A prediction model for the propagation of continuous pressure waves in complex structure wells

Continuous pressure wave (CPW) is regarded as promising information transmission technology while drilling. Based on fluid dynamics water hammer theory, this study proposes a prediction model for quantitatively calculating the propagation velocity and amplitude attenuation of CPW with consideration of the compressibility of the drilling fluid and the reflection and stacking of waves in complex structure wells. The mathematical model is then validated by the experiments with water as circulating fluid in curved pipe with length exceeding 600m. The results show that, the pressure drop rate along the pipe is 8112 Pa/m, and the pressure drop of the double curved head is 7070 Pa, and the error of the simulation results is less than 13 % compared with real tests. The propagation velocity of the CPW is in positive correlation with the static pressure in the pipe. The CPW propagates with standing wave characteristics, and it is significantly influenced by the reflection and stacking in curved wells. The amplitude attenuation of the CPW could be models with negative exponential function during propagation upward along the well. The results would facilitate to clarify the application scope of certain CPW devices.