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Outlaw Automation Inc Has an interesting set of tools designed to run in the Fisher ROC products to enhance production using plunger and/or timers. The program offers a number of different control modes designed to achieve maintaining, or increasing in production. Depending on the mode selected, control functions utilize timers, gas flow rate, well pressure, plunger arrival data or a combination thereof.
The Time On/Off and Plunger Control - Fixed Timers modes are the only selections that will result in definite well on and off times. All other modes will result in a variable on time, a variable off time, or both variables on and off times. Times will vary based on the characteristics of the well and the entered setpoints.
For a FloBoss 103 with the 4-point I/O board the only I/O configuration detail of note is that the DIN Type should be set to Standard. The Accumulated Value parameter is monitored to determine if the plunger has arrived. For a FloBoss 103 with a 6-point I/O board more configurations may be required. If a plunger arrival sensor is connected to a DI point then that DI point must have its DIN Type set to Standard and the Plunger Sensor TLP on the CONFIG screen must be defined as that DI point.
Logic to control the ESD valve is built into the optimization program and operates independently of the password-protected well optimization functions.
In a sample application of Gas Flow Rate vs. Time for a typical gas well that has been shut in for a period of time, and then opened to flow - Pressure has built up during the shut-in time and the well is able to generate a high initial flow rate as the gas flows out of the tubing string. There is sufficient flow to maintain a slug of liquid and bring it to the surface, or a plunger if it has been installed. The Gas Flow Rate drops significantly as the slug of liquid arrives at the wellhead and recovers once the liquid has passed or the plunger has arrived. The Gas Flow Rate will then slowly decline as pressure drops or the well begins to load. The well is shut in when the flow drops below the Critical Flow Set point.
When in Critical Flow mode the Critical Flow set point will determine the length of time the well will stay open after the well unloads. If Plunger Arrival is being monitored then the Post Plunger Sales Time Preset (PPST) will determine the length of time the well will stay open after the plunger arrives.
The Time on bypass time should be set at a value slightly greater than that required for unloading of liquids and/or should allow enough time for the plunger to arrive. A short Time on bypass time may result in premature shut-in of the well.
The Emergency Shut Down (ESD) logic, if purchased as an option, is written into the optimization program and will operate without the optimization program authorization code. The optimization control may not be started if an ESD condition exists.If an ESD condition occurs in an off cycle then the program operation will continue as usual. If the ESD condition persists at the end of the off cycle the program will hold at the start of the on cycle. If an ESD condition occurs in an on cycle then the program will hold until the condition is cleared and the ESD bypass timer has expired if ESD logic is built-in.
Optimization Modes:
1 Time on/Time Off - This mode provides automatic On/Off control of well flow using timer setpoints entered by operator. The cycle may be started in either the On or Off time cycle. The Time On counter will start when the program is activated if the Start flag is set to one.
2 Critical Flow vs. Time Off - This mode provides automatic On/Off control based on a critical flow set point and a fixed time off period. The amount of time that the valve will be open will vary depending on the characteristics of the well. Plunger is optional with this mode. The cycle is started in the on or off time according to the Start Position.
3 Critical Flow vs. Casing - Enhanced On/Off control utilizing well pressure. A Plunger is not required. Use of critical flow allows the on time to vary according to the wells ability to produce gas. Use of casing static delta pressure being less than the set point is included because if a well becomes loaded with liquid when it is flowing, the casing pressure may become considerably greater than the static pressure (DP increases because liquid prevents gas flow up the tubing). If the casing and static pressures are equalized during the shut-in period then this may be considered as a safe condition to resume flow.
4 Static Differential Pressure - Enhanced On/Off control utilizing well pressure. A plunger is not required. Use of critical flow allows the on time to vary according to the wells ability to produce gas. Use of casing static delta pressure being greater than the set point is included because as a well builds pressure during the shut-in time the casing pressure may become considerably higher than the static pressure. When the well is opened to flow the high casing pressure may aid in lifting liquids
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