Experimental Investigation of Coupled Flow-Mechanical Behavior of Inclined Heterolithic Strata (IHS) During Steam-Assisted Gravity Drainage (SAGD) Operations

ABSTRACT: This study aims to investigate the geomechanical response and permeability change of oil sands, mud stone, and inclined heterolithic stratification (IHS) under stress paths during steam-assisted gravity drainage (SAGD) operations. Drained triaxial unloading tests were conducted to evaluate stress-strain, failure envelope, volumetric, and permeability responses for the three sample types. Sand samples exhibited high dilation, and permeability increased exceeding 700% when the confining stress was 3.5 MPa during the triaxial unloading test. Mud samples demonstrated cohesive behavior, showing minimal permeability changes of 160% and transitioned from ductile behavior at the highest axial stress to brittle failure with significant strain-softening behavior at lower axial stresses (1.0 and 0.5 MPa). IHS samples exhibited similar volumetric behavior resembling reconstituted sand but permeability responses closer to mud. Failure envelopes were captured for all sample types, showing similar friction angles for sand and mud, while IHS samples had lower strength due to weaker interfacial zones. These findings highlight the critical role of material composition, lithological heterogeneity, and confining stress in controlling reservoir deformation and fluid flow, offering valuable insights into caprock integrity and performance optimization during SAGD operations.