The vapor extraction process (Vapex) has received considerable attention as a promising new in-situ recovery technology for difficult to produce heavy oil and tar sand reservoirs. The recovery by currently used thermal based methods can be problematic and uneconomic in some reservoirs. It is likely that the Vapex can potentially overcome some of the recovery difficulties especially in the formations that are thin and heat losses are unavoidable. The advantages of Vapex process might be even more significant in other scenarios such as in the presence of overlying gas cap and/or bottom water aquifer, low thermal conductivity, high water saturation, clay swelling and formation damage and etc.
Several experimental investigations of the Vapex process have been conducted in the laboratory at the pore scale and in small physical models. Most of the past physical model studies of Vapex process have used the rectangular-shaped models, which have limitations when used at higher pressures. In particular, such models become difficult to work with when the desired height and length scales are large.
This paper presents a new design of physical models that overcomes this limitation. It uses the annular space between two cylindrical pipes for constructing the slice-type sand-filled models. The cylindrical geometry makes the model more compatible with higher pressures without making them too heavy and cumbersome.
Side by side Vapex experiments were conducted in the cylindrical models and the rectangular models with equivalent geometrical dimensions. It is shown that the stabilized drainage rates from new cylindrical models are in nearly perfect agreement with those from the rectangular one.
The downward trend of remaining conventional oil reserves all around the world has become a serious source of concern for the industry and governments and is a good reason to think about other energy alternatives. On the other hand, there are huge and virtually untouched resources of heavy oil and bitumen deposits in the globe, especially in Venezuela and Canada. These are now targets of considerable attention and investments by the industry to find a less costly and more effective method to recover the almost immobile hydrocarbons.
Among the several methods proposed for heavy oil and bitumen recovery, solvent extraction of the heavy deposits appears to be very attractive. The Vapor extraction (Vapex) method is basically an analogue of the steam assisted gravity drainage (SAGD) process. In Vapex process, vaporized solvents are used instead of high temperature steam and the oil viscosity is lowered by in-situ dilution instead of heating. A vaporized light hydrocarbon, such as propane or butane, is injected through a horizontal well into the formation containing the viscous oil or bitumen. The solvent gradually dissolves into the bitumen and increases its mobility. The diluted oil with much lower viscosity drains by gravity to another horizontal well, located in parallel below the injector at the base of the formation from where it is brought to the surface. In the early stage of the process, the vaporized solvent rises up to reach the top of the formation and builds a vapor chamber above the injection well.