Time-Lapse Separation Of Fluid And Pressure Effects With An Arbitrary Fluid Mixing Law
F. Borges and M. Landrø
Event name: Fifth CO2 Geological Storage Workshop
Session: Session 2: Reservoir Management
Publication date: 21 November 2018
Info: Extended abstract, PDF ( 4.11Mb )
Time-lapse seismic is a tool widely used for reservoir management. A common challenge is to isolate the effect of pore pressure and saturation changes in the 4D signal. This is an obstacle not only for hydrocarbon reservoirs: CCS projects also demand monitoring, to ensure that the injected CO2 remains stored in the target interval and that there is no abnormal pore pressure build-up. The way fluids mix in the pore space has a significant impact on the effect of saturation changes in the 4D signal, and uncertainties in this mixing propagate into the estimations of pressure and fluid changes from time-lapse data. Homogeneous mixing is usually assumed to be a reasonable approximation of the fluid behavior. In this study, we will make no such assumption, but rather set the mixture law as a degree of freedom in an inversion scheme. We model different CO2 saturations and pore pressures, which we combine with a rock physics model to obtain different synthetic reflectivities and time-shifts. From these modeled seismic measurements, we try to recover the changes in the reservoir parameters. We compare the results obtained with our method against those under failed assumptions about the fluid mixture law.