Introducing Pseudo Steady State Nitrogen Lifting Rate in Coiled Tubing Unloading Operations Based on Numerical Methods
Volume Title: 1
1Coiled Tubing Service Supervisor,International Petro Offshore Niam Kish
2Department of Petroleum Engineering, Amir Kabir University Of Technology, Tehran, Iran
3Department of Petroleum Engineering, Amirkabir University of Technology, Tehran, Iran.
One of the most widely applications of coiled tubing is unloading the heavy weight fluids by nitrogen gas. Dynamic time dependent simulations give accurate results, but reasons like availability, run time,and etc.,cause them to be ignored for field simulations. Controlling the nitrogen injection rate in dynamic simulations results are difficult regarding, too many disturbances and field limitations. On the other hand steady state software may cause failure of well intervention and not reliable due to in-dependency of time and transient. Disturbances affected by viscosity and density changes is the main problem. By considering changes in fluid characteristic parameters, calculating unloading time, disturbances trend and fluctuations can be figured out from beginning to stability of well head pressure with numerical methods. Simulation has been implemented with the help of Multi phase transient flow simulator too. Both Transient and pseudo steady state methods are compared with operation results. Transient flow simulator results illustrated about 5% deviation from real operation ,How ever error comes to about 10% when using pseudo steady state numerical method .On the other hand simulation with dynamic multi phase flow simulator is time suffering and contain operational constraint and limitations .Therefor using pseudo steady state method may be capable to estimate the amount of nitrogen volume in shorter time and calculations. Comparing Method differences for nitrogen consumption is calculated to be about 5% .Since the transient time dependent flow simulator and pseudo steady state method compared with real operation to estimate transient disturbance caused by fluid properties changes.