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, the casing flow stopped. To “correct” this situation, a restrictive choke was placed in the tubing side of the wellhead tree. This resulted in a wellhead tubing pressure higher than the compressor discharge pressure! This odd situation resulted in a net reduction of gas flow from the well as a consequence of the compressor installation. The reason for this detrimental effect was that the wellhead compressor was too small.
