RESEARCH ON PRESSURE WAVE PROPAGATION CHARACTERISTICS IN THREE-PHASE FLOW DURING MANAGED PRESSURE DRILLING

In this paper, considering the virtual mass force, resistance, gas solubility and gas slip velocity etc., a model for predicting transient pressure wave velocity in oil-gas-water is established on the basis of the two-fluid equations. The influx gas is regarded as gas phase, and the influx oil is regarded as liquid phase. Parameters of liquid phase, such as elastic modulus and density, are defined as the weighted sum of the parameters of gas phase and drilling fluid. With the help of computer programming, the model is solved by the small disturbance theory and semi-implicit finite difference mathematical method. Results show that the pressure wave velocity is decreased by as much as 498.59m/s when the gas influx rate at the bottomhole increases form 0.36m³/h to 3.6m³/h. Meanwhile, the pressure wave velocity shows a slowly decreasing tendency at the same oil influx rate increase, decreasing by 19.21m/s. As the back pressure increases from 0.1MPa to 9.0MPa, the pressure wave velocity has an increasing tendency at a maximum increase of 233.15m/s. At low frequencies range, an increasing calculation error of pressure wave velocity can be observed with the increases of angular frequency by neglecting virtual mass force. At high frequencies range, the calculation error keeps constant at 10.03% when the influence of virtual mass force is neglected.