Abstract
Air injection-based enhanced oil recovery processes are receiving increased
interest because of their high recovery potentials and applicability to a wide
range of reservoirs. However, most operators require a certain level of
confidence in the potential recoveries from these (or any) processes prior to
committing resources. This paper addresses the challenges of predicting field
performance of air injection projects using laboratory and numerical
modelling.
Laboratory testing, including combustion tube tests, ramped temperature
oxidation and accelerating rate calorimeters can supply data for simple
analytical models, as well as providing important insights into potential
recovery-related behaviours. These tests are less suited to providing detailed
kinetic data for direct and reliable use in numerical simulators. Indeed, the
oxidation reactions are sufficiently complex that, regardless of how powerful
the thermal reservoir simulator is, its predicting capability will strongly
depend on the engineer's understanding of the process and ability to model the
most relevant oxidation behaviours of the particular oil reservoir under
study.
It is proposed that the optimum design cycle for air injection-based processes
is to perform laboratory testing that would aid in the understanding of the
process and in the design and monitoring of a pilot-scale field operation.
Analytical models and simplified, semi-quantitative reservoir simulation models
would be employed at this stage. If this evaluation stage is successful, a
pilot operation would be initiated and the data gathered during the pilot, as
well as laboratory oil property and compositional data, would then be used to
history match and tune a model for predictions of the full field
operation.
Introduction
This paper has been written in response to questions which many reservoir
engineers express when evaluating the feasibility of air injection as an
enhanced oil recovery process for their fields. Questions such as, "What
laboratory tests are available? What type of data is provided by each test? How
do we use the lab results to predict field performance?" are not uncommon, and,
although there are not straightforward answers, a discussion on the usefulness
of different lab tests is presented to clarify some of the related
concepts.
This document has also been written in response to the concerns and comments
expressed by many reservoir simulation practitioners when matching combustion
tube tests and other supporting oxidation experiments, and trying to predict
field performance of an air injection project based on kinetic parameters
obtained from such tests. Questions such as, "How do we use the lab data in the
reservoir simulator? What are the limitations of thermal reservoir simulation
when predicting field performance of air injection projects?" are addressed to
provide additional feedback and promote further discussion.
Additionally, this manuscript describes some of the combustion behaviours which
have been observed by the In Situ Combustion Research Group (ISCRG) at the
University of Calgary while performing combustion tube tests and supporting
cracking/oxidation experiments, and gives some recommendations to improve the
modelling of the combustion process using thermal reservoirsimulators.
© 2009. Petroleum Society of Canada (now Society of Petroleum Engineers)
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History
- Original manuscript received:
7 January 2008
- Revised manuscript received:
9 February 2009
- Manuscript approved:
2 March 2009
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