Effect of gas cap and aquifer strength on optimal well location for thin-oil rim reservoirs

Many hydrocarbon reservoirs have an oil bearing zone, sandwiched between gas and water bearing zones. For these reservoirs, considerable studies are conducted to optimize the location of wells in the oil rim so as to maximize oil recovery. Few studies however have investigated the conditions under which wells could be located in either the gas cap or the water leg so as to also maximize oil recovery. This study investigates the effect of gas cap and aquifer sizes on oil recovery from a reservoir with a thin oil rim using a single well numerical reservoir simulator model. Sensitivity studies were conducted by varying gas cap size, aquifer size and well location, and analyzing their effect on oil recovery. The results indicated that for a reservoir with a large gas cap, it may be more favorable to place the horizontal well below the water-oil contact; for a reservoir with a small gas cap and large aquifer, it may be advantageous to place the horizontal well above the gas-oil contact. This study is significant since thin oil rims are especially prominent in the prolific gas province offshore the east coast of Trinidad, and maximizing oil recovery, the more valuable resource, has positive financial implications.