No abstract

A technique is developed for a North Sea chalk reservoir to estimate the Hatchell-RØste R factors using a reservoir engineering constraint. This provides a way of defining the uncertainty on the R values, given the range of mechanical properties for the field of interest. In our case study the average R for the reservoir and overburden appears to be in the range 7 to 22. R factors are also calculated for regions of pressure relaxation and drawdown identified in the field, and the results confirm the current understanding determined by laboratory experiment and previous studies that the magnitude varies as a function of strain polarity, with the asymmetry being at most a factor of three. These results are validated with full geomechanical modelling followed by time shift modelling, showing that the observed time shifts cannot be created unless this asymmetry is present 30 May -2 June 2016 | Reed Messe Wien

No abstract

A high resolution, time lapse seismic inversion into pressure and saturation changes is performed. This provides insights into well performance and pressure distribution within a geo-mechanically active chalk reservoir (Ekofisk). The inversion is constrained by reservoir engineering concepts and predictions to reduce the non-uniqueness involved, and to maintain consistency with the physics of flow. At the heart of this inversion scheme is the effective union of engineering data and different seismic products such as reservoir time strain, percentage changes in elastic properties to influence the inversion. Quantitative interpretation on this field using the inversion results shows good agreement with well production data and helps to explain strong localised anomalies in both the Ekofisk and Tor formations. Analysis shows that the hardening signals around producers are due to lack of pressure support and reservoir compaction; whereas softening signals are attributed to high pressure flooding around injectors.