Velocity Analysis for Depth Conversion: A Case Study of Block A, Baga/Lake Sub-basin in the Borno Basin, Northeastern Nigeria
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Date
2021
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Department of Geology School of Physical Sciences, Federal University of Technology, Minna
Abstract
Time-depth conversion analysis of time-migrated seismic images was undertaken on Block A, Baga/Lake sub-basin of Borno basin Nigeria, to predict the appropriate velocity model suitable for depth conversion away from six existing well control points. Three velocity models were used for the time-to-depth conversion including the average velocity-time analytical function, 2nd Order Polynomial time-depth analytical function, and instantaneous velocity analytical function. The velocity models were tested with the shallow and deep horizons representing the tops of Kerri-Kerri and Gongila Formations penetrated by six wells fairly spread on the 3,891 km? of 3D seismic data. The results show that each model has a variable degree of accuracy after depth conversion at the two formation tops. The average velocity-time analytical technique appeared as the best technique for the time-depth conversion having errors in the range of -0,12 to 145 meters at shallow and deeper formations respectively. The 2nd-order polynomial time-depth analytical function and Vo-K techniques gave a depth uncertainty greater than 135 meters at the shallow formation and over 1,000 meters at the deeper formation. The maximum percentage error recorded for both formations using the average velocity technique was 0.48% this is less than 5% and considered good in the practical situation, it is therefore recommended to be used for velocity modeling and depth conversion study in the Baga/Lake sub-basin of Borno Basin, Northeastern Nigeria.
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Seismic Image, Depth Conversion, Velocity Analysis, Borno Basin, Chad Basin., Research Subject Categories::NATURAL SCIENCES