Investigation of pressure wave propagation and attenuation characteristics in wellbore gas-liquid two-phase flow

Pressure waves have many important applications in the oil and gas drilling engineering field. This paper aims to discuss the propagation and attenuation of pressure waves transmitted in wellbore gas-liquid two-phase flow. In this study, a mathematical model is proposed that estimates the pressure wave propagation and attenuation in wellbore two-phase fluid flow. The model is based on a two-fluid model and considers the interactions between two phases, wall shear force, and gravitational effect. The wave speed and attenuation coefficient are calculated and compared to previous experimental results. The comparison of the results shows satisfactory compliance. Based on the model, the effects of void fraction, angular frequency, system pressure, and temperature on wave speed and attenuation coefficient are discussed. The results indicate that pressure wave dispersion is obvious in wellbore two-phase fluid flow. The wave speed first decreases with an increase in the void fraction and then exhibits a flat transition. Next, the wave speed increases notably after the void fraction exceeds 90%, showing a characteristic U-shape curve. The pressure wave attenuation shows the inverse variation trends than that of wave speed. Lower angular frequency and temperature, and higher system pressure are observed to benefit the transmission of a pressure wave in wellbore two-phase flow. Furthermore, the propagation and attenuation behaviors of pressure waves in wellbore two-phase flow during aerated underbalanced drilling are discussed as a case study. The pressure wave attenuation rises with respect to the gas injection rate. The amplitude of the pressure wave at the wellhead decreases to 8.1% of the initial value when the gas injection rate reaches 13 m(3) min(-1). This wave amplitude is almost undetectable during drilling operations. This is the cause of failure for mud pulse telemetry in aerated underbalanced drilling. Stronger attenuation is observed when the pressure wave travels close to the wellhead. (C) 2016 Elsevier B.V. All rights reserved.