Coiled Tubing Deployed ESP on the Auk Platform

Abstract

In March 1995, what is believed to be the worlds first offshore coiled tubing deployed electrical submersible pump (ESP) was successfully commissioned in well AA-03Sl on Shell U.K. Exploration and Production (Shell Expro) Auk platform in the United Kingdom's Central North Sea. The ESP provides a new and important method of artificial lift for the 21 year old Auk platform, which hitherto had relied upon downhole hydraulic jet pumps to lift approximately half of the platform's oil production. The coiled tubing deploymentproved the viability of performing future work over with or without the assistance or indeed the presence of a drilling package. The novel completion design successfully catered for the wide variety of customer requirements; Well Engineering for a rigless workover, Petroleum Engineering for reservoir access and Facilities Engineering for a specified flowline height The experience gained during this project will be a valuable input in determining the future artificial lift strategy for this platform and for other prospects in terms of performance, reliability and operating costs. Introduction The Auk Alpha platform was brought on stream in 1975, producing from 11 oil wells. The reservoir pressure is supported by a strong aquifer drive and the fields water cut has currently reached 70%, The GORs are low, at approximately 175 sef/bbl with a bubble point of 680 psi. The existing method of artificial lift is by wire line retrievable ?downhole hydraulic jet pump, However, due to the limited capacity of the permanent artificial lift (PAL) system, no more than three wells could be lifted simultaneously. It was against this background that the decision was taken to proceed with a trial ESP installation as a complementary method of artificial lift. After deciding to use an ESP pump on the Auk (the first within Shell Expro) the method of deployment had to be considered, conventional deployment versus cable or coiled tubing deployment The preliminary work showed that using either cable or coiled tubing as the means of deployment for the ESP could give rise to significant savings. Opex reduction of 20% on future workoversInstallation times reduced by 50%. Bedding reduction of circa 100 mandays per workover The use of cable or coiled tubing deployment was also an opportunity to utilize new technology whilst being aware of the risks involved capitalizing on the work already done with large bore coiled tubing by Shell Expro in the Southern North sea. An invitation to tender was prepared which invited companies to tender for the supply and installation of all components for the completion excluding the tubing hanger and wellhead. They were also required to supply a Project Engineer to work with the Shell Exploration project team to bring the proposal to fruition. After evaluation of tie submitted tenders a pump manufacturer was selected.