Coiled-tubing (CT) applications include drilling operations, hydraulic fracturing, well completions, removing sand or fill from wellbore, and other applications that involve pumping fluids at high temperatures and high salinity. Because of curvature effects in CT, huge pressure losses occur, limiting the maximum flow rate achieved. By adding specific chemicals known as "friction reducers" or "drag reducers" to the fluids, these pressure losses can be minimized to a great extent.
Previously, several authors have published their results for fluid flow through CT, but only a limited number of studies have been reported that relate to temperature and salinity effects on drag reduction in fluids flowing through CT.
This paper discusses an experimental study of two commonly used drag reducers--ASP-700 and ASP-820--flowing through CT with different salinities and temperatures. Both small-scale and large-scale flow loops are used in this study. The small-scale flow loop includes a 1/2-in.-outside-diameter (OD) smooth CT, while the large-scale flow loop includes 2 3/8-in. rough CT. Elevated temperature tests and salinity tests are conducted using optimum concentrations of drag reducers in fresh water, 2% KCl, and synthetic seawater.
The flow data gathered were analyzed and used to develop correlations that can predict drag reduction at different salinities and temperatures. The developed correlations show reasonable agreement with experimental data.