Pore pressure prediction using multicomponent PS-wave seismic velocities : Columbus Basin, Trinidad W. I.

dc.contributor.advisorFerguson, Robert J., Ph. D.
dc.creatorKumar, Kimberly Melissa, 1981-en
dc.description.abstractI estimate overpressure in a seismic cross-section along a 12km traverse associated with a 2D/4C OBC line in the Columbus Basin, Trinidad, West Indies, where shallow gas reduces both data quality and apparent seismic velocity for P-waves, using a modified Eaton's equation for PS-waves. Pore pressure prediction using the modified Eaton's method involves velocity analysis, conversion of the stacking velocities to interval velocities via the Dix's equation, converting the interval velocity trends to pressures and mudweights, and comparison of the predictions to 3 wells surrounding the seismic line. In the presence of shallow gas, the magnitude and areal extent of seismically derived P-wave and PS-wave velocity deviates from regional trends along the seismic line. PS-waves show a more accurate areal extent of velocity deviation due to overpressure than the P-wave, which is also affected by the presence of shallow gas. I verify my derived velocities and predicted-pressure values using sonic log data and observed pressure from 3 wells. Direct comparison between the sonic-derived velocities and the seismic-derived velocities shows that shallow gas reduces P-wave velocity, and that PS-wave velocity is less affected. Pressure prediction is verified using mudweights and formation tests from well logs and drilling reports. I find pressure predictions associated with P-waves, especially in areas of shallow gas are less reliable than for pressure predictions using PS-waves. I conclude that PS-wave velocity provides a superior map of overpressure in this region in areas with shallow gas clouds.en
dc.description.departmentEarth and Planetary Sciencesen
dc.rightsCopyright is held by the author. Presentation of this material on the Libraries' web site by University Libraries, The University of Texas at Austin was made possible under a limited license grant from the author who has retained all copyrights in the works.en
dc.subjectPore pressure predictionen
dc.subjectNatural gasen
dc.subjectNatural gas explorationen
dc.titlePore pressure prediction using multicomponent PS-wave seismic velocities : Columbus Basin, Trinidad W. I.en
thesis.degree.departmentGeological Sciencesen
thesis.degree.disciplineGeological Sciencesen
thesis.degree.grantorThe University of Texas at Austinen
thesis.degree.nameMaster of Scienceen

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