Abstract:
A wellbore instrument includes a housing configured to traverse a subsurface wellbore. A shock and vibration sensor disposed in the housing and is mounted on a carrier disposed in the housing. The carrier includes at least two, laterally movable elements each having an outer surface configured to contact an inner surface of the housing. The carrier includes an adjustable wedge disposed between the opposed elements. The wedge is arranged such that longitudinal movement thereof causes lateral separation of the laterally movable elements into frictional engagement with the inner surface of the housing.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]    Priority is claimed from U.S. Provisional Application No. 61/107,202 filed on Oct. 21, 2008. 
     
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
       [0002]    Not Applicable 
       BACKGROUND OF THE INVENTION 
       [0003]    1. Field of the Invention 
         [0004]    The invention relates generally to the field of instruments used to make measurements in subsurface wellbores. More specifically, the invention relates to structures for mounting shock and vibration sensors in such instruments to provide a more accurate indication of shock and vibration actually experienced by such instruments. 
         [0005]    2. Background Art 
         [0006]    Certain types of instruments are used to make measurements from within wellbores drilled through subsurface rock formations. Such instruments may be conveyed through the wellbore by various devices known in the art including armored electrical cable (“wireline”), slickline, coiled tubing, production tubing and by drill string. In the latter conveyance, certain of such instruments may be configured to make measurements during the actual drilling of the wellbore. Moving instruments along the interior of a wellbore, in particular during drilling, as well as handling and transportation to the well site, can impart shock and vibration to the instruments. 
         [0007]    There is a need to properly characterize the shock and vibration levels that such instruments experience. Only through proper characterization of the shock and vibration environment to which such instruments are exposed can more accurate shock and vibration testing specifications be developed. More accurate shock and vibration testing specifications may assist in the design of more robust wellbore instruments. 
         [0008]    A shock and vibration environmental recorder has been developed for placement inside a wellbore instrument. One such recorder is sold under model designation “SAVER 3×90” by Lansmont Corporation, Ryan Ranch Research Park, 17 Mandeville Court, Monterey, Calif. 93940. The shock and vibration recorder generally consists of triaxial accelerometers, analog to digital converters and appropriate analog and digital processing circuitry and digital memory or other data storage to store the measurements made for a selected time period. 
         [0009]    However, such recorders cannot simply be placed in or on a tool and accurately characterize the shock and vibration experienced by the instrument. The sensing elements in a shock and vibration recorder are typically accelerometers that are mounted on a circuit board. The circuit board having the accelerometers must be mounted inside the instrument housing in a way that assures adequate mechanical coupling between the instrument housing and the circuit board. 
         [0010]    It is known in the art to directly mount accelerometers and strain gauges directly on the instrument housing. While effective, such mounting can make servicing the instrument more difficult and expensive. 
         [0011]    There exists a need for devices to mount shock and vibration sensors (e.g., accelerometers) that make instrument assembly convenient and accurate, and provide sensor mounting to the instrument housing that efficiently transfers acceleration from the housing to the shock and vibration sensors. 
       SUMMARY OF THE INVENTION 
       [0012]    A wellbore instrument according to one aspect of the invention includes a housing configured to traverse a subsurface wellbore. A shock and vibration sensor is disposed in the housing and is mounted on a carrier disposed in the housing. The carrier includes at least two, laterally movable elements each having an outer surface configured to contact an inner surface of the housing. The carrier includes an adjustable wedge disposed between the opposed elements. The wedge is arranged such that longitudinal movement thereof causes lateral separation of the laterally movable elements into frictional engagement with the inner surface of the housing. In one example, longitudinal movement of the wedge may be performed by rotating a screw that threadedly engages an interior passage in the wedge. 
         [0013]    In another example, a downhole tool comprising a shock and vibration recorder is provided. In various examples, the downhole tool comprising a shock and vibration recorder may be a wireline tool, a drill string or a logging while drilling tool. 
         [0014]    A method for assembling a shock, acceleration and vibration sensing recorder to a well logging instrument according to another aspect of the invention includes inserting chassis components into a housing by sliding longitudinally therein to a selected position. The chassis components include a shock, acceleration and vibration sensor disposed in a carrier. The carrier is laterally expanded into frictional engagement with an interior surface of the housing. 
         [0015]    The invention also provides a method of characterizing the shock and vibration levels that a downhole tool encounters during transportation, handling, rig up/down, and downhole operations comprising providing said downhole tool with a shock and vibration recorder, and transporting, handling, performing rig up/down procedures, and downhole operations with such downhole tool. This method may be used where the tool is a wireline tool, a drill string or a logging while drilling tool. 
         [0016]    The invention also provides a method for mounting a board with accelerometers inside a downhole tool housing that assures adequate mechanical coupling to allow high quality shock and vibration measurements. This method may be used where the tool is a wireline tool, a drill string, coiled tubing or a logging while drilling tool, or a tool conveyed into a wellbore by any means known in the art 
         [0017]    The invention also provides a system for attaching a recorder to a downhole tool housing using a wedge system to push a board with accelerometers against the tool&#39;s housing. 
         [0018]    In one example, the invention provides a system wherein the wedge system is activated with a screw after the tool has the tool chassis installed inside its housing. In some examples the activation may be performed in a way the optimizes the axial loading capability of the instrument without decreasing the instrument pressure rating (in other words, just tight enough to provide grip but without affecting the mechanical integrity of the tool housing it is mounted within. 
         [0019]    Other aspects and advantages of the invention will be apparent from the following description and the appended claims. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0020]      FIG. 1  shows a wireline conveyed instrument including a shock and vibration recorder. 
           [0021]      FIG. 2  shows a measurement and/or logging while drilling (drill string conveyed) instrument including a shock and vibration recorder. 
           [0022]      FIG. 3  shows an example carrier for a shock and vibration recorder (sensor assembly) in side view disposed in an instrument housing. 
           [0023]      FIG. 4  shows an oblique view of the assembled carrier. 
           [0024]      FIG. 5  shows an oblique view of the circuit board holding component of the carrier. 
           [0025]      FIG. 6  shows an example of a triaxial accelerometer measurement circuit board on the left, and a controller circuit board on the right. 
           [0026]      FIG. 7  shows a lower connector head for a wireline instrument that includes access to the wedge screw of  FIG. 3 . 
           [0027]      FIG. 8  shows an assembled wireline tool including a shock and vibration recorder according to the various aspects of the invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0028]    One example of a wellbore instrument is shown schematically in  FIG. 1  at  10 . The instrument  10  can be configured to make any type of measurement known in the art from within a wellbore  14  drilled through subsurface rock formations  11 . Without limitation, examples of such measurements include electrical resistivity, naturally occurring gamma radiation, neutron capture cross section, neutron hydrogen index, gamma gamma density, acoustic compressional and shear velocities, and samples of fluid and pressures thereof from the formation. 
         [0029]    The instrument  10  includes a shock and vibration recording sensor  12  according to various aspects of the invention that will be explained in more detail below. The instrument  10  may be transported to the wellbore, “rigged up” and then conveyed along the wellbore  14  using, in the present example, an armored electrical cable  16 . The cable  16  may be extended into and retracted from the wellbore  14  using a winch  18  or similar spooling device known in the art. Signals from various sensors including those in the shock and vibration recording sensor  12  may be communicated along the cable  16  for recording and/or processing in a recording unit  20  disposed at the surface. In other examples, the cable  16  may be substituted by “slickline.” Accordingly, wireline conveyance is not a limit on the scope of the present invention. Because the shock and vibration recording sensor  12  may be configured to store signals locally, it may not be necessary in certain examples, to transmit measurements from such sensors  12  to the surface recording unit while the instrument  10  is in the wellbore  14 . The sensors  12  may be interrogated after the instrument  10  is withdrawn from the wellbore  14 . 
         [0030]      FIG. 2  shows an example measurement while drilling (MWD) or logging while drilling (LWD) instrument  25  disposed in a drill string  24 . “MWD” instruments are generally understood to be those types of instruments that make measurements corresponding to certain drilling parameters such as the geodetic trajectory of the wellbore, and mechanical drilling parameters affecting the drill string  24 , e.g., torque and axial load (weight on bit). “LWD” instruments are generally understood to be those which make petrophysical parameter measurements of the types explained above with reference to  FIG. 1 . The present shock and vibration recording sensor is equally usable with MWD and LWD instruments. Accordingly, the types of measurements made in a drill string conveyed measurement system by the instrument  25  that are made in addition to the shock and vibration measurements are not intended to limit the scope of the invention. 
         [0031]    The drill string  24  is generally assembled from segments (“joints”)  23  of pipe threadedly connected end to end. A drill bit  26  is typically disposed at the bottom of the drill string  24  and is axially urged and rotated to lengthen (drill) the wellbore  14 . The instrument  25  may also include a shock and vibration recorder. In the present example, the drill string  24  is suspended by a top drive  30  disposed in a hoisting unit such as a drilling rig  28 . During drilling, a pump  36  lifts drilling fluid  32  (“mud”) from a tank  34  and pumps it through an internal passage in the drill string  24 . The mud  32  eventually leaves the drill string  24  through courses or nozzles (not shown) in the drill bit, whereupon it lifts drill cuttings as the mud  32  returns to the surface. The instrument  25  may be configured to modulate the flow of mud  32  in the drill string  24  so as to communicate signals from the instrument  25 , including from the shock and vibration recorder  12 , to a recording unit  20 A at the surface  22 . The modulation may be detected by one or more pressure transducers  38  disposed in the discharge line from the pump  36 . Other techniques for communicating signals include using so-called “wired” drill pipe. Examples of such pipe are described in U.S. Pat. No. 6,641,434 issued to Boyle et al. and commonly owned with the present invention. As explained above with reference to  FIG. 1 , it may be unnecessary to transmit the shock and vibration measurements to the surface during the time the instrument  25  is in the wellbore. The instrument  25  may be interrogated after removal from the wellbore  14  because the instrument may have local data recording capability. 
         [0032]    Irrespective of the type of instrument conveyance, proper operation of the shock and vibration recording sensor  12  requires good mechanical coupling between the sensing elements (typically being one or more circuit boards that include accelerometers to measure acceleration in mutually orthogonal directions) and the instrument housing. By such good mechanical coupling, it is believed that a more accurate characterization may be made of the shock and vibration experienced by the instrument because any mechanical contamination of the recorded vibration is minimized. 
         [0033]    An example carrier  13  for a shock and vibration recording sensor is shown in cross section in  FIG. 3 . The carrier  13  in the present example includes an upper carrier  42 , which has a receptacle  42 B for holding a sensor board  40 . In the present example, the sensor board  40  can be a triaxial accelerometer sensor assembly based on a recording sensor assembly sold under model designation SAVER 3×90 by Lansmont Corporation, Ryan Ranch Research Park, 17 Mandeville Court, Monterey, Calif. 93940. Such sensor board  40  typically includes three mutually orthogonal accelerometers, analog to digital conversion and signal processing circuitry, and a data recorder. The upper carrier  42  may include a radiused feature  42 A configured to contact with and conform to the inner surface of the instrument housing  10 A. Disposed laterally opposite to the upper carrier  42  may be a carrier base  50 . The carrier base  50  is also configured to contact and conform to the inner surface of the housing  10 A, typically diametrically opposite to the upper carrier  42 . The carrier base  50  and the upper carrier  42  may have opposed, tapered inner surfaces, shown at  51  and  53 , respectively. The opposed, tapered inner surfaces  51 ,  53  may be generally semi-conical in shape, or may be planar tapered, and provide a corresponding opening for a wedge  48 . The wedge  48  may be a generally conically or flat shaped wedge  48 . The wedge  48  may include a threaded, centrally disposed opening  48 A therethrough. A screw  46 , such as a socket head (Allen) screw may be disposed in the narrow end of the wedge opening  48 A, and supported, for example, by a thrust washer  44 . Upon rotation of the screw  46 , the wedge  48  is drawn longitudinally along the corresponding inner surfaces  51 ,  53 , causing the diameter traversed between the upper carrier  42  and the carrier base  50  to increase. Thus, by suitable operation of the screw  46 , the upper carrier  42  and carrier base  50  may become laterally displaced and thus tightly compressed against the inner surface of the housing  10 A. Such compression may enable efficient transfer of acceleration applied to the housing  10 A to the carrier  13  and thus to the accelerometers on the sensor board  40  for recording and analysis. 
         [0034]    The screw  46  may be covered by a cap  52  fastened to the ends of the upper carrier  42  to protect the screw  46  and parts of the carrier  42 ,  50  during operation. The cap  52  provides the function of allowing the screw  46  to push the wedge outwardly to release the carrier assembly  13  from the housing  10 A. As the screw  46  is reverse rotated, it moves closer to the cap  52 , then touches the cap. If reverse rotation of the screw  46  continues the cap  52  prevents the screw  46  from moving relative to carrier parts  42  and  50 , and creates a force that causes the wedge  48  to disengage from carrier  42  and  50 , thus releasing the carrier assembly  13  from the inner surface of the housing  10 A. 
         [0035]    A side view of the assembled carrier  13  is shown in  FIG. 4 . In the present example, the carrier  13  may include elastomer (e.g., rubber) plugs or stand offs to isolate the carrier  13  from acceleration transferred from electronic support chassis ( FIG. 8 ) and other components inside the housing ( 10 A in  FIG. 3 ). An upper oblique view of the carrier is shown in  FIG. 5 , wherein reliefs  43 A,  43 B,  43 C for components on the bottom of the sensor board ( 40  in  FIG. 3 ) can be observed. 
         [0036]    An oblique view of the sensor board  40  is shown in  FIG. 6 . The sensor board may be self-contained and may be powered, for example by using batteries. 
         [0037]    Some of the design considerations for this example of the wedge, upper carrier and carrier base to function optimally include the following. The taper angle of the wedge was chosen to maximize the normal force between the interior surface of the housing ( 10 A in  FIG. 3 ) and the carrier. Maximizing the normal force is used to provide enough friction to transfer acceleration efficiently, while at the same time keeping the normal force between the different parts of the carrier assembly low enough to minimize the probability of galling. Copper based alloys may be used in the wedge ( 48  in  FIG. 3 ) to further decrease the possibility of galling. The materials may also selected in such a way that under thermal expansion the wedge assembly increases the contact force with the housing  10 A. 
         [0038]    The carrier ( 13  in  FIG. 3 ) relies on friction to hold it in place during shocks, particularly in the direction of the longitudinal axis of the instrument housing ( 10 A in  FIG. 3 ). Therefore the contact surfaces between the upper carrier ( 42  in  FIG. 3 ) and the inner surface of the housing ( 10 A in  FIG. 3 ) and the inner surface of the housing and the carrier base ( 50  in  FIG. 3 ) require rougher surface finish than ordinarily finished machined metal parts would have to increase the acceleration levels that the device can sustain without slippage. Such extra roughness may be limited only to the portions of the interior of the housing ( 10 A in  FIG. 3 ) where the carrier  13  will be positioned in order to minimize additional friction to other components to be inserted into the housing. 
         [0039]    The weight of the carrier  13  can be minimized, e.g., by selecting a shape to cover only a limited portion of the circumference of the interior of the instrument housing ( 10 A in  FIG. 3 ) to decrease the inertial forces experienced during high level shocks, while retaining the rigidity of the assembly to avoid compromising the acceleration measurements quality. 
         [0040]    The radii of the upper carrier ( 42  in  FIG. 3 ) and carrier base ( 50  in  FIG. 3 ) surfaces that contact the inner surface of the instrument housing ( 10 A in  FIG. 3 ) should be as closely matched as possible to the radius of the inner surface of the instrument housing ( 10 A in  FIG. 3 ) to maximize contact area, but should also be selected such that the upper carrier assembly and the carrier base contact the housing inner surface along two circumferentially displaced, essentially parallel lines (on the sides) rather than along the center line. Such contact will provide lateral stability of the carrier assembly and will lessen the possibility of incorrectly measured lateral shock and vibration. 
         [0041]    An example of a conventional wireline multiple pin lower electrical connector  70  is shown disposed inside the housing  10 A. The present example connector is modified to include an opening  71  in the connector  70  to provide access to the wedge locking and unlocking screw ( 46  in  FIG. 3 ), and access to a USB port  72  on the sensor board ( 40  in  FIG. 3 ). In the present example, and referring to  FIG. 8 , an instrument chassis set, which may include batteries  65  and main circuits  67  may be assembled with the carrier  13  conventionally by sliding all the foregoing into their correct respective positions in the housing  10 A. The wedge screw ( 44  in  FIG. 3 ) may be tightened using the access hole ( 71  in  FIG. 7 ) in the lower connector ( 70  in  FIG. 7 ), thus locking the carrier  13  in place. 
         [0042]    The foregoing assembly was subjected to shock and vibration testing. The carrier ( 13  in  FIG. 3 ) did not move with respect to the housing ( 10 A in  FIG. 3 ) throughout shock and vibration testing, assuring a transmissibility of 100% of the acceleration from the housing to the carrier. Likewise, the screw ( 44  in  FIG. 3 ) did not lose any of the torque applied at installation even after a large number of repeated high level shocks as well as intense vibration testing. 
         [0043]    A shock and vibration sensor and carrier made according to the various aspects of the invention may facilitate instrument assembly and service, while providing accurate measurement of the shock and vibration forces experienced by the instrument. 
         [0044]    While the invention has been described with respect to a limited number of embodiments, those skilled in the art, having benefit of this disclosure, will appreciate that other embodiments can be devised which do not depart from the scope of the invention as disclosed herein. Accordingly, the scope of the invention should be limited only by the attached claims.