Wellhead Compression
FIELD TROUBLESHOOTING CHECKLIST FOR WELLHEAD COMPRESSORS
1. Check interstage line temperatures to determine which valves have been removed from a cylinder.
2. Remove disabled valves, cages, and valves in ends taken out of service and replace with gaskets. This reduces parasitic pressure loss.
3. By-pass crank-end when not in use through fuel gas lines. Saves horsepower.
4. Is engine exhaust temperature at least 600°F? [...]
Wellhead Compression – Dual Completions
Attempting to utilize a single compressor to service both the casing and tubing flows on a dual completion well can present some real problems. On one installation, both the casing and tubing were piped into the suction of the reciprocating machine. However, the operators observed that when the tubing flowed unrestricted into the compressor suction, [...]
14Oct2009 | admin | Comments Off | ContinuedWellhead Compression – Minimum Suction Pressure
field compressor to trip-off prematurely. In this case, the field operators were reporting that they could not operate a compressor suction below 70 PSIG. Their experience had taught them the following:
1. They would set the compressor to operate in the tandum mode.
2. Over a period of a few days the wellhead pressure would diminish from [...]
Wellhead Compression – Transient Effects
To further complicate the adjustment of a field compressor, one needs to be aware of certain transient effects that the well imposed on the compressor.
• Many wells, immediately after unloading liquids exhibit an increase in wellhead pressure sufficient to overload and stall the engine.
• Opening the head-end cylinder clearance valve to reduce the first-stage discharge [...]
Wellhead Compression – Varying Speed
If a compressor has an excessively high second-stage (crankend) discharge temperature and a low first-stage (head-end) discharge temperature, one should proceed as follows:
• Reduce the adjustable clearance on the head-end.
• Slow the machine down.
• Balance the above two steps to restore the original wellhead pressure.
This technique switches load from the crank-end to the headend without [...]
Wellhead Compression – Rod Loading Limit
As the wellhead pressure falls, the differential pressure that the field compressor must deliver increases. This is because the collection header into which the compressor discharges remains relatively constant. As this differential pressure rises, the compressor may become limited by “rod loading”. A machine may be only utilizing a fraction of the available engine horsepower [...]
13Oct2009 | admin | Comments Off | ContinuedWellhead Compression – Horse Power Bottlenecks
There are three fundamental limits to which all field compressors are subject:
• Compressor rod loading
• Speed
• Engine horsepower
In addition to calculating the actual engine horsepower by the above equation and comparing it to the name plate rating, the engine exhaust gas temperature should be checked. The engine manufacturer specifies a maximum exhaust temperature for the [...]