Rotatable liner hanger with multiple bearings and cones

A multiple cone, multiple bearing liner hanger for hanging a well liner for extension of the casing liner. The multiple slip cone and multiple bearing arrangement provides uniform, positive distribution of liner weight thereby facilitating hanging of heavier liner strings. The multiple bearings ensure proper rotation of the liner during cementation. The multiple cone, multiple bearing liner hanger includes an upper slip assembly with an associated bearing and a lower slip assembly with an associated bearing. The hanger is hydraulically set by first setting the upper slips and thereafter setting the lower slips. A series of shear pins ensure proper setting of the hanger to distribute the hang weight evenly over the slip cones and bearings.

BACKGROUND OF THE INVENTION 
I. Field of the Invention 
This invention relates to rotatable liner hangers for setting successive 
sections of casing liner within a well bore and, in particular, to a liner 
hanger which incorporates double slip cones and double bearings for 
improved weight distribution of the liner. 
II. Description of the Prior Art 
Liner hangers have been used for many years to attach an inner string of 
well pipe or casing liner to the lower end of a larger diameter well pipe 
or casing liner already set within a well bore. After hanging the liner, 
the liner will usually be cemented within the well bore by circulating a 
cement slurry through a setting string and the interior of the liner and 
upwardly about the exterior of the liner. Typical liner hangers include at 
least one set of slips with slip elements which wedge on a slip cone to 
grip the interior surface of the outer casing. The slip elements are 
arranged to be expanded into gripping engagement with the interior of the 
larger casing by the underlying slip cone. The slip cone travels beneath 
the slip elements as a result of mechanical or hydraulic actuation of the 
tool. In many applications, the casing liners are long and heavy requiring 
additional slip area to assure effective attachment of the liner. Such 
attachment can be carried out by large slip assemblies or a plurality of 
spaced apart slip assemblies. 
Because of the nature of the slurry used to cement the casing liners in 
place, it has been found that the rotation of the liner facilitates proper 
cementation. As a result, rotatable liner hangers were developed to ensure 
the flow of cement about the casing liner. Such rotatable liner hangers 
may utilize a rotatable bearing assembly in conjunction with the slip 
assembly. The bearing allows rotation of the liner independently of the 
set hanger during cementation. However, due to the increased length of 
some liners and a desire for additional fluid by-pass around the liner 
hanger multiple slip and cone arrangements have been used. It has been 
found that with some multiple cone rotatable liner hangers, a 
disproportionate load was being placed on the upper slip assembly and its 
associated bearing. This resulted in increased wear and failure of the 
rotatable liner hanger. 
Liner hangers have been developed which comprise individual hanger units 
which can be connected in series to form a multiple bearing or a multiple 
cone liner hanger. However, because individual units must be manufactured 
and stocked, such a system is prohibitively expensive. Moreover, since the 
units operate independent of each other the load may not be evenly 
distributed between the individual liner hanger units. The separate units 
are also, at times, difficult to set with varying densities of cement 
slurry and mud displacement since multiple shear pins must be accurately 
and sequentially sheared to set the slips. 
SUMMARY OF THE PRESENT INVENTION 
The present invention overcomes the disadvantages of the prior known liner 
hangers by providing a bearing for rotation of the hanger and liner with 
each of the slip cones facilitating automatic and even weight distribution 
across the slip assemblies. 
The rotatable liner hanger of the present invention includes a pair of 
longitudinally spaced slip assemblies mounted to the tubular mandrel of 
the hanger. The tubular mandrel allows fluids to be pumped therethrough 
including hydraulic fluid initially to set the liner hanger and thereafter 
cementing mud to secure the casing liner. Each slip assembly includes a 
slip cone and a plurality of contiguous or circumferentially spaced slip 
elements. The slip elements are forced outwardly into contact with the 
positioned casing liner as they travel over the slip cone. 
Circumferentially spaced slip elements facilitate the circulation of 
cement slurry past and around the liner hanger to secure the liner. 
Associated with each slip assembly is a bearing to facilitate rotation of 
the liner hanger during cementing. In a preferred embodiment the bearing 
is mounted to the mandrel just above the slip cone of the associated slip 
assembly. As a result, the weight of the liner is evenly distributed among 
the slip assemblies preventing a single slip assembly, usually the upper 
slip, from carrying a majority of the load. Additionally, the bearings 
allow rotation of the liner and hanger during cementing relative to the 
set and fixed slip assemblies. The multiple bearings increases the 
capacity which can be hung and rotated. 
The liner hanger of the present invention is hydraulically set by pumping 
fluid through the hanger to operate a piston and cylinder connected to the 
slip assemblies. Shear pins are positioned such that the upper slip 
assembly is set against the casing first followed by setting of the lower 
slip assembly. This sequence ensures an even load on the slip assemblies 
and the associated bearings. Once the hanger is set, the liner and hanger 
may be cemented into position during which the liner can be rotated. 
Other objects, features, and advantages of the invention will be apparent 
from the following detailed description taken in connection with the 
accompanying drawings.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE PRESENT INVENTION 
Shown in FIGS. 1 through 3 is the rotatable liner hanger and liner assembly 
10 embodying a preferred configuration of the present invention. The 
assembly 10 is utilized to run and set a new section of casing liner 12 
within a well bore which may be a previously set casing section 14. 
Additional sections of liner 12 may be run into the well bore to extend 
the cased well bore with each liner extension 12 being connected to the 
lower end of the previously set casing section 14. Once a section of 
casing has been set it is normally cemented into position by pumping 
cement through the central passageway 16 to the bottom of the well bore 
and upwardly around the outside thereof to fill the outer annulus 18 
securing the casing within the well bore. However, prior to cementation, 
the new casing section 12 must be set or "hung" from the previously 
secured liner section 14 using the liner hanger 20 of the present 
invention. The liner hanger and liner assembly 10 are run into the well 
bore using a releasably connected running string 22 to position the hanger 
20 and liner 12 at the lower end of the outer casing liner 14. The running 
string 22 is preferably threadably connected to an end sub 24 attached to 
the upper end of the liner 12. Accordingly, the new section of casing 
liner 12 can be positioned and set within the well bore as will be 
subsequently described. 
The liner hanger 20 of the present invention is mounted to the outer 
annular surface of the liner 12 and generally includes an upper slip 
assembly 26, a lower slip assembly 28 and a mechanism for setting the 
slips 30. In order to facilitate rotation of the liner 12 relative to the 
hanger 20 and the outer casing 14, each of the slip assemblies 26 and 28 
is associated with a bearing assembly specifically an upper bearing member 
32 associated with the upper slip assembly 26 and a lower bearing member 
34 associated with the lower slip assembly 28. By supplying a bearing with 
each slip assembly, the of the liner 12 will be evenly distributed to both 
slip assemblies to ensure secure setting of the hanger 20 and smooth 
trouble-free rotation of the liner 12. 
The upper slip assembly 26 includes an annular slip cone 36 mounted to the 
liner 12 and a plurality of slip elements 38 which are movable relative to 
the slip cone 36 to set the upper slip assembly 26. As the slip elements 
38 move along the sloped surface 40 of the slip cone 36 the elements 38 
will expand outwardly into engagement with the casing 14 as shown in FIG. 
2. As the slip elements 38 expand outwardly they will separate to form 
gaps substantially aligned with notches 42 formed in the slip cone 36 
creating a series of fluid passageways to bypass the upper slip assembly 
26. These fluid passageways facilitate circulation of the cement around 
the upper slip assembly 26 to ensure proper setting of the liner 12. In a 
preferred embodiment, the annular bearing 32 is positioned between the end 
sub 24 of the liner 12 and the slip cone 36 of the upper slip assembly 26. 
As a result, the end sub 24 and liner 12 is free to rotate relative to the 
upper slip assembly 32 as will be subsequently described. 
The slip elements 38 are attached to slip holders 44 which in turn are 
slidably connected to a spacer sleeve 46. The slip holders 44 are received 
within corresponding slots 48 formed in the spacer sleeve 46 and 
detachably secured thereto by shear screws 50. The screws 50 are designed 
to shear under a predetermined force once the upper slip assembly 26 has 
been set as will be described herein. The slip holders 44 and the spacer 
sleeve 46 are mounted to the exterior surface of the liner 12 such that 
the liner 12 will be free to rotate relative thereto since the holders 44 
and sleeve 46 will be held stationary by the set slip elements 38. The 
sleeve 46 includes an abutment end 52 which cooperates with the lower slip 
assembly 28 and bearing 34. 
The lower slip assembly 28 similarly includes a slip cone 54 and a 
plurality of selectively expandable slip elements 56. The slip elements 56 
are detachably connected to the slip cone 54 by shear screws 58 which 
prevent the slip elements 56 from travelling up the slope surface 60 of 
the slip cone 54 and setting against the casing 14 until sufficient force 
is applied to shear the screws 58. The shear screws 58 allow the upper 
slip assembly 26 to be set prior to setting of the lower slip assembly 28 
ensuring uniform weight distribution. As the slip elements 56 expand 
outwardly into engagement with the casing 14 (FIG. 3), the elements 56 
will separate forming gaps substantially aligned with notches 62 formed in 
the slip cone 54 creating a series of fluid bypass passageways. A 
cross-sectional perspective view of the set slip assembly with the slip 
elements 56 separated in spaced apart relation forming the bypass 
passageways 57 is shown in FIG. 4. These passageways facilitate 
circulation of the cement past and around the lower slip assembly 28. To 
allow independent rotation of the lower and upper slip assemblies, the 
lower bearing 34 is disposed between the upper end of the slip cone 54 and 
the end 52 of the sleeve forming a part of the upper slip assembly 26. 
Accordingly, once the upper slip assembly 26 has become set within the 
casing 14 the lower slip assembly 28 will not be fixed against rotation. 
Furthermore, upon setting both slips, the weight of the liner 12 will be 
distributed over both bearings 32 and 34 allowing greater sections of 
casing to be hung and rotated. The slip elements 56 are connected to slip 
holders 64 which are connected to a lower spacer sleeve 66. The sleeve 66 
and holders 64 are slidably mounted to the outer surface of the liner 12. 
In order to set the slips through longitudinal movement relative to the 
liner 12, the sleeve 66 is connected to the setting mechanism 30. In a 
preferred embodiment, the mechanism 30 is responsive to fluid pressure 
within the liner 12 which is communicated thereto through at least one 
port 68 formed in the liner 12. The setting mechanism 30 includes an outer 
sleeve 70 or cylinder which forms an annulus 72 with the liner 12. 
Received within the annulus 72 is an inner sleeve 74 or piston. The lower 
end of the annulus 72 communicates with the port 68 such that an increase 
in fluid pressure within the liner 12 will cause the piston 74 to 
longitudinally slide within the cylinder 72. The outer sleeve 70 is 
connected to the liner 12 against relative movement by set screw 76. The 
piston or inner sleeve 74 is connected to the spacer sleeve 66 of the 
lower slip assembly 28 by set screws 78 wherein as piston 74 is forced to 
move longitudinally as a result of fluid pressure within the cylinder 72 
the slip assemblies will also be moved to set the hanger 20. 
Referring now to FIGS. 1 through 3, which show the liner hanger 20 at 
various stages of being set, the liner and liner hanger assembly 10 is run 
into the well bore using string 22. Once the hanger 20 is positioned near 
the lower end of the outer casing 14, fluid pressure within the central 
passageway 16 is increased to actuate the setting mechanism 30. The 
increased fluid pressure causes the piston sleeve 74 to move upwardly 
relative to the liner 12 and cylinder sleeve 70. The longitudinal movement 
of the sleeve 74 in turn will cause the lower slip assembly 28, the lower 
bearing 34, the spacer sleeve 46 and the slips 38 of the upper slip 
assembly 26 to also move longitudinally relative to the liner 12. Since 
the slips 56 of the lower slip assembly 28 are connected to the slip cone 
54, the longitudinal movement will be imparted to the cone 54 preventing 
the lower slip assembly 28 from setting. As the slip elements 38 of the 
upper slip assembly 26 travel along the sloped surface 40 of the cone 36, 
which remains stationary, the slip elements 38 will expand outwardly into 
engagement with the casing 14 as shown in FIG. 2. Once the upper slip 
assembly 26 is set continued upward pressure will cause screws 50 to shear 
moving spacer sleeve 46 relative to the slip holders 44 until the sleeve 
46 engages retaining ring 45. Further pressure will cause screws 58 to 
shear releasing the slip elements 56 from the slip cone 54 allowing them 
to move along sloped surface 60 into expansion against the casing 14 as 
shown in FIG. 3. With both slip assemblies set, the weight of the liner 12 
can be released thereby preventing the slips from disengaging. Moreover, 
as the slip assemblies are set and particularly once the weight of the 
liner 12 is released, the weight of the liner 12 will be distributed over 
both bearings 32 and 34 thereby increasing the bearing capacity of the 
hanger 20. Similarly, the hang weight of the liner 12 will be evenly 
distributed over both slip assemblies. Thus, the liner hanger 20 of the 
present invention will allow larger sections of liner 12 to be hung and 
set. 
The liner hanger assembly 10 of the present invention is run into the cased 
14 and open bore hole using the running equipment shown generally in FIG. 
5. The liner hanger 20 is run on drill pipe and attached by a running seat 
100 which attaches the hanger 20 to a setting tool 102. A portion of the 
liner 12 extends above the running seat 100 and includes a debris barrier 
104 which prevents debris from falling into the tie-back receptacle 106. 
The drill pipe 22 extends to the surface where a dropping head manifold 
108 is installed. When the liner 12 is run to the desired depth, drilling 
mud is circulated down the drill pipe 22 and back up the annulus 
surrounding the running equipment to clean up the well. To set the 
hydraulic liner hanger 20 a ball is dropped from the dropping head 108 and 
pumped to a seat 110 just below the liner hanger 20. Fluid pressure is 
applied which activates the setting mechanism 30 in the hanger 20 to set 
the slips 26 and 28. Liner weight is slacked off so that the slip elements 
will bite into the casing 14 to suspend the liner 12. When additional 
fluid pressure is applied, the ball seat 110 shears out to re-establish 
circulation. Once the hanger assembly 10 is set and the setting tool is 
released by clockwise rotation, the new liner 12 can be cemented within 
the hole. During cementation, the liner 12 may be rotated using a rotary 
table 112 to obtain an improved cement job. 
Once the hanger 20 is set, the liner and liner hanger assembly 10 may be 
cemented into place. The cement is typically pumped through the central 
passageway 16 to the bottom end of the liner 12 at which point the cement 
will flow upwardly around the outside of the liner 12. The gaps between 
the slip elements allow the cement to completely fill the outside of liner 
hanger 20 and the liner 12 for securement thereof. To facilitate thorough 
cementation of the liner and hanger, the liner 12 is rotated using the 
string 22 during cementation. The liner 12 can be rotated relative to the 
hanger 20 because of the double bearings 32 and 34. 
When sufficient cement slurry has been pumped through the passageway 16, a 
drill pipe plug 114 is released from the dropping head 108 and pumped 
downhole until it reaches the liner wiper plug 116. Increased pressure 
will shear the liner wiper plug 116 causing it to seat within the landing 
collar 110. The drill pipe plug 114 and the liner wiper plug 116 act as a 
back pressure valve to prevent the cement slurry from flowing back inside 
the liner 12. Upon completion of the cementing process, the drill pipe 22 
and the setting assembly are pulled from the hole. 
The foregoing detailed description has been given for clearness of 
understanding only and no unnecessary limitations should be understood 
therefrom as some modifications will be obvious to those skilled in the 
art without departing from the scope and spirit of the appended claims.