Piston Effect on Tapered String and Expansion Device

In many situations, a completion string may consist of several size of strings and components so total axial force must be carefully considered by applying a free body diagram concept. When the tubing string is free to move, forces will affect the tubing above where the force is applied.

Tapered String

Tapered string is a string which consists of more than one size of tubing. Hence, forces acting at tapers must be accounted for. Force depends on configurations of pipe and pressure and it will either decrease or increase surface load.

Figure 1 illustrates diagram of a tapered completion string. Wherever in the string there is a difference in outside diameter or inside diameter, there will be downwards or upwards force acting against the tapered edge. It is imperative to analyze each ledge and combine all the results in order to see the total effect. From Figure 1, F1 and F2 cause compression, but F3 creates tension force.

Figure 1 - Tapered String Configuration

Figure 1 – Tapered String Configuration

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Well Control Procedure for Non-Shearable String

There are many cases when non-shearable string is across the BOP therefore blind shear rams will not be able to shear the string to secure the well if needed. The special procedure must be in place to deal with this situation. This is an example of well control procedure for non-shearable string. If you want to use it for your rig, it must be modified to match with your rig operation.

Well Control Procedure for Non-Shearable String FB Continue reading