P-wave velocity alone cannot always distinguish between different lithologies. In this example from onshore Libya, cross-plotting Vp with Vs aids the discrimination of reservoir from non-reservoir. (Hanitch et al, 2006)
P and S waves provide complementary information about the rock matrix properties, pore fluids and pressures. From early laboratory rock physics studies to recent seismic surveys, the combined use of P- and S-wave data help in discriminating lithology.
Seismic inversion provides estimates of rock properties used to identify lithologies and fluids. P-wave data alone require the use of long offsets and AVO techniques to derive S-wave impedances and velocities. Joint PP and PS inversion provides S-wave properties directly and hence better fluid and lithology identification than either one alone.
Use of multicomponent data can help discriminate between:
Sand, shale, carbonates and volcanics
Fluid, temperature and pressure changes during production
Gas and lithology bright spots
Multicomponent & Heavy Oil
Heavy oil reservoirs can be found around the world, including Canada, Venezuela, China and Russia. Advances in technology are opening access to hydrocarbons once thought uneconomic to produce.
Multicomponent data have several applications in heavy oil developments, such as:
Identification of shale volume through better density estimation
Tracking temperature changes in 4D surveys
Identifying local variations in anisotropy
Shale volume is a particularly important parameter for the heavy oil recovery processes because shale units act as barriers or baffles to steam movement. Multicomponent data can be used to plan well locations more effectively, leading to a higher recovery factor.
CGGVeritas recently processed these multicomponent data from a heavy oil survey
in Alberta, Canada. The primary objective was to obtain an improved understanding
of the reservoir via joint interpretation of the PP and PS images. Note how the
reservoir interval is almost transparent on the PP data (left) yet shows clear internal structure on the PS image (right).
