GB2359579A - Redundant nose seal for a production fluid drainage apparatus - Google Patents

Abstract

A production fluid drainage apparatus 18 for a subterranean well comprises seal apparatus to prevent pressurized well fluid from entering, via an annular gap 90, an annular fluid flow passage 32 defined between the base pipe 26 and an outer tubular structure 30. The seal apparatus is disposed axially outward of a sidewall inlet opening 28 of the base pipe 26 and comprises an annular interior recess surface 86 disposed on the outer tubular structure 30, and a quantity of adhesive type resilient sealant material 102. The sealant 102 fills both the recess 86 and the annular gap 90. The sealant is preferably a chemically curing polyioether polymer-based material. An epoxy xylene primer material may be applied to the base pipe and the tubular structure. A method of sealing the apparatus is also disclosed.

Description

2359579 PRODUCTION FLUID DRAINAGE APPARATUS FOR A SUBTERRANEAN WELL The

present invention generally relates to the retrieval of production fluids in subterranean wells and, in a preferred embodiment thereof, more particularly relates to screened or filtered drainage pipe structures used to filter and retrieve production fluids in horizontal subterranean wells, and having selected, variable length labyrinth inlet flow control apparatus.

The elongated horizontal fluid-receiving subterranean piping portion in a horizontal well is typically formed from joined drainage pipe sections. Each drainage pipe section has an. external screen or other filter structure thereon for filtering production fluid'being forced inwardly through the screen into the interior of drainage pipe section via suitable side wall openings therein. The horizontal piping portion has an upstream end commonly referred to as the "toe" of the overall underground piping structure, and a downstream or "heel" end joined to the vertical piping portion leading to the surface.

A well-known problem in this type of production fluid retrieval system is that the flow rate of fluids produced from a horizontal well is not uniform over the horizontal producing length of the well. Instead, the fluid inflow rate is generally high near the heel compared to the toe due to the inherent pressure drop in the horizontal section of the well bore. This differential production rate, in some instances, could undesirably limit the maximum production fluid drainage that can be achieved for a given reservoir.

One previously proposed method of preventing this i L undesirable production fluid inflow rate along the hee'-to-toe length of the horizontal piping portion of the well is to incorporate adjustable choke structures (commonly referred to as inlet control devices of "ICD's") in the individual drainage pipe sections to control the inflow rate to each drainage pipe section in a manner providing an essentially constantinflow rate profile a-Long the heel-to-toe length of the horizontal pining section. This desirable result may be at least theoretically achileved by setting the chokes to have progressively higher hydraulic resistances from the heel to the toe of the horizontal piping portion of the subterranean well.

While this theoretical approach to equalizing inflow along the hori zontal piping length would appear to be a relatively simple and straightforward solution inflow problem in horizontal wells, concept into a practical design in to be surprisingly difficult due to the nonuniform drainage actual embodiment of this horizontal wells has proven in large part to geometrical limitations of the available space in typical horizontal well applications, and due to the tolerances on the pipe diameters requiring highly demanding seal designs in the choke structures.

For example, in one previously proposed type of choke or inlet control device, illustrated and described in U.S. Patent 5,435,393 to Brekke et al, a labyrinth structure having a selectively variable effective flow passage length is interposed between the flow outlet side of the outer filter structure and the inlet openings in the interior base pipe portion of the overall screened drainage pipe section. Thus, -3during operation of the drainage pipe section, production fluid is sequentially forced inwardly through the filter, through the labyrinth structure, inwardly through the side wall openings in the base pipe, and through the interior of the base pipe to the surface via the balance of the production piping length.

Using, for example, external plug devices removably inserted into various ones of the labyrinth passages as shown in the aforementioned U.S. Patent 5,425,393 to Brekke et al, the effective length and thus flow resistance of the labyrinth may be selectively varied to correspondingly adjust the fluid inflow rate to the interior of the base pipe.

At production fluid pressures typically encountered in horizontal wells, the overall effectiveness and flow control accuracy of this general type of adjustable labyrinth inlet control device tends to be substantially degraded due to the tendency of production fluid to at least- partially bypass the labyrinth passageway on its way into the interior of the base pipe through two leakage flow paths.

The first leakage flow path labvrinth structure and the is disposed between the structure which operatively supports it exteriorly on the base pipe. Due to the presence of this first leakage flow path, an often substantial amount of the production fluid inwardly exiting the screen or filter simply bypassed its intended labyrinth passageway and flowed into the base pipe without being subjected to the adjustable flow resistance of the labyrinth. Due to the unavoidably different clearances between the labyrinths and their associated base pipes and support structures, the degree of by-pass leakage was a varil-able factor which to a substantial extent prevented accurate adjustment of each base pipe inflow rate using the labyrin-.-h adjustment structure.

UnlLke the f-'-rst leakage flow path, the second 'Leakage flow path permits the well fluid to bypass the external filter or screen structure, and at least a portion of the intended labyrinth passageway, and flow unfiltered into the interior of the base pipe. A po--tJLon of this second leakage flow path can occur at the external i::)-!ug devices extending through the labyrinth strucuure into various ones of its internal flow passages. P_-essurized unfiltered production fluid tends to leak inwardly through these plug devices into their associated. labyrinth passages, -, hereby undesirably bypassing a portion of the intended labyrinth flow length and altering its otherwise predictable effect on the production fluid inflow rate to the base pipe. An additional portion of this second leakage flow path can occur between the labyrinth and its supporting structure, at the outlet end of the labyrinth structure, and undesirably base pipe intended.

As cap. readily be seen highly desirable to provide, filtered well labyrinth type inlet permit upf--'ltered -production fluid to enter the without operatively traversing the labyrinth as from the foregoing, it would be in a screened or otherwise drainage pipe section, improved adjustable flow control apparatus, and associated L- methods, in which the above-mentioned problems, limitations and disadvantages of conventional labyrinth type inlet control T devices are eliminated o_r ar- least substantially reduced. -L is accordingly an object of the present invention to provide such improved adjustable labyrinth type inlet flow control apparatus and associated methods.

In carrying out principles of the present invention, in accordance with a preferred embodiment thereof, a subterranean drainage pipe structure is provided with a fluid flow control structure which, due to unique sealing techniques incorporated in various locations in the overall drainage pipe structure, provides for enhanced accuracy in regulating the well fluid flow into the drainage pipe structure. Thus, when a series of the drainage structures are joined end-to-end in the horizontal portion of a subterranean well the production fluid retrieval rate may be more precisely equalized along the length of the drainage pipe string, from its toe portion to its heel portion, to thereby more nearly optimize the well production rate.

Each drainage pipe structure representatively comprises a tubular base pipe having, in opposite end portions thereof, at least one sidewall fluid inlet opening. A tubular structure coaxially circumscribes the base pipe and forms therewith an annular flow passage that surrounds the base pipe and communicates with the interior of the base pipe via its sidewall inlet openings. A longitudinally central portion of the tubular structure is defined by a fluid filtering apparatus, preferably a tubular sand screen assembly, The outer ends of the sand screen are positioned axially inwardly of the base pipe sidewall openings, and opposite outer end portions of the tubular structure are positioned axially ou--wardly of the base pipe sidewall openings.

Coaxially in--erDosed in opposite end portions of the annular flow passage, be-nween the oppos'Lue ends of the sand screen assembly and the base pipe sidewall inlet openings, are a pair of annular flow control members each having inner and outer side surfaces and a fluid flow passage axially traversing the flow control member. Accordingly, pressurized well fluid passing inwardly through the sand screen assembly into the underlying annular flow passage then sequentially flows through the flow control member passages, -through remaining portions o_ the annular flow passage between the base pipe and the tubular structure, and into the interior of the base pipe via its sidewall inlet openings.

Preferably, the fluid passage in each flow control member is a labyrinth flow passage recessed into its outer side surl-Eace and having an inlet por' Lion extending into the flow control member end facing the sand screen assembly, labyrinth portion extending circumferentially around control member, and a circumferentially spaced series portions extending from the main labyrinth portion through the flow control member end facing away from screen assembly.

The flow rate through the well fluid flow rate i selectively regulated by fluid flow length of its preferred embodiment of the a main the flow of outlet outwardly the sand each flow control member, and thus nto its associated base pipe, is selectively varying the effective labyrinth flow passage. In the present invention, this is achieved using specially designed first and second plug structures each of which has a resilien-IC portion that operates to sealingly block off selected ones of the labyrinth passage outlet portions, while leaving a selected one of the outlet passage portions unblocked. Each plug structure has associated series of therewith one of a circumferentially spaced internally threaded circular holes that are formed through the tubular structure in alignment with the underlying labyrinth flow passage outlet portions.

Each first plug structure has (1) a resilient portion having a first section receivable in one of the labyrinth passage outlet portions, and (2) a second section receivable in an inner end portion of the overlying tubular structure openings; and a rigid portion that is threadable into the opening into forcible engagement with the first resilient portion section in a manner deforming the resilient portion into a sealingly blocking relationship with its associated tubular structure opening and its associated labyrinth passage outlet portion.

Each second plug structure has (1) a first rigid portion positionable at the inner end of its associated tubular structure opening with an inner side thereof resting on flow control member outer side surface ledge portions adjacent thereto, (2) a resilient portion secured to the outer side of the rigid portion, and (3) a second rigid portion threadable into the associated tubular structure into forcible engagement with the resilient portion in a manner deforming it into sealingly blocking engagement with the tubular structure opening.

1 - 1 - The fi rst and second piug structures, 'M addition to be-ina operative to selectively vary the well fluid flow -through the flow control members, also form part of the improved overa'I f -L sealing structure of the present invention by functioning to L- L - essentia'',v prevent undesirable well fluid inflow through the plug openings which would permit such in-f-lowing well fluid to bypass an intended portion of -he intended total labyrinth Passaae -::low lenath and thereby degrade the regulation accuracy o-l the flow control oortion of the overall drainage pipe structure.

In the oreferred embodiment of the present invention, another por-. nion of the imoroved overall sealing apparatus i positioned at the opposite ends of the tubular structure and functions to essentially prevent well fluid inflow axially inwardly beneath such opposite ends into the annular flow passage, thereby permitting such inflowing well the annular flow control members and enter interior without traversing t-1h e intended 1 passages.

This second portion of the improved sealing apparatus provides redundant nose seals at the opposite ends of the tubular structure coaxially surrounding the base p-,pe. Each tubular structure end port-ion, at its outer end, defines an annular gap around the base pipe communicating at its axially inner end enlarged annular interior side sur.-::ace structure end portion. A -first oortion seal is formed by injecting an adhesive -fluid to bypass the base pipe abyrinth flow such annular gap with a diametrically recess in the tubular of each redundant nose type resilient sealant - Q material into the annular recess, through spaced sidewall openings in the tubular structure, in a manner filling it and forcing a portion of the injected sealant outwardly into the annular gap.

To facilitate the formation of this seal portion, annular exterior side surface recesses are formed in the base pipe in opposing relationships with the outer end portions of the tubular structure. The surfaces of these recesses. and opposing interior side surface portions of the tubular structure have a suitable primer material applied thereto prior to the injection of the adhesive type sealant material Preferably, the primer material is an epoxy xylene material, and the adhesive sealant material is a chemically curing polythioether polymer-based sealant material.

In defined sealant, includes inwardly tubular annular addition to the annular resilient seal structure by the injected quantity of adhesive type resilient each redundant nose seal apparatus also preferably (1) an elastomeric 0-ring seal disposed axially of the injected sealant and compressed between the structure and -the base pipe, and (2) lip seal member disposed axially inwardly of the 0-ring seal, having a generally C-shaped cross section, and being compressed between the tubular structure and the base pipe.

In the preferred embodiment of the present invention, a third portion of the overall improved seal apparatus is disposed at each of the annular flow control members and serves to essentially prevent any appreciable quantity of pressurized well. fluid from axially traversing the flow control member an elastomeric without passing through the entire its '-labyrinth _flow passage. A t member such third seal apparatus (1) a first generally annular seal intended effective length of each annular flow control portion Qreferably includes structure oositioned between the outer side surface of the flow control member and the Lac-ing interior side surface portion and (2) a second between the inner s facina outer side The first representatively preferably rubber, surface portion O-L between the flow generally annular seal of: the -tubular structure, structure positioned ide surface of the flow control member and a surface portion of the generally f or,--ted by adhered to the nonrecessed the -flow control member and control member and the facing surface portion of the tubular structure.

this elastomeric coating, and the proDer axial the flow control member 4:

preferably facilitated by complementary conical tapers portions.

The second generally annular seal structure representatively includes an annular outer side surface recess formed in the base pipe and facing the inner side surface of the annular flow control member. The surface of this recess and the facing inner side surface of the flow control member are coated with a nrimer material, preferably an epoxy xylene material. Disposed in an axially central portion of this recess is an annulus of ad"-,,--sive type sealant material which is annular a thin base pine.

seal structure elastomeric coating, outer side compressed inner side The comnression of nositioning of within the Lubular structure is providing each with small along their facing side surface is sealingly adhered to facing primed surface areas of the recess and the inner side surface of the flow control member. The adhesive type sealant material, preferably a chemically curing polythioether polymer-based sealant material, is operatively positioned within the drainage pipe structure by injecting predetermined quantities thereof through circumferentially spaced injection openings extending inwardly through the tubular structure, and underlying openings -Lormed in nonrecessed sidewall portions of the flow control member, into the annular space between the base pipe and the flow control member.

According to another feature of the present invention, the radial alignment of the base pipe and its outwardly circumscribing tubular structure, and thus the thickness uniformity of the various annular spaces within the drainage pipe structure, is facilitated by a centering structure incorporated in the drainage pipe structure. Representatively, such centering structure includes axially spaced apart series of circumferentially spaced internally threaded sidewall openings formed in the tubular structure, adjustment members threadingly received i and a series of n the internally threaded sidewall openings and bearing against the base pipe. Preferably, these sidewall openings spaced series thereof include circumferentially extending through opposed outer end portions of the tubular structure, and circumferentially spaced series thereof extending through the tubular structure axially outwardly adjacent the opposite ends of the tubular sand screen assembly.

Reference is now made to the accompany drawings, in which:

FIG. 1 is a schematic cross-sectional view through a horizontal well illustratinR a drainage pipe assembly made up of screened drainage pipe sections incorporating an embodiment of inlet flow control structures according to the present invention:

FIG. 2 is an enlarged scale, horizontally foreshortened schematic side elevational view of the drainage pipe section within the dashed line area 'W^ in FIG. 1; FIG. 3 is an enlarged scale quarter sectional view of the portion of the drainage pipe section within the dashed line area "B" in FIG. 2; FIG. 4 is an enlaraed scale detail view of the dashed line area "C" in FIG. 3; FIGS. 5A-5C, respectively, are top plan, side elevational and end elevational views of an embodiment of a resilient portion of a specially designed labyrinth passage closure structure according to the present invention and cross-sectionally illustrated in FIG. 4-, FIG. 6 is an outer side elevational view of outer housing opening with which the closure structure is operatively associated; FIG. 7 is an enlarged scale cross-sectional view through an embodiment of a labyrinth portion of the inlet flow control structure of the present invention; FIG. 8 is a reduced scale developed exterior side view of the labyrinth portion; FIG. 9 is an enlarged scale cross-sectional view -through the labyrinth portion taken along line 9-9 of FIG. 8 and illustrating a specially designed housing opening closure plug structure installed in -the screened drainage piping section outwardly of one of the labyrinth flow passages; FIG. 10 is a top plan view of a sealing disc portion of the closure plug structure; FIG. 11 is a cross-sectional view through the sealing disc portion taken along line 11-11 of FIG. 10; and FIG. 12 is an enlarged scale detail view of the dashed line area "D" in FIG. 3.

Depicted in highly schematic form in FIG. 1 is a portion of a horizontal subterranean well 10 having a wellbore 12 formed in the earth 14 and having a generally vertical portion 12a leading to the surface, and a generally horizontal portion 12b extending through a subterranean well fluid production zone. To retrieve production fluid, such as oil, from the well 10 a production piping string 16 is extended from the surface downwardly through the wellbore 12 and has a horizontal portion disposed in the wellbore section 12b and made up of individual drainage pipe sections 18 coaxially joined together by suitable couplings 20. The horizontal portion of the piping string 16 has a "heel" section 22 and a "toe" section 24 as indicated in FIG. 1.

Referring now to FIGS. 1 and 2, as subsequently described in greater detail herein, each drainage pipe section 18 basically comprises a tubular inner or base pipe 26 with 14 opposite left and right end portions 26a and 26b in each of which is formed a circumferentially spaced series of axially extending fluid inlet slots 28. A tubular outer inlet flow structure 30 coaxialiy circumscribes the base pipe 26 and forms a flow passage 32 disposed between the base pipe 26 and the flow structure 30 and extending between the two sets of fluid inlet slots 28 as schematically depicted in FIG. 2. A longitudinally central portion of the tubular inlet flow structure 30 is defined by a fluid filtration structure, representatively a stainless steel wire wrapped sand screen assembly 34.

During operation of the well 10, pressurized production fluid F flows inwardly through the sand screen 34, which filters particulate matter from the production fluid, horizontally through the flow passage 32, inwardly through the two series of base pipe slots 28 into the interior of the base pipe 26, and then leftwardly through the base pipe 26 for delivery to the surface through the balance of the piping string 16.

According to a key feature of the present invention, production fluid inflow to the various drainage pipe sections 18 in the horizontal portion of the piping string 16 is substantially equalized, thereby tending to substantially maximize the production fluid retrieval from the well 10, using a specially designed fluid flow control structure in the form of a selectively variable length labyrinth structures 36 interposed in the passage 32 between the opposite ends of the sand screen assembly 34 and the two sets of base pipe fluid inlet slots 28. In each drainage pipe section 18 j ---t -15the labyrinth structul-es 36 serve as inlet control devices (ICD's) and, as subsequently described in detail herein, are provided with specially designed seal structures that also embody principles of the present invention and provide for substantially improved fluid inflow control accuracy in each drainage pipe section 18.

Referring now to FIG. 3, which illustrates in quarter section a left end portion of the drainage pipe section 18 depicted in schematic form in FIG. 2, the tubular outer inlet flow structure 30 that coaxially circumscribes the base pipe 26 and forms therewith the annular flow passage 32 includes, at each end of the tubular sand screen assembly 34, an annular screen connector member 38 and a tubular housing member 40.

The left end portion of the drainage pipe section depicted i FIG. 3 is a mirror image of its right end portion.

The annular screen connector member 38 is secured at it left or axially outer end to the outer side of the base pipe 26 by an annular weld 42 having a circumferential gap 42a therein which is aligned with a longitudinally extending notch 38a formed in the left or axially outer end 44 of the connector member 38. The aligned weld gap 42a and connector member end notch 38a form a passage through which the portions of the annular flow passage 32 on the left and right sides of the weld 42 communicate. The right or axially inner end of the connector member 38 is anchored to the left end of the sand screen assembly 34 by means of two annular welds 46 and 48.

To provide for precise centering of the sand screen assembly 34 relative to the base pipe 26, thus providing for 16 essentially uniform thicknesses of the portions of the passage 32 underlying the screen assembly 34 and the connector member 38, the connector member 38 is provided with a circumferentially spaced series of interiorly threaded circular openings 50 in which centering screws 52 are positioned (only one centering screw 52 being visible in FIG. 3). The inner ends of the centering screws 52 bear against the outer side of the base pipe 26 and may be loosened or tightened as necessary to provide the desired centering of the connector member 38, and thus the sand screen assembly 34, relative to the underlying base pipe 26.

A right or axially inner end portion of the tubular housing member 40 outwardly overlies the connector member 38 and is threadingiy coupled thereto at threaded section 54 which has a suitable epoxy thread sealant compound applied thereto. A series of internally. threaded circular openings 56 are formed in a left or axially outer end portion of the housing member 40. Centering screws 58 (only one of which is visible in FIG. 3) are threaded into the openings 56, bear against the outer side of the base pipe 26, and are used to center a left end portion of the housing member 40 relative to the base pipe 26 to thereby generally equalize the radial thickness of the portion of the annular passage 32 to the left of the annular weld 42.

Referring now to FIGS. 3, 7 and 8, the labyrinth structure 36 has an annular flow control member in the form of a hollow tubular metal body portion 60 with inner and outer side surfaces 62 and 64, an open left end 66, and an open right end 68. Body portion 60, as can best be seen in FIG. 7, tapers slightly in a leftward and radially inward direction. As best illustrated in FIG. 3, the labyrinth structure 36 coaxially circumscribes the base pipe 26 and is interposed in the annular flow passage 32 between the connector member 38 and the base pipe fluid inlet slots 28. A well flow control passage includes a labyrinth flow passage portion 69 (see FIG. 8) which is suitably recessed into the outer side surface 64 and has a single fluid inlet opening 70 extending inwardly through the right labyrinth structure body end 68. The labyrinth inlet opening 70 is circumferentially aligned with the weld gap 42a and the 17 connector member notch 38a (see FIG. 3), As viewed in FIG. 8, from its inlet opening 70 the labyrinth flow passage 69 has a downwardly serpentined configuration including a spaced series of axially extending passage portions 72 (representatively ten in number) interconnected at alternating end portions thereof by shorter circumferentially extending passage portions 74 as illustrated. Alternating ones of the passage portions 72 have axially extending outlet portions 76 that pass outwardly through the left end surface 66 of the labyrinth structure 36.

For sealing purposes later described herein, a thin coating of an elastomeric material 78, prefe-rably rubber, is suitably adhered to the outer side surface 64 of the labyrinth structure body 60 (see FIG. 7). The rubber coating 78 does not extend into the labyrinth flow passage 69 and preferably has a thickness within the range of from about 0.008 inches (0.2mm) to about 0.012 inches (0.3mm). Also for sealing purposes later described herein, a thin coating of sealant primer material 80 is applied 1 18 to the inner side surface 62 of the labyrinth structure body 60. Preferably, the primer material 80 is an epoxy xylene material, such as that used in aerospace fuel tank applications, and has a thickness within the range of from about 0.001 inches (0.025mm) to about 0.003 inches (0. 076mm), Turning now to FIGS. 3 and 4, an annular exterior side surface primer recess 82 is formed on the base pipe 26. The primer recess 82 is in an aligned, facing relationship with the inner side surface 62 of the labyrinth structure 36 and has opposite ends 82a. A similar annular exterior side surface primer recess 84 is formed in the base pipe 26 in a facing relationship with a left or axially outer end portion of the housing member 40 in which the openings 56 and an annular interior side surface recess 86 are disposed. As best illustrated in FIG. 3, a circumferentially spaced series of small circular holes 88 extend radially inwardly through the tubular housing member 40 into the annular recess 86. The annular recess 86 opens outwardly through the left or axially outer end of the housing member 40 via a small annular gap 90 between the interior side surface of the left end of the housing member 40 and a left end portion of the primer recess 84. As best illustrated in FIG. 4, a thin layer of the previously described

primer material 80 is suitably adhered to the inner surface of the annular recess 82 and is also carried short distances past the recess ends 82a along the outer side surface of the base pipe 26. A thin layer of the primer material 80 is also suitably adhered to the inner surface of j -19the annular recess 84 (see FIG. 3) as well as to the opposing annular interior surface portion of the housing member 40.

A circumferentially spaced series of internally threaded circular holes 92 (representatively ten in number) are formed in the tubular housing member 40 and, with the labyrinth structure 36 operatively positioned within the housing member 40, are circumferentially aligned with the labyrinth passage outlet portions 76 (see FIG. 8). Prior to the installation of the housing member 40 on the base pipe 26, and the threaded connection of the housing member 40 to the screen connector 38, the labyrinth structure 36 is leftwardly inserted into the open right end of the housing member 40. The proper insertion depth of the labyrinth structure 36 is automatically provided for by means of a slight interior surface tapering in a right longitudinal section of the housing member 40 which corresponds to the previously described exterior tapering of the labyrinth structure 36. The labyrinth structure 36 is diametrically sized relative to the housing member 40 in a manner such that upon insertion of the labyrinth structure 36 into the housing member 40 the rubber layer 78 on the exterior side surface of the labyrinth structure 36 is slightly compressed, thereby forming an essentially fluid tight seal between the outer side surface 64 of the labyrinth structure and the facing interior side surface portion of the surrounding housing member 40.

While the labyrinth structure 36 is being axially pressed into the housing member 40 a circumferentially spaced plurality of small circular openings 93 (only one of which is shown in FIG. 3) are drilled inwardly through the housing member 40 and a b y -- i n -Lh, s rlic ture and D--rt-: allv J nto the -.nse----ed JO retentior pins 93a are forced in--o holes 93a to thereby -a--n ine p-ressed-in -6 n ax-all re laby--- -n structure 3 place the -1 1 1 housing member 4. 0 as lustrated in E!-. 3.

The proper relative circumferential- orientation of the laby--Int., sructure 36 and -the housLng member 40, in Y,-.nJ-h the labyrinth passage inlet 70 (see FIG. 8) is circumferentially aligned w---h the weld cap 42a and the sCreen connector member no.--c 38a, is ach-'neved using aliarment 111nes 94,96 resDectively scribed on adjacent exterior surface portions of the housing member 40 and the screen connector member 38. As the labyrinth structure 36 is being inserted into the housing member 40, labyrinth structure -'s -otationall-ly oriented relative to such that ihe i the the housing member in a manner nner end of an alignment stud (norshown) temporarily threaded into one of the circular openings 92, for example the opening 92a depicted in FIG. 3, enters the labyrinth passage portion 72,76 having the inlet opening 70 at one end thereof (i.e., the top passage portion 72,76 as viewed in FIG. 8).

The use of -the alignment stud in -h-s manner installed labyrinth structure 36 in a positions the predetermined circumferential relationship with the alignment mark 9 on the housing member 40. Alignment mark 94, in turn, is related to the alignment mark 96 on the screen connector member 38 in a manner such that, when the mark 94 is circumferentially aligned with the mark 96 as the housing member 40 is being threaded onto the screen connector member 38 the labyrinth inlet opening 70 (see FIG. 8) is circumferentially aligned wi i the weld gap 42a and the connector member -21end notch 38a (see FIG. 3) With reference now to PIGS. 3, 4 and 8, a circumferentially spaced series of, representatively, ten small circular injection holes 98 are formed in the housing member 40 and are positioned around its circumference to overlie outer side surface areas 100 of the installed labyrinth structure 36 disposed between adjacent pairs of the labyrinth passage portions 72 as shown in FIG. 8. After the labyrinth structu-re 36 is installed between the base pipe 26 and the housing member 40 as previously described herein, the injection holes 98 are used as guides to drill underlying holes 98a radially inwardly through the labyrinth structure wall portions 100.

Subsequent to the formation of the holes 98a, predetermined quantities of an adhesive type resilient sealant material 102 (see FIG. 4) are injected inwardly through the aligned hole pairs 98,98a into the annular space 104 between the facing primed labyrinth structure and recess surfaces 62 and 82. Preferably, the sealant material 102 is a chemically curing polythioether polymer-based sealant material of the type used, for example, to seal aerospace industry fuel tank joints.

The injected sealant material 102 forms a resilient annular seal between the inner side surface of the labyrinth s-Lructure 36 and the base pipe 26 which it coaxially circumscribes. The quantities of sealant 102 injected inwardly predetermined through the hole pairs 98,98a are selected in a manner such that the opposite ends of this resulting annular seal (such as the seal end 102a in FIG. 4) are spaced axially inwardly from the opposite ends 82a of the primer side surface recess 82.

T n acid on --o the annul a- 102 associated tIne Itabyri nth ends of the draInace cloe section inner and outer s e a 1 s '1 8 a n d -6 at the opposl. e 1-8, the drainage pipe section 18 has, at the ax--la--],,i outer ends o-: -Its -nwo tubular members 40 a special1; designed nose seal s-_ructure. The nose seal structure shown at L-he lef-i_ or ax-la---',y outer end of the housing member 40 in!G. 3 includes an annular elastomeric lip seal 106 (see alsc FIG. 12) havirg a gen.eral--v C-s'.haped crosssection and beinc d-isDosed in an annuLar inl- e-rior side surface recess 108 in the housing member 40. As illustrated, the lip 6 is radialiv comDres-ed between the outer side surface of the base pipe 26 and the inner side surface of recess 108. The nose seall elastomeric 0- r-ing seal side surface srructure member also includes a redundant 1-10 positioned between the lip seal 106 and the interior recess 86 arid compressed between the interor side surface of -he housirQ member O and the outer of the base ripe 26. TI-)E _final portion of: the redundant nose seal structure is positioned just to the left of the 0-r--1ra seal 1-10 and consists o a cTuantity of the previously described adhesive sealan-.- 102 injected inwardly through th.e circu'Lar ho-"'es 88 and fillino the annula-- interior recess 86 and the le-ftwardly adjacent annular gap 90 between the left end of the housing member 40 and the facing outer side surface portion o_ the base nipe 26.

The effect-ive lenath of the -iabyrj.n-h flow passage 69 (see EIG. 8), and thus the total resistance to pressurized well f'Luid flow therethrouQh, may be selectively varied, using specially designed plug structures 112:'see FT-S. 4-5C and 8) and 114 (see FIGS. 8-11) that embody principles of the present invention. In a manner subsequently described herein, the plug structures 112 are installed in all but a selected one of the labyrinth outlet passage portions 76 and serve to sealingly block such outlet passage portions and their overlying circular housing member plug holes 92. A plug structure 114 is installed in the remaining plug hole 92 and sealingly blocks it, but does not block the underlying labyrinth outlet passage portion 76a.

Accordingly, pressurized well fluid entering the labyrinth inlet 70 (see FIG. 8) flows through the labvrinth passage 69 until it reaches and is leftwardly discharged through the unblocked passage. outlet portion 76a with the plug structure 114 in its associated housing member plug hole 92. As representatively shown in FIG. 8, the non-outlet blocking plug structure 114 is installed in the third outlet passage portion 76 from the bottom. Thus, the incoming pressurized well fluid F follows the dashed line flow path indicated in FIG. 8, exiting the labyrinth structure 36 through passage outlet portion 76a. By simply switching positions of the plug structure 114 and one of the plug structures 112 the actual length of the labyrinth passage 69 through which the well fluid F flows may be selectively shortened or lengthened to correspondingly reduce or increase the fluid pressure drop across the labyrinth structure 36.

Turning now to FIGS. 4-6, each plug structure 112 includes a rigid portion 116 and an elastomeric sealing portion 118.

Rigid portion 116 is a metal, exteriorly threaded disc which threads -in:o --he associa--eo' housing Qor--i3n plug hole 92 the oi-, tsJcie of ihe -,ousJng por--.ior,, 0. E'astomer-ic sealing portion 118 has an elongated rectangular base portion 120 Si 7ed 'abyrinth to be comc-le.men7ari,v recelved in -,,-S associated outlet- passage iDortion 76, and a cenerally disc-shaped top portion 122 having a domed upper side surface 124. As 6 illustrated;n FICS. 0, each housing member circular plug or)en-,no 92 has a d-iar..e--er somewha-- larger than the width of the Dassage Dor-ion --hereby exposing an underly-ing cutlet 76, opposite pair of ledge sections 126 of the 'Labyrinth structure 36 at the bo---orri end of the hole Each resilient secr-ion 118 is base portion 120 with the 012.

n the associated top portion 122 of the resi upwardly into the overIving best illust-rated in ' _I 'D.

threadina v tightened Into 92 until the disc 116 compresses the elastomer-J--- Tlug structure portion 118 between the plug 116 and the inner side surface of the outlet passage Do-rtion 76. This compression of the elastomeri c Porti. on 118 causes the base portion l20 to be deformed into tight, sealing engagement with installed by positioning ii- out-let passage portion 76, lient. section - li8 extending portion hole 92- Next, as 116 is the associated housing member hole housing 4Ine r -- 9 i d p lu g di sc the bottom and opposite side surfaces of the passage portion 76 and the inner side surface o_ the housing member 40, thereby sealinaly blocking offE the outlet passage Portion 76. The comp-ression of the elastomeric oortion 118 also causes the top portion 122 to be deformed into sea-', surface of th.e Inole 92 ng engagement with the interior side Further seal-Ing of the hole 92 is L -25preferably effected using a suitable epoxy-type -thread sealant on the disc 116.

Turning now to FIGS. 9-11, the plug structure 114 i an externally threaded metal disc 128 (similar to the previously described discs 116) threadable into the housing member hole 92 overlying the labyrinth outlet passage portion 76a (see FIG. 9), and a sealing structure 130 having a metal, disc-shaped base portion 132 sized to be inserted inwardly through the hole 92 and rest on the underlying ledges 126 (see FIG. 6), and a slightly larger diameter disc-shaped elastomeric upper side portion 134 having a domed top side surface 136.

With the sealing structure operatively placed within the housing member hole 92 that overlies the outlet passage portion 76a, the disc 128 is threaded into the hole 92 and firmly tightened against the underlying sealing structure 130. This compresses the elastomeric portion 134 between the disc 128 and the disc 132 and outwardly deforms the elastomeric portion 134 into tight sealing engagement with the interior side surface of the hole 92.

As is best illustrated in FIG. 9, the installed plug structure 114, while it tightly seals off. its housing member hole 92 it does not extend downwardly into or block any portion of the underlying labyrinth outlet passage portion 76a.

Accordingly, the well fluid traversing the labyrinth passage 69 c-an freely exit it via the outlet passage portion 76a. The sealing of the hole 92 by the plug structure 114 is augmented by using an epoxy-type thread sealant on the disc 128.

-2 E. - 1n. e varlous specially oesigneo sea:inc s t r j c tu. -- e s -ra-ea crainage pipe sec ser-,-e incorpor-ared in the -t-on _; ' to advantageously ass,--re that all of the well fluid w'-ich enters the o-fl the base pipe 26 via its various fluid i-let ooe,-ings 28 o-oeative.2y traverses t-he sand screen assembly 3J as well as tne selected -'Luid flow length of the labyrinth passage 36 and does not undesirably bypass either the sCreen s t -- u c -- u r e or any,Dor---,on of t h, e selected abvr'n...

passage length.

S-oecifil caliv, as described above, the structures at the ax--a-'-LY outer ends of meir,be---s O Drevent any apDreclable amount fluid from flowing inwardly beneath housing members into the passage undesirably bypass-ing the labyrinth into the -Ln,7erior of the base p'pe redundan-nose seal the tubular housing of pressurized outer ends o' 32 (see FIG. 3) well the an d structures 36 on its way 26 -through it-S sidewal 1 openings 28. Plug struclLures 114 serve to preven-- any appreciable amount of oressurized well --Fluid -from enterinG the interior of the housing members 40, via the plug holes 92, and undesirablv flowino through only a cori:--;on of the intended labyrinth flow passage length.

-1he sealant materlals 78 and!'02 respectively disposed on the outer and inner side surfaces of the labyrinth structure 36 (see F7GS. 4 and 7) assures that no appreciable portion of the pressurized well fluid approaching the llaby-rinth inlet -70 in the annular passage 32 axially traverses the labyrinth structure 36 without passing through the entire selected length of its labyrinth passage 69. BY virtue of this highly -27efficient overall sealing apparatus, the fluid flow regulation accuracy of each of the drainage pipe sections is substantially increased, thereby permitting the fluid inflow rates thereof to be more accurately equalized to correspondingly provide for heightened well fluid production rates.

It will be appreciated that the invention may be modified within the scope of the appended claims.

28

Claims (11)

CLAIMS:

1. Production fluid drainage apparatus for a subterranean well, comprising. a base pipe having a sidewall inlet opening therein; a tubular structure coaxially circumscribing the base pipe and forming therewith an annular fluid flow passage communicating with the interior of the base pipe through the sidewall inlet opening, the tubular structure having a fluid filtering section axially offset from the sidewall inlet opening and through which well fluid may flow into the annular fluid flow passage, and an axially outer end portion forming between itself and the base pipe an annular gap disposed axially outwardly of the base pipe sidewall inlet opening and through which the annular fluid flow passage outwardly opens. an adjustable fluid flow control structure operative to selectively vary well fluid inflow between the fluid filtering section and the base pipe and including a flow control member coaxially interposed in the fluid flow passage between the sidewall inlet opening and the fluid filtering section; and seal apparatus disposed axially outwardly of the base pipe sidewall opening and being operative to essentially prevent pressurized well fluid from entering the annular fluid flow passage through the annular gap, the seal apparatus including an annular interior side surface recess disposed axially inwardly of the annular gap and defining a radial enlargement thereof, and a quantity of an adhesive type resilient sealant material filling the interior side surface recess and extending therefrom into the annular gap.

2. Apparatus according to claim 1, wherein the adhesive type resilient sealant material is a chemically curing polythioether polymer-based sealant material.

3. Apparatus according to claim 1 or 2, wherein the base pipe has an annular outer side surface depression facing the annular gap and the annular side surface recess, and the adhesive type resilient sealant material extends into the 29 outer side surface depression.

4. Apparatus according to claim 3, wherein the surface of the annular depression and an opposing annular interior side surface portion of the tubular structure have a primer material thereon.

5. epoxy xylene material.

Apparatus according to claim 4, wherein the primer material is an

6. Apparatus according to any one of claims 1 to 4, further comprising adjustable apparatus for radially centering the base pipe and the tubular structure relative to one another.

7. Apparatus according to claim 6, further comprising a circumferentially spaced series of internally threaded sidewail openings formed in the axially outer end portion of the tubular structure, and a series of adjustment members threadingly received in the internally threaded sidewall openings and bearing against the base pipe.

8. Apparatus according to any one of claims 1 to 7, wherein the seal apparatus further includes an annular interior side surface groove formed in the axially outer end portion of the tubular structure axially inwardly of the annular interior side surface recess, and an annular resilient lip seal member having a generally C-shaped cross-section, the lip seal member being received in the side surface groove and being compressed between the tubular structure and the base pipe.

9. Apparatus according to claim 8, wherein the seal apparatus further includes an annular resilient 0-ring seal circumscribing the base pipe between the annular interior side surface recess and the lip seal member and being compressed between the tubular structure and the base pipe.

10. A method of constructing a drainage pipe section for a subterranean well, the method comprising the steps of coaxially positioning a tubular structure around a base pipe having a sidewall fluid inlet opening therein to form therebetween an annular passage that communicates with the interior of the base pipe through its sidewall fluid inlet opening, the positioned tubular structure having an axially outer end portion disposed axially outwardly of the sidewall fluid inlet opening and forming an annular gap between itself and a facing portion of the base pipe; coaxially positioning an annual flow control member in the annular passage in an axially inwardly offset relationship with the sidewall fluid inlet opening; and forming an essentially fluid tight seal between the axially outer end portion of the tubular structure and the facing portion of the base pipe by (1) forming in the axially outer end portion of the tubular structure an annular interior side surface recess which is positioned axially inwardly of and defines a radial enlargement of the annular gap, (2) forming an injection opening in the tubular structure that extends into the annual interior side surface recess, and (3) forcing an adhesive type sealant material inwardly through the injection opening in a manner causing the sealant material to fill the annular interior side surface recess and flow into and fill at least a portion of the annular gap.

11. A method according to claim 10, wherein the forming step is performed using a chemically curing polythioether polymer-based sealant material.