Inverse problem theory to estimate thermo-poroelastic parameters: An analytical/ experimental approach

Induced stresses are one of the main factors affecting wellbore instability and associated problems in drilling operations. These stresses are significantly impacted by pore pressure variation and thermal stresses in the fields. Heat and fluid transfer capability of rock and thermal expansion coefficient are important parameters in the study of stresses using a thermo-poroelastic model. In this study, the field equations governing the problem have been derived based on the thermo-poroelastic theory and solved analytically. Afterward, the couple of 50 mm synthetics sand-cement samples are applied in laboratory experiments. The in situ stresses and wellbore pressure are applied on the sample in a true triaxial stress cell (TTSC). In the laboratory tests, the temperatures are controlled and cooled oil is injected into the sample. The strains are measured and calculated based on experiment and model. In the next step, a genetic algorithm has been applied to solve an inverse problem and get a match between experimental data and the modeling results. Ultimately, the important properties for the interactions of fluid and rock can be estimated. With this approach, the required thermal and flow parameters are estimated with good accuracy without using time consuming and costly tests.