Appraisal of complex reservoirs with short-time tests

The utility of short-time tests to obtain the description of a reservoir with complex geology is evaluated. Using a porosity cube that is representative of the Brent reservoir in the North Sea, a series of independent tests is simulated and results are evaluated as a function of depth. The characteristics of the signatures are documented. An understanding of these signatures is particularly useful in that the overwhelming majority of the signatures is quite different from what we expect in REV-type models.Over 170 independent tests as a function of depth are evaluated, the permeability profile is computed and compared with the in situ profile and conclusions are derived. The conclusions that may be derived depend on the specifics of the model used to evaluate the pressure response. The fact that the estimation of permeability is a function of scale is recognized and attention is drawn to the fact that, if properly analyzed, such tests must reflect scale dependency.Permeability estimates of short-time tests essentially yield values of permeability in the immediate vicinity of the perforation; thus, it is best to use data that represent local values to calibrate a model that reflects the underlying geology. Conventional interpretations will yield conservative estimates of well deliverability unless careful calibration is done with a model that carries the geological imprint.