Gas Lift Optimization in Unconventional Wells – Vaca Muerta Case Study

Abstract

Gas lift was the selected artificial lift system for Vaca Muerta formation in the Bajada del Palo Oeste field, a shale oil reservoir in Argentina. At an early stage, the main goal was to successfully overcome the design challenge of facilities and downhole installation for wells with very wide and constantly changing liquid production ranges. At a later stage, to establish an optimization methodology that could be updated at a rate comparable to production changes. Several projects were implemented for optimizing the gas lift field. First, work was oriented toward improving the prevention and mitigation of wax deposition. Several chemicals were tested and tried different ways of injecting them into the system, via capillary string and gas lift. For each stage of production, alternative treatments were determined, and wax deposition was controlled and mitigated. The need for slickline interventions was reduced by running wellbore completion with IPO valves installed instead of dummy valves. Also, efficiency was improved by changing the slickline unit to a faster one and by strategically scheduling the unit to synergize with other needs. For the optimization of gas injection, the conventional methodology of building a performance curve was used as the first option. It was found that this methodology would be useful for wells where the flow pattern remains stable or pseudo-stable, but in the case of unconventional wells, was not the best methodology to optimize the field. Optimization Curves were not concluding. Wells took so long to stabilize, that the production decline affected the results. That's when the AI-based model became relevant. In addition to global field optimization, gas optimization should be at the PAD level, not only at the well level. This paper describes the drawbacks of trying to optimize an unconventional gas lift field with traditional methodologies, and the search for innovative ways to achieve it. Finally, to share a vision of what we believe should be the state of the art of an unconventional gas lift operation: an intelligent artificial field that is fully instrumented and monitored.