The Effect of Viscosity on Drag Reducer Performance in Oil Pipelines

Abstract

Abstract The polymeric drag reducer CDR has been tested in the laboratory in oils with viscosities ranging from 3 to 48 cp and in product and crude oil pipelines at 3, 5, and product and crude oil pipelines at 3, 5, and 9 cp. Three regions have been identified in the drag reduction spectrum—(1) an extension of laminar flow where drag reduction increases with increasing flow velocity, (2) a transition region where drag reduction first decreases and then increases again with increasing flow velocity, and (3) a region of maximum constant drag reduction. Above a certain critical concentration of polymer, the transition from the laminar flow extension to the maximum constant drag reduction occurs without any inflection points. Below the critical concentration the extension of laminar flow increases with increasing oil viscosity. In the region of extension of laminar flow, significant drag reductions (up to 50 percent) were obtained. The laboratory data show that CDR is an effective drag reducer in all the oils tested regardless of their viscosity. The results of pipeline field tests in products and oils from 3 to 9 cp viscosity show that in the full turbulence region the performance of CDR is independent of viscosity. Introduction Drag reduction is the increase in pumpability of a fluid caused by the pumpability of a fluid caused by the addition of small amounts of additive to the fluid. It occurs only in turbulent flow. At a given flow rate, the percent drag reduction is given by (1) where delta P is the pressure drop in the pipe without drag reducer, the base pressure drop, and delta Pp is the pressure drop in the line when drag reducer is added to the fluid. Because large pressure drop reductions can be obtained with small amounts of drag reducer, drag reduction has a wide potential application within the oil industry. potential application within the oil industry. We have reported recently on a drag reducing polymer, CDR, that gave substantial drag reduction in crude oil pipelines. However, these tests were limited to relatively low viscosity fluids.