Pore-pressure prediction derived by common-reflection-surface (CRS) stacking seismic velocity to prevent drilling problems in geopressure zones: a case study of Snapper Field, Gippsland Basin, Australia

Abstract

Snapper Field is located in the Gippsland Basin, Australia. The field was discovered in 1968, and then continued by development drilling from the Snapper A platform, which started in 1981. The geopressure zones were encountered below 3,200 m at the Snapper—1 well and below 2,800 m at the Snapper A—21 well. If these zones are not anticipated before drilling, they could create problems, such as sticking, kick, or blowout. This extended abstract presents a technique to predict pore pressure from seismic velocity, where the seismic velocity was derived by CRS. Many case studies have shown that CRS stack could produce smooth macro-velocity model, which is more reliable to be used for pore pressure prediction. Eaton's equation was used to transform the seismic velocity derived by CRS to pore pressure as a function of depth. All of these workflows have been conducted using field data from the Snapper Field provided by the Victorian Department of Primary Industries. The prediction was compared with actual well pressure data to test the accuracy of prediction. The comparison shows that the pressure, which has been generated using this technique, is accurate. This result could be applied when making drilling programs particularly to identify the geo-pressure zones for wildcat/exploration wells in another field when pressure data from neighbouring wells are unavailable. If these geo-pressure zones could be anticipated, it will reduce drilling risk operation.