EXAMPLE WELL PROFILE
Scenario
Description: snub in a completion string
Well Location: High Level (Zama Lake) Alberta, Canada
Temperature: -23 C
Shut in casing pressure: 12 MPA (1850 p.s.i.)
Well Depth: 1860m
Gas at surface: 2% H2S
Casing size: 7"
Tubing size: 2 7/8
Service rig: 72' telescopic single tubing
BOPS: 7 1/16" class 3
Completion String:
Bottom hole assembly: from the bottom up
.10m re-entry guide
3.0m perforated pup joint
2.0m SOT 1 packer
0.58m on/off connector c/w plug in place
6 - joints of tubing
18.0m of 4" blast joints
tubing to surface
Conventional thinking...from the Snubbing Operator's standpoint
You are thinking..... this perforated pup directly below the packer is going to make this job ugly. Basically, I need to provide 5.68m of lubricating space to get this assembly in the hole as I've got nothing to seal on below the packer for staging purposes. The rig's class 3 stack should give me almost 1.2m from their blind to the top of their annular. My unit gives me exactly 1.8m of lubricating space to the bottom of my single gate. Hmmmm......1.2m + 1.8m = 3m of lubricating space. That makes me 2.68m short, so I will need to install 3m of spools before I pick up the snubbing unit. The unit is 14' tall plus another 9' for spools and the rigs stack is going to be at least 6' high. That's 29' to the top of my slips and lets allow 9' for the blocks, bales and elevators for a total of 38'. OK.... I can bring out 2' shorty bales, that will give me back about 4'. I will need 1' minimum for the tool joint stick up above my slips, so now I'm back to 35' with a 72' mast, it's going to be skinny at best. Once we get the packer in hole we can always land the tubing hanger and rig out the spools. If we can get a wireline unit to lubricate the assembly in the well, that would save a lot of grief. That seems like the answer. I will have to also change over my slips to run all those blast joints at that pressure. Maybe I can just sneak them in without changing over.....2 7/8 dies bite pretty good on 4" blast joints. In the end, you get the job done without incident and it took you 10 hours from start to finish.
Piston Well Services thinking....
You are operating Piston Well Services new Rig Assist #3 concentric snubbing unit. The same job comes in and you look over the job description and bottom hole assembly. It measures 5.68m which equates to less than 19'. The 8' stroke concentric will give me 16' and the rigs BOPS will give me another 4'. OK, I've got 20 + feet of lubricating space. I will just rig up as per usual, make up the bottom hole assembly and lower it into the stack. I will then stroke up the concentric unit positioning my annular above the on/off tool and close the bag and slips. I will equalize the well, open the blinds and contract the concentric lowering the entire bottom hole assembly into the well bore. I will then lock down the concentric and start snubbing in non-stop. I won't worry about changing over my slip dies when I get to the blast joints because my new slips bite on any size of pipe up to 7 inch O.D. The job took you 5 hours from start to finish. No spools, no staging, wirelining and no changing slips.
Why would you do it any other way?
1.) Wireline Scenario (*2)
Rig Time: 10 hours @ $400/ hour = $4000.00
Conventional Snubbing Unit 10 hour day plus stripping etc. = $6000.00
Wireline Unit (all charges inclusive and back to base) = $10,000.00
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Total Cost for Day = $20,000.00
1.) Conventional Snubbing (Spool up) Scenario (*1)
Rig Time: 12 hours @ $400 /hour plus overtime = $4400.00
Snubbing Unit 12 hour day (including overtime and rentals listed below) = $7675.00
Additional Rental Charges:
Spools: 3 - 1 m spools @ $250 min = $750.00
Ring Gaskets: 3 @ $75 = $225.00
Flange Bolts: 3 sets @ $50 / set = $150.00
Shorty bales: $250.00
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Total Cost for Day = $12,075.00
Piston Concentric Snubbing Unit Scenario (*3)
Rig Time: 5 hours @ 400.00 / hour = $2000.00
Piston Snubbing Unit: $6000.00
_______________________________________________
Total Cost for Day = $8,000.00
* Safety Factors
1.) some calculated risk, high rig ups, extra rigging and work
2.) lower rig up, no calculated risk, but still extra rigging and work
3.) low rig up, no caculated risk, no extra rigging or work