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.

The Peregrino heavy oil field is located 85 km off the coast of Cabo Frio, Rio de Janeiro. The water depth in the area is approximately 120 m. Phase I of the development comprises a FPSO and two wellhead/ drilling platforms. Production of oil started in April 2011. Statoil is operator with 60% equity and partner Sinochem holds 40%. To date, more than 80 million barrels of 14°API oil has been lifted and close to 30 development wells have been drilled. The drive mechanism of the reservoir is reinjection of produced water and pressure support from the aquifer.The new Phase II development involves a third wellhead platform tied back to the FPSO. It targets oil resources that cannot be reached from the two existing wellhead platforms. An extensive exploratory drilling program with a total of six reservoir penetrations and a detailed data collection program were undertaken in 2011-2012. From the drilling campaign the Peregrino field was found to have a large southern extension with additional 1-2 billion barrels of oil in place that could be developed. In spite of many similarities with the geology in Phase I, the new reservoirs held a number of surprises with respect to reservoir fluid (lighter oil was found) and different reservoir properties.This paper describes the experiences and challenges with developing this offshore heavy oil field from a subsurface point of view: These include appraisal strategy for optimum data collection, reservoir modelling, and impact on design parameters such as production capacities. Many of these challenges are generic for heavy oil fields: how to handle large amounts of water circulation, identifying reservoir data that are critical for field planning such as absolute and relative permeability. Heavy oil reservoirs with oil viscosity of several hundred centipois are usually high quality reservoirs with relatively homogenous sandstone, as is the case with the Peregrino field for the most part. This paper discusses critical factors in determining reservoir performance for a wide range of reservoir parameters, and includes a section on how this was implemented in the uncertainty analysis.Safe water injection into the oil zone to avoid fracturing the cap rock is very important. This has been assured both through theoretical work and data from an injection well in the Peregrino field. All producers in Peregrino are horizontal wells (with open-hole gravel packs) in order to improve productivity and drainage. Flow assurance and oil-water transport in wells and flow lines are also described. Use of inflow control valves in horizontal wells have shown potential in Peregrino and will be described in the paper.