THAI (Toe to Heel Air Injection) and Beyond
by Franklin L. Foster, Ph.D.
As mentioned elsewhere on this
site, in the early days of the Lloydminster patch, heavy oil was
excruciatingly frustrating. Small productions of conventional oil
giving way to increasingly viscous and, therefore, unproduceable oil.
Innovation was always, by necessity, a part of the local patch. In
the early days unconventional production methods were called "how do we get the damned stuff out" but
are now
referred to as IOR (improved oil recovery) or EOR (enhanced oil recovery).
Not surprisingly one of the early ideas was to apply heat. As early
as 1951, tests were being done on what is now called ISC (In-Situ
Combustion). Almost 60 years later, descendents of this technique are
promising to make major contributions to the recovery of heavy oil.
As the slide presentation
[available through the link below] diagrams, conventional ISC used an
injection well to ignite and maintain combustion through air injection and
drive oil toward the producing well. This process was fraught with several
problems, not least of which was that the producing well was always in the
cold region away from the combustion. What has revolutionized the
process is the advent of horizontal wells. Now, the horizontal well
"toe" can be drilled to be in close proximity to the combustion zone,
resulting in startling increases in recovery rates (to as high as 80%,
whereas, in the old days 20% might be considered good).
Above is a diagram (from the
slide presentation) showing how the "toe" of the horizontal well
penetrates the optimum oil production regions and drives the oil toward
the producing well's "heel". Even more exciting, adding an annular
sheath of catalytic material along the length of the horizontal well can
effectively upgrade the oil prior to production. To quote the
presenter:
|
CAPRI is the
catalytic variant of the THAI process. Imagine an annular sheath of
solid catalyst surrounding the horizontal producer well in the
bottom of the oil layer. Thermally cracked oil produced by THAI
drains into the horizontal producer well, first passing through the
layer of catalyst – like a radial inflow reactor. Thus, THAI and
CAPRI can achieve very significant upgrading (conversion of the
heavy oil, transforming it almost into a light oil). To achieve
equivalent oil conversion in a surface upgrading plant would cost
£100’s millions. THAI/CAPRI achieves the in situ upgrading virtually
for free, compared to the cost of surface upgrading.
- Malcolm Greaves |
In recent field tests,
improvements in viscosity from the range of 10°
API to the range of 16° API have been achieved. In any case, the slide
presentation discusses and details these important innovations which may
lead to significantly enhanced oil recoveries from such "mature" fields as
the North Sea.
The presentation was made to the Petroleum
Society of CIM, Lloydminster (Heavy Oil) Section in September 2007 by
Dr. Malcolm Greaves, of the University of Bath, Department of Chemical
Engineering.
For Slide Presentation -
Click Here
Please Note: Slides contain copyrighted material. Not to be used without
permission.
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see the slides]
