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A new seismic technique, the DIVA (Differential Interformational Velocity Analysis) (trademark, Copyright Zenith Exploration Co., patents pending), which makes use of ultra refined seismic velocity analysis has been developed to identify and localize low velocity anomalies in the subsurface. Reservoir quality porous rock formations will always be distinguished by reduced seismic velocities whether or not hydrocarbons are present. In favorable settings, however, low velocities correlate well with hydrocarbon reservoirs. Where gas is present, the velocity reductions can be spectacular making the DIVA display an indicator with as much visual impact as the "bright spot" offshore. Color acoustic impedance sections further corroborate the reality of DIVA detection anomalies and assist in localizing them in reflection time. In addition, the color display, which in fact represents the essential information content of the seismic amplitudes, though very imprecise, is a vital monitor of the detailed changes in lithology. Fourteen wells to date have tested the concept ranging in depths from 7,00 to 15,000 ft (2,133 to 4,572 m) and targeting both carbonate and sandstone reservoirs. Several of these results are reviewed to illustrate the power of the approach. The technology has not only been proven by the drill but has also initiated new and exciting exploration plays which can not even be detected with usual seismic approaches. An east Texas reef bank sequence illustrates such a circumstance.
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