Method for casing a wellbore

Casing is installed in a well in a folded collapsed condition by uncoiling it from a reel. Two strings of tubing extend continuously through the collapsed casing. One of the strings of tubing is connected to a cement shoe at the lower end of the casing. An opening tool is located above the cement shoe and includes a piston. The other string of tubing extends to a pressure chamber that is between the piston and the cement shoe. After the casing is lowered with a running tool to the desired depth, cement is pumped down the first string of tubing, which flows back up the annulus surrounding the casing. A liquid is then pumped down the second string of tubing into the pressure chamber, causing the piston to push the opening head upward relative to the casing and the strings of tubing. The forming head opens the casing from the collapsed condition into a cylindrical configuration. The running tool retrieves the strings of tubing, opening tool and piston at the conclusion of the opening process.

TECHNICAL FIELD 
This invention relates in general to installing well casing in oil and gas 
wells and in particular to a method involving fabricating and collapsing 
casing, running the collapsed casing into the well and opening the casing 
into a cylindrical configuration. 
BACKGROUND ART 
Oil and gas wells are typically drilled by installing a conductor pipe to 
first depth, then drilling the well to a second depth. A string of casing 
is made up by coupling together sections of pipe, each being about forty 
feet long, and lowering the string inside the conductor pipe in a nested 
arrangement. Cement is then pumped down the casing which flows back up the 
annulus between the casing and the open borehole. Drilling is resumed to a 
third depth and the process is repeated with another smaller diameter 
nested casing. An even smaller diameter string of casing may be installed 
at a fourth depth. 
These casings serve to support the borehole wall and to prevent undesired 
outflow of drilling fluid into the formation or inflow of fluid from the 
formation into the borehole from strata other than the target production 
strata. The nested arrangement requires a relative large borehole at the 
upper part of the wellbore due to the thickness of casing couplings and 
also due to the minimum clearance necessary between casing to displace 
cement in the annulus space. 
Larger boreholes are more costly to drill since they require larger drill 
bits, more mud, and more cuttings disposal. Also, a larger diameter pipe 
has a lower pressure rating for the same wall thickness than a smaller 
diameter pipe, in consequence each of the casings has to cover the 
previous one up to the wellhead to enhance the pressure capability as the 
well goes deeper. Also conventional casing requires a derrick to make-up 
the pipe sections and lower the casing string into the well. Derricks are 
big and costly to move, and running casing in forty foot sections is time 
consuming. 
Liners are employed in some wells. A liner is similar to a casing, however, 
rather than extending completely to the surface wellhead, the upper end of 
the liner is suspended on the lower end of the previous string. Liners 
still must be run by making-up pipe sections together and are employed 
usually to extend in limited lengths from only the smallest diameter full 
length casing installed. 
Coil tubing units permit one to rapidly run a continuous metallic tubing 
into a well. The tubing is plastically coiled on large reels. A pushing 
mechanism straightens up the tubing and lowers it into the well as it is 
uncoiled from the reel. Coil tubing is used to circulate fluids into wells 
for various purposes. However, it is seldom used to serve as casing due to 
its small diameter. Coil tubing is smaller in diameter than typical 
casings, which have usually a minimum diameter of five inches. It would 
require a large reel to be able to coil several thousand feet of metallic 
casing of five inches in diameter or larger. 
DISCLOSURE OF INVENTION 
In this invention, a metal strip plate is formed in a generally tubular 
configuration, and welded longitudinally with at least one string of 
continuous tubing inserted during the manufacturing process. The casing is 
then collapsed with the tubing located therein and wound on a small reel 
due to its small height by comparison to its nominal diameter. The upper 
and lower end portions of the casings are formed in a somewhat cylindrical 
configuration. An opening tool is located in the lower end cylindrical 
portion. The opening tool has a piston and a conical forming head located 
above the piston. A pressure chamber is created below the piston in the 
lower end portion of the casing. 
The casing is deployed from the reel and folded in a horseshoe shape prior 
to entering the well. When the casing has reached the proper depth, a 
fluid is pumped down the tubing into the pressure chamber to open the 
casing into a cylindrical shape. The fluid pressure acts against the 
piston to push the opening tool upward. This causes the head of the 
opening tool to form the casing from the collapsed/folded configuration 
into a cylindrical configuration. The forming tool and the tubing are then 
pulled from the casing. 
Preferably, two strings of tubing are installed in the casing while it is 
being manufactured. One of the strings of tubing serves to pump a cement 
slurry down through a cement shoe located at the lower end of the casing. 
The cement flows back up the annulus surrounding the casing to cement the 
casing in place. Then fluid is pumped down the other string of tubing to 
open the casing. 
Also after the opening tool reaches the upper end of the casing, a forging 
tool is used to expand the upper end cylindrical portion of the casing 
into a metal-to-metal sealing engagement with the lower end of the 
previously cased section of the well. In the preferred embodiment, this 
involves releasing the running tool from the upper end of the casing after 
the collapsed portion of the casing has been expanded, then lowering the 
forging tool located above the running tool into the casing. Fluid is then 
pumped down to radially forge the upper end of the casing into engagement 
with the lower end of the previous one. 
The opening tool includes a forming head with a conical body with flutes. 
Balls roll along the flutes in rolling engagement with the casing wall as 
it is being opened to a cylindrical configuration. The balls force the 
opening of the casing as they roll along the flutes. The balls roll from 
the flutes into a lower ball passage, an axial passage, into an upper 
passage, and back into the flutes in a continuous cycle.

BEST MODE FOR CARRYING OUT THE INVENTION 
Referring to FIGS. 1A-1D, the well illustrated has a cased section 11 which 
has already been cemented in place and an open hole section 13 which 
extends below cased section 11 to the target depth. A continuous string of 
casing 15 according to the invention is shown in place in the well with a 
lower end portion 15a at the lower end of the well open hole section 13. 
Casing 15 has an intermediate portion 15b that extends from the lower end 
portion upward, typically several thousand feet, to an upper end portion 
15c. Upper end portion 15c overlaps the lower portion of cased section 11. 
Casing lower and upper end portions 15a, 15c each are somewhat cylindrical 
with axially extending corrugations 17 as shown in FIG. 5. Corrugations 17 
are straight axially extending channels on both the inner and outer 
diameters of casing, providing inward protruding valleys 17a alternating 
with outward protruding peaks 17b. Intermediate portion 15b, shown in FIG. 
4, is collapsed and folded, having a bight 18 that curves inward and 
touches the opposite side, which is generally arcuate when lowered into 
the wellbore. 
Referring to FIG. 1D, a cement shoe 19 is located at the lower end of 
casing lower end portion 15a. Cement shoe 19 provides an end cap for 
casing 15 and is made of drillable material with a cementing port 20 
extending axially through it. A metal stinger 21 engages sealingly into 
the upper portion of cementing port 20. Stinger 21 is a tubular member 
having a conduit 23 for pumping down a cement slurry through cementing 
port 20 which flow back up the annulus space surrounding the casing 15, as 
indicated by the arrows. Stinger 21 has also some flow ports 25 which are 
isolated from conduit 23 and lead to the exterior of stinger 21. 
A cement slurry tubing 27 extends continuously through casing 15, and has 
its lower end coupled to stinger 21 for connecting with conduit 23. 
Similarly, a fill-up tubing 29 extends continuously through casing 15 and 
has its lower end coupled to stinger 21 for delivering fluid to ports 25. 
Tubing strings 27, 29 are conventional metal coiled tubing strings of 
about one inch in diameter. 
An opening tool 31 is housed in casing lower end portion 15a, shown in FIG. 
1C, above stinger 21. Opening tool 31 includes on its lower end a piston 
33. Piston 33 is an elastomeric cup sliding seal which has straight 
axially extending grooves on its exterior for meshing with the 
corrugations 17 of casing lower end portion 15a. A pressure chamber 35 is 
located in the space surrounding stinger 21 above cement shoe 19 and below 
piston 33. In the running-in position, as shown in FIG. 1D, pressure 
chamber 35 is at its minimum volume. A cylindrical metal piston head 37 
extends upward from piston 33. Piston head 37 is movable within a sleeve 
48 which has a smaller outer diameter than the inner diameter of casing 
lower end portion 15a at valleys 17a. 
Opening tool 31 has a tapered or conical forming head 39 that tapers from a 
smaller diameter upper end to a larger diameter at lower end. Head 39 has 
vertical flutes 41 which align with valleys 17a, as shown in FIG. 5. A 
plurality of balls 43 roll down flutes 41 of head 39. Balls 43 are movable 
through two axial passages 45, a plurality of lower lateral passages 47, 
and a plurality of upper lateral passages 49. Piston head 37 initially is 
in a lower position within sleeve 48 of head 39, providing a chamber for a 
number of balls 43 as shown in FIG. 1C. When piston head 37 is pushed 
upward, until it will enter in contact with a flange 50 of head 39 as 
shown in FIG. 8A, it will push the balls 43 upward through axial passages 
45. Balls 43 move outward on upper ball passages 49, down flutes 41, and 
back inward in lower ball passages 47 to axial passages 45 in a continuous 
cycle as head 39 moves upward in casing 15. 
Referring again to FIG. 1C, opening tool 31 has a cylindrical top end 51 
which has an outer diameter equal to the minimum inner diameter of casing 
lower end portion 15a, which is measured at valleys 17a. Balls 43 will 
engage valleys 17a when contained in flutes 41 and bend the casing wall to 
line up with expanded peaks 17b. While at the upper end of flutes 41, the 
diameter from one ball 43 to an opposite ball 43 is substantially equal to 
the diameter between valleys 17a. When balls 43 are at the lower ends of 
flutes 41, as shown in FIG. 8A, the outer diameter of forming tool 31 
measured from one ball 43 to an opposite ball 43 at the lower ends of 
flute 41 is greater than the minimum inner diameter of casing lower end 
portion 15c. Consequently, balls 43 push valleys 17a outward to open, in a 
smooth circular configuration, the upper end of casing lower portion 15a 
as opening tool 31 moves upward. 
Due to the relative stiffness of the casing metal wall, the intermediate 
portion 15b is opened from its folded configuration ahead of the opening 
tool 31, and the contact between the inner wall and the opening tool 31 is 
made only by the balls 43 rolling on flutes 41 of the conical forming head 
39. 
Referring to FIG. 1B, a running tool 55 is located at the top of casing 
upper end portion 15c. Running tool 55 is a tubular member which has an 
outer sleeve 56. The exterior of outer sleeve 56 has vertical grooves 58 
between vertical bands 58a. Outer sleeve has a set of threads on bands 58a 
which engages a mating set of threads 57 formed on valleys 17a in the 
upper inside end of casing upper end portion 15c. Because of corrugations 
17 and grooves 58, threads 57 will be discontinuous and located only on 
the valleys 17a. 
Outer sleeve 56 is supported by an inner body 59, which has a smooth 
cylindrical exterior. Outer sleeve 56 has a J-pin 61 that protrudes 
inwardly into an elongated U-shaped J-slot 63 formed in outer body 59. 
J-slot 63 has a first leg 63a and a parallel second leg 63a joined at the 
bottom. During running-in of casing 15, J-pin 61 will be at the upper end 
of the first leg 63a and maintained in this position by the weight of the 
casing 15 hanging on the running string connected to the inner body 59. 
After casing intermediate portion 15b has been opened, the weight of the 
casing 15 is supported by the numerous contacts with the inner wall of the 
borehole. After opening has been completed, the operator will lower the 
casing of a running string 72, which lowers the inner body 59 relative to 
outer sleeve 56. Subsequently, the operator will pick up the running 
string 72 to place the J-pin 61 in the second leg 63b. This causes sleeve 
56 to rotate an increment, as shown by the arrow in FIG. 3B, disengaging 
the threads on outer sleeve 56 from threads 57. Bands 58a on outer sleeve 
56 align with peaks 17b, allowing running tool 55 to be lowered into 
casing upper end portion 15c. 
Running tool 55 has a main supply passage 64 connected to the passage in 
the lower part of a packer string 69 which extends into inner body 59. A 
cement slurry passage 65 (FIG. 3A) connected to tubing string 27 is 
located in running tool 55 and can be connected to the lower end of main 
supply passage 64. Similarly, a fill-up passage 67 connected to tubing 
string 29 can be connected to the lower end of main supply passage 64. 
Inner body 59 of running tool 55 is connected to the packer string 69 by 
threads. The upper part of packer string 69 features a centralizer 70. Two 
or more forging packers 71 are mounted on the packer string 69 between 
centralizer 70 and inner body 59. Forging packers 71, when supplied with 
high internal pressure from a downhole pressure multiplicator (not shown), 
will inflate and radially expand to plastically forge the upper end of 
casing upper end portion 15c, as shown in FIG. 12. Hydraulic passages 73, 
extending through packer string 69, can be connected via pressure 
multiplicator to lower end of main supply passage 64 within running tool 
inner body 59. Packer string 69 is connected at centralizer 70 to a 
running string 72 which extends to the surface. Preferably, running string 
72 is another string of coiled tubing approximately two inches in 
diameter. Packers 71 have external axial grooves 74 which will align with 
valleys 17a of casing upper end portion 15c when packers 71 are lowered 
into upper end portion 15c with the centralizer 70 landed on top of the 
casing 15c as shown in FIG. 12. 
Referring to FIG. 22, in the preferred embodiment, electrically actuated 
valves 75, 77 and 79 are mounted in running tool inner body 59 (FIG. 1B). 
Valve 75 is in slurry passage 65 and opens and closes flow to tubing 27. 
Valve 77 is in opening fluid passage 67 for opening and closing flow from 
main supply passage 64 to tubing 29. Valve 79 is in pressure passage 73 
for opening and closing pressure fluid from main supply passage 64 to 
forging packers 71 (FIG. 1A). Electrical valve control wires (not shown) 
extend through coiled running string 72 to the surface to a control panel. 
A small accumulator (not shown) supplies hydraulic fluid to valves 73, 77, 
79 to open and close them when electrically actuated. Pumps 80 on the 
surface, which could be either cement or mud pumps, are used for 
delivering pressure fluid down main supply passage 64. 
Referring now to FIG. 15, casing 15 is fabricated by drawing a first metal 
strip 81 from a reel and bending two edges down around two laterally 
spaced apart, parallel continuous strings of the coil tubing 27, 29. As 
shown in FIG. 16, the edges are bent over and welded at seam 82. The upper 
side is bent into a concave shape touching seam 82, while the lower side 
is flat. Then, a second strip 83 is drawn from a reel and bent to have 
upturned edges. As shown in FIG. 17, second strip 83 is then bent by 
rollers around first strip 81 while first strip 81 is in the configuration 
shown in FIG. 16. Rollers then bend the upper side of strip 83 into a 
concave shape as shown in FIG. 20. Casing 15 thus is double-walled and has 
a flat side 85 that extends between parallel tubing strings 27, 29, 
generally tangent to outer diameter portions of tubing strings 27, 29. 
The use of two walls for casing 15 reduces the amount of strain that would 
otherwise occur during opening plastic deformation with a single wall 
casing having the same total thickness. Three or more wall casings might 
be desirable in certain cases. Casing made of multiple walls needs good 
friction between the walls to resist external pressure. Known friction 
enhancing techniques such as surface stamping, surface treatment or 
coating are desirable to offer adequate external pressure capability when 
open. Also the circumference of the external wall can be made slightly 
smaller than the previous one to offer adequate fretting of the wall when 
the casing is open. 
Casing 15 will be coiled on a reel 87 (FIG. 19) while in the configuration 
shown in FIG. 20. Reel 87 is a large member capable of holding 5000 feet 
or more of casing 15 which has a 51/2 inch external diameter when expanded 
to a cylindrical configuration. FIG. 18 illustrates corrugations 17 which 
are formed on both the upper and lower end portions 15c, 15a (FIGS. 1B, 
1D) by a roller corrugating operation. The upper and lower end portions 
15c, 15a remain generally cylindrical, although corrugated. The straight 
upper and lower end portions 15c, 15a are only a few feet in length and 
are not wound on reel 87 during transportation from the manufacturing 
plant to the well site. 
When deploying casing 15 from reel 87, casing intermediate portion 15b will 
first pass through a set of bending rollers 89 as shown schematically in 
FIG. 19. Folding rollers 89 will form casing 15 from the collapsed 
flattened configuration of FIG. 20 to the folded collapsed configuration 
shown in FIG. 21. This creates bight 18, and positions tubing strings 27, 
29 closer toward each other. The maximum width of casing intermediate 
portion 15b in the horseshoe collapsed configuration of FIG. 21, is less 
than the inner diameter of cased section 11 (FIG. 1A). The maximum width 
of casing intermediate portion 15b while in the collapsed flattened 
configuration of FIG. 20 is greater than the inner diameter of cased 
section 11. Associated with the folding rollers 89, a gripping and pushing 
mechanism 91 is employed. The folding mechanism 91 is constructed 
generally as in conventional coil tubing pushing mechanisms. It grips 
casing 15 without deformation, pulls it from reel 87, and pushes it 
downward into the well. The horseshoe shape of FIG. 21, resists the 
compression applied by gripping and pushing mechanism 91 while being 
pushed into the well. 
During installation, casing 15 will be uncoiled from reel 87 and pushed by 
mechanism 91 into the well until cement shoe 19 is close to the bottom of 
open hole section 13. The length of casing 15 will be previously selected 
so that the upper end of portion 15c extends into cased section 11 (FIG. 
1B), overlapping it over a substantial length. Valves 77, 79 are closed, 
valve 75 (FIG. 22) is opened, and cement pump 80 pumps a cement slurry 92 
(FIG. 9) down the passages 64, 65 through open valve 75 and down cement 
slurry tubing 27. As shown by the arrows in FIG. 1D, the cement slurry 
flows down passages 23, 20 and flows up the annulus space surrounding 
casing 15. 
A selected volume of cement will be pumped based on an estimate of the 
total volume of the annulus as if casing 15 had already been opened to the 
cylindrical configuration. Because of the collapsed rounded or horseshoe 
configuration of casing intermediate portion 15b, a much greater annulus 
volume initially will be present around casing intermediate portion 15b, 
as shown in FIG. 9, facilitating circulation. Consequently, initially, 
cement 92 will normally not completely fill the annulus to the top of 
casing upper portion 15c. During the pumping of cement, displaced drilling 
fluid, or returns, will flow up the corrugations 17 of the casing upper 
end section 15c into the annulus surrounding running tool 55 flow by ports 
60. The returns flow up around the forging packers 71 and around the 
annulus surrounding running string 72 to the surface. 
After pumping the calculated volume of cement slurry, a selected volume of 
flushing fluid will be pumped down cement slurry tubing 27. The volume is 
selected to be just the amount needed to push cement slurry from conduit 
72, tubing 27 and stinger 21 into the open borehole, but substantially no 
more. The valve 75 is then closed and valve 77 is open. Drilling fluid is 
pumped down conduit 72, which flows through passages 64, 67 and down 
fill-up tubing 29. The fluid flows out ports 25 into pressure chamber 35, 
shown in FIG. 1D. 
As shown in FIG. 8B, the fluid pushes upward on piston 33, which slides 
upward relative to tubing strings 27, 29. Piston head 37 pushes balls 43 
from the space in sleeve 48 upward into passages 45, as can be seen by 
comparing FIG. 1D with FIG. 8A. Once in contact with flange 50, the force 
exerted by piston head 37 begins to push the opening tool 31 upward while 
tubing strings 27, 29 remain stationary. Due to the engagement of balls 43 
with head 39 and casing lower end portion 15a, balls 43 are forced to roll 
down the inclined flutes 41, pushing the valleys 17a outward to first 
remove corrugations 17 of the casing lower end 15a and open the 
intermediate portion 15b. 
After a short distance, all of the balls 43 will be in engagement with 
conical head 39, as shown in FIG. 8A. Upper end 51 will move upward into 
the intermediate portion 15b. Balls 43 will open casing from the collapsed 
folded configuration of FIG. 9 to the cylindrical configuration of FIG. 
10. During the casing expansion process, the annulus surrounding casing 
intermediate portion 15b decreases, pushing cement slurry 92 upward, and 
returns will flow up into the channel spaces between corrugations 17 of 
casing upper end portion 15c and cased section 11. Some of the cement 
slurry 92 will flow out above running tool 55 to insure a proper seal 
between casings when they will be later forged together. As forming tool 
31 moves upward, the volume of pressure chamber 35 increases. This process 
will continue for the entire length of the casing which could exceed 
several thousand feet. 
Eventually, forming tool 31 will reach casing upper end portion 15c. At 
this point, balls 43 will push outward on valleys 17a to round the 
corrugated configuration 17 into a cylindrical configuration in the same 
manner as at casing lower end portion 15a. Forming tool 31 will eventually 
contact the lower end of running tool 55, which protrudes a short distance 
into casing upper end portion 15c, shown in FIG. 1B. 
The running tool 55 will be released from threads 57 by letting running 
string 72 go down a short distance, then pulling upward. While lowering, 
tubing strings 27, 29 will spiral slightly along their lengths to 
accommodate the compression. The downward movement of inner body 59 
relative to outer sleeve 56 causes J-pin 61 to move from first leg 63a to 
second leg 63b. When this occurs, an incremental amount of rotation of 
sleeve 56 occurs relative to inner body 59. This rotation, as illustrated 
in FIG. 3B, causes threads 57 to disengage from the threads on sleeve 56, 
releasing running tool 55 from casing upper end portion 15c. Grooves 58 on 
outer sleeve 56 will now be aligned with valleys 17a. 
The operator then again lowers running string 72 to place forging packers 
71 within casing upper end portion 15c as shown in FIG. 12. Because of the 
alignment of axial external grooves 58 and external grooves 74 (FIGS. 1A, 
1B) with corrugations 17, outer sleeve 56 and packers 71 will pass 
downward within casing upper end portion 15c. Centralizer 70 is closely 
spaced to the inner diameter of cased section 11, and will land on the 
upper edge of casing upper end portion 15c. Valve 77 is now closed and 
valve 79 open (FIG. 22). Pressurized fluid is supplied with mud pump 80 
through running string 72. This pressure, which will be multiplied by a 
known pressure multiplier, causes the forging packers 71 to inflate and 
plastically deform a portion of upper end portion 15c out into a tight 
gripping and sealing engagement with cased section 11. 
The fluid pressure is then bled off to allow forging packers 71 to retract. 
The running string 72 is lifted to pull up running tool 55. Tubing strings 
27, 29 will move upward along with stinger 21 and forming tool 31. The 
entire assembly is pulled out of the well and reeled back on the reel 87. 
FIG. 14 illustrates casing 15 without the installation apparatus. Casing 
hydrostatic pressure tests can then be done against the shoe and drilling 
can resume just after. Also, FIG. 14 shows that cased section 11 may be of 
a continuous expandable type installed as a liner to another cased section 
93. Cased section 93 is shown to again be an expandable type installed in 
the same manner as described and located within a conductor 95 that is 
threaded to a wellhead 97. 
The invention has significant advantages. As can be seen in FIG. 14, the 
difference in the inner diameters of one cased section to the next upward 
cased section is no greater than the wall thickness of the lower cased 
section. This reduces substantially the loss in diameter from one casing 
string to another, allowing substantially monodiameter drilling. It allows 
a smaller cased section at the top of the well for a given bottom diameter 
and depth than prior art wells. Monodiameter drilling allows smaller bits, 
less mud, less cuttings to be disposed of, and less cement to achieve the 
same final size well. This method allows one to have shorter and more 
different diameter strings than in the prior art. The method can be 
performed without the need for a hoisting mast if drilling is done by 
turbine driven drill bit on coiled tubing. 
While the invention has been shown in only one of its forms, it should be 
apparent to those skilled in the art that it is not so limited, but is 
susceptible to various changes without departing from the scope of the 
invention. For example, rather than coiled tubing running string 72, if a 
hoisting mast is available, conventional drill pipe may be used. In that 
event, rather than electrically actuated valves, the valving can be 
accomplished by balls or darts dropped down the conduit 64 to selectively 
close and open the passages. Also, rather than elastomeric packers for 
expanding the casing upper end portion, other pressure actuated metal 
radially expandable members may be employed. In addition, in lieu of balls 
on inclined flutes which circulate in a cycle, expander segments which 
slide downward from an upper retracted position to a lower expanded 
position, then stop, could be employed.