Oil Reservoir Assessment Using Multicomponent Seismic Data
Chuandong (Richard) Xu
The multicomponent seismic method has been recognized as a useful tool to enhance the traditional P-wave seismic method for hydrocarbon exploration and exploitation. In this dissertation, a workflow of multicomponent seismic interpretation has been proposed. Using multicomponent seismic data, two oilfields (Ross Lake heavy-oil field in Canada and Cantarrel/Sihil carbonate oilfield in Mexico) are assessed. Checking the Vp-Vs relationship and other rock properties and carefully correlating synthetic seismograms, VSP (zero-offset and offset) and surface seismic data for both PP-wave and PS-wave are essential for interpreting multicomponent seismic data. In the Ross Lake heavy-oil field, a traveltime-derived Vp/Vs map clearly delineates the channel sand and shows a shale-plug in it which is supported by the result from the horizontal well. On the Vp/Vs map derived from impedance inversions of the poststack PP and PS data, the channel sand is also suggested by a low Vp/Vs anomaly but not as crispy as that of the traveltime-derived Vp/Vs map. In the Cantarell/Sihil carbonate oilfield, the PS data provide more continuous reflections in the areas where gas effects are visible in the P-wave sections (as noted elsewhere, especially in the North Sea), which may provide useful refinement of the structure. In addition, there may be fluid contacts visible in the upper reservoir. Several new structures are interpreted on the PS data. Vp/Vs values could be interpreted as showing shaliness or less consolidation in some areas.
An empirical Vp-Vs relationship has been established for deep-water siliceous shale using well data. Qp determined using spectral-ratio method from the zero-offset VSP in Ross Lake oilfield presents an inverse linear relationship with Vp/Vs derived from P-wave and S-wave source VSP, which may help to predict attenuation from Vp/Vs. An index for indicating the quality of Q estimation from VSP data has been proposed.