Mariano Floricich

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.

Determination of a seismic and engineering consistent petro-elastic model for time-lapse seismic studies: Application to the Schiehallion Field

Summary A relationship between pressure and saturation changes in the reservoir and the corresponding time-lapse seismic signatures is determined from measurements of the produced fluids and downhole pressures at a number of wells. The results from this process also provide an insight into the governing parameters for the rock and fluid physics model which are then compared directly to conventional petro-elastic predictions. The methodology is applied to the Schiehallion field where it is found that the 4D responses to water replacing oil, and gas breakout, follow the predictions of Gassmann fairly accurately. However, the sensitivity of the seismic to increases in pressure is observed to be roughly half as strong as that estimated from standard core plug measurements.