US20140360729A1

US20140360729A1 - Subsea or downhole electrical penetrator

Info

Publication number: US20140360729A1
Application number: US14/298,585
Authority: US
Inventors: Harald Benestad
Original assignee: Ingenior Harald Benestad As
Current assignee: Ingenior Harald Benestad As
Priority date: 2013-06-07
Filing date: 2014-06-06
Publication date: 2014-12-11
Also published as: WO2014195465A2; WO2014195465A3

Abstract

A subsea electrical device has a penetrator extending through a housing for the connection of a motor lead cable supplying electric power or electric signals. The penetrator has a glass or glass-ceramic body sealed to the housing. A connector, such as a pin connector, extends through the glass or glass-ceramic body. The motor lead cable connects to one end of the connector while the other end of the connector allows for the transfer of the electric power or electric signals to the components within the housing. The glass or glass-ceramic body withstands the high pressure and harsh environment of the subsea atmosphere, allowing for the long term us of the electrical device without need for replacement due to failure of the penetrator.

Description

This application claims benefit of U.S. provisional application 61/832,411, filed Jun. 7, 2013, the content of which are incorporated in their entirety.

BACKGROUND OF THE INVENTION

Various subsea and downhole systems today are reliant on the provision of electricity provided from a distant source in order to fulfill their functions. Many of these functions were either not relevant or were conducted above the water surface before subsea operations and the more recent developments in more complicated and advanced downhole operations were realized. While the various conventional topside systems also require provision of power in the form of electricity, the environments obviously differ greatly.
Moreover, drilling operations continually occur at greater and greater depths, increasing the pressure on the equipment. Reasons for failure in the various systems requiring electrical power include electrical insulation breakdown, particularly where the electrical lines are connected to and penetrate the subsea or downhole equipment housing. The conventional mating connector often also forms the penetration point from the outside to the inside of the various subsea and downhole components or systems. In various pumping/compression systems, contamination of the motor insulation (motor oil) with well fluid can lead to early insulation failure. Electrical breakdown in the connector or penetrator may be due to the combination of fluctuating or high pressures/temperatures, well fluid effects, well fluid intrusion, poor insulation etc. Electrical breakdown in the connector or penetrator due to well fluid intrusion, heat, poor insulation due to the combination of pressure, temperature and well fluid is not uncommon In addition to the effect of fluid intrusion, resulting in electric shorts between the pins of the connector or penetrator, the geometry and materials of the connector or penetrator contribute to electric shorts occurring. The high voltages/currents, the short distance between the pins together and the presence of well fluids greatly increase the risk for shorts. The replacement costs for the various subsea and downhole components or systems are high and the electrical penetration or connection point for the various subsea and downhole components or systems must be able to withstand the operating conditions to avoid being the reason for replacement.
A conventional connector comprises a mating three pin male and female connection, where the pins comprise a suitable metal alloy material and are surrounded and spaced by a suitable polymer material. In addition, seals are used to isolate the interior of the connection against intrusion of well fluids. Conventional penetrators, either they form part of or are separate from the connector, are in the form of inserts that are sealed by various seals, welds, screw connections etc. that all are prone to failure and leakage, particularly in the highly fluctuating, high temperature, high pressure subsea or downhole environment.
In addition to the problem of electrical shorts in the connector or penetrator, that by itself may result in system failure, the connector or penetrator may also serve as an intrusion point of well fluids into the various subsea and downhole components or systems. Even if the connector or penetrator does not suffer electrical short, the intrusion of well fluids through the connection or penetrator passage may cause other problems that ultimately results in the various subsea and downhole components or systems to fail, e.g. loss of lubrication, premature wear of moving parts etc.
It is an object of the invention to provide a penetrator for the various subsea and downhole components or systems able to withstand the operating conditions for an extended period of time.
It is another object of the invention to utilize glass ceramics in creating a seal for the penetrator of various subsea and downhole components or systems.
It is yet another object of the invention to provide a penetrator that prevents electrical problems when power is supplied to downhole components or systems.
It is still another object of the invention to provide a penetrator providing long term electrical connection in a high pressure environment.
These and other objects of the invention will be apparent to one of ordinary skill after reading the disclosure of the invention.

SUMMARY OF THE INVENTION

The penetrator of the present invention uses a glass/glass-ceramic sealed to the metal housing of the various subsea and downhole components or systems. The glass/glass-ceramic is an inorganic material and will not deteriorate over time. It is very resistant to water, salt solutions, acids, metals and organic substances as well as long term exposure to high pressure and a broad range of operating temperatures. The combination of high temperature and pressure will cause the polymers in the current penetrators to become brittle and the insulating properties will decrease, leading to electrical breakdown and loss of a pressure barrier.
One challenge with the conventional penetrators for the various subsea and downhole components or systems, is the available space, or lack thereof, and the insulation distance between pin(s) and housing body. According to the present invention, one solution is to provide a greater distance between pin and component or system housing body, resulting in a larger glass/glass-ceramic.
By sealing the glass/glass-ceramic directly to the housing of the subsea and downhole components or systems, an absolute seal is provided between the subsea and downhole components or systems housing body and the glass/glass-ceramic, as opposed to using various O-rings, welding, screw connections or other conventional sealing arrangements. Also, by sealing the glass/glass-ceramic directly to the various subsea and downhole components or systems, a hermetic seal effective over a large pressure and temperature range is formed. Furthermore, this arrangement and solution makes it possible to increase the distance between the pin(s) and component or system housing body. By splitting the phases in three (or more), i.e. by providing an arrangement with three individual and separated penetrators through holes, the abovementioned advantages and benefits are increased even more.
The invention improves performance of the electrical penetration in several ways. These include sealing the glass/glass-ceramic directly into the component or system housing body, with three (or more) separate holes with one pin in each hole or make one larger hole, either circular or oval, with all three pins in the same glass/glass-ceramic, making the component or system housing wall a pressure bather to ensure clean motor oil (no mixing with well fluid), and allowing the penetrator to withstand up the high pressures encountered in HTHP, in addition to a considerable safety margin.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross sectional view of an embodiment of the present invention;

FIG. 2 is a detailed view of a section from FIG. 1;

FIG. 3 is a front perspective view of an embodiment having three slots formed in a sidewall;

FIG. 4 is a cross sectional view of the embodiment of FIG. 3;

FIG. 5 is a top perspective view of an embodiment having a single slot housing three pins; and

FIG. 6 is a front perspective view of an embodiment having a single slot housing three pins in a kidney shaped seal.

DESCRIPTION OF THE INVENTION

The present example relates to the application of the present invention in an Electrical Submersible Pumping (ESP) system. It is understood that the present invention is equally applicable for other subsea and downhole components or systems that require electrical power provided from some distant source, where electrical power or electrical signal is supplied though electrical power or signal lines from the source to the subsea and downhole components or systems, and where the subsea and downhole components or systems comprise a metal housing or wall though which must be penetrated. These subsea and downhole components or systems can include, but are not limited to pumps, compressors, separators, hydraulic, power and signal systems, rotary systems, communication systems, injection systems, high integrity pressure protection systems, actuator systems, etc.
Electrical submersible pumping (ESP) systems are a form of artificial lift developed to help petroleum companies maximize their production for the least amount of investment. Oil and gas production is the process of bringing the hydrocarbons in a well to the surface. With sufficient pressure in the reservoir, the hydrocarbons surface naturally. Artificial lift is needed in most cases to provide additional energy or pressure to increase the flow of well fluids to the surface, and this additional pressure is provided by Electrical Submersible Pumping (ESP) systems.
The ESP system is comprised of an electrical motor, seal section, rotary gas separator, multistage centrifugal pump, electrical power cable, motor controller and transformers. The ESP systems operate in high temperature, corrosive environments and are subjected to high pressure at the great operating depths. The fluid within the ESPs is high viscosity and can be abrasive.
The ESP motors are typically two pole, three-phase, squirrel cage, induction type. The critical link between the downhole equipment and the power source is the ESP cable, having either a round or flat configuration. The motor lead cable connects the main ESP power cable to the motor. The motor lead cable is spliced to the power cable and banded to the pump and seal assembly all the way down to a pothead which is plugged into the motor.
ESPs may be placed in the production string during completion. In reservoirs with low initial pressures, the ESPs may run from start-up. In reservoirs where the initial pressure is sufficient, but where pressure gradually depletes, the ESPs may lay dormant for many years before they start to run. In many cases more than one ESP is installed in order to have redundancy.
Under some conditions, conventional ESPs may have high failure rates, and may break down after only a couple of years of production. Vibration, a corrosive environment, general wear on the radial bearings and leaks may all play a significant role in reducing pump life. When the motor shaft vibrates, it increases wear on seals around the shaft, eventually permitting fluids produced from the well to leak into the protected interior of the pump. Wellbore fluids can seep past the shaft seals and into the motor itself, where they contaminate the motor oil and change its dielectric, hydraulic and lubricating properties, causing failure of the pump motor.
FIG. 1 shows one application of the invention for High Temperature, High Pressure (HTHP) ESPs. FIG. 1 depicts the pump 10 separated from the motor 20 by the motorhead 30. A driveshaft 22 of the motor 20 extends through the pothead separator into the pump. The details of FIG. 1 are more clearly shown in FIG. 2. The pothead separator with the pump 10 above the pothead separator and the motor 20 below the pothead separator is seen. The sidewall of the motorhead 30 has a recess 32. At the bottom of the recess is an electrical connector, such as a pin connector 40 embedded in a glass/glass-ceramic seal 50 to form the penetrator.
The metals of preference for both the housing of the motor and pothead separator is Titanium grade 5, NACE approved Titanium or Inconel 718 NACE. The penetrator is coupled to the cable by a multilam contact or similar contact, and the pin connector is protected with an overlaying bootseal of a suitable polymeric material and/or situated in dielectric oil. Any suitable connector can be used for the penetrator and a mating connector on the power cable completes the electrical connection.
FIG. 3 depicts the motorhead having three separate recesses 32, each configured to receive a motor lead cable carrying power to the motor. Each recess is formed by a radially extending bottom wall 34. The bottom wall extends upwardly and it extends inwarly. This causes the pin connector 40 to be angled outwardly to facilitate connection of the motor lead cable. A sidewall 36 extends from the inner edge of the bottom wall 34 and tapers outwardly as it extends upwardly from the bottom wall to meet the sidewall of the motorhead. The motor lead cable supplies power to the motor and has a copper core surrounded by insulation. The motor lead cable connects to the pin connector 40 extending from the bottom wall 34 of the recess. Glass/glass ceramic seal 50 surrounds the pin connector and is sealed to the motorhead. The seal maybe any suitable types, such as a compression seal or a match seal. While the recess and penetrator are depicted in the housing of the motorhead, these elements can easily be formed directly in the housing of the electrical components, such as the pump, compressor, separator or communication system.
By splitting the pin connector into three separate recesses, the distance between pin connector and housing is increased, and the chance of electrical breakdown decreases. The glass/glass-ceramic is an inorganic material and will not deteriorate over time. It is very resistant to water, salt solutions, acids, metals and organic substances as well as long term exposure to high pressure and a broad range of operating temperatures.
Various pin configurations in the penetrator are depicted in FIGS. 5 and 6. FIG. 5 depicts a configuration with one recess 132 having three pin connectors 140 within one glass seal 150. This arrangement would connect with a motor lead cable having a mating connector. FIG. 6 is similar to FIG. 5 in showing a single recess 232. The three pin connectors 240 are spaced from one another in the circumferential direction, causing the glass seal 250 to have a kidney shape. The invention provides a more durable electrical connection to a motor in an ESP system.
While the invention has been described with reference to preferred embodiments, variations and modifications would be apparent to one of ordinary skill in the art. The invention encompasses such variations and modification.

Claims

What is claimed is:

1. A subsea or downhole penetrator for an electric subsea or downhole component or system, the electric subsea or downhole component or system comprising:

a metal housing,

at least one slot formed in the sidewall of the housing, the at least one slot forming a passage from an exterior to an interior of the housing,

the penetrator comprising:

at least one pin running through the at least one slot through the sidewall of the housing,

a glass or glass ceramic seal surrounding the at least one pin, the glass or glass ceramic seal forming a seal with chemical bonding between the glass or glass ceramic material and the pin material and the glass or glass ceramic material the housing material, respectively.

2. A subsea or downhole penetrator according to claim 1, wherein the seal between the glass or glass ceramic material and the pin material and the glass or glass ceramic material the housing material, respectively, is a compression seal.

3. A subsea or downhole penetrator according to claim 1, wherein the seal between the glass or glass ceramic material and the pin material and the glass or glass ceramic material the housing material, respectively, is a match seal.

4. A subsea or downhole penetrator according to claim 1, wherein three slots are formed in the sidewall of the housing.

5. A subsea or downhole penetrator according to claim 4, wherein each slot is provided with one pin.

6. A subsea or downhole penetrator according to claim 1, wherein one slot is formed in the sidewall of the housing.

7. A subsea or downhole penetrator according to claim 6, wherein the slot is provided with three pins.

8. A subsea or downhole penetrator according to claim 1, wherein the at least one slot is circular.

9. A subsea or downhole penetrator according to claim 1, wherein the at least one slot is oval.

10. A subsea or downhole penetrator according to claim 1, wherein the at least one slot is kidney shaped.

11. A subsea or downhole penetrator according to claim 1, further comprising a formed in a housing of the subsea or downhole component or system, the recess having a bottom wall and a sidewall, and

wherein the at least one slot is formed in the recess bottom wall.