Enhanced Oil Recovery by Nitrogen Injection: The Effect of Increased Temperature and the Amount of Gas in Solution

Abstract

ABSTRACT The results of laboratory research conducted to study displacement of crude oil by high-pressure nitrogen injection are presented in this paper. The objectives of this research were to study the effect of temperature and original gas-oil ratio in solution on crude oil recovery and the miscibility process in high-pressure (H-P) nitrogen injection. Also in addition, the effectiveness of nitrogen injection after waterflooding and the effect of nitrogen-driven propane slugs was examined. Nine experimental tests were performed using crude oil of 42.3° API recombined with natural gas. The experimental tests were made using two temperatures (70°F and 120°F) and three gas-oil ratios in solution (575 SCF/STB, 400 SCF/STB and 200 SCF/STB). The reservoir model used was a stainless steel tube 125 feet long and 0.435 inches in diameter, packed with sand consolidated to give an average permeability of 910 md. The model was provided with five sampling valves to collect vapor samples. The vapor samples were analyzed by using a gas chromatograph. A temperature control system was built based on the results obtained from a heat transfer mathematical model specifically prepared for this research. The results obtained in this study suggest very strongly that crude oil recovery and miscibility in this kind of oil depend on temperature and oil-gas ratio in solution. Multiple-regression equations to predict crude oil recovery using temperature and gas-oil ration in solution were developed based on the experimental data.