API RP 80 pdf download Defnition of Onshore Gas Gathering Lines
The defnition of gathering line in 4.2 describes specifed gathering line end points that delineate the end of the gathering function. This style of defnition is necessary to accommodate the wide variety of gas gathering pipeline confgurations. This recommended practice also defnes production operation in Section 4.4 to assist with describing where the gathering function begins.
4.2 Defnition of Onshore Gathering Line A “gathering line” is defned as any pipeline or part of a connected series of pipelines used to: — transport gas from the furthermost downstream point in a production operation to the furthermost downstream of the following end points, which physically may have intermediate deliveries that are not necessarily part of the gathering line:
1) the inlet of the frst downstream natural gas processing plant, other than a natural gas processing plant located on a transmission line, unless the operator can demonstrate, using sound engineering principles, that gathering extends to a further downstream plant (see Figure 1);
2) the outlet of the furthermost downstream gathering line gas treatment facility; 3) the furthermost downstream point where gas produced in the same production feld or separate production felds not more than 50 miles from each other, is commingled, unless the authorities having jurisdiction permit a longer separation distance;
4) the outlet of the furthermost downstream compressor station used to increase gathering line pressure for delivery to another pipeline; or 5) the connection of an incidental gathering line to another pipeline downstream of: a) the furthermost downstream end point identifed in (1), (2), (3), or (4) of this Section, or in the absence of such end point, the furthermost downstream production operation; — transport gas from a point other than in a production operation exclusively to points in or adjacent to one or more production operations or gathering facility sites for use as fuel, gas lift, or gas injection operations within those operations; Gathering does not include a natural gas processing plant.
A pipeline constructed after the publication date of this RP may not be considered an incidental gathering line if the pipeline exceeds 20 miles in length. Representative applications of the gathering line defnition are shown and discussed in Section 5.
4.3 Basic Gathering Line Defnition Concepts The gathering of gas from multiple production operations can be a complex process. In many locations, one or more of the processes that may occur in the production operation may also occur downstream in the gathering function. The introduction of gas of varying quality into a gathering system may require treatment/processing before the gas can be delivered into another pipeline or facility downstream of the gathering line. Because a gathering system may extend over a large geographical area, it is not uncommon for taps on gathering systems to serve numerous residential consumers, as well as make intermediate deliveries to local distribution facilities or large volume end users. In determining where a gathering line ends, two important concepts are considered—the concepts of “function” and “furthermost downstream.”
4.3.1 Function Concept The function concept recognizes that a gathering line continues to fulfll the gathering function until it reaches a defned and recognized end point, regardless of intermediate processes and/or deliveries along the line. Because gas fowing into a gathering line from various locations may be of difering quality and fowing pressure, it is sometimes necessary to subject the gas stream to one or more intermediate processes. This is usually done to maintain efcient operation of the gathering line and/or maintain pressure in the line to prevent unacceptable back pressure on production or gathering lines. Regardless of the intermediate processes and/or deliveries that may occur along a gathering line, including the existence of customer taps, the gathering function continues until the line terminates at a defned end point.
4.3.2 Furthermost Downstream Concept The furthermost downstream concept recognizes that the most downstream of all locations defned as potential gathering end points is the end point for the gathering line. These end points, together with related basic gathering line concepts, are discussed below.
22.214.171.124 Natural Gas Processing Plants When there is no gas gathering function beyond a natural gas processing plant (as shown in Figure 1), the end point of gathering is the plant inlet. Natural gas processing is not a transportation function. As shown in Figure 2, the gathering function may extend beyond the frst processing plant if justifed by sound engineering principles.