what is the role mechanical engineer inside casing and tubing oil service company?  

  
 

Hi, are you trying to say casing/tubing manufacturing company or casing/tubing running company?
I believe one of the role is to interpret buck-on graphs..

casing and tubing running company

Well, I'm not sure if they are called mechanical engineers, but I expect the casing & tubing running crews to do the following when they arrive on my rig:
1. Check their gear (Has it all arrived?  Is it everythiong they need? Is it all working?  Is it all certified?) and tell me ASAP if there is anything wrong
2. Drift any special assemblies (the casing or tubing will have been tallied & drifted by the drill crew)
3. Check the tally, and let me know if they are unhappy about anything
4. Witness the landing joint/ landing string space out
5. Check with the toolpusher how they will rig up and what utilities they need (and let me know ASAP if there are any problems.... I don't what them whinging to me that "the rig has crows foot fittings and our power pack has BSP fittings and we forgot to check this while we've been watching TV for the last 36 hours")
6. Hold the toolbox talk before they start
7. Rig up and run the casing/ tubing as per the tally, making up all joints to the triangle/ recommended torque turns, noting any reject joints
8. Give me a report and a final as run tally
9. backload all their gear, checking they haven't left anything behind


A mechanical engineer within a tubular running company might do this or might be involved with servicing and maintaining the tongs, power packs etc, or perhaps even involved in designing new tongs and so on.