Deriving effects of pressure depletion on elastic framework moduli from sonic logs     

Anne-Kari Furre  Mona Andersen  Anita Smalø Moen  Randi Kristin Tønnessen 《Geophysical Prospecting》2009,57(3):427-437

We have developed a method to determine the effect of pore pressure depletion on elastic framework moduli, by utilizing sonic logs from wells drilled at different locations through a reservoir at varying depletion stages. This is done by first inverting the sonic logs for elastic framework bulk and shear moduli, thus carefully removing pressure dependent fluid effects. By crossplotting these elastic framework moduli against an increase in net stress (which is directly related to depletion), we derive the stress sensitivity of the elastic framework moduli. We found that the observed stress sensitivity was consistent with time-lapse seismic results and that the sensitivity derived from the sonic logs was much smaller than predicted by hydrostatic measurements on core samples. This method is applicable to depletion scenarios in mature fields and can be used both for modelling and inverting time-lapse seismic data for effects of pore pressure depletion on seismic data.  相似文献   

Dual sensor streamer technology used in Sleipner CO2 injection monitoring     

Anne‐Kari Furre  Ola Eiken 《Geophysical Prospecting》2014,62(5):1075-1088

CO₂ has been injected into the saline aquifer Utsira Fm at the Sleipner field since 1996. In order to monitor the movement of the CO₂ in the sub‐surface, the seventh seismic monitor survey was acquired in 2010, with dual sensor streamers which enabled optimal towing depths compared to previous surveys. We here report both on the time‐lapse observations and on the improved resolution compared to the conventional streamer surveys. This study shows that the CO₂ is still contained in the subsurface, with no indications of leakage. The time‐lapse repeatability of the dual sensor streamer data versus conventional data is sufficient for interpreting the time‐lapse effects of the CO₂ at Sleipner, and the higher resolution of the 2010 survey has enabled a refinement of the interpretation of nine CO₂ saturated layers with improved thickness estimates of the layers. In particular we have estimated the thickness of the uppermost CO₂ layer based on an analysis of amplitude strength together with time‐separation of top and base of this layer and found the maximum thickness to be 11 m. This refined interpretation gives a good base line for future time‐lapse surveys at the Sleipner CO₂ injection site.  相似文献