Determination of Recovery Factor in the Bakken Formation, Mountrail County, ND

Abstract

This paper was prepared for presentation at the 2009 SPE International Student Paper Contest at the SPE Annual Technical Conference and Exhibition. Abstract An accurate value for recovery factor in the Bakken shale is needed for estimation of ultimate recovery. Published estimates of recovery factor in the North Dakota region of the Bakken vary greatly and examination of historical production from this region reveals that very few published recovery factor estimates are accurate. In this paper, recovery factor for the Bakken shale in Mountrail County, ND, was determined using three different methods. The first method involved review of the literature and an examination of recovery factors historically used by companies operating in the area. The second method was based on material balance, while the third method was based on decline curve analysis. Results from all three methods were integrated and indicate that the most likely value for recovery factor in the Bakken shale is approximately 7%. In the absence of more definitive performance data, these results can be used by companies to estimate ultimate recovery and to help make investment and development decisions in the Bakken shale. Introduction The Bakken shale is not a new discovery, having originally been found to contain oil in the 1970s. Recently, thanks to a higher oil price and the introduction of new and effective well completion technologies, production in this area has increased dramatically. Fig. 1 shows the tremendous increase in production, which began in 2006 in Mountrail County, ND. Wells drilled in the Bakken shale come with a high price tag. The target formation is at a depth of approximately 10,000 ft and requires laterals of anywhere from 5000 - 10,000 ft in length. The formation is extremely tight and has a low matrix permeability of approximately 0.05 mD, with limited evidence of natural fractures. Fracture treatments are quite large, having anywhere from 6 to 18 stages and requiring several million pounds of sand. Only with high oil prices, lengthy laterals and huge fracture treatments can the Bakken formation produce oil economically.