Volumetric and Material Balance Methods of Reserve Estimation: A Comparative Study using Niger Delta Reservoirs

Abstract

This paper investigated the estimations of reserve in place in four Niger Delta Reservoirs using both the Volumetric and Material Balance (MB) methods comparatively. The Volumetric estimations started from the planimeter readings while the MB method used plots from the Havelena and Odeh formats in its estimations. Reservoir “A” is a saturated oil reservoir, no water drive, and negligible rock and fluid compressibilities; Reservoir “B” is a saturated oil reservoir underwater drive at encroachment angle of 70o; Reservoir “C” is an undersaturated oil reservoir under solution gas drive, while Reservoir “D” is a gas reservoir without water influx. There were good to the very good correlation between the results obtained by both methods except in the case of “D” where an extension of the reservoir to another occurred and so the Volumetric method gave a value of 4.48MMMSCF as the value of gas in place while the MB method gave a value of 9.15MMMSCF. The MB method was recommended to give better accuracy though very cumbersome to evaluate.