Patent Application
20100108393
Downhole tools used in the hydrocarbon recovery industry often experience extreme conditions, such as, high temperatures and high pressures, for example. These high temperatures can be elevated further by heat generated in by the tools themselves. Mud motors, for example, can generate additional heat during operation thereof. Materials used to fabricate the various components that make up the downhole tools are therefore carefully chosen for their ability to operate, often for long periods of time, in these extreme conditions.
Many polymeric materials have maximum operating temperature ranges, that when exceeded, result in early failure of components made therefrom. Advancements in the field that allow tools to operate below these temperature ranges are well received in the art.
Disclosed herein is a downhole mud motor. The mud motor includes, a stator, a rotor in operable communication with the stator, a polymer in operable communication with the stator and the rotor, and a plurality of carbon nanotubes embedded in the polymer.
Further disclosed herein is a method of improving durability of a mud motor elastomer. The method includes, dissipating heat through the mud motor elastomer with carbon nanotubes embedded therein, and maintaining temperature of the mud motor elastomer below a threshold temperature.
The following descriptions should not be considered limiting in any way. With reference to the accompanying drawings, like elements are numbered alike:
A detailed description of one or more embodiments of the disclosed apparatus and method are presented herein by way of exemplification and not limitation with reference to the Figures.
Referring to
The operating temperature of the elastomer 22 can affect the durability of the elastomer 22. Typically, the relationship is such that the durability of the elastomer 22 reduces as the temperature increases. Additionally, temperature thresholds exist, for specific materials, that when exceeded will significantly reduce the life of the elastomer 22.
The elevated operating temperatures of the mud motor 10 are due, in part, to the high temperatures of the downhole environment in which the mud motor 10 operates. Additional temperature elevation, beyond that of the environment, is due to such things as, frictional engagement of the elastomer with one or more of the stator 14, the rotor 18 and the mud 26, and to hysteresis energy, in the form of heat, developed in the elastomer 22 during operation of the mud motor 10, for example. This hysteresis energy comes from the difference in energy required to deform the elastomer 22 and the energy recovered from the elastomer 22 as the deformation is released. The hysteresis energy generates heat in the elastomer 22, called heat build-up. It is these additional sources of heat generation within the elastomer 22 that the addition of the nanotubes 42 to the elastomer 22, as disclosed herein, is added to mitigate.
Several parameters effect the additional heat generation, such as, the amount of dimensional deformation that the elastomer 22 undergoes during operation, the frictional engagement between the elastomer 22 and the rotor 18 and an overall length 46 of the mud motor 10, for example. Additional heat generation may be reduced with specific settings of these parameters, and the temperature of the elastomer 22 may be maintainable below specific threshold temperatures. Such settings of the parameters, however, may adversely affect the performance and efficiency of the mud motor 10, for example, by allowing more leakage therethrough, as well as increase operational and material costs associated therewith. Embodiments disclosed herein allow an increase in power density of a mud motor 10 by, for example, having a smaller overall mud motor 10 that produces the same amount of output energy to a bit 50, attached thereto, without resulting in increased temperature of the elastomer 22. Additionally, the mud motor 10, using embodiments disclosed herein, may be able to operate at higher pressures, without leakage between the elastomer 22 and the rotor 18, thereby leading to higher overall motor efficiencies, for example.
The carbon nanotubes 42, disclosed in embodiments herein, are embedded in the elastomer 22, such that, the carbon nanotubes 42 interface with a surface 54 of the elastomer 22. Having the carbon nanotubes 42 interface with the surface 54 allows a decrease frictional engagement to exist between the elastomer 22 and matter that comes into contact with the surface 54, such as, the rotor 18 and the mud 26, for example. Such a decrease in friction can result in a corresponding decrease in heat generation. Additionally, in embodiments of the invention, the presence of the carbon nanotubes 42, embedded within the elastomer 22, decrease the hysteresis energy and heat generation resulting therefrom.
While the invention has been described with reference to an exemplary embodiment or embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the claims. Also, in the drawings and the description, there have been disclosed exemplary embodiments of the invention and, although specific terms may have been employed, they are unless otherwise stated used in a generic and descriptive sense only and not for purposes of limitation, the scope of the invention therefore not being so limited. Moreover, the use of the terms first, second, etc. do not denote any order or importance, but rather the terms first, second, etc. are used to distinguish one element from another. Furthermore, the use of the terms a, an, etc. do not denote a limitation of quantity, but rather denote the presence of at least one of the referenced item.
