Experimental and analytical modeling studies of steam injection with hydrocarbon additives to enhance recovery of San Ardo heavy oil
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Experimental and analytical studies have been carried out to better understand production mechanisms of heavy oil under steam injection with propane and petroleum distillate as steam additives. The studies have been conducted for heavy oil from San Ardo field (12oAPI, 2800 cp at 53.3oC), under current reservoir conditions. The experiments consist of injecting pure steam, steam-propane, and steampetroleum distillate into a vertical cell containing a mixture of sand, water and San Ardo oil. The injection cell (68.58 cm long with an ID of 7.376 cm) is placed inside a vacuum jacket, set at the reservoir temperature of 53.3oC. Superheated steam at 230oC is injected at 5.5 ml/min (cold-water equivalent) simultaneously with propane or a petroleum distillate slug. The cell outlet pressure is maintained at 260 psig. Six runs were performed, two runs using pure steam, two steam-propane runs using 5:100 propane:steam mass ratio, and two steam-petroleum distillate runs using 5:100 petroleum distillate:steam mass ratio. We develop a simplified analytical model that describes steam front advancement and oil production for the 1D displacement experiments. The model incorporates heat and material balance, fillup time and Darcy??????s law pertaining to the injection cell. The analytical model results are compared against the experimental data to verify the validity of the model. The main results of the study are as follows. First, experimental results indicate that compared to pure steam injection, oil production was accelerated by 30% for 5:100 propane:steam injection and 38% for 5:100 petroleum distillate:steam injection respectively. Second, steam injectivity with steam-propane and steam-petroleum distillate increases to 1.4 and 1.9 times respectively, compared with pure steam injection. Third, steam front advancement and oil production data are in good agreement with results based on the new analytical model. The analytical model indicates that the oil production acceleration observed is due to oil viscosity reduction resulting from the addition of propane and petroleum distillate to the steam. Oil viscosity at the initial temperature with pure steam injection is 2281 cp, which is reduced to 261 cp with steam-propane injection and 227 cp with steam-petroleum distillate injection.