Estimated gas loss thru wet gas pipeline

[720101]

Hi and Dear All.

Anybody knows how do you calculata estimated nat gas loss ( wet gas) departing offshore at e.g 90 barg, 70C , [75% mole C1, 15% mole C2, 10% mole C3] and reach terminal at 70 barg , 50C with about the same compositions through a PL with 26" X 75 km long?

Gas rate assumed at offshore is at 300 mmscfd.
Note: To do manual calc w/out Hysis, pipesim or Olga

rgds

 

[LittleInch]

Sorry, but can you explain what you mean by "gas loss"? You have the pressure drop and flow rate, what more do you need. Is there any liquid or water when it starts?

BTW I can't see a 70C subsea gas line arriving at 50C after 75 km - more like seabed temperature if you ask me.

I can't see how composition would change if all you have is C1,2,3. If you have condensate then some of that will flash off as the pressure falls to change the composition, but not C 1-3.



My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way

 

[720101]

Dear Littleinch, thank you for yr reply.

Further to this, I am assuming C1,C2 and C3 since I don't have yet the actual compositions. I will hv to get them and manually calc the gas loss.

What I mean gas loss is est gas condensed along the pipeline. Yes, the arrival temp will be seabed temp.
I would like to know how do you calc est gas condensed along PL with say 300 mmscfd wet gas flowrate at the depart P,T without any simulations done.

RGds

 

[LittleInch]

I'm not sure that you can, but at those sorts of pressures and temperatures I wouldn't expect to see any real drop out of C1,C2 or C3 that didn't start life in the pipeline as liquid.

Not sure why you need this, but without some sort of composition analysis or simulation I think it would ne very difficult to do it manually and the answer would be very approximate.

what is your concern / issue? The mass of gas will be the same in steady state over a period of time.

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way

 

[720101]

Thank you LittleInch.

I am a process eng in Oil & gas co. Basically, operations team in one of our platforms exporting wet gas asking me to est gas loss...they do not have gas meter at depart and landing point..only parameters as I mentioned.
rgds

 

[LittleInch]

No where near enough information or data here to get anywhere close. ~The term "wet gas" is very vague, - usually means gas with water saturated vapour, but could mean anything. Without a more detailed composition you can't find out what the static volumes could be of any compound in terms of whether it is above the boiling point at that pressure and temperature (start and finish) to be able to estimate if anything which is a gas at the start point is a liquid, or some fraction of it has turned into a liquid, by the time it gets to the end point.

It's all much easier in a simulation program....

If they don't have a gas meter at the start and finish, how are they going to measure it?

Remind them that the same mass flow rate in = mass flow rate out.

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way