Experimental Study on the Compressive and Shear Mechanical Properties of Cement–Formation Interface Considering Surface Roughness and Drilling Mud Contamination

In a casing-cement sheath-formation system, the cement–formation interface is usually weakly cemented for residual of drilling mud, in which leakage path would easily form, threatening safe operation underground energy exploitation and storage. To evaluate compressive shear mechanical behavior interface, cement–rock composite cylindrical specimens were prepared. Uniaxial triaxial compression direct tests implemented. The flushing efficiency rock surface, strength, incompatible deformation, parameters morphology failure surface acquired analyzed. Results show that shale decreases from 76.7% to 64.2% with roughness increasing 0 2 mm. sandstone only 44.7%, remarkably lower than shale. With stress condition transforming uniaxial compression, feature stress–strain curves changes elastic-brittle elastoplastic, strength increases 20.6~60.1 MPa 110~120 MPa. cement part presents noteworthy plastic deformation several micro fractures develop. There between rock, induces debonding almost all specimens. internal friction angle cohesive both decrease increase pollution degree rise roughness. facture not exactly rock–cement but manifests as zone, cement, contribute final failure. above findings be valuable revealing mechanism.