Abstract:
An intelligent downhole impact jar device is described that is able to sense well bore angle or deviation and alter the effective jar impact load based upon the sensed information. The impact jar device includes a jarring portion for creating jarring impacts within a wellbore toolstring. The jarring portion is adjustable so that jarring forces of various levels can be produced. The jarring portion is adjusted in response to sensed wellbore conditions, such as the angle of deviation of the surrounding wellbore.

Description:
This application claims the benefit of U.S. Provisional Patent Application Ser. No. 60/843,256 filed Sep. 8, 2006. 

   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates generally to mechanical jars that perform impact-related forces on a tool string downhole in hydrocarbon wells, water wells, or other well applications. 
   2. Description of the Related Art 
   Well operations often require the use of devices that provide an “impact” on a tool string or a downhole production device. Certain types of downhole tools require the shearing of screws or pins to either set or release a device. A downhole packer or bridge plug, for example, may be run into a wellbore on wireline and then set in place within the is wellbore by shearing screws on the run-in tool. To do this, an impact load will need to be delivered to the run-in tool that is sufficient to cause shearing to occur. In other applications, a device that is being installed in or removed from a production string by wireline or coiled tubing may require impacts to properly install or remove it. For example, gas-lift valves are typically installed in and removed from the pocket of a gas-lift mandrel by a wireline tool. Removing the gas lift valve from the pocket requires the application of an impact force to unseat the valve from the pocket. 
   Typically, a mechanical, hydraulic or spring-type jarring tool is used to deliver the impact forces for these situations. With these tools, the impact force is predetermined and calibrated at the surface prior to running the jarring tool in to the wellbore. However, the actual impact force that will be delivered while in the hole will vary depending upon the various well environments and geometries that exist. One important aspect of wellbore geometry is wellbore angle or deviation. Wellbore deviation applies increased friction forces on the tool string and thereby results in reduced impact forces being applied by the jarring tool. In particular, spring jars require pre-set calibration at the surface by manually applying torque to the spring mechanism prior to running the tool in. However, this is not optimal where the wellbore angle is unknown or if wellbore angle changes along the length of the wellbore. 
   SUMMARY OF THE INVENTION 
   An intelligent downhole impact jar device is described that is able to sense well bore angle or deviation and alter the effective jar impact load based upon the sensed information. In an exemplary embodiment, the impact jar device includes a jarring portion for creating jarring impacts within a wellbore toolstring. The jarring portion is adjustable so that jarring forces of various levels can be produced. The device also includes a sensor for determining a wellbore condition, principally the angle of deviation of the surrounding wellbore, and generating a signal indicative of the wellbore condition. In addition, the impact jar device includes a controller to receive the signal from the sensor and adjust the jarring portion to produce a jarring impact of suitable force to match the wellbore condition. For example, if the wellbore is deviated and the jarring force provided by the impact jar will be reduced by the deviation, the controller will adjust the jarring assembly so as to correspondingly increase the force of the jarring impact the jarring assembly will create, thereby increasing the effective jarring force to compensate for the wellbore deviation. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     For detailed understanding of the invention, reference is made to the following detailed description of the preferred embodiments, taken in conjunction with the accompanying drawings in which reference characters designate like or similar elements throughout the several figures of the drawings. 
       FIGS. 1A-1C  present a side, cross-sectional view of an exemplary intelligent impact jar tool constructed in accordance with the present invention, and in a run-in position. 
       FIGS. 2A-2C  present a side, cross-sectional view of the impact jar tool of  FIGS. 1A-1B , now with the jar having been actuated in preparation for a jar impact. 
       FIGS. 3A-3C  depict the impact jar tool of  FIGS. 1A-1B  and  2 A- 2 B during jarring. 
       FIGS. 4A-4C  illustrate the impact jar tool now being adjusted for downhole angle. 
       FIG. 5  is an illustration of an exemplary controller constructed in accordance with the present invention. 
       FIG. 6  is a diagram depicting operational steps taken by the controller to adjust the impact jar jarring force to compensate for deviations in wellbore deviation angle. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIGS. 1A-1D  illustrate an exemplary intelligent impact jar device  10 , which is adapted to be secured within a production string (not shown) in a wellbore. The jar device  10  includes an outer tubular housing, generally indicated at  12 , that defines a bore  14  along its length. The bore  14  includes upper and lower enlarged diameter upsets  16 ,  18  proximate its upper end  20 . The upper end  21  of the housing  12  has a reduced diameter neck  23 . The housing  12  is attached at its lower end  22  to a lower end sub  24 . 
   Disposed radially within the bore  14  of the housing  12  is an impact anvil  26  having a reduced diameter shaft portion  28 , an enlarged diameter anvil portion  30  and a retaining portion  32 . An equalizing passage  34  is defined within the impact anvil  26  and extends between port openings  36 ,  38 , and  40 . The retaining portion  32  of the anvil  26  carries a release bearing  42  having a collar  44  and ball bearings  46 . The release bearing  42  is removably secured to the retaining portion when the ball bearings  46  reside within a complimentary annular relief  50 , which is visible in  FIG. 3B . The upper end of the anvil  26  is affixed to a top sub  48 , which has a connection suitable for attaching the jar device  10  to a desired wireline or coiled tubing running arrangement (not shown). 
   The release bearing  42  is secured by threading or similar fashion to spring housing  52 , which resides within bore  14 . Within the spring housing  52  is a compressible spring  54 . In a currently preferred embodiment, the spring  54  is made up of stacked Belleville washers. However, a coiled spring or fluid spring may be used as well. A spring compression member, or rod,  56  is disposed within the spring housing  52  as well and extends through the lower axial end of the spring housing  52 . The lower end of the compression rod  56  is secured to the spindle of rotary motor  58 . The motor  58  is secured within the bore  14  below the spring housing  52 . Spring  60  is disposed between the spring housing  52  and the motor  58 . A battery pack or other power supply  62  provides power for the motor  58  to operate. The upper end of the compression rod  56  has an enlarged compression head  64  that is located above the spring  54 . Compression of the spring  54  by the spring compression rod  56  and affixed head  64  pre-tensions the release bearing  42  upon the retaining portion  32  of the impact anvil  26 . The compression rod  56  also includes a screw shaft  65 , which is the portion that is affixed to the rotary spindle of the motor  58 . Rotation of the screw shaft  65  in one direction by the motor  58  will shorten the screw shaft  65  and cause the compression head  64  to compress the spring  54 . Rotation of the screw shaft  65  in the opposite direction will uncompress the spring  54 . When the spring  54  is compressed by the motor  58 , the jar force provided by the tool  10  is increased due to increased spring loading and pre-tensioning. Conversely, when the spring  54  is uncompressed, by operation of the motor  58  in reverse, the jar force provided by the tool  10  is decreased. 
   During run-in, the jar device  10  is in the configuration shown in  FIG. 1A-1C . In order to cause the jar device  10  to create an impact, the top sub  48  is pulled upwardly, drawing the anvil  26  upwardly with respect to the housing  12  to place the anvil  26  in tension. When the anvil  26  reaches the position shown in  FIGS. 2A-2C , the ball bearings  46  of the release bearing  42  will encounter the enlarged diameter upset  16 . The ball bearings  42  will move radially outwardly into the upset  16  and allow the retaining portion  32  of the anvil  26  to be move out of the relief  50  on the retaining portion  32 . As a result, the retaining portion  32  is released from attachment to the release bearing  42  and spring housing  52  (see  FIG. 3B ). This release will happen very quickly, as the anvil  26  is pulled upwardly in tension. When the anvil  26  is released from the release bearing, the enlarged portion  30  of the anvil  26  will strike against the upper end  20  of the bore  14 , as shown in  FIG. 3A . This striking action creates the jarring impact that the tool  10  is intended to deliver. The presence of the equalizing passage  34  and ports  36 ,  38 ,  40  will permit the anvil  26  to move within the bore  14  of the housing  12  without hindrance by fluid pressure differentials that might otherwise prevent the desired impact jar from occurring. 
   Following the jar impact described above, the tool  10  must be reset before a second impact can be performed. To reset the tool, the anvil  26  is moved axially downwardly with respect to the housing  12 . The retaining portion  32  is reinserted into the release bearing  42  and urge the release bearing  42  and affixed spring housing  52  axially downwardly within the housing  12 . This downward movement of the anvil  26  will be resisted by the compression spring  60 , which will compress during the downward movement. As the release bearing  42  enters the lower upset  18 , the ball bearings  46  of the release bearing  42  can move radially outwardly into the upset  18 , thereby allowing the retaining portion  32  to be moved within the release bearing  42  to a point wherein the ball bearings  46  will become aligned with its relief  50 . At this, point the spring  60  may decompress to urge the spring mandrel  52  and anvil  26  axially upwardly with respect to the housing  12 . The release bearing  42  will move out of the enlarged diameter upset  18  and is into a restricted diameter portion  66  of the bore  14  located between the upper and lower upsets  16 ,  18 , thereby securing the anvil  26  to the release bearing  42  and the spring housing  52 . Following this resetting, the jarring tool  10  may be again actuated to cause an impact jar, as described previously. 
   The jar device  10  is also capable of self-adjustment to alter the amount of impact force that is delivered by the jar device  10 . A controller  68  is operably associated with the motor  62  and governs the adjustment of the impact jar force via adjustment of the compression spring  54  by compression rod  56  and motor  62 . Upon receipt of a suitable command from the controller  68 , the motor  62  will rotate the screw shaft  65  in order to adjust the jarring force (either increase or decrease) that will be provided by the tool  10 . In a currently preferred embodiment, depicted schematically in  FIG. 5 , the controller  68  comprises a circuit board  69  having an on-board inclinometer  70  that is capable of detecting the angle from the vertical at which the tool  10  is oriented. Inclinometers of this type are available commercially from a number of commercial sources, including various suppliers of MEMS (microelectromechanical systems) devices, such as Analog Devices of Norwood, Mass. In a currently preferred embodiment, the inclinometer  70  is a spring system made of silica. The controller  68  is also provided with a processor  72  that receives the data obtained by the inclinometer  70  and determines the amount of adjustment that is needed to be made to the compressible spring  54  to compensate in the loss effective jarring force resulting from the deviation angle of the surrounding wellbore. The controller  68  is also capable of providing a command signal to the motor  58  to cause the motor  58  to operate in a particular manner. 
   The controller  68  is preprogrammed at the surface with the parameters necessary to allow the controller  68  to determine the amount of frictional losses upon the impact jar device  10  as a result of deviations in the angle of the surrounding wellbore as measured by the inclinometer  70 . These parameters will likely include the weight of the jar tool  10  and associated components as well as the coefficient of friction for the material making up the surrounding wellbore or wellbore casing (either measured or obtained from widely-available reference sources). 
   Exemplary operation of the controller  68  to adjust the impact force of the jar tool  10  is depicted schematically in  FIG. 6 . According to step  82  of the process  80 , the inclinometer  70  detects the angle of deviation of the surrounding wellbore from the vertical and transmits this information to the controller  68 . In step  84 , the controller  68  determines an approximated amount of impact force loss due to the angular deviation. The determination of force loss may be done by applying known frictional coefficients and friction determination equations to calculate, from the detected angle of deviation and the known material of the surrounding wellbore, a friction force loss amount. For example, if the surrounding wellbore is lined with iron casing sections, an approximate kinetic frictional coefficient (μ) of 0.20 (obtained from published source materials) can be used by the controller  68  to determine the amount of force that is necessary to overcome the frictional losses from the angled deviation of the wellbore. In this example, if the inclinometer  70  were to determine that the impact jar tool  10  were deviated, say 10 degrees from the vertical, the friction force loss due to the deviation could be determined by the equation:
 
F 1 =Nμ where:
         F 1  is the friction force loss (i.e., the frictional force resisting motion of the impact jar tool  10 );   N is the component of force exerted upon the wellbore surface by the weight of the tool  10 ; and   μ is the coefficient of friction.       

   In step  86 , the controller  68  provides a command to the motor  58  to increase the compression of the spring  54  by rotation of the screw shaft  65  to cause the compression head  64  to compress the spring  54 , thereby creating a pre-tension condition upon the impact anvil  26 . As the spring  54  is axially compressed (see  FIG. 2B ), the force with which the impact anvil  26  will impact the upper end  20  of the bore  14  of housing  12  will be correspondingly increased. This process may be repeated by the controller  68 , as illustrated by arrow  88  in  FIG. 6 , to provide for a constantly updating, iterative process that is repeated in accordance with a programmed timed cycle. 
   The necessary wiring and programming needed to accomplish the above-described steps  82 ,  84 , and  86  will be apparent to those of skill in the art of programming microprocessors. The controller  68  is preferably programmed with the desired parameters prior to running the tool  10  into a wellbore. To do this, a serial interface port  90  is provided which allows the controller  68  to be connected up to a programming computer at the surface of the well prior to running the tool  10  into the well. 
   Those of skill in the art will recognize that, although the present invention is shown and described in a limited number of forms herein, it is amenable to various changes and modifications without departing from the scope and spirit of the invention.