Patent Application
20150125325
This invention relates generally to the field of submersible pumping systems, and more particularly, but not by way of limitation, to a connector for use in connecting a power cable to a component in a downhole pumping system.
Submersible pumping systems are often deployed into wells to recover petroleum fluids from subterranean reservoirs. Typically, the submersible pumping system includes a number of components, including one or more fluid filled electric motors coupled to one or more high performance pumps. Each of the components and sub-components in a submersible pumping system must be engineered to withstand an inhospitable downhole environment, which may include wide ranges of temperature, pressure and corrosive well fluids.
Typically a power cable and motor lead cable supply power to downhole components through a pothead connection. High temperature electrical pothead designs often use a compression seal, like an o-ring, to seal the cable insulation to the inner block of the pothead's housing. As the cable insulation expands under high downhole temperatures, such as temperatures approaching or exceeding 250° C., the insulation presses against the compression seal, and the compression seal expands until it is compressed into the mounting grooves of the pothead's housing. This expansion may also cause the compression seal to press into and deform the cable insulation. When the downhole temperature cycles back down, the insulation contracts back down toward the copper core of the cable. If the insulation was deformed by the expansion of the compression seal, the compression seal may not properly seal onto the insulation. Without a proper seal, well fluid may leak through the pothead and into the motor or other downhole component. Well fluid leaking into the motor can cause decreased motor performance and eventual motor failure.
Accordingly, there is the need for an improved sealing device that will allow expansion to occur at high temperatures without deformation of the cable insulation and incorporate the sealing mechanism into a single, simple, compact design. It is to these and other deficiencies in the prior art that the present invention is directed.
In preferred embodiments, the present invention includes a high temperature connector for use in connecting a power cable to an electric motor. The connector includes an outer housing, an inner housing inside the outer housing and at least one cable conductor disposed through the inner housing. To maintain a seal around the cable conductor during thermal expansion and contraction, the connector includes at least one spring-energized seal disposed around the cable conductor. The spring-energized seal permits the expansion and contraction of the cable conductor without deforming the cable conductor or the sealing mechanism against the inner housing.
In accordance with a preferred embodiment of the present invention,
The pumping system 100 further includes a motor lead extension (MLE) 114 and pothead connector 116. The MLE 114 is preferably configured to have a lower profile than the power cable 112 because it resides within the smaller annular space between the pumping system 100 and the wellbore 104. The MLE 114 may also include additional armor and shielding to guard against damage from contact with the pumping system 100. The power cable 112 extends downhole and is connected to the MLE 114 on its lower end. The MLE 114, in turn, is connected to the pothead connector 116, which secures the MLE 114 to the motor 106. Alternatively, the power cable 112 may extend from the surface directly to the connector 116.
Although the power cable 112 and MLE 114 are depicted in
Turning now to
The connector 116 further includes one or more cable conductors 124 that pass through the compression nut 122 and inner housing 120 of the connector 116. In a particularly preferred embodiment, the connector 116 includes three cable conductors 124 that each correspond to a different phase of electrical power provided to the three-phase electric motor 106.
Each of the cable conductors 124 includes a core 126, an insulating layer 128 and a sheath 130. The core 126 typically consists of copper or another conductive material to provide an electrical connection to the motor 106 or other component of the pumping system 100. The insulating layer 128 is made out of an insulating material, such as Ethylene Propylene Diene monomer (EPDM), polyether ether ketone (PEEK) or epitaxial co-crystallized perfluoropolymer. The sheath 130 acts as a protective barrier to protect the cable conductors 124 from hazardous, high temperature well environments. Each of the cable conductors 124 is configured for connection with the MLE 114 and internal wiring within the motor 106.
The connector 116 further includes one or more spring-energized seals 132 and may also include one or more o-rings 134. The number of spring—energized seals and o-rings will vary depending on thermal expansion difference between inner housing 120 and outer housing 118. As depicted in
During the operation of the motor 106, the connector 116 is exposed to cycles of increasing and decreasing temperatures. During these thermal cycles, the insulating layer 128 of the cable conductors 124 undergoes alternating periods of expansion and contraction around the core 126 of the cable conductors 124. As the insulating layer 128 expands, it presses outward on the spring-energized seal 132. The spring-energized seal 132 accommodates the expansion and contraction of the insulating layer 128 of the conductors 124 to maintain a fluid seal through the connector 116.
More particularly, during expansion of the insulating layer 128, the spring 138 in the spring-energized seal 132 is radially compressed, thereby allowing the insulating layer 128 of the cable conductors 124 to expand toward the inner housing 120 of the connector 116 without deformation of the insulating layer 128. As the temperature recedes and the insulating layer 128 contracts, the spring 138 expands and presses the lip seal flaps 136 back onto the insulating layer 128. Thus, the spring-energized seal 132 maintains a seal around the cable conductors 124 which prevents well fluid from passing through the inner housing 120 of the connector 116 and into the motor 106.
It is to be understood that even though numerous characteristics and advantages of various embodiments of the present invention have been set forth in the foregoing description, together with details of the structure and functions of various embodiments of the invention, this disclosure is illustrative only, and changes may be made in detail, especially in matters of structure and arrangement of parts within the principles of the present invention to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed. It will be appreciated by those skilled in the art that the teachings of the present invention can be applied to other systems without departing from the scope and spirit of the present invention.
