PetroVisor Package
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      3. PetroVisor Package

      Gas Lift Monitoring Package

      Monitor gas lift stability and gas injection rates and detect problems related to gas lift operations.

      Usage

      Run the workflows from this package to perform the calculations. The schedules may be adapted to use different contexts.

      Details

      Gas Lift Problem Detection

      The logic tries to detect a number of events or problems related to gas lift operations. This is based on how the different measurements or signals are changing with time. Each event is given a score that reflects how strong its symptoms are, hence the likelihood that this event is taking place.
      The following problems are detected:
      • low casing pressure
      • high casing pressure
      • low gas usage
      • high gas usage
      • intermitter problem
      • high back pressure
      • well will not accept input gas
      • well flowing in heads
      • unloading problem
      • hole in tubing
      • valve hung open
      • choke sizing problem

      Gas Lift Stability

      To assess the stability of the gas lift operation, two criteria can be calculated:

      • The inflow response, which quantifies the stability as a consequence of the inflow responses of injection gas and reservoir fluid inflow
      • The pressure depletion response, which quantifies stability as a function of the depletion of the casing pressure

      The inflow response criteria is defined as:

      where:

      The pressure depletion response criteria is defined as:

      where:

      If unstable conditions are detected (i.e. the criteria are not satisfied), tag entries for the tags Inflow Response Unstable or Pressure Depletion Response Unstable are created.

      Gas Lift Performance

      The performance of the gas lift is assessed. If unfavorable conditions are detected tag entries for the tag Underperforming are created.

      Gas lift performance is assessed by calculating a performance factor and target injection differential (TID):

      Performance Factor = Injected Gas / Produced Oil
      TID = (Casing Head Pressure – Well Head Pressure) / Casing Head Pressure

      Tag entries for the tag Underperforming are created if the performance factor surpasses a user defined limit, or if the TID falls below a user defined limit.

      Injection Rate Deviation

      The theoretical volumetric gas throughput of an orifice or choke is calculated and compared to measured rates. If big differences are detected tag entries of the tags Injection Rate Deviation (Thornhill) or Injection Rate Deviation (Tulsa) are created, depending on the method used to calculate the theoretical gas throughput.

      Gas Lift Well Ranking

      The well performance factor and target injection differential are used to calculate a combined gl performance score. Gas lifted wells are ranked based on this score.

      Data Requirements

      The following data is required on well level: 

      orifice efficiency factor
      injection port size
      tubing inner diameter
      injection point depth
      casing inner diameter
      tubing outer diameter
      lift gas density
      gas formation volume factor
      gas injection rate
      productivity index
      liquid production rate
      injection point tubing pressure
      injection point liquid production rate
      injection point lift gas rate
      injection point fluid density
      injection point lift gas density
      injected gas per time increment
      produced oil per time increment
      casing head pressure
      well head pressure
      discharge coefficient
      choke downstream gas pressure
      choke upstream gas pressure
      gas lift valve inlet area
      upstream gas temperature
      well head temperature
      gas compressibility factor
      flowline pressure
      gas lift intermitter state
      gas lift valve set pressure
      liquid above pump
      gas lift valve surface closing pressure