Optimizing your model

Diagnostic maps(found under Bubble Maps in the Property Manager) can help you optimize the performance of your model. These diagnostic maps can highlight areas with operational issues, or can be used to locate areas where potential exists to increase deliverability. The following sections discuss how the information provided by diagnostic maps can help you optimize your gathering system to maximize production and minimize operational costs.

Pressure distribution map

A pressure distribution map is used to see the calculated pressures along the gathering system. Large pressure ranges suggest that various stages of compression and or high pressure losses within pipelines are present. You can customize the pressure distribution range for easy identification of wells operating outside of desired ranges.

Pipeline pressure loss calibration map

A pipeline pressure loss calibration map shows the difference between the measured pipeline pressures (set in Wells > Well Editor > Well Options) and calculated pressures at each of the wells.

Two patterns of pressure loss may be visible: step change losses or systemic losses.

Type of loss Visual cue on the map Signifies Corrections
    Step change loss     The color of the pressure bubble shows an increase or decrease at a certain location. This difference remains the same from that location either upstream or downstream.
       If measured pressure is less than calculated pressure this could be a data entry problem.
    Confirm the following:
  • suction pressure at compressors and pumps
  • gas / liquid ratios
  • disabled pipelinks
  • pipeline diameter values
    Step change loss     If measured pressure is greater than calculated pressure, then field pressure losses are not accounted for.
  • check the pipeline velocity to determine if the losses are due to liquids or obstructions
  • check field conditions to make sure losses are not at risers or facilities but in the pipelines
  • if the loss should be included in a present or future forecast, add a pressure loss facility; add a fixed pressure loss facility for liquid related pressure loss and a variable pressure loss facility for friction related losses
    Systemic loss     Pressure loss differences keep increasing as you progress past a certain point in the gathering system. This is displayed on the map by the bubble colors becoming warmer and warmer.     The system:
  • was modeled using single phase when it should have used multiphase
  • has unaccounted for fluids, such as: missing liquid rates, or 3rd party production
  • has missing elevation data
    Confirm or correct the following:
  • use a multiphase correlation
  • compare calculated delivery rates vs. measured rates at delivery points, compressor stations, or pumps
  • enter required elevation data

Gas and water line difference map

The purpose of this map is to show if forecast gas line pressures fall below required water line pressures. In gas systems, you need to make sure that the separator pressure is high enough to push fluids through the pipeline. To validate gas and water line differences, make sure that measured water rates are accounted for.

Well drawdown map

A well's drawdown map is used to quickly identify wells that are not producing at their maximum potential. Generally a 75% drawdown is an optimum operating range. Wells falling below this operating range can indicate potential for increased production.

Well uplift map

A well's uplift map displays the ultimate uplift potential for wells that have been defined using a deliverability model. Cooler colors indicate little uplift potential. Warmer colors indicate larger delivery rate increases are possible, if wellhead pressure is reduced.

Frictional pressure loss map

A frictional pressure loss map can quickly identify restrictions in pipeline capacities resulting from frictional pressure losses. For this link map, you need to customize a frictional pressure loss range that reflects hardware used in the field.

Warmer link colors indicate greater frictional pressure losses, and thus reduced capacity available in lines. This may indicate: undersized pipelines, a potential requirement to twin lines, or an inability to increase rate without causing operational issues. Cooler link colors indicate lines have capacity available due to low frictional pressure losses. This may be an indication of oversized pipelines and therefore the potential to increase the rate in those pipelines.

Gas velocity map

The gas velocity map displays the average gas velocity in each segment of the pipeline. Warm colors indicate faster velocities, cool colors, slower gas velocities. Low gas velocities coinciding with elevation change can indicate the possibility of stagnant liquids. If there is a difference between measured and calculated pressures (pipelines pressure loss calibration map), and gas velocities are low, then stagnant liquids are likely. Low gas velocity and Turner critical velocity maps together can identify the potential for liquid loading.

Delta pressure map

The delta pressure map displays the change in pressure between two nodes connected by a link. This map can be used to identify pipelines with significant pressure losses. Warmer colors indicate a large pressure loss between nodes, while cool colors indicate a small pressure loss. Large pressure changes along lines may indicate the need for additional compression, or that frictional and hydrostatic losses are limiting field delivery rates.

Turner critical velocity map

The Turner critical velocity map displays whether the current velocity in the pipeline segment is above or below the Turner critical velocity. Pipes with red colored links indicate areas where velocities are likely lower than that required to move liquids.

Delta Erosional map

The delta erosional map displays the difference between erosional velocity and gas velocity. This map can be used to identify pipelines with gas velocity approaching erosional velocity. Blue colors indicate a small difference between erosional velocity and gas velocity, while orange-to-red colors indicate a large difference. Small velocity deltas along links may indicate a risk of line erosion.

Note:    The erosional velocity constant used to calculate erosional velocity is set under the Properties menu, Defaults.