Propagation And Attenuation Of Pressure Wave In Wellbores Under Complex Fluids Flowing Conditions

There are many engineering problems relating to the propagation of pressure wave along wellbores in oil and gas drilling operations. Investigating of the propagation and attenuation of pressure wave in varieties of fluids in wellbores is instrumental in solving these technical problems such as mud pulses telemetry in gas drilling, aerated drilling, foam drilling and drilling with higher density drilling fluid, and the well control of oil and gas drilling in high pressure formations, which troubling the exploration and development of the large-scale low grade and deep oil and gas resources. In this thesis, the propagation and attenuation of the pressure wave in different circulating fluids along wellbore has been investigated, and the main content and some important results of this research as follows:(1) An analytical model for predicting the wave speed and attenuation coefficient of pressure wave travels through wellbore with gas fluid has been proposed. Experiments have been conducted to validate the presented model, and the results show that the theoretical wave speed and attenuation coefficient are in good agreement with the tested data. Besides, a parametric study was also performed, and the results indicate that the static pressure, angular frequency, gas mass flow rate and temperature have obvious influences on the propagation characteristics.(2) An analytical model characterizing the propagation and attenuation of the pressure wave in liquid fluids through wellbore with the effects of wall shear stress viscous dissipation, and liquid density behavior was proposed, and the model was validated against experimental results. Besides, effects of the angular frequency, static velocity, fluid density and viscosity, and bulk modulus on the propagation and attenuation of the pressure wave have been analyzed.(3) Based on the gas-liquid two-fluid model, a mathematical model predicting the wave speed and attenuation coefficient of pressure wave in gas-liquid two-phase fluids through wellbore has been proposed, and the model has been validated by a experiments using a foam fluid and traditional test data of pressure wave travelling in gas-liquid two-phase upward flow. Besides, effects of angular frequency, air void, system pressure and temperature were also discussed.(4) Based on liquid-solid two-fluid model, a mathematical model predicting the propagation and attenuation of pressure wave in liquid-solid fluid through wellbore has been proposed, and the model was also validated by traditional experimental data of sonic wave in liquid-solid two-phase medium. Besides, a parametric study was also performed to ascertain the important parameters affecting the wave speed and attenuation factor. The results indicate that the angular frequency of the pressure pulses, fluid viscosity, the volume fraction, size and density of the solid particles all exert significant influence on the pressure pulses propagation and attenuation.(5) For the technical problems of mud pulse telemetry in aerated drilling, a series of composite improved techniques and measures has been proposed to enhance the mud pulse telemetry in aerated drilling. Field test has been conducted to invalidate the proposed techniques and measures, and the results shows that the composite improved techniques and measures improve the mud pulse telemetry in aerated drilling.(6) Based on observed characteristics of the pressure wave, a rapid and reliable technique was proposed for the early detection of the unexpected gas influxes induced by encountering gas-bearing fractures in gas drilling. Field test results indicate that the technique has a shorter detection time than traditional methods.This study fully built the theoretical system of the propagation and attenuation of the pressure wave in wellbore under complex fluid flowing conditions. The researches and results laid a solid foundation for solving the engineering problems relating to the propagation of pressure wave in wellbore.