This paper presents results of a comprehensive study on cable design concepts for Electric Submersible Pumping (ESP) rigless deployment. One of the key challenges faced by operators with ESPs is how to efficiently deploy and retrieve these systems. Rig-based, conventional jointed pipe installations are costly for high pressure naturally flowing wells, especially offshore. Over the years, various Cable Deployed ESP (CDESP) concepts and technologies have been proposed and tested. Most of the concepts worked to some degree but very little additional development has been done to optimize the technology. The focus of this study was to conduct state-of-the-art technology review, explore different concepts based on technological and material advancement, and identify the most viable cable design concept for further development.
All aspects of ESP deployment and retrieval have been reviewed to ensure a complete definition of the requirements and technology gaps. The cable has to perform a dual function: to conduct power efficiently and to support the downhole assembly. There are three critical aspects to the development of this cable concept: environmental protection, ability to carry the weight of downhole assembly and cable terminations. One of the key environmental requirements is to withstand 15% H2S concentration. A reliable method for isolating the conductors from H2S exposure is a key requirement. The second key requirement is that the cable needs to have ability to carry its own weight plus the weight of the ESP with additional over pull load capacity. A third key element in the design involves methods to terminate the cable with the ability to transmits power and provide mechanical support.
Several possible cable design concepts were investigated in this study: wire wrapped, copper conductor cable, non-copper conductor cable, and Slick Line Power Cable (SLPC). Taking into consideration of various requirements, it was concluded that SLPC had the most merit. It addressed the issue of H2S permeability as well as handling issues. The size and weight of the system are within reasonable limits making transportation less of an issue. There are fewer different materials used so differential thermal and mechanical force considerations are simplified and electrical and mechanical connections are more straightforward. All of these considerations lead to a development that is less risky and faster than the other options investigated.