PIPELINE OFFSHORE

I Presentation

The following results come from computation with a two components flow (Gasoil-methan/ethan) in a pipe as the picture below :

Exploitation Conditions :

            Reservoir     : pressure = 235 bar        T = 60 degrees C
            Pipes             : internal diameter = 5.5 inches (0.1397 m)
            Gas Production : 5 000 barils a day  (794 850 liters a day)
            Petroleum Production : 15 000 barils a day (2 384 550 liters a day)
            Ouput pressure : 10 bar

In TACITE Code, it is possible to initialize output pressure, i.e. 10 bar, but not the input pressure, i.e. 235 bar.
So our work was to determinate convenient initializing conditions and adapted equipments to obtain a realist simulation.
That is to say, we had to find pump characteristics (velocity and number of stages) .



 
 
 
 
 
 

II Comparison between with and without pump

At first, we made a simulation without pump. We obtain the following results .
 We can see that reservoir pressure is higher than real pressure i.e. 300 bar instead of 235 bar .
That is the reason why a pump is necessary.Also, we decided to introduce a pump at 800 meters upper the reservoir .
 







After many simulations, we found the rights pump characteristics : Nominal rotation velocity is 130 loops per second.
                                                                                                                          : Maximum pressure drop is 250 bar.
                                                                                                                          : Number of stages is 16.
Every stage has the same input internal and external diameters and the same output external diameter.(see Part IV about input files).
 
 






 The Flow Pattern value is defined as below : 1 = single phase liquid flow                5 = stratified smooth flow
                                                                                   2 = dispersed flow                                6 = stratified wavy flow
                                                                                   3 = slug flow                                          7 = annular flow
                                                                                   4 = annular dispersed flow                 8 = single phase gas flow
The slug fraction is the gas pocket fraction.
 

III Comparison between two meshes with a pump

The pump is always the same, for the two meshes and has the same characteristics as the part before.

Mesh 1 : 0 < Pipe lenght < 800 m , pipe  is divided into 8 cells.
                800 < Pipe lenght < 50800 m , pipe is divided into 50 cells.
               50800 < Pipe lenght < 52300 m , pipe is divided into 15 cells.

Mesh 2 :  0 < Pipe lenght < 800 m , pipe  is divided into 8 cells.
                800 < Pipe lenght < 50800 m , pipe is divided into 300 cells.
               50800 < Pipe lenght < 52300 m , pipe is divided into 15 cells.

Temperature  variation is no significant between the two meshes along all the pipe..
Near the pump, there are two different profiles, particulary about pressure.
The most raffined mesh makes faster evolution pressure as picture below.
 
 

To study differences between results with mesh 1 and results with mesh 2, we decided to draw variables, at two locations , function of time iteration. First point (x = 750 m) is just before the pump and second point (x = 1300 m) is just after the pump.