Note: Descriptions are shown in the official language in which they were submitted.
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1
WELL STABILIZATION TOOLS AND METHODS
Background of the Invention
1. Field of the Invention
The present inventioru relates to tads and methods for
enlarging and placing a cementitious cvaterial in a well bore
which passes through an unstable subterranean zone or
Formation during drilling.
.2. Description of the Prior Art
In the drilling of a well bore with a rotary drill bit,
~Neight is applied to the drill. string (a string of connected
drill pipe sections) while the drill bit is rotated. A
:Fluid, often referred t:o <~s dr~ill:i.~~g flu:ici or drilling mud,
:is circulated through the dr.il7_ st:rixzg, through the drill
bit and upwardly to the surirace through tlue annulus between
i~he drill string and the wal.l;~ of ts?ze well. bore. The
drilling fluid cools the drill bit., removes cuttings from
i:he well bore and ma:i.nta:i_ms h.yda ost:atic pressure on
pressurized subterranean formations.
During the drilling of a well bore, the well bore may
penetrate and pass through i.zcompetcmt: or~ ot:herwise unstable
subterranean zones or formations such as unconsolidated
;ands or shales . Such unstable zones <.:~r formations can have
very high permeabiiit:ies whereby revere drilling fluid
__osses occur into the cones ox- forma c: ions. Also, the zones
or formations can. cave :in, s:' ough off nor wash out due to the
i=low of drilling fluid through the well bore which causes
t:he well bore to enlarge. This, in turn, can cause the drill
mitring to become stuck as
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2
well as a variety of other severe problems. The zones or
formations can also be charged with a fluid, e.g. , water or gas,
which flows into the well bore making drilling difficult.
In order to solve the problems caused by an unstable
subterranean zone or formation, the portion of the well bore
passing through the zone or formation has heretofore been
enlarged and filled with cementitious material. After the
cementitious material has set, the well bore has been drilled
through the cementitious material leaving a cementitious sheath
in the well bore for preventing fluid influx, fluid losses,
cave-ins, etc. While such techniques have been utilized
successfully, they have heretofore required the use of many
different tools, the necessity of making many trips in and out
of the well bore, and a great deal of time and expense to
complete.
Thus, there is a need for improved tools and methods for
stabilizing unstable subterranean zones or formations penetrated
by a well bore which do not require the use of many different
tools, numerous drill string and/or work string trips, long
delays and the like.
Summary of the Invention
The present invention provides improved well stabilization
tools and methods which meet the needs described above and
obviate the shortcomings of the prior art.
The well stabilization tools and methods of the present
invention can be used to stabilize an unstable zone or formation
encountered in the drilling of a well bore without removing the
drill string and drill bit from the well bore or only doing so
a minimum of times. That is, one improved well stabilization
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3
tool of this invention can be connected in a drill string
adjacent the drill bit before the well bore is drilled. The
drilling of the well bore can then proceed in the normal manner
until an unstable zone or formation is encountered. The well
stabilization tool is then activated and used to enlarge the
portion of the well bore which passes through the unstable zone
or formation and to fill the enlarged well bore with a
hardenable cementitious material. Alternatively, in those
instances where washout or other well bore enlargement has
already occurred, it may be unnecessary to enlarge the portion
of the well bore which passes through the unstable zone or
formation prior to filling it with a hardenable cementitious
material. In such instances, the hardenable cementitious
material is placed in the same manner as described herein with
respect to the enlarged portions. After the cementitious
material has hardened, the well bore is drilled through the
hardened material and normal drilling operations are resumed.
The well stabilization tool used as described above is
basically comprised of a tubular housing having a fluid flow
passage extending therethrough adapted to be connected in a
drill string. The housing includes one or more outwardly
extending enlarged portions formed thereon whereby the outer
surfaces of the enlarged portions are positioned in close
proximity to the walls of the well bore drilled with the drill
string and drill bit and having one or more lateral fluid jet
forming ports extending from the fluid flow passage through the
enlarged portions of the housing to the exterior thereof . A
valve sleeve is releasably and slidably disposed within the
fluid flow passage of the housing which is movable between a
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first position whereby the fluid jet forming ports are closed
by the valve sleeve and fluid pumped through the drill string
is free to flow through the fluid flow passage of the housing
by way of the interior of the valve sleeve and a second position
whereby the fluid jet forming ports are opened.
The tool is activated by an activator plug which is flowed
through the drill string into the housing where it releasably
engages and plugs the valve sleeve causing it to move from the
first position to the second position whereby fluid pumped
through the drill string is forced through the fluid jet forming
ports of the tool. When the activator plug is retrieved, the
valve sleeve is pulled back to the first position so that fluid
again flows through the tool.
The methods of using the above described tool basically
comprise the steps of placing the tool in a drill string near
the drill bit, drilling a well bore with the valve sleeve of the
tool in the first position whereby fluid flows through the tool
and through the drill bit until the well bore has been drilled
through an unstable subterranean zone or formation. The tool
is then activated by means of the above mentioned activator plug
and the valve sleeve is moved to its second position whereby
fluid flows through the jet forming ports of the tool. When
necessary, fluid is pumped through the drill string and through
the tool at a rate while moving the tool through the portion of
the well bore in the unstable zone or formation whereby the
diameter of the well bore is enlarged by fluid jet erosion. A
hardenable cementitious material is then pumped through the
drill string and through the jet forming ports of the tool at
a rate while moving the tool through the enlarged portion of the
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well bore whereby the enlarged portion is filled with the
cementitious material. While the cementitious material is
allowed to harden, the activator plug is retrieved which moves
the valve sleeve back to its first position after which the well
bore is drilled through the hardened material and normal
drilling operations are resumed.
An alternate well stabilization tool of this invention for
enlarging and placing a cementitious material in an unstable
subterranean zone or formation passed through by a well bore
requires only a minimum number of trips in and out of the well
bore. That is, after a well bore penetrates and passes through
an unstable zone or formation, the drill string is removed from
the well bore, the drill bit is replaced with the well
stabilization tool and the tool and drill string are placed back
in the well bore. The tool is used to enlarge when necessary
and to place a hardenable cementitious material in the unstable
zone or formation whereupon the drill string is removed from the
well bore and the well stabilization tool is replaced with the
drill bit. After the drill string and drill bit have been
placed back in the well bore, the well bore is drilled through
the hardened cementitious material and normal drilling
operations are resumed.
The well stabilization tool used as described above is
basically comprised of a tubular housing having a longitudinal
fluid flow passage extending therethrough and having a plurality
of lateral threaded openings extending from the fluid flow
passage to the exterior of the housing. The housing includes
a seat for receiving an activated plug and a plurality of
tubular threaded arm members are threadedly connected within the
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threaded openings in the housing. T'he threaded arm members
have fluid flow passages extending the:~rethrough and have
fluid jet forming ports communicating with the passages at
their exterior ends. 'The arm members are of lengths such
that the fluid jet forming ports at. the exterior ends
thereof are positioned in close proximity to the walls of
the well bore. A further feature of this tool is that the
tool can be made up using d:~.ffe.rent sizes of arm members to
conform the tool to varying well bore sizes.
Therefore, in accordance with thE: present invention,
there is provided a method of stabi~.izing an enlarged
portion of an unstable subterranean zone or formation passed
Through by a well bore during the dr-i:~ lung of the we:Ll bore
with a drill bit connected to a drill string comprising the
;steps of
(a) placing a well stabilization tool in the drill
:string near the drill bit, said tool. hawing a longitudinal
:Fluid flow passage ther_~et.l~rougn, having c ne or more :Lateral
fluid ports therein and having an internal valve which can
be selectively moved between a r~irst position whereby fluid
pumped into the drill string is f::l.owed through said fluid
i=low passage of said tool and t~hraugh the drill bit and a
second position whereby said fluid i.~; a lowed through said
lateral fluid ports of :aaid t.oal;~
(b) drilling the well bore wits said valve of said
tool in said first posi.t:iori ~.~nt.zl t~ve well bore has been
drilled through the unst;ab:le subterranean zone or formation;
(c) moving said valve of saica tool from said first
position to said second posit:ian;
(d) pumping a hardenable cementitious material
through the drill string and through°~ said ports of said tool
at a rate while moving said tool thz~ough the enlarged
portion of the well box-e in the unstable zone or formation
whereby the enlarged portion of ,:.he we~l.l bore is filled with
said hardenable cementit.i.oi.zs material ;
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6a
(e) moving said valve of said tool back to said
first position while said c~ementitious material is allowed
to harden; and
(f) drilling the well bore through said hardened
cementitious material.
Also in accordance with the present invention, there is
provided a method of utabiliz:ing an enlarged portion of an
unstable subterranean zone or formation penetrated by a well
bore during the drilling of the well bo.:r~e with a drill bit
connected to a drill string comprising the steps of:
(a) placing a well stabil:izatic~n tool in the drill
string adjacent to the drill bi.t, said tool comprising:
a tubular h.ous5.zng to.aviz:~g a longitudinal fluid
flow passage extending thereth.rough, having one or more
outwardly extending enlarged portions formed thereon whereby
v~he outer surfaces of sai~~ enlarged portions are positioned
:in close proximity to the walls of the well bore drilled
with the drill string and drill bit and having one or more
:Lateral fluid ports extending from said fluid flow passage
through said enlarged portions of said housing to the
exteriors thereof, and
a valve sleeve releasably and s:Lidably
disposed within said fluid flow passage t~f said housing and
being movable between a first pos~.tion whereby said fluid
ports are closed by said valve ~al.c~eve and fluid pumped
through the drill string is free t.o flow through said
housing by way of the interior of said valve sleeve and a
second position whereby said fluid ports are opened;
(b) drilling the-_ wel:1 bt~re withx said valve sleeve
of said tool in said first position whi_Le pumping drilling
i=luid through the drill string and drill. bit until the well
bore has been drilled through the unstable subterranean zone
or formation;
(c) flowing an activator plug with drilling fluid
through the drill string and tool h~~,o.asirlg into releasable
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6b
engagement with said valve sleeve whez:~eby said activator
plug and valve sleeve are moved by drilling fluid pressure
to said second position and drilling ~lu:i.d is flowed through
said lateral fluid ports;
(d) pumping a hardenable cernentitious material
through the drill string and through said fluid ports at a
rate while moving said tool through the enlarged portion of
the well bore in the unstab-_e zone o~- fc.:~rrnat.ion whereby the
~snlarged portion. o.f the well bore is filled with said
'.zardenable cementitious material;
(e) retrieving ~~aid activator ialug from said tool
housing and from the drill string while said cementitious
material is allowed to harden whereby said value sleeve is
pulled from said second position to said first position
prior to when said activator plug is x:ea.E~ased and disengaged
:From said valve sleeve; and
(f) drilling the well bore through said hardened
c:ementitious material whi:l.e pum;p:ing car:i:~ ling fluid through
i~he drill string and drill bit.
Further in accordance witrn the present invention,, there
is provided a method of stabilizing an enlarged portion of
an unstable subterranean zone or formation passed through by
a well bore during the dri.ll.i.ng o.f t~hF~ well bore with a
drill bit connected to a dril_1 string comprising:
(a) removing the drill st..r~_rig and drill bit from
t;he well bore;
(b) connecting a well stabilization tool to the
drill string in place off- the dz:-:i11, bit, said well
stabilization tool comprising:
a tubular housing havirvg a ~l.ongitudinal. fluid
flow passage extending therethrough, having a threaded drill
mitring connection at the upper erzc~ thereof, having a
plurality of lateral openings extending from said fluid flow
passage to the exterior of said housing and having an
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6c
annular seat extending into said flaw passage below said
lateral openings for receiving an activator plug, and
a plurali..ty c~f t.ub~z:i<zx.~ arm members connected
within said openings in said :~o~zsi.ng having fluid flow
passages therethrough and having flt.rid parts communicated
with said fluid flow passages at tlue exterior ends thereof,
said arm members being of lengths such ttnat said fluid ports
at the exterior ends t: hereof are p<~sitioned in close
proximity to the walls oft::he wel:_ borE: when said tool is
connected to the drill string and placed in the well bore;
(c) placing tr:~e drill. string and well
stabilization tool in the well bore with said tool
positioned within the part iorz of t:: he well bore in the
vanstable zone or formation;
(d) flowing an activator plug with fluid pumped
~~hrough the drill string into sa d hozzsing of said tool
whereby said activator plug lands on said annular seat in
;paid housing and said Fluid is caused tca flow through said
t=ubular arm members cf said too:? and said fluid ports
thereof ;
(e) pumping a ha.rdenable cementitious m<~terial
through the drill string and through said fluid ports at a
gate while moving said tool through trze enlarged portion of
i:he well bore in the unstab7..e zone or formation whereby the
enlarged portion of the well bore is filled with said
hardenable cementitious material;;
(f) removing the drill string and well
;stabilization tool # ram the we~l...l. bore while said
cementitious material is allowed to hay°den;
(g) reconnecting a drill bit to the drill string
and placing the drill string arid dry 1l.. b~.t in the wel7_ bore;
and
(h) drilling the well bore through said hardened
c:ementitious material.
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6d
It is, therefore, a general object of the present
invention to provide improved well stabilization tools and
methods.
Other and further
object's,
feature:;
and advantages
of
the present invention will be readily apparent to those
skilled in he art upon a read:irag of the description of
t
preferred.
embodiments
which fa~lLows
when taken
in
conjunction ith the accompanying drawings.
w
Brief Description of the Dr~v~rings
FIGURE 1 is a side partif~lly seotic3nal view of a well
stabilization tool of the pr=,~sent i~vvfnti.oru.
FIGURE 2 is a side cro~~s-sectional v_i.ew of the tool
of
FIG. 1 after an activator plug has engaged a valve sleeve
in
the tool.
FIGURE 3 is a side cro ss-sectional sra.ew of the tool
of
FIG. 1 after the activator plug and ,ralve sleeve have been
moved downwardly
in the tool
by fluid pressure.
FIGURE 4 is a side cro~~s-sect:iorlal ~riew of the tool
of
fIG. 1 after a fishing tool has en~~acJ~-:d tIe fishing neck
of
the activator plug within the tool.
FIGURE 5 is a cross-:sectior~a:1 view ~of the tool of
FIG.
1
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7
after the activator plug and valve sleeve have been moved
upwardly within the tool as the activator plug is being
retrieved therefrom.
FIGURE 6 is a side cross-sectional view of the valve sleeve
of the tool of FIG. 1.
FIGURE 7 is a top view of the valve sleeve of FIG. 6.
FIGURES 8 - 13 are sequential schematic illustrations of
a well bore drilled through an unstable zone or formation and
the stabilization of the well bore using the tool of FIG. 1 and
the method of the present invention.
FIGURE 14 is a schematic illustration of an alternate well
stabilization tool of this invention in a well bore which passes
through an unstable zone or formation.
FIGURE 15 is a side partially cross-sectional view of the
tool illustrated in FIG. 14 having additional arm members
connected thereto.
FIGURE 16 is a cross-sectional view taken along line 16-16
of FIG. 15.
FIGURE 17 is a cross-sectional view taken along line 17-17
of FIG. 15.
Description of Preferred Embodiments
Referring now to the drawings and particularly FIGS. 1-6,
an embodiment of the well stabilization tool of the present
invention is illustrated and generally designated by the numeral
10. The tool 10 is comprised of a tubular housing 12 having a
longitudinal fluid flow passage 14 extending therethrough. The
housing 12 includes a conventional female threaded connection
16 at the upper end thereof for threaded connection to a drill
string 18. As is well understood by those skilled in the art,
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8
the drill string 18 is made up of a plurality of drill pipe
sections threadedly connected end to end. A complimentary male
threaded connection 20 is provided at the lower end of the
housing 12 for connecting the tool 10 to a drill pipe section,
a drill collar or the drill bit (not shown).
The housing 12 includes four outwardly extending enlarged
rib portions 22 which are positioned in close proximity to the
walls of a well bore drilled with the drill string 18 and a
drill bit (not shown) connected below the tool 10. As will be
understood by those skilled in the art, the housing 12 can
include a single cylindrical enlarged portion or two or more
enlarged rib portions 22 as desired. The housing 12 further
includes a plurality of fluid jet forming passages or ports 24
formed therein extending from the fluid flow passage 14 of the
housing 12 through the enlarged rib portions 22 thereof to the
exterior of the housing 12. Preferably, the lateral ports 24
are arranged in two groups of three or four equally spaced ports
24 (two groups of four ports 24 are illustrated in the
drawings). Also, the ports 24 preferably intersect enlarged
counter bores 26 in the housing 12 adjacent the exterior thereof
and include fluid jet forming nozzles 28 threadedly connected
therein. In an alternative embodiment (not shown), the nozzles
28 may extend through the full length of the lateral ports 24
to the fluid passage 14 for preventing erosion of the housing
12 and to increase the fluid jetting efficiency therefrom. As
will be described further hereinbelow, some of the ports 24 can
include plugs instead of nozzles 28, and the sizes of the flow
passages through the nozzles 28 can be varied as required to
produce the desired number and velocities of the fluid jets
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9
issuing from the tool 10.
The tool 10 includes a valve sleeve 30 releasably and
slidably disposed within the fluid flow passage 14 of the
housing 12. The valve sleeve 30 includes an elongated
cylindrical body portion 32 having a pair of longitudinally
spaced grooves 34 formed in the exterior surface thereof with
conventional O-ring seals 36 disposed therein. As shown in
FIGS. 1, 2 and 5, the grooves 34 in the valve sleeve 30 are
spaced a distance apart whereby the 0-ring seals bracket the
lateral fluid jet forming ports 24 when the valve sleeve is in
its first position as shown in FIGS 1, 2 and 5.
As shown best in FIGS. 6 and 7, the upper end portion of
the valve sleeve 30 includes an internal activator plug
receiving seat 38 and a collet 40 comprised of a plurality of
collet fingers 42 extending upwardly from the receiving seat 38.
Each of the collet fingers 42 of the collet 40 have collet heads
44 at the upper ends thereof. The collet heads 44 protrude
radially outwardly and the external surfaces of the collet
fingers 42 below the heads 44 are recessed whereby the lower
surfaces 43 of the collet heads 44 are inclined (as shown in
FIG. 6). Alternatively, the collet heads 44 may include
additional collet fingers (not shown) extending upwardly
therefrom, wherein the collet fingers (not shown) are attached
to one another at an end distant from the collet heads 44. When
the valve sleeve 30 is in its first position within the housing
12 as illustrated in FIGS. 1, 2 and 5, the collet heads 44 of
the collet 40 extend within a complimentary groove 46 in the
housing 12 whereby the valve sleeve 30 is releasably retained
in the first position.
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When it is desired to activate the tool 10, i.e., move the
valve sleeve 30 to a second position within the flow passage 14
of the housing 12 whereby the fluid jet forming ports are
opened, an activator plug 50 is flowed through the drill string
18 and housing 12 into releasable engagement with the valve
sleeve 30 as illustrated in FIG. 2.
The activator plug 50 includes an elongated nose portion
52 which is of an external size slightly smaller than the
internal diameter of the valve sleeve 30. The nose portion 52
includes an O-ring groove 54 with an O-ring 56 disposed therein
for providing a seal between the external surface of the nose
portion 52 and the internal surface of the valve sleeve 30.
Immediately above the nose portion 52 of the activator plug 50
is an enlarged portion 58 which forms an annular shoulder or
seat 60 on the activator plug 50 complimentary to the annular
seat 38 within the valve sleeve 30. An annular groove 62 is
formed in the enlarged portion 58 of the activator plug 50 which
is positioned to receive the collet heads 44 of the collet 40
as will be described hereinbelow. Finally, the activator plug
50 includes a reduced diameter upwardly extending fishing neck
64 connected to the enlarged portion 58.
When the activator plug 50 is flowed by drilling fluid
pumped through the drill string 18 and housing 12 of the tool
10 into engagement with the valve sleeve 30 as illustrated in
FIG. 2, the seat 60 of the activator plug 50 lands on the seat
38 of the valve sleeve 30 thereby plugging the interior of the
valve sleeve 30 and moving it to a second position as shown in
FIG. 3. That is, the activator plug 50 seals the interior of
the valve sleeve 30 whereby fluid pressure produced by drilling
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11
fluid pumped through the drill string and into the housing 12
forces the activator plug 50 and valve sleeve 30 to move
downwardly in the passage 14 of the housing 12. As the
activator plug 50 and valve sleeve 30 move downwardly, the
collet heads 44 of the collet 40 are pulled out of the annular
groove 46 in the housing 12 whereby the valve sleeve 30 is
released from its first position. Simultaneously, the collet
heads 44 are deformed into the annular groove 62 in the enlarged
portion 58 of the activator plug 50 as illustrated in FIGS. 3
and 4 whereby the valve sleeve 30 is releasably engaged by the
activator plug 50.
As shown in FIG. 3, the downward movement of the activator
plug 50 and valve sleeve 30 is terminated when the valve sleeve
reaches its second position by an annular shoulder 66 extending
into the fluid flow passage 14 of the housing 12. In the form
illustrated in the drawings, the annular shoulder 66 is formed
by a snap ring 68 disposed within a groove 70 in the housing 12.
As will be understood, when the valve sleeve 30 is in its second
position shown in FIG. 3, fluid pumped through the drill string
and into the housing 12 of the tool 10 flows through the fluid
jet forming ports 24 of the housing 12.
When it is desired to move the valve sleeve 30 of the tool
back to its first position and remove the activator plug 50
from the interior of the housing 12 of the tool 10 whereby
normal well bore drilling can be resumed, a fishing tool 72 is
lowered through the drill string 18 by means of a wire line, a
slick line or a working string into the flow passage 14 of the
housing 12 whereby the fishing neck 64 of the activator plug 50
is engaged by the fishing tool 72 as shown in FIG. 4.
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12
Thereafter, the fishing tool 72 and activator plug 50 are raised
whereby they are moved upwardly within the housing 12. As the
activator plug is moved upwardly, the valve sleeve 30 is pulled
with it since the collet heads 44 of the collet 40 of the valve
sleeve 30 extend into the annular groove 62 of the activator
plug 50 and are engaged thereby. When the activator plug 50 and
the valve sleeve 30 are pulled upwardly to the point where the
valve sleeve 30 reaches its first position, the collet heads 44
of the valve sleeve 30 spring back into the annular groove 46
in the housing 12 and out of the annular groove 62 in the
activator plug 50. This releases the activator plug 50 from the
valve sleeve 30 whereby the continued upward movement of the
fishing tool 72 and activator plug 50 removes the activator plug
50 from the tool 10. The fishing tool 72 and activator plug 50
are then lifted to the surface and removed from the drill
string.
Referring now to FIGS. 8-13, various preferred steps
involved in stabilizing an unstable subterranean zone or
formation passed through by a well bore during its drilling
using the well stabilization tool 10 are schematically
illustrated. Referring specifically to FIG. 8, a well bore 80
which has been drilled through an unstable subterranean zone or
formation 82 with a drill string 84 having the tool 10 and a
drill bit 86 connected thereto is illustrated. As will be
understood, the well stabilization tool 10 is placed in the
drill string prior to the commencement of drilling with the
valve sleeve 30 in its first position whereby drilling fluid
pumped into the drill string 84 during drilling flows through
the flow passage 14 of the housing 12 of the tool 10 and through
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13
the interior of the valve sleeve 30, through the drill bit 86
and upwardly through the annulus between the drill string 84 and
well bore 80. When the well bore 80 has been drilled to a depth
whereby it has passed through the unstable zone or formation 82,
the drilling of the well bore is stopped and the activator plug
50 is placed into the drill string 84 at the surface. The
activator plug 50 is caused to flow by pumped drilling fluid
through the drill string 84 and into the housing 12 of the tool
where it engages the valve sleeve 30 of the tool 10, moves
it from its first position to its second position and opens the
lateral fluid jet forming ports 24.
Referring now to FIG. 9, after the fluid jet forming ports
24 are opened, drilling fluid is pumped through the drill string
and through the fluid jet forming ports 24 of the tool 10 at a
rate while moving the tool 10 through the portion of the well
bore 80 in the unstable zone or formation 82 whereby the
diameter of the well bore 80 is enlarged by fluid jet erosion.
That is, the drilling fluid jets issuing from the ports 24 of
the tool 10 impinge on the walls of the well bore 80 in the
unstable zone or formation 82 causing the well bore 80 to be
eroded and enlarged as illustrated in FIGS. 9 and 10.
Alternatively, if the unstable zone or formation is already
suf f iciently enlarged due to washout etc . , it may be unnecessary
to pump drilling fluid through the ports 24 and to jet the well
bore 80 for enlarging the zone or formation. Thus, jetting the
well bore 80 to enlarge a portion thereof may not be necessary
when a sufficient amount of hardenable cementitious material can
be placed in the unstable zone or formation to provide the
desired well bore stabilization.
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14
Referring now to FIG. 11, once the portion of the well bore
80 passing through the unstable zone or formation 82 has been
enlarged, a hardenable cementitious material is pumped through
the drill string 84 and through the jet forming ports 24 of the
tool 10 at a rate while moving the tool 10 through the enlarged
portion of the well bore 80 whereby the enlarged portion of the
well bore is filled with a quantity 90 of cementitious material
as shown in FIGS. 11 and 12.. As shown in FIG. 12, when the
enlarged portion of the well bore 80 has been completely filled
with the cementitious material, the drill string 84, the tool
and drill bit 86 are moved to a position in the well bore 80
above the enlarged portion containing the cementitious material
and the cementitious material is allowed to harden. While the
cementitious material is hardening, the activator plug 50 is
removed from the tool 10 and drill string 84 which closes the
ports 24 of the tool 10. Thereafter, the well bore 80 is
redrilled through the hardened cementitious material as shown
in FIG. 13 and normal drilling operations are resumed. The
cement sheath 91 which remains in the unstable zone or formation
stabilizes the well bore passing therethrough and prevents such
problems as excessive, fluid influx, fluid loss, cave ins, wash
outs, etc.
As will be understood by those skilled in the art, a
variety of hardenable cementitious materials can be utilized in
accordance with this invention for stabilizing an unstable
subterranean zone or formation. For example, hydraulic
cementitious materials which form hard impermeable masses in the
presence of water can be utilized such as Portland cement, high
alumina cement, slag and/or fly ash (ASTM Class F fly ash) and
CA 02212198 1997-08-O1
lime, fly ash which includes free lime (ASTM Class C fly ash),
condensed silica fume with lime, gypsum cement (calcium sulfate
hemihydrate) and mixtures of the foregoing materials.
Hardenable cementitious materials which are not hydraulic such
as hardenable resins, polymers and the like can also be used.
Examples of such materials which are not hydraulic include epoxy
resins, furan resins and acrylamide polymer gels. The
particular cementitious material used depends upon a variety of
factors relating to the particular unstable zone or formation
to be stabilized. Essentially, any pumpable cementitious
material that will harden after being placed in a subterranean
zone at the temperature, pressure and other conditions in the
zone to provide stability thereto after the well bore has been
drilled through the material can be utilized.
Thus, the method of stabilizing an unstable subterranean
zone or formation passed through by a well bore during the
drilling of the well bore with a drill bit connected to a drill
string using the tool 10 basically comprises the following
steps:
(1) placing the well stabilization tool 10 in the
drill string near the drill bit, the tool having a longitudinal
fluid flow passage therethrough, having one or more lateral
fluid jet forming ports therein and having an internal valve
which can be selectively moved between a first position whereby
fluid pumped into the drill string is flowed through the fluid
flow passage of the tool and through the drill bit and a second
position whereby the fluid is flowed through the lateral fluid
jet forming ports of the tool;
(2) drilling the well bore with the valve of the well
CA 02212198 1997-08-O1
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stabilization tool in its first position until the well bore has
been drilled through the unstable subterranean zone or
formation;
(3) moving the valve of the tool from its first
position to its second position and if necessary pumping fluid
through the jet forming ports at a rate while moving the tool
through the portion of the well bore in the unstable zone or
formation whereby the diameter of the well bore is enlarged by
fluid jet erosion;
(4) pumping a hardenable cementitious material through
the drill string and through the jet forming ports of the tool
at a rate while moving the tool through the enlarged portion of
the well bore in the unstable zone or formation whereby the
enlarged portion of the well bore is filled with the
cementitious material;
(5) moving the valve of the tool back to its first
position while the cementitious material is allowed to harden;
and then
(6) drilling the well bore through the hardened
cementitious material thereby forming a hardened cementitious
material sheath in the unstable zone or formation which
stabilizes the well bore.
Another well stabilization tool of this invention for
enlarging and placing a hardenable cementitious material in an
unstable subterranean zone or formation passed through by a well
bore is illustrated in FIGS. 14-17 and is generally designated
by the numeral 100. The well stabilization tool 100 does not
include a valve and is adapted to be connected to a drill string
in place of the drill bit. That is, when a well bore has been
CA 02212198 1997-08-O1
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drilled through an unstable subterranean zone or formation
utilizing a drill bit connected to a drill string, the drill
string and drill bit are removed from the well bore and the
drill bit is replaced with the tool 100. In addition, if the
drill string does not - already include a drill string
centralizes, such a centralizes is placed in the drill string
adjacent to or near the well stabilization tool 100. As will
be described further hereinbelow, the well stabilization tool
100 is utilized to enlarge, unless such portion is already
sufficiently enlarged, the portion of the well bore passing
through the unstable zone or formation and to fill the enlarged
portion of the well bore with a cementitious material. While
the cementitious material is setting, the drill string having
the well stabilization tool connected thereto is pulled from the
well bore, the well stabilization tool and drill string
centralizes (if not left in the drill string) are removed from
the drill string, the drill bit is replaced on the drill string
and the drill string and drill bit are placed in the well bore.
The drill string and drill bit are used to drill the well bore
through the set cementitious material leaving a cementitious
sheath in the unstable zone or formation which stabilizes the
zone or formation. Thereafter, normal drilling operations are
resumed.
Referring now to FIG. 14, a well bore 102 drilled through
an unstable zone or formation 104 is illustrated. The drill
string has previously been removed from the well bore and the
drill bit replaced with a conventional drill string centralizes
106 and the well stabilization tool 100. Drill string
centralizers are well known to those skilled in the art and
CA 02212198 1997-08-O1
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function to maintain the drill string and tools connected
thereto in a central position within the well bore. For
example, the drill string centralizer illustrated in FIG. 14 is
a typical bow spring type of centralizer which contacts the
walls of the well bore and expands or compresses as required.
The centralizer 106 can be a separate tool or an integral part
of the well stabilization tool 100. The drill string 108
including the centralizer 106 and tool 100 are placed in the
well bore 102 and lowered to the portion of the well bore 102
within the unstable zone or formation 104. When the well bore
80 is not large enough to receive a sufficient amount of
hardenable cementitious material therein for stabilizing the
unstable zone or formation, the tool 100 is utilized to enlarge
the portion of the well bore 102 within the zone or formation
104 as shown in FIG. 14. Subsequently, the tool 100 is used to
fill the enlarged portion with a cementitious material in the
same manner as described above in connection with the well
stabilization tool 10. As mentioned above, the centralizer 106
and the well stabilization tool 100 are removed from the drill
string 108 while the cementitious material sets, and the drill
string and drill bit are placed back in the well bore, used to
drill the well bore through the set cementitious material and
to continue drilling the well bore below the unstable zone or
formation.
Referring now to FIGS. 15-17, the well stabilization tool
100 is illustrated in detail. The tool 100 basically comprises
a tubular housing 110 having a longitudinal fluid flow passage
112 extending therethrough. A threaded connection 114 is
provided at the upper end of the housing 112 for connecting the
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tool 100 to the drill string, and a plurality of lateral
threaded openings 116 extending from the fluid f low passage 112
to the exterior of the housing 110 are formed in the housing
110. An annular seating surface 118 is provided within the
fluid flow passage 112 of the housing 110 below the lateral
threaded openings 116 therein for receiving an activator plug
120 (as shown in FIG. 15). As will be understood, the activator
plug 120, which can be in the form of a ball, is flowed by
drilling fluid to within the flow passage 112 of the housing 110
of the tool 100 and lands on the seat 118. The activator plug
120 plugs the passage 112 whereby drilling fluid is forced to
flow through the lateral threaded openings 116 of the tool 100.
A plurality of tubular threaded arm members 122 are
threadedly connected within the threaded openings 116 in the
housing 110. Each of the threaded arm members 122 includes a
flow passage 123 therethrough and a fluid jet forming port 124
formed in the end thereof. Like the previously described well
stabilization tool 10, the fluid jet forming ports 124 of the
tubular threaded arm members 122 can include nozzles 126
threadedly connected thereto which can be varied in size to vary
the velocities and other aspects of the fluid jets formed.
Prior to using the well stabilization tool 100 for
enlarging and placing a hardenable cementitious material in a
well bore passing through an unstable zone or formation, tubular
threaded arm members 122 are threadedly connected in the lateral
threaded openings 116 of the tool 10. The tubular threaded arm
members 122 have lengths such that the fluid jet forming ports
24 at the exterior ends of the threaded arm members 122 are
positioned in close proximity to the walls of the well bore in
CA 02212198 1997-08-O1
which the tool is to be used. To accomplish this, various
lengths of tubular threaded arm members 122 can be made
available for installation in the housing 110, or arm members
122 which are too long can be shortened by cutting portions
therefrom at the interior ends thereof.
As shown in FIG. 14, the tool 100 can include a number of
tubular threaded arm members 122 less than the number of lateral
threaded openings 116 in the housing 110. The openings which
do not have tubular threaded arm members 122 connected thereto
can be plugged by threaded plugs 130.
The well stabilization tool 100 preferably includes seven
lateral threaded openings 116 therein with four of the openings
116 being equally spaced around the periphery of the housing 110
at a first upper position on the housing 110 and three of the
threaded openings 116 being equally spaced around the periphery
of the housing 110 at a second lower position on the housing 110
as shown in FIGS . 15-17 . The tool 100 can include seven tubular
threaded arm members 122 as illustrated in FIGS. 15-17, or less
than seven threaded arm members 122 can be utilized as mentioned
above . Preferably, when less than seven arm members 122 are
utilized, they are either two, three or four in number. When
two or four threaded arm members 122 are used they are connected
within two opposite or all four of the four equally spaced
threaded openings 116 in the upper position on the housing 110
with two threaded openings in the upper position and/or the
threaded openings 116 in the lower position being plugged. When
three threaded arm members 122 are used they are threadedly
connected within the three threaded openings 116 in the lower
position on the housing 110 with the threaded openings 116 in
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the upper position being plugged.
Thus, the method of stabilizing an unstable subterranean
zone or formation passed through by a well bore during the
drilling of the well bore with a rotary drill bit connected to
a drill string utilizing the well stabilization tool 100
basically comprises the following steps:
(1) removing the drill string and drill bit from the
well bore;
(2) connecting a drill string centralizer and/or a
well stabilization tool 100 to the drill string in place of the
drill bit, the well stabilization tool comprising,
a tubular housing having a longitudinal fluid
flow passage extending therethrough, having a threaded drill
string connection at the upper end thereof, having a plurality
of lateral threaded openings extending from the fluid flow
passage to the exterior of the housing and having an annular
seat extending into the flow passage below the lateral threaded
openings for receiving an activator plug, and
a plurality of tubular threaded arm members
threadedly connected within the threaded openings in the housing
having fluid flow passages therethrough and having fluid jet
forming ports communicated with the fluid flow passages at the
exterior ends thereof , the arm members being of lengths such
that the fluid jet forming ports at the exterior ends thereof
are positioned in close proximity to the walls of the well bore
when the tool is connected to the drill string and placed in the
well bore;
(3) placing the drill string, centralizer and well
stabilization tool in the well bore with the tool positioned
CA 02212198 1997-08-O1
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within the portion of the well bore in the unstable zone or
formation;
(4) flowing an activator plug with fluid pumped
through the drill string into the housing of the tool whereby
the activator plug lands on the annular shoulder in the housing
and the f luid is caused to f low through the tubular arm members
and the fluid jet forming ports of the tool;
(5) if necessary, pumping fluid through the jet
forming ports at a rate while moving the tool through the
portion of the well bore in the unstable zone or formation
whereby the diameter of that portion of the well bore is
enlarged by fluid jet erosion;
(6) pumping a cementitious material through the drill
string and through the fluid jet forming ports at a rate while
moving the tool through the enlarged portion of the well bore
in the unstable zone or formation whereby the enlarged portion
of the well bore is filled with the cementitious material;
(7) removing the drill string and well stabilization
tool from the well bore while the cementitious material is
allowed to set;
(8) reconnecting a drill bit to the drill string and
placing the drill string and drill bit in the well bore; and
(9) drilling the well bore through the set
cementitious material to thereby form a cementitious sheath in
the well bore which stabilizes the well bore passing through the
unstable zone or formation and resuming normal well bore
drilling operations.
Thus, the well stabilization tools and methods of the
present invention are well adapted to carry out the objects and
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attain the ends and advantages mentioned as well as those which
are inherent therein. While numerous changes to the tools and
methods can be made by those skilled in the art, such changes
are encompassed within the spirit of this invention as defined
by the appended claims.
