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,… Read More »
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… Read More »
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… Read More »
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… Read More »
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… Read More »
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… Read More »
The easiest, but least cost effective method, to operate a field compressor is the crank-end mode. When only the Crank-end (i.e. second stage) is in operation, capacity, compression ratio, as well as engine horsepower load and compressor rod loading are minimized. Left to their own devices, field personnel oft-times run compressors on the crank-end only.… Read More »
This incident illustrates the importance of adjusting field compressor operation to maintain a minimum velocity in the production tubing. The velocity must be sufficient to entrain water, which migrates into the well, up into the high pressure separator. Based on a limited amount of data taken in gas field operation and a more substantial data… Read More »
Figure 4-1 illustrates a typical two-stage compressor. Machines of this type range from 30 to 300 horsepower. They are driven by a gas engine; fueled by natural gas. Engine speed is 250 to 450 rpm, with the compressor inter-cooler and after-cooler air fans driven by the engine. Such machines are rugged, reliable and flexible. To… Read More »