PSI - Issue 13

A. Kostina et al. / Procedia Structural Integrity 13 (2018) 1159–1164 Author name / Structural Integrity Procedia 00 (2018) 000–000

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(a) (b) Fig. 2. Volumetric structural strain (a) initial; (b) after 700 days of continuous steam injection.

(a) (b) Fig. 3. Evolution of vertical permeability (a) thermo-elastic model; (b) thermo-inelastic model.

Structural changes induced by initiation and evolution of defect systems alter not only rock properties but also the stress state in the reservoir. Such changes can lead to the caprock fracture and break the integrity of a steam chamber. Loss of a caprock integrity is a serious problem for a human safety and environment. Figure 4 illustrates assessment of a caprock failure according to the Drucker-Prager criterion obtained for two cases: thermo-elastic and thermo-inelastic problems. Strength parameters for a caprock were taken from (Rahmati et al., 2017). It can be seen that according to the thermo-elastic solution there is no fracture for the considered heating temperature and pressure, while thermo-inelastic solution gives an opposite result. Therefore, thermo-elastic mathematical model can lead to the overestimation of the caprock strength.

Fig. 4. Illustration of the fracture criterion for a caprock (1-solution to thermo-inelastic problem, 2-solution to thermo-elastic problem; 2 J denotes the second invariant of a deviatoric stress, 1 I denotes the first invariant of a stress tensor).