Title: Experimental Investigation of Frictional
Pressure in Coiled Tubing
Author(s): I. Azouz, S.N. Shah and P.S. Vinod, The
University of Oklahoma and D.L. Lord, Halliburton Energy
Services
Presentation: SPE Eastern Regional Meeting
Location: Columbus, Ohio USA
Date: October 23-25, 1996
Abstract: This paper presents an experimental
investigation of tabular frictional pressure loss in coiled
tubing and straight sections of seamed and seamless tubing.
Fluids investigated include water, linear guar gum and
hydroxypropyl guar (HPG), and borate-crosslinked guar gum
and hydroxypropyl guar, under conditions typically
encountered in many coiled tubing field applications. The
equipment used includes a system of one 1000 ft and two 2000
ft coiled tubing reels that can be arranged to provide total
coiled tubing lengths of 1000, 20900, 3000, 4000, and 5000
ft. The system also includes straight sections of seamed and
seamless tubing with the same nominal diameter (1 ¸ in.) and
wall thickness (0.156 in.) as that of the coiled tubing. The
investigation focuses mainly on the effects of coiled tubing
curvature, tubing seam, fluid pH and shear history on
frictional pressure loss. Results obtained with water
indicate that curvature as well as the seam inside the
coiled tubing significantly affect the frictional pressure
losses. Results obtained with various polymer solutions and
gels, however, suggest that tubing curvature has a more
significant effect on the frictional pressure losses than
the tubing seam. Moreover, it is observed that for
borate-crosslinked HPG the pressure gradient is dependent on
both the fluid pH and the length of coiled tubing across
which it is measured. However, for borate-crosslinked guar
gum the pressure gradient is a function of pH and is not
very sensitive to the length of tubing along which it is
measured.