Abstract

Over the last decade, seismic inversion has acquired the status of being a routine interpretation step during exploration as well as development of fields. For detailed reservoir characterization, prestack inversion is desirable; however, poststack inversion is a reasonably effective tool. The inversion starts with calibration of the well with seismic data. The synthetic seismogram is tied with stacked seismic data on the basic premise that the seismic data (full stack) mimics the zero-offset data and therefore should match with the zero-offset synthetic seismogram. Generally, a good match is obtained. However, during the course of many inversion exercises, it is observed that the synthetic-to-seismic match is not good in parts of the drilled interval. There could be many reasons for this partial mismatch. One of the important reasons is that the well data represent one-dimensional data, whereas the seismic data are stacked over an angle range. In other words, the well data are equivalent to zero-offset data, whereas seismic is not. The poor calibration at the well location leads to lack of confidence in inversion results. The possible solution, such as simultaneous or full-waveform inversion, involves a lot of computation time and hardware requirements. An alternative approach is introduced which uses elastic impedance instead of normal P-impedance for synthetic match and inversion of stacked data. The synthetic seismic generated from elastic impedance shows an improved match with seismic data. The approach is quick, reliable, easy, and not heavy on computational resources. The result is inverted volumes with better hydrocarbon delineation and characterization ability.

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