Substantiation of Direct Detection and Mapping of Fluid-saturated Fractured Reservoirs Using Reservoir-generated Scattered Waves
V. Leviant, I. Kvasov and I. Petrov
Event name: Saint Petersburg 2018
Session: Seismic Exploration Technologies
Publication date: 09 April 2018
Info: Extended abstract, PDF ( 1.16Mb )
Price: € 20
Methods to detect fluid-saturated fractured prospects are based on significant difference in position of maximum wave amplitudes: reflections in source region; scattered converted waves - in near field on offsets shorter than prospect depth; and scattered compressional waves - on longest offsets. Detecting scattered compressional waves under said conditions among reflections from acoustic boundaries is based on opposite character of AVO-curves for scattered and reflected waves. For waves scattered by fluid-saturated fractures, stacked amplitudes of far channels are always higher than of near channels when impedance abruptly changes to zero or to positive at bed top. Their ratio is greater than 1. For reflections from acoustic boundaries, stacked amplitudes from far channels usually are lower than from near channels, while ratio of their amplitude sums is always smaller than 1. Another method to identify compressional wave type from its AVO-curve gradient sign uses midlength source-receiver distances. Gradient sign should be positive for scattered wave and negative for reflection. Indicators to detect fluid-filled mesofracture zones from X-component data are based on: high relative strength of scattered converted waves in near field; differences in structure and strength of converted wavefield with polarity reversal on either receiver spread side; shift of zero on AVO-curve. These diagnostic indicators may effectively be complemented with summing no-phase-change recordings from either spreadside.