You are an expert at summarizing long articles. Proceed to summarize the following text:

You are an expert at summarizing long articles. Proceed to summarize the following text: 
BACKGROUND 
       [0001]    During the conveyance of wireline tools, the toolstring is often subjected to friction. To make conveyance of wireline tools more efficient and reduce the risk of sticking during conveyance, rollers are often used with the toolstring. The rollers are often retained using external mechanism; however, these mechanisms are hard to maintain and take up significant space. 
       SUMMARY 
       [0002]    An example downhole roller includes a body. The body has a wheel connected therewith. A bearing assembly is disposed between the body and the wheel to allow the wheel to move relative to the body. An internal shaft is located between the wheel and the bearing assembly. The internal shaft holds the bearing assembly in place. 
         [0003]    An example method of conveying a tool into a wellbore includes connecting a toolstring with a downhole roller. The downhole roller includes a body with a wheel connected therewith. A bearing assembly is disposed between the body and the wheel to allow the wheel to move relative to the body. The downhole roller also includes an internal shaft between the wheel and the bearing assembly, and the internal shaft holds the bearing assembly in place. The method also includes running the toolstring and downhole roller into the wellbore. 
         [0004]    An example system for conveying a tool into a wellbore includes a downhole roller. The downhole roller includes a body with a wheel connected therewith. A bearing assembly is disposed between the body and the wheel to allow the wheel to move relative to the body. The downhole roller also includes an internal shaft between the wheel and the journal assembly, and the internal shaft holds the bearing assembly in place. The example system also includes a toolstring having at least one downhole tool. A conveyance is connected with the toolstring. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0005]    The present disclosure is best understood from the following detailed description when read with the accompanying figures. It is emphasized that, in accordance with the standard practice in the industry, various features are not drawn to scale. In fact, the dimensions of the various features may be arbitrarily increased or reduced for clarity of discussion. 
           [0006]      FIG. 1  depicts an example system for conveying a tool into a wellbore. 
           [0007]      FIG. 2  depicts an example downhole roller. 
           [0008]      FIG. 3  depicts an example roller having retaining lips formed on a surface thereof 
           [0009]      FIG. 4  depicts an example standoff having retaining lips formed on a surface thereof 
           [0010]      FIG. 5  depicts an example method of conveying a downhole tool. 
       
    
    
     DETAILED DESCRIPTION 
       [0011]    It is to be understood that the following disclosure provides many different embodiments, or examples, for implementing different features of various embodiments. Specific examples of components and arrangements are described below to simplify the present disclosure. These are, of course, merely examples and are not intended to be limiting. In addition, the present disclosure may repeat reference numerals and/or letters in the various examples. This repetition is for the purpose of simplicity and clarity and does not in itself dictate a relationship between the various embodiments and/or configurations discussed. 
         [0012]      FIG. 1  depicts an example system for conveying a tool into a wellbore. The system  100  includes a conveyance  110 , a toolstring  120 , one or more downhole rollers  130 , and one or more downhole tools  140 . The conveyance  110  can be a slickline, wireline, coil tubing, drill string, or the like. 
         [0013]    The toolstring  120  can have one or more segments. The segments can include electronic modules, hydraulic modules, sensors, and communication equipment. 
         [0014]    The downhole roller  130  can have one or more wheels connected with a body. The body can be configured to connect about the toolstring  120 . The downhole roller  130  can reduce friction between the toolstring  120  and wellbore walls  150  during conveyance. The downhole roller  130  can also mitigate sticking by preventing damage to mud on the side of the wellbore walls  150 , thereby preventing differential pressure sticking. 
         [0015]    The downhole tool  140  can be a milling tool, a cutting tool, a shifting tool, an anchor, a tractor, a perforating gun, a logging tool, or the like. 
         [0016]      FIG. 2  depicts an example downhole roller. The downhole roller  200  includes a body  220 , one or more wheels  210 , one or more internal shafts  250 , one or more outer journal bearings  240 , one or more retaining rings  242 , one or more static seals  270 , one or more inner journal bearings  230 , one or more rotating seals  260 , and one or more locking pins  280 . 
         [0017]    The body  220  can have a wheel  210  connected on one side thereof and another wheel connected on the other side. Both wheels can be connected to the body in the same way; however, a detail of the wheel connection is only shown for one of the wheels  210 . 
         [0018]    The wheel  210  can be connected with the body  220  by a bearing assembly that includes an inner journal bearing  230  and an outer journal bearing  240 . The inner journal bearing  230  can be placed about a threaded cylinder  222  connected with the body  220 . A static seal  270  can be placed about the shaft  250 , and the static seal can seal against a land in the threaded cylinder  222 . The internal shaft  250  can be threaded to the threaded cylinder  222 , holding the journal bearings  230  and  240  in place. The lock pin  280  can be engaged with the internal shaft  250  to prevent the internal shaft from unthreading. 
         [0019]    The body  220  can have the rotating seal  260  located thereon. The rotating seal  260  can be on a rotating bearing. 
         [0020]    The wheel  210  can be placed about the bearing assembly and a retaining ring  242  can hold the wheel  210  in place. Accordingly, the outer journal bearing  240  can rotate about the inner journal bearing  230 , allowing the wheel  210  to rotate relative to the body  220 . The key  241  can prevent the outer journal bearing from rotating relative to the wheel  210 . 
         [0021]      FIG. 3  depicts an example roller having retaining lips formed on a surface thereof 
         [0022]    The roller  200  can have a body  220 . The body  220  has one or more retaining lips  322  and  324  located thereon. The retaining lips  322  and  324  can be formed, connected with, or otherwise located on the body  220 . The lips  322  and  324  can be configured to fit in retaining grooves  122  and  124  formed on a toolstring  120 . The upper retaining lip  322  can be larger than the retaining lip  324  and act as a point of retention to prevent substantial axial movement of the body  220  relative to the toolstring  120 . The lower retaining lip  324  can be smaller and act as a failsafe to prevent incorrect installation onto the toolstring  120 . For example, the lower retaining lip  324  can be spaced from the upper lip so that if the roller is installed the wrong direction on the toolstring  120 , the lower retaining lip will act as a stop on the toolstring and prevent the pin end  326  from closing, thereby preventing installation of the roller onto the toolstring  120 . 
         [0023]    A similar method can be used with other accessories, for example a standoff can be formed with retaining lips formed thereon and the toolstring can have similar grooves. 
         [0024]      FIG. 4  depicts an example standoff having retaining lips formed on a surface thereof The standoff  400  can include a standoff boy  420 . The standoff body  420  can have one or more retaining lips  422  formed on an interior thereof The standoff  400  can be connected about a tubular  410 . The tubular  410  can have one or more retaining groves  412  configured to operatively cooperate with the retaining lips  422  to prevent axial movement of the standoff on the tubular  410 . 
         [0025]      FIG. 5  depicts an example method of conveying a downhole tool. The method  500  includes connecting a toolstring with a downhole roller, Box  510 . The downhole roller can be any roller described herein or substantially similar downhole rollers. The downhole roller can be connected with the toolstring using a hinge pin design. For example, the downhole roller can be hinged at one end and pinned at the other end; the pin can be removed allowing the pinned end to open allowing the downhole roller to be placed about the toolstring, and after being placed about the toolstring, the pinned end can be closed and the pin inserted therein preventing the pin end from opening. The method can also include running the toolstring and downhole roller into the wellbore, Box  520 . 
         [0026]    The preceding description has been presented with reference to certain embodiments. Persons skilled in the art and technology to which these embodiments pertain will appreciate that alterations and changes in the described structures and methods of operation may be practiced without meaningfully departing from the principle, and scope of these embodiments. For example, while techniques utilized are directed at jacketing a metal core for an oilfield conveyance or line, these techniques may be modified and applied to other hardware such as metallic tool housings. Regardless, the foregoing description should not be read as pertaining only to the precise structures described and shown in the accompanying drawings, but rather should be read as consistent with and as support for the following claims, which are to have their fullest and fairest scope.

Summary:
A downhole roller having a body. The downhole roller also has a wheel connected with the body, and a bearing assembly disposed between the body and the wheel to allow the wheel to move relative to the body. The downhole roller can also have an internal shaft between the wheel and the bearing assembly, wherein the internal shaft holds the bearing assembly in place.