Summary
Low-damage fracturing fluids are normally used for better fracture-dimension
confinement and lower residue. This leads not only to longer fracture lengths,
but also to higher fracture conductivity. Slickwater fracturing technology,
developed in the 1980s, is less expensive than gel treatments. Fluid and
proppant volumes can be reduced, and treatment flow rates can be increased
significantly. When compared to conventional gel treatments, slickwater
fracturing can generate similar or better production responses.
In frac treatments, slickwater is pumped through straight tubing (ST) and
coiled tubing (CT). As a result of secondary flow, frictional pressure losses
in CT are higher than in ST. Determining these losses is of the utmost
importance for successful treatments. Customarily, laboratory-generated flow
data are used to develop correlations to predict frictional pressure loss of
fluids flowing in ST and CT. These correlations are then, without verification,
applied to field applications, which employ much larger conduit sizes.
The present study is aimed to experimentally investigate the hydraulic
properties of a commonly used drag reducer--Nalco ASP-820--in larger tubing
sizes. This is a modified partially hydrolyzed polyacrylamide (PHPA).
Previously, we reported flow data gathered employing ½-in. ST and CT (varying
curvature ratio) and the correlations developed to predict frictional pressure
losses of fluids in ST and CT. In this investigation, the large-scale flow data
acquired from 200-ft ST and 1,000-, 2,000-, and 3,000-ft, 1½-in. CT, and
1,000-ft 2⅜- and 2⅞-in. CT, are compared with the predictions from the
correlations developed from ½-in.-pipe data. The effects of shear intensity,
shear duration, and pipe roughness on flow properties of the ASP-820 fluid are
also investigated.
Results show significantly lower drag reduction in CT than in ST because of
secondary flow caused by the CT curvature. Polymer degradation because of shear
(shear intensity and duration) and/or tubing roughness can reduce drag
reduction significantly. The results are discussed in light of a recently
developed "drag-reduction envelope" to evaluate the drag reduction
characteristics of slickwater fluid in ST and CT.
© 2009. Society of Petroleum Engineers
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History
- Original manuscript received:
13 September 2008
- Meeting paper published:
19 January 2009
- Revised manuscript received:
16 March 2009
- Manuscript approved:
31 March 2009
- Published online:
22 December 2009
- Version of record:
1 March 2010
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