Note: Descriptions are shown in the official language in which they were submitted.
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METHOD AND APPARATUS FOR GRAVEL PACKING A WELL
The present invention relates to a method and apparatus for
gravel packing a well. More particularly the invention relates
to a method and apparatus for gravel packing a well wherein the
gravel slurry is delivered into different points within the
wellbore annulus from the interior of the apparatus through a
plurality of spaced outlets along the apparatus which, in turn,
are closed after the gravel has been placed.
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 material
(e.g. sand) along with the formation fluids. These particulates
routinely cause a variety of problems which result in added
expense and substantial downtime. For example, ~in most
instants, particulates in the produced fluids cause (1) severe
errosion of the well tubing and other production equipment; (2)
partial or
complete clogging of the flow from the well which requires
workover of the well; (3) caving in the formation and collapse
of the well casing; (4) extra processing of the fluids at the
surface to remove the particulates; and (5) extra cost in
disposing of the particulates once they have been separated.
Accordingly, it is extremely important to control the production
of particulates in most operations.
Probably the most popular technique used for controlling
the production of particulates (e.g. sand) from a well is one
which is known as "gravel packing". In a typical gravel pack
completion, a screen is lowered into the wellbore and positioned
adjacent the interval of the well which 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
"cross-over" or the like and flows downward in the annulus
formed between the screen and the well casing or open hole, as
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the case may be. The liquid in the slurry flows into the
formation and/or the openings in the screen which are sized to
prevent the gravel from flowing therethrough. This results in
the gravel being deposited or "screened out" 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 around the
screen which allows f low of the produced f luids therethrough and
into the screen while blocking the flow any particulates
produced with the formation fluids.
One of the major problems associated with gravel packing,
especially where long or inclined intervals are to be completed,
is the proper distribution of the gravel over the entire'
interval to be completed, i.e. completely packing the annulus
between the screen and the casing in cased wells or between the
screen and the wellbore in open hole or under-reamed
completions. Poor distribution of gravel (i.e. incomplete
packing of the interval resulting in voids in the gravel pack)
is often caused by the loss of liquid from the gravel slurry
into the more permeable portions of the formation interval
which, in turn, causes the formation of gravel (e.g.sand)
"bridges" in the annulus before all of the gravel has been
placed. These bridges block further flow of the slurry through
the annulus thereby preventing the placement of sufficient
gravel (a) below the bridge for top-to-bottom packing operations
or (b) above the bridge, for bottom-to-top packing operations.
US-A-4945991 discloses a method for gravel packing an
interval of a wellbore wherein there is good distribution of the
gravel throughout the desired interval even where sand bridges
form before all the gravel is deposited. In this method,
perforated shunts or conduits are provided along the external
surface of the screen which are in fluid communication with the
gravel slurry as it enters the annulus in the wellbore adjacent
the screen. If a sand bridge forms before all of the gravel is
placed, the slurry will flow through the conduits and out into
the annulus through the perforations in the conduits to complete
the filling of the annulus above and/or below the bridge. See
also, US-A-5113935 for a similar technique.
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In some instances, valve-like devices have been 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 US-A-5082052. In all of these prior art
apparatuses used for gravel packing, the individual conduits or
W shunts are carried externally on the screen where they are
exposed to damage, possibly severe, during the handling and
placement of the screen.
Other downhole well tools have been proposed for fracturing
a formation (US-A-5161618) or treating a formation (US-A
5161613) wherein individual conduits or shunts are positioned
internally within a housing or the like to deliver a particular
treating or fracturing fluid to selective levels within the
wellbore. However, the outlets through the housing remain open
after the particular operation is completed which would normally
prove detrimental in a gravel packing operation.
The present invention provides a method and apparatus for
gravel packing an interval of a wellbore wherein there is a good
distribution of gravel over the entire interval even if a sand
bridge or the like is formed within the interval before the
placement of the gravel is completed. Basically, the present
invention provides for distributing the gravel slurry to
different points of the wellbore annulus from an internal
passage within the apparatus where it is protected from damage
during handling and installation. The outlets through which the
gravel slurry is delivered to the wellbore annulus are then
closed after the gravel has been placed.
According to one aspect of the present invention there is
provided a method of gravel packing an interval of a wellbore,
said method comprising:
(a) positioning a gravel pack apparatus within said
wellbore adjacent said interval whereby an annulus is
formed between said apparatus and said wellbore;
(b) flowing a.gravel slurry from the surface and through
the interior of said gravel pack apparatus;
(c) distributing said gravel slurry from the interior of
said apparatus at different points within said
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annulus through~a plurality of spaced outlets along
said apparatus; and
(d) closing said outlets after said flurry is
distributed.
Advantageously the gravel slurry is flowed to said spaced
outlets through a washpipe which extends through said apparatus.
Preferably said outlets are closed when said washpipe is
removed from said apparatus.
According to another aspect of the invention there is
IO provided apparatus for gravel packing an interval of a wellbore,
said apparatus comprising:
(a) a plurality of gravel screen units connected
together, each of said screen units comprising:
(i) a gravel screen; and
(ii) a valve-outlet assembly connected to said
screen, said assembly having at least one outlet
and a valve which allows flow through said
outlet when in an open position and blocks flow
through said outlet when in a closed position;
(b) means for delivering gravel slurry through the
interior of said gravel screen units to each of said
at least one outlet in each said valve-outlet
assembly; and
(c) means for closing each said valve.
Advantageously the gravel slurry comprises a washpipe
extending substantially through all of said gravel screen units
and having a respective outlet in fluid communication with each
said outlet in each said valve-outlet assembly.
Preferably the means for closing each said valve comprises
means on each of said valves adapted to engage said washpipe
whereby said respective valves will be moved to a closed
position' as said washpipe is removed from said gravel screen
units
Desirably the apparatus further includes means for securing
each of said valves in said closed position.
In a preferred embodiment the apparatus further includes
a cross-over connected to the upper end of said gravel screen
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units, said cross-over having at least one outlet in fluid
communication with an outlet in said washpipe. Desirably a valve
is prey=ded for closing said at least one outlet in. said cross-
over when said washpipe is removed.
Preferably the washpipe comprises: an outer conduit; and
an inner conduit concentrically positioned within said outer
conduit and spaced therefrom to form an passage therebetween
which extends substantially through said gravel screen units.
Each valve-outlet assembly preferably comprises: collar
having a radial outlet therein and an annular recess on the
inner surface thereof ; and wherein said valve comprises a sleeve
valve slidably positioned within said recess and movable between
an open position and a closed position, said sleeve valve having
a radial opening therethrough which fluidly communicates with
said outlet when said valve is in said open position:
According to a further aspect of the invention there is
provided a valve-outlet assembly for use in a gravel pack
apparatus, said valve-outlet comprising:
(a) a collar adapted to be connected into said gravel
pack apparatus, said collar having a radial outlet
therein and an annular recess on the inner surface
thereof ;
(b) a sleeve valve slidably positioned within said recess
and movable between an open position and a closed
position, said sleeve valve having a radial opening
therethrough which fluidly communicates with said
outlet when said valve is in said open position; and
(c) means to secure said valve in its closed position.
Reference is now made to the accompanying drawings, in
which:
FIG. 1 is an elevational view, partly in section, of the
gravel pack apparatus of the present invention in an operable
position within a wellbore;
FIG. 2 is an enlarged perspective view, partly cut away,
of one of the gravel screen units which forms a part of the
apparatus of FIG. 1;
FIG. 3 is an elevational view, partly in section, of the
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cross-over extension and the upper portion of the wash pipe of
the gravel pack apparatus of FIG. 1;
FIG. 4A is an elevational view, partly in section, of a
portion of the sliding valve-outlet assembly of FIG 2 with the
valve in an open position; and
FIG. 4B is an elevational view of the sliding valve-outlet
assembly of FIG. 4A with the valve in a closed position.
Referring more particularly to the drawings, FIG. 1
illustrates the lower end of a producing and/or injection well
10. Well 10 has a wellbore 11 which extends from the surface
(not shown) through an unconsolidated and/or fractured
production and/or injection formation 12. While well 10 is
illustrated as a substantially vertical, open-completed well,
it should be recognized that the present invention is equally
applicable for use in cased wells and/or underreamed completions
as well as in horizontal and/or inclined wellbores.
Gravel pack apparatus 20 of the present invention is
lowered into wellbore 11 on the bottom of workstring 14 and
positioned adjacent the completion interval of formation 12 to
form annulus 13 with wellbore 1l.
Apparatus 20 may be comprised of all or some of the
following standard gravel packing components: setting tool and
cross-over assembly 21, packer 22, cross-over extension 23,
knock-out valve 24, shear-out joint 25, and the desired length
of standard, blank pipe 26. Connected to the lower end of the
blank pipe 26 are one or more gravel-screen units 30 (three
shown) which are connected together to extend subsantially
through the completion interval of the formation. Since each
of screen units 30 have the same basic construction, only one
will be described in detail.
Referring now to FIGS 2-4, each gravel-screen unit 30 is
comprised of a sliding sleeve valve-outlet assembly 31 and a
screen section 32. The term "screen" is used generically herein
and is meant to include all types of those structures commonly
used by the industry in gravel pack operations which permit flow
of fluids therethrough while blocking the flow of particulates
(e. g. commercially-available screens, slotted or perforated
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PCT/US94/00216
,liners or pipes, screened pipes, prepacked screens and/or
liners, or combinations thereof).
Sleeve valve-outlet assembly 31 is comprised of a tubular
collar 35 having one or more radially-extending slurry outlet
ports 36 through the wall thereof. Slidably mounted within an
internal recess 37 on collar 35 is valve sleeve 38 which, in
turn, has a radially-extending passage 39 therethrough which
fluidly communicates with ports 36 when the valve is in an open
position (FIG. 4A). Sliding sleeve valve 38 has appropriate O-
ring seals 40 or the like thereon to form a seal between the
outer surface of valve 39 and the inner surface of collar 35.
Annular seals 41a, 41b are fixed to and carried by valve 38 and
are positioned on either side of passage 39 to effectively form
an annular channel in fluid communication with passage 39.
Slidably mounted within recess 37 below sleeve valve 38 is
detent ring 42 which, in turn, carries an inner and outer,
spring-biased detent 43, 44, respectively, for a purpose to be
described below. While being disclosed as a separate element,
it should be understood that detent ring 42 could be made
integral with sliding valve 38 without effecting the function
of either element.
A specially constructed washpipe 50 is positioned within
workstring 14 and extends from the surface through all of the
screen units 30. As best seen in FIGS. 2 and 3, the lower end
of washpipe 50 (i.e. that portion which extends through the
screen units) is comprised of two concentric tubulars members
51, 52 which, in turn, form a longitudinally-extending passage
53 therebetween. The upper end of the centermost or inner
tubular member 51 is closed at 54 to divert upward flow through
one or more cross-over ports 55 (only one shown in FIG. 3) which
are in fluid communication with the annulus 56 formed between
washpipe 50 and pipe 57.
Small cross tubes 58 (FIGS. 2 and 4A) fluidly communicate
the outside of outer tubular member 52.with the interior of
inner tubular member 51 of the double-walled washpipe 50 to form
leak-off or cross-through ports for a purpose described below.
One or more radially-extending ports 60 (FIGS. 4A, 4B) are .
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provided through outer tubular member 52 at spaced lengths along
member 52 so that each port or set of radial ports will be
aligned to fluidly communicate passage 53 with the annular
channel formed between seals 41a and 41b on sliding valve 38.
In operation, apparatus 20 is lowered into wellbore 11 on
workstring 14 and is positioned adjacent formation 12. Packer
22 is set as will be understood by those skilled in the art.
Gravel slurry is then pumped down washpipe 50 with most of the
slurry originally exiting through passage 39 in sleeve valve 38
(FIG. 3 ) and out outlet ports 65 in cross-over extension 23.
Sleeve valve 38 in the cross-over extension is basically
identical in both construction and function as the other valves
38 described above in relation to sliding valve-outlet
assemblies 30.
As the gravel slurry flows downward in annulus 13 around
the screen units, it is likely to lose liquid to formation 12
and/or through screen 32. The liquid entering screen 32 is
returned to the surface through cross tubes 58 (FIG. 4A), inner
conduit 51, cross-over ports 55, and annulus 56 (FIG. 3). The
gravel carried by the slurry is deposited and collects in the
annulus to form the gravel pack. As is known in the art (see
US-A-4945991), if enough liquid is lost from the slurry before
the annulus is filled, a sand bridge (not shown) is likely to
form which will block flow through annulus 13 and prevent
further filling below the bridge. If this occurs while using
the present invention, the gravel slurry can continue to flow
downward through passage 53 and out respective ports 60 in outer
conduit 52 and outlets 36 in the respective collars 35.
When gravel pack apparatus 20 is run into the wellbore, all
of the valves 38 are held in an open position (FIG. 4A) by
gravity or by a shear pin or the like (not shown). When in an
open position, the radial passage 39 in a respective sleeve
valve 38 is aligned with outlet ports 36, 65 in collars 35 or
cross-over extension 23 as the case may be. Passage 39 in valve
38 communicates with the annular channel formed between annular
seals 41a, 41b on sleeve valve 38 which, in turn, communicates
with,ports 60 in outer conduit 52.
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Accordingly, slurry flowing down passage 53 between inner
and outer conduits 51, 52 will flow through ports 60, 39, and
36 and into annulus 13 at the respective location of each
sliding valve-outlet assembly 31 to complete the gravel pack.
Any fluid leaking back through a screen 32 will flow through
cross tubes 58 (FIG. 4A) into inner tube 51 to be return via
cross-over extension 23 to the surface.
When annulus 13 has been gravel packed, flow of slurry is
stopped and washpipe 50 is removed to the surface. Outwardly
biased detent 44 on ring 42 will engage shoulder 70 (FIG. 4A and
4B) as washpipe 50 moves upward and will cause detent ring 42
to be carried upward thereby moving sliding sleeve valve 38 to
a closed position (FIG. 4B) . As valve 38 reaches its closed
position, inner detent 43 will be biased outward into recess 71
to secure a respective valve in its closed position. Continued
upward movement of washpipe 50 will shear the outer detents 44
whereby washpipe 50 can be removed to the surface.
The distribution of gravel directly to the various levels
in the annulus from an internal passage in the gravel pack
apparatus is believed to provide a better distribution of gravel
throughout a completion interval which results in a better
overall gravel pack efficiency, especially where long wellbore
intervals are being completed. At the same time, the passages
used for delivering the gravel, being inside the gravel pack
apparatus, are protected from damage and abuse during handling
and installation of the gravel pack screen.
