CA1190142A - Chemical injection system for offshore drilling rigs - Google Patents

Abstract

CHEMICAL INJECTION SYSTEM FOR OFFSHORE DRILLING RIGS

ABSTRACT OF THE DISCLOSURE
Conventionally, anti-freeze such as methanol, is injected through a chemical valve sub situated below the sea bed, with the chemical being pumped from the surface through a tube situated externally of the string. However, difficulty is encountered when passing through a blow-out preventer assembly particularly when associated with a slick joint and typically, internal and external bores and con-duits are used for this purpose with difficulties in effect-ing efficient seals engaging between the joints and bores together with the possibility of damage occurring to the external fluid conduit portions of the bypassing section.
The present invention utilizes a pierced slick joint assem-bly whereby the fluid is conveyed from the upper end of the centralizer, through the slick joint and through the lower hanger all internally, thus eliminating any possibi-lities of the collapsing of conduits or other damage from occurring. Furthermore, double fail closed check valves may be incorporated adjacent the upper end of the slick joint assem-bly as well as in the chemical valve sub in order to prevent oil and/or gas from entering the chemical carrying conduits if excess pressure is encountered.

Description

- l -CHEMICAL INJECTIO~ SYSTEM FOR OFFSHORE DRILLING RIGS

BACI~GROU~ID OF THE INVENTION
This invention relates to new and useEul improve-ments in a method and system for the injection of methanol or other chemicals below the sea floor during oil or gas tests on sub-sea exploration wells.
The coolest part of the well is normally just be-low the sea floor and water droplets in produced gas form low temperature hydrate plugs of ice or similar material thus blocklng off or interfering with the gas flow.
It is therefore conventional to purnp methanol or other chemicals including freezlng point depressants, from the surface, down a relatively small diametered con-duit to a chemical valve sub situated at the location witln-in the string tubing where these hydrates may form. This re-latively sma]l diametered conduit usually runs parallel to the string but difficulty is encountered in bypassing the blow-out preventer ram assembly which is usually situated around a slick joint above the sea bed or floorO
The rams of the blow-out preventer engage the preventer around the slick joint and this blow-out preventer has to be bypassed without crushing of the hose or contamina-tion of the contents of the hose from fluids in either the 3~

- 2 -annulus or the string tubing.
One such method is to provide a combination internal porting and external tubing between the centralizer and the hanger with the slick joint and blow-out preventer therebet-ween. In this method, a longitudinally extending groove is formed along the surface of the slick joint, a hose or con-duit is inserted within this groove which is then capped, but care must be taken in order to preserve the integrity of the slickjoint so that the blow-out preventer ram may work ef-fectively.
Also, a plurality of permanent and detachable junc-tions are provided along the length of the chemical carry-ing conduit in this method, each one of which adds to the possibility of leakage occurring because of the relative high pressure of the chemical fluid present within the tubing which may be between 10~000 and 15,000 lbs. per square inch.
SUMMARY OF THE INVENTION
The present invention overcomes all of these dis-advantages by providing an internal porting system extending from the upper end of the centralizer, through the slick joint wall, and through the fluted hanger component situa-ted on the lower end of the slick joint.
An external conduit extends from the upper end of the centralizer to the surface and a further external con-~ 3 ---duit extends from the lower end of the hanger to the chemical val.ve sub thus reducing considerably the number of junc-tions or joints within the chemical fluid carrying conduit and providing a complete inter~al porting system past the blow-out preventer.
In accordance with the invention there is provi-ded in a chemical injection assembly used primarily for t'ne conveying of a Ereezing point depressant, and connected to a well producing oil and/or gas, said well having a product carrying string extending therethrough and including a cen-tralizer component, a lower hanger component and a slick joint extendi.ng therebetween and a blow-out preventer assem-bly surrounding said slick joint; the improvement which in-cludes in combina-tion an internal chemical carrying porting extending through the wall of said centralizing component from one end to the other, an internal chemical carrying porting extending through the length of the wall of said slick joint from one end to the other and a fur-ther internal chemical carrying porting extending through the wall of said lower hanger component from one end to the ot'ner, said che-mical portings being operatively connected together inter-nally and in serial relationship with each other thereby form-ing a pierced slick joint assembly, and sealin~ means between the junctions of said internal portings.

3V~

In accordance with another aspect of the inven-tion there is provided an injector assembly in combination with an offshore oil and/or gas producing well, said well having a product carrying string extending therethrough, said product carrying string including a centralizer com-ponent, a lower hanger component~ a blow-out preventer as-sembly surrounding said slick joint, a chemical carrying porting extending vertically through the wall of said cen-tralizer component, an internal chemical carrying porting extending through the length of the wall of said slick~
joint from one end to the other and a further internal chemical carrying porting extending through the wall of said lower hanger component from one end to the other, said chemical portings being operatively connected toge-thér internally and in serial relationship with each other thereby forming a pierced slick joint assembly, and seal-ing means between the junctions of said internal portings.
In accordance with a still further aspect of the invention there is provided a method for conveying a che-mical past a blow-out preventer on a product carrying string of an offshore oil and/or gas producing well in which the blow-out preventer is operatively connected to a slick joint assembly which includes a centralizer component, a hanger component and a slick joint extending therebetween; said method comprising the forming of an internal porting ver-tically through the wall of said centralizer component, an internal porting extending through the length of the wall of said slick joint and a further internal porting extend-ing vertically through the lower hanger component, said portings being operatively connected together internally and in serial relationship with each other and having sealing means between the junctions of said internal port-ings, operatively connecting the upper end of the porting within said centralizer componen-t to a source of chemical under pressure at the surface, operatively connecting the lower end of the porting within said hanger component, with a chemical injector sub in said product carrying string below the sea bed and then pumping chemical therethrough.
A further advantage of the invention is to provide portings through the centralizer, the slick joint and the fluted hanger in which the connections bet-ween the portings in each component may readily be sealed in order to prevent leakage from occurring.
A still further advantage of the invention is to provide a device of the character herewithin des-cribed which is simple in construction and otherwise well suited to the purpose for which it is designed.

3 ~

With the foregoing in view, and other advantages as will become apparent to those skilled in the art to which this invention relates as this specification proceeds, the invention is herein described by reference to the accom-panying drawings orming a part hereof, which includes a description of the best mode known to the applicants and of the preferred typical embodiment of the principles of the present invention, in which:
DESCRIPTION OF THE DRAWINGS
Figure 1 is a schematic elevation of a portion of a gas and/or oil producing well in an offshore environ-ment.
Figure 2 is a composite view of the centralizer, slick joint, and lower hanger partially in section and con-sisting of Figures 2A, 2B, 2C and 2D.
Figure 3 is a composite view of the chemical injection sub also partially sectioned and consisting of Figures 3A and 3~.
Figure 4 is a top plan view of Figure 3 and is on the sheet carrying Figure 1.
In the drawings like characters of reference in-dicate corresponding parts in the different figures.
GENERAI. DESCRIPTION
Proceeding therefore to describe the invention generally, reference should first be made to Figure 1 in which 10 illustrates the rig floor of an oil or gas we]l forming part of a self-elevating platform with legs ex-tending to the sea floor (not illustrated).
Wel] casing 11 extends downwardly from the rig floor, to the oil or gas bearing zones (not illustrated) with reference character 12 illustrating sdea level and reference character 13 illustrating the sea floor. The casing 11 is provided with a truncated conical restriction 14 just above sea level with the casing portion llA des-cending downwardly therefrom of a slightly smaller dia-meter than the upper portion of the casing 11. Although this is shown just above sea level, it can be situated in other locations depending upon design parameters.
The test string collectively designated 15 con-sists of lengths of piping screw-threadably connected to-gether in a conventional manner which extends downwardly through the casing 11 and llA and which is supported at the truncated conical restriction 14 by means of a hanger com-ponent collectively designated 16. Situated spaced above 2~ the hanger component 16 is a centralizer component collec-tively designated 17 with a slick joint collectively de-signated 18 extending therebetween and these three com-ponents form part of the invention contained within the bracketed area designed 19 in Figure 1.

,~,9 ~
.~O_qV~ ~,4 The upper tubing 15A communicates at the lower end thereof to the centralizer 17 and a lower length of tubing 15B extends downwardly from the underside of the hanger which supports the tubing within the truncated res-triction 14 as will hereinafter be described.
A chemical valve injection assembly collectively designated 20 is situated below the sea floor, in this embodiment, for the injection of chemicals such as freez-ing point depressors and is positioned to be located with-in the area in which hydrates normally would form.
DETAILED DESCRIPTI~N
In detail, reference should be made to Figure 2 which shows the portion of the invention generally de-signated 19.
The centralizer component co~lectively designa-ted 17 is a cylindrical hollow body having a plurality of flutes 22 formed longitudinally through the outer surface so that drilling mud may pass thereby within the annulus 23A formed between the tubing 15A, 15B and the casing 11.
The outer surface 23 of the body forming the centralizer, contacts the casing 11 and centralizes the assembly for protective purposes.
The lower end of tubing 11 is screw-threadably engaged within the upper end of the centralizer with re-ference character 24 illustrating this internal threading in the centralizer.
The slick joint collectively designated 18 is a length of tubing with no external upsets over its major length and it is screw-threadably secured to the lower end of the centralizer component via screw threads 25 shown in Figure 2A. This slick joint is screw-threadably secu-red at the lower end thereof via threads 26, to the upper end of the hanger component 16. This cylindrical hanger component is also fluted as at 27 to allow drilling mud to pass thereby through the annulus, and is provided with a conical base 28 which engages within the truncated res-triction 14 and suspends the entire tubing assembly with-in the casing being centralized by the centraliæer com-ponent 17.
The upper end of the lower tubing 15B is screw-threadably engaged within the lower end of the hanger component via screw threads 29 thus completing the assem-bly 19.
An upper length of externally situated conduit or hose 30 extends from a pump on the rig and the pump is operatively connected to a source of chemical fluid to be pumped downwardly to the chemical valve sub 20. A lower external conduit or hosing 31 extends below the hanger and ~Vl~'~

operatively connects with the chemical valve sub 20.
Reference to Figure 1 will show schematically, a blow-out preventer and ram assembly 32 surrounding the slick joint between the centralizer component 17 and the hanger component 16 so that when actuated by hydraulic rams in a conventional manner, seals around the slick joint 18 during a production flow test thereby isolating the annu-lar space 23A between the tubing 15B and the casing llA be-low the blow-out preventer, from the annular space 23 between the tubing 15A and the casing 11, situated above the blow-out preventer. Pressure may then be exerted upon or contained within the lower annular space 23A with the flow from the well being tested passing upwardly through the tubing 15B and 15A.
As mentioned previously, internal porting is provided clear through the portion of the invention iden-tiEied as 19 and dealing first with this internal port-ing through the centralizer component 17, reference should be made to Figure 2A.
A bore or port 33 extends downwardly from the horizontal shoulder 34 within the open upper end 35 and through the wall 36 of the centralizer to a location indica-ted by reference character 37. A radially extending bore 38 extends from adjacent the lower end of bore 33 inwardly to the main bore of the centralizer.
The diameter of various portions of the bore 33 gradually decrease from the upper end thereof to receive a cylindrical check valve plug 39 which is screw_threadably engaged within the bore, said check valve plug including a sealing O ring 40 and a pair of one-way check valves 41, one above the other, permitting the flow of fluid downwardly in the direction of arrow 42. These check valves are fail closed and are bubble proof so that any back pressure from the pro-ducing section of the well due to failure of the pur.lp or the likeg will not pass these fail closed valves. The con-struction of these valves is conventional so tha-t it is not believecl necessary to describe same further.
An adapter 43 screw threadably engages within the upper end of the check valve plug 39 and the lower end of the upper external conduit or hose 30 is screw thread-ably en~aged therewith in sealing relationship in a conven-tional manner.
Referring next to Figure 2B which shows the ~0 pierced slick joint, this comprises a length of piping or tubing having a smooth external surface and around which the bLow-out preventer together with the rams 32 may engage.
It is hollow and communicates at the upper end thereof with the hollow centralizer and thence to the production test ~IL~
V ~

tubin~ 15A. The slick joint is conventionally approximately 10 to 12 feet in length and a bore or port 44 is Eormed lon-gitudinally through the wall 45 thereof from the upper end 45 to the lower end 47. Once the bore has been formed, pipe plugs 48 are screw threadably engaged within either end of the bore in order to close same.
Ad-jacent the upper end of the bore 44, a radially extending bore 49 is formed communicating with the bore 44 and to the outside surface o~ the upper end of the slick joint above the screw threading 25 and when assembled as shown in Figure 2A, this bore 49 aligns with the radial bore 38 within the centralizer. Indicating means (not il-lustrated) are provided on both of the external surfaces of the centralizer and t'ne slick joint in order to ensure this alignment.
O rings 50 and 51 are provided above and below the junction between the bores together with a retainer ring 52, a split ring 53 and an L ring 54, all of which assist in maintaining the integrit~7 o~ the seal between the radial ports 38 and 49 and isolate t'ne porting from both the fluids passing upwardly through the tubing 15 and through the annulus 23A.
Reference should next be made to Figure 2C which shows in detail, the construction of the hanger component 16.

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This is provided with a longitudinal bore or port 54 extend-ing upwardly from the horizontal shoulder 55 within the lower open end 56 thereof, to a location indicated by refer-ence character 57 whereupon a radially extending bore 58 extends from adjacent the point 57, inwardly to the inte-rior of the hanger,which is hollow,communicating with the internal bore 59 of the tubing..
A further radial bore 60 extends from adjacent the lower end of the bore 44 through the slick joint wall, to the exterior of the slick joint below the screw threading 26 and this aligns with the radial bore 58 when the parts are assembled, similar markings being provided to ensure the integrity of this alignment.
Seals are provided similar to those between the upper end of the slick joint and the centralizer and similar reference characters have been given. In addition~ a fur-ther O ring 61 is provided between the upper end of the tubing 15B and a shoulder 62 formed intermediate the ends of the hanger against which the adjacent ends of the slick joint and tubing 15B engage.
A further adaptor 63 screw threadably engages the lower end of the bore or port 54 to which the upper end of the lower external conduit or hose 31 may be attached in sealing relationship similar to the connection to the adaptor 43.
It will therefore be seen that when the assembly 19 is assembled as illustrated in Figure 2, an endless port or bore is provlded from the upper end of the centralizer to the lower end of the hanger completely within the assem-bly with the sealing rel.ationship of the various portions of the bore being maintained with full integrity against leakage from either the tubi.ng bore 59 or the annulus 23 or 23A.
The tubing 15B extending below the hanger com-ponent 16 may include a cross-over assembly or component 64 which is conventional in construction with the tubing extending to the chemical valve or safety valve sub 20 situated at the desired relationship below the blow-out preventer assembly 18 and details of this sub are shown in Figure 3.
It consists of a cylindrical length of tubing 65 having a conventional connection (not illustrated) at the other end and a similar connection at the lower end so that it may be connected in series with in the tubing 15B at the desired location.
It is fluted as at 66 and an enlarged portion 67 is longitudin.ally apertured as at 68 through which the lower end of the external conduit or hosing 31 may extend as ._ 15 shown in Figure ~.
Spaced below the lower end of the portion 67 is a portion ~9 of the wall of the tubing which is longitudinally bored to provide a connection for the lower end of the con-duit or hosing 31 and to permit injection into the interior of the sub which is longitudinally bored as at 70.
A bore 71 extends upwardly from adjacent the lower end 69B of the wall portion 69 inclining inwardly at a slight angle and screw threadably receiving a seal plug 72 with O
rings 73 providing a satisfactory seal. An annular retainer ring 74 is situated adjacent the lower end of the bore 71.
A pair of one-way valves 75 are situated within the portion of the bore above the plug 72 and these valves are similar in construction to valves 41 hereinbefore des-cribed and are conventional. They permit fluids to pass only in the direction of arrow 76 and are fail closed and bubble proof against gas under pressure which may inadver-tently attempt to move in a direction opposite to arrow 76. The bores of these valves communicate with a small bore or port 77 formed within the inner end of the sealing plug 72 which in turn communicates with a cross bore 78 formed across the sealing plug 72 and into an annulus 79 surround-ing the inner end of the sealing plug. This annulus communi-ca-tes with a radial bore 30 extending through the wall por-tion 69A of the tubing 65 and into the interior bore 70 of the sub.
An adaptor 81 screw threadably engages a bore portion 82 formed in a shoulder 83 of the wall 69 and a further bore 82A communicates between this adaptor and the bore within which the valves 75 are engaged. The lower end of the conduit or hosing 31 screw threadably engages the adaptor plug 81 in sealing relationship in a conven-tional manner.
By locating the sub 21 in the desired locàtion along the tubing 15B, any liquid chemical may be injected at will although it is designed primarily for a freezing point depressor chemical such as methanol or some similar chemical.
Since various modifications can be made in our invention as hereinabove described, and many apparently widely different embodiments of same made within the spi-rit and scope of the claims without departing from such spirit and scope, it is intended that all matter contained in the accompanying specification shall be interpreted as illustrative only and not in a limiting sense.

Claims

CLAIMS:
(1) In a chemical injection assembly used primarily for the conveying of a freezing point depressant, and connec-ted to a well producing oil and/or gas, said well having a product carrying string extending therethrough and including a centralizer component, a lower hanger component and a slick joint extending therebetween and a blow-out preventer assembly surrounding said slick joint; the improvement which includes in combination an internal chemical carrying port-ing extending through the wall of said centralizing compo-nent from one end to the other, an internal chemical carry-ing porting extending through the length of the wall of said slick joint from one end to the other and a further in-ternal chemical carrying porting extending through the wall of said lower hanger component from one end to the other, said chemical portings being operatively connected together internally and in serial relationship with each other there-by forming a pierced slick joint assembly, and sealing means between the junctions of said internal portings.
(2) The improvement according to Claim 1 which in-cludes a double fail normally closed valve assembly in said pierced slick joint assembly.
(3) The improvement according to Claim 2 in which said valve assembly is situated within said centralizer com-ponent and within the internal porting extending there-through.
(4) The improvement according to Claim 1 in which said internal porting in said centralizer component ex-tends vertically through the wall thereof from the upper end thereof to adjacent the end connecting with the upper end of said slick joint and then communicating inwardly through the wall to the interior of the lower end thereof to communicate with the upper end of the porting of said slick joint.
(5) The improvement according to Claim 3 in which said internal porting in said centralizer component ex-tends vertically through the wall thereof from the upper end thereof to adjacent the end connecting with the upper end of said slick joint and then communicating inwardly through the wall to the interior of the lower end thereof to communicate with the upper end of the porting of said slick joint.
(6) The improvement according to Claim 1 in which said internal porting in said hanger component extends ver-tically through the wall thereof from the lower end thereof upwardly to adjacent the end connecting with the lower end of said slick joint and then communicates inwardly through the wall to the interior of the upper end thereof to commu-nicate with the lower end of the porting of said slick joint.
(7) The improvement according to Claim 1 which includes a chemical injection sub in said string situated below the sea bed and being operatively connected to said chemical injection assembly, and means to connect said chemical assembly to a source of chemical at the surface.
(8) The improvement according to Claim 2 which includes a chemical injection sub in said string situated below the sea bed and being operatively connected to said chemical injection assembly, and means to connect said chemical assembly to a source of chemical at the surface.
(9) The improvement according to Claim 3 which includes a chemical injection sub in said string situated below the sea bed and being operatively connected to said chemical injection assembly, and means to connect said chemical assembly to a source of chemical at the surface.
(10) The improvement according to Claim 4 which includes a chemical injection sub in said string situated below the sea bed and being operatively connected to said chemical injection assembly, and means to connect said chemical assembly to a source of chemical at the surface.
(11) The improvement according to Claim 5 which includes a chemical injection sub in said string situated below the sea bed and being operatively connected to said chemical injection assembly, and means to connect said chemical assembly to a source of chemical at the surface.
(12) The improvement according to Claim 6 which includes a chemical injection sub in said string situated below the sea bed and being operatively connected to said chemical injection assembly, and means to connect said chemical assembly to a source of chemical at the surface.
(13) The improvement according to Claims 1, 2 or 3 which includes a first external, chemical carrying conduit extending between the upper end of the porting in said cen-tralizer component and being operatively connected thereto, said first external chemical carrying conduit lying substan-tially parallel to the product carrying string and being operatively connected to a source of chemical under pressure at the surface, and a second external chemical carrying conduit extending from the lower end of the porting in said hanger component and being operatively connected thereto, said second external carrying conduit lying substantially parallel to the product carrying string and being operatively connected to said chemical injection sub.
(14) The improvement according to Claims 4, 5 or 6 which includes a first external, chemical carrying conduit extending between the upper end of the porting in said cen-tralizer component and being operatively connected thereto, said first external chemical carrying conduit lying substan-tially parallel to the product carrying string and being operatively connected to a source of chemical under pressure at the surface, and a second external chemical carrying conduit extending from the lower end of the porting in said hanger component and being operatively connected thereto, said second external carrying conduit lying substantially parallel to the product carrying string and being operatively connected to said chemical injection sub.
(15) The improvement according to Claims 7, 8 or 9 which includes a first external, chemical carrying conduit extending between the upper end of the porting in said cen-tralizer component and being operatively connected thereto, said first external chemical carrying conduit lying substan-tially parallel to the product carrying string and being operatively connected to a source of chemical under pressure at the surface, and a second external chemical carrying conduit extending from the lower end of the porting in said hanger component and being operatively connected thereto, said second external carrying conduit lying substantially parallel to the product carrying string and being operatively connected to said chemical injection sub.

(16) The improvement according to Claims 10, 11 or 12 which includes a first external, chemical carrying con-duit extending between the upper end of the porting in said centralizer component and being operatively connected there-to, said first external chemical carrying conduit lying sub-stantially parallel to the product carrying string and be-ing operatively connected to a source of chemical under pressure at the surface, and a second external chemical carrying conduit extending from the lower end of the porting in said hanger component and being operatively connected thereto, said second external carrying conduit lying substan-tially parallel to the product carrying string and being operatively connected to said chemical injection sub.
(17) A chemical injection assembly in combin-ation with an offshore oil and/or gas producing well, said well having a product carrying string extending there-through, said product carrying string including a centralizer component, a lower hanger component and a slick joint ex-tending therebetween, a blow-out preventer assembly sur-rounding said slick joint, a chemical carrying porting ex-tending vertically through the wall of said centralizer com-ponent, an internal chemical carrying porting extending through the length of the wall of said slick joint from one end to the other and a further internal carrying por-ting extending through the wallof said lower hanger component from one end to the other, said chemical portings being operatively connected together internally and in serial relationship with each other thereby forming a pierced slick joint assembly, and sealing means between the junctions of said internal portings.
(18) The improvement according to Claim 17 which includes a double fail normally closed valve assembly in said pierced slick joint assembly.
(19) The improvement according to Claim 18 in which said valve assembly is situated within said centralizer component and within the internal porting extending there-through.
(20) The improvement according to Claim 17 in which said internal porting in said centralizer component extends vertically through the wall thereof from the upper end thereof to adjacent the end connecting with the upper end of said slick joint and then communicating inwardly through the wall to the interior of the lower end thereof to communicate with the upper end of the porting of said slick joint.
(21) The improvement according to Claim 18 in which said internal porting in said centralizer component extends vertically through the wall thereof from the upper end thereof to adjacent the end connecting with the upper end of said slick joint and then communicating inwardly through the wall to the interior of the lower end thereof to communicate with the upper end of the porting of said slick joint.
(22) The improvement according to Claim 17 in which said internal porting in said hanger component extends vertically through the wall thereof from the lower end there-of upwardly to adjacent the end connecting with the lower end of said slick joint and then communicates inwardly through the wall to the interior of the upper end thereof to com-municate with the lower end of the portion of said slick joint.
(23) The improvement according to Claim 17 which includes a chemical injection sub in said string situated below the sea bed and being operatively connected to said chemical injection assembly and means to connect said chemical assembly to a source of chemical at the surface.
(24) The improvement according to Claim 18 which includes a chemical injection sub in said string situated below the sea bed and being operatively connected to said chemical injection assembly, and means to connect said chemical assembly to a source of chemical at the surface.
(25) The improvement according to Claim 19 which includes a chemical injection sub in said string situated below the sea bed and being operatively connected to said chemical injection assembly, and means to connect said chemical assembly to a source of chemical at the surface.
(26) The improvement according to Claim 20 which includes a chemical injection sub in said string situated below the sea bed and being operatively connected to said chemical injection assembly, and means to connect said chemical assembly to a source of chemical at the surface.
(27) The improvement according to Claim 21 which includes a chemical injection sub in said string situated below the sea bed and being operatively connected to said chemical injection assembly, and means to connect said chemical assembly to a source of chemical at the surface.
(28) The improvement according to Claim 22 which includes a chemical injection sub in said string situated below the sea bed and being operatively connected to said chemical injection assembly, and means to connect said chemical assembly to a source of chemical at the surface.
(29) The improvement according to Claims 17, 18 or 19 which includes a first external, chemical carrying con-duit extending between the upper end of the porting in said centralizer component and being operatively connected there-to, said first external chemical carrying conduit lying sub-stantially parallel to the product carrying string and being operatively connected to a source of chemical under pres-sure at the surface, and a second external chemical carry-ing conduit extending from the lower end of the porting in said hanger component and being operatively connected there-to, said second external carrying conduit lying substanti-ally parallel to the product carrying string and being ope-ratively connected to said chemical injection sub.
(30) The improvement according to Claims 20, 21 or 22 which includes a first external, chemical carrying con-duit extending between the upper end of the porting in said centralizer component and being operatively connected there-to, said first external chemical carrying conduit lying sub-stantially parallel to the product carrying string and being operatively connected to a source of chemical under pres-sure at the surface, and a second external chemical carry-ing conduit extending from the lower end of the porting in said hanger component and being operatively connected there-to, said second external carrying conduit lying substanti-ally parallel to the product carrying string and being ope-ratively connected to said chemical injection sub.
(31) The improvement according to Claims 23, 24 or 25 which includes a first external, chemical carrying con-duit extending between the upper end of the porting in said duit extending between the upper end of the porting in said centralizer component and being operatively connected there-to, said first external chemical carrying conduit lying sub-stantially parallel to the product carrying string and being operatively connected to a source of chemical under pres-sure at the surface, and a second external chemical carry-ing conduit extending from the lower end of the porting in said hanger component and being operatively connected there-to, said second external carrying conduit lying substanti-ally parallel to the product carrying string and being ope-ratively connected to said chemical injection sub.
(32) The improvement according to Claims 26, 27 or 28 which includes a first external, chemical carrying con-duit extending between the upper end of the porting in said centralizer component and being operatively connected there-to, said first external chemical carrying conduit lying sub-stantially parallel to the product carrying string and being operatively connected to a source of chemical under pres-sure at the surface, and a second external chemical carry-ing conduit extending from the lower end of the porting in said hanger component and being operatively connected there-to, said second external carrying conduit lying substanti-ally parallel to the product carrying string and being ope-ratively connected to said chemical injection sub.

(33) A method for conveying a chemical past a blow-out preventer on a product carrying string of an off-shore oil and/or gas producing well in which the blow-out preventer is operatively connected to a slick joint assem-bly which includes a centralizer component, a hanger com-ponent and a slick joint extending therebetween; said me-thod comprising the forming of an internal porting ver-tically through the wall of said centralizer component, an internal porting extending through the length of the wall of said slick joint and a further internal porting ex-tending vertically through the lower hanger component, said portings being operatively connected together internally and in serial relationship with each other and having sealing means between the junctions of said internal portings, operatively connecting the upper end of the porting within said centralizer component to a source of chemical under pressure at the surface, operatively connecting the lower end of the porting within said hanger component, with a chemical injector sub in said product carrying string be-low the sea bed and then pumping chemical therethrough.
(34) The method according to Claim 33 in which the chemical is a freezing point depressor.
(35) The method according to Claim 34 in which the freezing point depressor is methanol.

(36) The method according to Claims 34 or 35 which includes providing at least one double fail closed valve assembly within the porting, to prevent oil/gas leakage from said well and through said porting beyond the upper end of said centralizer component.