What is annular gas flow?
What is annular gas flow?
1. n. [Drilling] A flow of formation gas in the annulus between a casing string and the borehole wall. Annular gas flows occur when there is insufficient hydrostatic pressure to restrain the gas. They can occur in uncemented intervals and even in cemented sections if the cement bond is poor.
What causes annular flow?
Annular flow occurs at high velocities of the lighter fluid, and is observed in both vertical and horizontal wells. As the velocity increases, the film may disappear, leading to mist flow or emulsion flow. When the interface between the fluids is irregular, the term wavy annular flow may be used.
What coefficient does determine the flow regime?
The flow regimes vary according to: Velocity, viscosity, pipe diameter, roughness, density. If Re < 2000 the flow regime is laminar, we use the formula of Poiseuille laminar flow to find the coefficient of major losses.
How do you calculate Reynolds number flow rate?
The Reynolds number (Re) of a flowing fluid is calculated by multiplying the fluid velocity by the internal pipe diameter (to obtain the inertia force of the fluid) and then dividing the result by the kinematic viscosity (viscous force per unit length).
Does Reynolds number apply to gases?
The important factor on the Reynolds number is the gas density ρ, which is proportional to the atomic mass of gas species. Therefore, the light atom gas of He has much lower Reynolds number than those of other gases of Ne and Ar, when the value of (Q/rD) is fixed.
How do you calculate flow regime?
The flow regime depends on the boundary condition, and it can be identified by the rate of change in pressure with time. The steady state flow regime corresponds to a system in which the mass flow rate is constant everywhere, and pressure is constant with respect to time (dP/dt = 0).
How do you calculate flow in a pipeline?
How do you calculate gravity flow through a pipe? First use the Hazen-Williams equation to find the velocity of the fluid: v = k × C × R0.63 × S0.54 .
What is 3phase flow?
Origin of the Water Phase Three-phase flows of gas and two liquid phases ( ) often occur during production of oil. A typical oil and gas reservoir contains gas, oil and water. As oil is extracted from the reservoir, the formation water beneath may flow into the well, due to its easier motion through the rock pores.
Which type of flow is controlled by Reynolds number?
laminar flow occurs at low Reynolds numbers, where viscous forces are dominant, and is characterized by smooth, constant fluid motion; turbulent flow occurs at high Reynolds numbers and is dominated by inertial forces, which tend to produce chaotic eddies, vortices and other flow instabilities.
What is slug fluid?
The word slug normally refers to the heavier, slower moving fluid, but sometimes to the bubbles of lighter fluid. There are also small bubbles within the liquid, but many of these have coalesced to form the large bubbles until they span much of the pipe.
What is annular gas-liquid flow?
Annular flow is a flow regime of two-phase gas-liquid flow (see gas-liquid flow ). It is characterized by the presence of a liquid film flowing on the channel wall (in a round channel this film is annulus-shaped which gives the name to this type of flow) and with the gas flowing in the gas core. The flow core can contain entrained liquid droplets.
What is annular flow?
Annular flow is a flow regime of two-phase gas-liquid flow (see gas-liquid flow ). It is characterized by the presence of a liquid film flowing on the channel wall (in a round channel this film is annulus-shaped which gives the name to this type of flow) and with the gas flowing in the gas core.
How do you calculate liquid flow through an annulus?
Equations for the Liquid Flow Through Annulus Calculator. The Darcy Weisbach equation for flow in an annulus is: h L = f(L/D H)(V 2/2g), with the parameters in the equation as follows: h L is the frictional head loss for flow of a liquid at average velocity, V, through an annulus of length, L, and hydraulic diameter, D H .
What is the true volumetric gas concentration of annular flow?
The true volumetric gas concentration (void fraction) of the annular flow ε G, determined as a fraction of the cross section occupied by the gas phase, is high and, as a rule, exceeds 75-80%. In horizontal channels the film thickness is non-uniform around the channel perimeter due to gravity.