Abstract:
A downhole mud motor includes, a stator, a rotor in operable communication with the stator, and a plurality of nanoparticles embedded in at least a portion of the stator

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a continuation-in-part application of U.S. patent application Ser. No. 12/264,591, filed Nov. 4, 2008, the entire contents of which are incorporated herein by reference. 
     
    
     BACKGROUND 
       [0002]    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 the tools themselves. Mud motors, for example, can generate additional heat during operation. 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. 
         [0003]    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. 
       BRIEF DESCRIPTION 
       [0004]    Disclosed herein is a downhole mud motor that includes, a stator, a rotor in operable communication with the stator, and a plurality of nanoparticles embedded in at least a portion of the stator. 
         [0005]    Further disclosed herein is a method of improving durability of a mud motor stator. The method includes, dissipating heat through the mud motor stator with nanoparticles embedded in at least a portion of the stator, and maintaining temperature of the mud motor stator below a threshold temperature. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0006]    The following descriptions should not be considered limiting in any way. With reference to the accompanying drawings, like elements are numbered alike: 
           [0007]      FIG. 1  depicts a side view of a mud motor disclosed herein; 
           [0008]      FIG. 2  depicts a cross sectional view of the mud motor of  FIG. 1 ; and 
           [0009]      FIG. 3  depicts a cross sectional view of the mud motor of  FIG. 2  taken along arrows  3 - 3 . 
       
    
    
     DETAILED DESCRIPTION 
       [0010]    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. 
         [0011]    Referring to  FIGS. 1-3 , an embodiment of a downhole mud motor  10  disclosed herein is illustrated. The mud motor  10 , among other things, includes, a stator  14 , a rotor  18  and a polymer  22 , also referred to herein as an elastomer, positioned between the stator  14  and the rotor  18 . Mud  26 , pumped through the mud motor  10  flows through cavities  30  defined by clearances between lobes  34  of the stator  14  and the elastomer  22  and lobes  38  of the rotor  18 . The mud  26 , being pumped through the cavities  30 , causes the rotor  18  to rotate relative to the stator  14  and the elastomer  22 . The elastomer  22  is sealingly engaged with both the stator  14  and the rotor  18  to minimize leakage therebetween that could have a detrimental effect on the performance and efficiency of the mud motor  10 . The elastomer  22 , of embodiments disclosed herein, has nanoparticles  42  embedded therein that have thermal conductivity that is greater than a thermal conductivity of the elastomer  22  to increase heat transfer through the elastomer  22  and into the stator  14 , the rotor  18  and the mud  26 . The increased heat transfer, provided by the nanoparticles  42 , permits temperatures of the elastomer  22  to more quickly adjust toward temperatures of matter contacting the elastomer  22  than would occur if the nanoparticles  42  were not present. 
         [0012]    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 . 
         [0013]    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 nanoparticles  42  to the elastomer  22 , as disclosed herein, is added to mitigate. 
         [0014]    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. 
         [0015]    The nanoparticles  42 , disclosed in at least one embodiment herein, are embedded in the elastomer  22 , such that, the nanoparticles  42  interface with a surface  54  of the elastomer  22 . Having the nanoparticles  42  interface with the surface  54  allows a decrease in 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 nanoparticles  42 , embedded within the elastomer  22 , decrease the hysteresis energy and heat generation resulting therefrom. 
         [0016]    The nanoparticles  42  can consist of various materials with a primary characteristic being a thermal conductivity thereof that is greater than a thermal conductivity of the elastomer  22 . As such, the nanoparticles  42  can be from the carbonaceous family of materials including, carbon nanotubes (CNT), single-walled carbon nanotubes (SWCNT), double-walled carbon nanotubes (DWCNT), and non-nanotube configurations such as graphenes, fullerenes and diamonds, for example. The nanoparticles  42  can also be noncarbonaceous and include materials such as copper, silver, aluminum or nitrides as in boron nitride (BN), and aluminum nitride (AlN). Additionally, the nanoparticles  42  can be a mixture of one or more of the foregoing materials. 
         [0017]    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.