A New Technique for Pressure - Saturation Separation from Time-Lapse Seismic - Schiehallion Case Study

A technique is shown for estimating pressure and three phase saturation changes from 4D seismic. The technique is a further development of a recently published method which does not require defined rock and fluid physics relationships. A multi-attribute approach is taken, in which 4D seismic attributes are linked (by relationships with a physically reasonable form) to production data, and an optimal combination of seismic attributes are then selected to perform a bayesian inversion separating pressure and saturations. The methodology is applied to the Schiehallion field in the West of Shetlands with encouraging results. It has highlighted saturation changes, previously hidden by the effect of pore pressure on the rock frame, which can be validated against production and tracer data. Additionally, it has shown areas where gas is coming out of solution that have been validated against information acquired in a recently drilled well.