Water Management in a Closed Loop - Problems and Solutions at Brage Field

Abstract

Abstract Brage field offshore Norway is producing off plateau at 8500 Sm3/d oil. Associated daily produced water rates are in excess of 16000 m3. Following a change in injection scheme from seawater to aquifer water in 1997, two water supply wells were drilled and completed in the Utsira reservoir. Artifical lift from Utsira was achieved by installation of Electric Submersible Pumps. In parallel, the topside system was upgraded to facilitate complete PWRI (Produced Water Reinjection) in the Statfjord sandstone reservoir. The Utsira aquifer, located 600 m below seabed, has showed excellent properties with respect to productivity and deliverability. ESP equipment installed in A-24 and A-29 has had a continuous improvement in reliability since 1998. Topside, PWRI has resulted in wear on the injection pumps as a consequence of high particle content. Corrosion has lately been detected in the Utsira water producers, injection flowlines and 3 injection well tubings. Sulphate scaling resulting from early seawater injection has been moderate at Brage. No problems associated with H2S have been seen following the change in water management philosophy. Carbonate scale in the upper tubing is successfully removed by a new acid deflection tool run on wireline while bullheading HCl. Bullhead squeeze treatments is utilized to control further scale buildup. The closed loop approach to water handling at Brage has proven environmentally favourable, and has prevented the discharge of 9 500 000 m3 produced water to sea. Introduction The Brage Field is located in the Norwegian sector of the North Sea and is operated by Norsk Hydro. Production commenced in September 1993 from five predrilled wells tied back to the steel jacket platform. The two main reservoirs, Fensfjord and Statfjord, are located at appx. 2100 and 2300 m TVD and consists of Jurassic age sandstones. One well has been drilled and completed in the Sognefjord reservoir, located in the north-eastern part of the field. The platform is equipped with a two stage separation system incorporating gas compression/export facilities to Statpipe and oil export via Oseberg Field Centre. Water injection is the main drive mechanism at Brage. A WAG-scheme was implemented for several of the Fensfjord flank injectors shortly after field startup.