Further experimental studies of steam-propane injection to enhance recovery of Morichal oil

Abstract

In 1998-1999, experimental research was conducted by Goite at Texas A&M University into steam-propane injection to enhance oil recovery from the Morichal field, Venezuela. Goite's results showed that, compared with steam injection alone, steam-propane injection accelerated oil production by as much as 23 % pore volume of steam injected (cold-water equivalent). The apparatus and procedure used in this study have been improved. Steam injection rate was kept constant at 5 cc/min (cold-water equivalent) for all runs. Four thermocouples were placed along the longitudinal axis of the cell to measure temperature profiles during injection. A new, more efficient method was developed to break emulsion in the produced sample. For four of the eight runs, consistent operating conditions were obtained by use of superheated steam, cell pressure of 50 psig, and identical insulation. Eight experimental runs were made in which the propane:steam mass ratios used were 0:100 (steam only), 1:100, 2.5:100, and 5:100. A run using 5:100 nitrogen: steam mass ratio was also made. The main findings of this research (derived from four runs with consistent operating conditions) are as follows. First, the propane:steam mass ratio of 5:100 accelerated the start and peak of oil production by 20 % and 13 % pore volume steam injected (cold-water equivalent), compared to steam injection alone. Second, oil recoveries for practical purposes are similar in all cases, 63 % - 70 % OOIP if average high and low values are taken. Third, the start of production is practically the same for 0:100 and 1:100 propane:steam ratio and for 5:100 nitrogen: steam ratio. In the latter case, the production peak is higher due to additional drive from nitrogen injection. Fourth, oil production acceleration in the 5:100 propane:steam case is probably caused by dry distillation in which light fractions of the oil partition into and are carried by the injected propane to lower the viscosity of the oil ahead of the steam front. Last, convective heat transfer at any of these low (5:100) ratios appears to be of secondary importance.