DK201470810A1

DK201470810A1 - Method and connector assembly for connecting tubular members

Info

Publication number: DK201470810A1
Application number: DK201470810A
Authority: DK
Inventors: Daniele Di Crescenzo; Michael Shuster; Dayeeta Roy
Original assignee: Shell Int Research
Priority date: 2012-06-15
Filing date: 2014-12-19
Publication date: 2015-01-19
Also published as: WO2013186400A3; US20150152691A1; WO2013186400A2; AU2013276415A1; CA2874384A1; US9404315B2; CN105874150A; AU2013276415B2; WO2013186400A8; BR112014030665A2

Description

METHOD AMD OObMECTOR ASSEMBLY FOR CONNECTING TUBULAR

MEMBERS

The present, indention relates to a method for connect.!og· Tubular members end to a. connector assembly made-up using said method.

The connector typically includes a pin member and a boa member. The pin member may have a threaded outer surface and the box member may have a correspendLeg threaded inner snrfa.ee allowing the pin - member and box member to be connected, forming a threaded connection. Connectors of this type are generally used in oilfield applications, for instance to cannedt sections of red shore casing or production tubing. Often, connectors for oilfield appii.cati.ons are required to provide lignin tight and/or gas-tight sealing and to have a strength at least approximately equal to the body strength of toe pipe sections joined by the conxreetors.

Recently, expandable tubular technology has become commercially available. Herein, expandable pipes are radially expanded downhole. The outer diameter of the pipes are increased, for instance, in the range of about 10% to 25%. Many cells hare already beexx eased or lined using expandable tubulars. Expandable tubulars - such os expandable casings or liners - are typically also comprised ob pipe sections which are interconnected using threaded connections. Each pipe section typically has a length in the order of 10 metres.

An API (American Petroleum institute} threaded connector is a commonly used type of connector which performs relatively well at relatively low cost. The API connector however may not always provide reliable gas-tight sealing. In view thereof the API threaded connectors are primarily used for liquid service applications, eh lie more expensive connections, so-called premium connectors, are typically used for applications where gas-tight sealing is required, for instance in production casing or production tubing of gas ceils. Most conventional premium connectors have specially designed threads, and rely on metai-to-metaI interference for leak tight sealing.

In. order to improve the gas scalability of API threaded connectors it has been proposed to apply a soft metal plating to the threaded surfaces. Examples of such plating material include sine phosphate, sine and tin, US patent no, 5,212,855 discloses a threaded connector therein the threaded section of each pin member is marked with a band, and therein, the threaded surface of the bos member is plated with tin, A thread lubricant is applied to the threads of the box member, arid the pin and box members ate; screwed, together until the face ox the box member overlaps the band, The connection is considered acceptable if the face of the box member is properly positioned over the band on the pin member, arid if the make-up torque is within predetermined limits. Proper make-up of the connect ox- of 113-5,212,885 may be difficult or impossible· if the coating layer is too thick., and. unallowable deformation of the pin member dr the box member may occur, The make-up torque can become excessive arid poor thread engagement can occur which negatively impacts performance of the connector. This.· connector ig unsuitable to be expanded and will probably leak after expans ion,

To ensure leak tightness after expansion, expandable pipes, typically comprise, premium connectors, Still, the connectors often are the weakest link in the expansion process mainly due to the complicated stress distribution along the thread profile during expansion., Severe plastic defo matron. during the expansion process may totally destroy the· sealing mechanism of the connector, including the metal.-to-metai seal of a premium connectar. Hence the need arises to develop alternative connections which can survive high expansion ratios (up to 30% or even 35% in some eases) and be leak tight (liquid tight and preferably gas tight) after expansion, US-6417147 discloses a combination of a mechanical and metallurgical, connection for joining :manors such as conduits wherein amorphous diffusion bonding material is placed at mating or abutting surface a in the mechanical, joint. The bonding' material is compressed under pressure and heat is applied to cause the bonding material to diffuse into the mechanical connection. IB-6 86Q420 discloses a method of interconnecting a pair of mets.1 oilfield tubulars having complementary tapered edges. The tapered edge of at least one of the tubulars at the common contact surface thereof is provided with a thin layer of a metal having· a melting temperature lower than the melting temperature of the tubular, The tubulars are interconnected, and heat is applied to the thin layer of metal to melt the thin layer ox metal,- followed by cooling the tapered edges wherein a metallurgical bond is created between the tubulars, Subsequently the tubular are radially expanded in the wellbore.

As resources become ever scarcer, recently wells have been drilled in ever more 'challenging environments- For instance, wellbores have been drilled- in deep water and/or in high pressure hydrocarbon, reservoirs. Deep water herein may indicate more than 1 km water depth.

Sigh pressure muy for instance indicate reservoirs at a pressure of more than 100 ear. However, pressures up to 400 bar or acre are not uncommon, in exceptional cases even exceeding 1200 bar. To render matters worse, the hydrocarbons in the reservoirs stay comprise contaminations, typically including corrosive and/or toxic gasses such as H2S or C02« The expanded tubing, including the expanded connections, is expected to contain said gases up to the maximum pressure to which the tubing in a worst case may be exposed.

Based on a: challenging drilling scenario, tor instance in the Gulf of Mexico, it was also established through computer mode 11.1 ng that the connections should preferably be able to survive a drilling torque. Rotating the tubing may be required to introduce the tubing into, the well beyond a threshold depth. For example, a pipe having an outer diameter (DD) of 5.5 inch may be required to withstand a torque of about 'TOGO xt-ihs (about 9,5 kHm) or more. Rotating the pipe may be required to be able to introduce the pipe more than about 5,050 feet into the we!X bor e,

There- is currently no connection available in the market that can survive expansion -and remain leak tight after expanding the outer diameter about 20% or more. However, the challenging· drilling scenarios· presented above have created a heed for -connections· which can be leak-tight, and preferably gas-tight, after expansion.

It is an object of the present invention to provide an improved; method of connecting, tubular members.

In accordance with the- invention there is provided a method of coining tubular members, comprising the steps o f providing a first tubular member having a first end connection part; providing' a second tabular member having a second end connection part configured to rake-up a connection with the first end connection part; placing .an -amount of filler material on. at least a portion oi a mating surface of at least one of the first end connection part and the second end connection part; joining she first and second tabular member by making-up she first end connection and the second end connection while applying a first torque, wherein the filler- material is compressed between the first end connection and the second end connection; heating the joined firer end connection and second end connection to a·· first temperature below the melting temperature of the filler material; applying a second, torque, exceeding the first torque; raising the temperature to a. second, temperature at or above the -melting temperature of the filler material to cause diffusion bonding among the filler material and the first and second end connection; lowering the applied second torque? and cooling the first and second end connections.

The invention relates to a method of interconnecting a pair of metal oilfield tubulars having complementary tapered edges with a common contact surface when the tubulars are interconnected, The tapered edge of at least one of the tubulars at the common contact surface thereof is provided; with a thin layer of a filler material having a melting temperature lower than tie melting temperature of the tabular . The layer of filler material is heated to melt the thin layer:, herein a metallurgical bend is. created between the tubular end connection parts. The method creates a relatively strong bond as well as a reliable metal-ho-metal seal between toe end parts at their common contact surface.

Suitably the filler material may he selected from a material suitable for 1.: arise, soldering, amorphous bonding or diffusion welding so as to form, said metallurgical bond,. The filler material, for instance comprises one or' more of : Fe, hi, Cu, Ag, Hi, brass*, broare, Qe, An, Zw, Cry Si, B.. C, P, 1, Mu, Su, or an as ίο r p.h o u s me Pal,

The filler material may be deposited on the end connection parts in the form of a spray, paint, foil, tape, ring, grease or suspension in a suitable gel,

The heat to melt the filler material can be applied, for enarsple, by 'meana of a flame, inductive heating, chemical reaction, heat convection or an electrical resistance process, In a preferred embodiment, the heat is applied using inductive heating. The filler material may be deposited on the first and/or second connection ends using thermal spraying.

Suitably the angle of intersection of the tapered end connection parts with the longitudinal awes of foe: tubulars is in the range of from 1 to 10% bore preferably from 3 to 6%

In an embodiment, the joined tubular members, including the joined first and second end connections, are radially expanded. Such expansion process can tabe place in a wellbore formed in the earth, formation, for example in order' to create an expanded casing op liner in the wellbore.

According to another aspect, the invention provides a connector assembly, comprising; a first tubular hawing a first end connection part; a second, tubular having a second end connection part make-ηρ to the first end. connection part; and an a mo tint of filler material on at least a portion of a mating surface of at least one of the first end connection part and the second end connection part; the assembly being joined using the method described above.

According so another aspect, the present invention relates to ;a hydrocarbon wellbore provided with a series of tubular members which have been mutually connected using the method of the present invention.

The invention, will be described hereinafter in more detail and by way of example, with reference to the accompanying drawings in which:

Fig, i is hows a longitudinal or os e-ae at: on of an embodiment of first and second end connection parts cl tubular members to be used in the method of the i event i on r Pet ore ma he-up;

Fig, 2 shows a loogitudinil cross-section of the end connection parts of Fig, 1 after make-up;

Fig. B shows a perspective view of another embodiment of an end connection part to be used in the method of the invention; rig. & shows a perspective view of the end connection part of Fig. 3 after application of filler material;

Fig. o shows a cross-section of assembled end connection: parts;

Fig. 6 .shows a cress-sectxqn. of an embediment of a method, for non-destructive quality control;,?

Fig. 1 shows examples of test results of the method: of fig.. 6;

Fig. S shows an exemplary graph indicating the application of torque and heat during make-up of the end connection parts according to tire method of the invention; and

Fig. 3 shone another exemplary graph indicating she application of torque and heat during make-up of the- end eon.neofc.ion parts according to the method of the invent i on,

Figures: 1 and 2 show an embodiment of a first, tubular member 1 provided with a first end connection part 2,. The first end connection part is a male connection part having first tapered edge 3.· A second tubular member 4 comprises second end connection, pert provided with a second tapered edge 6 which is complementary to the first tapered edge 3, The tapered edges form a pin and box type stab-~in connector wherein the first tapered edge 3 is the pin tiember of the connector and the second tapered edge 6 is the bor member of. trie connector. The tubular members-1, h are aligned and have a common longitudinal axis 7.

The tapered edges 3, 6 have a common contact surface 8 (Fig. 2} when the end connection parts 2, 5 are interconnected. In Fig. I the individual surfaces of the first and second tapered edges 3,, 5 which form the common contact surface 3 are indicated by respective reference signs 8a,· 8b. The contact surfaces 8a, 8b may be provided with complementary threads, comprising ribs ID and grooves 12,

The pin member 2 may have an end portion in the form of lip 18, The box member 5 may have an end portion in the form of lip 18. The box member 5 may have a shoulder 20. The pin member 2 may have a shoulder 22, insen made-op, the lip 18 of the pin .member preferably engages the shoulder 20 of the box member and/or the lip j.8 of the bom member.:engages the shoulder 22 of the pin smamber. A relatively tain layer of a filler material (not shown} having a melting temperature lower than the melting temperature of the tubular members 1, 4 is deposited on at least a part of the tapered surface 3 and/or 6 prior to make-up of the pin member 2 and the boa member 5. Bald filler material may for instance be deposited in one or more of the grooves 12 -

In a preferred e.mbcdimenc, the melting temperature of the filler .material loner than the transition temperature.. The transition temperature may be about 723 degree C, The base material, i.e. the material of the: pipe, is preferably steel,

The layer of filler material may include a Copper based alloy or a Michel based alloys, Alt emotively,· the filler material may comprise another alloy or an amorphous metal. If the filler material is a bracing composition it may also contain a fins material, for instance a herat.e. The flux material may be embedded in the braving' composition, or be distributed over the surface of the bracing composition before bracing is commenced,

The thin layer of filler material may be deposited on the contact surface 8a and/or 3b in the form of a spray, paint, tape, ring, grease or suspension in a suitable gel.

After the layer of tiller material has- been applied to one or both the contact surfaces 3a, 3b, or into the grooves 12, the .pin. member 2 is introduced in the bom. member .2 and screwed together wherein the ribs Id fit into the corresponding grooves 12, as shown in Fig, 2. when the connection, is made up, heat is applied, to the pin and box members. 2., 5 to melt, the filler material.

As shown in. Fig, 3, in an alternative embodiment the tapered surfaces 3, 6 of the pin member 2 and the box member h respectively (Fig, 5) may be smooth, Smooth herein for instance implies that the respective surface is non-threaded, The end section It is indicated, as well as shoulder 22,

Figure 4 shows the pin member 2 wherein filler material 24 is applied to the tapered surface 3, The filler material may be applied to only a section of the tapered surface. In the embodiment of Fig. 4,- the entire surface 3 has been provided with filler material. The filler material has for instance been applied by spray coating or -thermal spraying. The thickness of the filler material is .about 0,1--0,2 mm on one or both of the pin member and the box member, in .a preferred embodiment, the filler material is deposited on both the pin member and the box member.

Although not shown, the box member 5 may have a similar smooth tapered surface 6. Said tapered surface 6 may similarly be provided with a layer of filler material, I.e., one or both of the tapered surfaces 3, a may be provided with, a layer of filler material.

Fig. 5 -shows the angle a between the cross-section: of the tapered surfaces 3,- 3 oh one hand and the common longitudinal axis 7. The: angle a is preferably in the range of 2 to Id degrees:. When the tapered surfaces are smooth, ah angle ά in the order of about 3 degrees has proven to provide optimal bonding and strength, heating Is preferably effected by means of a flame, inductive heating, chemical reaction, heat convection or an electrical resistance process.

For application on a drill site near a hydrocarbon wellbore, induction heating is preferred, herein, an inductive coil may be arranged around the connection of Fig, 2,

During induction heating,· an electrical current through said coil may create Eddy currents in the connection, dissipating heat. Although store neat is generated closer to the outer surface of the connection,· the entire ail her material will be heated due to the neat conduction of the metal of the tubular members 1, 4, To minimise fire and explosion hasards, for instance inert gas stay be provided at the inner surface of she connection during heating,

As a result of this heating process the tengierature of the layer of filler material is for instance raised to a temper«lure at or above the melting temperature of the material. The temperature is for· instance within the range of about tub to 1100 °C, preferably in the range of about 600 to 700 degree C. Id a preferred embodiment, the connection is heated to a temperature about -20 degree e above the melting temperature of the filler material.

While- heat is applied and she temperature is raised, a pressure may be applied between the pipe ends to be bonded, this situation being advantageously maintained during a period of time, for instance at least 10: seconds,

Erasing as a joining process can be defined as a process which joins materials- (of the same or dissimilar composition}' through the use of heat and a filler material. The filler material is for instance a metal or menal alloy with a ..melting temperature above about 452 degree C but below the molting temperature pf the bate materials being joined, A successfully braced joint can result in a metallurgical, bond that is. as strong as. or stronger than the base metals being joined. As mentioned before, the base metal is typically steel.,

The filler material is arranged in a gap between two parts to be: joined. Said parts are heated up to the melting temperature of the filler material, which melts and flows into the gap, forming an alloy of the materials at the transition point, typically on solidification»

This creates a metallurgical bond. The molten metal typically flows into and fills voids within the gap between the two parts by capillary action.

Like erasing, soldering does not involve the melting of the base me ta 1s, Η o wev e r, filler me t a i f or s oId e r1no has a lower melting point (less than 450 degree C) *

Though this may be an advantage of the soldering process, soldered joints lack a metallurgical bond and are therefore incapable or handling high stresses because the soldered joint is relatively weak.

Welding forms a metallargical bond in a way similar to brasing» However, the filler metals used have higher melting temperatures which are typically in the same order as, or only just below: the melting temperature of the base metals. Due to the relatively high, temperatures, it is possible that there is some distortion in the base metals. Though welding can create a strong joint, it can also change the mechanical and metallurgical properties of the case metals dab to the high teemneratores,

The main advantages of bracing with respect to: spidering or welding are: i) Relatively low melt, i.ng point of flirer maser.in Is; 11} Joins dissimilar materials; ill) Maintains .metallurgical properties of base metals;

It) Compatible with conventional quality control tech n i qt.es; c) Provides reproducible restits;

However, adapting bracing tor the oil industry has its own. challenges, Some of them are; a) Making bracing suitable for big as sooth, i os like tubular connections for oilfield tubular strings; b) Cleanliness effects the quality of the joint, rendering bracing a difficult technology to Implement on oilfield rigs where the surroundings may not sufficiently c .1 e an; c) Quality control checks after bracing and before putting pipe downhole may be a challenge,

Bragina or amorphous bonding of oilfield tubulars has the following potential advantages; - it is applicable to a wide range of material a including carbon steel, stainless steel and titanium; - no protrusions occur after bonding or bracing, hence flash connections are formed; ~ it can be carried out automatically, hence no skilled operators are required; " the required heat inputs are lower than for welding, improving safety and making it easier to limit risks; - it is relatively rapid; - the Pabulars are automatically axially aligned; - a. large bonding surface and thus a strong bond is created; and -- it is a cost-effective process.

For these reasons bracing or amorphous bonding of tapered edges of adjoining oilfield tubulars can be of significant benefit lor joining carbon steel and corrosion-resistant alloy well casings, tubings and liners .

In order to achieve a good quality brazed joint, the process of bracing: is very important. This process includes the preparation of the end. connection, parts to be brazed till the cleaning or the end product,

Good fit and. correct clearance between the faces to be 'joined is an important parameter in brazing. The capillary action which is the main principle involved worts most effectively when the gap between, the components it optimal. For oilfield connectors, typically this gap can range from. 10 microns to 100 microns. The optimum gap is specific for a particular base metal in a given set of conditions, The tensile strength of the erased, joint varies with the amount of clearance between the parts before brazing thereof.

According to tesos, the strongest joints are achieved when the clearance between the two parts is less than. 0,15 mm. The tensile strength may be more than 80,000 to 100.000 psi (abort 550 to 700 HPa). If the -gap is wider, the capillary action is reduced, so the filler metal may fail to fill the joint completely thus lowering the joint strength, the ideal clearance between the two parts before brazing is in. the order of 0,001 to 0,004 inch (about 30-80 pm;. Tensile strength may be in the order of 120.000 psi (about B25 bPa) or more,

Gapj.ilary action worts best when the surfaces of the base metals are clean. Contaminated surfaces, for instance contaminated with dust, grease, rust or oil, hinder the flow of molten metal and result in a wearer joint. Oil prevents proper distribution of molten metal through the joint. Filler materials do not bond well to rusty surfaces. Cleaning surfaces may be done with water or organic coiceats, Alternatively, mechanical removal may include abrasive cleaning. Particularly in repair erasing# where parts may be very dirty or heavily runted, yon can speed the cleaning process by using emery cloth# a grinding wheel or grit blast, followed by a rinsing operation. Once the parts are clean, flux and bracing material are preferably applied as soon as possible. This prevents recontamination of the surfaces# for instance by dust, grease or oil which may be deposited daring handling, flux is a chemical compound applied to the joint surfaces. The primary purpose of flux is to promote wetting of the base metal by the brazing filler materia!. Heating a metal surface accelerates the formation of oxides, the result of chemical combihation between the hot metal and oxygen in the air. It is preferred, to prevent the formation of oxides, as oxides may inhibit the brazing filler metal from wetting and bonding to the surfaces, .¾ coating of flux on the joint area will shield the surfaces from the air, preventing: oxide formation.

The flux will also dissolve and absorb any oxides that form during heating or that were hot completely removed in the cleaning process. Fluxes are Usually tailor made for a certain filler material. Chemical fluxes may comprise one or more of* Borates, elemental Boron, fluohorates, fluorides, chlorides;, wetting agents, or water,

It is important to align the eng connection parts in the right position to get the correct, geometry of the final joint. This ensures correct distribution of the brazing filler throughout the joint by capillary action. Usually gravity can be used to hold, the two tapered surfaces together. Other methods might involve a mechanical tool to hold the pieces together ίο the right position.

The above shows chat adapting the brazing technology for the oil and gas industry can be quite a challenge.

The present invention enables the development of this technology for use in oilfield applications.

The main challenges faced in brazing a threaded connection are; a. Application of bracing alloy on the connection threads; b. Presence of threads highly influence the distribution of the orating material; c. Rotation (making up of the threaded connection) simultaneously with the application of beat (induction) also influences the spread of brazing1 material over the connection area; d. Establishing the process parameters to ensure repeatable: performance ,

Out of the various bracing· materials that exist in the industry today, the most optimum materials mere chosen. This was done by small scale testing·. This· saved time and costs,, as a. lot of materials and application methods could be tested in a limited amount of time. The most suitable materials were then applied on full.-«bale connections1 of oilfield pipes.

Out of the whole range of brazing alloys,,· silver"' copper based alloys provided the highest yield strength and/or shear strength. Shear strength may he above 2DO to 210 Mpa C.3S hsi). Yield strength may exceed I8b itPa.,

The table below discloses two exemplary embodiments· of. brazing materials providing erased connections having yield and shear strengths, .in the highest range, .1. e . above 180" HP a and 200 HPa respectively.

A number of possible processes for the application of brazing material are available, The brazing material can be in the ferm of paste, foil, coatings, dippings etc.

One of the most convenient and reliable sags to apply filler material, is thermal spraying, A preferred, method, of pre-bracing comprises thermal, spraying of molten filler material. Thermal spraying herein preferably includes plasma-spraying. This method provided the best resorts, eliminating voids and incomplete filler formation, thus drastically decreasing a number of bratihg defects during manufacture.

Appl..1 cati.ou of a pre-hraze coating using plasma spraying of the brazing material B:Ag~2i may for instance be deposited using a manually operated plasma gau, optionally· arsing argon as a shielding atmosphere. Serial production of steel tubing provided with the pre-braze coating may be performed by a robotic· plasma spraying system..

Preferably surfaces are prepared before plasma spraying, for instance using sand blasting. Preparing surfaces mill improve the adhesion of thermally sprayed materia,! to the steel substrate and/or· remove oxides and contaminants on the surface,. Pin and box members of steel tubing may for instance be subjected to blasting with fine alumina sand in a glove: chamber.

Preferably, the combined, layers of the filler material to be sprayed on the pin and· box of the connection together provide a filler material volume which is about equal to up to about 50% greater than the gap volume between the pin and box members of a fully made-up connection. This ensures that enough bracing material la present in the connection during brazing to bully cover the connection and have a proper joint.

Excess filler material will be pushe;! out oi the connection by pressure generated during the mechanical action of rotating the connection. In a preferred embodiment, the combined filler material volume is about 50% greater than the gap volume.

Disadvantages of depositing insufficient amounts of filler material in the connection may include; * lasakihq connection; * Lower strength of the joint.

Disadvantages of depositing excess material in the connection may include; * Impossibility of making up the: connection due to high required torque; * .Damage (permanent plastic delormation} of the connection ends (pin. and/or box.); * Solid protrusion of filler material on the inside or outside of the connection after bracing; * Increased cost per connection.

According to the present .invention, deposition of she filler material to the pin and/or bqx may include one or more of the following steps; 1) Dopes it 1 on of the 0.: using mat er i a 1 on the oonnection: aurfaoes to maximise efficiency and consistency of the process before brazing. In this case it can he any method of deposition, such as dipping, plating,, brushing, painting. Spraying is preferred, due to the easy application# the predictable process# and the repeatafcie thickness; 2) Sintering of she filler material after spraying to increase the bonding to the base metal and the strength, of the eventual bracing by decreasing porosity and increasing cohesion (i.e. bonding between particles of. brazing material).

The application of the filler material can be done in & workshop or factory, which will improve the quality and decrease the time of the eventual, bracing at the rig.

The tests proved that the deposition of the filler material on the connections be fore? the real 'htrasiag" strengthens the eventual braced connection. This may be referred to: as "prebrazing", Herein the bonding between the braring material and the steel is already established before the final brazing of the brazingmaterial at the we 13. bore,

Prebrasing is a technique wherein the filler material is deposited on the bin and/or the box (to create a diffusion bond between the base metal anil the brazing alloy). Subsequentl.y the two prebrazed. surfaces are joined by brazing. This process reduces the final brazing time drastically# making it better suitable for application at. a rig. The prebraaing process also ensures proper banding of the brazed layer to the. substrate.,.

The pre-brazing step can be performed in a clean and controllable environment such as a work shot? or .factory. Once the coating of filler material has been applied, to one or both of the pin member· and the box member in the workshop# s.a.id pia and box can be connected at tee rig site within a limited time, Ά protective cover may be applied to the pre-brazed pin. member and/or box: member to keep the parts clean.

For instance,· she cadmium-free brazing materials BAg-18, BAg-24 (composition provided above} and BAg~21 provided increased strength of the braced connection.

Deposition of Che filler materia.! by dipping directly into a bath of molten filler material may encounter one or more of the following technological problems; 1} The steel tubing' should be heated to a temperature: above the melting temperature of the pre-brazing material. Otherwise the pre-bras lag material may solidify on the tubing in the fora:, of a non-uniform layer, which also may be too thick; 2) Erasing fluxes may have limited working time, and therefore the flax cannot be placed above the molten pre-brazing material in the same bath. Consequently, the steel tubing must be heated for contacting and reacting with the flux, then, heated, again (or held at the higher' temperature) in order to dip the tubing into the bath of molten braze. Such mode of operation is difficult even with small size tubing and it is almost impossible with thick steel tubing, having a diameter of 6 inch or nære; and 3} The filler material may only have to be deposited, on one surface of the pin (outside surface 3} and/or one surface of the box [inside surface 6), Koweyer, the direct dipping method results in coatings of both the inside and gutside surfaces of pin and/or box, thus consuming double the volume of relatively expensive' brazing material. Herein, please note that often the brazing material comprises silver.

In an embodiment, it is possible to disconnect the connection after beating or brazing if required.. Disconnecting includes : a) The assembled connection is heated to a temperature at or above the melting temperature of the filler material (the filler material melts); b) Rotating the first end connection part and tbs? second end connection part with respect to each ether while the assembly is at or above the melting temperature to disconnection the first end connection part from the second end connection part*

The pre-applied coating mag have a thictness in the range of 0*l~0*2 mm* Good adhesion of plasma-sprayed pre-brase coatings to steel surfaces was confirmed. Thermal spraying of the fillet material improves the control over the amnunt and distribution of the filler material.

The surfaces were prepared for plasma spraying by sand blasting, to improve the adhesion of plasma"Sprayed brazing material to the steel, substrate.. Steel tubing and standard specimens mere subjected to blasting eitfe fine alumina sand In a glove chamber.

According to the invention, the pin and bos members of the connect ions can be tested after application of the pre-bracing layer, or after brazing. Herein, each pin and box member can be tested, or a certain percentage thereof can bo tested, depending on ior instance specifications., strength of final connections, etc. For instance, at first all pre-braoed parts may be tested, and once satisfactory connections have been achieved, only a set percentage of connectors may be tested*

The quality of the braced joints is qf .critical importance in ensuring the proper performance of the bond * Non-destructive test methods, part icaiar iy ultrasonic techniques nave been a prime area for research in determining the quality of such bonds. Ultrasonic techniques, in comparison with other non-destructive· methods, offer the highest sensitivity for evaluating metallurgica.i bonds because acoustic properties of materials and interfaces are closely related to their elastic properties,. A procedure was adopted to control and check the quality of the braced connection. Herein, the beared connections; are subjected to ultrasound scanning. Fig. 6 shows a testing apparatus 50 for testing the braced connection. The testing apparatus, comprises a container 52 filled with a fluid 54, such as water, ha acoustic transducer 50 is mounted on a frame 58 arid is moveable a,iong: the length of a sample, such as the tubular· members .1, 4 including: the braced connection of surfaces 3, 6,

The fluid has a height LI, which at least exceeds the length of the connection, The total height of the apparatus may be L2,

During testing, the transducer 56 sends out acoustic signals towards the pipes 1, 4. Reflections of said signals are recorded by the transducer 5=--, and supplied to a data processor (not shown), Fig, ? shows reflections 60 from front wall 61, interface 62 and back wail. S3, Example 7a shows good bonding,· including only reflections from the front wall Si and aft wall 63, Example IB shows reflections from the front wail 61, interface 62 and aft wall 63, indicating mediocre quality of bonding. Example 7C shows reflections from the front wall 61 and, the' interface 62 indicating a lack of bonding.

The quality- of bracing is highly dependent on various parameters, Besides the preparation, of the parts .of the connection, the brazing process itself is important.,

Care ful control over tesoper at ure and time is mandatory to get optimal results. Brazing the threaded connection® is even more complicated because of the presence of a third parameter, i.e. torque. This is because the connection is braced while if is being· made up. According to the present invention, a con junction between torque, time and temperafare is provided rendering the process and the quality of .trie braced connection reproducible,

Additionally, tbe process of the invention may include one or more of tbe following steps: - Application of different thicknesses of bracing material along the length of the (threaded} connection. This may improve the distribution of the bracing material, may compensate for tolerances· and concentrate necessary material at the beginning and end of the thread. Id apply a thicker layer at certain areas, one uses extra time (e.g. in the order of 2 to ID seconds, for instance about 5 seconds) for spraying brazing material in said areas; ~ Application of a reservoir for additional bracing material in a contact surface of the connection to improve the distribution of the brazed material along the length and perimeter of the threaded Connection; -- Spme elements of the destructive and. nondestructive1 quality control for· the erased threaded connection,

Through extensive experimentation: and analysis, she process envelopes shown in Figures S and S have been developed. In the graphs of rigs. 2-9, the vertical axis on the right side represents torque t (make up), and the vertical axis on the left side: represents temperature: I, The horizontal axis represents time fe. The dotted line represents the torque applied to the connection, while tb fe stripe-dot line indicates the applied temperature. Both the application of torque and temperature· are associated with a tisse factor.

The process producing connections 'having optimal strength and reliability generally comprises the steps of (reference to Tigs. B, 2) : i) At t(h apply torque to make up the pin member 2 and the box member S until the end 16 of the pin engages the shoulder 20 of the cox and/or until the end 18 of the cox engages; the shoulder 22 of the pin. Engagement will be indicated by a sudden increase in or levelling of the torque at Λ. Application of torque indicates that the pin and box are rotated with respect to each other. This may be done for both threaded and rue? threaded connections, in an embodiment, the pin and boat are not completely connected, maintaining a small gap between· the' t«o: parts. The small gap is for instance about 8 sat or about 2 turne; ii) At tl,- increase the temperature up to about 75-S2%, for instance 35%, of the me It. log' temperature of the filler material; iii) Maintain the temperature at the level of ii) for a time period t.2 to t3, to equalize the heat distribution in the connection (E to F). In an embodiment, the time (tl to t.3} which is at least required to equal ire the temperature in step E~F (Figs·, 8, 9) can be calculated, vita the formula; t - S . 4'10Λ (~ 5 ) -h * I { (0Λ2~dA2 )v r} /41 vihereio: t is time in seconds; h is the height of the connection in asg: D. is the OD of the pipe (in mm); and d is the 10 of the pipe (in mm), ID indicates the inner diameter. The formula above was confirmed using a v&H FJL connection on 5,5" OD 9 -, .5mm WT pipe; iv) At ; J, increase the temperature no about the melting temperature of the filler material, up to about 20 degree 7, or 10%* higher (F to G5; v) Apply Increased torque to mate up the connection. The increased torque is preferably applied when the temperature is about 90-95% of the melting temperature of the bracing material. As shown in Figs. 8-9, the increased torque may exceed the level of torque applied at i), for example be more than three or four times higher·, Again, application of torque indicates that the pin and box are rotated with respect to each otter, This may be done for both threaded and non-threaded connections: (C to D) , The optional small gap between the two parts, which may have been left at step 1), is closed; ei) At to, cease to apply torque; vii) After a predetermined time (G to R), cease applying heat to enable the connection fee cool. Cooling is preferably done naturally, by cooling to air (line 70), Cooling to air provides· the strongest brared connection. Alternatives for faster cooling include cooling by adding cooling liquid such as water. Cooling liquid can be applied in modest amounts (line 72) or vast amounts· (11¾¾ 9%)< The latter will cool the connection fastest, but will also produce a more brittle connection; and vi.ii) Optionally, when the temperature of the assembled connector is at or below a predetermined cooling temperature ϊ (at to in Fig, 8) the connector may he cooled rapidly to below 50 degree C by supplying liquid,· such as mater, The eooirng temperafure is for instance about 350 degree C.

The combination ei Torque» Temperature, and Time parameters enables the reproduction of identical successful braced connections.

The casing and tubing strings which, hare been joined according to the present invention provide a leak-free, seamless, lifetime cora.pletio.ri and potentially enable slimmer, more cost-elfactive sells to be pursued.

After the metallurgical bond is created between tbe pin member 2 and bon member 5,. the casings 1» 1 may be radially expanded using a suitable expansion cone or other expansion device. Spring the expansion process» the lip IS of the pin member 3 and the lip 18 of the box member bare a tendency to bend radially inwards- due to the fact that the radially inner portions of the pin and box members1 are subjected to a larger circumferential strain than their respective radially outer portions, such radially inward bending of the lip 16 of the pin member 2» and the consequent {partial} loss of the sealing capacity of the connector, is adequately prevented by the metallurgical bond created between the pin and box members.

Deposition a coating of the filler material in a factory accelerated the assembly of braced connections on a rig site . In practice, the connect ions can he made-up and braced in about 6 minutes or less, for instance in about i minutes (time tQ-t.S in Figures 8, 8}. The cool down in air fro?;· the braxing temperature (for instance about 7.00 degree C, or G--B in rigs, 8, s) to the cooling temperature (for instance about 350 degree C, or 1 in Fig. 3) may babe about 15 to. .20 minutes (15 bo to In Fig. 8) ,

Tims., the deposition of a coating (pre-braeing) allows depositing material outside the critical path of the connection make-up, which will make the make-up of the braced. connection faster compared to alternative-Craning methods (such as bracing paste or foil) that would require this operation the be performed on the rig f loom la an embodiment,- one layer of pre-braning material was deposited on the pin member and one layer of pre-bracing material was deposited on the bos member. Said pre-brasing coatings were comprised of the same bracing material. Both pre-bracing coatings may comprise different materials though.

Threaded connections, braced in less than 5 minuses, were able to seal more than oQQ bars {7250 psi) of liquid and gas pressure after being expanded about 22% in fix-fix condition (this is the worst case scenario simulation the differential sticking in real field). Similar tests were also performed· on fatigued connections (one million cycles) . These connections could, also be expanded 22% and remained lead tight.

To react es:~ connections were also braced and expanded. The brazing: materials which survived 500 bars liquid tightness included for instance el-eotr olytioally applied pure Copper and Silver ,

The method of the invention enables more reliable make-up of connectors, while at the same time fluid-tight or even gas-tight sealing of the connector can be achieved,, even after expansion. The method, of the invention is at present the only method available wherein eon.nee-ti.om; can be expanded, remain leak-tight after expansion, :and .survive a drilling torque of about. 70QD ft-lbs (about 9,5 kbm) or more. Herein, the connections can be radially expanded about 20% or more. The connections: rex·®in leak-tight after expansion, Gas-tight herein indicates that the connection cam for instance contain 500 bars of gas pressure or more after expansion.

Premium connections suitable .for the present invention include for instance VAPSh-PJL and uvd.::i 1 ':m mb These are inside and outside· flush integral connections providing maximum. clearance with optimum strength for liners, casing, and tigbC-noie tubing strings. The method of the present invention enables to upgrade she connections: to satisfy the functional requirements of chalienging weI i s,

The bracing process is optimized, including for instance the conjunction of temperature, torque and time. Fixing the process parameters enables to reliably deliver .identical connections and identical performances ,

The method of the invention enables the use of "threadless"' connections. This obviates the need for expansive premium threaded connechions, thus limiting costs. Using threadless connections may cut costs by more than 5Q% with respect to pipes provided with premium connections·.

The invention is not limited to the above-described embodiments1 thereof, wherein· various modifications· are conceivable1 within the scope of the appended claims'·. Features of respective embodiments may for instance be combined,