We developed a method for quantification of uncertainties on spatial
data acquired at points with uncertain location coordinates. We applied
it to well-log data from wells with uncertain trajectories. The method
is fully probabilistic and requires few a priori assumptions on the
Earth model and the wellbore geometry. We performed simulations of well
trace and well-logging showing how the total uncertainty of well-log
data vary according to the variability of subsurface properties, and how
the reliability of well-log interpretations close to layer boundaries
may be compromised.