Cable Installation Procedures for Deep Wells Brief Summary
Special attention must be given to cable installation to prevent damaging the cable when it is used on deep wells where high tensions are encountered. This section of the manual discusses drum crush and how it can be avoided with proper cable installation and operating techniques.
It is of prime importance to put a logging cable onto a winch using the proper spooling profile. The proper spooling profile is the profile that will match the tensions expected during logging as closely as possible. Drum crush will result if the cable is not installed properly.
In instances where cables have been installed at significantly lower tensions than those experienced in the borehole, the cable in the lower layers under low tension have been "crushed". By "crushed" we mean that at certain spots in the cable, the two dimensions of the cable measured at 90 degrees with respect to each other are significantly different, i.e., the cable is no longer round, but egg-shaped. The most likely spot to experience cable crushing is where the cable "crosses over" the winding in the layer below. In the winding below, the crossover direction is opposite the direction in the layer being installed. At the "break or crossover", the cable contacts the cable underneath at only one point. That single point of contact is directly underneath the cable. The pressure at this single point is twice as high as the pressure on the cable around the rest of the circumference of the winding, since at all other locations, the cable is supported in 2 adjacent windings as it sits in the valley between those two windings. A logging engineer should be alert to the following two situations in order to prevent the logging cable from being crushed.