Cyclic Solvent Injection Process for Heavy Oil Recovery
Figure 4: Dissolution and Exsolution of Component i Solvent Dissolution: Rate proportional to xieqm
Figure 6: Incremental and Cumulative Oil Production During the Experiment
Gaseous component i Dissolved component i – xi
Solvent Exsolution: Dissolved component i Gaseous component i
Rate proportional to xi – xieqm Figure 5: Radial Drainage into a Wormhole Laboratory model
10 20 30 40 50 60
0 Primary Cycle 1 Cycle 2 Incremental
Cycle 3 Cycle 4 Cycle 5 Cumulative
Table 1: Primary Production and Six Solvent Cycles (28% Propane and 72% Carbon Dioxide)
Dead oil density at 20ºC (g/cm3) Dead oil viscosity (mPa.s)
Wormhole
Permeability (Darcy) Porosity (%)
0.988
39,320 at 20ºC 345 at 75ºC 48.4 at 120ºC 4.5 38
Pre-primary gas-oil ratio (STD cm3/cm3)8 Pre-primary oil saturation Pre-primary water saturation Pre-primary pressure (mPa.a)
Gas values were determined for standard (STD) conditions of 101 kPa.a and 15ºC Schematic
It also assumes increased competition between gas and oil flow, typically resulting in a significant under-prediction of oil production. In field-scale simulations, the non-equilibrium behaviour is greater for
Numerical simulation and laboratory experiments are important in designing a CSI strategy for a particular reservoir and in interpreting the results obtained during the process.
larger grid blocks, i.e. it takes longer to reach equilibrium in a large block. Appropriate values must be selected for simulation models based on an in-depth knowledge of the process from laboratory-scale experiments, previous field-scale simulations and field data if available. Modelling of CSI is improving as more data (e.g. pressure, volume, temperature, live oil viscosities, etc.) become available.
Solvent Dissolution and Exsolution
The delay in solvent component i dissolving in oil and exsolving from oil is represented in AITF models (see Figure 4). In field-scale modelling, the BHP is matched using dissolution rate parameters for specified injection rates. The more soluble the injected gas and the quicker it dissolves, the lower the rise in BHP will be during an injection period. In contrast, the injection of a low solubility or slowly dissolving gas will cause a relatively rapid rise in injection pressure.
EXPLORATION & PRODUCTION – VOLUME 9 ISSUE 2
Figure 7: Oil Production During Cyclic Solvent Injection Cycles 2003-02-02 Test 8-4-3
2,000 1,500 1,000 500 0 0 100 200 Experiment SC = surface conditions (15ºC and 101.3kPa.a).
During gas exsolution, foamy oil behaviour can be part of the non- equilibrium process. This factor is included in current AITF models.
Solvent/Oil-mixture Viscosity
A mixing rule, such as the following equation, is used to determine the oil-phase viscosity: 1n(µliveoil) = ∑(xi µi)
where µi is the pseudo-viscosity in the oil phase of component i. Solvent/Oil-mixing Process
Solvent and oil are mixed in a reservoir as a result of convection, diffusion, dispersion and dissolution. Diffusion is represented in simulators by Fick’s first law. Diffusion coefficients should be based
37 300 Time (day) Predicted 400 500 600
0.88 0.12 3.3
Cycle 6
3m
3m Cumulative oil SC (cm3 ) Oil recovery (%)
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