ABSTRACT
The productivity index (PI) is one useful tool used in assessing well productivity in the oil industry. As the reservoir pressure declines during production, the decline in well productivity becomes inevitable following the depletion of the hydrocarbon in place. Hence, the well productivity index declines over time even as the strength of the predominant drive mechanism deteriorates and becomes less significant in hydrocarbon recovery. Production decline can also result from impairment of the formation and poor completion designs. Therefore, PI decline of wells draining a reservoir suggests reserve depletion while exceptions suggest formation damage for low PI wells. Consequently, the PI values should be compared to the well completion efficiency to know if the decline is normal or induced by formation damage. This study presents procedure for analyzing PI decline curves and its application to well surveillance. Different representative rate of decline curves and their respective critical times were developed for determining stimulation candidate for different sand exclusion types. The possible areas of application include ranking candidates for stimulation as well as predicting the critical time for stimulating wells in order to improve production in oil wells.
