厚壁圆筒式两相流体致裂仪研制

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

两相条件下岩石强度是重要力学参数,是CO2地质封存、油气田开发、非常规能源开采等工程中压裂增采与安全控制共性科学问题。厚壁圆筒式两相流体致裂仪的开发,可以对含有两相流体的厚壁圆筒试件施加不同内压、轴压、围压和孔隙压力的应力组合,实现两相条件下岩石拉破坏试验控制。该研究解决了试验过程中温度稳定、饱和度控制、内压和孔隙压力密封性等技术问题。为检验仪器的性能,采用某砂岩进行可重复性验证试验、两相流体条件下致裂试验和不同应力路径下致裂试验。试验结果表明:致裂仪的温度及压力稳定性好,控制精度高,试验结果可重复性强,可以为两相流体岩石拉剪破坏特性研究提供新的手段。

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.