A back-pressure valve is a type of check valve, typically installed in the tubing hanger, to isolate the production tubing. The back-pressure valve is designed to hold pressure from below yet enable fluids to be pumped from above, as may be required for well-control purposes. Thus, it reduces downtime and operating cost by allowing for repairs without killing the well.
BPV is commonly used during the nipple down and up of the drilling BOP stack, nipple up or down of Christmass trees, test the Christmas tree (2-way check valve), and during the replacement of the master valve.
Junction box, Check and Drain Valves, Downhole Sensor and Centralizers are some kinds of ESP Accessory Equipment. These type of equipment could play an important role to operate the ESP efficiently and maximize it run lifetime.
The power cable coming from the well is connected to a surface electric cable leading to the switchboard. As seen in the figure below, the two cables are joined in the junction box, also called a “vent box”. The surface cable connects the junction box to the motor control panel and the motor control panel to the secondary side of the transformers.
It is a ventilated, weatherproof box performing the following three important functions:
Provides the electrical connection between the downhole and the surface electric cable.
Vents any gas to the atmosphere which might reach this point due to migration of well gases up the ESP power cable. The venting of gas eliminates the danger of fire or explosion that could happen if gases travel in the cable to the switchboard.
Acts as an easily accessible test point for electric checks of the downhole equipment.
This article “Downhole and Surface Accessory Equipment” is the step 8 of the nine-step procedure to design an ESP with an efficient and cost-effective performance. The required downhole and surface accessory equipment are discussed and recommended practices are highlighted.
Downhole Accessory Equipment:
Motor Lead Extension (MLE):
API RP 11S4 defines the Motor Lead Extension as a “special power cable extending from the pothead on the motor to above the end of the pump where it connects with the power cable. A low-profile cable (flat configuration) is usually needed in this area due to limited clearance between the pump housing and the well casing”. It is recommended to select a length at least 6 ft. (1.8 m) longer than the upper end of the pump. The length of MLE has to be select in a way to avoid a splice over a tubing collar. Doing so could allow the cable to catch on the wellbore casing and damage the equipment.
Banding Cable Protectors:
Cable protectors are used to protect the Motor Lead Cables from damage during installation, operation and pulling. The figures below show an example of cable protectors.