DEVELOPMENT OF HOLLOW-CYLINDER TENSILE TESTER IN TWO-PHASE FLUIDS

The strength of rock in two-phase fluids is an important parameter and is scientific problem in common of fracturing-enhanced oil recovery and safety control for projects such as CO2 geological storage,oilfield development and unconventional energy exploitation.A new hollow-cylinder cell has been developed to investigate the effects of two-phase fluids on rock failure.The hollow-cylinder cell can apply different combinations of internal and external hydrostatic pressures,axial and pore pressures to explore the rock tensile strength in state of true triaxial stress;and rock tensile failure test in two-phase fluids can be controlled.Technical problems for uniformity and constancy of testing temperature,saturation degree control and sample sealing performance under high triaxial pressure during test are solved.The failure stresses were measured for dry and water/CO2 containing fine sandstone samples.To verify the performances,repeatable verifying test,fracture test in two-phase fluids and fracture tests in different loading paths are conducted.Test results show that the apparatus exhibits performances with excellent temperature and pressure stability,high control accuracy and strong repeatability.The apparatus can serve as a new tool providing scientific data for validating failure criteria,especially in tensile regime for two-phase fluid bearing rocks.