PSI - Issue 37

A. Kostina et al. / Procedia Structural Integrity 37 (2022) 431–438 A.Kostina/ Structural Integrity Procedia 00 (2019) 000 – 000

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Figure 3 presents the results of the vertical displacement obtained for plastic and elastic problems. As it can be seen, the single mechanism of thermal expansion could not provide significant values of the vertical heave. The maximum value of displacement for the elastic problem is about 5 cm while for the plastic problem this value is three times greater. This can be explained by a significant contribution of plastic volumetric strain into total volumetric strain. Figure 4 displays evolution of the plastic ant total volumetric strains at the point located near the top of the layer. The results show that the plastic strain is almost half of the total volumetric strain.

(a)

(b)

Fig. 3. Final vertical displacement in reservoir for: (a) plastic problem, (b) elastic problem.

Fig. 4. Evolution of volumetric strain and plastic volumetric strain for plastic problem in the point located near the top of the reservoir.

Moreover, figure 5 (a) shows that the plastic strain gives a threefold rise in porosity in comparison with the pure thermo-elastic strains because the porosity is a function of the total volumetric strain. It is noticeable that after 50th day of the heating process porosity in the plastic problem continue to rise slightly while porosity in the thermo-elastic problem starts to decrease. This can be explained by the unloading of the formation after propagation of the steam chamber through the considered point. However, for the plastic problem the most part of the total strain is irreversible and the effect of the unloading is negligible. The same character of distribution is observed for the permeability. Figure 5 (b) displays ratio of current permeability to the initial value. In the case of the plastic problem there is a rise in permeability in 1.14 times while for the thermo-elastic problem this rise is about 1.04 times. A higher increase of reservoir properties in case of the plastic problem leads to a higher rise in oil recovery rate in comparison with the thermo-elastic problem as is shown in figure 6. Also, slower steam chamber development in the thermo-elastic problem retards oil recovery rate which is expressed by a shift of the black curve on nearly 17 days in