Patent Application
20150027728
The field of the invention is installation of electric submersible pumps and more particularly, devices that enable subassembly installation to fit into a lubricator for live well deployment.
Electric submersible pumps (ESP) are used to increase bottom hole pressure to deliver produced fluids to a well surface. These pumps are multistage centrifugal pumps with the number of stages determined by the depth of the ESP and the properties of the pumped fluids and the well configuration. As wells get deeper, with improved drilling technologies, the number of stages needed to achieve desired production has necessarily increased. The additional horsepower to drive the added stages and obtain higher discharge pressures, also by necessity, increased the length of the motor associated with the ESP.
In order to deploy ESPs in live wells utilizing wire line, the pump assembly has to pass through a lubricator. A lubricator is mounted on the well head at the surface. There are installations where the lubricator length is limited by the derrick height. Other installations may limit the lubricator length based on safety concerns or policy. Lubricator assemblies contain valves at opposed ends that can be sequentially operated to introduce the ESP components into the live well, such as with a wireline or slickline, when the bottom valve is opened and the wireline or slickline is delivered through a sealed connection near the top of the lubricator. Another more recent development is to mate a wet connect device on the lower end of the ESP assembly with the other half of the connection that is connected to a cable, run alongside the tubing that will convey the pumped fluids to the surface. This type of power/instrumentation connection has also added to the overall length of the assembly. Since there is a finite limit to the height of the lubricator supported in the derrick, or limited for safety reasons, it has become a problem to get extended length, higher horsepower, ESP assemblies inserted into live wells.
It should be noted that coiled tubing, continuous rod and jointed rod or tubing could also be utilized to deploy these ESP systems with and without lubricator type equipment. While the lubricator type applications allow these installs on live wells, the same equipment can be used on wells that have been pressure equalized/neutralized or killed.
The present invention addresses this problem with a solution that allows the overall ESP assembly to be broken down into subassemblies that will fit in a lubricator for staged deployment and final system assembly, at the downhole fixture located at or near the bottom of the production tubing. This downhole fixture being the socket portion of the wet connection device. Once run into the well, these staged subassemblies function as though the entire assembly was put together at the surface, as could be done before when the assemblies had smaller motors and fewer stages.
Those skilled in the art will better appreciate the various aspects of the invention from a review of the detailed description of the preferred embodiment and the associated drawings while understanding that the full scope of the invention is to be determined by the appended claims.
An ESP assembly is broken down into subassemblies to fit within a lubricator where a safe working length is required for live well deployment. A lifting device has a shaft transmission feature and associated housing rotational lock for use at the top of the first subassembly which is left in position for engagement of the next assembly. The subassemblies can be delivered on wireline or slickline. A wet connect can be at the lower end of the initial subassembly to connect to a cable run alongside the production tubing. The ESP subassemblies all are deployed and interconnected in the live well and function as they would if assembled at the surface. The ability to break down the assembly and run it in segments lets the components fit through a length limited lubricator for live well deployment.
Referring to
Thus, in operation, the housing 30 does not rotate but the shaft coupling assembly 36 turns. Assembly 36 is supported on bearings 38 and 40 and has a male end 42 with spline 44 to engage a pump shaft that is not shown that extends out the lower end of the ESP 46 shown in
Item 24 is the seal section component. This component provides an equalization function between the well bore pressures seen at depth and the internal pressure of the ESP components 46, 58 and 60. In addition to providing pressure equalization, the seal component 24 also handles axial thrust to the ESP system created by the driven pump assembly 46 while the system is energized. The seal component 24 also protects the motor 22, 24 and connection plug 20 from well bore fluid contamination. It is important to note that the assembly of
The motor shaft extends From 22 through 24 to end 52 where an end spline meshes into the female splined connection 54 shown in
Once the assembly of
Those skilled in the art will appreciate the fact that the problem of limited length in a lubricator is addressed by the present invention that breaks down an overlong assembly into stages that are short enough to load into a lubricator with a length limit of about 25 meters allowing the assembly to be put together in the live well while still maintaining the safety systems that are there to prevent loss of well control. The first break location is at the motor drive shaft which is run in with the lift device 26 in a way that the motor shaft is already coupled to the lift device that is left in the hole after the first trip to deliver the assembly of
The problem that limits placement of ESP in a live well at depths where the length of the ESP and motor exceed the lubricator length is solved with the present invention. While the break locations in the ESP assembly can be selected at different component connections doing the breaking up at the connection of the motor shaft to the pump shaft allows more efficient use of the available length in these limited length lubricators. The incorporation of a shaft connector in the lift sub also allows having the break in the assembly at the connection between the motor and pump shafts. The other components above just push together and are finally anchored by anchor 60. As the operating depth and pressure output demanded from ESPs increases the ability to get the entire assembly into a live well will no longer be limited by lubricator length can no longer be a limiting factor. Indeed in the deeper applications where more pump stages and motor horsepower are required would mean such assemblies could not be run into a live well without significant risks of blowout. The method of the present invention allows the safe downhole assembly in a live well of long ESPs that are wet connected in the hole.
The above description is illustrative of the preferred embodiment and many modifications may be made by those skilled in the art without departing from the invention whose scope is to be determined from the literal and equivalent scope of the claims below:
