This paper was presented as part of the student paper contest associated with the European Petroleum Conference.

Abstract

An experimental study of pressure drop in pipes at high Reynolds numbers was performed to determine the friction factor of coated gas pipes. The results enable more accurate predictions of long distance gas pipeline capacity, and demonstrate the drag reduction potential of internal coating in gas wells.

The friction factor of the coated pipe was 31 % lower than in the bare steel pipe at a Reynolds number of 1 × 107. Such a reduction in the friction factor means 21 % higher mass rate at the same pressure drop if internal coating is used in a horizontal pipeline.

Simulations of flow in vertical gas wells in the offshore Troll field showed that internal coating can reduce the pressure drop significantly in high rate gas wells. A reduction in the tubing pressure drop from 18.9 bar to 16.6 bar at a production rate of 2.2 × 106Sm3/day was possible when internal coating was used. At higher rates the reduction in the pressure drop was even larger. As a result the need for compression for gas export may be reduced.

Introduction

Internal coatings for drag reduction have been used with success in gas pipelines since the 1950's. Economic studies show that the typical pay-back time for the investment in internal coating is 3 - 5 years due to improvements in pipeline hydraulics. It is well known that internal coatings reduce the friction in the pipeline and there for reduce the operating cost of compressors. In Norway 35% of offshore generated electrical power is used for gas export compressors. The use of coatings to reduce the operating cost is there for important. In addition the coatings protect the pipe wall against corrosion and reduce the need for maintenance of the pipeline.

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