TABLE OF CONTENTS As seen in Chapters 3 and Chapters 4, the size of the flow conduit through which the gas is produced (this could be the tubing or the casing-tubing annulus or simultaneous flow up the casing-tubing annulus and the tubing) determines the performance of velocity or siphon strings or just determines how well and for how long the production tubing will produce the well.
The basic concept of tubing design is to have a large enough tubing diameter so that excessive friction will not occur and a small enough tubing diameter so that the velocity is high and liquid loading will not occur. The objective is to design a tubing installation that meets these requirements over the entire length of the tubing string or flow conduit. Also, it is desired to meet these requirements for as long as possible into the future before another well configuration may be required.
The concepts needed to properly size and evaluate a tubing change-out have been described in Chapter 4 using Nodal Analysis concepts and in Chapter 3 using critical velocity concepts. Both of these concepts should be considered when sizing tubing to reduce liquid loading. A well decline curve is also desirable to help decide if liquid loading is a problem and to properly evaluate the installation of smaller tubing.
The reason to run smaller tubing is to increase the velocity for a given rate and to sweep the liquids out of the well and...
