This paper summarizes numerical and experimental simulation results of a
cyclic solvent injection process study, which was part of a continuing
investigation into the use of solvents as a follow-up process in Cold Lake and
Lloydminster reservoirs that have been pressure-depleted by cold heavy oil
production with sand (CHOPS). Typically only 5% - 10% of the original oil in
place (OOIP) is recovered during cold production; therefore, an effective
follow-up process is required.
The cyclic solvent injection (CSI) experiment consisted of primary
production followed by six solvent (28% C3H8 - 72%
CO2) injection cycles. Oil recovery after primary production and six
solvent cycles was 50%, which indicates the potential viability of the CSI
Concurrently with the laboratory physical simulation, a numerical simulation
model was developed to represent the physical behaviour of the experimental
results. A history match of the primary production portion of the experiment
was obtained using an Alberta Innovates - Technology Futures (AITF) foamy oil
model. This resulted in the characterization (fluid saturations and pressures)
of the oil sandpack at the start of the solvent injection process. The history
match of the subsequent six solvent injection cycles was used to validate the
numerical model of the CSI process developed at AITF.
This model includes nonequilibrium rate equations that simulated the delay
in solvent reaching its equilibrium concentration as it dissolves or exsolves
in the oil in response to changes in the pressure and/or gas-phase composition.
Dissolution of CH4, C3H8 and CO2 in
oil and CO2 in water were considered, as was exsolution of
CH4, C3H8 and CO2 from oil and
CO2 from water. Reduced gas-phase permeabilities resulting from gas
exsolution were also included.
The history match simulations indicated that:
- The important mechanisms were represented in the simulations.
- Significant oil swelling by solvent dissolution occurs during solvent
injection periods. This can reduce solvent injectivity and penetration into a
heavy oil reservoir during solvent injection periods.
- Low oil and gas-phase relative permeabilities are required during
production periods to match the experimental oil and gas production during
A parametric simulation study showed that the quantity of gas injected in an
injection period was relatively insensitive to the oil-phase diffusion
coefficients, but was sensitive to solvent solubility in oil, dissolution
rates, gas-phase diffusion coefficients, molar densities in the oil phase,
gas-phase relative permeability and capillary pressure. It was shown that oil
production is highly dependent on how quickly solvent can dissolve in the oil
during injection and exsolve from the oil during production.
© 2010. Society of Petroleum Engineers
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- Original manuscript received:
28 March 2009
- Meeting paper published:
17 June 2009
- Revised manuscript received:
30 June 2010
- Manuscript approved:
8 July 2010
- Published online:
1 September 2010
- Version of record:
1 September 2010