U.S. patent application number 10/669079 was filed with the patent office on 2005-03-24 for alternate path gravel packing with enclosed shunt tubes.
Invention is credited to Gunneroed, Terje, Vorkinn, Paul, Ward, Stephen L..
Application Number | 20050061501 10/669079 |
Document ID | / |
Family ID | 34313654 |
Filed Date | 2005-03-24 |
United States Patent
Application |
20050061501 |
Kind Code |
A1 |
Ward, Stephen L. ; et
al. |
March 24, 2005 |
Alternate path gravel packing with enclosed shunt tubes
Abstract
Apparatus for gravel packing a wellbore interval with enclosed
alternate flowpaths (i.e. conduits) that can provide a good
distribution of gravel over the entire completion interval. The
alternate flowpaths for the slurry are positioned in the annulus
formed by the base pipe and the external surface of the screen, and
connected to corresponding exit nozzle chambers positioned at
different levels on the screen, and therefore do not significantly
increase the overall effective outside diameter of the screen.
Inventors: |
Ward, Stephen L.; (Cypress,
TX) ; Gunneroed, Terje; (The Woodlands, TX) ;
Vorkinn, Paul; (Lillehammer, NO) |
Correspondence
Address: |
David M. Ostfeld
Chamberlain, Hrdlicka, White, Williams & Martin
Suite 1400
1200 Smith Street
Houston
TX
77002
US
|
Family ID: |
34313654 |
Appl. No.: |
10/669079 |
Filed: |
September 23, 2003 |
Current U.S.
Class: |
166/278 ;
166/227 |
Current CPC
Class: |
E21B 43/045
20130101 |
Class at
Publication: |
166/278 ;
166/227 |
International
Class: |
E21B 043/08 |
Claims
What is claimed:
1. A well screen comprising: a base pipe having openings through
the wall thereof; an outer surface having a top and having a
section mounted over said base pipe, some of said surface of said
section being permeable to fluids and abating the flow of
particulate material, said outer surface having standoff from said
base pipe, to form an annulus between the said base pipe and said
outer surface; at least one section of exit nozzle chambers, said
section placed over said base pipe and adjacent to said permeable
outer surface section; at least one shunt tube positioned inside
said annulus and secured to the inside of said outer surface and
extending axially along said base pipe adjacent to said permeable
section of said outer surface; said section of exit nozzle chambers
secured to said outer surface, said nozzle chamber section having
multiple exit ports circumferentially spaced around said nozzle
chamber section, said exit nozzle chambers being connected to said
shunt tube for communicating with the outside of said outer surface
of said screen; an outer member having side openings and mounted on
said top of said outer surface, and forming an annulus between said
outer member and said base pipe with openings through the exterior
of the sides of said outer member, permitting fluid flow to said
annulus from the exterior to said outer member.
2. The well screen of claim 1, wherein there are several permeable
sections of said outer surface.
3. The well screen of claim 2, wherein there are further included
longitudinal support rods secured to the inside of said outer
surface, thereby causing said outer surface to stand off from said
base pipe.
4. The well screen of claim 3, wherein said support rods are welded
to the inside of said outer surface.
5. The well screen of claim 4, wherein said shunt tube is
interspersed with said longitudinal support rods.
6. The well screen of claim 5, wherein said shunt tube is welded to
the inside of said outer surface.
7. The well screen of claim 3, wherein said outer surface includes
multiple sections of a wire wrapped around said shunt tube and said
longitudinal support rods, each wrap of said wire being spaced from
the adjacent wraps to create openings between said wraps of
wire.
8. The well screen of claim 2, wherein said section of exit nozzle
chambers is placed over said base pipe and alternates with sections
of said outer surface.
9. The well screen of claim 1, wherein said exit ports of nozzle
inserts includes material used for erosion abatement.
10. The well screen of claim 2 where there is included: a multiple
number of said shunt tubes radially spaced around said base pipe
within said annulus and extending along said base pipe in said
permeable sections of said outer surface and connected to said exit
nozzle chamber sections of said outer surface, thereby at least one
flow path is established.
11. A well screen for use with fluid in slurry in a flow stream,
comprising: a plurality of joints, each of said joints having a
base pipe having openings through the wall thereof; an outer
surface having a top and having a section mounted over said base
pipe, some of said surface of said section being permeable to
fluids and abating the flow of particulate material, said outer
surface having standoff from said base pipe, to form an annulus
between the said base pipe and said outer surface; at least one
section of exit nozzle chambers, said section placed over said base
pipe and adjacent to said permeable outer surface section; at least
one shunt tube positioned inside said annulus and secured to the
inside of said outer surface and extending axially along said base
pipe adjacent to said permeable section of said outer surface; said
section of exit nozzle chambers secured to said outer surface, said
nozzle chamber section having multiple exit ports circumferentially
spaced around said nozzle chamber section, said exit nozzle
chambers being connected to said shunt tube for communicating with
the outside of said outer surface of said screen; a coupling
joining adjacent ones of said joints together forming a common
manifold area, whereby said coupling permits said at least one
shunt tube in one each of said joints being in fluid connection
which is connected to said common manifold area and thereby in
communication with said exit nozzle chambers and at least one shunt
tube of the adjoining joints of said joint; an outer member having
side openings and mounted on said top of said outer surface, and
forming annulus in the upper most joint of said joints between said
outer member and said base pipe for joining adjacent ones of said
joints and top of said outer surface with openings through the
exterior of the sides of said outer member, permitting fluid flow
to said annulus from the exterior to said outer member.
12. The well screen of claim 11 where said mechanism joining said
joints includes: a fluid means for fluid in slurry to return to the
flow stream in the said shunt tubes.
13. The well screen of claim 12 wherein said fluid means includes a
box end at one end of said base pipe, said box end having threads
for attachment to an adjacent one of said plurality of joints; an
external circumferential groove above said threads; and a slotted
plate covering said external circumferential groove.
14. The well screen of claim 11 where said mechanism includes
connection means for joining adjacent ones of said joints, and the
flow stream is in said base pipe and further including: a fluid
means for the fluid in slurry to return to the flow stream in said
base pipe; a slotted external concentric pipe positioned between
said exit nozzle chamber that is the highest mounted and said
threaded box, said slotted external concentric pipe forming an
annulus with said inner concentric pipe and said threaded box and
having a bored channel therein, said bored channel being in fluid
connection with said annulus and in further fluid communication
with the flow stream in said base pipe.
15. The well screen of claim 11 where there are a multiple number
of said shunt tubes radially spaced around said base pipe within
said annulus and extending along said base pipe in said permeable
section of said outer surface and connected to said exit nozzle
chamber sections of said outer surface.
16. A method for placement of gravel slurry for gravel packing an
interval of a wellbore in the presence of a block by a sand bridge
or void formed in a well annulus before the placement of the gravel
slurry in the gravel packing is complete, the well annulus being
formed between a tool, having a screen, with exit nozzle chambers
placed at different points along the screen, inside the wellbore,
which screen at least partially surrounds a base pipe of the tool
forming a tube annulus, comprising the steps of: A. providing
conduits and the arrangement of conduits positioned between the
base pipe and the screen in the tube annulus and connected to the
exit nozzle chambers; B. filling the well annulus with gravel
slurry until the well annulus is blocked; C. after step B, flowing
the gravel slurry into the conduits in the tube annulus past the
well annulus block; D. causing the gravel slurry flow of step C to
flow from the tube annulus through said exit nozzle chambers to the
well annulus.
17. The method of claim 16 wherein the conduits are unperforated
flow conduits.
18. The method of claim 16 wherein the conduits are alternate flow
paths.
19. The method of claim 16 wherein the conduits are shunt
tubes.
20. The method of claim 16 wherein the conduits are round
conduits.
21. The method of claim 16 wherein the alternate flow paths are
spaced radially around the base pipe within the tube annulus.
22. The method of claim 16 wherein the gravel slurry is introduced
interior to the tool.
23. The method of claim 16 wherein the well bore is sealed in its
upper end by the tool preventing the flow of gravel slurry upward
into the well annulus.
24. The method of claim 16 wherein the gravel slurry flows through
the interior of the tool and through a crossover tool to flow into
the well annulus.
25. The method of claim 16 wherein the gravel slurry flows from the
annulus through the screen to the shunt tubes and returns through
the interior of the tool.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Technical Field
[0002] The present invention relates to the gravel packing of wells
and in more particular relates to an apparatus for delivering a
particulate-laden fluid and providing a distribution of the fluid
at different levels within the wellbore annulus being packed.
[0003] 2. Background
[0004] In producing hydrocarbons or the like from loosely or
unconsolidated and/or fractured subterranean formations, it is not
uncommon to produce large volumes of particulate matter (e.g. sand)
in conjunction with the formation fluids. As is known in the art,
these particles routinely cause a variety of problems that result
in added expense and increased downtime. Accordingly, it is
extremely important to control the production of these particulates
in most operations.
[0005] Probably the most common technique for controlling the
production of particulates (e.g. sand) from a well is one that is
known as "gravel packing". In a typical gravel pack completion, a
well screen is lowered into the wellbore and positioned across the
interval of the well that is to be completed. Particulate material,
collectively referred to as gravel, is then pumped as a slurry down
the tubing on which the screen is suspended. The slurry exits the
tubing above the screen through a "crossover" tool or the like and
flows downward in the annulus formed between the screen and the
well casing or open hole, as the case may be.
[0006] The liquid in the slurry flows into the formation and/or the
openings in the screen that are sized to prevent the gravel from
flowing through them. This results in the gravel being bridged on
or "screened out" on the screen and in the annulus around the
screen where it collects to form the gravel pack. The gravel is
sized so that it forms a permeable mass which blocks the flow of
any particulates produced with the formation fluids.
[0007] One of the main problems with gravel packing, especially
where long horizontal or inclined intervals are to be completed, is
obtaining equal distribution of the gravel along the entire
completion interval, i.e. completely packing the annulus between
the screen and the casing in cased hole completions or between the
screen and the wellbore in open hole completions. Poor distribution
of the gravel (i.e. incomplete packing of the interval resulting in
voids/unpacked areas in the gravel pack) is often caused by the
dehydration of the gravel slurry into more permeable portions of
the formation interval that, in turn, causes the formation of
gravel "bridges" in the annulus before all of the gravel has been
placed. These bridges block further flow of the slurry through the
annulus causing insufficient placement of the gravel. Subsequently,
the portion of the screen that is not covered or packed with gravel
is thereby left exposed to erosion by the solids in the produced
fluids or gas and/or that portion of the screen is then easily
blocked or "plugged" by formation particulates (i.e. sand).
[0008] U.S. Pat. No. 4,945,991, Jones, L. G., "Method for Gravel
Packing Wells" discloses a screen with rectangular perforated shunt
tubes attached to the outside of a screen longitudinally over the
entire length of the screen. In this method, the perforated shunts
(i.e. flow conduits) extend along the length of the screen and are
in fluid communication with the gravel slurry as it enters the
annulus in the wellbore adjacent the screen.
[0009] If a sand bridge forms in the annulus formed by the screen
and the wellbore prior to placing all of the gravel, the gravel
slurry will flow through the conduits past the sand bridge(s) and
out into the annulus through the perforations spaced along the
conduits to complete the filling of the annulus above and/or below
the bridge(s). U.S. Pat. No. 5,113,935 is a further modification of
this type of well screen. In some instances, valve-like devices are
provided for the perforations in these conduits so that there is no
flow of slurry through the conduits until a bridge is actually
formed in the annulus; see also U.S. Pat. No. 5,082,052.
[0010] In many prior art, alternate path well screens, the
individual perforated conduits or shunts are shown as being
preferably carried externally on the outside surface of the screen;
see U.S. Pat. Nos. 4,945,991; 5,082,052; 5,113,935; 5,417,284; and
5,419,394. This positioning of the shunt tubes has worked in a
large number of applications, however, these externally-mounted
perforated shunts are not only exposed to possible damage during
installation but, more importantly, effectively increase the
overall diameter of the screen. The latter is extremely important
when the screen is to be run in a small diameter wellbore where
even fractions of an inch in the effective diameter of the screen
may make the screen unusable or at least difficult to install in
the well. Also, it is extremely difficult and time consuming to
connect respective shunt tubes attached to the outside of the
screen to shunt tubes attached to the outside of the following
screen in the course of assembling the screen and lowering it into
the wellbore.
[0011] In order to keep the effective diameter of a screen as small
as possible, external perforated shunt tubes are typically formed
from "flat" rectangular tubing even though it is well recognized
that it is easier and substantially less expensive to manufacture a
round tube and that a round tube has a substantially greater and
more uniform burst strength than does a comparable rectangular
tube.
[0012] An additional disadvantage to mounting the shunt tubes
externally, whether they are round or rectangular, is that the
shunt tubes are thereby exposed to damage during assembly and
installation of the screen. If the shunt tube is crimped during
installation or bursts under pressure during operation, it becomes
ineffective in delivering the gravel to all levels of the
completion interval and may result in the incomplete packing of the
interval. One proposal for protecting these shunt tubes is to place
them inside the outer surface of the screen; see U.S. Pat. Nos.
5,476,143 and 5,515,915. However, because these prior art,
alternate path well screens incorporate the perforated shunts and
require that holes be drilled in the wire wound portions of the
screen and/or the shunt tubes, some additional form of seal between
the drilled hole in the wire and shunt tube is needed to prevent
slurry flow and possible erosion in the internal surface of the
screen annulus formed with the base pipe. This substantially
increases the cost of the screen without substantially decreasing
the over all diameter of the screen. In addition, the connections
between the joints of screen in these prior art well screens,
require either a union type connection, which is understood by
those skilled in the art, that is incapable of withstanding torque
being applied, a timed connection to align all of the shunt tubes
from screen joint to screen joint, a jumper shunt tube between
screen joints or a cylindrical cover plate over the connection
between screen joints that is either welded to the base pipe or
held in place by metal bands. All of these alternatives are
expensive, time consuming and/or very difficult to handle on the
rig floor while making up and installing the well screens.
[0013] Other downhole well tools have been proposed for fracturing
a formation (U.S. Pat. No. 5,161,618) or treating a formation (U.S.
Pat. No. 5,161,613) whereby individual conduits or shunt tubes are
positioned internally within a housing or the like to deliver a
particulate treating or fracturing fluid to selective levels within
the wellbore. However, the outlets through the housing of these
tools remain open after the particular operation is completed which
would be detrimental in gravel packing completions since the
produced fluids could then carry particulates back into the housing
through these openings after the gravel pack has been completed and
the well has been placed on production.
[0014] U.S. Pat. No. 5,333,688 discloses a gravel pack screen
having shunt tubes positioned within he base pipe of the screen
where they do not increase the overall diameter of the screen.
Gravel slurry carried by these shunt tubes is delivered to
different levels in the well annulus around the screen through the
spaced outlets through the housing. However, by placing the shunt
tubes within the base pipe (i.e. ultimately part of the production
flowpath), an intricate and sophisticated valve is required to each
of the outlets after the gravel packing operation is completed,
thereby adding substantially to the costs of the screen and of
installation. As well, with the shunt tubes in the production
flowpath any remedial or production data gathering work will be
inhibited by the tubes and will cause such work to be expensive or
incapable of being performed.
SUMMARY OF THE INVENTION
[0015] The present invention provides an apparatus for gravel
packing an interval of a wellbore wherein there is good
distribution of gravel over the entire completion interval even if
a sand bridge or void or the like is formed in the well annulus
before the placement of the gravel is completed. The present
apparatus is similar to that disclosed in U.S. Pat. No. 4,945,991
but includes unperforated shunt means (e.g. conduits and
arrangement of conduits) positioned within the annulus formed
between the base pipe and the outer surface of the screen that can
deliver the gravel slurry to different levels of the interval
during the gravel pack operation.
[0016] This is believed to provide a more reliable means of
deploying the apparatus in some applications (e.g. completion of
long openhole intervals) over the prior art apparatus with the
external shunts.
[0017] The present invention provides for distributing the gravel
slurry to different points of the wellbore annulus from a
multiplicity of unperforated flow conduits or shunt tubes
positioned within the annulus formed between the base pipe and the
outer surface of the screen, thereby providing the necessary
alternate flowpaths for the slurry without substantially increasing
the overall, outside diameter of the screen. The shunt tubes are
connected to exit nozzle chambers placed at different points along
the screen to allow for dispersion of the slurry around the
complete circumference of the screen and along the entire length of
the screen.
[0018] Also, by placing the unperforated shunt tubes within the
annulus formed between the base pipe and the outer surface of the
screen, a) the shunt is protected from damage and abuse during
handling and installation of the gravel pack screen; b) a more
desirable "round" tube can be used to form the shunt tubes thereby
providing shunts with greater burst strength and less chance of
failure during operation than most external shunts; c) the ability
is present to increase the number of shunts and thereby provide
more flow area for delivery of the gravel slurry along the
completion interval; and d) an externally smooth outside diameter
on the outer surface of the screen is permitted to simplify the
installation of the well screen
[0019] More specifically, the well screen of the present invention
is comprised of a base pipe that has multiple openings through the
wall thereof and an outer surface which is spaced from the base
pipe to form an annulus between the base pipe and the outer
surface. Typically, multiple alternate flow paths (e.g. shunt
tubes) are spaced radially around the base pipe within the annulus
and extended axially along the length of the base pipe and
connected to exit nozzle chambers at designated intervals along the
outer surface of the screen. Solid support members are interspersed
between the shunt tubes to aid in supporting and spacing the outer
surface away from the base pipe.
[0020] The outer surface of the screen is comprised of a continuous
length of wire wrapped around the radially spaced shunt tubes and
the support members and is welded at each point of contact with the
tubes and support members. Each coil of the wrap wire is spaced
slightly from the adjacent coils to form fluid passages between the
respective coils of wire. End rings are used to align the tubes and
support members and none of the tubes or support members are welded
to the base pipe. This eliminates problems associated with stress
crack corrosion due to welding dissimilar metals. Multiple exit
nozzle chambers are provided at designated intervals along the
outer surface of the screen and the shunt tubes are connected to
the exit nozzle chambers by a connector above and below. The
present well screen may consist of only one section or it may
consist of multiple sections that are connected together via a
manifolded connector.
[0021] The manifolded connector allows for ease of make up of the
joints of screen as it is run in the wellbore. The connector has
multiple holes bored longitudinally through the box and pin ends.
As the pin end is made up into an adjacent box end, there is a
manifold area or space (e.g. common area) above the make up point
that combines the flow from all of the shunt tubes. No other tie-in
of the shunt tubes or additional cylindrical cover plates are
required; therefore the make up is similar to conventional pipe or
tubing make up as performed in daily operations. The top of the
manifold area is sealed with a seal ring above and below. A slotted
plate can be positioned on the box end of the connector to allow
for return to the surface of the solids free carrier fluid to aid
dehydration across the manifolded connector. No special tools or
timed connection or welding in the area of the connector are needed
or required. The joints are made up end to end without any
interruption in the flow between the joints. An additional
concentric sleeve is provided below the box end of the connector to
provide an area for hanging the screen on slips and/or latching the
rig elevators to pickup the screen joint. Slotting of the
concentric sleeve can be to provide additional area for return of
the slurry fluid to aid dehydration across the concentric sleeve
area. These areas for return of the slurry fluid help achieve an
even leak off rate across the entire well screen assembly. The top
joint of the sand screen incorporates perforations in the external
member of the concentric sleeve to provide the means for pumping
slurry into the alternate flowpaths.
[0022] In a typical gravel pack operation, the present screen is
lowered into a wellbore and a gravel slurry is pumped down through
the workstring to a cross-over tool and through a perforated packer
bore extension that diverts the slurry flow to the well annulus
surrounding the screen and the fluid returns to the surface via the
workstring and wellbore annulus. The upper end of the shunt tubes
within the screen are open to the annulus via the perforated
external member of the concentric sleeve to receive the gravel
slurry and the tubes manifolded together at the connections.
[0023] As the gravel slurry flows downward in the well annulus
around the screen, it is likely to dehydrate on the formation and
the screen as gravel is deposited around the screen to form the
gravel pack. If enough fluid is lost from the slurry before the
annulus is completely filled, a sand bridge is likely to form that
will block further flow through the well annulus. The shunt tubes
in the present well screen allow the slurry to by-pass this bridge
in the well annulus and thereby complete the gravel pack.
BRIEF DESCRIPTION OF DRAWINGS
[0024] The apparent advantages and improvements of the present
invention, as well as, actual construction and operation will be
better comprehended by referring to the drawings that are not
necessarily to scale and in which like parts are identified with
like numerals and in which:
[0025] FIG. 1 is an elevational view, partly in cut away, of the
well screen of the present invention in an operable position within
a wellbore;
[0026] FIG. 1A is an elevational view, partly in cut away, of the
well screen, having a slotted plate on the threaded box end for
leak off, of the present invention in an operable position within a
wellbore;
[0027] FIG. 2 is a partly section view of a single joint of the
well screen of the present invention as set up to run in a
wellbore;
[0028] FIG. 2A is a partly section view of a single joint of the
well screen, having a slotted plate on the threaded box end for
leak off, of the present invention as set up to run in a
wellbore;
[0029] FIG. 3 is a partly section view of a joint of the well
screen of the present invention with several cross-sections taken
along different lines of the well screen as indicated by the
letters;
[0030] FIG. 3A is a cross-sectional view of FIG. 3 taken along
section lines AA of FIG. 3;
[0031] FIG. 3B is a cross-sectional view of FIG. 3 taken along
section lines BB of FIG. 3;
[0032] FIG. 3C is a cross-sectional view of FIG. 3 taken along
section lines CC of FIG. 3;
[0033] FIG. 3D is a cross-sectional view of FIG. 3 taken along
section lines DD of FIG. 3;
[0034] FIG. 3E is a cross-sectional view of FIG. 3 taken along
section lines EE of FIG. 3;
[0035] FIG. 3.1 is a partly section view of a joint of the well
screen, having a slotted plate on the threaded box end for leak
off, of the present invention with several cross-sections taken
along different lines of the well screen as indicated by the
letters;
[0036] FIG. 3.1A is a cross-sectional view of FIG. 3.1 taken along
section lines AA of FIG. 3.1;
[0037] FIG. 3.1B is a cross-sectional view of FIG. 3.1 taken along
section lines BB of FIG. 3.1;
[0038] FIG. 3.1C is a cross-sectional view of FIG. 3.1 taken along
section lines CC of FIG. 3.1;
[0039] FIG. 3.1D is a cross-sectional view of FIG. 3.1 taken along
section lines DD of FIG. 3.1;
[0040] FIG. 3.1E is a cross-sectional view of FIG. 3.1 taken along
section lines EE of FIG. 3.1;
[0041] FIG. 4 is an enlarged sectional view, partly cut away, of
the manifolded connector end portions of two adjacent joints of the
well screen of FIG. 1;
[0042] FIG. 4A is an enlarged sectional view, partly cut away, of
the manifolded connector end portions, having a slotted plate on
the threaded box end for leak off, of two adjacent joints of the
well screen of FIG. 1A;
[0043] FIG. 5 is a side view of the entire screen assembly in place
in the wellbore and indicating the fluid flow while in the gravel
packing position;
[0044] FIG. 6 is a side view of the entire screen assembly in place
in the wellbore and indicating the fluid flow while in the gravel
packing position with a sand bridge formed in the annulus.
DESCRIPTION OF PREFERRED EMBODIMENTS
[0045] FIGS. 1 and 1A illustrate the well screen 17 of the present
invention in an operable position within the lower portion of a
producing and/or injection well 20. Well 20 has a wellbore 25 that
extends from the surface ( not shown) through an unconsolidated
and/or fractured production and/or injection formation 22. Even
though well 20 is shown as a vertical, cased well, it should be
noted that the present invention is equally applicable for use in
open-hole wells and/or completions as well as horizontal and/or
deviated (inclined ) wellbores.
[0046] As shown, wellbore 25 is cased with casing 24 and cement 23
with perforations 21 within the interval of formation 22 that is to
be gravel packed and/or fractured. Screen 17 is connected to the
lower end of a cross-over tool 31 that is connected to the surface
via a tubing or workstring (not shown) and is positioned across
formation 22 forming an annulus 18 with casing 24.
[0047] FIGS. 1-3.1 illustrate screen 17 as comprised of a
perforated base pipe 1. However, because base pipe 1 is shown as
having multiple perforations 14, it should be recognized that other
types of base pipes, e.g. slotted pipe, etc., can be used in place
of the perforated base pipe without departing from the present
invention. One or more unperforated shunt tubes 7 (two shown) are
spaced around the circumference of base pipe 1 and extend
longitudinally along the length of the base pipe 1. Unperforated
shunt tubes 7 (i.e. flow conduits) are shown as being circular in
cross-section, but it should be understood that conduits having
other cross-sections ( e.g. rectangular) can be incorporated
without departing from the present invention.
[0048] As shown in FIGS. 1 and 1A, outer surface 32 of screen 17 is
comprised of a continuous length of wrap wire 33 that, in turn, may
be shaped to provide a "keystone" profile (not shown). Solid
support rods or longitudinal rod wire 34 (three shown in FIG. 1) or
the like--which are commonly used in prior art screens of this
general type--are interspersed with and/or between shunt tubes 7 to
aid in supporting and spacing outer surface 32 (wire 33 in the
preferred embodiment) of screen 17 away from base pipe 1. Shunt
tubes 7 may be used as the only spacers between the base pipe 1 and
the wire 33 without departing from the present invention.
[0049] Wire 33 is wrapped around the radially-spaced shunt tubes 7
and the longitudinal support rods 34 (Shown in FIGS. 3E and 3. 1E)
on base pipe 1 and is normally welded at each point of contact with
the tubes and wire rods. Each circumferential wrap of wire 33 is
spaced slightly from the adjacent wraps to form passageways (e.g.
slot openings) 5 between the respective wraps of wire. The wire is
wrapped circumferentially in various lengths along the base pipe 1
and is shrink fit onto the base pipe 1 while covering the shunt
tubes 7 and longitudinal support rods 34 forming the outer surface
32. Connector rings 16 are shrink fit onto the outer surface 32 of
screen 17 and base pipe 1 to connect the outer surface 32 of screen
17 to the base pipe 1.This is basically the same process commonly
used in the manufacture of wire-wrap screens that are commercially
available, such as LINESLOT Screens, Reslink, Inc. Houston,
Tex.
[0050] As shown in FIGS. 1,1A, 2, 2A, 4 and 4A, a part of the outer
surface 32 of screen 17 incorporates multiple exit nozzle chambers
6 spaced along the length of each screen joint 17, shrink fitted
onto base pipe 1 and comprised of several nozzles 10 (FIGS. 1-4A)
that are connected to the unperforated shunt tubes 7 via connectors
9. The outer surface 32 of screen 17 is connected to the exit
nozzle chambers 6 via connector rings 16 that are shrink fitted on
to the screen 17 and exit nozzle chamber 6.
[0051] The preceding description of screen 17 indicates that it is
constructed of a perforated base pipe 1 with a wire 33 or the like
that is wrapped in closely spaced wraps to form a permeable liner,
it will also be recognized by those skilled in the art that outer
surface 32 may be formed from a slotted pipe, screen material, or
the like, as long as it is permeable to fluids and impermeable to
particulates. Accordingly, the "screen" as used throughout the
present specification and claims is meant to be generic and to
include and cover all types of those structures commonly used by
the industry in gravel pack and frac pack operations which permit
the flow of fluids through them while abating the flow of
particulates (e.g. commercially available screens, slotted or
perforated liners or pipes, screened pipes, prepacked or dual
prepacked screens and/or liners or combinations thereof) into which
shunt tubes 7 can be incorporated inside the outer surface of the
screen 17 as disclosed in the present invention.
[0052] Additionally, screen 17 may comprise of only one joint (e.g.
30 foot section) or it may comprise of a multiple number of joints
connected together. As an example, FIG. 4 illustrates a coupling 2
for joining two screen joints 2A and 2B together. Coupling 2 is
comprised of a standard threaded box 2b and a threaded pin 2a.
After the two joints have been joined and properly torqued a
manifold area 13 is formed above the threaded connection by the
extension 2d that is threaded onto box 2b. Manifold area 13 is
connected to the shunt tubes 7 from joint 2A via the channels 12
bored through exit nozzle chamber 6 above the threaded pin 2a, and
is in turn connected to the shunt tubes 7 from joint 2B via
channels 15 bored in the threaded box 2b. Incorporation of this
manifold area 13 allows for make up of the joints 2A and 2B without
having to align the shunt tubes on the adjoining joints. The bored
channels 15 in the threaded box 2a connect or align with the
concentric annulus 8 formed by the base pipe 1 and external
concentric pipe 4 that is positioned between the top exit nozzle
chamber 6 and the threaded box 2b (FIG. 4).
[0053] As known by those skilled in the art, the inability to bleed
off the fluid from the slurry across the coupling 2 may cause
insufficient dehydration of the fluid from the gravel slurry to
occur in this area and thereby an incomplete pack is performed. A
nonpreferred embodiment of the present invention may incorporate
area 3 for bleed off of the fluid from the slurry (FIGS. 1A, 2A,
3.1 and 4A). The bleed off area 3 in coupling 2 is formed by
milling a groove 2c radially around the exterior of the threaded
box 2b, then covering the groove 2c by a thin slotted cover plate
3a that is held in place by the extension 2d, made up to the
outside of threaded box 2b (FIG. 4A). Bored hole 2e connects to
bored channel 3c to allow bleed off of the fluid to the base pipe 1
(FIG. 4A). The bleed off area 3 is used when there is significant
blank area between screen areas to provide bleed off of fluid that
may be entrained in such area.
[0054] In a typical gravel pack operation, screen 17 is lowered
into wellbore 20 (FIG. 1) on workstring 32 and is positioned across
the formation 22. Ball 43 is pumped onto ball seat 42 and pressure
is applied through ports 51 as is understood by those skilled in
the art to set packer 30. A gravel slurry 56 is then pumped down
the workstring into cross-over tool 31 and out of outlet ports 31a
in crossover tool 31 through ports 50 and into annulus 18 of
wellbore 25. All of the shunt tubes 7 are manifolded together by
concentric annulus 8 that is formed by base pipe 1 and external
concentric pipe 4 to receive the gravel slurry via the wellbore
annulus 18 through the ports 4a in the external concentric pipe
4.
[0055] As the gravel slurry flows downward in annulus 18 around the
screen 17, it will likely dehydrate due to fluid loss to formation
22 and/or through screen 17. The fluid entering screen 17 will
return to the surface through holes 14 in base pipe 1, up washpipe
55, passing through check valve 44 and through pipe 31b in
cross-over tool 31 (FIGS. 5 and 6). As the fluid from gravel slurry
56 dehydrates on the screen 17 and/or the formation 22, gravel 57
carried in slurry 56 is deposited and collects in the annulus 18 to
form the gravel pack. As is known in the art, if enough fluid is
lost from slurry 56 before annulus 18 is filled, a gravel bridge 60
(FIG. 6) will form and block flow through annulus 18 and prevent
further filling below bridge 60. If this occurs while using the
present invention, gravel slurry 56 can continue to be pumped
downward into ports 4a to concentric annulus 8 and then downward
through the shunt tubes 7 and out the respective exit nozzles 10
by-passing gravel bridge 60 and completing the gravel pack.
[0056] Because many varying and different embodiments may be made
within the scope of the invention concept taught herein which may
involve many modifications in the embodiments herein detailed in
accordance with the descriptive requirements of the law, it is to
be understood that the details herein are to be interpreted as
illustrative and not in a limiting sense.
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