Analysis of Development Methods for Gravel Envelope Wells - 15
With a double swab the effect of undersized swabs on clearance must
be compensated by increasing pump capacity to offset leakage past the swabs. As
discussed in Section 3.2, the effect of providing flange clearance is the same as
introducing an orifice that permits flow to bypass the swab. With a ¼-inch
clearance on the swab diameter in a 14-inch diameter well it was estimated that 10 ft
of head would produce a flow of about 600 gpm. Thus with two flanges an extra 1200
gpm is required. Adding this to the 666 gpm required for flushing the gravel gives a
total of about 1900 gpm.
We can summarize the previous discussion of the various methods in
terms of the tangential velocities induced at the filter pack/ formation interface to
develop a typical 14-inch diameter well with 28-inch diameter filter pack.
