The Heidrun Field - Development Overview

ABSTRACT Heidrun an oil and gas field lying in 345 meters of water off the coast of Norway. has been developed using the world's first concrete Tension Leg Platform (TLP). The TLP substructure. comprised of the Hull and Module Support Beams (MSB'S) is built of high strength lightweight aggregate concrete. The MSB concept eliminated the need for a module support frame and enabled the modules to be mated will the SUbStIUCIUI＿Cby ballasting and de ballasting, without the use of expensive heavy Lift vessels. The TLP topsides consists of five main modules and a drilling rig. The design concept of these large modules as self contained elements enabled them to be pre-commissioned to a Large extent at the fabrication yards, prior to load out. Sixteen tubular steel Tethers anchor the platform to four concrete Foundations on the seabed. These Foundations were towed to the field and Lowered into position by ballasting. again without the use of heavy lift vessels. Installation of a sub sea Well Template enabled the first wells to be pre-drilled and pre-completed before the platform was towed to the field. enabling an early production start after platform instillation. TIVO oil export pipe-Lines and one gas export line were completed onshore then MCI towed to the field using the controlled depth tow method. Titanium is used for the platform Drilling Riser, providing the same strength as conventional materials but with considerable weight savings. Produced oil from Heidrun is offloaded directly into shut ankles, without intermediate storage, using the innovative Submerged Turret Loading technology. THE HElDRUN FIELD Introduction. This paper first describes the main parameters of the field and the phases of the project development from discovery to first oil. The main components of the platform, sub sea development and export system arc described. The project organization is outlined. A description of the pre-operations drilling program is given. Construction of the concrete hull, fabrication of the topsides modules and marine operations. including module transportation and platform installation, arc reviewed. Emphasis is placed upon the novel aspects ofthc field development. Field Location and Environment, Heidrun, which is an oil field with associated gas and gas cap, is located under the stormy waters of the Norwegian Sea, 175 kilometers from the coast. and covers an area of 38 square kilometers (9,000 acres). Water depth at the field is 345 meters. Fig. 1 shows the field location. Discovery. The License for Conoco to explore and appraise the Heidrun field was awarded in 1984 and the first WCII was drilled in August of that year. The first well was a dry hole but the second WCII. completed in June 1985. encountered a 137 meler oil column in the Lower Jurassic Tile Formation, In addition. the upper part of the Tile Formation and the Middle Jurassic Fangst Group were found to be gas bearing, Seven more wells drilled on the block to confirm and delineate the field. Flow rates from the tests merged up to 930 m3 (6,000 barrels) per day.