Depressurization damage of oil well cement cured for 3 days at various pressures

• High curing temperature increases the 3-day splitting tensile strength of cement.
• Pressure has little effect on the 3-day splitting tensile strength of cement.
• A mechanism for depressurization-induced cement specimen damage is proposed.
• High C3A content in cement increases its risk to damage during depressurization.

A variety of different types of oil well cement were tested with a newly developed test apparatus under different curing conditions to study the effects of curing temperature and pressure on their tensile test behavior. Specimens were cured at temperatures ranging from 24 to 60 °C and pressures ranging from 0.69 to 51.7 MPa. Tensile tests were performed at the age of 72 h. The capability of the test apparatus to record system deformation during pressurization and depressurization also allows study of cement–water interactions at different curing stages. Both splitting tensile tests and water pressure tensile tests were conducted after depressurization for assessing possible damage induced by the pressure change. A potential damage mechanism of set cement during depressurization is proposed in this study by analyzing the system deformation and tensile strength test data.