Gas Lift Journey to Maximize the Asset Value in Platong Field, Gulf of Thailand

Abstract

Abstract Operating Platong field in the Gulf of Thailand (GoT) is challenging because of the small compartmentalized reservoirs in the fluvial deposition environment. As the completion strategy has to be low cost in order to achieve the economic hurdle rate and the initial strategy is to develop to be a gas field, a lot of existing oil wells do not have the artificial lift system in place. Without artificial lift, most of the oil wells usually cease flowing in 2–6 months. Therefore, the artificial lift is crucial to prolong the well life in Platong. Gas lift currently plays a very important role in Platong field. With the continuous initiation and operation improvement, production from Platong gas lifted wells has been gradually increasing from 10% in June 2008 to 50% of total field production in June 2011. The subsurface challenge for gas lift mainly involves with the effort of cost reduction. Drilling and completion improvements from 2-trip to mono-trip gas lifted completion in 2008 reduces a rig time by ~1 day/well (from total ~7 to ~6 days/well). Converting the existing producers that are not equipped with gas lift mandrels was initially undertaken by installing coiled tubing gas lifted assemblies. This method was subsequently replaced with the installation of slickline run straddle pack-off gas lift assemblies in 2010 at a cost saving by -73%. In terms of the production operation aspect, proper gas lift candidate selection process, excellent collaboration between office and offshore are the key components for the success. Beyond the gas lift injection rate optimization, the surface challenge is mainly related to the optimization of the gas lift sources from the back pressure reduction systems, i.e. Remote Compressor (RC) and the mobile Well Unloading Unit (WUU). The RC functions in both back pressure reduction and providing the high pressure gas lift gas to the producers. Several efforts have been put on the RC unit optimization and modification to maximize gas lift rate, for example the RC inter-stage is modified to increase gas lift rate from 2 to 5 MMscf/d which resulted in the oil increase of +500 bopd/platform. In May 2011, the modified WUU that can provide high pressure gas lift was implemented to revive the platform that does not have the RC to provide gas lift with the incremental oil of +1,000 bopd/platform. In Q2 and Q4 2011, four main gas lifted platforms are scheduled to commence the gas lift injection from a gas supply pipeline, where the gas source is supplied from the Central Processing Platform (CPP). We walk away from the gas lift from RC due to the limited gas reserves on those four platforms. With the continued gas lift completion and operation innovations in both surface and subsurface, proper working process in place, sufficient gas lift trainings for all personnel, and excellent collaboration between office located subject matter experts (SMEs) and offshore production operators, gas lift could significantly prolong the well life and certainly increase the recovery; as a result, enhance the asset value.