The Integration of Core and Pressure Transient Data for Reliable Reservoir Characterization

The pressure transient analysis is a reliable method to acquire average permeability around the wellbore. It can also be used to explore reservoir heterogeneity but this may lead to non-unique solutions. This problem is due to the nature of well-test, which could provide only one property combination function called heterogeneity function (Levitan and Crawford, 2002). Therefore, to infer individual properties one has to use additional information from other sources.In this paper, heterogeneity function is used to demonstrate the impact of uncertainty in porosity-permeability relationship on non-unique solutions. As such we consider a reference reservoir where porosity-permeability correlation and their distributions are known then heterogeneity function can be calculated. Using this function and assuming several scenarios for the relationship, multiple porosity-permeability distributions can be generated for the subject reservoir. Such solutions are generated for two different radially heterogeneous reservoirs and in each case the non-uniqueness of solutions is confirmed by constructing numerical pressure transient models and comparing responses. In addition, it is shown that unique solution can only be obtained, if the porosity-permeability relationship holds for both the reference and the subject reservoir. Therefore, incorporating a core porosity-permeability correlation in pressure transient analysis may weed out redundant non-unique solutions.