Note: Descriptions are shown in the official language in which they were submitted.
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GRAVEL PACR W~LL COMPLETIONS
WIT~ AUGER-S~R~EN
DESCR~PTION
1. Technical Field
The present invention relates to gravel pack
well completions and in one of its preferred aspects
relates to a method and apparatus for completing a
production or injection well wherein a particulate
material (collectively called "gravel") is first
positioned or preset within the well adjacent the zone
and a fluid-permeable liner having a auger blade
10 thereon is augered into place within said preset
gravel to form a gravel pack without circulating fluid
through the liner.
2. Background Art
In completing wells having production or
15 injection zones which lie adjacent incompetent
subterranean formations (i.e.formations formed of an
unconsolidated matrix such as loose sandstone or the
like) or which lie adjacent formations which have been
hydraulically-fractured and propped, serious
20 consideration must be given to the sand control
problems which will almost certainly arise during the
operational life of the well. These problems arise
when large volumes of sand and~or other particulate
material (e.g. backflow of proppants from a
25 hydraulically-fractured formation) dislodge from the
formation and become entrained in the formation fluids
and are produced therewith into the wellbore. These
produced materials are highly detrimental to the
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operation of the well and routinely cause erosion,
plugging, etc. of the well equipment which , in turn,
leads to high maintenance costs and considerable
downtime of the well.
While many-techniques have been proposed for
controlling sand production in a well, probably the
most widely-used is one which is generically known as
~gravel packinq n . Basically, a gravel pack completion
is one wherein a fluid-permeable liner (e.g. screen,
perforated liner, slotted liner, pre-packed screens,
combinations thereof, or the like) is positioned
within the wellbore (open or cased) adjacent the
incompetent or fractured zone and is surrounded by
aggregate or particulate material (collectively called
"gravel"). As known in the art, the gravel particles
are sized to block or filter out the formation
particulates which may become entrained in the
produced fluids while the openings in the liner are
sized to block the gravel from flowing into the
liner. This two-stage filtration system is commonly
known as a "gravel pack".
There are two basic, well known techniques
for instaLling a typical gravel pack completion in a
wellbore. A first of these techniques involves
positioning the fluid-permeable liner in the wellbore
before placing the gravel around the liner to form the
gravel pack. The other technique involves placing the
gravel in the wellbore first and then driving,
rotating, or washing the liner into the gravel to form
the gravel pack. For a good discussion of these
techniques, see PETROLEUM PRODUCTION ENGINEERING, Oil
Field Development, L.C. Uren, Third Edition, McGraw-
Hill ~ook Co., N.Y., 1946, pps.575-588.
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While both of these techniques have been
widely used, both require the circulation of fluid
during installation. For example, where the liner is
positioned first in the wellbore, a slurry of gravel
and a carrier fluid may be pumped down and out through
a "cross-over" sub into the annulus formed between the
liner and the casing wall (cased hole) or the borewall
(open hole). The openings in the liner allows only
the carrier fluid to flow from the annulus into the
liner while the gravel is strained from the fluid and
is deposited within the annulus to form the gravel
pack. The gravel can also be placed ~y flowing the
gravel directly into the annulus around the liner from
the surface or through open-ended tubulars which
extend down the wellbore.
Where the gravel is placed in the wellbore
first, the liner is lowered on a workstring and is
washed or driven into place while fluid is being
pumped down the workstring and out the bottom of the
liner. This circulating fluid (i.e. jetting action)
is necessary to "fluidize" the pre-positioned or
preset gravel so that the liner can be lowered into
and through the gravel to form the gravel pack.
Unfortunately, since the fluid flows through the
workstring, the pumping must be stopped each time an
additional stand of workpipe must be added to lower
the liner further into the gravel. While the pumping
is stopped, the gravel settles and in many instances,
cannot be adequately "re-fluidized" upon the
resumption of pumping to allow any deeper placement of
the liner into the gravel.
Since both techniques require the pumping
and/or circulation of fluid under pressure during
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installation, both may experience severe fluid loss
problems, especially when used to complete zones
adjacent formations having normal or below normal
pressures or pressures which are below the hydrostatic
pressure of the completion fluids in the wellbore.
For example, in placing gravel around a preset liner,
the loss of expensive completion fluids to an
underpressured formation (i.e. formation having a
pressure less than the fluid pressure in the wellbore)
can be excessive. The use of known loss-circulation
materials in the gravel slurry is limited since such
materials severely hinder the placement of the gravel
around the liner. Where the gravel is positioned
first, the fluid losses during the high pressure
jetting required to "fluidize" the preset gravel also
can be excessive. In both cases, these fluid losses
not only result in increased costs due to the loss of
the expensive completion fluids , themselves, but also
contribute to severe formation damage in many cases
thereby reducing the productivity and/or operational
life of the completed well.
DISCLOSURE OF T~E INVENTION
The present invention provides a method and
apparatus for installing a gravel pack completion in a
zone of a wellbore which does not require the
circulation of fluids during installation of the
liner. The present invention is especially useful in
completing zones which lie adjacent normal or below
normal pressured formations. Basically, gravel is
first placed within the zone and then a well
completion tool having an auger blade thereon i~
lowered and rotated into the preset gravel without
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circulating fluid through the ~ool. Since the auger
blade mechanically displaces the gravel upward and
outward as the tool is moved into the gravel, there is
no need to flow fluid under pressure to "fluidize~ the
gr~vel as is required in previous completions of this
type.
More particularly, gravel is supplied down
the wellbore to preset the gravel in the completion
zone. This gravel may be placed by any suitable step,
e.g. flowed down a workstring which is positioned in
the wellbore, dumped into the wellbore at the surface
and allowed to fall by gravity into position, or
placed in the wellbore as a result of hydraullically-
fracturing and propping the formation). Next, a
gravel pack well completion tool assembly comprised of
a workstring and an auger-screen is lowered into the
wellbore until it contacts the top of the preset
gravel. The workstring is then rotated to "auger" the
auger-screen into the preset gravel to form the gravel
pack without circulating fluid through the a~ger-
screen. In some applications, the workstring will
function as the production tubing while in others, the
workstring will be removed and replaced with a
different string of production tubing.
The auger-screen is comprised of a body
which, in turn, is comprised of a fluid-permeable
liner having an au~er blade secured to and extendinq
along the outer periphery thereof. One embodiment of
the present invention includes a safety feature in the
event the auger-screen becomes stuck during
installation. This feature includes a val~e sub which
iQ connected to the lower end of the body and has a
check valve therein to prevent upward flow into the
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body. A tapered plug is connected to the lower end of
the valve ~ub and has at least one fluid outlet
passage. A wash pipe is connected to the workstring
and extend through the body to fluidly co~unicate
with the outlet p~ssage in the tape~ed plug so that if
the auger-screen should become stuck within the gravel
during installation, fluid can be pumped down the
workstring, wasn pipe, and out the outlet passage to
"fluidize" the gravel so that the tool can be
withdrawn. Once the auger-screen is properly
positioned within the gravel to form the gravel pack,
the workstring is released and withdrawn and is
replaced with production tubing or the like.
The present invention allows a fluid-
permeable liner to be augered into preset gravel and
placed across perforations (in a cased hole) without
pumping fluid to "wash" the liner into place. This
will s~bstantially reduce the cost of gravel packed
completions, especially in short zone situations, by
reducing hardware costs, rig time, and pumping costs
normally associated with prior art gravel pack
completions. It also will result in additional
savings and in reduced formation damage in
underpressured reservoirs.
BRIEF DESCRIPTION OF THE DRAWINGS
The actual construction, operation, and
apparent advantages of the present invention will be
better understood by referring to the drawings in
which like numeral~ identify like part~ and in which:
FIG. 1 is an elevational view, partly in
section, of a well under~oing a gravel pack completion
in accordance with the present invention:
FIG. 2 is a séctional view of a portion of
S the well of FIG. 1 which lies adjacent the ~ompletion
zone with only the preset gravel in place in the
wellbore;
FIG. 3 is a sectional view similar to that
of FIG. 2 after the gravel pack completion of the
present invention has been completely installed; and
FIG. 4 is a sectional view of the lower end
of the auger-liner of FIG. 3.
BEST KNOWN MODE FOR CARRYING OUT THE INVENTION
Referring more particularly to the drawings,
FIG. 1 illustrates the gravel pack completion of the
present invention as it is being installed in well 10
(e.g. production or injection well). Well 10 has a
completion zone ll therein which lies adjacent to a
relatively incompetent formation 12 of the type which
is likely to produce sand and/or other particulate
material with the formation fluids, e.g. hydrocarbons,
at some time during its operational life. As shown,
well lO has been cased along its length with casing 13
which ha~ been perforated to provide perforations 13a
adjacent zone 11. While the present invention is
shown and described in relation to completing a zone
in a cased, vertical wellbore, it should be understood
that the invention can also be used for carrying out
completions in open holes as well as in horizontal or
deviated wells or to prevent proppant flowback in
wells which have been hydraulically-fractured and
propped.
In installing the present gravel pack
completion in wells where the wellbore extends past
the bottom of completion zone 11, a cement plug,
bridge plug or an equivalent-type packer 15 is set in
the wellbore at the lower end of zone 11. Sufficient
gravel is then supplied down the wellbore and onto the
top of plug 15 to fill the area of the wellbore which
extends through the length of zone 11 to be completed
with preset gravel 14. "Gravel n as used herein is
intended to include all particulate and~or aggregate
materials (e.g. gravel, sand, combinations, etc.
which are used or can be used in gravel pack or
fractured completions. As known in the art, the
"gravel" particles used in a particular situation are
sized so as to block or filter out the particulates
which may be produced with the well fluids or which
are used to prop open ahydraulically-induced fractures
in the formation.
The preset gravel 14 may be introduced into
wellbore in any suitable manner, depending upon the
actual circumstances involved with a particular
completion zone 11. For example, where formation 12
is a relatively low pressured formation, gravel may be
flowed down and out of the lower end of a workstring
16 which is lowered down the well (FIG. 2) and
positioned above plug 15 or lt may be dl~mped lnto the
well at the surface and allowed to fall under the
influence of gravity. The gravel may be flowed into
the wellbore as a substantially dry mixture or as a
slurry (mixed with a carrier fluid such as polymer-
type, water-based fluid, crude oil, etc.). This type
of gravel placement does not require high pressures
thereby reducing fluid losses and/or potential damage
to the formation. Further, if the situation and
formation pressures allow, the gravel may be placed by
~tandard squeeze operations which will insure good
filling of perforations 13a with the gravel during the
placement of the preset gravel 14.
After the preset gravel 14 is in place
adjacent to zone 11, gravel pack well tool 17 is
lowered into the wellbore. As illustrated, gravel
pack well tool 17 is comprised of an auger-screen 20
which is connected onto the bottom of workst~ing 18 by
means of release sub 19. If workstring 18 is to be
used as the production tubing, release sub 19 can be
replaced with a standard connection.
In accordance with the present invention/
auger-screen 20 is comprised of a body 21 having an
auger blade 22 welded or otherwiAe secured to and
extending along the outer periphery thereof. Body 21
is comprised of a ~fluid-permeable linern, which as
used herein is meant to be generic and to include any
and all types of liners (e.g. screens, slotted pipes,
screened pipes, perforated liners, pre-packed screens
and/or liners, combinations of same, etc.) which are
used or could be used in well completions of this
general type. As will be recognized by those skilled
in the art, there are presently several known
suppliers from whom such "liners" are readily
commercially available. ~he liner may be of a
continuous length, as shown, or it may be comprised of
a plurality of segments connected by subs or ~blanksn.
sody 21, as illustrated in the drawings, is
a typical fluid-permeable liner of the type known as a
nperforated, pre-packed screen~ and is comprised of an
inner screen section 23 (FIG. 4) having an outer
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perforated pipe section 24 mounted thereon to form an
annulus 25 therebetween. Annulus 25 is filled with a
pre-packed particulate material, e.g. re-sieved Otta~a
sand. A valve sub 26 is connected to the lower end of
S body 21 and has an O-ring seat 27 adapted to receive
the lower end of wash pipe 28 which, in turn, extends
through auger screen 20 and is in fluid communication
with workstring 18 (FIG. 1). Valve sub 26 also
includes a passage 29 which is closed to upward flow
by check valve ~flapper valve 30). Other types of
check valves (e.g. ball valves, rupture disks, etc.)
can be used in place of flapper 30 to allow downward
flow through passage 29 while preventing upward
flow. Tapered nose plug 31 having fluid outlet
passages 32 therein is connected to the lower end of
sub 26.
Auger blade 22 has basically the same
configuration as known earth augers in that it is a
continuous flighting which extends helically around
the periphery of body 21 and is secured thereto by any
appropriate means, e.g. welding. The blade extends
sufficiently along the length of auger-screen 20 to
insure that the auger-screen 20 will be properly
positioned within the preset gravel 14 to form the
desired gravel pack completion. If auger screen 20 is
compri~ed of segments and blanks or if blank tubular
sections above auger-screen 20 are also to be position
within gravel 14, auger blade 22 may also extend about
the periphery of such blanks.
Again, as shown in FIG. 1, preset gravel 14
is placed adjacent completion zone 11 as described
above. Well tool 17 is lowered on workstring 18 until
it contacts the top of preset gravel 14. Workstring
18 is then rotated at the surface by a rotary table,
power sub, or the like (none shown) to rotate auger-
screen ~0 and ~auger" it downward into preset gravel
14. Since the gravel being displaced by the auger-
scree~ 20 as it moves downward is mechanically moved
upward and outward along rotating auger blade 22,
there is no need to "fluidized" the preset gravel 14
by circulating fluid as was necessary in previous
gravel pack completions of this type. This is
extremely important, especially where the completion
zone is adjacent a normal or underpressured formation
in order to prevent substantial fluid losses and/or
severe formation damage during installation of the
gravel pack. Further, as the gravel is moved upward
by auger blade 22, some of this gravel is likely to be
forced into perforations 13a in casing 11 thereby
improving the overall efficiency of the gravel pack
14.
If auger-screen 20 becomes stuck in preset
gravel 14 before it has reached its desired position,
fluid can be flowed down workstring 18, wash pipe 28,
and out passages 32 in nose plug 32 to "fluidize" the
gravel whereby auger-screen can be lowered the
remaining distance in gravel 14 or it can be removed
to the surface.When auger-screen 20 is properly
positioned within preset gravel 14 to form the gravel
pack, sub 19 is released and workstring and wash pipe
28 are withdrawn from the wellbore and are replaced
with production tubing or the like and packer 34 (~IC.
3) to finiqh the well completion as will be understood
by tho8e Qkilled in the art.
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