Abstract:
An improved reemployable tubular connection system and method for oil field application disposes an axially asymmetric seal in a coupling sleeve interconnecting the oppositely entered pin ends of two tubing sections. The sleeve includes an approximately central interior surface for seating a deformable seal having oppositely directed tapered edges with different angles of convergence. The pin ends enter into and resiliently displace the edges of the seal, which may be made differentially adhesive so that a tubing connection may be broken and remade a number of times.

Description:
REFERENCE TO PRIOR APPLICATION 
     This application relies for priority on the previously filed provisional application of the same title filed by Kenneth J. Carstensen on Sep. 4, 2008, Ser. No. 61/190,145. 
     FIELD OF THE INVENTION 
     This invention relates to improvements in oil field pipe assemblies having threaded and coupled end areas for use in demanding conditions, and more particularly to coupling configurations which employ internally plastic coated or fiberglass lined tubings and casings. 
     BACKGROUND OF THE INVENTION 
     In the development of improved methodologies to meet the ever-increasing demands for the production of petroleum hydrocarbons, improved tubing systems have been developed for use at great drilling depths, in directionally drilled wells, and in ever increasing very corrosive high pressure and temperature operational environments. There are constant needs to meet such increasingly demanding reliability requirements under ever more stringent field conditions. 
     Two broadly different present categories of such improved systems are generally recognized, namely, those which, on the one hand, meet standards set by the American Petroleum Institute (API) and those which, on the other hand, meet specialized, usually more exacting standards, usually commercialized as “premium” products. The latter group is necessarily more costly, and seldom economically viable for general usage, so although the concepts presented here may find application in premium products, this invention is primarily directed to tubular goods that meet particularized API standards. 
     API standard products must meet known tolerances and design characteristics, so they are consequently interchangeable, less costly, and available in quantity. They are therefore preferred for use wherever field conditions permit. In order to gain the longest working life and best economic case, some API tubing and casing, when used in corrosive environments, are internally plastic coated (IPC) and others insert fiberglass liners (FGL). As technology has developed to extract oil from fields which are less accessible, more stressful conditions have had to be met and overcome, including operating at increasingly greater drilling depths and under even less favorable production conditions. 
     Different problems are presented by W/AG (water/alternating gas) systems for recovery of additional hydrocarbons by the injection of water and CO 2  gas into fields in which production has dwindled to near nothing or which have otherwise ceased to produce. This has led to increasing adoption of the internally coated and fiberglass lined tubing systems, to provide tubing strings which not only can withstand high pressures and temperatures, but which can also resist corrosion and chemical attack. Placing such products in use, in turn, has revealed a number of other problems and weaknesses. For example, applying a protective coating adapted for its chemical resistance to attack often also led to threaded end area non-uniformities. Such coatings have to be applied by spraying, which more or less inevitably has tended to introduce disparities between coating thickness at the crest and root areas of the threads. Moreover, the stresses within a threaded joint vary with the local physical strength of segments of the joint, since the relatively thinner cross-sections of pin ends are likely to deflect more than the thicker opposing sections of the associated coupling sleeve during makeup and joint tightening. Minute but significant surface imperfections can then appear in the coatings and these imperfections can be attacked by pressurized corrosive gases. Moreover, continued or repeated makeup of a coupling may introduce hairline cracking which can affect not only the integrity of a coating or lining, but also the physical strength of a threaded joint. In consequence, even though the lined or coated tubing and coupling combinations are intended for repeated engagement and disengagement, these and other problems have militated against satisfactory performance under repeated use. 
     Workers in the art therefore have sought to introduce special techniques for improving sealing performance. Perhaps the most commonly used is a product called “Coupling Guard”™ a product of Tuboscope Inc. which is formulated of an epoxy, PTFE, and “Ryton”™, a liquid mix which is applied to an interior central length of the central region of a coupling and is subsequently thermally treated to accelerate solidification and curing. The liquid properties of the mix and the inherent shrinkage following the heating and curing process can introduce irregularities between the thickness of the thread crest coatings in comparison to the thickness at the thread roots. Consequently, there can be a proclivity toward thread damage under makeup conditions, and thread damage and deformation because of differentials in pin end radial compression. If stresses exceed the capability of a material beyond what it can resist, the deformation will introduce cracking of the plastic coating. Damage and loss of corrosion protection also occur from successive makeup and breakout of the connections. 
     Another connection for internally plastic coated pipe is sold by Hunting Energy Services, of Houston, Tex. as the “KC-MMS Connection”™ and uses an interior ring seal centrally set into an interior circumference of a coupling. The ring seal includes an index tongue on the coupling internal diameter and a matching outer groove on the outer surface of the seal. Tapered side wings on the ring engage the pin end faces inserted into the coupling. Central sealing requires both precision marking and subsequent makeup steps, often difficult to achieve under practical field circumstances. For example, the “KC-MMS Connection” must be aligned relative to “timing” or “makeup marks” on the connection, which alignment is time consuming and difficult to achieve in the field and if not performed properly can result in widely varying final makeup torque. Moreover, the “MMS” type of sealing connection can encounter problems during assembly, from hydraulic deformation and displacement of the thread lube as the pin is being driven into the coupling. Also, the thread lube can be forced into the space between the wing of the resilient seal and the coupling and impelled by hydraulic forces out of its groove. 
     These and other problems are exacerbated during production when high pressure injection tubing has to be withdrawn from the downhole installation and run back in, as for regular maintenance or replacement or repair. This is commonly known in the industry as “tripping the pipe”. It is preferred to be able to do this at least 8-10 times, although practical experience has shown that this is seldom feasible. This is true because such conditions as thread deformation, pin end compressive deformation and coupling bell-out exist and impede establishing the torque level in the connection that is needed for adequate strength. 
     Consequently, some existing very expensive premium internally plastic coated and fiberglass lined pipe connections have been designed to confront the problem of providing adequate pressure containment and corrosion resistance. However, economic and operative advantages can be realized if baseline, economical, API threaded and coupled connection products can be widely used under the previously stated more stringent conditions and still furnish all the operative reliability and repeatability that is required. 
     SUMMARY OF THE INVENTION 
     An internally lined or coated connection for use with production and high pressure injection tubing, such as (for example) 2⅞″ or 3½″ diameter tubing incorporates a homogeneous central seal such as a non-fiber reinforced Teflon body engaging both pin ends within a coupling. The seal is in the form of a ring with asymmetry between the shapes and lengths of its two lengthwise ends. The seal body lies slightly longitudinally offset, within a generally central but precisely offset seating span of constant diameter of the coupling, adjacent the female threaded ends of the coupling. When the two compatibly shaped male threaded pin ends of tubing are threaded into the opposite ends of the coupling the pin ends each engage into the adjacent and different specifically shaped axially converging edges or end sections of the central “Teflon” ring. The seal end section on the mill or plant makeup side includes a shorter, relatively steeper taper radius than the other seal end section, on the field makeup side, which has a longer shallower taper. The tapers are angled to converge toward the adjacent end in a predetermined proportion, and the ratio can be dependent on the specific API coupling that is being used. The pin ends can be shaped to have bullet nose configurations, but in any event the initial threads engage into and deform the interior sides or angled surfaces of the end sections of the seal ring, which they separately engage. To insure proper displacement of the pin end stabbing chamfer, the first 1½ to 2½ starting thread areas tap into the resilient Teflon seal material, thus establishing the initial compression of the resilient material necessary to effect a high pressure seal mechanism. The threads are processed to have finished polished surfaces which receive an interior coating for engagement with the opposed segment of seal surface. 
     As in typical assembly operations, the coupling including the interior seal is bucked on at the plant, here with the pin end being made up at the short radius side with inserted mill end tubing. A retainer tool may be inserted from the opposite side to hold the seal in position as the tubing is driven in. The threads of the pin end penetrate into and deform the “Teflon” seal material such that volumetric displacement occurs in a predeterminable range. This tolerable deformation permits shape recovery that is adequate to assure restoration of contact pressure on multiple makeups, when such are called for. In the field, when the full coupling is made up, the pin end of the field tubing engages into the seal at the tapered end section which is at a flatter angle. Again, the volumetric displacement of the seal material is limited to a predetermined amount. This combined with the innate resiliency of “Teflon” assures that the integrity of the seal will be retained on repeated breakouts of the coupling. In engagements after successive breakouts, the inserted tubing end penetrates to a cumulative depth that increases with successive engagements, but the added increments diminish with repetition. The configuration also provides improved sealing and corrosion barrier protection for API connections on internally plastic coated (IPC) pipe and fiberglass lined pipe. 
     Seals in accordance with the invention are also advantageously useful with fiberglass lined (FGL) pipe connections. In this exemplification, however, the connection includes a “bonding slurry” layer interposed between the facing circumferences of the liner and pipe, and also between the pipe end face and the central seal. On full makeup, the field side pin end displaces the seal on that side, forcing it into the pin end threads and establishing the desired asymmetry. In the FGL version the central ridge section of the seal preferably is volumetrically displaced sufficiently such that its inner diameter is substantially flush with the inner diameter of the lined tubing. 
     Methods for employing this configuration are simple, readily accomplished and practical. Prior to assembly of the mill pin end of the tubing to the coupling, a circumferential demarcation line of precision width is applied to each end of the tubing to establish dimensional thread engagement positions for plant makeup and for first field makeup. A light coat of a fast curing sealant is applied to the mill pin end threads and to the internal threads at the plant makeup side of the coupling. The coupling can then be bucked-on to a dimensional position in which the previously implanted line is lined up with the outside shoulder of the coupling. The sealant increases sealing capability of the threads and also increases breakout torque so that only the field side of each connection will disengage when the tripping operation is properly carried out. The tubing end inserted in the field initially is also inserted to the demarcation line depth, but subsequent makeups are to greater depths and are defined by torque limits. 
     Seals in accordance with the present invention have separate utility in connections that do not employ either internally coated tubing or fiberglass lined tubing, because of the continuity in flow they impart to the system. By incorporating the presently disclosed seals in the connections, the resistance to high pressure differentials across the joints is increased and sealing is improved. At the same time, the seal is more resistant to internal turbulence in the tubing, and thereby improves operative characteristics of the tubing string. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A better understanding of the invention may be had by reference to the following description, taken in conjunction with the accompanying drawings, in which: 
         FIG. 1  is a perspective view, partially broken away, of an IPC connection in accordance with the invention; 
         FIG. 2  is a cross-sectional side view of the connection of  FIG. 1 ; 
         FIG. 3  is an enlarged fragmentary view in section, showing further details of the construction of  FIGS. 1 and 2 ; 
         FIG. 4  is a side view, partially in section, of an FGL connection in accordance with the invention; 
         FIGS. 5 and 6  are fragmentary views of successive phases of formation of the FGL connection of  FIG. 4 ; 
         FIG. 7  is a block diagram representation of method steps used in assembling a connection in accordance with the invention, and 
         FIG. 8  is a side sectional view of a retainer tool as used in mill end assembly of a coupling configured in accordance with the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     As seen in  FIGS. 1-3 , a pipe connection  10  is shown that is in conformity with API standards and can meet the demanding corrosive high temperature conditions that often exist at substantial depths and otherwise. A distinction is made in the industry between API couplings, which are made in accordance with predetermined industry standards set by the America Petroleum Institute, and “premium” couplings, which typically are more precise, intended for specific purposes and consequently substantially more expensive and not interchangeable with API connections. Illustrated herein are typical and widely used examples of tubing connections, as in API 2⅞″ 8 rnd and 3½″ 8 rnd. The connection  10  includes a sleeve coupling  12  with internal threaded sections at each end in accordance with the chosen thread, whether round or buttress. The product depicted in  FIGS. 1-3  provides an example of an IPC type-connection  10  evolved over time in the course of industry efforts to meet corrosion and durability problems, but specifically improved, as described hereinafter, by employing seal elements, coatings, and lubricants in both novel and conventional ways. In this example, the coupling sleeve  12  includes a approximately central section  14  of constant interior diameter, between and merging into the female thread sections  15 ,  16  on each side. The constant I.D. span  14  is longitudinally offset from the true longitudinal center of the coupling  12 , here by a fraction of an inch, for this example. The pin ends  18 ,  19  of two separate and opposite tubing elements  20 ,  21  are threaded into the associated female threads of the coupling sleeve  12 , with the exterior male threads  23 ,  24  of the pins engaging into the female threads  15 ,  16  respectively of the sleeve  12 . The first and second pin ends  18  and  19  respectively are of API standard configuration. The first pin end  18  will be referred to as being on the field makeup side, so the second pin end  19  is on the mill makeup side. In conventional fashion for such applications, the pin ends  18  and  19  have been prepared by machining the flat pin ends to a rounder, “bullet nose” configuration, which is more amenable than flat pin end shapes to coating and concomitant processing steps. Moreover, the pin ends  18  and  19 , including the threaded sections, are typically blasted with “Garnett” abrasive to form an anchor pattern on the steel surfaces of the pin ends and provide maximum mechanical adhesion of the coating. 
     In the connection  10 , the generally central flat ID section  14  of the sleeve  12  receives and retains a polymeric seal  25  in the form of a ring occupying a generally central but slightly longitudinal offset position with its outer diameter engaged against the span  14  between the threaded sections  15 ,  16 . This generally central seal  25  has asymmetric tapered edge sections  27 ,  29  extending axially and each converging to a terminal edge from a flat (i.e. constant diameter) central section  26 . The flat (constant radius) span or section  14  in the mid-region of the inner diameter of the sleeve  12  is referred to as “generally central” to denote that it is slightly offset, in this example by ⅛″ from the true longitudinal center of the sleeve  12 . The particular asymmetry of the seal  25  is configured to accept differential penetrations of the male threaded ends  23 ,  24  of tubing separately inserted from opposite directions, as described hereafter. Note that the female threads  15 ,  16  in the sleeve  12  commence at the extremity of the slightly offset flat section  14  and continue axially to each proximate end of the sleeve  12 . Each tapered edge section  27 ,  29  of the seal  25  is thus within, engaged and locally deformed by a different pin end  18 ,  19  of a tubing element  20 ,  21 . The seal  25  itself is of uncoated, non-impregnated and non-reinforced “Teflon”. The tapered edge section  27  on the mill end side converges at a first predetermined taper angle from an essentially uniform inner diameter section  26  of the seal  25 , and is relatively steeper than the converging taper tapered edge section  29  on the field end side. For a 2⅞″ tubing, the tapered section  27  on the mill side is an angle of approximately 10-12° to the centerline, while on the field side the taper angle on the tapered edge section  29  is about 18-19° to the centerline. In this example, there is thus a differential of ⅛″ between the axial lengths of the tapered edge  27  of the mill end side (which is shorter) and the tapered edge  29  on the field end side. The differential in length is of significant benefit in practice, because of the fact that the mill end side essentially is held static while a succession of breakout and makeups are effected on the field end side, as described further hereafter. 
     Installation and Functioning of the Systems of FIGS.  1 - 3   
     In reviewing the following description of installation and use of an IPC [[FGL]] version of a system, reference can also be made to the method steps depicted in  FIG. 7 . After the installation of the seal ring  25  in proper orientation within the flat surface  14  of the coupling sleeve  12 , one pin end  21  is bucked-on in the mill to a selected linear position on the sleeve  12 . The position is first measured in known fashion by placing a conventional cup gage (not shown) over the end of the pin  21  to dimensionally define a specific location relative to the threads of the pin end. Using the cup gage, a visible (white) line 0.125″ wide is applied to each end of the tubing elements with a steel paint marker pin. These visible lines  31 ,  32  are depicted separately in outline by dotted lines on the Figures and the marks establish the plant makeup position  31  and the first field makeup position  32  for thread engagement at each end of the tubular product. The reference marks  31 ,  32  are rapidly installed (requiring little or no additional labor) and only 4-6 seconds per end for an experienced installer. Thereafter, a light coat of “LubeLock Sealant” is applied to the plant makeup pin end threads  24  and also to the internal threads  16  of the plant makeup side of the coupling  12 . In bucking on the pin end  21  on the mill side, the forces involved are substantial as the threads of the pin end penetrate into the tapered edge  27  of the seal ring  25 . To retain the seal ring  25  in precise position, a retainer tool  35  ( FIG. 8 ) having a concentric tapered end  36  mating within the field end taper  29  on the seal  25  is entered into position within the coupling  12  to retain the seal  25  and to eliminate axial or rotational displacement during powered insertion of the pin end  21 . 
     In the plant or pipe yard, the coupling  12  is then bucked-on to the dimensional position in which the white line  31  that has previously been applied is lined up with the outside shoulder edge of the coupling  12 . The “LubeLock Sealant” is of the water activated type, and when cured performs two functions. First, it ensures additional sealing capability and second it provides further adherence of the joined parts, adding an additional 50% increase in breakout torque (relative to a petroleum based thread lubricant). This helps in ensuring that on breakout of a connection at the operating site, the upper-most, or field side of each connection will disengage when the pipe is tripped out of the wellbore. 
     The material of the seal  25  used in this example is polytetrafluoroethylene (“Teflon”), and here the material is employed without any additional reinforcements or fillers (i.e. as virgin “Teflon”). With the exterior uniform diameter of the seal  25  in engagement against the flat slightly off center ID span  14  of the coupling  12 , and with the retainer tool  35  in position, the seal  25  is secured firmly, so when the first pin  21  is bucked-on during makeup at the mill, the first pin end  19  threadedly engages into and resiliently deforms the shorter tapered edge section  27  of the seal  25 . This engagement occurs without linear or rotational displacement of the seal  25  as the threads penetrate and displace the “Teflon” seal  25 . The angle of the relatively shorter tapered edge  27 , and the thickness of its cross-section as the pin end  19  moves in axially, determine the axial length of thread penetration and also the preload initial contact pressure between the seal  25  and the pin end  19 . It also determines the displacement volume induced in the “Teflon” as the pin threads are tapped into it, which must be accomplished without crushing the “Teflon” seal material. The “Teflon” seal  25  geometry relative to the displacement volume induced by the intruding pin threads is designed to ensure a range of 15-18% of displacement. This insures proper initial compression of the seal material, aids in assuring shape recovery on breakout of the connection and provides adequate initial contact sealing pressure for future multiple makeup and breakout sequences. 
     The partially finished connections, comprising multiple separate tubing sections, each paired with a seal and coupling that is precisely and properly attached at the pin mill end, can then be transported to the rig site, directly or after storage in inventory. For the first makeup of connections at the rig site, each pipe is picked up and the second or field pin end is stabbed into the coupling sleeve  12 , so that a power tong (not shown) can make up the connection until the previously inscribed 0.125″ white line or first field makeup position  32 , that was applied at the plant, is in proper position with respect to the coupling sleeve  12 . This is when the bottom edge of the line is lined up even with the outside shoulder edge of the attached coupling sleeve  12 . In conventional fashion, field end makeups are accomplished using an API modified type thread lubricant. The use of curing or hardening sealants on the field pin ends is not generally required. 
     When the coupling has been made up to proper dimensional relationships as described above, the connection  10  can later be broken out and made up a number of times, employing the resilient and repeatable deformability of the interior seal  25 . For well maintenance or repair, additional makeups and tripping of the pipe require only that the thread lubricant be renewed and that the joints be made up to optimum API torque specifications. 
     An alternative seal construction in accordance with the invention for use with fiberglass lined pipes is shown in  FIGS. 4-6 , to which reference is now made.  FIG. 4  shows, for introductory purposes, two opposed fiberglass lined tubing sections relative to an intermediate coupling sleeve and central seal in partially assembled form, although in practice the field installation of a pin end is not completed until the mill end tubing is secure. The successive stages leading to complete engagement are illustrated in  FIGS. 5 and 6 . 
     The connection of  FIGS. 4-6  provides sealing and corrosion barrier protection for API connections using fiberglass lined (FGL) pipe. As in conventional practice, sections of fiberglass liner  40 ,  41  are incorporated internally in each of the adjacent pipe sections  43 ,  44  to be substantially longitudinally coextensive therewith. At the ends of the fiberglass liners  40 ,  41 , transverse fiberglass reinforced rings  46 ,  47  are interposed between the pin ends of the pipe  43 ,  44  and a central seal  50  which is seated in a uniform approximately central diameter section  52  of the coupling  51 . The liner inserts  40 ,  41  are sealed and secured to the pipe sections  43 ,  44  by intervening layers of bonding slurry  53 ,  54  respectively. The central seal  50  has a central inwardly directed ridge  56 , and axially extending tapered edges  57 ,  58  in the field end and mill end sides respectively. 
     As shown in  FIG. 4 , the pin end of the mill pipe  44  on the mill end engages into a length of the shorter side tapered edge  58  of the central seal  50 , leaving a small gap which can be filled with “Lube Lock” or other sealant to help insure that breakout during later disengagement occurs at the field end side. The longer shallower taper edge section  57 , is shown in  FIG. 4  as initially seated in the central uniform diameter section of the coupling  51  to await full engagement of the pipe end  43  at the field site. Here, the central ridge  56  on the seal  50  is not yet volumetrically displaced. However, in the field, as the field makeup torque is applied ( FIGS. 5 and 6 ), the field end pin  43  moves into and begins to displace the seal material in the shallower taper end section  57 . Consequently, the radial thickness of the seal ridge  56  is displaced inwardly somewhat by the field side pin end  43  as it penetrates into the coupling  51  and the seal  50  ( FIG. 5 ). When the full engagement position is reached for the field end tubing  43 , the ridge  56  inner diameter is substantially flush ( FIG. 6 ) with the inner diameter of the fiberglass liners  40 ,  41 . 
     In this position, the leading edge threads of the field pin end  43  have engaged into and deformed the shallower tapered field edge section  57  of the central seal  50 . At consummation of the field end engagement action therefore, ( FIG. 6 ), the inner surface of the pin end  43  on the field side is thus aligned longitudinally with the inner surfaces of the fiberglass ring ends  46 ,  47  and the inner diameters of the liners  40 ,  41 , while the ridge  56  inner surface is also aligned, so that all interior surfaces are substantially flush and at the same radius from the center line. 
     Displacement of the material in the seal  50  is limited to the level at which the shape can be recovered after deformation, so that repeated connections of the field end into the coupling  51  can be made. The seal  50  is not permanently deformed or rendered inelastic, thus preserving resilience through a number of repetitive connections. In addition, the full benefits of the fiberglass liner  41  and the associated end rings  46 ,  47  are retained and their sealing effects are augmented by the action of the seal  50 . 
     Methods in Accordance with the Invention 
     Referring now to  FIG. 7  the pin ends  18 ,  19  of the tubing elements  20 ,  21  are typically converted to a “bullet nose” configuration by machining the flat end area at the pin end of the pipe to eliminate 90° sharp angles and to create a smooth radius, particularly where it is desired to apply an even thickness of coating. In the event that a plastic coating is to be incorporated in the pipe, the ID of the pipe is cleaned to white metal by blasting full length with “Garnett”-type abrasive. This establishes an anchor pattern to improve the coating bond. Each pin end is also blasted around the bullet nose, across the stabbing bevel, up to the first 1½ turns of thread, and then the coating is applied, and either air cured or baked in an oven. 
     Separately from pin end preparation the asymmetric center seal  25  is inserted into the prepared interior constant diameter seating section of the coupling sleeve  12 , with its tapered edges properly oriented in the mill end and field end directions. As another preliminary step, the position markers ( 31 ,  32  of  FIGS. 1-3 ) have already been precisely placed (as by using a cup gage) on the pin ends (see  FIG. 7 ) to demarcate desired final position in the sleeve. Sealant can be added to the mill end pipe to assure differential break out so that subsequent couplings can be made up while assuring integrity. At the mill, therefore, one pin end can be precisely engaged into the sleeve, to the marker indicated depth. 
     Usually, an inventory of tubing lengths properly attached to coupling sleeves will be stored in a pipe yard and delivered when requested to a drill site. There, lift equipment is used to stab the field end of a pipe length to be added to an existing string into the upper open end of the coupling sleeve accessible at the top of the string. Power tongs are used to engage the field end of this next section into the sleeve to the marker indicated depth and the coupling is complete. 
     Implementation of the connections using interior seals in accordance with the invention is of particular importance to improving multiple use capability of coated tubing. This is because the coating process involves both liquid application and heat treatment. The liquid application step causes inevitable flow of some material from thread crests to thread roots, such that the disparity can sometimes vary from a thread crest coating thickness of 0.002″ to 0.004″, relative to thread roots having coatings of up to 0.025-0.040″ thick under the same application. It is often not feasible to avoid damaging coatings of this characteristic because of the stresses induced by makeup and breakout. Consequently, although internally plastic coated pipe is often used, these limitations and problems which usually arise from cracking damage in the plastic coating, are often encountered. 
     Employing connections incorporating seals in accordance with the present invention, however, markedly diminishes such problems with relatively little penalty in cost and complexity. Connections in accordance with the present invention make full use of the available deformability, resiliency and recovery characteristics of modern materials by virtue of the advantageous design features which militate against internal deformation of seals during makeup and provide a high degree of tolerance for deformation under stress, as well as acceptance of repeated deformation of the seal. The disclosed sealing configuration for tubular goods has inherent economic and operative advantages even without use of precision placement and makeup techniques as discussed above. When the pin ends are engaged into the spaced apart tapered sections of the seal, the resilient deformation of the seal aids in minimizing leakage through the joint, and the effects of internal turbulence. 
     Although there have been described above and illustrated in the drawings various examples and alternatives in accordance with the invention, it will be appreciated that other variants will suggest themselves to those skilled in the art. Consequently the invention should be recognized as encompassing all expedients and variations within the scope of the appended claims.