5. Down-Hole Example

This example makes predictions for a situation where a tool is lowered into a well to a depth indicated by the friction rollers. The same dimensions as used on the previous 3 examples are used here D=2.375”, t=0.188”, spool radius = 60”, Gooseneck radius = 84”. In this example, 1000 ft of tubing are lowered into a well with a tool weighing 1,630 lbs. Water is assumed to fill the tubing and annulus. The surface pressure inside the tubing is taken as 5000 psi, and 1000 psi in the annulus. Assuming the tool to be 3.5” in diameter and 50 feet long, the force distribution from the tool to the surface (with x = distance from tool a position along the tubing) is approximated by: F(x) = 6988 lbs + 2.451 lb/ft (x).

The tube was divided into 8 increments and the force computed at the end of each increment. The CTDef model was run using the input panel option to make 10 trips for the conditions outlined above. The permanent and maximum strains from the runs are listed in the table below, and the average elongation of each segment is estimated. The total permanent and maximum elongation from the runs for this example are estimated to be 18.2 ft and 30.5 ft, respectively.