Using multicomponent seismic data to delineate hydrocarbon reservoirs: 2D-3C Willesden Green, Alberta and 3D-3C Manitou Lake, Saskatchewan
Roxana Maria Varga
Multicomponent seismic analysis can be a powerful tool for reservoir delineation. Analyzing both compressional (PP) and converted (PS) wavefields can provide detailed information about lithologies, fluid saturation and subsurface structures. Two projects are considered in this thesis: a 2D-3C (two dimensional seismic survey recorded on three component geophones) project from Willesden Green, Alberta and the 3D-3C (three dimensional seismic survey recorded on three component geophones) project from Manitou Lake, Saskatchewan. The Upper Cretaceous (Turonian) Second White Speckled Shale (2WS) is the zone of interest at Willesden Green. PP and PS synthetic seismograms generated from borehole logs correlate well with the surface seismic data. Post-stack PP and PS inversion was applied to the vertical and radial components to yield P and S impedances. Vp/Vs estimates (from horizon correlations after registration) show anomalous values around 1.6 to 1.8 in zones of interest around the producing wells. This result was helpful for sand/shale discrimination, considering that shale's Vp/Vs values are usually higher than 1.9. Lower Cretaceous fluvial sand channels with high porosity and permeability in the Manitou Lake area of Saskatchewan contain important oil and gas reserves. The goal here is to use 3C-3D seismic data to differentiate sand versus shale and find hydrocarbon- filled porosity. Well logs and synthetic seismograms are used to correlate the PP and PS seismic sections from the 3C-3D seismic survey, to better delineate the Colony and Sparky reservoir sands. Detailed registration of multicomponent seismic data aims to reduce the uncertainty of traditional channel interpretation and improve well targeting. Mode-converted (PS) seismic amplitudes complement traditional PP channel interpretations. PP and PS amplitude maps show different aspects of the Sparky and Colony sand channels. Curvature co-rendered with the PP/PS amplitude envelope or curvature co-rendered with coherence can better delineate the edges of the channels, providing information about the top and bottom of the reservoir. Seismic attributes such as AVO, fluid factor, LMR (lambda-mu-rho), and joint inversion methods provide additional information. The simultaneous inversion method followed by Vp/Vs maps can complement the information for drilled wells and give confidence in identifying new drilling locations. Vp/Vs values less than 2.15, from PP and PS maps (registered in PP time), correlate with productive zones.