Flow Regimes - Cased-Hole Log Analysis and Reservoir Performance Monitoring - page 50

If a logging tool, such as a spinner flowmeter, takes a measurement of fluid
velocity in the center of the pipe, then it holds that some corrections must be made
before converting that velocity to a volumetric flow rate. The normal practice is to
take 85 % of the fluid velocity in the center of the pipe as being the superficial
velocity. This is based on the assumption that flow is turbulent. The kind of flow that
will occur is predicted by use of the Reynolds number, N , which is defined as:

N d =r/,

where:

ˁ = fluid density in g/cc
V = superficial velocity in cm/s
d = inside pipe diameter in cm
ʼ = fluid viscosity in poise

Reynolds numbers in laminar flow are less than 2,000. In turbulent flow, they are
greater than 4,000. Figure 4.2 shows a plot of flow rate vs. Reynolds number for a
number of pipe IDs and viscosities.

Fig. 4.1 Velocity profiles for laminar and turbulent flow—Courtesy Baker Hughes