Gas export conditions through subsea pipeline?
Gas export conditions through subsea pipeline?
(OP)
HI There,
just need few advices on the above subject:
in fact we are exporting gas to shore from an offshore platform.
The pipe is 8" diameter and 100 km long subsea. the sea bed temperature is about 4oC.
the gas caracteristics at the metering kid prior to be sent to the subsea line are as follow:
•Line pressure 70 bar
•Line temperature 3oC
•Dry gas dew point <7lbs/mmscfd
•Gas measured through orifice plate 2.75" orifice diameter.
•Average gas rate 20mmscfd
•Gas temperature @ beach 25oC
My question:
How can the gas temperature rise during the transporation in the subsea line?
With a lower gas temperature as above is there any possibility of the gas quality being affected prior to reach the beach?
Your assistnce will be much appreciated.
Cheers
the
just need few advices on the above subject:
in fact we are exporting gas to shore from an offshore platform.
The pipe is 8" diameter and 100 km long subsea. the sea bed temperature is about 4oC.
the gas caracteristics at the metering kid prior to be sent to the subsea line are as follow:
•Line pressure 70 bar
•Line temperature 3oC
•Dry gas dew point <7lbs/mmscfd
•Gas measured through orifice plate 2.75" orifice diameter.
•Average gas rate 20mmscfd
•Gas temperature @ beach 25oC
My question:
How can the gas temperature rise during the transporation in the subsea line?
With a lower gas temperature as above is there any possibility of the gas quality being affected prior to reach the beach?
Your assistnce will be much appreciated.
Cheers
the





RE: Gas export conditions through subsea pipeline?
Here you do have some considerable length involved and the flow is not exceptionally high, so I would have thought that the temperature might fall some. But looking at your data, it does appear that the temperature lost 5oC on the run to the beach, so where did the line gain temperature?
I would at least have a look at the overall heat transfer coefficients used in the analysis to see if they look reasonable. If the line is buried, the heat transfer properties of the soil might not have been correct. Depending on currents on an exposed line, the heat transfer of the film coefficient can be another source of error.
"We have a leadership style that is too directive and doesn't listen sufficiently well. The top of the organisation doesn't listen sufficiently to what the bottom is saying." Tony Hayward CEO BP
http://www.youtube.com/watch?v=hpiIWMWWVco
"Being GREEN isn't easy." Kermit
http://virtualpipeline.spaces.liv
RE: Gas export conditions through subsea pipeline?
IMO it looks like an error in an instrument.
Best regards
Morten
RE: Gas export conditions through subsea pipeline?
"We have a leadership style that is too directive and doesn't listen sufficiently well. The top of the organisation doesn't listen sufficiently to what the bottom is saying." Tony Hayward CEO BP
http://www.youtube.com/watch?v=hpiIWMWWVco
"Being GREEN isn't easy." Kermit
http://virtualpipeline.spaces.liv
RE: Gas export conditions through subsea pipeline?
Presuure loss in the pipeline comes from friction and all the "work" it "transferred" to the media. So its an isenthalpic adiabatic expansion- or JT expansion.
Then some heat may transfer through the wall of the pipeline - thats why you will asymptotic approach the ambient temperature - usually slightly colder.
Best regards
Morten
RE: Gas export conditions through subsea pipeline?
"We have a leadership style that is too directive and doesn't listen sufficiently well. The top of the organisation doesn't listen sufficiently to what the bottom is saying." Tony Hayward CEO BP
http://www.youtube.com/watch?v=hpiIWMWWVco
"Being GREEN isn't easy." Kermit
http://virtualpipeline.spaces.liv
RE: Gas export conditions through subsea pipeline?
I've never seen a fluid friction result in a net temperature gain compared to heat gain/loss through the pipe walls. My experience is that a line that long would tend to be essentially at ambient (ground or sea) temperature on exit.
Unless you are flowing past a fire breathing Kraken (or a BIG thermal vent), I'd say there is no internal flow phenomenon that would explain that sort of temperature rise in that sort of ambient conditions.
David
RE: Gas export conditions through subsea pipeline?
"We have a leadership style that is too directive and doesn't listen sufficiently well. The top of the organisation doesn't listen sufficiently to what the bottom is saying." Tony Hayward CEO BP
http://www.youtube.com/watch?v=hpiIWMWWVco
"Being GREEN isn't easy." Kermit
http://virtualpipeline.spaces.liv