A feasibility study of timelapse seismic monitoring using stochastic reservoir models

1999 Society of Exploration Geophysicists. All rights reserved. Time-lapse seismic monitoring of producing reservoirs presents strong potential for improving reservoir management. We have implemented a high speed simulation combing streamline fluid flow and ray-Born seismic modeling to examine feasibility and uncertainty of such monitoring. The simulations is applied to an 80% gas saturated reservoir model subjected to water injection by building a realistic porosity model using stochastic methods and generate a permeability model using cloud transforms. We then apply a rapid streamline fluid simulation. The petrophysical and fluid saturation data provide the basis for predicting time-dependent elastic properties of the reservoir using the Gassmann equation. Bulk moduli for the solid grains and fluid properties were chosen to represent reservoir conditions at a depth of 2km, and dry rock bulk and shear moduli were chosen to have a linear dependence on porosity similar to observations from laboratory data. Given the parameters from the Gassmann equation, a ray-Born algorithm provides a high speed, 3-D simulation of seismic data. We find that the RMS amplitude change before and after water injection is large enough to be seismically visible in the high porosity regions of the reservoir, but the change in low porosity regions is small and may be masked if the signal-to-noise ratio is small. Other factors such as seismic resolution will also hinder time-lapse analysis.

A feasibility study of timelapse seismic monitoring using stochastic reservoir models Conference Paper