This paper discusses the Bayesian updating of the chances of hydrocarbon success in a sand cut by a fault when the sand is charged after fault time. Prior to actual drilling the decision to drill either the downthrown sand component or the upthrown sand component depends, in particular, on whether the fault is considered to be leaking a lot or a little and whether any leaked hydrocarbons are then trapped in the upthrown sand. Based on prior-to-drill estimates of parameters one can then determine which is the better probability to drill. After drilling one knows with certainty the worth obtained in one component of the fault cut sand. This information can then be used to update the probability that the fault is leaking a lot or only a little, as well as to change the assessment made prior to drilling concerning the probability that a hydrocarbon charge indeed took place in the lower sand after fault time. These updated parameter values can then be used to re-assess the location off the next drill site in order to improve the chances of commercial success. This group of problems is addressed in this paper with numerical examples to show how the procedures operate in practise.