Installation of Annulus Cement Plugs Using Perforation, Wash and Cement Technique, a Lookback from a First for Australia

Abstract

Abstract The Gorgon Foundation Project (GFP) development comprises of the Gorgon and Jansz-Io gas fields located in offshore Western Australia. To maintain gas supply, the Gorgon Stage 2 (GS2) project will expand the existing infrastructure with additional subsea production wells. The Gorgon Stage 2 (GS2) well architecture is designed to deliver a 7 5/8 in. tubing × 7 in. production liner Cased Hole Orientated Perforation completion (CHOP). An unsuccessful production liner primary cement job resulted in an area of uncemented wellbore -casing annulus and a sand containing mobile water exposed. This led to the unresolvable uncertainty of water crossflow into adjacent produced sands. Under the current flow assurance restrictions, the risk of produced water could reduce production rates or require the well to be shut-in. To mitigate water flow potential, cement plug annulus impediments (baffles) were installed. The objective of these plugs are for reservoir management, not abandonment barrier plugs. This allowed an optimized scope for verification and contingency operations planned and executed. This paper provides an insight into the collaborative efforts made by the Subsurface, Drilling and Completions (Wells) teams and Service Partners to plan and successfully execute two (2) Perforate, Wash and Cement plug jobs. Operations include the use of Tubing Conveyed Perforations (TCP) and Closed Loop Cup Type Wash and Cement tool, a first for Chevron in Australia. The cement plugs were deployed from a semi-submersible in ~220 m of water and placed at depths of ~5,700 mMD and ~5,500 mMD respectively, at inclinations of 60° and in high static bottom hole temperatures up to ~157°C. The key challenges and lesson are discussed including planning to optimize swab cup integrity in high temperature operations.