10.Direct Hydrocarbon Indicators

10.Direct Hydrocarbon Indicators - 10. Direct Hydrocarbon...

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Unformatted text preview: 10. Direct Hydrocarbon Indicators Kurt J. Marfurt CPSGG The University of Oklahoma Petroleum Geology and Geophysics 10-1 Learner Objectives After this section, you will be able to: Given appropriate impedances of a target sand reservoir and background shale matrix, be able to predict the presence of DHIs Recognize bright spots, flat spots, and phase reversals on seismic amplitude data Correlate DHIs to structural control 10-2 10-3 Gas sand, water sand and shale acoustic impedances all increase with depth and age but at different rates. The crossover points define whether the hydrocarbon indication is bright spot, phase change (polarity reversal) or dim spot. The principal effect of overpressure moves the shale line to lower impedance, thus increasing the effect of dim spots and decreasing the effect of bright spots. (Brown, 2011) A Gulf of Mexico bright spot and flat spot from the early 1970s. (Brown, 2011). Seismic processing must be amplitude friendly. (Brown, 2011) Time (s) 10-4 B r ig h t s p o t Flat spot (Gardner et al., 1974) 10-5 P-wave velocity sensitivity to gas vs. water or oil saturation of porous sands. Very sensitive Less sensitive Less sensitive Bright spot technology works very well in shallow, uncompacted sediments such as the Gulf of Mexico (Brown, 2011) 10-6 Seismic trough (negative reflection coefficient) Seismic pea (positive reflection coefficient) Zero-phase response of hydrocarbon reservoirs for different acoustic contrasts between the reservoir and the embedding medium (Brown, 2011) 10-7 magnitude of acoustic impedance changes between water-filled and hydrocarbon- filled sands and the resulting direct hydrocarbon indicators (DHIs) (Brown, 2011) 10-8 B r ig h t s p o t Flat spot B r ig h t s p o t Flat spot Bright and flat reflections from a Gulf of Mexico gas reservoir known to be subdivided into upper and lower sand units Map of bright spot (Brown, 2011) 10-9 Gulf of Mexico data indicating bright spots on vertical and horizontal sections. (Brown, 2011)...
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This note was uploaded on 02/04/2012 for the course GPHY 3423 taught by Professor Marfurt during the Fall '11 term at The University of Oklahoma.

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10.Direct Hydrocarbon Indicators - 10. Direct Hydrocarbon...

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