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Seasoning a New Well Logging Cable

It is very important that a new cable be operated properly during the first runs in the well. During seasoning, a cable is much more susceptible to damage due to improper operation than later in it's life. Proper seasoning is the first step to insure the longest possible cable life.

When the cable is first put into use at the wellsite, it experiences changes in length, diameter, and torque condition. The goal is for the cable to become properly "normalized" for the typical well conditions in which it operates. The changes in length, diameter, and torque are interrelated, and are primarily a function of the cable's operating tension.

The cable is in a low-tension condition (several hundred pounds only) during the manufacturing process. The cable experiences high tension when it is first installed on the logging unit drum. The installation tension profile is chosen to be appropriate for the maximum tensions at which the cable will operate. As a cable is subjected to high tensions it becomes smaller in diameter, due to compression of the core from the radial forces exerted by the armor package. Any void space present in the core will be eliminated as the cable "pulls down" or becomes smaller in diameter. The cable also gets longer during the seasoning process, gaining its permanent stretch. The amount of permanent stretch and the degree of length stability is primarily related to cable tension and borehole temperature. The permanent stretch of a cable will be larger, as operating tension and downhole temperature increases. The permanent stretch is primarily related to the rotation or "unwinding" of the cable, the compression of the core, and not to stretch of the individual armor wires.

In addition to the changes in length and OD, and most important to proper seasoning, is the changes the cable experiences in it's torque condition. Because cables are installed with the ends fixed (not free to rotate), they will undergo much of the permanent rotation in the first few runs in the well when the downhole end is free. As an example, consider a new 15/32" OD seven-conductor cable, 25,000 ft long. If the full length Is placed in a perfectly vertical, 25,000 ft deep air filled well for the first trip, where it is allowed to hang under it's own weight and be completely free to rotate, the free end will rotate 600 to 700 times. After this permanent rotation is established, it will rotate only when the tension changes. A cable that is not allowed to rotate freely can develop serious problems, including loose outer/tight inner armor, loss of tensile strength, development of high wires and birdcages, and damage to the plastic insulation. Also, a cable with loose outer/tight inner armor does not stretch predictably.

An important aspect of the rotation factor is the dynamic condition of the two armor layers. During seasoning the layers are not "seated" against each other- both layers of armor and each individual wire can and will move independently. As the cable becomes normalized with respect to tension and torque, the armor wires stretch only a small amount, the helical layers unwind and lengthen, and the OD decreases. As the cable is operated and accumulates runs in the well, solid particles from the wellbore fluids and corrosion accumulate between the wires and armor layers, and the individual wires become seated against each other.

In old cables, the armor layers can become securely fixed to the point of acting like a single solid "tube" of steel, instead of individual wires.

A new cable's condition and limitations are important to recognize when working with wellhead pressure and pressure control equipment. Pressure control equipment seals only around the outside diameter of a cable. It is possible to lose the seal when the pressurized wellbore fluids pass up between the armor layers. Camesa applies Superseal between the armor layers of all monocables during manufacturing. This compound reduces or eliminates the movement of fluids between the armor layers in new cables. As a new cable accumulates runs in the well, the voids between the armor layers become filled with the solid particles present in the borehole and grease from the injection head. Therefore, an older cable does not usually experience the pressure bypass problem.

The improper use of pressure control equipment can easily damage a new cable during the seasoning process. The grease injection head, hydraulic packoff, pressure type wireline fluid applicator, and any similar device can cause forced rotation and "milking" of the outer armor strands.

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