gas metering instrument 1

[141175]

I have a case folowing:
A field with reserves are 65 Bcf, Developping facilities are include: 01 monotower, 01 gas producer with peak flowrate is 30 MMscfd, produced gas wil be transported to another platform for processing by a 10"x10.5 km sub-sea pipeline. We have to set up a gas metering instrument in that monotower.
Could you please help me to recommend a suitable gas metering instrument, that bring me high economical efficiency ?
Bests regard.
141175

 

[zdas04]

Is this a custody-transfer station or a mass-balance station? If it is custody-transfer, then the contract will specify the measurement technology required. Deviate from the contract at your peril.

For any other category of gas measurement I would look for something with acceptable accuracy, that doesn't have much tendency to foul, and that has a reasonable calibraton frequency. The station that stands out with that criteria is an ultra-sonic. These stations rely on the doppler shift of fluids moving away from them determine velocity. Today most of them have temperature and pressure compensation routines to convert the actual velocity to a standard volume flow rate (but make darn sure the one you select does - I learned the hard way that doing your own coversion takes a bunch of code that is hard to fit into most RTU's).

David Simpson, PE
MuleShoe Engineering

http://www.muleshoe-eng.com

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

The Plural of "anecdote" is not "data"

 

[141175]

Thank for useful idea. But I think that, if we set up an ultrasonic gas measurement we will set up more additional equipment like: generator, indoor& master computor,gas chromatograph panel... alls not suitable for unmanned platform like monotower. I think in this case we need onother kind of simpler & more suitable measurement instrument

 

[DrillerNic]

What about an orifice meter then? Read out to a pressure transducer and then to your DCS/ SCADA system or to an old fashioned chart recorder. My old platform (and it was almost older that I was!) used to use Daniels boxes and orifice meters for all their non- custody metering. Erosion can be a problem if the orifice isn't sized properly or you have solids production.

 

[141175]

Thanks DrillerNic, but Daniels box & orifice meters can be used as custerdy meter. Beacause i need an custerdy gas meter in this case

 

[141175]

Thanks DrillerNic, but Daniels boxes and orifice meters can be used as a custerdy gas meter ?

 

[DrillerNic]

I don't think orifice meters can really be used as custody meters, but I don't know enough about metering to be sure.

If you've got a design a custody meter then I'd go with zdas' suggestion and see what the contract says and then speak to a vendor.

 

[zdas04]

Nearly 100% of the gas sales (custody transfer) in the U.S. go through a square-edged orifice meter at least once (and 90% of that goes through one 4 or more times).

Daniels fittings are the big dog in that business worldwide - everyone else is trying to build a niche from Daniels long product-lead time.

This type of measurement has the widest body of operational and calibration data of any sort of measurement.

In short, yes Daniels orifice fittings can be used for custody transfer. Check your contract, and it probly specifies ASME 14.3 measurement (i.e., orifice meter).

David Simpson, PE
MuleShoe Engineering

http://www.muleshoe-eng.com

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

The Plural of "anecdote" is not "data"

 

[mb44]

If this is custody transfer then you will almost certainly need other equipment besides the meter

Normally with gas you pay for the energy flow not the volume flow (even domestic although they assume a standard energy per volume figure)as such you will need to know the volume flow which you get from the meter (turbine, ultasonic, orifice plate), pressure and temperature of the line, gas composition (from gas chromatograph)and a flow computer to put all these signals in this will then calculate the energy rate for you (there are different calculations AGA8 and NX19). If you gas is always one composition and doesnt vary much then you dont need the chromatograph as you can assume a fixed composition

Dont forget all the different meter types require upstream and downstream straight lengths to give accurate meter readings, one problem with orifice offshore could be the space as the straight length can be up to 44*pipe diameter

Ultrasonic is usually 10*Pipe Dia - I think

Your meter vendor would be able to tell you this information depending on the custody specification ISO etc

I dont know this stuff in too much detail, metering is a funny art but there are other vendors as well as Daniels, PECO, FMC plus loads of others but beware some just copy others, they may look cheap but there is no back up support if things go wrong

As well you will alsmost certainly need duty/standby meters, because if one fails you would loose production, also you need to calibrate the meters or have a 'pay and check' arrangemnet of the piping that allows meters to be operated in series if required.

Also are you sure you have custody metering before the gas processing? seems unusual as you could send a load of hot air down the pipe and get paid for it!!!! Perhaps you pay for the gas after the KO drum and first filter unit, this way you only pay for the good stuff?

Few thats enough typing and I havent really grazed the surface of this issue

Regards

MB44

 

[MortenA]

As David Simpson said: Since its costudy transfer there will (most likely) be requirements for this metering application. They can be from companies involved in the transaction and/or govermental.

Check this out first and try to find a commonly accepted system and a technology suited for unmanned installations.

I fail to see how you will get this to work if power is not avaiable? How will you transfer data? But im not a metering specialists.

I also wonder about the fact that it is untreated well "fluid". Usually this will be wet gas and thus require more specialised equipment.

Best regards

Morten

 

[Bubbarock]

I am not sure of your working pressure but at 1440 psi the meter run size is 4".
As far as being used for custody transfer. They have been and are used for this for years. The new AGA / API spec for meter runs using a flow conditioner bring better acuracy and still can be used in non normal conditions.
The cost for a 4" 600 sch 80 std. meter run would be approx $4400.00 Canadian so should be well within any budget.

 

[jsummerfield]

What do you mean by high economic efficiency?

Flow meter technologies often differ between the initial installation cost and the long-term cost due to the permanent pressure loss.

I agree that the orifice is very commonly used for custody transfer. In fact, production contracts often relied upon circular windup chart recorders for custody transfer long after the use of electronic flow computers.

John