Utilizing Cost-Effective Finite Energy Gas Lift Scheme as an Alternative Mid Term Gas Lift Solution
Authors: Ishak Ahmad Firdaus , Mohd Nawi Huda 
Published: October 2023

This paper shares the success of a cost-effective finite energy gas lift scheme implemented as a measure to temporarily replace shortcomings of field gas lift system. Given the lack of full artificial lifting, Field C oil production dropped by an order of magnitude with remaining field production contribution only from naturally flowing wells. Sustainability of low-rate natural flow production continued to be at risk from slug flow, despite best efforts to optimise surface backpressure. Field C is a field with waterflooding as its depletion scheme. With gas lift system recovery anticipated to straddle more than 12 months, the team took on the challenge to find "out of the box" alternative solutions in minimizing production shortfall and avoid excessive well shut-in period which could lead to severe water crossflow from the water injection supported layers.

A variety of options were evaluated, including topside modification, conversion of existing water injection pipeline as temporary gas lift line, as well as installation of unconventional artificial lift methods to temporarily replace gas lift as an artificial lift for Field C. After extensive analysis and evaluation, the team settled for a ‘finite energy gas lift system’ – using gas produced from a deeper, high-pressure reservoir through a previously idle well as gas supply to the gas lift headers. This required installation of a new flowline to connect the well directly to the gas lift headers.

Success of the implemented ‘finite energy gas lift system’ resulted in recovery of production shortfall by 50% through idle well restoration of 12 wells. The scheme lasted a full year, through to the reinstatement of original gas lift system. Maturing a winning solution banking on an idle gas producer was not an easy feat. Uncertainties revolved around confirmation of gas lift gas source fluid type as well as sustainability of support. The scheme is also unique in a sense that unlike conventional gas lift routing to gas dehydration system, the produced gas was flowed directly to gas lift headers. This warrants a comprehensive corrosion study as well as consideration of potential costs required to replace existing Gas Lift Headers, Gas Lift Flowlines, Shut Down Valve (SDV)s that would be subject to risk of corrosion. Complete risk assessment was also undertaken to ensure seamless and safe operations given the non-conventional artificial lift approach.

A recap of the journey will reveal the challenges faced in the early stages and the importance of multi-disciplinary collaboration which help to ensure alignment in mindset which then facilitated brainstorming of options and solutions. In addition, this project will show the importance to define issue at hand holistically and establish multiple fall-back options upfront so that all relevant stakeholders can act quickly on time when and as required. Another important element that surfaced from this experience is how rigorous and continuous surveillance is a must in ensuring sustainability of the scheme.