Steam Assisted Gravity Drainage was first proposed in late 1970's and has been developing eversince. This process was devised to produce heavy oil by continuous injection of steam into a growing chamber. During the process steam is injected into a steam chamber at the rate required to maintain the pressure and thus the temperature within the chamber. At the contact of the steam and the oil, condensed steam and heated oil flows downward towards the production well located under the injection well.
In this study a Computerized Tomography (CT) was used for visualization of the development of the steam chamber. An Aluminum core holder packed by 14–35 mesh limestone was saturated with water, and steam was injected at four different rates through the upper one of the two parallel horizontal wells located at the down part of the sand pack. Temperature and pressure of steam was monitored at the injection line, and all the system was insulated by glass wool to reduce heat losses.
Totally six experiments were conducted and besides production and injection data, CT images were taken. Images were taken with regard to production, instead of regular time intervals. The shape of the chamber was found to be similar to that theoretically described in literature from CT images and presence of chamber was supported by production data also. Vertical distance of wells was found to be not affecting production in case of mobile fluids. But injection rate did. As the injection rate increased production rate increased also.
With the decline of light oil reserves, a major thrust of oil industries throughout the world is on the exploitation of the huge resources present in the form of heavy oil and bitumen. These resources are approximately six trillion barrels of oil in place throughout the world. Heavy oil and bitumen are characterized by their high viscosities and low degree API gravities (Das and Butler1). And, in Turkey, 80 percent of the oil reservoirs are heavy-oil reservoirs. These heavy oils are usually mobile at reservoir conditions and most can be produced with primary production but recovery is very low (Bagci and G?mrah2).
However only the application of primary and secondary recovery methods can produce a small portion of these oils. Consequently, the development of a suitable enhanced oil recovery process is of vital importance. The aim of suitable processes is to influence the physical and/or chemical properties of the reservoir and its contents in such a way to improve oil recovery. In thermal recovery processes, heating the reservoir reduces the viscosity.
In steam applications various mechanisms contribute to the higher recovery. Among them, gravity drainage and thermal expansion play important roles. One other mechanism to contribute to the production is distillation of lighter hydrocarbon components, and related solvent drive.
SAGD has proved its superiority in the field, wherein oil/steam ratios ultimate recoveries, and production rates have exceeded those of conventional methods by factors of two to ten.
