Near-Surface Seismic Imaging of the Shallow Sediments of Galveston Bay, Texas and the Tullos Oilfield, Louisiana



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In this thesis, two studies were conducted using high-resolution seismic and sonar methods to image the near-surface of Galveston Bay, Texas and the Tullos oilfield in Northern Central of Louisiana. Seismic reflection and sonar surveys were carried out in Galveston Bay. Processing flows including a bandpass filter, spiking deconvolution, and migration were used to process the boomer data and chirp sonar data. Boomer data achieves penetration of more than 100 m and reflectors of Quaternary age are imaged. Chirp sonar data has higher frequency content and greater resolution of 6-10 cm but lower penetration of 25 m than boomer data. The morphology of Holocene sediments overlying the Trinity River valley is clearly imaged in the chirp sonar data. Single-channel data and multi-channel data with the boomer source show reasonable correlation. A 2C-2D seismic survey was performed in the Tullos oilfield with multi-component seismic techniques. The processing flow includes receiver statics, F-K filter, surface consistent deconvolution, velocity analysis and CCP brute stack. The PP processed image has good signal-to-noise ratio value of 8 with penetration more than 1500 m. Synthetic seismograms were generated using a 50 Hz Ricker wavelet and correlated with seismic data. The PP processed data matched the synthetic seismogram nicely, and the Carrizo sand at 440 m depth was interpreted. Based on the 2D seismic data from Tullos, three 3D seismic survey options were designed for the neighboring Selma oilfield to image the Wilcox Group. The orthogonal geometry shows better fold distribution for the PP survey, whereas the PS survey has fold stripes. Slant geometry with 45° between the shot lines and the receiver lines showed better fold distribution for the PS survey. This thesis shows that seismic and sonar data can provide useful images of the shallow sediments of Louisiana and coastal Texas. Multi-channel seismic data was used for the first time to image the subsurface of Galveston Bay. High-resolution seismic imaging in the Tullos and Selma oilfields could lead to major exploration improvements.



Sonar technology, Multi-channel data, Multi-component seismic, Converted-waves, 3D design