In offshore environment, it is common for operators to develop the field with high deviation wells, in order to optimize both field development cost and reservoir drainage. Well intervention for high deviation wells can be difficult, as specialized tools are needed for well intervention in high deviation wells. As such, high deviation wells normally have well issues after 5 years of production. In Field B, 4 high deviation wells were having unhealthy well lifting, well lifting diagnostics and optimization was needed in order to sustain well and field production. CO2 Tracer Survey was selected for well lifting diagnostics, and all wells were found to have some degree of well lifting issue. With the result from CO2 Tracer Survey, gas lift optimization was conducted, and well was restored to its design condition.