Investigation of Diffusivity Coefficient of Asmari Reservoirs by Well Test Analysis

One of the dimensionless reservoir parameter which can be used to characterize reservoir formation is the diffusivity coefficient. Diffusivity coefficient is a ratio of medium's capacity for transmissibility of fluid to its capacity for storing or releasing fluid. Diffusivity provides a quantitative measure for the rate of response during transient fluid flow. It is a parameter that is derived from the analysis of well test data. The objective of this work was to determine diffusivity coefficient for the Asmari sedimentary layer in an Iranian Southern oil field achieve this objective. Initially all available information such as petrophysical data, PVT data, production and pressure buildup data of the completed wells in Asmari formation were collected. Twenty one buildup tests data were analyzed by using Pan System Software using appropriate model for each well to estimate the parameters such as permeability, Skin factor, wellbore storage, average reservoir pressure and so on. A correlation between productivity index and the diffusivity coefficient for the Asmari formation has been obtained. The proposed correlation is very useful for determination of reservoir permeability for the situations where enough well tests data are not available.