Prediction of Residual Oil Saturation by Using the Ratio of Amplitude Attributes of Time-Lapse Seismic Data

Abstract

Subtraction of baseline and monitoring seismic data is a common step to highlight reservoir changes in time-lapse seismic interpretation. However, ambiguity exists in the interpretation of the amplitude difference, which is controlled by fluid change and reservoir thickness. To estimate residual oil saturation quantitatively, we propose a time-lapse seismic interpretation method that utilizes the ratio of amplitude attributes extracted from baseline and monitoring seismic data. The relationship between impedance change and the ratio of the baseline and monitoring amplitude attributes is determined to avoid the influence of reservoir thickness. Subsequently, the fluid saturation is calculated from the impedance change by using a proper petrophysical relationship based on time average equation. The new method is tested on a real time-lapse seismic dataset from a water-flooded reservoir in the deep-water area of West Africa. The water-flooded area determined from the amplitude difference does not completely match the production logs because of the influence of variations in reservoir thickness. However, the residual oil distribution calculated with the proposed method matches the production logs well. The connectivity of sandstone bodies is also evaluated based on an integrated interpretation of estimated oil saturation. With its simple principle and easy accessibility, the proposed method improves the accuracy of time-lapse seismic data interpretation in water-flooded oil reservoirs. Furthermore, the quantitative interpretation of fluid change enables the time-lapse seismic technology to guide reservoir development directly.

AAPG Datapages/Search and Discovery Article #90323 ©2018 AAPG Annual Convention and Exhibition, Salt Lake City, Utah, May 20-23, 2018