Method and apparatus for treating multiple production zones

The method and apparatus for treating multiple production zones includes a completion string having a plurality of sets of tools including a closing sleeve, indicator collar, and production screens with an isolation packer disposed between each adjacent set. An inner service tool is disposed within the outer completion string and includes an upper portion with a crossover tool and a lower portion with a closing sleeve shifter and a weight-down collet with the upper and lower portions being connected. The apparatus is assembled by assembling an initial length of the outer completion string which does not includes any of the closing sleeves or indicator collars. After the initial length is assembled, the lower portion of the service tool with the closing sleeve shifter and weight-down collet are assembled and inserted into the initial length of completion string. The remainder of the completion string is then assembled with all closing sleeves in the closed position. The upper portion of the service tool is then assembled and stabbed and connected into the lower portion. As multiple production zones are treated, the inner service tool is raised and then lowered opening a closing sleeve and setting weight on the indicator collar. A predetermined amount of weight is then maintained during the operation to ensure that the crossover tool is positioned adjacent the opened closing sleeve. The production zone then may be treated in the weight-down position.

BACKGROUND OF THE INVENTION 
The present invention relates to a method and apparatus for gravel packing, 
frac packing or other treatment of a production zone and more particularly 
for gravel packing, frac packing or other treating of multiple production 
zones with one trip of the apparatus into the well. 
During the production of hydrocarbons from a well, loose sand and degraded 
sandstone migrate into the wellbore as the formation deteriorates under 
the pressure and flow of fluids. This migration of particles may 
eventually clog the flow passages in the well. One method of controlling 
migration into a wellbore is the placing of a pack of gravel on the 
exterior of a perforated or slotted liner or screen which is positioned 
across from the producing formation to present a barrier to the migrating 
sand while permitting hydrocarbon flow. The gravel is carried to the 
formation in the form of a slurry, the carrier fluid being removed and 
returned to the surface. The gravel is packed around an inner liner or 
screen which maintains the gravel around the exterior of the screen and 
the slurry fluid enters the liner or screen from its exterior for flow 
back to the surface or is forced into the formation. 
In a typical gravel packing operation, a liner assembly having a perforated 
liner or screen is disposed within a perforated casing and positioned 
adjacent the formation. A packer is set above the zone between the liner 
and the well casing. A tubing string is run inside the liner assembly at 
the area of the zone. Gravel slurry is pumped down the tubing string and 
through a crossover tool and out into the annulus between the liner and 
the casing below the packer at a suitable location above the zone where it 
descends and the gravel is deposited in the area of the screen as the 
carrier fluid passes through the screen. The crossover tool routes the 
upward movement of the returning fluid back outside the liner assembly, 
the fluid then traveling up to the surface. Once a pressure build up is 
noted at the surface, the flow of gravel-laden fluid is stopped. After the 
gravel packing is completed, the tool is generally moved and the 
circulation of fluid is reversed, a clean fluid being pumped down the 
casing annulus and back up the tubing in order to flush out sand remaining 
in the tubing. Subsequently, the well may be subject to other treatments, 
if necessary, and produced. One such treatment may be fracturing the well. 
Patents disclosing different methods of gravel packing include U.S. Pat. 
Nos. 3,710,862; 3,952,804; and 4,044,832. 
In gravel packing wells having multiple production zones, it is desirable 
to utilize a method and apparatus which has the capability of gravel 
packing the multiple zones in a single trip into the well. See for 
example, U.S. Pat. Nos. 4,105,069 and 4,270,608. 
Some prior art methods and apparatus for gravel packing multiple zones 
require that the operating string trip into the well for each producing 
zone. The outer string, containing the packing screens, are assembled from 
the bottom up in a step by step process and then the operator must 
withdraw the operating string between zones in order to add components to 
the outer string. This also renders it impossible to pack an upper zone 
before a lower zone, or to set or inflate packers in any order other than 
the lowest packer first. Because of the order in which the zones are 
packed, it is almost impossible to repack zones below the uppermost zone. 
In some instances, this is due to an inability to place the operating 
string back in the desired location, due to restrictions placed in the 
outer string after packing a zone. In other cases it is due to an 
inability to relocate the desired zone and to position the gravel ports 
with any precision. 
A conventional multi-zone packing system includes an outer completion 
string having a production packer with slips for supporting the completion 
string within the cased well. Disposed below the production packer is an 
upper closing sleeve and an upper zone screen. An isolation packer is 
disposed below the upper zone screen and a lower closing sleeve and a 
lower zone screen which are disposed below the isolation packer. A first 
seal bore is disposed between the production packer and upper closing 
sleeve and a second seal bore is disposed between the upper closing sleeve 
and upper zone screen. A third seal bore is disposed between the upper 
zone screen and isolation packer and a fourth seal bore is disposed at the 
lower zone screen. A sump packer is disposed below the lower zone screen 
around a lower seal assembly. In the case of an open hole, inflatables 
would be used in place of the sump packer and isolation packers. An inner 
service tool includes a plurality of seal units forming an outer conduit 
and an inner center tube. The center tube and seal units form an annulus 
extending from upper ports in the uppermost seal unit to lower crossover 
ports extending through the outer conduit formed by the seal units and 
center tube. An additional length of seal units extends from the crossover 
ports downwardly for several feet followed by an extension and an 
additional set of seal units to a ported sub and lower seal assembly at 
its lower end. To be able to open and close the closing sleeves, the 
service tool includes at least two shifting tools, one above the crossover 
tool and one below. A single shifting tool may be used but it must be 
located very close to the gravel pack ports so that the shifting tool can 
be raised a very short distance, close the closing sleeve, and still have 
the gravel pack ports within the short distance range. An upper ball check 
is provided at the lower terminal end of the center tube to prevent 
downward flow through the flowbore of the center tube. A lower check valve 
is provided in the conduit of the seal units to prevent the downward flow 
of fluids in the annulus and into the flowbore formed by those seal units 
disposed below the crossover ports. Another ball check valve is provided 
at the lower terminal end of the seal units. 
In operation, the sump packer is lowered into the well and set by a wire 
line at a predetermined location in the well below the zones to be 
produced. The completion string is then assembled at the surface starting 
from the bottom up until the completion string is completely assembled and 
suspended in the well up to the packer at the surface. Then, the inner 
service tool is assembled and lowered into the outer completion string. 
The service tool includes one or more shifting tools, depending upon the 
number of production zones, for opening and closing the closing sleeves. 
When the service tool is lowered into the completion string, the shifting 
tool opens all of the closing sleeves in the completion string. Therefore, 
it does not matter whether the closing sleeves were initially in the open 
or closed position since the shifting tools will move them all to the open 
position as they pass downwardly through the completion string. These 
sleeves later must be moved to the closed position to set the isolation 
packer. The packer assembly and setting tool are then attached to the 
upper ends of the service tool and completion string and the entire 
assembly lowered into the well on a work string onto the sump packer. Upon 
aligning the zone screens with the production zones, the production packer 
is set to suspend the completion string within the cased well. 
In gravel packing the lower production zone, the setting tool is 
disconnected from the completion string and is raised such that the set of 
upper seals no longer engages the first seal bore of the production 
packer. At that time, the seals on the upper seal units sealingly engage 
the first, third, and fourth seal bores and the crossover ports are 
adjacent the lower closing sleeve which is open. In order to set the 
isolation packer, the lower closing sleeve must be closed utilizing a 
shifting tool in the service string so that the annulus between the 
closing sleeve and the outside of the service tool may be pressurized to 
set the isolation packer. 
Gravel slurries are then pumped down the flowbore of the work string and 
center tube. The ball check valve directs the gravel through the crossover 
ports and through the open lower closing sleeve and into the lower 
annulus. The gravel builds in the lower annulus adjacent the sump packer 
with the returns flowing through the lower zone screen and ported sub. The 
returns flow up the flowbore of the lower seal units and through the lower 
ball check valve. The returns then pass through the bypass apertures 
around the crossover ports and up the annulus. The returns thereafter flow 
out through the upper ported sub and up the upper annulus formed by the 
work string and outer casing. Upon completing the gravel pack of the lower 
production zone, fluids are reverse circulated down to the crossover 
ports. Fluid is then pumped down the annulus between the work string and 
casing, through the upper ported sub at the upper end of the seal units, 
down the annulus, and through the bypass apertures around the crossover 
ports. The lower ball check prevents the fluid from passing down into the 
flowbore of the lower seal units and directs the flow through upper ball 
check and flowbore to the surface. 
In gravel packing the upper production zone, the service tool is raised 
such that the crossover ports are adjacent the upper closing sleeve. Also, 
the seals on the seal units sealingly engage the first, second, and fourth 
seal bores. Circulation and reverse circulation occurs substantially as 
previously described with respect to the lower production zone. 
In a gravel pack operation for three or more production zones, upper and 
lower shifting tools are used with one of the shifting tools being in the 
service tool and the other in the wash pipe. The shifting tools on the 
service tool push the closing sleeves to the down or open position as they 
pass through the completion string. Then, the upper shifting tool is 
raised through the upper closing sleeve to pull the upper closing sleeve 
to its upper or closed position. Once the upper closing sleeve has been 
closed, the gravel pack ports are placed in position to pressure up the 
annulus and set the isolation packer. This procedure requires that the 
service tool be raised and then lowered back down to reopen the sleeve but 
not lower the upper shifting tool through the closing sleeve. This creates 
a lot of movement up and down to get the closing sleeve in the proper 
position. 
In a gravel pack operation for a dual zone, it is possible to use only one 
shifting tool. However, in utilizing only one shifting tool, it is 
necessary to space the shifting tool very close to the gravel pack ports 
such that the shifting tool can be raised through the closing sleeve to 
pull the sleeve closed and yet not raise the gravel pack ports so high 
that the gravel pack ports are moved above the seal bore of the isolation 
packer so as to prevent pressuring up to set the isolation packer. This 
requires a very short reciprocal motion thereby requiring that the service 
string be spaced out very accurately with respect to the completion 
string. Another problem with locating the closing sleeve and shifting tool 
so close to the gravel pack ports is that the gravel pack sand tends to 
get into and around the keys of the shifting tool, locking up the keys so 
that they will not function properly. Further, the use of a single 
shifting tool is useful for relatively shallow, straight wells. However, 
when gravel packing deep wells or highly deviated wells where the pipe 
making up the work string has high movement, the operator has difficulty 
knowing whether the gravel pack ports are properly positioned adjacent the 
closing sleeve. 
Another disadvantage of the prior art is that the prior art method and 
apparatus does not permit performing the gravel pack in a weight-down 
position which is preferred in the industry. The work string is made up of 
steel tubing which will contract and expand in the well, particularly when 
the work string is several thousand feet long. At such lengths, the steel 
stretches causing the lowermost end of the work string to move several 
feet within the well. This is particularly a problem in gravel packing 
operations when it is necessary to position the gravel pack ports 
accurately across from the closing sleeves. 
It is also advantageous to perform other operations, such as hydraulic 
fracturing, in a weight-down position. The work string extending from the 
top of the service tool to the surface has substantial movement during a 
fracturing or fracpac operation. The movement of the work string is even 
more exaggerated than during a gravel pack operation due to the thermal 
effects caused by the cool fracturing fluid being pumped down through the 
work string at a very high rate. This tends to cause shrinkage in the work 
string. Further, the work string tends to balloon due to the increased 
pressure within the work string which also causes the work string to 
shrink. These combined affects tend to shorten the work string 
substantially during the operation. 
Although a weight indicator is used at the surface to determine the amount 
of weight hanging off the crown block, the fact that the weight appears to 
be staying the same does not provide an indication as to whether the 
length of the work string is changing at its lower end. If the work string 
shrinks several feet, the gravel pack ports may be raised a distance so as 
to cause the gravel pack ports to be moved up into the packer seal bore 
and prematurely end the operation. 
Another problem during the frac pack operation is that the pumping of the 
fluid through the work string at a very high rate causes a vibration in 
the work string thereby causing it to move up and down. With a very long 
work string, this reciprocable motion may get very large causing it to 
bounce up and down within the well such that it may act like a spring. 
The present invention overcomes the deficiencies of the prior art. 
SUMMARY OF THE INVENTION 
The method and apparatus of the present invention for individually treating 
a plurality of production zones with one trip into the well includes a 
completion string having a plurality of sets of closing sleeves, indicator 
collars, and screens with an isolation packer disposed between each 
adjacent set. An inner service tool is disposed within the outer 
completion string and includes an upper and lower portion connected by a 
connection such as a pin and box or latch. Typically, the upper portion 
includes a cross-over tool and the lower portion includes a closing sleeve 
shifter and weight-down collet. The completion string and service tool are 
assembled by assembling an initial length of the outer completion string 
which does not include any closing sleeve or indicator collar. After the 
initial length of completion string is assembled, the lower portion of the 
service tool which includes the closing sleeve shifter and weight-down 
collet are assembled and inserted into the initial length of completion 
string. The remainder of the completion string is then assembled with all 
closing sleeves in the closed position. Upon completing the assembly of 
the completion string, the upper portion of the service tool is assembled 
and stabbed into the lower portion and connected thereto at the 
connection. Alternatively, the cross-over tool can be located in the lower 
portion and with lower portion initially suspended within the outer 
completion string by a latch. After the completion string is assembled 
within the well, a work string is attached by the latch to the lower 
portion and the lower portion is raised within the completion string. The 
latch is then removed from the lower portion and the sections of the upper 
portion are then assembled to the lower portion. This later method 
eliminates the need to leave the connection in the inner service tool. 
In treating multiple production zones, the lowermost isolation packer is 
set on the completion string and then the inner service tool is raised 
allowing the closing sleeve shifter to pass through the lowermost closing 
sleeve and the weight-down collet to pass through the lowermost indicator 
collar. The service tool is then lowered back down causing the closing 
sleeve shifter to open the closing sleeve and allowing the weight of the 
service tool and work string to be set down on the support shoulder of the 
indicator collar. The operator at the surface monitors the weight on the 
indicator collar and selectively adds or reduces weight on the indicator 
collar to maintain the crossover tool in position with the lowermost, now 
opened, closing sleeve. Upon completing the treatment of the lowermost 
production zone, the inner service tool is raised to the next uppermost 
production zone and the procedure repeated. 
One object of the present invention is to have the capability of gravel 
packing multiple zones in a multiple zone completion string with a single 
trip into the well of the service tool and also have the ability to set 
weight-down on the completion string during the treatment of the 
production zones. 
Another advantage is that only one closing sleeve shifter is required. 
Closing sleeve shifters have a tendency to get stuck within the completion 
string. Thus, it is advantageous to not only limit the number of shifters 
to a single closing sleeve shifter but also limit the movement of the 
closing sleeve shifter within the completion string such as raising and 
lowering the closing sleeve shifter to open and close various closing 
sleeves. The present invention provides a single closing sleeve shifter 
which only has limited movement within the completion string. 
Still another object of the present invention is to be able to perform a 
frac packing operation after the gravel packing operation and allow a 
substantial amount of the weight of the service tool and work string to be 
placed on the completion string to maintain the service tool in a 
predetermined position with respect to each of the multiple production 
zones and prevent the service tool from drifting during the movement of 
the work string associated with the high pressures caused by the 
fracturing operation and to prevent vibration of the service tool downhole 
causing the service tool to wear out. By allowing weight-down, the service 
tool will maintain its position to ensure that the crossover ports are 
properly aligned with the apertures through the closing sleeves for each 
of the multiple zones. 
Other objects and advantages of the invention will appear from the 
following description.

DESCRIPTION OF A PREFERRED EMBODIMENT 
Referring initially to FIG. 1, a completion string 10 is shown for a dual 
zone completion with a production packer 30 at its upper end having slips 
26 for supporting completion string 10 within an outer casing 18. Casing 
18 is disposed within a well having a plurality of production zones, such 
as lower zone 12 and upper zone 14 having perforations 13, 16, 
respectively, for the passage of hydrocarbons from zones 12, 14 into the 
annulus 24 formed between completion string 10 and outer casing 18. The 
completion string 10 includes a plurality of sets of tools with an 
isolation packer disposed between each set. A set of tools includes an 
upper seal bore, a closing sleeve, a lower seal bore, an indicator collar, 
and a plurality of screens. Thus there is an upper set for the upper zone 
and a lower set for the lower zone in a dual zone completion. 
The upper zone set of tools is disposed below production packer 30 and 
includes upper zone upper closing sleeve 32, an upper zone indicator 
collar 34, and an upper zone screens 36. An upper zone upper seal bore 38 
is disposed between production packer 30 and upper zone upper closing 
sleeve 32 and an upper zone lower seal bore 40 is disposed between upper 
zone upper closing sleeve 32 and upper zone screen 36. Pup extensions 42, 
44 extend between upper seal bore 38 and upper closing sleeve 32 and 
between lower seal bore 40 and indicator collar 34, respectively. 
An isolation packer 50 is disposed between the adjacent upper and lower 
zone sets of tools. The lower zone set includes a lower zone lower closing 
sleeve 52, a lower zone indicator collar 54, and lower zone screens 56 
being disposed below isolation packer 50. A lower zone upper seal bore 58 
is disposed adjacent isolation packer 50 and a lower zone lower seal bore 
60 is disposed between lower zone lower closing sleeve 52 and lower zone 
indicator collar 54. Pup extensions 62, 64 extend between isolation packer 
50 and lower zone lower closing sleeve 52 and between lower zone lower 
seal bore 60 and lower zone indicator collar 54, respectively. The lower 
terminal end of completion string 10 includes a seal assembly 66 which is 
received by a sump packer 70. 
It should be appreciated that although the completion string 20 shown in 
FIGS. 1-3 includes only upper and lower zone sets of tools with an 
isolation packer disposed therebetween, additional sets of tools may be 
included with the completion string for gravel packing or otherwise 
treating additional production zones and that the present invention is not 
limited to treating only two production zones. As additional sets of tools 
are added to the completion string 10, an additional isolation packer is 
disposed between each additional adjacent set. The present invention may 
be used to complete any number of production zones with one trip into the 
well. 
Referring now to FIG. 2, a service tool 20 includes an upper portion, 
generally designated 28, and a lower portion, generally designated 90. A 
setting tool 72 and work string 15 are disposed at the upper terminal end 
of upper portion 28 with an inner center tube 74 and a plurality of seal 
units 76 forming an outer conduit 78. Inner center tube 74 and outer 
conduit 78 form a fluid passageway 80 which extends from setting tool 72 
at its upper end to a crossover tool 130 at its lower end. Seal units 76 
include an upper set of seal units 84 adjacent setting tool 72, a medial 
set of seal units 86 above crossover tool 130, and a lower set of seal 
units 88 which extends downwardly from crossover tool 130. Lower portion 
90 is connected to upper portion 28 at the lower terminal end of lower 
seal units 88 by a connection means 95. Connection means 95 includes a 
downwardly projecting pin member 92 on the lower terminal end of upper 
portion 28 and a receptacle or box 94 disposed at the upper terminal end 
of lower portion 90. The connection means 95 is described in further 
detail below with respect to FIG. 4. Lower portion 90 is a wash pipe which 
includes a closing sleeve shifter 96, a weight-down collet 100, a ported 
pipe 98, and a lower ball check valve 102 disposed in the lower terminal 
end of lower portion 90. 
Service tool 20 further includes an upper spring loaded ball check 85 
provided at the lower terminal end of center tube 74 to prevent the 
downward flow of fluids through the flowbore 75 of center tube 74. A lower 
check valve 87 is provided adjacent the upper end of lower seal unit 88 to 
prevent the downward flow of fluids in fluid passageway 80 and into the 
flowbore 89 formed by those lower seal units 88 which are disposed below 
crossover tool 130. 
Alternatively, cross-over tool 130 may be a part of the lower portion 90 
with the connection means 95 disposed above cross-over 130 between 
adjacent sections of inner center tube 74 and outer conduit 78 between the 
upper set of seal units 84 and the medial set of seal units 86. Connection 
means 95 may be in the form of a latch (not shown) for suspending the 
lower portion 90 within outer completion string 10 at its lower end. A 
work string is attachable to the latch for raising the lower portion 90 
within the completion string 10. The latch is removable so that after the 
lower portion is raised, the latch may be removed for connecting the 
sections forming the upper portion 28. 
Referring now to FIG. 3, service tool 20 is shown disposed within 
completion string 10. In the position shown in FIG. 3, all of the closing 
sleeves 32, 52, are shown in the closed position. The closing sleeve 
shifter 96 and weight-down collet 100 are disposed below all of the 
closing sleeves 32, 52 and indicator collars 34, 54. Work string 15 forms 
an annulus 23 with outer casing 18 for fluid communicating with the 
surface. 
Referring now to FIG. 4, the connection means 95 connects the upper portion 
28 of service tool 20 to the lower portion 90 of service tool 20. The 
connection means 95 includes a pin member 92 threaded at 104 to the lower 
terminal end of seal units 88 and a receptacle or box 94 disposed on the 
upper terminal of wash pipe 98. Box 94 includes an inwardly projecting 
annular shoulder 106 which engages the nose 108 of pin member 92. Pin 
member 92 includes a double male threaded connector member 110 threaded at 
104 and threaded at 112 to nose member 108. Connector member 110 includes 
a reduced diameter portion 114 on which is housed a seal member 116 which 
sealingly engages the inside diameter of box member 94. The upper terminal 
end of box 94 includes internal threads 118 which engage external threads 
122 on a split ring 120 housed on pin member 92. Upon assembly, pin member 
92 is received within box 94 and rotated to threadingly engage threads 
118, 122 on box 94 and ring 120, respectively. 
Also shown in FIG. 4 is lower zone indicator collar 54. Indicator collar 54 
includes a reduced diameter portion 55 forming an upwardly facing support 
shoulder 57 and a downwardly facing cam shoulder 59. Indicator collar 54 
is adapted to support the load shoulder 222 on weight-down collet 100, as 
hereinafter described, so as to provide an indication of the position of 
the service tool 20 with respect to completion string 10. It should be 
appreciated that upper zone indicator collar 34 is substantially the same 
as lower zone indicator collar 54. 
Referring now to FIG. 5, a crossover tool 130 is shown which includes 
crossover ports 82 for the passage of the gravel slurry through the wall 
of service tool 20. Crossover tool 130 also includes a protective sleeve 
132, preferably made of tungsten carbide, which is secured within 
crossover tool 130 by a set screw 134 which extends laterally through 
protective sleeve 132 and into the tubular body 136 of crossover tool 130. 
Protective sleeve 132 extends axially upward past the crossover ports 82 
and crossover tool 130. The upper end of sleeve 132 includes a transition 
surface 138. Sleeve 132 includes a plurality of openings or flow ports 140 
which are circumferentially aligned with the crossover ports 82. Further 
details of the crossover tool 130 are disclosed in U.S. patent application 
Ser. No. 08/529,769, filed Sep. 18, 1995 and entitled "Abrasive Slurry 
Delivery Apparatus and Methods of Using Same", incorporated herein by 
reference. 
Also shown on FIG. 5 is the upper spring loaded ball check 85. Ball check 
85 includes a generally cylindrical body 142 having an inwardly extending 
annular seat 144 which supports a sphere 146. An inner member 148 is 
biased downwardly by spring 150 against sphere 146. Ball check 85 prevents 
downward flow through the flowbore 75 of inner center tube 74 but becomes 
unseated upon the upward flow of well fluids having sufficient pressure to 
compress spring 150 and allow fluid flow around sphere 146 as it becomes 
unseated from seat 144. 
Referring now to FIG. 6, there is shown lower zone, upper closing sleeve 
52. Closing sleeve 52 is identical in operation to upper zone, closing 
sleeve 32. Closing sleeve 52 includes a tubular body 152 having a 
plurality of apertures or flow ports 154 circumferentially spaced around 
body 152. A closure member 156 is reciprocably disposed on tubular body 
152. Closure member 156 includes a plurality of upwardly and downwardly 
projecting fingers 166, 167, respectively, and upper and lower sets of 
sealing members 160, 162, respectively, for sealingly engaging the inside 
diameter of tubular body 152 for closing and sealing ports 154. In the 
upper and closed position of closure member 156, the upper terminal ends 
of upper fingers 166 engage a release ring 158. Release ring 158 is fluted 
for fluid flow. In the lower and open position, the lower fingers 167 pass 
over annular detent 168 allowing ports 154 to be open for fluid flow. The 
lower end of closure member 156 abuts detent 168. Closure member 156 
further includes an inner enlarged diameter channel 172 for cooperatively 
receiving a latch member 174 on closing sleeve shifter 96 hereinafter 
described. 
Referring now to FIG. 7, there is shown closing sleeve shifter 96. Closing 
sleeve shifter 96 includes a tubular body 170 having threads 174, 175 on 
each end for threaded engagement in wash pipe 90. Tubular body 170 
includes a reduced diameter portion 176 for receiving a plurality of latch 
members 180 which are biased outwardly by spring members 178. Latch 
members 180 are maintained within the channel formed by reduced diameter 
176 by retainer 182 at the upper end and retainer 184 at the lower end, 
retainers 182, 184 being attached to tubular body 170. Latch members 180 
include tapered shoulders 186, 188 for camming latch members 180 inwardly 
upon engaging a shoulder on completion string 10. Closing sleeve shifter 
96 is located below connection means 95 on the lower portion 90 of service 
tool 20. 
Referring now to FIG. 8, there is shown weight-down collet 100. Weight-down 
collet 100 includes a tubular body 190 having an enlarged diameter annular 
boss 192 forming a downwardly facing shoulder 208 and an upwardly facing 
shoulder 212. Tubular member 190 is threaded at 194 at its lower end and 
at 196 at its upper end for connection within lower portion 90. A sliding 
sleeve 200 is reciprocably and slidably mounted around tubular body 190 
and includes an enlarged diameter portion forming an inner annular channel 
202 which, in the assembled position, receives annular boss 192. The lower 
end of body 190 is formed by a plurality of fingers 195, having slots 
therebetween, allowing fingers 195 to be bowed or collapsed inwardly. 
Sliding sleeve 200 includes an inwardly directed flange 204 at its lower 
terminal end forming an upwardly facing annular shoulder 206 for abutting 
engagement with the downwardly facing shoulder 208 formed by annular boss 
192. A collar 209 is threaded on the upper terminal end of sliding sleeve 
200 thereby forming a downwardly facing annular shoulder 210 adapted for 
engaging upwardly facing annular shoulder 212 on the upper end of annular 
boss 192. Adjacent the lower terminal end of sliding sleeve 200 is an 
outwardly extending annular shoulder 220 forming a downwardly facing 
annular load shoulder 222 and an upwardly facing and downwardly and 
outwardly tapering shoulder 224 at its upper end. The threaded connections 
at 194, 196 form shoulders 226, 228. Sliding sleeve 200 is free to 
slidingly reciprocate on annular boss 192 of tubular body 190. 
Referring now to FIGS. 9 and 10, the weight-down collet 100 is designed so 
that it may pass upwardly through an inwardly projecting restriction on 
completion string 10, such as the reduced diameter portion 55 of indicator 
collars 34, 54, but not past back downwardly through such a restriction so 
that a predetermined portion of the weight of service string 20 and work 
string 15 may be supported by the support shoulder 57 of indicator collars 
34, 54. In operation, sliding sleeve 200 has an upper position shown in 
FIG. 10 whereby upwardly facing annular shoulder 206 on sleeve 200 
abuttingly engages downwardly facing annular shoulder 208 on boss 192. In 
this uppermost position, annular boss 192 is aligned directly behind 
fingers 195 on which is disposed annular shoulder 220 with downwardly 
facing load shoulder 222. Annular boss 192 prevents fingers 195 from being 
bowed or collapsed inwardly thereby allowing load shoulder 222 to engage 
support shoulder 57 on reduced diameter portion 55 of indicator collars 
34, 54. In the lowermost position shown in FIG. 9, fingers 195 are 
positioned over the reduced diameter portion 191 of tubular body 190 
thereby allowing the fingers 195 to collapse inwardly upon annular 
shoulder 220 engaging a restriction on completion string 10 as service 
tool 20 passes upwardly through completion string 10. However, once the 
weight-down collet 100 has passed through the reduced diameter portion 55 
of one of the indicator collars 34, 54, the sleeve 200 on weight-down 
collet 100 moves to its uppermost position as shown in FIG. 10 whereby 
annular boss on 192 on body 190 maintains the fingers 195 in their 
outermost position such that part of the weight of the service tool 20 and 
work string 15 may be supported by the completion string 10. 
The weight-down collet 100, like closing sleeve shifter 96, is disposed on 
the lower portion 90 of service tool 20 below connection means 95. Since 
the weight-down collet 100 cannot be lowered through one of the indicator 
collars 34, 54, it must be disposed within completion string 10 prior to 
one of the indicator collars 34, 54, being assembled within the well on 
completion string 10. Thus, the weight-down collet 100 is placed inside 
the completion string 10 prior to any of the indicator collars 34, 54 or 
other restrictions within the flowbore 17 of the completion string 10, 
being assembled within the completion string 10. 
It should be appreciated that the present invention is not limited to a 
single position weight-down collet which only allows the operator to raise 
the weight-down collet up through an indicator collar once and then set 
back down. A multi-position indicator collet such as the multi-position 
indicator collet shown and described in U.S. Pat. No. 4,722,392, issued 
Feb. 2, 1988, incorporated herein by reference, may be used in place of 
the single position weight-down collet. The single position weight-down 
collet is preferred since the single position weight-down collet can be 
used to support more weight than an unsupported multi-position indicator 
collet. In particular, during a frac pack operation, a large amount of 
weight may need to be supported by the weight-down collet to withstand the 
amount of tubing movement caused by the frac pack operation so as to 
maintain the service string 20 in position with respect to completion 
string 10. Substantial loads such as up to 100,000 pounds may be required 
to prevent the weight-down collet from being lifted off of the indicator 
collar. A single position weight-down collet may support up to 100,000 
pounds of weight. The single position weight-down collet will not pass 
down through the indicator collar unless its mechanical limits are 
exceeded causing it to break. However, it is impractical to use a 
multi-position indicator collet which would support a substantial load, 
such as 100,000 pounds, because it would require that a large percentage 
of that 100,000 pounds be applied to raise the multi-position indicator 
collet up through a restriction in the completion string. 
Prior to the assembly of the multi-zone gravel pack assembly, the sump 
packer is run into the well on a wire line and set at a predetermined 
location prior to assembling the completion string 10 and service tool 20. 
The completion string 10 and service tool 20 are then assembled on the rig 
floor at the surface. The completion string 10 is assembled by inserting 
completion string 10 into the well at the surface, section by section, 
starting at the lower end of the completion string. As each section is 
added to the completion string 10, the top of the string is supported at 
the wellhead by slips which are set around the completion string 10. As 
distinguished from the prior art, prior to attaching that section of the 
completion string 10 which includes the lowermost closing sleeve, such as 
lower closing sleeve 52, and lowermost indicator collar, such as lower 
indicator collar 54, the lower portion 90 of the service tool 20 is 
assembled and lowered into that portion of the completion string 10 which 
extends below the lowermost closing sleeve and indicator collar. The lower 
portion 90 of the service tool 20 is either supported by a restriction in 
the sealing assembly 66 on the lower end of completion string 10 or by a 
retractable "no-go" such as a reverse indicator. The remaining sections of 
the completion string 10 are then attached until the completion string 10 
is assembled up to the production packer 30 which is connected after 
completing the assembly of the completion string 10 and service tool 20. 
After the completion string 10 is assembled, the upper portion 28 of 
service tool 20 is assembled beginning with lower seal units 88 having pin 
member 92 at its terminal end. After lower seal units 88 have been 
assembled, the outer concentric conduit 78 of the crossover tool 130 is 
assembled and lowered into completion string 10 and then the inner smaller 
center tube 74 is lowered into outer conduit 78 to complete the assembly 
of the upper portion 28 of service tool 20. 
Upon completing the assembly of upper portion 28, pin 92 on its lower end 
is inserted into receptacle or box 94 on the upper terminal end of lower 
portion 90. Upper portion 28 is then inserted and latched into lower 
portion 90 to connect pin and box 92, 94, respectively, to form connection 
means 95. 
Alternatively, if the cross-over tool 130 is disposed in the lower portion 
90, the lower portion 90 includes a releasable latch at its upper end. The 
lower portion 90 with latch is lowered and suspended by the latch at the 
lower end of outer completion string 10 prior to attaching that section of 
completion string 10 which includes the lowermost closing sleeve and 
lowermost indicator collar. The remaining sections of the completion 
string 10 are then attached until the completion string 10 is fully 
assembled. A work string is then lowered into inner service string 20 and 
attached to the latch at the upper end of lower portion 90. The lower 
portion 90 is then raised until the lower portion of service string 20 is 
aligned and supported within completion string 10. The latch is then 
removed so as to eliminate leaving the connection means in the well and 
the remaining sections of the upper portion 28 are assembled to complete 
the assembly of inner service string 28 as previously described. 
By locating the closing sleeve shifter 96 in lower portion 90 and inserting 
lower portion 90 into the lower portion of completion string 10 as 
completion string 10 is assembled, the lower portion 90 with closing 
sleeve shifter 96 is not lowered through the assembled completion string 
10 so as to open all the closing sleeves as it passes down the completion 
string. Thus, the completion string 10 may be assembled with all of the 
closing sleeves, such as sleeves 32, 52, in the closed position and the 
service tool 20 may be assembled and disposed within completion string 10 
without passing the closing sleeve shifter 96 downwardly past the closing 
sleeves 32, 52 moving them to the open position as in the prior art. 
Once both the completion string 10 and service tool 20 have been assembled 
up to the production packer assembly and are suspended at the surface, the 
completion string 10 and service tool 20 are raised for connection with 
the production packer 30 and setting tool 72. Seal units 84, 86 and 88 on 
service tool 20 are located with respect to seal bores 38, 40, 58 and 60 
such that well fluids are allowed to pass into the annular area 65 best 
shown in FIG. 3 as the assembly of the completion string 10 and service 
tool 20 are lowered into the casing 18. If the annulus is sealed between 
upper and lower seal bores 58, 60, ambient pressure would become trapped 
in this annular space creating a pressure differential which could cause 
the pipes to collapse under hydrostatic pressure. Tools are positioned 
with seals 86 below seal bore 58 to prevent this from happening. The 
completion string 10 and service tool 20 are lowered as a unit into the 
well and supported on sump packer 70. At that time, upper and lower 
screens 36, 56 are located adjacent each of the upper and lower production 
zones 14, 12, respectively. A sphere (not shown) is then dropped through 
work string 15 and production packer 30 is set by pressuring up the work 
string 15. Upon setting production packer 30, slips 26 are also set such 
that the completion string 20 is supported and sealed within outer casing 
18. 
The setting tool 72 with service tool 20 is then disconnected from outer 
completion string 10. Once the cross over ports 82 are positioned within 
the pup extension 62 and prior to opening lower zone lower closing sleeve 
52, the flowbore 75 of work string 15 is again pressured up to set 
isolation packer 50. Service tool 20 is then picked up and raised within 
completion string 10 to begin the treatment of production zones 12, 14, 
such as by gravel packing. In raising service tool 20, closing sleeve 
shifter 96 passes through lower zone lower closing sleeve 52 and 
weight-down collet 100 passes through lower zone indicator collar 54 with 
fingers 195 on collet 100 collapsing inwardly so as to allow shoulder 220 
to pass beneath reduced diameter portion 55 of lower zone indicator collar 
54. Service tool 20 is then moved back downwardly with latch members 180 
engaging closure member 156 of sleeve 52 and moving closure member 156 to 
its lower position thereby opening ports 154 and allowing fluid 
communication with annulus 24. Also upon lowering the service tool 20 back 
down, load shoulder 222 of weight-down collet 100 is engaged and supported 
by support shoulder 57 on indicator collar 54. Further, the seals on 
setting tool 72 no longer engage upper zone upper seal bore 38 adjacent 
production packer 30 thereby opening a ported sub for communication 
between upper annulus 23 and fluid passageway 80 formed by inner center 
tube 74 and outer conduit 78. In this position, the upper set of seal 
units 84, the medial set of seal units 86, and the lower set of seal units 
88 sealingly engage upper zone upper seal bore 38, lower zone upper seal 
bore 58, and lower zone lower seal bore 60, respectively. Crossover ports 
82 of crossover tool 130 are now adjacent the apertures 154 through lower 
zone lower closing sleeve 52 which had been previously been opened by 
closing sleeve shifter 96. No seals or seal bores are provided below lower 
zone screen 56. 
The weight supported by load shoulder 57 on indicator collar 54 is 
determined by a weight indicator (not shown) at the surface which 
indicates the amount of weight of the work string 15 and service tool 10 
which is supported by the crown block on the drilling rig at the surface. 
The weight indicator provides the operator a means of determining the 
location of the service tool 20 with respect to the completion string 10 
since as long as the indicator collar is supporting weight from the 
service tool 20, the gravel pack ports 82 of crossover tool 130 are 
properly positioned adjacent the apertures 154 in the closing sleeve. The 
weight applied to the tool 20 changes as the length of the string changes. 
When the length of the work string 15 shortens, load is removed from the 
weight-down collet 100 which indicates that the work string 15 is 
shrinking. This tendency for the working string 15 to move upwardly 
reduces the load on the weight-down collet 100. If the work string 15 
shortens too much as indicated by the weight indicator, a lowering of the 
work string 15 applies additional weight on service tool 20 to compensate 
for the shrinkage in length. Additional weight may be placed on the 
weight-down collet 100 by slacking off on the work string 15 thus allowing 
the work string 15 to be lowered until the weight indicator indicates that 
there is again a predetermined amount of weight on the weight-down collet 
100. By slacking off on the work string 15, weight is transferred from the 
crown block on the rig at the surface to the support shoulder 57 on 
indicator collar 54 on completion string 10 downhole. 
Although a gravel packing operation is being described, it should be 
appreciated that the present invention may be used for other methods of 
treating the well such as a fracturing operation. Treating the well in a 
weight-down position is particularly important in a fracturing operation 
since the work string 15 can shrink several feet during such an operation. 
In a prior art operation, if the work string 15 were to move upwardly 
several feet, it would be possible for the gravel pack ports and the 
service tool to be raised into the seal bore above the isolation packer 
thereby prematurely ending the operation. 
In gravel packing the lower zone 12, gravel slurry is pumped down the 
flowbore 75 formed by work string 15 and center tube 74. The ball check 
valve 85 directs the gravel through crossover ports 82 and through the 
opened apertures 154 in lower closing sleeve 52 and into lower annulus 24. 
The gravel builds in lower annulus 24 adjacent sump packer 70 with the 
returns flowing through lower zone screen 56 and ported sub 98. The 
returns flow up flowbore 89 of lower seal units 88 and through lower ball 
check valve 87. The returns then pass through the bypass apertures in 
crossover tool 130 around crossover ports 82 and up fluid passageway 80. 
The returns then flow out through the open ported sub adjacent the setting 
tool 72 and up upper annulus 23 formed by work string 15 and casing string 
18. Upon completing the gravel pack of the lower production zone 12, 
fluids are reverse circulated down to the crossover ports 82. Fluid is 
pumped down the annulus 23 between work string 15 and casing 18, through 
the ported sub and then flows up through upper ball check 85 and flowbore 
75 to the surface. 
The extension of the fluid passageway 80, formed by upper seal units 38 and 
center tube 74 between crossover ports 82 to a point above production 
packer 30, prevents any returns from flowing into an upper production 
zone. Further, this fluid passageway 80 and upper ball check 85 at the 
lower end of center tube 74 allow reverse flow through the service tool 20 
without any requirement for a wash string from the surface. 
In gravel packing the upper production zone 14, the service tool 20 is 
raised within completion string 10 and then moved downwardly as previously 
described. In particular, closing sleeve shifter 96 latches with upper 
zone, upper closing sleeve 32 and moves it to its lower open position. 
Further, weight-down collet 100 allows weight to be set on work string 15 
to ensure that crossover ports 82 are properly positioned adjacent the 
apertures in upper zone upper closing sleeve 32. In this position, the 
upper set of seal units 84, the medial set of seal units 86, and the lower 
set of seal units 88 sealingly engage upper zone upper seal bore 38, upper 
zone lower seal bore 40, and lower zone lower seal bore 60. The gravel 
slurry is then pumped down work string 15 and out through ports 82 and 
closing sleeve 32 to gravel pack upper zone 14. Circulation and reverse 
circulation occurs as previously described with respect to the gravel 
packing of lower production zone 12. 
As can be appreciated, the indicator collars, such as collars 34, 54, are 
set at a predetermined position below each production zone, 12, 14, 
respectively to ensure that the gravel pack ports 82 are positioned 
adjacent the appropriate closing sleeve. The distance between the closing 
sleeve and indicator collar 100 in each set has a predetermined relative 
distance between the gravel pack ports 82 and the weight-down collet 100 
since these must be spaced relative to each other. This allows the gravel 
pack operation to be performed in a weight-down position as previously 
described. 
The weight-down collet 100 allows the gravel pack ports 82 to be very 
accurately positioned adjacent the closing sleeve. Further, the 
weight-down position ensures that the gravel pack ports 82 on the service 
tool 20 stay properly aligned adjacent with the closing sleeve. The 
weight-down position is particularly important because it allows the 
operator at the surface to know that the gravel pack ports 82 remain in 
the aligned position with the closing sleeve in spite of any movement of 
the work string. 
Although the present method and apparatus have been described for 
completing a dual zone, the present invention may be used to treat any 
number of production zones with one trip into the well. The isolation of 
the upper production zones by the extension of the upper seal units and 
center tube 74 above production packer 30 allows the production zones to 
be gravel packed in any sequence, i.e. the production zones do not have to 
be gravel packed beginning with the lower production zone and then each 
successive zone above the lower zone. Additional sets of tools are added 
for each production zone, namely an upper seal bore, a closing sleeve, a 
lower seal bore, an indicator collar, and production screens with an 
isolation packer between adjacent sets. Therefore, in a multi-zone 
operation having more than three production zones, multiple isolation 
packers are used. Where multiple isolation packers are used, the service 
tool 20 is raised up the completion string 10 and each isolation packer is 
set as the service tool 20 is moved up hole. With all of the closing 
sleeves run in the closed position, each of the isolation packers can be 
set and subsequently opened as needed by raising the closing sleeve 
shifter 96 upward through an individual closing sleeve and then setting 
back down to open the closing sleeve. 
Although a single position weight-down collet requires that the production 
zones be treated beginning with the lowermost zone and moving upwards, a 
multi-position weight-down collet may be used which allows the method and 
apparatus of the present invention to treat or produce the individual 
production zones in any order. In doing so, the closing sleeve shifter 96 
is raised upwardly to set each of the isolation packers and then lowered 
back downwardly to open the closing sleeve for the particular production 
zone to be treated or produced. At that time, it does not make any 
difference that the closing sleeve shifter passes downwardly through and 
opens a closing sleeve since the isolation packers at that time will 
already have been set. 
While a preferred embodiment of the invention has been shown and described, 
modifications thereof can be made by one skilled in the art without 
departing from the spirit of the invention.