Hydrocarbon Column Height Modelling for Prospect Resource Assessment. A new Innovative Approach

Pre-drill estimates of prospect resource volume are strongly dependent on the expected hydrocarbon (HC) column height - which is directly influenced by the depth and uncertainty range of the expected hydrocarbon-water contact. Hence, HC-contact depth modelling has far reaching impact on the predicted range and probability of success-case volumes, impacting both exploration and development organisations.

A valid trap in a migration fairway may be underfilled due to the presence of a leak point (e.g. thief sand) in the seal at a depth shallower than the ultimate spill point. A good geologic description of the top-seal with respect to the likelihood of such features is therefore critical to resource size prediction. Unfortunately, however, experience tells that such leak points may not be detectable on seismic data –ie they are ‘cryptic’.

This paper describes a novel application of Poisson distribution theory for the forward modelling of HC-water contacts, integrating trap geometry (from depth-area data) and a geologic description of the seal to yield a HC-contact probability vs depth series that can be used directly in standard Monte-Carlo prospect assessment tools.