Abstract
The vapour extraction (VAPEX) process has been an intense research topic in
recent years as an alternative technology to thermal recovery methods for heavy
oil and bitumen resources. Most previous 2D transparent models had simulated
the vapour chamber evolution behaviour of a vertical slice of the reservoir;
however, the longitudinal vapour chamber evolution characteristic in 3D
geometry could not be detected.
This paper presents the results of 3D monitoring of the VAPEX process in a
laboratory model, using computed tomography (CT) technology to investigate the
vapour chamber expansion behaviour in both radial and longitudinal
directions.
The results show that in 3D geometry, “V” shape vapour chamber expansion was
a localized phenomenon. The dominant characteristic was that solvent gas first
broke through upward to the top, progressing through the high-permeability zone
by gravity segregation, forming a vapour chamber at the top. It then expanded
downward from the top as the experiment progressed. From the numerical analysis
of the CT images, the in-situ porous medium’s porosity, density and oil
saturation profiles were obtained. The results further imply that contained
gravity drainage may be the key for the success of the VAPEX process.
Introduction
For the more than 400 billion m3 heavy oil and bitumen deposits
in Canada, only 10% is surface minable. The major part of the deposits has to
be relied on in-situ recovery processes(1). However, because of their high
viscosities and low-degree API gravities in native state(2), these reservoirs
can only be recovered with low recovery efficiency by conventional methods. For
example, primary recovery in the best of these heavy oil reservoirs is
approximately 6% of the original oil in place (OOIP). Subsequent waterflooding
can improve the recovery to an extent of 1% ~ 2% incremental of OOIP(3). In
order to more effectively recover these reserves, enhanced oil recovery (EOR)
or improved oil recovery (IOR) methods have to be directly applied(4). The main
technology challenge is to reduce the heavy oil viscosity in-situ(5). As the
oil viscosity is very sensitive to temperature, thermal recovery methods seem
to be very effective and have been widely researched and piloted(6), including
cyclic steam simulation (CSS), in-situ combustion (ISC), steam assisted gravity
drainage (SAGD) and steamflooding(7). The SAGD process has been commercially
used by several oil companies in Canada. However, the SAGD process is not
always applicable for all heavy oil reservoirs; some economic constraints arise
if the high cost of steam generation and excessive heat losses in some thin oil
reservoirs are considered(8). As alternatives, non-thermal processes such as
solvent-based processes are still a logical choice to recover such heavy
oil/bitumen reservoirs(9).
© 2010. Society of Petroleum Engineers
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History
- Original manuscript received:
27 March 2008
- Meeting paper published:
17 June 2008
- Revised manuscript received:
28 October 2009
- Manuscript approved:
28 December 2009
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