An enhanced SAGD process named SAGD-ISSLW for heavy oil recovery has been studied by experiments using 2-dimensional scaled physical-models, video and infra-red visualization techniques. In the usual SAGD process, oil production rate increases with increasing vertical well spacing between two horizontal wells, but the lead time to start oil production by gravity drainage is longer at the initial stage. The new process uses a lower horizontal well with both functions of intermittent steam-injection and continuous oil-production instead of the usual SAGD production-well. Meanwhile, like in the usual SAGD, the steam is also injected continuously through the upper well as same as the usual SAGD. The benefits of the new concept reported in the paper are quick buildup of warm steam chamber and higher oil production rate as compared to the usual SAGD process.
The process also has advantages for setting longer vertical well spacing and keeping temperature of flowing heavy-oil in the surface-drilled SAGD wells by the single well configuration.
It is not easy to produce heavy oil efficiently and economically. However, as shown in the reports of the UTF projects (phase A and B) in Canada, the steam assisted gravity drainage, SAGD, process has proven to be very superior process for the recovery of the bitumen due to its high recovery factor. The process has been developed by Butler and his coworkers. Their ideas was to overcome the problems associated with the highly viscous bitumen by gravity drainage in steam chambers generated by displacement of heavy oil. Recently, the surface-drilled SAGD process has been tested as more economical one. The SAGD process operated by steam injection from upper well and production from lower well like that of UTF project, is hereinafter referred as ‘usual SAGD’.
A problem of the usual SAGD process for oilsands reservoirs is the lead time required to generate a steam chamber in near break-through condition between two wells before the rising chamber stage.
The more economical SAGD process should be achieved by an enhanced process to shorten the period of initial stage with effective usage of boilers and production facilities.
In this study, expanding or rising process of steam chamber and drainage mechanism along the chamber interface at the initial stage have been investigated by video-pictures and temperature distributions visualized using thermal-video system. The scaled physical reservoir models (200 x 200 mm and 300 x 300 mm, thickness = 4.5 or 9.6 mm) with tightly packed glass-beads (diameter =
