Identification of GL underperforming wells is a crucial step because early detection of such wells may improve their economics. Gas lift monitoring package includes the following workflows:
- Ranks gas lift wells by underperformance
- Performs stability analysis
- Identifies multi-point injection detection
Ranking: Gas Lift Wells Underperformance
Identification of GL underperforming wells is a crucial step because early detection of such wells may improve their economics. The current workflow screens all the gas lifted wells based on their Target Injection Differential and Well Performance Factor. It is calculated as follows:
Target Injection Differential indicates how much the casing head pressure and the well head pressure are different. It is calculated as follows:
Target Injection Differential =
(Casing Head Pressure – Well Head Pressure) / Casing Head Pressure
Well Performance Factor is indicative of the GL performance. It is estimated as follows:
Well Performance Factor = GL Injection RT / (Produced Oil + Produced Water)
Stability Analysis: Gas Lift Optimization
In order to evaluate gas lift wells stability, two explicit criteria for stability can be calculated: inflow response (“quantiﬁes stability as a consequence of the inﬂow responses of injection gas and reservoir ﬂuid inﬂow”) and pressure depletion response (“quantifies stability as a function of the depletion of the casing pressure”). A stability map can be generated giving boundaries of stable and unstable condition.
Inflow response: By these criteria, the stability is promoted by high gas injection rate and small injection port.
SIPOC diagram of Gas Lift Stability
Gas Lift Performance
Multi-point Injection Surveillance
Calculating theoretical gas lift injection rate (using Thornhill-Craver or TULSA generic algorithm) across operating valve and comparing it with the measured rate can be an indicator of multipoint injection issue. If the calculated and measured rates are differing greatly, then you might have multipoint injection or plugged, eroded upper valve, etc.
Stability analysis and injection rate monitoring