Petroleo

Energy & Fuels 2009, 23, 327–333

327

Analysis and Simulation of Steam Distillation Mechanism during the Steam Injection Process
Mohammad T. Vafaei, R. Eslamloueyan, L. Enfeali, and Sh. Ayatollahi*
EOR Excellence Research Centre, College of Petroleum and Chemical Engineering, Shiraz UniVersity, Shiraz, Iran ReceiVed July 28, 2008. ReVised Manuscript ReceiVed October 31, 2008

Steamdistillation could improve the oil recovery efficiency during the steam injection enhanced oil recovery process. Because of its immense effects on oil recovery, it is important to investigate the main parameters of steam distillation as well as the effects of oil and reservoir properties during this thermal process. In this work, the simulation of batch steam distillation is performed on 18 sets ofcrude oil found in the literature. The developed model is highly compatible with respect to the input oil properties that can also characterize the oil with minimum entry. The calculated distillates were compared to the experimental data, and the results show an average relative error of 13.74% for 15 sets of crude oil data, each calculated at 20 different points. According to this study, thesuperheat conditions of steam and the amount of light oil fractions have the greatest effect on the distillation yields, while the steam saturation conditions have less considerable effects. It was also found that the steam injection rate has almost no effect on the distillate recovery. Butler’s correlation for steam-assisted gravity drainage (SAGD) recovery was modified to evaluate the effects of thesteam distillation mechanism during the SAGD process. The results reveal that almost 10-30% of the oil recovery is because of the steam distillation mechanism during the steam injection process.

Introduction Steamflooding, a thermodynamically complex oil displacement process, is currently used as one of the most successful enhanced oil recovery methods for heavy oil production.1 This processinvolves simultaneous heat, mass, and fluid transport in the heavy oil reservoir, which aims to increase the oil recovery efficiency. Although it has been widely claimed that viscosity reduction plays a key role in increasing the oil recovery efficiency during thermal processes, including steamflooding, this process differs markedly in performance from other thermal methods.2-4 Experimental studies areperformed to study the effect of different mechanisms during steamflooding, such as viscosity reduction, thermal expansion, gas drive, extraction effects, steam distillation on oil recovery efficiency, and wettability alteration of the reservoir rock.5,6 According to these studies, the residual oil after steamflooding is essentially independent of the initial oil saturation and the oil recovery efficiencyis higher for lighter hydrocarbons because they contain a greater fraction of distillable components.5 It is widely known that the
* To whom correspondence should be addressed. Telephone: +989171184379. E-mail: shahab@shirazu.ac.ir. (1) Butler, R. M. Thermal RecoVery of Oil and Bitumen; GravDrain, Inc.: Calgary, Alberta, Canada, 1997. (2) Prats, M. Thermal RecoVery, SPE Monograph; Society ofPetroleum Engineering: Richardson, TX, 1986. (3) Farouq Ali, S. M. Heavy oil-evermore mobile. J. Pet. Sci. Eng. 2003, 37, 5–9. (4) Nabipour, M.; Escrochi, M.; Ayatollahi, S.; Boukadi, F.; Wadhahi, M.; Maamari, R.; Bemani, A. Laboratory investigation of thermally-assisted gas-oil gravity drainage for secondary and tertiary oil recovery in fractured models. J. Pet. Sci. Eng. 2007, 55, 74–82. (5)Willman, B. T.; Valleroy, V. V.; Runberg, G. W.; Cornelius, A. J.; Powers, L. W. Laboratory studies of oil recovery by steam injection. J. Pet. Technol. 1961, 222, 681–690. (6) Ayatollahi, Sh.; Lashanizadegan, A.; Kazemi, H. Temperature effects on heavy oil relative permeability during gas-oil gravity drainage (GOGD). Energy Fuels 2005, 19 (3), 977–983.

Figure 1. Schematic of steam distillation....