Geometrical Effect Of Steam Injection On The Formation Of Emulsions Nn The Steam-Assisted Gravity Drainage Process

Abstract

Abstract The production from the in-situ thermal recovery of heavy oils always consists largely of water in oil emulsion. These are much more viscous than the oil itself. In this paper, the production of such emulsions has been studied in a laboratory scaled reservoir model and it has been found thai the degree of in situ emulsification can be changed by altering the geometry of the steam injection. Laboratory studies on the steam-assisted gravity drainage process were conducted to monitor the content of water/oil emulsion in the produced fluid for two different well configurations. The first consisted of a steam injector slightly above a producer at the base of the formation; the second consisted of a producer at the base of the formation and a vertical circulating steam injector which was perforated near the top of the formation. The experiments were conducted in a visual reservoir model with Cold Lake bitumen at 153 kPa steam injection pressure. The temperature profile within the model was monitored continuously. The flow patterns of steam and heated bitumen were recorded using time-lapsed movies. A much higher water/ oil emulsion content was found in the produced fluid when the steam chamber was rising in the experiment with bottom steam injection than with injection at the top. The rate of recovery was higher in the operation with top injection. The water/oil emulsion increased the viscosity of the produced fluid. The particle size of porous materials did not affect the water content in the water/oil emulsion in the range studied. Introduction In the steam-assisted gravity drainage process, steam is injected continuously above a horizontal production well which is completed at the base of the reservoir. The injected steam moves upward and sideways and forms a steam chamber. The steam condenses at the interface and liberates heat to the surrounding reservoir. This causes the oil near the interface to become heated and to drain by gravity toward the production well. Butler et al. (1–2) did early experimental and theoretical studies for the recovery of bitumen using two parallel wells. Their theoretical prediction agreed well with the experimental results. As in many other thermal recovery processes, the oil is produced in the form of an emulsified water/oil mixture. SteinboTl1 and Flock(5), Dealy(6), and Marsden and Mao(7) reported the rheological properties of water/oil emulsions formed by dispersing water into Albertan and Californian heavy crude oils. These studies all show a substantial increase in the viscosity of water/oil emulsions as the water content increases, Clearly, the water content in the emulsion should be minimized to improve the recovery rate*. Another problem is the separation of oil from water/oil emulsions; there is considerable literature on the demulsification processes. In this work, an attempt is made to elucidate the geometrical effect of steam injection on the water/oil emulsion of the produced fluid in the steam-assisted gravity drainage process. Two different well configurations are considered. These are shown in Figure J: