High pressure nitrogen injection is being considered as an enhanced oil recovery process for a naturally fractured thick carbonate reservoir containing light oil underlain by an infinite aquifer. The objective is to maintain reservoir pressure at such a level as to increase the ultimate oil recovery economically. In this paper, some of the pre-injection evaluation studies are described. (1). Slim tube displacement tests showed that injecting a small bank of produced C2-C6 hydrocarbon solvent ahead of nitrogen lowered the minimum miscibility pressure (MMP) from 5,300 psi to 3,500 psi, a reduction of about 34 percent. (2). Oil recovery experiments in one meter long, 10 millidarcy permeability homogeneous cores gave an increase of 15 percent in oil recovery at 1.2 pore volumes of nitrogen injection at 3,500 psi injection pressure if miscibility is achieved. (3). A small volume, single well nitrogen injection test in the field resulted in increase of the average daily oil rate by 3 m3 under miscible conditions.

You can access this article if you purchase or spend a download.