi Arabia

Saudi Aramco engages in exploration and development of onshore oil and gas fields in the Arabian Peninsula, and offshore fields in the Arabian Gulf and the Red Sea. The key geophysical challenges are: 1) Near surface velocity estimation for complex arid land environments containing collapsed filled karsts, strong velocity inversions, outcropping refractors, severe topography including sand dunes, dry river beds, and basalt flows. Workflows and algorithms for redatuming or pre-stack depth migration using complex near surface models are required. 2) Reservoir characterization and monitoring of oil, gas, and CO2, for both carbonate and clastic reservoirs, and identification and characterization of faults and fracture fairways. 3) Velocity analysis and imaging in complex subsalt deep water environments. In addressing these challenges, solutions will be developed for 3D seismic data from conventional acquisition geometries as well as high channel single sensor surveys, simultaneous source, continuous recording, buried source and receiver data, and surveys which also include gravity and EM data.

10/15

CSM Fall Break - no seminar

10/8

Bharath

Bharath Shekar

Algorithms to orient multicomponent geophones

It is crucial to correctly orient multicomponent geophones in processing reflection data. I will discuss some of the algorithms that I developed for the same, as part of my summer internship work.

10/1

Ali

Allison Knaak

Antenna Theory: A tutorial and discussion

This tutorial and discussion will illustrate how antennae play a role in our daily lives from cell phones to wireless internet. You may be surprised to learn that antennae play an important role in geophysics. To understand a field created by an antenna, we must understand its emitted signal. I will present an overview of basic antenna theory and discuss some antennae-optimization techniques. I will connect these concepts throughout the presentation to current research and conclude by presenting my research in applying 3D aperture to controlled-source electromagnetics.

9/24

Francesco

Francesco Perrone

Wavefield tomography based on local image correlations: Application to real data and time-lapse seismic monitoring

Kinematic accuracy of migration models is conventionally measured using the semblance principle: because the Earth is time-invariant during a seismic acquisition, images obtained for different experiments (or different illumination angles) must locate reflectors at the depths. The semblance principle is implemented using conventional semblance or focusing measures. These methods analyze the migrated images at fixed lateral positions, build new images called Common-Image Gathers (CIGs) that are indexed by an extension parameter (subsurface offset, illumination angle, plane-wave parameter, shot number, etc.), and convert the moveout or defocusing in these images into model update. We restate semblance using image warping and relative shifts between images. This technique is based on local image correlations and allows us to consider small groups of images and all points in the migration domain at once. This strategy is the dual of conventional semblance methods where the entire survey must be analyzed and where the spatial domain is sampled to make the problem numerically treatable. In this presentation I briefly describe the technique and show the inversion results obtained for a real dataset. I also show a few preliminary tests for the application on time-lapse seismic monitoring where the apparent shift between a baseline and monitor survey image is inverted to recover the change in propagation velocity in the subsurface.

9/17

Xinming

Xinming Wu

Generating a seismic Wheeler volume by using a relative geologic time volume

A seismic Wheeler volume is an important tool for seismic stratigraphic interpretation to portray the geologic time-space distribution of strata and the related depositional, non-depositional and erosional events. It is also valuable for seismic geomorphological interpretation by facilitating the extraction of isochronal stratal slices. In complicated geologic settings (e.g., faults and unconformities), generation of a reasonable seismic Wheeler volume is difficult for the current seismic Wheeler volume generation methods. In this paper, we present a method to convert a seismic data volume from travel time-space domain into Wheeler domain via its corresponding a relative geologic time volume generated by phase unwrapping. Tests by model and real seismic data suggest that our method can effectively deal with complicated geological situations with faulting, folding and unconformities, resulting in a reasonable seismic Wheeler volume.

Stefan

Stefan Compton

3D nonlinear stack enhancement

Stacking is a key step in seismic data processing that also plays a large role in interpretation. Results of stacking pre stack gathers can be greatly enhanced by using a reference model as a coherence measure for noise attenuation. This 3D correlation based stacking approach allows an optimal mute to be designed for each gather prior to stacking. The result is the removal of unbalanced or coherent noise that may otherwise not be   removed by deconstructive interference from stacking.

9/10 CWP C-Team ----- -----
9/3 1st CWP seminar of the Fall 2012 semester (CWP administrative topics only)

 

 

 

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