Application Of Numerical Optimization To Seawater Pumping Systems

Abstract

A new project to increase the oil produced at Khurais, Saudi Arabia, was the focus of a study to determine the optimal pipeline size and pump combination for a 90.4 mile (145.5 km) long, treated-seawater transfer line between Ain Dar and Khurais. The study evaluated the supply pumps at Ain Dar, operations with and without booster pumps at Khurais, and the injection pump configuration at Khurais. The entire system was optimally designed to provide the required seawater flow of 2.14 million barrels per day (62,400 gpm) for initial operations prior to 2009 with the ability to be scaled up to the planned increased flow of 3.0 million barrels per day (87,500 gpm) 10 years later. Both first costs and life-cycle costs over 20 years were evaluated. The tradeoff of increasing initial costs to reduce life-cycle costs was examined during the study. The pipeline material considered was X-70 steel with sections welded together to form the 56 inch, 60 inch, or 64 inch diameter pipe. The study assumed the pipeline could have a maximum of two unique wall thicknesses along its entire length. The study started from a well-engineered design and through optimization techniques realized a first cost savings of $37 million (5 percent) and life-cycle cost savings of $104 million (12 percent). This cost savings could have been greater except that part of the cost reduction was used to allow the possibility for the system to be operated at a 17 percent increased capacity without any additional expenditure for construction.