Page 205 - Shale Shakers Drilling Fluid Systems

188 SHALE SHAKERS AND DRILLING FLUID SYSTEMS

Sample Calculation:

For 800 gpm of a 12.0 ppg drilling fluid flowing through a 6-inch diameter. Schedule 80 pipe, the fluid has a PV = 20 cp.
2
and a YP = 18 lb/100 ft . Find the Reynold's number.
The pipe data in Table 11-2 shows that the pipe's inside diameter is 5.76 inches.
The velocity of the fluid in the pipe would be:

The 600-rpm Fann reading would be 58 (the 300 rpm reading would be 38). The apparent viscosity would be 29 cp.

This value is larger than 4000, so this flow is turbulent.

This equation is correct for either laminar or where d = Pipe inside diameter, in.
turbulent flow.' It calculates the head loss of a v = Velocity of liquid, ft/sec
constant-density fluid flowing in a straight, constant- MW = Fluid density, pounds per gallon
diameter pipe. p = Viscosity of the fluid, centipoise
For laminar flow conditions, or Reynold's num-
ber (R e) less than 2000, the friction factor (f) is: For laminar flow, R e < 2000; and for turbuler
flow, R e > 4000.
Viscosity for Newtonian fluids can be easil
defined if the pressure and temperatures are knowr
For turbulent flow conditions, or Reynold's num Drilling fluids, however, are usually shear-thinninj
ber (R e) greater than 4000, the friction factor is: and the viscosity decreases as the shear rate ir
creases. Drilling fluid viscosity also depends on th
pressure and temperature. If the flow properties c
a drilling fluid are known as a function of shea
rate, the viscosity for the appropriate shear rat
The head loss (H) for fluid with a viscosity, p, can be used to calculate head loss in a pipe systerr
and a flow rate, Q, gpm, in a pipe with a diam- In lieu of this, the apparent viscosity can be usec
eter of D, inches, would be: This value, in centipoise, is calculated by dividin
the 600-rpm Fann reading by two. This is the vis
cosity of the drilling fluid at 1022 sec~' shear rat<
After determining the Reynold's number an
flow regime, the head loss per unit length of pip
where L e = Equivalent length of pipe, ft may be calculated from the equation:

Elbows, valves, swedges, and changes in direction
of piping can be expressed in equivalent lengths
of straight, smooth pipe (Table 11-I). Reynold's
number may be calculated from the equation:
To calculate velocity, v in ft/sec, the following
equation can be used instead of using the conver-
sion factors. Here, Q is in gpm and d is the inside
pipe diameter in inches:

1
The velocity head is the vV2g part of this equation. This should
be recognizable from the kinetic energy equation: KE = m(vV2g).