A stratigraphic elastic inversion scheme has been applied to a data se
t from the Troll East Field, offshore Norway The objective of the pres
ent work is to obtain estimates of the P- and S-wave velocities and de
nsities of the subsurface. The inversion is carried out on tau - p tra
nsformed common depth-point (CMP) gathers. The forward modeling is per
formed by convolving a wavelet with the reflectivity that includes wat
er-bottom multiples, transmission effects, and absorption and array ef
fects. A damped Gauss-Newton algorithm is used to minimize a least-squ
ares misfit function. Inversion results show good correlation between
the estimated V-P/V-S 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 V-P/V-S ratio is estimated to 1.55 in the gas s
and and to 1.62 below fluid contact.