Optimization is the process whereby configured set points are adjusted automatically in an attempt to find an operating point where production from the well is maximized and wear and tear is minimized. Optimization is optional, and can be enabled or disabled on the Plunger Control Settings.
Optimization depends on having a plunger in the well. Optimization will attempt to adjust the flow conditions and shut in conditions set points to ensure normal plunger arrival. The algorithm works as follows:
At the end of a cycle, the plunger's arrival can be categorized as either early, normal, late or no arrival. The categorization is determined based on the Early Arrival Time and Late Arrival Time limits in the Plunger Control Settings group. Setting these limits correctly is vital to making automatic optimization work.
If the plunger arrival is categorized as normal, nothing is done, and the well is considered to be optimized.
For other plunger arrival types, a perfect arrival time is calculated as the average of the Early Arrival Time and Late Arrival Time limits. That means that if the Early Arrival Time is 20 minutes, and the Late Arrival Time is 24 minutes, a perfect arrival time would be 22 minutes.
For early and late arrival, the distance of the actual arrival from a perfect arrival is calculated as a percentage. That means that if the plunger actually arrived at 18 minutes (early arrival), the distance would be (22-18)/22 = 18% early. If the plunger actually arrived at 30 minutes, the distance would be 30-22/22 = 35% late. The more early or late the arrival, the greater the distance is.
No arrival is a special case of late arrival. Because a distance cannot be calculated, the distance is set at 101%, and then the same adjustments that are made for late arrival are made.
For early arrival, the flow condition that caused flow to occur (the last enabled flow condition that was accepted), is adjusted to cause the well to shut in for less time. This allows less energy to build up and the plunger to arrive later. The adjustment is fixed at 2% of the distance. That means that if the distance is 50%, the adjustment is 0.5 * 0.02 = 0.01 = 1% of the set point. The greater the distance, the greater the adjustment.
For very early arrival, where the distance is greater than 50%, the shut in condition that caused the well to be shut in is also adjusted. The condition is adjusted so that the well is shut in for less time. The adjustment is fixed at 2% of the distance. That means that if the distance is 75%, the adjustment is 0.75 * 0.02 = 0.015 = 1.5% of the set point. The greater the distance, the greater the adjustment.
For late arrival, the flow condition that caused flow to occur (the last enabled flow condition that was accepted), is adjusted to cause the well to shut in for more time. This allows more energy to build up and the plunger to arrive earlier. The adjustment is fixed at 2% of the distance. That means that if the distance is 50%, the adjustment is 0.5 * 0.02 = 0.01 = 1% of the set point. The greater the distance, the greater the adjustment.
For very late arrival, where the distance is greater than 100%, the shut in condition that caused the well to be shut in is also adjusted. The condition is adjusted so that the well is shut in for more time. The adjustment is fixed at 2% of the distance. That means that if the distance is 110%, the adjustment is 1.10 * 0.02 = 0.022 = 2.2% of the set point. The greater the distance, the greater the adjustment.
In all cases, the adjustment will be limited to the range specified by the condition's optimization limit. Each flow condition and shut in condition has a corresponding high optimization limit and low optimization limit. These limits are specified as a percentage of the set point. An automatic adjustment will not exceed these values. To disable optimization of a specific condition, set the optimization range to 0. This will not allow the set point to be adjusted.
Optimized set points for all conditions can be viewed via the relevant status parameters.
Condition Adjustments
The table below shows how each Flow Condition set point is adjusted for each plunger arrival type.
1. Before Plunger Lift application version 1.4.3 the increase/decrease were reversed for the Critical Flow shut in condition, which was incorrect. The values shown apply to Plunger Lift application version 1.4.3 and later.
