Studies of Drag Reduction Conducted over a Broad Range of Pipeline Conditions when Flowing Prudhoe Bay Crude Oil

Abstract

The effects of solventviscosity, bulk velocity, and pipe diameter on drag reduction have been investigated in order to ascertain the feasibility of utilizing polymer drag‐reducing additives to increase the flow rate in the Trans‐Alaska Pipeline. Laboratory screening studies were performed in 1‐ and 2‐in. diam flow loops to determine the best commercially available additive for the application. Field tests in a 14‐in. crude pipeline and in the 48‐in. Trans‐Alaska Pipeline confirmed the material's effectiveness in large‐scale applications. This research program has resulted in the use of drag‐reducing additive in the Trans‐Alaska Pipeline as a temporary replacement for unconstructed pump stations. The effect of additive concentration was investigated over a range of 5 to 25 ppm. The crude‐oil flow conditions that were studied included solventkinematicviscosities of 9 to 50 mm 2 /sec (9 to 50 cs), Reynolds numbers of 4000 to 300000, wall shear rates of 100 to 2000 sec −1 , as well as inside pipe diameters from 2.66 to 119.4 cm (1.05 to 47.0 in.). The drag‐reduction results have been correlated based on an extension of a theoretical model available in the literature. The functional form of the model requires a knowledge of the wall shear rate, the friction factor, and the additive concentration as independent variables.