Post-Mortem Analysis of Exploration Results: A Model-Based Approach

Hall, David M.¹, Annick Richard¹, Eric Denelle¹, Pierre Delfiner² (1) Total S.A, Paris, France (2) Total E&P, Paris La Defense Cedex, France

Since the creation of the new Group in 2000, Total has carried out post-mortem analy­ses of over 300 exploration objectives from a the world-wide drilling programme of more than 200 wells located in a variety of geological basins.

Using the in-house post-mortem method, the outcome of each exploration objective is compared with the key elements of the predicted geological model namely; source rock; tim-ing/migration, reservoir, seal, trap geometry, fluid type and in-place hydrocarbon volumes.

The overall outcome is then assessed as being either compliant (agreeing with the pre­dicted model) or non-compliant (disagreeing with the predicted model).

The compliance rate (compliant / non-compliant ratio) provides a convenient way of evaluating the success rate of geological predictions, independent of economically-influ-enced considerations such as recovery factor and non-economic cut-off volumes. The com­pliance rate differs from the discovery rate (presence of movable hydrocarbons) which, by definition, is always higher.

Post-mortem analysis is an essential part of the exploration cycle. Firstly, lessons learnt help reduce the bias of pre-drill estimates and also help recognise the limits of predictive ability. Secondly, this knowledge is shared on a company-wide basis thus improving the coherency of prospect evaluations between different project teams. As a consequence, cen­tralised portfolio management is also improved.