line sizing

[ChePengPM]

Hi Guys,
In EPC word, what is the best option/way and your experiences for line sizing when you have a line list with +100 lines.
Thanks for sharing

 

[zdas04]

Man, that is not an easy question. Most people start with a velocity range (I use 11 ft/sec to 120 ft/sec unless the company has other limits, lower limit is really the minimum velocity that will allow gas to shift water, upper is quite arbitrary). At that point I will either build a hydraulic model of the system or generate a set of velocity vs pipe-size graphs for given downstream pressure (assuming that the off-system pressure is defined). Then I'll work backwards from the off-system point to the wells and pick a pipe size that works. Often several pipe sizes will work for a given segment and for those segments I'll define a "standard" size for that classification of use (i.e., well flow lines, laterals, or trunks). Then I'll do a reality check. If most of the trunks are 12-inch, but one is 10-inch I'll generally accept a lower-than-minimum velocity in the one trunk to minimize pigging complexity and purchasing complexity.

In other words, it should be a very complex exercise managing Engineering considerations with Operational and Procurement considerations. Oh yeah, and everything you do in a new field development has a high probability of being very wrong. Every well has a personality and most of them are unpleasant. No well is average, but the only assumption available to you is that all of them will be average. In my experience you do your best knowing that in year 2 and 3 you'll have to have projects to correct problems in the piping caused by above-average wells.

David Simpson, PE
MuleShoe Engineering

"Belief" is the acceptance of an hypotheses in the absence of data.
"Prejudice" is having an opinion not supported by the preponderance of the data.
"Knowledge" is only found through the accumulation and analysis of data.
The plural of anecdote is not "data"

 

[Berenger]

Does your company have a standard "line sizing" spreadsheet? If yes, then all you'll have to do is probably just plug in the numbers - T, P, flow, sg and, maybe, pipe schedule or thickness.

If your company doesn't have one, you can develop one yourself using the volumetric flow and pressure drop equations.You will need to validate this spreadsheet before it can be used. This is done by calculating the line size, velocity and pressure drop using the spreadsheet you developed and comparing the solution to both hand calculations and a reputable software like ProMax.

Using ProMax is quite easy. Go to the property window, analysis and then click on line sizing.
Put in the maximum pressure drop (you can find rule of thumb values if you search this forum) for gas pipelines: 0.15 psi/100 ft for secondary lines and 0.25 for the primary gas pipelines. You'll also put in the max velocity (for gas, 80 ft/s). Put in pipe schedule or thickness and click execute. For liquid rule of thumb values, see attached excel sheet.