Hi, I am currently working on my master thesis and in this context I want to model the depressurization of a CO2 transport pipeline in HYSYS.
So my question is if any of you have experience with this kind of modelling and could offer me some advice on the way.

Here follows a brief description of the case:

The pipeline is a 153 km, 8 inch offshore CO2 reinjection pipeline and the model is should be able to simulate the depressurization of it.
Initially the pipeline will be closed in both ends and it is assumed that the conditions of the pipe has settled, meaning that the initial temperature in the whole pipe is equal to the ambient seawater at 5 C.
The pressure is set to be an average of 100 bars, or 113.95 bars at the wellhead and 86.05 at the valve onshore. The valve at the wellhead will remain closed for the whole simulation and the valve onshore opens to start the depressurization.
Also, prior to depressurization, all the fluid will be in liquid phase and 100% CO2 (Impurities will be added at a later stage) and there will be no flow in the pipe. The flow is induced by the pressure reduction from when the valve opens and the
Liquid CO2 starts to boil off. For the simulation I want to be able to study how different valve openings and heat transfer coefficients affect the depressurization time. The backpressure of the depressurization valve is 1 atm, and the simulation ends when
The pipe pressure reaches equilibrium with this.

As I mentioned I have done the same model in OLGA and I want to find out how well suited HYSYS is to do these same kinds of flow calculations. In other words the transient/dynamic behavior within the pipeline is of great importance.
To be able to compare the results, the model is quite basic and I have tried to implement the same geometry that I have used in OLGA which is a steady inclination all the way and a total elevation from inlet to outlet of 300m.
As you can see from the overview of the OLGA model its modeled with a source with only is on during the initialization and then is turned off. The leak opens after the initial conditions have been reached. You can also see the overview of the simplified geometry. And from the results graph you can see how the pressure develops for different positions in the pipes (don’t mind the numerical instabilities in the end). So this is basically what I am trying to achieve in HYSYS, and I trying to find out what the possibilities to do so is.

All the best,
Eirik Thu