Summary
This paper presents an integrated workflow for the interpretation of 4D
seismic data to monitor steam chamber growth during the steam-assisted gravity
drainage recovery process (SAGD). Superimposed on reservoir heterogeneities of
geological origin, many factors interact during thermal production of heavy oil
and bitumen reservoirs, which complicate the interpretation of 4D seismic data:
changes in oil viscosity, fluid saturations, pore pressure, and so on.
The workflow is based on the generation of a geological model inspired by a
real field case of the McMurray formation in the Athabasca region. The approach
consists of three steps: the construction of an initial static model, the
simulation of thermal production of heavy oil with two coupled fluid-flow and
geomechanical models and the production of synthetic seismic maps at different
stages of steam injection.
The distribution of geological facies is simulated on a fine grid using a
geostatistical approach, which honours all available well data. The reservoir's
geomechanical and elastic properties are characterized by logs and literature
at an initial stage before the start of production. Production scenarios are
run to obtain pore pressure, temperature, steam and oil saturations on a
detailed reservoir grid around a well pair at several stages of production.
Direct coupling with a geomechanical model produces volumetric strain and mean
effective stress maps as additional properties. These physical parameters are
used to compute new seismic velocities and density for each stage of production
according to Hertz and Gassmann formulas. Reflectivity is then computed, and a
new synthetic seismic image of the reservoir is generated for each stage of
production.
The impacts of heterogeneities, production conditions and reservoir
properties are evaluated for several simulation scenarios from the beginning of
steam injection to 3 years of production. Results show that short-term seismic
monitoring can help in anticipating early changes in steam injection strategy.
In return, long-term periods allow the behaviour of the steam chamber to be
monitored laterally and in the upper part of the reservoir. This study
demonstrates the added value of 4D seismic data in the context of
steam-assisted heavy oil production.
© 2010. Society of Petroleum Engineers
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History
- Original manuscript received:
31 March 2009
- Meeting paper published:
17 June 2009
- Revised manuscript received:
1 April 2010
- Manuscript approved:
6 April 2010
- Published online:
21 June 2010
- Version of record:
1 June 2010
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