Title: Effects of Coiled Tubing Shear History on
the Rheological and Hydraulic Properties of Fracturing
Fluids
Author(s): S.N. Shah and R. Subramanian, The
University of Oklahoma
Presentation: SPE 2nd North American Coiled Tubing
Roundtable
Location: Montgomery, Texas USA
Date: April 1-2, 1997
Abstract: Coiled tubing shear history effects on the
rheological and hydraulic properties of various fracturing
fluids are investigated using the experimental equipment
available at the Fracturing Fluid Characterization Facility
(FFCF), located at the University of Oklahoma. The primary
investigation includes tubing curvature effects on the
frictional pressure losses using various lengths of coiled
tubing and on the fracturing fluids apparent viscosities,
over a range of selected linear and crosslinked fluids,
using a unique High Pressure Simulator (HPS), capable of
operating at elevated temperatures and pressures. To ensure
a comprehensive understanding of the curvature effects on
the rheological and hydraulic properties of the selected
fracturing fluids, both coiled and straight tubing are
investigated. The results show that coiled tubing curvature
increases the frictional pressure losses for fluids such as
water, linear guar gum and Hydroxypropyl guar (HPG, and
borate-crosslinked guar and HPG fluids.) Also, the study
shows that frictional pressure losses within a coiled tubing
are dependent of coiled tubing shear history for
borate-crosslinked HPG gels and are independent of coiled
tubing shear history for borate-crosslinked guar gels. On
the effects of coiled tubing shear on the rheological
properties of the fracturing fluids, the study indicates
that apparent viscosities of borate-crosslinked gels are a
function of shear history, pH, and temperature. Furthermore,
the results show that for certain fluids, there exist an
optimum pH where shear history does not affect fluid's
apparent viscosity.