Publications

Following initiation of peripheral waterflood injection in 1997, oil production peaked at BK field in 2002. It is clear that water injection successfully improved oil production in the up-structure producing wells. However, it also isolated oil down-structure below the peripheral water injectors. Isolated oil accumulation down-structure in the east-southeast (ESE) flank was proven with the unexpected result of appraisal well #166 with initial production 320 BOPD and 65% water cut from a single X sand reservoir in 2011. That result was followed by four successful directional infill wells in 2012 with initial production ranges from 50 to 251 BOPD and water-cut ranges from 84 to 91%. This unique production discovery raises the question of the existence of an oil trap in the ESE flank structure so close to original oil-water-contact despite primary recovery showing that the oil-water-contact already moved-up above the peripheral injectors in 1997 due to the strong water-drive reservoir. Recoverable oil down-structure in the ESE flank is not because of structural or stratigraphic compartmentalization but rather due to isolation of oil as a local result of peripheral water injection. Borehole image data from a directional infill well shows no fault indication as indicated in 3-D seismic cube. Reservoir pressure data in X Sand shows high pressure ranges from 420 to 750 psi up from initial pressure of 200 psi which indicates reservoir connectivity to the peripheral injectors. Well-to-well correlation shows flexure oil-water-contact with draping oil pay thickness ranges from 15 to 20 feet. Discovery of the flexure oil trapped below the peripheral water injection level BK has led to the conclusion that classic piston-like waterflood displacement might not be a suitable approach since the calculated Dietz flood front angle approximation is –1.57 degree (< 0 degree). Gravity force with strong water-drive mechanism and low structure angle (1 to 3 degree) in the ESE flank are much stronger influences as compared either to mobility contrast or to rock heterogeneity that made the flexure oil trap in X Sand. Therefore, injector placement strategy and injector to producer alignment prioritization are critical factors for maximizing and improving oil recovery in the flank structure.