Since its introduction in the early 1950s numerical reservoir simulation has become the mainstay of reservoir engineering practice. Indeed no major asset anywhere in the world has not been simulated, sometimes many times. Such preponderance of usage obscures the fact that there remains a place for simpler models.
This presentation gives a brief review of the use of models in reservoir engineering. It then reviews the use of simple (nonsimulation) models in current practice. The latter falls into the category of “cogent” models (Bratvold and Bickel) that allow the execution of multiple simulations and thereby enables decision-making.