Haseeb Janjua, PROLIFTCO
This case study has a completion with 2-7/8” tubing in 5-1/2” casing without a packer, with 8 IPO gas lift valves in conventional mandrels with an orifice as the last valve and a chemical screen below that. A grooved plunger was used in this well in combination with gas lift to reduce liquid fall back losses and provides a solid sealing interface between the liquid slug and the gas below it. The liquid rate declined drastically after operating the well on the gas lift at 600 MCFD rate and 1050 psig injection pressure for eight months. The well did not recover after trying several combinations of lift gas volume and plunger speed. As the lift depth in gas lift system depends upon the intersection point between surface injection pressure and multiphase flowing gradient. The pressure and temperature survey with resistance temperature detector (RTD) sensor has been run till the heal of the well at a stabilized injection gas flow rate along with wellhead recorders, recording casing and tubing pressures and temperatures for the entire duration of the survey. This process will help determine the lift point by identifying the Joules-Thompson cooling effect on the temperature curve. And it will also help sense the maximum and minimum pressures if the well is heading (surging or slugging) by keeping the wireline gauges at each depth for sufficient time. The methodical approach of creating a bridge between gas lift design and pressure-temperature survey interpretation gives operational insights into what was wrong with the gas lift operating envelope. The injection pressure endpoints are generated after performing a well-delivery analysis simulation with lower bottom hole pressure (revealed from the survey). And by utilizing Winkler’s gas passage analysis, the gas rate through designed port sizes in gas lift valves can be simulated, which is required for the existing deliverability of the well. Recent changes in operating conditions were proposed after performing several simulations on downhole flowing pressure and temperature at changing injection rates to measure the decrease in production. And applying these new conditions backed by the well’s data brought the well’s production back on the curve. This case history shows the complete scheme of creating an effective lift gas troubleshooting matrix in gas lift systems from concept initiation to execution and field installation.