The Changing Role of Reservoir Engineering in the Airlie Project

Abstract

Abstract This paper discusses the changing role of reservoir engineering in the various stages of a marginal development offshore Western Australia known as the Airlie Project. The project, which comprises three thin oil column fields, South Pepper, North Herald and Chervil, was made possible through an innovative approach to development. This included the pioneering of horizontal well technology in Australia, the use of a jackup drilling rig as a production platform and the application of monopod and minimal structure concepts for wellhead Support. Specifically the paper addresses the use of horizontal and high angle slant production wells in marginally economic thin oil columns, and discusses the successes, the failures and the general philosophy applied to the development. The results of several numerical reservoir Simulation studies are used to illustrate these aspects. The evolution of the role of reservoir engineering is followed from the feasibility stage through the initial development, to the mature stage including two infill drilling programs in South Pepper, and finally to the future twilight phase of the project. The applicability and reliability of reservoir modelling at various points in the project life are reviewed. A critical feature of the reservoir management of thin oil column reservoirs has been the almost continuous remapping process as additional data was acquired and the necessity for detailed geological flow unit description. A multi disciplinary team approach has therefore been of great importance in achieving an integrated reservoir management plan. Foremost in the development success of marginally economic fields such as those in the Airlie Project, has been the application of new technology including MWD logs, gas wetness ratios and modern Simulation tools. The use of reservoir Simulation has been instrumental in the optimisation of horizontal well placement within the thin oil columns which are continually rising as gas caps become depleted. It was concluded from reservoir Simulation studies and appraisal drilling that future horizontal wells drilled in these thin oil columns should be placed as high in the remaining oil column as possible.