Patent Number: 054254280
Section: description

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention furnishes an apparatus and method for facilitating the transport of a tool through a drill string in slimhole drilling operations. Referring to FIG. 1, a conventional "tool" or pipe joint is illustrated. As illustrated, pipe joint 10 includes threaded box 12 for rotatable connection with threaded nipple 14 of pipe joint 16. Bore 18 has a diameter less than the internal diameters of pipe joint 10 or pipe joint 16. In normal drilling operations, multiple pipe joints are connected to form a drill string, and a drill bit or drill rod section (not shown) is connected to the lower end of the drill string for cutting the desired borehole. Drilling fluid is circulated down through the interior of the drill string, through the drill bit, and returns to the well surface through the annulus between the drill string and the wellbore. FIG. 2 illustrates an embodiment of the present invention. First pipe section 20 defines an interior bore having a selected diameter. Second pipe section 22 similarly defines an interior bore for permitting the passage of tools and drilling fluid (not shown). Threaded nipple end 24 of first pipe section 20 is rotatibly connected with threaded box end 26 of second pipe section 22 to create pipe joint 28. As illustrated, pipe joint 28 includes bore 30 that has a diameter smaller than the interior diameters of first pipe section 20 and second pipe section 22. In one embodiment of the invention, bore 30 can be larger than bore 18 through a conventional pipe section as illustrated in FIG. 1. This embodiment would permit the passage of tools through pipe joint 28 that are larger than tools that could pass through bore 18 in FIG. 1. Bore 30 can be enlarged during the original manufacture of first pipe section 20 and second pipe section 22, or could be created by drilling through conventional pipe sections. Referring to FIG. 2, fluid passage 32 traverses pipe joint 28 to furnish a fluid communication path between the interior of first pipe section 20 and the interior of second pipe section 22. As illustrated, fluid passage 32 can comprise a groove that is milled or cut into the inner wall of pipe joint 28. Alternatively, fluid passage 32 can comprise a port that is drilled or otherwise formed in pipe joint 28. Although FIG. 2 illustrates one fluid passage 32, a plurality of fluid passages 32 can be utilized to facilitate the flow of the fluid between the interior of first pipe section 20 and second pipe section 22. Fluid passage 32 is adaptable to drill pipe, to drill rod, or to similar tubulars having a constriction such as a pipe joint. For example, the use of fluid passage 32 is equally applicable in pipeline operations requiring the transport of a pig or other tool through the pipeline. In operation, first pipe section 20 is connected to second pipe section 22 to create pipe joint 28. As illustrated, bore 30 of pipe joint 28 has an interior diameter less than the interior diameters of first pipe section 20 and second pipe section 22. First pipe section 20 and second pipe section 22 are placed into the wellbore, fluid (not shown) is placed therein, and a tool such as core barrel 34 is transported therethrough. As core barrel encapsulates a core sample and is withdrawn with wireline 36, core barrel 34 passes through pipe joint 28 as illustrated in FIG. 3. Because the annulus between core barrel 34 has a smaller cross-section than the annulus between core barrel 34 and first pipe section 20 or second pipe section 22, pipe joint 28 impedes the flow of fluid around core barrel 34 as core barrel 34 is transported into or out of the drill string. To minimize this impedance, fluid passage 32 provides an opening to permit the transport of the fluid around pipe joint 28. This flow reduces pressure variations in the fluid due to transport of core barrel 34. Wireline 36 can lower or raise core barrel 34 within the drill string. Alternatively, core barrel 34 can be transported by pumping techniques known in the art, which are particularly useful in horizontal applications. In one embodiment of the invention, as illustrated in FIG. 2, the drill string can comprise four inch pipe sections having an internal diameter of 3.340 inches. Although the standard bore dimension through a pipe joint can be 2,438 inches, pipe joint 28 shown in FIG. 2 has been bored to an internal diameter of 3.0 inches. These dimensions are illustrative only and do not define the scope of the inventive concepts herein. These dimensions illustrate one embodiment of the invention wherein a balance between certain criteria is maintained. Specifically, such embodiment maximizes bore 30 through pipe joint 28 to permit the passage of the largest possible tools, while maintaining sufficient wall thickness in pipe joint 28 to maintain the structural integrity of pipe joint 28. It will be appreciated that the configuration, location, and number of fluid passages 32 can be modified to maintain the structural integrity of pipe joint 28 while maximizing the potential flow of fluid across pipe joint 28. This fluid flow balances the pressure of the fluid acting on opposite ends of core barrel 34 as core barrel 34 is transported through pipe joint 28. Although the present invention has been described in terms of certain preferred embodiments, it will be apparent to those of ordinary skill in the art that various modifications can be made to the inventive concepts without departing from the scope of the invention. The embodiments shown herein are merely illustrative of the inventive concepts and should not be interpreted as limiting the scope of the inventive concepts.