Tie-In Branch Design on an existing Flowline

[gv83]

Good Morning to all, this is my first post at all!

I'm working in a gas field in Sahara Desert and we have to assess if the following operation is feasible or not.

We want to reroute an existing 8" CS flowline and connect it to another 8" flowline through a barred TEE.

The flowline (let's call it "A" )that will be the new main line will be sectioned by the TEE approximately 3.3 km from the wellhead ( and the total length is 4.8 km).

The second flowline ( the branch, "B") length will be approx 150m.

The working pressure will be decreased from the present 70 barg to 23 barg since a new compressor station has been installed.

We would want to install across the TEE also two manual flanged ball valves from the TEE to well "A" and two manual flanged ball valves from the TEE. ( We only have flanged valves abailable)

My questions are:
1. Is it allowed by the code to put all this equipment buried? ( In a concrete canteen)
2. What do you suggest to avoid loads on the connection? Expansion Loops?
3. In order to avoid any leakage or damage due to working conditions, it is preferrable to put only the TEE? This will reduce the possibility to dismiss wells in the future.
4. Is it better to put everything above ground?

Thanks in advance for your help.

Best regards
GV

 

[LittleInch]

My questions are:
1. Is it allowed by the code to put all this equipment buried? ( In a concrete canteen)
Can't see why not

2. What do you suggest to avoid loads on the connection? Expansion Loops?
If the main line A is on a long straight then you won't get axial movement, but the connection from well B should either be anchored or come in as a z bend (buried) to take out the thermal thrust force on the tee.

3. In order to avoid any leakage or damage due to working conditions, it is preferable to put only the TEE? This will reduce the possibility to dismiss wells in the future.
Don't understand the question

4. Is it better to put everything above ground?
not much in it. AG means more bends and supports, but might be easier to see what is going on.
buried flanges aren't normally a great idea, but in the desert you're not going to get much in the way of corrosion, just tape up the flanges and grease the bolts so you can break the flanges later if you want.

A drawing helps a lot, especially to understand stresses and movements.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[BigInch]

Above ground is never the best of ideas, even if out in the middle of a desert.
Desert winds use the sand to blast off the pipeline coating.
Day and night temperature changes can cause constant movement.
In Saudi we used to say that it never rains in the desert... until it RAINS!
There are 8 washed out major highway bridges in Asir Province from flash flooding in 1986 still there to prove it.

Technology is stealing American jobs. Stop visas for robots.

 

[gv83]

Ok,

I attached a sketch of the map with routing.

To reply to the other concerns:

3. In order to avoid any leakage or damage due to working conditions, it is preferable to put only the TEE? This will reduce the possibility to dismiss wells in the future.
Don't understand the question --> The Well A and B are producing well now, but it happens here that sometimes a no more producing well is dismantled and the piping/telecom/instrument material is moved to another well.
Said that, if I have to dismantle well A , I need to isolate the relevant branch of flowline from the well up to the TEE: I should put two valves upstream the TEE.

4. Is it better to put everything above ground?
not much in it. AG means more bends and supports, but might be easier to see what is going on.
buried flanges aren't normally a great idea, but in the desert you're not going to get much in the way of corrosion, just tape up the flanges and grease the bolts so you can break the flanges later if you want.

Since the two well are producing, we have to reduce the down time of the two wells: I can put everything on a metal frame and maximize the construction work in SIMOPS.

 

[BigInch]

I'd put the bar tee with a valve and a flange set upstream. When/if you remove the well, close the valve and replace the upstream flange with a blind flange and be done with this. No you don't need two valves.

Technology is stealing American jobs. Stop visas for robots.

 

[LittleInch]

Ok, "dismiss" is not a usual term - "de-commission" or "destruct / abandon" is more usual. Yes, but you could just abandon the leg from the tee to well A and isolate unless they remove the buried piping as well?? That's usually too expensive.

It's not great practice to do that and leave a long dead leg so yes, valves are better, but not essential, especially if the wells only operate for a limited time.

That should be Ok - It will make it easier to anchor all the incoming lines on the skid and reduce stresses on the tee.

Still better to come in as you've shown then add a 90 degree elbow and end up from well B coming in parallel with the line from well A.

nothing too unusual with what you're doing.


Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[Bernoulli31]

Just saying, I'm jealous of your job.

I design aqueducts in a parallel universe.