A stratigraphic elastic inversion scheme has been applied to a data set from the Troll East Field, offshore Norway. The objective of the present work is to obtain estimates of the P- and S-wave velocities and densities of the subsurface. The inversion is carried out on τ - p transformed common depth-point (CMP) gathers.
The forward modeling is performed by convolving a wavelet with the reflectivity that includes water-bottom multiples, transmission effects, and absorption and array effects. A damped Gauss-Newton algorithm is used to minimize a least-squares misfit function.
Inversion results show good correlation between the estimated VP/VS ratios and the lithologies in the wells. The VP/VS ratio is estimated to 2.1–3.0 for shale and 1.6–2.0 for sandstones. In the reservoir, the VP/VS ratio is estimated to 1.55 in the gas sand and to 1.62 below the fluid contact.