Summary
We investigate oil recovery from multicontact miscible (MCM) gas injection
into homogeneous and crossbedded porous media, using a combination of
well-characterized laboratory experiments and detailed compositional flow
simulation. All simulator input data, including most EOS parameters, were
determined experimentally or from the literature produced fluids in all
experiments were found not to be in compositional equilibrium. This was not
predicted by the simulator, giving a poor match between experimental and
simulated oil recoveries. The match was significantly improved for the
cross-bedded displacements by using alpha factors derived from the MCM
displacements in the homogeneous pack.
Introduction
The recovery of oil by miscible gas injection has been a subject of interest
and research in petroleum engineering for more than 40 years (Stalkup
1983). In a first-contact, miscible (FCM) displacement, the gas and oil
mix instantly in all proportions. No capillary forces exist, so, in
principle, residual oil saturation is zero, and 100% oil recovery should be
achieved. In practice, many phenomena conspire to limit the efficiency of the
miscible flooding process, including viscous fingering, gravity override, and
permeability heterogeneity. Moreover, it is often not economical, and
sometimes not technically feasible, to inject a gas that is first-contact
miscible with the oil. Instead, the injected gas is designed to develop
miscibility with the oil by mass transfer during the displacement. This is a
so-called MCM gas injection. If the bulk of the mass transfer is from the
gas to the oil, then the displacement is termed a condensing drive. If
most of the mass transfer is from the oil to the gas, then it is termed a
vaporizing drive. In most cases, however, because of the multicomponent nature
of oil and gas, the mass transfer is actually a mixture of both these cases,
and the displacement is termed a condensing-vaporizing drive.
Small-scale heterogeneities can have a significant impact on recovery
efficiency (Jones et al. 1995; Jones et al. 1994; Kjonsvik et al. 1994), yet
they cannot be modeled explicitly in field-scale simulations. Some of the
most common small-scale heterogeneities found in sandstone reservoirs are
laminations. However, because laminations have a small size and are generally
at an angle to the principal flow direction,their influence onfluid flow is one
of the most difficult features to predict numerically.
There is a significant amount of literature describing systematic
investigations of first-contact miscible and immiscible displacement processes
in laminated sandstones (Huang et al. 1995, 1996; Ringrose et al. 1993;
Kortekaas 1985; Honarpour et al. 1994; Hartkamp-Bakker 1991, 1993; McDougall
and Sorbie 1993; Marcelle-DeSilva and Dawe 2003; Borresen and Graue 1996; Roti
and Dawe 1993; Dawe et al. 1992; Caruana and Dawe 1996; Caruana 1997). Both
experimental and simulation studies show that significant volumes of oil can be
trapped by capillary forces during immiscible displacements (Huang et al. 1995,
1996; Ringrose et al. 1993; Kortekaas 1985; Honarpour et al. 1994;
Hartkamp-Bakker 1991, 1993; McDougall and Sorbie 1993; Marcelle-DeSilva and
Dawe 2003; Borresen and Graue 1996; Roti and Dawe 1993; Dawe et al. 1992;
Caruana and Dawe 1996; Caruana 1997). However, the influence of these
heterogeneities on MCM displacements, during which capillary forces change from
being very significant when gas is first injected to negligible once
miscibility has developed, has not yet been investigated. Indeed, the only
comparisons of well-characterized MCM displacement experiments and detailed
simulations reported in anywhere in the literature are those of Burger and
colleagues (Burger and Mohanty 1997; Burger et al. 1996; Burger et al.
1994).
© 2007. Society of Petroleum Engineers
View full textPDF
(
2,972 KB
)
History
- Original manuscript received:
3 December 2004
- Meeting paper published:
31 March 2005
- Revised manuscript received:
16 April 2006
- Manuscript approved:
25 September 2006
- Version of record:
20 March 2007
View Cart
