Interpretation of well-log, VSP, seismic streamer, and OBS data at the White Rose oilfield, offshore Newfoundland
Jessica Maria Jaramillo Sarasty
The petrophysical analysis in this thesis is based on dipole sonic (Vp and Vs), density, gamma-ray, and porosity logs (density porosity and neutron porosity). In general, velocity increases as total porosity decreases. Vp/Vs decreases slightly when total porosity decreases. Vs shows a high correlation with porosity. In addition, we find that Castagna's "mudrock" relationship predicts Vs from Vp reasonably well in the clastic section. Better fits can be achieved by dividing the lithologies into formations. In general, Faust's relationship makes a fair prediction of Vs, although for a better fit with the well data, different constants are required from the original relationship. The results were encouraging (Jaramillo and Stewart, 2003).
A multi-offset-VSP dataset was acquired in Husky Energy's H-20 well in the White Rose field. This survey generated several outputs including corridor stacks and CDP mapping of PP and CCP mapping of PS data. The interpretation of these results shows that the best correlations are between the PS synthetic seismograms and the PS offset VSP data. PS images from these synthetic seismograms at the top of the Avalon Formation, show higher amplitude over the adjacent signals. Synthetic and field data indicated that converted-wave (PS) data might be useful in mapping the Avalon reservoir at White Rose (Jaramillo et al., 2002).
During the summer of 2002, an ocean-bottom seismometer test line was conducted over Husky Energy's L-08 well in the White Rose oilfield. For this survey, 21 seismometer/hydrophone ocean-bottom (OBS) instruments were used as receivers to record the data. An airgun was used as the seismic source. The correlation between the PP and PS synthetics from well L-08 and the OBS data (vertical and radial components) gave confidence to the interpretation of the resultant PP and PS seismic sections. After matching both radial and vertical component seismic sections, the events on both sections became correlated. The Vp/Vs values obtained from the seismic are related to the values from well L-08. There are some Vp/Vs anomalies going laterally on the seismic sections. In general, the values decrease with depth (Jaramillo and Stewart, 2004).