Published by the DTI Oil & Gas Directorate for the reservoir
engineering and IOR community in the UK.
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by 15 August 2002.
Feedback
Light Oil Recovery via Air Injection Technology
Following the release of Issue 1 on the newsletter, we received questions
relating to the article by Demetrios
Yannimaras of BP Exploration on light oil recovery via air injection.
The questions came from S Lijhara who is an Oilfield Chemist working for
ONGC (JRC) in New Delhi, India and the answers below have been provided
by Demetrios.
Q: Thank you for providing the valuable information about BP's work.
I am quoting some of the lines of the article
"the in-situ generated flue gas (85%N2 + 15%CO2) is the main driving
force for oil displacement. The flue gas pressures up the reservoir, mobilises,
strips, and swells the in-place oil, and at sufficient pressure can miscibly
and near-miscibly displace the oil."
Here I add as the reservoir starts depleting with the above mechanism
there is more and more quantity of flue gases quantity remains inside.
What consideration you have given to the seepage of flue gases above the
cap rock and charging the upper formation?
A: In any injection process using water or gas, reasonable assurance should
be provided by the geology of the reservoir that the injectants will remain
in the formation they are injected into. If the caprock is impermeable
to natural gas or water, in an air injection process it will be heated
somewhat, but will be usually impermeable to air.
Q: What contribution does the flue gases make to the reservoir pressure?
A: The reservoir pressure goes up by mass addition (gas or water), and
while injection/withdrawals ratio (in reservoir units) is greater than
one.
Q: How do flue gasses or the rise in temperature affect the brine
(CaCl2/NaCl) in terms of its density or stability when these brines are
used in W/O jobs in the are under IOR?
A: The produced brine is fresher, after some initial period depending
on the injection rate and well spacing; it will be diluted by the water
created by the in-situ combustion process.
Q: Your comment and references on the above points will help in clarifying
doubts about the applicability of the technique.
A: We do not wish to promote this process as applicable to every reservoir.
If in doubt, do not apply.
We also received feed back on this article from John Hansen of First Echelon
Ventures of Vancouver, British Colombia, Canada who have implemented a
low temperature oxidation (LTO) air injection project in the Morton field,
Wyoming, USA operated by Mtarri Inc. The project is aimed at increasing
production from 1 stb/d to 50 stb/d per well. First Echelon feel that
this is accomplishable due to the steeply dipping formation, light high
gravity oil and the oil's ability to sustain oxidation. The project is
under way and continues to show good signs of increased reservoir pressure
and some increase in production. Time will tell but they are extremely
excited with results to date.
Further details on the project and air injection in general are available
on the First Echelon Ventures website at www.feventures.com
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