Patent Application
20140147301
This invention relates generally to the field of submersible pumping systems, and more particularly, but not by way of limitation, to a seal section separation bag for use within a submersible 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 the inhospitable downhole environment, which includes wide ranges of temperature, pressure and corrosive well fluids.
Components commonly referred to as “seal sections” protect the electric motors and are typically positioned between the motor and the pump. In this position, the seal section provides several functions, including transmitting torque between the motor and pump, restricting the flow of wellbore fluids into the motor, protecting the motor from axial thrust imparted by the pump, and accommodating the expansion and contraction of motor lubricant as the motor moves through thermal cycles during operation. Many seal sections employ seal bags to accommodate the volumetric changes and movement of fluid in the seal section. Seal bags can also be configured to provide a positive barrier between clean lubricant and wellbore fluid.
As the use of downhole pumping systems extends to new applications, traditional bladder systems may fail under inhospitable downhole environments. For example, the use of downhole pumping systems in combination with steam assisted gravity drainage (SAGD) technology exposes bladder components to temperatures in excess of 500° F. To increase the resistance of the bladder to degradation under these increasingly hostile environments, manufacturers have employed durable polymers, including various forms of polytetrafluoroethylene (PTFE), as the preferred material of construction. More recently, manufacturers have employed the use of perfluoroalkoxy (PFA) fluoropolymers. The use of PFA as the material of construction in seal bags is disclosed in U.S. Pat. No. 8,246,326 issued Aug. 21, 2012 and assigned to GE Oil & Gas ESP, Inc.
Although PTFE and PFA provide suitable materials of construction of many pumping applications, at extreme temperatures and elevated pressure differentials, even these materials may exhibit some permeability to liquids and gases. Of particular concern is the potential for liquid water permeation through the seal bags at extreme temperatures. There is, therefore, a need for an improved seal bag, seal sections and submersible pumping systems that overcome the deficiencies of the prior art. It is to this and other needs that the present invention is directed.
In a preferred embodiment, the present invention provides a seal section for use in a downhole submersible pumping system. The seal section includes a housing and a seal bag located within the housing. The seal bag comprises a substrate having a plurality of substrate surfaces and a metal coating layer on at least one of the plurality of substrate surfaces. The substrate can optionally be configured as a cylindrical form that includes an interior surface and an exterior surface. In particularly preferred embodiments, the substrate is seamless and fabricated from an extruded fluoropolymer. The metal coating layer preferably comprises a metal selected from the group consisting of titanium, stainless steel, nickel, chrome, silver and gold.
In accordance with a preferred embodiment of the present invention,
The pumping system 100 preferably includes some combination of a pump assembly 108, a motor assembly 110 and a seal section 112. The motor assembly 110 is preferably an electrical motor that receives power from a surface-mounted motor control unit (not shown). When energized, the motor assembly 110 drives a shaft that causes the pump assembly 108 to operate. The seal section 112 shields the motor assembly 110 from mechanical thrust produced by the pump assembly 108 and provides for the expansion of motor lubricants during operation. The seal section 112 also isolates the motor assembly 110 from the wellbore fluids passing through the pump assembly 108. Although only one of each component is shown, it will be understood that more can be connected when appropriate. It may be desirable to use tandem-motor combinations, multiple seal sections, multiple pump assemblies or other downhole components not shown in
Referring now to
For purposes of illustration, the bag seal assembly is disclosed as contained within the seal section 112. It will be understood, however, that the bag seal assembly could be installed elsewhere in the pumping system 100. For example, it may be desirable to integrate the bag seal assembly within the motor assembly 110 or pump assembly 108.
Referring now also to
In preferred embodiments, the substrate 130 is fabricated from an elastomer or other polymer, such as, for example PTFE, PFA, or polyvinyl chloride (PVC). Unlike prior art bladders, the seal bag 118 includes a metal coating layer 140 of chemically stable and inert metal or metal alloy. Presently preferred metals include titanium, stainless steel, nickel, chrome, silver and gold, and alloys for each of these metals. It will be appreciated that the metal coating layer 140 may be produced with combinations of multiple metals and metal alloys. In alternate preferred embodiments, the seal bag 118 is provided with a multilayered coating that includes two or more metal coating layers 140. For these multilayered embodiments, it will be appreciated that each metal coating layer 140 may be prepared using different metals and metal alloys.
The metal coating layer 140 is preferably applied to at least one of the exterior surface 138 (
Alternatively, the metal coating layer 140 is provided as a foil laminate over the substrate 130. In this alternate embodiment, the foil metal coating layer 140 may be adhered to the substrate with adhesives, mechanical fasteners or chemical bonding.
In a particularly preferred embodiment, the substrate 130 is manufactured from PFA and includes a titanium or titanium alloy metal coating layer 140 on the exterior surface 138 that is approximately 10,000 angstroms thick. PFA is commercially available from a number of sources, including E.I. du Pont de Nemours and Company and Daikin Industries. Like PTFE, PFA exhibits favorable resistance to corrosive chemicals and elevated temperatures. Unlike PTFE, however, PFA is melt-processable using conventional injection molding and screw extrusion mechanisms. The ability to extrude or mold PFA permits the construction of a seamless, unitary substrate 130. Furthermore, seal bags 118 manufactured using PFA experience less stretching during the expansion and contraction cycle than comparable PTFE-based bags. These characteristics favor PFA as a substrate for metallization because it is easier to achieve a more uniform coating along the seamless bag, and metal coating layer 140 is less likely to separate, crack, flake or peel from the substrate due to stretching and contraction.
Turning now to
The o-ring seal 128 includes an exterior surface 142 and a metal coating layer 144 on the exterior surface 142. The metal coating layer 144 is preferably prepared under the same techniques, using the same materials described above with reference to the metal coating layer 140 of the seal bag 118. The metal coating layer 144 increases the durability and lowers the permeability of the o-ring seal 128. The use of metalized o-ring seals 128 significantly decreases permeation of liquids and gasses across the o-ring seal 128 at elevated temperatures.
Although the o-ring seals 128 have been described with reference to the seal section 112 and shaft 116, it will be understood that the o-ring seals 128 will also find utility in other applications. For example, the o-ring seals 128 can be used in other downhole and surface pumping components that include, for example, pothead connectors, motor assemblies, pump assemblies, sensor arrays, and logging tools.
It will be further understood that the novel use of metalized polymers will find application in other downhole components, including, for example, mechanical seal bellows and pothead connectors. By way of illustration, an alternative embodiment includes the use of a metalized bellows 150 within a mechanical seal 152. Turning now to
The bellows 148 is preferably constructed from a polymer substrate 160 and a metalized coating 162. In preferred embodiments, the polymer substrate 160 is fabricated from a polymer, such as, for example PTFE, PFA, or polyvinyl chloride (PVC). The metalized coating 162 is preferably made by deposition, sputtering, spraying or through use of foil lamination. Preferred metals include titanium, stainless steel, nickel, chrome, silver and gold, and alloys for each of these metals. It will be appreciated that the metalized coating 162 may be produced with combinations of multiple metals and metal alloys. In alternate preferred embodiments, the bellows 148 is provided with a multilayered coating that includes two or more metalized coating 162. For these multilayered embodiments, it will be appreciated that each metalized coating 162 may be prepared using different metals and metal alloys. With the metalized coating 162, the bellows 148 is capable of withstanding higher temperatures and is less likely to rupture during explosive decompression.
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.
