Towards a successful time-lapse survey
Now that we have worked through enough background, and with the experience also of looking at several case histories, we are ready for a summary session on "how to do it" and some final points and "lessons learned."
(A) Work the rock physics. Establish the link between reservoir properties and seismic observables using logs, core and fluid data, plus VSP data if available.
(B) Work the reservoir simulator. Determine the changes we would expect due to production–the new fluid distributions and pressure changes.
(C) Work the seismic modelling to predict the changes in the seismic observables. Generate synthetic seismic data and assess the magnitude and character of the changes that might be visible. Assess the need for any special processing or seismic attribute studies. Study the resolution.
(D) Work the economics to estimate where and how the time-lapse data adds value.
(E) Design the baseline seismic survey (or the repeat).
(F) Work the earlier or later seismic data–it may be possible to extract more from it.
(G) Interpretation and modelling of time-lapse seismic relies on good well matching and wavelet extraction. If this is not possible, the error bars on the interpretation will be much larger.
(H) If there is no base reservoir or OWC event, then events below the reservoir may still allow a good indication of change via observable time delays.
(I) Manage the expectations. Results are more likely to be qualitative than quantitative. Don't over-hype.
(A) Rock Physics–Some key factors: Pore fluid affects the overall compressibility
Figures & Tables
“This book, prepared for use with the first SEG / EAGE Distinguished Instructor Short Course, discusses Â"time-lapse seismicÂ" and enables geoscientists to assess the value and risk of this new technology. It covers the rationale and driving forces behind time-lapse seismic by examining the limitations of existing methods of tracking fluid flow between wells. It examines those reservoir properties that change with time and what can be observed on seismic data over elapsed time. The repeatability of seismic data and the use of Â"legacyÂ" data sets are discussed, along with a review of the seismic data acquisition schemes and data processing requirements for time-lapse analysis. The rock-physics foundation for data analysis and interpretation options also are described. A selection of industry case histories illustrates many of these points. The reader will gain an understanding of key success factors, key calibration requirements, and key uncertainties of time-lapse seismic in reservoir management.”