Questions about MMSCFD
Questions about MMSCFD
(OP)
Hello all, I'm pretty new in oil and gas I have few questions any advice is much appreciated:
Question 1
Information of natural gas (assumes methane) provided by operator i.e. 5 mmscfd, 50 bar, 80 C am I right to say that it is referring to standard condition at 1 atm, 60 F not the specified conditions?
Question 2
So if I want to convert to mmcfd I need to do (PiVi)/Ti = (PfVf)/Tf
With P = Pressure, V = Volume, T = Temperature, i being initial and f being final,
which give me 0.52 mmcfd.
Is this the actual flow rate at the specified temperature and pressure, need confirmation please?
Question 3
What about converting to kg/s using gas constant?
Thank you
Question 1
Information of natural gas (assumes methane) provided by operator i.e. 5 mmscfd, 50 bar, 80 C am I right to say that it is referring to standard condition at 1 atm, 60 F not the specified conditions?
Question 2
So if I want to convert to mmcfd I need to do (PiVi)/Ti = (PfVf)/Tf
With P = Pressure, V = Volume, T = Temperature, i being initial and f being final,
which give me 0.52 mmcfd.
Is this the actual flow rate at the specified temperature and pressure, need confirmation please?
Question 3
What about converting to kg/s using gas constant?
Thank you





RE: Questions about MMSCFD
2) This is for an ideal gas and gets you close, but not close enough for real gases and proper calculations. You need to look this up and do it properly. I think you've got a decimal point wrong and it's circa .0.01 mmcfd.
Remember temp is in degrees K and pressure in bara. Try not to mix units. It just confuses everyone.
3) Depends on the density of your gas.
My motto: Learn something new every day
Also: There's usually a good reason why everyone does it that way
RE: Questions about MMSCFD
On question 2, what the hell are you converting from? I always calculate density at standard conditions and at flowing conditions, then if I have a standard flow rate, I can get an actual flow rate by qstd*ρstd/ρactual
Density = [P*SG]/[Rair*T*Z] Don't leave out the compressibility, even at very low pressures, you can't afford the 2-30% error that ignoring it will incur. Once you know density (either actual or standard) then mass flow rate is simply q*ρ. Work with density, not pressures/temperatures/compressibilities/gas constents--I can't tell you the number of times I've fixed stupid errors that come from not being able to do simple algebra.
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"
RE: Questions about MMSCFD
Katmar Software - AioFlo Pipe Hydraulics
http://katmarsoftware.com
"An undefined problem has an infinite number of solutions"
RE: Questions about MMSCFD
RE: Questions about MMSCFD
RE: Questions about MMSCFD
It is way worse than that. Queensland has a different number than NSW which is different from SA. This means that a field like the Cooper Basin that has production in all three must store data in three different standards (four if the sales contract specifies its own). Most people solve this by storing "standard" volumes at known pressure and temperature (usually one of the standard variations) and then convert on output. I am always amazed when companies get the conversion wrong, but it happens all the time.
As to "number of moles", standard "volumes" are a good surrogate for both moles and mass. I did an exercise this morning where I got a change in mass flow of 21% and a change in "volume" flow in SCF of 26%, red flags went off everywhere and I quickly found my bonehead error since a 21% change in mass must be a 21% change in moles and a 21% change in SCF. That is anything but true in actual volume flow rates (which changed by nearly 50%)
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"
RE: Questions about MMSCFD
I agree (and i think we have been there before
RE: Questions about MMSCFD
so
P*V=n*R(universal)*T*Z ==> P*V = m*R(gas)*T*Z ==> P*V*SG = m * R(air) * T * Z
Yep, looks like the same for moles or mass.
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"
RE: Questions about MMSCFD
RE: Questions about MMSCFD
RE: Questions about MMSCFD
It has been a really long time since I had any degree of mastery of Hysys (think mainframes, think CICS) so I can't really speak to anything that the current owners (Aspen Technologies) do. My dim memory is that back in the dark ages the primary input for flow was mass/unit time. Moles were a secondary option and volume flow rates (even at standard conditions) were not allowed.
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"
RE: Questions about MMSCFD
RE: Questions about MMSCFD
David Simpson, PE
MuleShoe Engineering
Law is the common force organized to act as an obstacle of injustice Frédéric Bastiat
RE: Questions about MMSCFD
RE: Questions about MMSCFD
RE: Questions about MMSCFD
David Simpson, PE
MuleShoe Engineering
Law is the common force organized to act as an obstacle of injustice Frédéric Bastiat
RE: Questions about MMSCFD
While we are knocking David
Katmar Software - AioFlo Pipe Hydraulics
http://katmarsoftware.com
"An undefined problem has an infinite number of solutions"
RE: Questions about MMSCFD
Katmar, you have to read closer. It wasn't 53.335 it was 53.335/SG
R(gas)=R(universal)/MW(gas)
SG = MW(gas)/MW(air) --> MW(air) = MW(gas)/SG
R(air)= R(universal)/MW(air) --> R(universal) = R(air)*MW(air)
Substituting:
R(gas)=R(air)*MW(air)/MW(gas) = R(air)/SG
R(air) = 53.355 ft*lbf/(lbm*R)
David Simpson, PE
MuleShoe Engineering
Law is the common force organized to act as an obstacle of injustice Frédéric Bastiat
RE: Questions about MMSCFD
Katmar Software - AioFlo Pipe Hydraulics
http://katmarsoftware.com
"An undefined problem has an infinite number of solutions"