Decline Curve Analysis for Farrud Reservoir in Zenad Oil Field

Abstract

Decline curve analysis (DCA), in petroleum engineering, is a tool being used to do many calculations, for instance: to estimate original oil in place, to estimate ultimate oil reserve (EUR) at initial reservoir conditions, to estimate remaining oil reserves from certain time to the end of reservoir age (that to be at future reservoir abandonment pressure or economic production rate), to forecast future production rate at any desired time and predict the reservoir performance. The basis of decline curve analysis (DCA) is to match past production performance histories or trends (i.e., actual production rate/time data) with a “model” assuming that future production continues to follow the past trend. The decline-curve methods apply to individual wells or an entire reservoir. This project presents basic concepts and applications of decline curve analysis using OFM software. Well-testing data from ten producer-wells in the Farrud reservoir were collected and subjected to DCA calculations through OFM software. The results showed that, for the whole Farrud reservoir, the economic flow rate was about 300 STB/D of oil, the recoverable reserves at initial reservoir conditions (EUR) were 80.2 MMSTB oil, and the remaining reserves at the time of study were 19.96 MMSTB oil, with an expected abandonment date of November- 2058. The decline curve analysis for the entire field is more reliable than for the wells, and the remaining reserve for the entire reservoir is very close to the summation of the remaining reserves for the ten well producers. Finally, it is preferable to evaluate the reserves with other methods, such as the MBAL software or utilizing the Petrel software to conduct the reservoir simulation study, in order to ensure that the results that have been obtained are dependable.