A Review and Analysis of Equipment for Running Electrical Cables Under Pressure

Developments in permanent-type well completion techniques have accentuated the need for improved equipment to handle cables under pressure. Existing conventional packoff devices were tested and their dynamic performance established at 200 to 600 psi with electrical conductor cables. A new packoff technique is reported that permits operating stranded cables at moderate running speeds up to pressure as high as 3,000 psi. In the higher pressure ranges a new commercial device is reported for running cables against well pressure as high as 6,000 psi. These new developments open wide the doors to improved well completion practices, resulting in improved well productivity and more precise well control. Introduction Field experience with some phases of permanent-type well completions uncover a need for more adequate and simplified means of running conductor cables into wells under pressure. This paper concerns armored electrical cables usually used in service company work, although the findings are equally applicable to other stranded cables. The construction of a reverse armor electric conductor cable is such that 20 per cent of the cross section area is pore space. The difficulty in sealing this amount of space has dictated, in the past, the use of small diameter cables for even medium pressure work. Early experiments with packing glands used with conductor cables revealed that a complete high-pressure shutoff could only be obtained by filling the pore space within the cable with heavy grease or packing gland pressures, which prohibited or retarded cable movement. Recently a new concept has developed of handling cables under pressure. Tests have shown that with a stranded cable located in a closely fitting metal sleeve, the flow through and around the cable is not great and can be controlled. This is known as the controlled blow-by principle and its use has opened up a new approach to the stuffing box problem.