Stress Path and its Implications on Drilling in Partially Depleted Formation

Estimation of reservoir in-situ stress changes, i.e., stress path, during depletion and injection is of paramount importance since these induced stress changes may cause drilling fluid lost circulation, sand production, casing collapse, etc.;One source of discrepancies between the current modeling tools and the field measurements of the in-situ horizontal stress via fracturing tests is that the boundary conditions in the field may not correspond to the oedometric assumption. In this study, several coupled analytical models are developed to study the spatio-temporal stress path prediction under different deformational conditions.;Another source of discrepancies between the measured and predicted stress paths is related to the material behavior. In this research, we study several space- and time-independent models to predict the stress path for different behavioral models. The perfectly plastic material models are implemented to study the stress path for brittle low-porosity rocks and high porosity rocks at low effective mean stresses. Moreover, the cohesive hardening models are intended to predict the stress path for a wider range of porosities but at low effective mean stress values. Finally, the cap plasticity models are used to include the pore collapse phenomenon observed in high porosity compactible rocks.;Since the stress path in elastic and plastic states are mainly controlled by the Poisson's ratio and friction angle, it is critical to have accurate estimations of these parameters for precise prediction of stress path. In this study, we propose a novel geomechanical well testing approach that includes all analysis techniques for estimation of mechanical properties of reservoir formation using the pressure transient testing. The proposed geomechanical well testing is used to determine the in-situ Poisson's ratio under different boundary conditions. Using the Theory of poroelastoplasticity, for the first time, we propose a geomechanical well testing technique to estimate the strength properties of reservoir formation such as friction and dilation angles.;It is important to have estimations of stress path at different times and locations within a reservoir. Therefore, two spatio-temporal stress path models are developed under plane strain-traction and displacement boundary conditions based on the Theory of Poroelastoplasticity using Drucker-Prager cohesive hardening function.;Prediction of formation fracture pressure is vital in well design considerations to avoid lost circulation of drilling fluid and other wellbore instability problems. The previous models are based on the Poroelasticity Theory assuming an elastic behavior during reservoir depletion. However, we propose several analytical models for estimation of the fracture initiation pressure in pre-plastically deformed wellbores.;To better understand the stress path, several experimental tests are designed to simulate the production and injection operations under in-situ conditions using a Rock Mechanics Facility (RMF) at TUDRP. The experiments are performed under different deformational conditions.