Well streams must be sampled and analyzed with great care if the resulting data are to serve as a reliable design basis. Even then, the well-stream composition used in design must be viewed realistically. The likelihood that the actual feed to the processing equipment will be identical to the design basis is remote. Production is usually from a combination of wells that may have differing compositions. The producing pattern (number of wells and flow rate from each) may be different from that originally envisioned. Also, well-stream compositions change as reservoir pressure declines. Equipment must be sufficiently flexible and/or adequately sized to operate well in the face of changing feed composition and flow rate. In addition to well-stream composition, important design data are wellhead pressure, temperature, and flow rate. These variables change with time in a manner often difficult to predict, but nevertheless important. Decline of reservoir pressure with production is a much-...