PSI - Issue 28

7

A. Kostina et al. / Procedia Structural Integrity 28 (2020) 675–683 Author name / Structural Integrity Procedia 00 (2019) 000–000

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Fig. 4. Ratio of permeability at 400 th day of SAGD to initial permeability (a) thermo-elastic model, non-uniform steam distribution; (b) thermo inelastic model, uniform steam distribution; (c) thermo-inelastic model, non-uniform steam distribution.

Fig. 5 presents results of the vertical heave by 400 th day of SAGD. Volumetric expansion of the pore space at the macroscale is expressed by vertical heave of the surface. As it has been mentioned by Shafiei and Dusseault (2013), the single mechanism of thermal expansion could not provide significant values of the vertical heave (Fig. 5 (a)). Structural damage defined by the proposed equations (12)-(13) simulates additional contribution to strain induced by the rise in volumetric-type defects (microcracks) due to the increase in the shear-type defects (microshears) which gives one order of magnitude higher values (Fig. 5 (b), Fig. 5(c)). Threshold stress values in (12)-(13) could be considered as the initiation criteria for this mechanism. It should be noted also that non-uniform distribution of the steam chamber induces non-uniform heave as it presented in Fig. 5(c).

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Fig. 5. Vertical displacement, m (a) thermo-elastic model, non-uniform steam distribution; (b) thermo-inelastic model, uniform steam distribution; (c) thermo-inelastic model, non-uniform steam distribution.

Fig. 6 demonstrates oil production rate after the establishment of the interwell communication. Uniform distribution of the steam chamber doubles the results and gives the biggest value of the oil production rate. Therefore, the uniform model of the steam chamber development can overestimate the oil production rate. In real SAGD process when the steam chamber near the heel spreads laterally along the upper boundary of the reservoir, the steam chamber far behind the heel can be only at the vertical rising stage. As for the non-uniform distribution, on the initial stage when the influence of the structural strain is small the oil production rates are slightly different from each other. When the volumetric increase in strain due to the evolution of defects is significant the distinction between all models is more pronounced.