THE YAMMADERRY AND COWLE SMALL OFFSHORE FIELD DEVELOPMENTS

Abstract

The Yammaderry and Cowle oilfields are located 22 km north-west of Onslow, Western Australia and are two and five km respectively from the Saladin oilfield. With estimated crude oil reserves of 1.6 and 2.3 MMBBLS respectively these developments are considered small.

A development strategy was formulated to provide minimum facility structures and to take maximum advantage of the very competitive design and construction capabilities being offered locally. Development costs were minimised by using the existing Saladin processing facilities on nearby Thevenard Island and by sharing mobilisation costs of major construction and development plant items.

The offshore monopod structures were designed to withstand cyclonic wind and wave conditions while supporting minimal production equipment and acceptable access structures.

The main advantages of these structures are that they can be fabricated in any competent heavy fabrication shop, well removed from the site, and can be transported easily by road and rig tender vessel to the installation site. Installation is generally carried out by the jack-up drilling vessel mobilised to drill the production wells.

The offshore pipelines were designed as paired bundles to accommodate multiphase product flow and gaslift supply and to provide greater confidence in achieving on-bottom stability.

Since the development strategy embraced two independent paths, these being structure/well development and offshore pipelay, the risk of claims due to late delivery of either structures or line pipe was removed. The success of the project was kept independent of any one major component of plant and throughout all phases of the project, realistic contingency plans and procedures were available.