This kind of special wellheads are those who by the use of an electric motor pump installed in the downhole reservoir allows the oil to come up to the surface by the tubing string connected to; and be able to be pumped to the tanks; we are talking of reservoirs lack in pressures or total absence of it, so the oil needs to be extracted by electromechanical devices, and also we need big flow quickly.This kink of wells uses electricity to move the pump downhole, and there are several arranges to connect by cable to the device; the figures ahead are one of the many configurations named ELECTRO-FEEDTHRU WELLHEADS,that by means of an electric penetrator mandrel ( depicted in red is one similar to an ESP model), they makes the connection with the electricity to move the pump . The penetrator mandrel device is a sealed type,explosion proof, and has a reinforced armor cable (very heavy to deal with), that makes the interface between the tubing hanger body, and the tubing bonnet, allowing an effective seal leakproof.
In others configurations of Electro-feedthru wellheads, the use of an electric penetrators is replaced by the an armored cable,that came from downhole to the surface in a single cable configuration; and a pack-off for the tubing bonnet and tubing hanger is the one that assures no leaks, we are talking of designs that uses REDA Cable configuration, and the uses of this ones depends of how much safety feature is added to the wellhead, as well as, pressures.
Once the pumping motor is feed it start to move and sucks the oil from the reservoir, (power for that pumps are impressive 1,000 to 3,000 HP), package compact. The oil in this way is being pushed to the tubing string in this case: 3-1/2" OD. tubing ,and it reaches the surface ,so the Christmas tree allows a control of the flow being carried out.Notice that this kind of arrangement for Electro-feedthru systems has an offset flange in the top of the tubing bonnet, as well as a hold-down flange in it, that allows an easy assembly with the tubing head's top flange. The tubing head section is typically the only one with the Christmas tree, that this kind of equipment are quoted and sale, due to the previous sections already planted in the field, because of a lost in pressure's well.
This is an electric penetrator mandrel used typically in Electro Feedthru Wellheads Systems, and there are many manufacturers available cost and quality, and models for any kind of budget
The one in the left is similar to an ESP model, observe the different section of the piece and the seals, as well as the armored cable.
Some of the details for the wellhead described above can be seen ahead.
Next is a close up of the same wellhead detailing seals and tubing bonnet.
Notice that the tubing hanger has an internal 3" nominal H-BPV preparation for plugging the well when needed.