Choke valve datasheet

[40410]

I have to specify the process data for the choke valve.
The well is having the following conditions

2000 BPD oil with 0% water cut
4000 BPD oil with 50% water cut

In this case, oil is flowing from 3 wells which is combined in a local manifold near the 3 wells and one line is run to the separator/ inlet manifold
I know the line size and line length and the separator/inlet manifold operating pressure.

i modelled the same in the HYSIM with flow from and the choke valve and the piping modelled as pipe segment and terminated with a separator. i fed the operating pressure of the separator and as i have fed the flow , pressure at the upstream of choke valve and fedd all the data required for pipe segment to calculate the pressure drop.

But the model could not get the value of pressure at the choke valve discharge by adding the pressure drop in the piping and the operating pressure of separator to arrive at the choke valve downstream pressure.

when i run the size utility, i am able to get pressure drop for the pipe segments modelled

how to decide the optimum value of pressure drop across the choke valve for with/ without water cut and different separator operating conditions
could anyone resolve this

 

[MortenA]

This is how HYSYS works. It dosnt calculate pressuredrop in a control valve/choke - you specify it. Why? Because its not a trancient simulatior - its a SS. Its the only natural assuption that your valve is big enough and that there then is a "suitable position" that will give the pressure drop you are interested in.

Specify the pressure in the outlet stream and everything is fine.

If your trailing calculation then gives a wrong pressure in the vessel and you wish to find your pressure at the choke outlet - set up a "adjust" function that will change pressure in your downstream the choke stream until your pressure in your separater matches your required value.

Best Regards

Morten

 

[krossview]

I agree with MortenA and would also recommend the databook feature in Hysys. It's a very powerfull feature and allows you run various cases by adjusting the inlet conditions of the separator. You can do a case study where Hysys adjust the independant variable(s) or record individual simulation results. It's a very quick way to find you optimum separator conditions, because it enables me to monitor various parameters that interest me.

Be aware that Hysys can crash when storing large amount of data and case studies in the databook. So, I copy and paste the results into Excel and delete the case study.

I know that there is the optimizer feature, but find the databook much easier to use.

Good luck

Krossview/OK

 

[209larry]

Normally the pressure drop is calculated from flowing tubing head pressure FTHP less separator or manifold pressure. Pressure drop between choke valve and separator or manifold can be considered negligible.

If you have the value of CITHP(closein tubing head pressure), your company must have calculation procedure to to get FTHP.

You should provide min/max flowrate/FTHP cases for optimum valve sizing and check also if there is gas lift option in the future. The valve must cover all operating conditions you require.

Use HYSIS in predicting composition at the separator not calculate pressure drop on short piping.

Rgds,

209Larry

 

[abb2100]

Pleas note that the process across a chock valve in a sence is tendeng toward isentropic ( constant entropy) rather than isenthalpic( constant enthalpy). This is due to great velocity change across the valve. Hysis does not model chock valves directely. I model chock valves indirectly by the followeing steps.
1. defininig a compressible gas pipe with inlet and
outlet streams,
2. set the length to very small number,
3. set the desired operational flow rate of the inlet
stream,
4. initially set the pipe ID and other characteristics
5. decrease the pipe ID until the velocity of the outlet
stream approaches the sound velocity ( mach close to 1).
Hysis does not converge if the velocity equals or
exceeds sound velocity.
In this way one can approximately size the chock valve for the the flowing well head pressure. The downstream pipng can be modeled to set the required constant pressureat of the separator.

 

[TD2K]

Isentropic? I doubt very much you'd have isentropic expansion across a choke valve especially with the high velocity. High velocity implies turbulence and that is definitely not something associated with isentropic processes.