GB2119831A

GB2119831A - Downhole safety systems for use while servicing wells

Info

Publication number: GB2119831A
Application number: GB08304518A
Authority: GB
Inventors: Jack Willis Tamplen
Original assignee: Otis Engineering Corp
Current assignee: Otis Engineering Corp
Priority date: 1982-05-07
Filing date: 1983-02-18
Publication date: 1983-11-23
Also published as: CA1200193A; NO830607L; GB8304518D0; NO160596B; NO160596C; GB2119831B

Abstract

A safety valve which prevents undesired fluid flow while conducting hydraulic workover or snubbing operations on a well includes three separate valve portions for blocking fluid flow including a poppet valve 85 which can be opened and closed from the well surface in response to control fluid in line 33. Elastomeric sealing elements 70a to 70d (only one shown) form a fluid barrier with the exterior of the work string 40. The work string 40 itself opens and closes a flapper valve 90. The poppet valve 85 allows fluid flow to bypass the elastomeric sealing elements 70a to 70d. <IMAGE>

Description

SPECIFICATION Downhole safety system for use while servicing wells This invention relates to downhole well tools and methods for preventing undesired release of well fluids while servicing wells.

United States Patent No. 3 21 5 203 discloses equipment and methods for inserting and removing a flow conductor from a well. United States Patent No. 3 21 6 731 discloses well tools and methods for preventing a blowout while moving a flow conductor into and out of a well.

Both of these patents disclose equipment and methods which are used for hydraulic workover of oil and gas wells. This equipment is sometimes referred to as "snubbing" equipment because a flow conductor (i.e. a work string or wash string of pipe) is inserted into the well against formation fluid pressure rather than overcoming the formation pressure with drilling mud or workover fluids.

An object of the present invention is to provide a safety valve which can control the flow of well fluids through a production tubing string.

Another object of the present invention is to provide a downhole safety valve which allows a work string to be inserted through the safety valve while the safety valve continues to control well fluid flow.

A further object of the present invention is to provide a downwhole safety valve which can be releasably secured within a production tubing string, which safety valve may include elastomeric sealing means to engage the exterior of a work string which can be inserted through the safety valve.

A still further object of the invention is to provide a safety valve or downhole blowout preventer which can control fluid flow in the annulus created by inserting a work string into the bore of a production tubing string.

Another object of the present invention is to provide a safety valve or downhole blowout preventer which will block fluid flow through a production tubing string after a work string has been withdrawn from the tubing string.

An additional object of the present invention is to provide a downhole blowout preventer to prevent the undesired escape of well fluids while moving a work string through the bore of a production tubing string.

A further object of the present invention is to provide a downhole safety valve which has a valve closure means that can be mechanically opened by inserting a work string through the safety valve and will automatically close when the work string is withdrawn from the safety valve.

A further object of the present invention is to provide a method for preventing undesired fluid flow while servicing or working over a well which has not been killed by drilling mud or workover fluids.

A still further object of the present invention is to provide a safety valve which can form a fluid barrier with the exterior of a work string but will still allow fluid flow in the annulus between the work string and production tubing string.

With this object in view, the present invention provides a safety valve for controlling fluid flow through a first flow conductor, comprising housing means with a longitudinal flow passageway extending therethrough; a valve closure means having a first position allowing fluid flow through the first flow conductor and a second position blocking fluid flow through the first flow conductor; means for shifting the valve closure means between its first position and its second position in response to control fluid pressure from the well surface; and sealing means for forming a fluid barrier with the exterior of a second flow conductor when the second flow conductor is disposed within the longitudinal flow passageway.

The invention will be described further, by way of example, with reference to the accompanying drawings, in which: Fig. 1 A is a drawing, partly in vertical section and partly in elevation with portions broken away, showing a typical well with the lower portion of a hydraulic snubbing apparatus (hydraulic workover unit) mounted on the wellhead; Fig. 1 B is a continuation of the well shown in Fig. 1A, including a schematic representation of the downhole safety system to prevent undesired fluid flow while working over the well; Figs. 2A to 2D are drawings, partly in elevation and partly in section, showing a safety valve incorporating the present invention, in its second position blocking fluid flow through the production tubing string (first flow conductor);; Figs. 3A to 3D are drawings, partly in section and partly in elevation, showing the safety valve of Figs. 2A to 2D in its first position with a work string (second flow conductor) inserted therethrough and poppet valve means thereof open to allow fluid flow through the annulus between the work string and the production tubing string; Figs. 4A to 4D are drawings, partly in section and partly in elevation, which show the safety valve of Figs. 2A to 2D returned to its first position after the work string has been partially withdrawn from the longitudinal flow passageway which extends through the safety valve; Fig. 5 is a cross-sectional view taken along the line 5-5 of Fig. 3D and shows pressure regulating means which limits the maximum difference in pressure acting upon each sealing element; and Fig. 6 is a cross-sectional view taken along the line 6-6 of Fig. 3B and shows the poppet valve means in its open position.

Referring to Figs. 1A and 1 B, hydraulic snubbing apparatus 20 is shown mounted on wellhead 21. The well is partially defined by casing string 22 which extends from the well surface to a subterranean hydrocarbon producing formation (not shown). The wellhead 21 is attached to and supported by the casing string 22.

Production tubing string or first flow conductor 23 is disposed within the bore of the casing string 22. A well packer 24 is installed at a down hole location to form a fluid barrier between the exterior of the tubing string 23 and the interior of the casing string 22. The packer 24 directs fluid communication between the hydrocarbon producing formation and the welihead 21 via bore 38 of the tubing string 23. The packer 24 preferably positioned to isolate most of the interior of the casing string 22 from the corrosive effects of formation fluids. This system of completing a well allows for reduced maintenance and increased well life. Only the production tubing string 23 should have to be cleaned and/or replaced. The casing string 22 should last indefinitely if not subjected to corrosive fluids.

The wellhead 21 includes a master valve 25 which controls flow into and out of the tubing string 23. These sets of blowout preventers 26, 27, and 28 are mounted onto the wellhead 21 above the master valve 25 during hydraulic workover of the well. The blowout preventers 26, 27 and 28 are of a conventional type. They are operated by fluid pressure and have a vertical bore aligned with the bore 38 of the tubing string 23. The preventers 26, 27 and 28 are used to retain pressure within the tubing string 23 while a work string or wash pipe 40, being a second flow conductor is moved longitudinally therethrough.

The hydraulic snubbing apparatus 20 includes necessary stationary slip assemblies 29 and 30 and travelling slip assembly 31 to move the work string or wash pipe 40 longitudinally into or out of the bore 38 of the tubing string 23. A detailed description of hydraulic snubbing apparatus 20 and associated methods for servicing a well are contained in United States Patent No. 3 215 203.

This description of the invention is made with reference to using the snubbing apparatus 20 to move the work string 40 through a safety valve 45. A similar safety valve, incorporating the present invention, could be installed within the casing string 22 and the production tubing string 23 moved longitudinally therethrough by the snubbing apparatus 20. Also, a coiled tubing unit or reeled tubing injector (not shown) could be used to insert a second flow conductor into the bore 38 of the tubing string 23.

A control manifold 32 at the well surface contains necessary accumulators, pumps, and valves to supply hydraulic control fluid to the safety valve 45 via a control line 33. The safety valve 45 contains three separate means for preventing undesired flow of well fluids. Each of these means will be described in detail. They cooperate to allow the safety valve 45 to function as a downhole blowout preventer while moving the second flow conductor 40 through the bore 38 of the first flow conductor 23.

Referring now to Figs. 2A to 2D, the safety valve 45 is shown in its second position, blocking fluid flow through the tubing string 23. The safety valve 45 includes housing means 46 with a longitudinal flow passageway 47 extending therethrough. For ease of manufacture and assembly, the housing means 46 consists of several relatively long, hollow cylindrical subassemblies.

These are attached to each other by threaded connections and are concentrically aligned to define the longitudinal flow passageway 47. A housing subassembly 46a is a conventional locking mandrel used for releasably anchoring the safety valve 45 at a downhole location within the tubing string 23. A landing nipple 34 is made up as a part of the tubing string or first flow conductor 23. Grooves 35 are formed on the interior of the landing nipple 34 to receive dogs 48 of the locking mandrel or housing subassembly 46a. Two sets of packing means 49 are carried on the exterior of the locking mandrel 46a to form a fluid barrier between the exterior of the locking mandrel 46a and the interior of the landing nipple 34. The packing means 49 restrict fluid flow through the safety valve 45 to the longitudinal flow passageway 47.The two sets of packing means 49 are spaced longitudinally from each other to provide a fluid seal on opposite sides of a port 36 which extends through the landing nipple 34. This port 36 allows control fluid to communicate between the control line 33 and the interior of the landing nipple 34. The packing means 49 isolate control fluid from formation fluids.

United States Patent No. 3 208 531 fully discloses a locking mandrel and landing nipple satisfactory for use with the present invention. If desired, the present invention could be incorporated into a safety valve which is permanently attached to and made up as part of the tubing string 23. However, such an arrangement might unduly restrict production fluid flow. Therefore, the safety valve 45 is preferably installed by conventional wireline techniques just prior to servicing the well and is removed after completion of the services.

An operating sleeve 50 is slidably disposed within the longitudinal flow passageway 47. For ease of assembly, the operating sleeve 50 comprises two hollow cylindrical subassemblies 50a and 50b which are joined together by threads 51. The operating sleeve subassembly 50a is disposed within and concentrically aligned with housing means subassembly 46c. This subassembly 46c functions as a piston housing.

Adapter subassembly 46b connects the piston housing 46c to the locking mandrel 46a.

A stationary seal 52 is carried on the inside diameter of the adapter subassembly 46b to form a fluid barrier with the adjacent outside diameter portion of the operating sleeve 50. A movable piston seal 53 is carried on the outside diameter of the operating sleeve 50 and contacts the adjacent inside diameter portion of the piston housing 46c. The seals 52 and 53 are spaced longitudinally from each other and partially define a variable volume control fluid chamber 54. The difference in diameter between the stationary seal 52 and the movable piston seal 53 defines the effective area for piston 55 on the exterior of the operating sleeve 50. Ports 56 extend laterally through the wall of the piston housing 46c to allow control fluid communications with the variable volume chamber 54.

A biasing means or spring 57 is disposed within the chamber 54 surrounding the exterior of the operating sleeve 50. This biasing means 57 is positioned between a shoulder 58 carried on the exterior of the operating sleeve 50 and a shoulder 59 carried on the interior of the piston housing 46c. Increase of the pressure of control fluid within the chamber 54 to a value greater than fluid pressure within the longitudinal flow passageway 47 serves to create a force on the piston 55 which tends to slide the operating sleeve 50 longitudinally in one direction. The biasing means or spring 57 resists this movement. When the difference in fluid pressure between the chamber 54 and the passageway 47 decreases below a preselected value, the spring 57 will return the operating sleeve 50 to its initial position.

The operating sleeve 50 is used to open and close poppet valve means 85 of the safety valve 45 in response to control fluid pressure within the chamber 54. The poppet valve means 85 includes the operating sleeve subassembly 50b and the housing means subassembly 46d. A plurality of radial openings 60 extend through the operating sleeve subassembly 50b intermediate the ends thereof. A plurality of longitudinal slots or radial openings 61 are machined through the exterior of the housing subassembly 46d. When the radial openings 60 are positioned adjacent to the longitudinal slots 61, fluids can communicate between the passageway 47 and the exterior of the housing means 46 as shown in Figs. 3B and 6.

A first annular valve seat 65 is formed on the exterior of the operating sleeve 50 adjacent to the radial openings 60. A second annular valve seat 66 is formed on the interior of the housing means 46 adjacent to the radial openings 61 and facing the first annular valve seat 65. The annular valve seats 65 and 66 are sized to engage each other and function as a poppet type valve.

Stationary elastomeric seals 67 and 68 are carried on the interior of the housing means 46 to form a fluid barrier with the exterior portion of the operating sleeve 50 adjacent thereto. The seals 67 and 68 have equal diameters to prevent differences in fluid pressure from acting upon the operating sleeve 50. These seals 67 and 68 are spaced longitudinally from each other on opposite sides of the radial openings 60 and 61. Therefore, when the first annular seat 65 contacts the second annular seat 66, this contact, in cooperation with the seals 67 and 68, blocks fluid communication through the radial openings 60 and 61.

A plurality of sealing elements 70a to 70d are disposed within the longitudinal flow passageway 47 surrounded by the housing means subassembly 46d. These sealing elements 70a to 70d comprise sealing means for forming a fluid barrier with the exterior of the work string 40 when it is disposed within the longitudinal flow passageway 47. The sealing elements 70a to 70d are moulded from suitable elastomeric material and are secured to respective flanges 71. Each flange 71 projects radially inward from its respective retaining cylinder 72. The retaining cylinders 72 are slidably disposed within the housing means subassembly 46d between shoulders 73 and 74. The number of sealing elements can be varied to correspond with the well fluid pressure.

Each retaining cylinder 72 carries an o-ring 75 on its outside diameter to prevent undesired fluid flow between the exterior of the cylinder 72 and the inside diameter of the housing means subassembly 46d. Plural pressure regulating valves 76 and also carried by each retaining cylinder 72.

The regulating valves 76 are spring-load ball check valves which open to allow fluid flow therethrough when the difference in pressure across each regulating valve 76 exceeds a preselected value. Various relief valves are commercially available and could be used in place of the ball check valves shown in the drawings. Contact between the second flow conductor 40 and the sealing elements 70a to 70dforms a plurality of longitudinally spaced fluid chambers 80, 81 and 82, as shown in Figs. 3C and 3D. If the difference in fluid pressure between the adjoining chambers 80, 81, and 82 exceeds a preselected value as compared with each other or the longitudinal flow passageway 47, the pressure regulating valves 76 will open to reduce the pressure difference to within the preselected value.Thus, the pressure rating for the sealing elements 70a to 70d is not exceeded, and their effectiveness is significantly increased. United States Patent No. 3 215 203 discloses a similar system of sealing elements and regulating valves for forming a fluid barrier with a flow conductor.

Flapper valve means 90 is threadedly attached to the extreme end of the housing means 46 opposite from the locking mandrel 46a. This flapper valve means 90 includes a cylindrical housing means subassembly 46e with the longitudinal flow passageway 47 extending therethrough. A circular valve disc 91 is secured by hinge 92 to the housing means subassembly 46e within the passageway 47. A third annular valve seat 93 is formed on the inside diameter of the subassembly 46e facing the valve disc 91. A resilient means or spring 94 biases the disc 91 to contact the third annular valve seat 93. Fluid flow in an upward direction within the passageway 47 also encourages the disc 91 to contact the seat 93.

The extreme end 42 of the work string 40 can contact the disc 91 to swing it out of the way, to open the longitudinal flow passageway 47.

Preferably, any difference in fluid pressure across the disc 91 should be equalized, prior to contact with the work string 40, to prevent damage to the hinge 92. Fluid pressures can be equalised by pumping down the tubing string 23 from the well surface or by opening the poppet valve means 85 to allow fluid flow through the radial openings 60 and 61. The poppet valve means 85 allows fluid flow to bypass the elastomeric seating elements 70a to 70d.

Operating sequence: A typical service performed by the hydraulic snubbing apparatus 20 is to insert the work string 40 into the bore 38 of the tubing string 23 against well pressure to remove or wash out a sand bridge which may be restricting formation fluid flow through the bore 38. A sand bridge can be removed by pumping high pressure clean fluids from the well surface down through bore 41 of the work string 40 to lift the sand or other particulate matter to the well surface through the annulus between the exterior of the work string 40 and the interior of the production tubing string 23.

The surface blowout preventers 26, 27 and 28 are designed to shut off undesired fluid flow from either the tubing string 23 or the work string 40 during emergency conditions. The safety valve 45 functions as a downhole blowout preventer, if the surface blowout preventers 26,27, and 28 should fail to operate properly. During normal operating conditions, the safety valve 45 must allow fluid communication through both the bore 41 of the work string 40 and the annulus between the work string 40 and the tubing string 23. The radial openings 60 and 61 of the poppet valve means 85 provide the latter fluid communication path.

The safety valve 45 is preferably anchored within the landing nipple 34 by conventional wireline techniques prior to attaching the snubbing apparatus 20. A removable prong (not shown) can be used to hold the disc 91 away from the third annular valve seat 93 to equalize fluid pressures during installation of the safety valve 45. After the prong has been removed and with no control fluid pressure present in the chamber 54, the safety valve 45 will be in its second position, blocking fluid flow through the tubing string 23. After installing the snubbing unit 20, control fluid pressure can be applied from the well surface to the chamber 54 to open the poppet valve means 85. Fluid communication through the radial openings 60 and 61 will then equalize fluid pressure across the disc 91.

The work string 40 can be inserted through the tubing string 23 and the longitudinal flow passageway 47 by conventional snubbing techniques. The end 42 of the work string 40 will contact the disc 91 to swing it away from the valve seat 93. The elastomeric sealing elements 70a to 70d form a fluid barrier with the exterior of the work string 40 when it is disposed within the longitudinal flow passageway 47. When necessary, fluids can bypass the sealing elements 70a to 70d by opening the poppet valve means 85.

During an emergency condition, control fluid pressure within the chamber 54 can be decreased below a preselected value to allow the spring 57 to close the poppet valve means 85. The elastomeric sealing elements 70a to 70d cooperate with the poppet valve means 85 to block fluid flow through the annulus between the work string 40 and the tubing string 23. By raising the work string 40 with the snubbing unit 20 until the end 42 is above the disc 91, the flapper valve means 90 will also be closed. The spring 94 and the well fluid pressure cooperate to urge the valve disc 91 to contact the third annular valve seat 93.

Thus, decreasing the control fluid pressure and raising the work string 23 will shift the safety valve 45 from its first position allowing fluid flow therethrough to its second position, blocking fluid flow through the tubing string 23. In this manner, the safety valve 45 provides a secondary barrier or additional backup for the surface blowout preventers 26, 27, and 28.

The foregoing description is illustrative of oniy one embodiment of the present invention. Those skilled in the art will readily understand that other variations and modifications may be adapted without departing from the scope of the invention as defined by the following claims.

Claims

1. A safety valve for controlling fluid flow through a first flow conductor, comprising: a. housing means with a longitudinal flow passageway extending therethrough; b. a valve closure means having a first position allowing fluid flow through the first flow conductor and a second position blocking fluid flow through the first flow conductor; c. means for shifting the valve closure means between its first position and its second position in response to control fluid pressure from the well surface; and d. sealing means for forming a fluid barrier with the exterior of a second flow conductor when the second flow conductor is disposed within the longitudinal flow passageway.

2. A safety valve as claimed in claim 1, wherein the housing means can be releasably anchored within the first flow conductor at a preselected downhole location.

3. A safety valve as claimed in claim 1 or 2, wherein the anchoring means comprises: a. a locking mandrel attached to and forming a part of the housing means for anchoring the housing means within the first flow conductor; b. dogs, carried by the locking mandrel, to engage grooves formed on the interior of a landing nipple which is part of the first flow conductor; and c. packing means for forming a fluid barrier between the exterior of the locking mandrel and the interior of the landing nipple.

4. A safety valve as claimed in claim 1,2 or 3 wherein the valve closure means comprises: a. a poppet valve means which can be opened and closed in response to control fluid pressure from the well surface; and b. a flapper valve means which can be opened by extending the second flow conductor through the longitudinal passageway.

5. A safety valve as claimed in claim 4, further comprising: a. an operating sleeve slidably disposed within the longitudinal flow passageway; b. a piston, on the exterior of the operating sleeve, comprising a portion of the means for shifting the valve closure means; c. a plurality of radial openings extending through the operating sleeve and the housing means; d. a first annular valve seat formed on the exterior of the operating sleeve adjacent to its radial openings; e. a second annular valve seat formed on the interior of the housing means adjacent to its radial openings and sized to engage the first annular valve seat; f. the first and second annular valve seats comprising a portion of the poppet valve means; and g. engagement of the first and second annular valve seats blocking fluid flow through the radial openings.

6. A safety valve as claimed in claim 5, wherein the sealing means comprises: a. a plurality of sealing elements disposed within the longitudinal passageway between the poppet valve means and the flapper valve means and spaced longitudinally from each other; b. the sealing elements being engageable with the exterior of the second flow conductor when the second flow conductor is disposed within the longitudinal passageway and forming a fluid barrier therewith when the second flow conductor is both moving and stationary with respect to the housing means; c. a plurality of longitudinally spaced chambers formed by the engagement between the sealing elements and the exterior of the second flow conductor; and d. pressure regulating means for limiting the pressure differential between each chamber to below a preselected value.

7. A safety valve as claimed in claim 6, wherein the flapper valve means comprises: a. a third annular valve seat formed within the longitudinal passageway near the end of the housing means opposite from the locking mandrel; b. a valve disc hinged within the longitudinal passageway adjacent to the third annular valve seat; c. means for biasing the disc to engage the third annular valve seat to block fluid flow; and d. the hinge allowing the disc to swing away from the third annular valve seat when contacted by extending the second flow conductor through the longitudinal passageway.

8. A safety valve as claimed in claim 7, wherein the first position of the valve closure means consists of: a. the first and second annular valve seats being spaced longitudinally away from each other to allow fluid flow from the exterior of the housing means through the radial openings into the longitudinal passageway; and b. the second flow conductor extending through the longitudinal passageway to open the flapper valve means.

9. A safety valve as claimed in claim 8, comprising means for biasing the operating sleeve to slide longitudinally to engage the first and second annular valve seats.

10. A well tool which can be positioned at a preselected downhole location within a first flow conductor to prevent the undesired escape of well fluids when a second flow conductor is disposed within the first flow conductor, comprising: a. housing means with a longitudinal flow passageway extending therethrough; b. a valve closure means having a first position allowing fluid flow through the first flow conductor and a second position blocking fluid flow through the first flow conductor; c. means for shifting the valve closure means between its first position and its second position in response to control fluid pressure from the well surface; and d. sealing means for forming a fluid barrier with the exterior of a second flow conductor when the second f!ow conductor is disposed within the longitudinal flow passageway.

11. A well tool as claimed in claim 10, further comprising: a. means for releasably anchoring the well tool within the first flow conductor; b. the valve closure means comprising a poppet valve means for controlling fluid communications with the longitudinal passageway via radial openings through the exterior of the housing means intermediate the ends thereof and a flapper valve means within the longitudinal passageway for blocking fluid flow therethrough; c. a hydraulic piston and operating sleeve for opening and closing the poppet valve means; d. a plurality of sealing elements disposed within the longitudinal passageway between the poppet valve means and the flapper valve means and spaced longitudinally from each other; e. the sealing elements being engageable with the exterior of the second flow conductor; and f. the flapper valve means being hinged to allow the second flow conductor to be moved longitudinally through the well tool.

12. A well tool as claimed in claim 11, wherein hydraulic control fluid can be directed from the well surface to the piston to open the poppet valve means.

1 3. A well tool as claimed in claim 12, wherein the flapper valve means closes when the second flow conductor is withdrawn from the longitudinal passageway.

14. A well tool as claimed in claim 13, wherein the poppet valve means in its open position allows fluids to bypass the fluid barrier formed by the sealing elements and the exterior of the second flow conductor.

1 5. The method of preventing undesired escape of well fluids from a first well flow conductor while moving a second well flow conductor into or out of the first well flow conductor, comprising: a. releasably anchoring a well tool having housing means with a longitudinal flow passageway extending therethrough, a valve closure means having a first position allowing fluid flow through the first flow conductor and a second position blocking fluid flow through the first flow conductor, means for shifting the valve closure means between its first position and its second position in response to control fluid pressure from the well surface, and sealing means for forming a fluid barrier with the exterior of a second flow conductor when the second flow conductor is disposed within the longitudinal flow passageway, and the valve closure means having a poppet valve means and a flapper valve means; b. opening the poppet valve means by applying control fluid pressure from the well surface to equalize fluid pressure across the flapper valve means; c. inserting the second well flow conductor into the first flow conductor at the well surface; d. moving the second flow conductor longitudinally through the first flow conductor until the second flow conductor opens the flapper valve means; e. decreasing the control fluid pressure at the well surface to below a preselected value to close the poppet valve means if undesired fluid flow should occur in the annulus between the first and second flow conductor above the well tool; and f. withdrawing the second flow conductor from the longitudinal passageway to close the flapper valve means if undesired fluid flow should occur through the second flow conductor.

16. The method of claim 1 5 which further comprises energizing the sealing means to firmly engage the exterior of the second flow conductor by closing the poppet valve means.

17. The method of claim 15 which further comprises: a. using blowout preventers at the well surface as the primary barrier for preventing undesired well fluid flow; and b. shifting the valve closure means to its second position to establish a secondary barrier for preventing undesired well fluid flow.

1 8. A safety valve or well tool substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.

19. A method of preventing undesired escape of well fluids from a first well flow conductor whilst moving a second well flow conductor into or out of the first well flow conductor, substantially as herein described, by way of example, with reference to the accompanying drawings.