Calculation Analysis of Pressure Wave Velocity in Gas and Drilling Mud Two-Phase Fluid in Annulus during Drilling Operations

Abstract

Investigation of propagation characteristics of a pressure wave is of great significance to the solution of the transient pressure problem caused by unsteady operations during management pressure drilling operations. With consideration of the important factors such as virtual mass force, drag force, angular frequency, gas influx rate, pressure, temperature, and well depth, a united wave velocity model has been proposed based on pressure gradient equations in drilling operations, gas-liquid two-fluid model, the gas-drilling mud equations of state, and small perturbation theory. Solved by adopting the Runge-Kutta method, calculation results indicate that the wave velocity and void fraction have different values with respect to well depth. In the annulus, the drop of pressure causes an increase in void fraction along the flow direction. The void fraction increases first slightly and then sharply; correspondingly the wave velocity first gradually decreases and then slightly increases. In general, the wave velocity tends to increase with the increase in back pressure and the decrease of gas influx rate and angular frequency, significantly in low range. Taking the virtual mass force into account, the dispersion characteristic of the pressure wave weakens obviously, especially at the position close to the wellhead.

Toward the Internet of Underground Things: A Systematic Survey

“…As the mud pulse signals propagate along the borehole, the signals are attenuated and dispersed due to under-balanced drilling mud [93]. The major sources of attenuation are the mud type, joints in the drill string, signal frequency, diameter of the string, and borehole depth [94]. Low frequency signals can be used to avoid excessive attenuation of the mud pulse signals [95].…”

A review of mud pulse telemetry signal impairments modeling and suppression methods

“…To minimize reservoir damage, the drilling mud pressure is kept high that exceeds the hydrostatic pressure and nitrogen gas is used to reduce mud density. The effect increases the drilling mud compressibility hence reducing mud bulk modulus and mud pulse propagation velocity in the drilling fluid (Lin et al 2013). Changes in drilling mud compressibility may result into serious earth formation damage which strongly affects the shape of the signal pulses and complicates the decoding process.…”

“…Drilling mud borehole boundary constraint study using mud pulse velocity continuity derived equation shows that water-based mud velocity is generally higher than oil-based mud. If gas influx is not offset in time, the unstable effect can escalate into well blowout creating severe financial losses, environmental contamination, and even potential human lives loss (Lin et al 2013).…”

A New Model for Predicting Dynamic Surge Pressure in Gas and Drilling Mud Two-Phase Flow during Tripping Operations

“…Then, the surge pressure at different depths of wellbore in tripping operations can be solved by (45). The process is repeated until the surge pressure in the whole wellbore has been obtained [37,38].…”