Patent Publication Number: US-2011061934-A1

Title: Vibration Damping Tool for Downhole Electronics

Description:
BACKGROUND 
     Downhole tools are subjected to substantial forces and vibration during drilling. Sensor packages and other sensitive downhole electronics, such as those housed in measurement-while-drilling (MWD) tools, steering tools, gyros, or logging-while-drilling (LWD) tools, are particularly vulnerable to damage from vibration and shock during drilling. Electronics in downhole tools are often mounted in ways that reduce the vibration and shock that is felt by the electronics, but ultimately the vibration and shock still reduce the life cycle of the electronics and add fatigue and wear to the bottom hole assembly. Reducing shock and vibration felt by the electronics extends their life cycle, which saves valuable time and money that would be spent replacing or repairing the directional sensors and electronics. Accordingly, additional measures to minimize shock and vibration that reaches electronics are valuable. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For a more detailed description of the embodiments, reference will now be made to the following accompanying drawings: 
         FIG. 1  is a schematic representation of a drilling system including a downhole tool with a shock reduction tool according to the principles disclosed herein; 
         FIG. 2  schematically illustrates a MWD tool including a shock reduction tool according to the principles disclosed herein; 
         FIGS. 3A-3F  are cross-sectional views of a shock reduction tool according to the principles disclosed herein; 
         FIG. 4  is a wire management section of a shock reduction tool according to the principles disclosed herein. 
     
    
    
     DETAILED DESCRIPTION OF THE DISCLOSED EMBODIMENTS 
     The present disclosure relates to a shock and vibration reduction tool (hereinafter “shock reduction tool”) for downhole tools with electronic or sensitive mechanical components. The drawings and the description below disclose specific embodiments with the understanding that the embodiments are to be considered an exemplification of the principles of the invention, and are not intended to limit the invention to that illustrated and described. Further, it is to be fully recognized that the different teachings of the embodiments discussed below may be employed separately or in any suitable combination to produce desired results. The term “couple,” “couples,” or “coupled” as used herein is intended to mean either an indirect or a direct connection. Thus, if a first device couples to a second device, that connection may be through a direct connection; e.g., by conduction through one or more devices, or through an indirect connection; e.g., by convection or radiation. “Upper” or “uphole” means towards the surface (i.e. shallower) in a wellbore, while “lower” or “downhole” means away from the surface (i.e. deeper) in the wellbore. 
     Referring now to  FIG. 1 , a drill string  10  is suspended in a wellbore  12  and supported at the surface  14  by a drilling rig  16 . The drill string  10  includes a drill pipe  18  coupled to a downhole tool assembly  20 . The downhole tool assembly  20  includes multiple (e.g., twenty) drill collars  22 , a measurement-while-drilling (MWD) tool assembly  1 , a mud motor  24 , and a drill bit  26 . The drill collars  22  are connected to the drill string  10  on the uphole end of the drill collars  22 , and the uphole end of the MWD tool assembly  1  is connected to the downhole end of the drill collars  22 , or vice versa. The uphole end of the mud motor  24  is connected to the downhole end of MWD tool assembly  1 . The downhole end of the mud motor  24  is connected to drill bit  26 . 
     The drill bit  26  is rotated by rotary equipment on the drilling rig  16  and/or the mud motor  24  which responds to the flow of drilling fluid, or mud, which is pumped from a mud tank  28  through a central passageway of the drill pipe  18 , drill collars  22 , MWD tool assembly  1  and then to the mud motor  24 . The pumped drilling fluid jets out of the drill bit  26  and flows back to the surface through an annular region, or annulus, between the drill string  10  and the wellbore  12 . The drilling fluid carries debris away from the drill bit  26  as the drilling fluid flows back to the surface. Shakers and other filters remove the debris from the drilling fluid before the drilling fluid is recirculated downhole. 
     The drill collars  22  provide a means to set weight off on the drill bit  26 , enabling the drill bit  26  to crush and cut the formations as the mud motor  24  rotates the drill bit  26 . As drilling progresses, there is a need to monitor various downhole conditions. To accomplish this, the MWD tool assembly  1  measures and stores downhole parameters and formation characteristics for transmission to the surface using the circulating column of drilling fluid. The downhole information is transmitted to the surface via encoded pressure pulses in the circulating column of drilling fluid. 
       FIG. 2  schematically illustrates the inside of MWD tool assembly  1 , in accordance with one embodiment. The MWD tool assembly  1  includes a collar  201  that includes a seat  230  in which an orienting sub  230  of an MWD tool  200  is disposed. Collar  201  is typically non-magnetic in order to allow measurements of the outside formation conditions to be taken by the MWD tool  200  from within the collar  201 . In the prior art, MWD tools often include multiple discrete modules that are electronically connected to form the MWD tool  200 . The multiple discrete modules are often connected using an interconnect module that provides electrical connectors and, optionally, a centralizer for centralizing the MWD tool  200  within the collar  201 . Embodiments of the present disclosure place a shock reduction tool  210  between at least two modules: lower module  202  and upper module  220 . Lower module  202  may include, for example, a pulser that produces pressure signals to transmit measurement data to the surface. Upper module  220  may include, for example, various sensors, such as directional sensors, microprocessors, and other electronic circuitry. Embodiments of the present disclosure are not limited to any particular combination of electronic modules for steering tools, MWD systems, LWD systems, or other downhole electronic systems. 
     Embodiments of the present disclosure provide a shock reduction tool that provides an electrical connection between at least two modules of a downhole tool, such as an MWD or LWD system. A cross-section of a shock reduction tool in accordance with one embodiment is shown in  FIGS. 3A-3F , with  FIG. 3A  at the upper end of the shock reduction tool and  FIG. 3F  at the lower end of the shock reduction tool in this embodiment.  FIG. 3A  is an end view of a male or female electrical connector  303  that connects to upper module  220 .  FIG. 3F  is an end view of a male or female electrical connector  304  that connects to lower module  202 . The electrical connectors  303 ,  304  may be any electrical connectors adapted for use with the modules  202 ,  220 . Common electrical connectors between MWD and LWD modules include MDM connectors. 
       FIG. 3B  includes an upper interconnect module  301 , which provides a sealed mechanical connection to the upper module  220 . Similarly,  FIG. 3E  includes a lower interconnect module  302 , which provides a sealed mechanical connection to the lower module  202 . The interconnect modules  301 ,  302  are selected according to the specifications of the modules  202 ,  220 . The interconnect modules  301 ,  302  are configured to be similar to commercially available interconnect modules. The electrical and mechanical components used for the commercially available interconnect modules are also commercially available. 
     From interconnect module  301 , wires  340  extend downward from electrical connector  303  into an interconnect crossover  343 . The wires  340  may terminate in a connector  341  with pins that pass through a pressure bulkhead feedthru  342 . The interconnect crossover  343  provides the mechanical connection between a body  350  of the shock reduction tool and the interconnect module  301 . In  FIG. 3C , wires  351  extend through the body  350  and through shock absorber section  330 . Embodiments of the present disclosure are not limited to any particular design for the shock absorber section  330 . One example of a shock absorber that may be adapted for use with embodiments of the present disclosure is the ELIMINATOR HYDRAULIC SHOCK TOOL available from THRU TUBING RENTAL (“TTR”) (Houston, Tex.). Any shock absorber design may be adapted for use with embodiments of the present disclosure so long as it contains a passage for wires  351  or other electrical conduit to pass through. 
     The axial distance between electrical connectors varies with the axial extension and compression of the shock absorber section  330  as it absorbs and dampens shock and vibration during the drilling process. As a result, the wires extending through the shock reduction tool must have length to extend at least the maximum length possible from extension of the shock absorber section  330 . Holding the wires in tension may lead to failure of the wires. Having extra slack in the wiring can lead to abrasion damage of the wires as the slack comes and goes with the changing axial length. 
     With these issues in mind, the shock reduction tool includes a wire management section  360 , an embodiment of which is shown in  FIG. 3D . In this embodiment, the wires  351  are contained in multiple sections of tubing  361 . The sections of tubing  361  may be formed from, for example, stainless steel. The sections of tubing  361  are helically wound inside of the wire management section  360 . Each section have tubing  361  may have multiple wires  351 . In one embodiment, there are four sections of tubing  361 , each with two wires  351  inside. The helically wound sections of tubing  361  may be nested within each other. The inside of the wire management section  360  may be pressure balanced and filled with dielectric fluid, such as oil, to lubricate and dampen the movement of the sections of tubing  361  as the helically wound portions extend and compress with the axial movement of the shock absorber section  330 . 
     The inside of the wire management section  360  may be at the ambient downhole pressure. The tubing  361  may be sealed within the wire management section  360  during assembly, which results in the inside of the tubing  361  having a lower pressure than the ambient downhole pressure. If sealed without any pressure compensation, the strength of tubing  361  is selected to withstand the crushing forces resulting from the pressure differential between the inside of tubing  361  and ambient downhole pressure. 
     On the lower end of the wire management section  360 , the wires  351  continue inside the tubing  361  to interconnect crossover  343 . The wires  351  continue to connector  341  and pass through pressure bulkhead feedthru  342  to connect with the wiring inside interconnect module  302 . 
     Although the embodiment in  FIGS. 3A-3F  is described in one orientation with  FIG. 3A  on the upper end and  FIG. 3F  on the lower end, those having ordinary skill in the art will appreciate that the shock reduction tool may be oriented in the opposite direction with the electrical connector ends reversed or with the wire management section  360  above the shock absorber section  330 . Further, more than one shock absorber section  330  may be included in the shock reduction tool, and the wire management section  360  may be disposed in between those two or more shock absorber sections  330 . 
     In  FIG. 4 , a wire management section  401  in accordance with another embodiment is shown. Instead of tubing, the wire management section  401  routes wires  402  through a flexible hydraulic hose  403 , which may be armored. Each of the wires  402  may route through the single flexible hydraulic hose  403 , or divided between multiple hydraulic hoses  403 . The flexible hydraulic hose  403  may terminate at opposing ends with AN fittings  405 , for example, to connect to other sections of the shock reduction tool. 
     Inside the wire management section  401 , the flexible hydraulic hose  403  is arranged into a loose knot  410 , which is a square knot in the embodiment shown in  FIG. 4 . As the ends of the hydraulic hose are pushed towards each other and pulled from each other with the travel of the shock absorber section, the loose knot  410  loosens and tightens within the constraints of the wire management section  401 . The loosening and tightening of the loose knot  410  provides sufficient travel for the wires  402  contained therein to avoid excessive tension on the wires  402 . Those having ordinary skill in the art will appreciate that other knot configurations may be used, or, alternatively, the hydraulic hose  403  may be arranged in a loop without being knotted. In one embodiment, at least a portion of the flexible hydraulic hose  403  may be coated or wrapped with a low friction and/or abrasion resistance coating, such as a shrink wrap Teflon® tube. The reduced friction allows for the loose knot  410  to loosen and tighten more freely within the wire management section  401  to avoid damage to the wires  402  contained therein. 
     The inside of wire management section  401  may be filled with fluid, such as oil, and exposed to ambient downhole pressure. The flexible hydraulic hose  403  may be fluidicly coupled to a pressure compensation chamber that allows for the inside of the flexible hydraulic hose  403  to balance with the ambient downhole pressure. At least some form of pressure compensation may be desirable because flexible hydraulic hose  403  generally has low resistance to collapse pressure. Pressure balancing reduces the pressure differential to a level that does not collapse the flexible hydraulic hose  403 . 
     The embodiments disclosed herein allow for multiple modules containing electronics to be electrically connected through a shock reduction tool disposed between at least two modules. The shock reduction tool reduces the shock and vibration experienced by the electronics in the modules while allowing for the modules to be electrically connected using common electrical connectors. The reduction in shock and vibration can increase the life expectancy of the modules relative to what their life expectancy would be if directly interconnected as in the prior art MWDs, LWDs, and other downhole electrical systems. 
     While specific embodiments have been shown and described, modifications can be made by one skilled in the art without departing from the spirit or teaching of this invention. The embodiments as described are exemplary only and are not limiting. Many variations and modifications are possible and are within the scope of the invention. Accordingly, the scope of protection is not limited to the embodiments described, but is only limited by the claims that follow, the scope of which shall include all equivalents of the subject matter of the claims.