Hanger suspension system

A hanger suspension system includes an inner casing hanger having an outer circumferential surface with at least three sets of at least three longitudinally spaced outwardly projecting load bearing members azimuthally spaced about the outer circumferential surface and separated by linear flow passages. A hanger assembly is positioned on each set of bearing members and is axially slidable on the outer circumferential surface of the hanger. Each hanger assembly includes a plurality of longitudinally spaced arcuate members having inwardly extending load bearing shoulders for engaging the load bearing members of the inner hanger. The hanger suspension system also includes an outer head having a non-restrictive bore with annular recesses which include load bearing surfaces and camming surfaces. The arcuate members of the hanger assembly include outwardly extending load bearing shoulders for engaging the load bearing surfaces of the outer head and outwardly extending camming shoulders for engaging the camming surfaces in the annular recesses of the outer head. The hanger assembly also includes a trigger member for releasing the bearing member upon alignment with the outer head and includes a deformable alignment tang for locating the recesses in the outer head. The load bearing members on the inner hanger bear against the arcuate members so as to maintain the arcuate members in engagement with the load bearing surfaces of the outer head. The suspension of the inner hanger within the outer hanger is repeatable so as to allow the reciprocation of the inner casing string within the outer casing string during the cementing operation.

FIELD OF THE INVENTION 
This invention relates generally to suspension systems for suspending 
concentric strings of pipe within an oil and gas well and, more 
particularly, relates to a casing hanger for supporting an inner casing 
string within an outer casing string at an offshore well and still more 
particularly, but not exclusively, to casing hanger systems for supporting 
casing strings at the mudline of the ocean floor. 
BACKGROUND OF THE INVENTION 
With the advent of offshore drilling in order to produce petroleum products 
from production zones located beneath bodies of water, it has become 
desirable to provide casing hanger systems that are adapted to be 
positioned at or near the bottom of the body of water. These hanger 
systems are typically known as mudline suspension systems. Mudline 
suspension systems use an outermost casing hanger which suspends a coaxial 
series of concentric casing strings such that their combined weight is 
suspended at the mudline. This allows the drilling rig to operate in 
deeper than normal waters, and provides for disconnection and removal of 
equipment above the mudline when the drilling rig moves from one drilling 
location to another drilling location or when the driller moves away from 
the well and subsequently re-establishes a well drilling connection when 
it is desirable to continue drilling operations. By locating suspension 
systems at or near the ocean floor, a temporarily abandoned well or capped 
well does not present an obstruction that typically interferes with the 
marine environment. Such suspension systems also enable the driller to 
complete wells by means of an ocean floor completion or extend the casing 
to the surface for completion on a drilling ship or platform and 
subsequently lends a degree of flexibility in completion systems that 
renders such casing hanger systems desirable. 
In mudline suspension systems, concentric casing strings are hung and 
cemented in place as the drilling progresses to increasing depths. Typical 
diameters for various casing strings are 30", 20", 16", 133/8", 95/8" and 
7". When drilling a subsea well from a fixed platform, it is desirable to 
support the casing weights from the mudline with a blowout preventer 
located at the platform. Risers extend from the blowout preventer to the 
support location and are of substantially the same size as the casing 
string itself. The riser may be several hundred feet long and is made up 
of successive riser pipes whose adjacent ends are connected at the water's 
surface as the riser is lowered into position, or disconnected as the 
riser is raised. Each of a plurality of inner casing strings is lowered 
into a bore drilled in the ocean floor by means of a hanger connected to 
the riser. When the hanger is landed within the hanger from which the next 
outer casing string is suspended, cement is pumped and circulated down 
through the flowbore of the riser, hanger and suspended string, around the 
terminal end of the string, and up into the annulus around the suspended 
string, to anchor it in place. It is necessary that the cement pass 
between the adjacent hangers of the inner and outer casing strings. When 
the well has been tested, the riser may be retrieved, and the hangers at 
the upper ends of the casing strings capped or closed off at the ocean 
floor to permit the drilling rig to be moved to another location. When it 
is desired to complete the well for production purposes, the cap is 
removed and risers are lowered into connection with at least the innermost 
suspended casing strings to tie them back to a production platform at the 
surface of the water. The successive hangers are supported on one another 
so that the load of all of the hangers and the casing supported from the 
hangers is supported by a seat in the bore of the outermost casing hanger. 
The casing hangers are connected to the upper ends of successively smaller 
diameter casing strings which are adapted to be lowered into and landed 
within the bore of a casing hanger which is connected to an outermost 
casing string at the mudline in order to suspend the strings within the 
outermost casing of the wellbore. The annular space, commonly called an 
annulus, between an outer casing string and the next inner casing string 
permits cement returns to circulate therethrough as the string is cemented 
within the wellbore, or adapted to be closed off, when the casing has been 
cemented. Casing strings of a large diameter, as for example, 16", 20" or 
30", have sufficient annular space to allow the use of solid hangers, 
normally in the form of an annular landing shoulder on the outer casing 
hanger, which in turn, suspends an inner casing hanger having an annular 
support shoulder. Such shoulders typically have a bypass or flute 
therethrough to connect the annulus above and below the hangers for the 
circulation of cement returns. 
Casing strings of a smaller diameter severely limit the annular space by 
which to support the next inner-casing hanger and also allow adequate flow 
passages therebetween for the circulation of cement returns. Because the 
annular spaces between the inner-most casing strings are much smaller, 
typically the hangers are provided with support members which are 
withdrawn or retracted until the string is lowered into the wellbore to 
dispose the support members opposite the landing member on the next outer 
hanger. Thus, in smaller strings, there is more limited annular space 
available for support and the support must be arranged in such a way as to 
permit flow through the annular space to facilitate cementing operations. 
One prior art type of hanger includes a support member having a 
circumferentially split ring which is contractible within a recess in the 
outer surface of the inner hanger body as the string is being lowered, and 
which has a landing surface on its lower end which, when the string has 
been so lowered, expands outwardly into a supported position on a landing 
member in the form of an upwardly facing seat extending radially inward 
from the bore of the outer hanger of the next outer casing string. 
However, in order to support the weight of the casing string, the 
expandable rings must have relatively large support surfaces, which of 
course require landing surfaces on the next outer hangers of equally large 
radial extent. As a consequence, in order for the hanger bodies to be 
thick enough to withstand pressure differences between the casing strings, 
it has heretofore been thought necessary, in apparatus of this type, to 
vertically stagger the expandable support ring and landing surface on at 
least some of the hangers. This in turn has increased the height of each 
such hanger and thus the size and cost of the suspension system. 
In another system of the prior art, the inner casing hanger with its string 
of casing includes a diametrically compressible collet which is urged 
outwardly. The collet includes specially-shaped support shoulders 
extending outwardly which engage grooves in the previously-set outer 
hanger. The inner casing hanger then rests on this collet. Means such as 
shear pins are required to carry the collet on the inner casing hanger at 
least until it enters the casing below the blowout preventer and sometimes 
to pull the collet down until it reaches the support elevation. Other 
systems use the load support shoulder to push the collet down after means 
are provided to constrain the collet until it enters the outer casing 
string. 
In another embodiment of the prior art, the inner and outer casing strings 
are connected together by means of a resilient expandable and contractible 
locking support element mounted on the inner casing hanger which is biased 
radially outwardly but free to expand and contract radially until it 
engages a mating profile in the outer casing string. After engagement, a 
releasable means permits the locking support element to move axially with 
respect to the inner casing hanger to a locked expanded position and 
support the weight of the inner casing string on the outer casing string. 
By providing two or more coacting load bearing shoulders between the inner 
casing string and the locking support element and two or more coacting 
load bearing shoulders between the outer casing string and the locking 
support element, a greater area of load bearing surfaces is provided in a 
limited annular space. Longitudinal slots are provided in the locking 
support element for the by-pass of fluid flow. 
The above prior art designs present a considerable restriction to flow 
during cementing. The arrangement of these prior art suspension systems, 
such as a contractible split ring, compressible collet, or other 
contractible locking support element, forces the fluid to flow through a 
tortuous path through expensive milled slots. Further, as wells approach 
greater depths, the innermost hangers must carry increased load thus 
requiring larger support surfaces thereby further reducing available 
space. 
Typically, in the above prior art designs, the load carrying member also 
serves as the triggering mechanism. This results in these members having 
to resist considerable bending stresses, a condition which precludes 
manufacturing the suspension system by casting. Castings invariably have 
some porosity which makes their resistance to bending less reliable than 
if the parts in the suspension system are forged or machined from bar 
stock. 
These prior art suspension members also occupy a larger portion of the 
latch profile such that debris and drilling mud filter cake can accumulate 
in the latch profile and greatly impair the latching process. The support 
members which enter the profiles of the previously run outer casing hanger 
must be fully engageable despite any mud that may have previously 
accumulated in the profiles. The restriction of the annular space between 
the innermost casing hangers further encourages the accumulation of debris 
and drilling mud in the profiles. 
The limited annular space between casing strings of a relatively smaller 
diameter is of particular concern when deep wells are drilled which 
deviate from vertical. A casing hanger for suspending an inner casing 
string of a relatively small diameter may suspend 10,000 to 15,000 feet of 
casing weighing approximately one million pounds. Previously, in vertical 
wells, the smaller casing strings were often rotated to assist the cement 
in completely filling the annulus. However, in strings of 10,000 to 15,000 
feet, the inner casing string cannot be rotated to assist in causing the 
cement to fill the annulus in a deviated well. Although not recommended, 
many operators reciprocate the inner casing string to assist in completely 
filling the annulus with cement. To allow reciprocation, it is necessary 
to have a casing hanger which does not require rotation to suspend the 
inner casing hanger within the outer casing hanger. In particular, the 
inner casing hanger must not be latched down or locked down such that the 
casing string may be reciprocated. Further, the act of suspending the 
inner casing hanger within the outer casing hanger must be repeatable to 
allow for the initial suspension, the subsequent reciprocation, and then a 
final suspension after the cementing operation has been completed. 
The present invention overcomes the deficiencies of the prior art. 
SUMMARY OF THE INVENTION 
The hanger suspension system of the present invention includes an inner 
casing hanger on an inner casing string suspended to and from an outer 
casing head on an outer casing string. The inner hanger includes an outer 
circumferential surface having at least three sets of at least three 
longitudinally spaced outwardly projecting load bearing members 
azimuthally spaced about the outer circumferential surface and separated 
by linear flow passages. A hanger assembly is positioned on each set of 
bearing members and is axially slidable on the outer circumferential 
surface of the hanger. Each hanger assembly includes a plurality of 
longitudinally spaced arcuate members having inwardly extending load 
bearing shoulders and outwardly extending load bearing shoulders. The 
arcuate members further include outwardly extending camming shoulders. 
The outer head has a non-restrictive bore with annular recesses which 
include load bearing surfaces and camming surfaces. Each hanger assembly 
further includes a trigger member mounted on the arcuate members for 
locating the annular recesses on the outer head and releasing the arcuate 
members on the hanger assembly whereby the outwardly extending load 
bearing shoulders engage the load bearing surfaces in the recesses. The 
trigger member includes a deformable alignment tang for being deformably 
received within a locator recess adjacent said recesses in the outer head. 
Springs are provided between the arcuate members and trigger member to 
bias the trigger member outwardly and into the recesses of the outer head. 
The load bearing members on the inner hanger bear against the arcuate 
members so as to maintain the arcuate members into engagement with the 
load bearing surfaces of the outer head. 
The present invention is particularly useful during the cementing of the 
inner casing string within the outer casing string. Once the inner hanger 
is suspended within the outer head by engaging the inwardly and outwardly 
extending load bearing shoulders on the arcuate members with the load 
bearing members of the hanger and load bearing surfaces of the head, 
respectively, cement is pumped down the flow bore of the inner casing 
string and up the annulus formed by the inner and outer strings. To assist 
the flow of the cement around the inner casing string, the hanger and 
inner casing string is lifted from the load bearing surfaces on the outer 
head by cammingly engaging the outwardly extending camming shoulders of 
the arcuate members with the camming surfaces on the outer head. This 
causes the arcuate members to contract and allow the inner casing string 
to be raised and lowered with respect to the outer casing string to cause 
the cement to flow around the outer circumference of the inner casing 
string and completely fall any voids in the annulus around the inner 
casing string. Prior to the cement setting up, the inner hanger is again 
suspended on the outer hanger by lowering the hanger and inner casing 
string to allow the outwardly extending load bearing shoulders on the 
arcuate members to reengage the load bearing surfaces in the recesses of 
the outer head. The cement is then allowed to set. 
Still other and further objects, features and advantages will be apparent 
from the following description of presently preferred embodiments of the 
invention, given for the purpose of disclosure and taken in conjunction 
with the accompanying drawings.

DESCRIPTION OF PREFERRED EMBODIMENTS 
The suspension system of the present invention may be used in a variety of 
different types of wells being drilled for the production of oil and gas. 
The suspension system is particularly adapted for use in drilling offshore 
oil and gas wells. The preferred use of the suspension system of the 
present invention is for suspending concentric strings of casing within an 
offshore oil and gas well at the mudline of the ocean floor. Although the 
present invention will be described for the installation of a mudline 
suspension system for an offshore oil and gas well, it should be 
appreciated that the suspension system of the present invention is not 
limited to use in such an installation. 
Referring initially to FIG. 1, there is shown an offshore oil and gas well 
being drilled into the ocean floor 10 from a ship or platform 12 located 
at the water's surface 14. FIG. 1 is a diagrammatic illustration of a 
typical installation of a mudline suspension system for suspending a 
plurality of concentric casing strings at the ocean floor 10. As is well 
known in the art, a plurality of casing strings are suspended within 
successively smaller diameter bores drilled into the ocean floor 10. 
Referring now to FIGS. 1 and 2, initially, a conductor casing string 16, 
typically 30 inches in diameter, with a casing hanger 11 are lowered on a 
conductor riser 20 from the drilling platform 12 and are driven or jetted 
into the ocean floor 10 until casing hanger 18 rests near the ocean floor 
10. Casing hanger 18 is provided with a landing shoulder for interiorly 
supporting a surface casing string 22. As is well known in the art, 
pressure control equipment 24 is mounted on the platform 12 and includes a 
wellhead 26 to which the upper end of riser 20 is connected. A blowout 
preventer stack 28 is installed above the wellhead 26. As is also well 
known in the art, the suspended casing strings are anchored within the 
well bores by means of columns of cement 29 which, as will be explained 
hereinafter, may extend upwardly into the annular space formed between the 
concentric casing strings. 
After the conductor casing string 16 is installed, a borehole is drilled 
for the surface casing string 22, typically having a diameter of 16 or 20 
inches. Surface casing string 22 is lowered into place with a surface 
casing hanger 30 on a surface casing riser 32. The surface casing hanger 
30 includes an annular support shoulder which is supported by the landing 
shoulder on conductor casing hanger 18. The surface casing 22 is then 
cemented in place. Casing hanger 30 also includes an inner landing 
shoulder for supporting intermediate casing string 34. 
A borehole is then drilled for the intermediate casing string 34, typically 
having a 133/8 inch diameter. Intermediate casing string 34 and 
intermediate casing hanger 36 are lowered on intermediate riser 38 with an 
annular stop shoulder on intermediate casing hanger 36 engaging the 
landing shoulder on outer surface casing hanger 30. The intermediate 
casing string is then cemented in place. The intermediate casing hanger 36 
includes a profile 40 which receives a hanger assembly 50 mounted on a 
production casing hanger 60 for supporting a production casing string 42. 
The borehole for production casing string 42 is then drilled and the 
production string 42, typically 95/8" in diameter, and production casing 
hanger 60 are lowered on production casing riser 44 until the hanger 
assembly 60 engages profile 40, as hereinafter described in further 
detail. Although not shown, another borehole may be drilled for an 
innermost casing string, typically 7 inches in diameter, for suspending 
another casing string within the production casing string 42 such as on 
profile 61. 
It should be appreciated that each of the hangers 18, 30, 36, and 60 not 
only serves as a hanger for suspending casing strings 16, 22, 34 and 42, 
respectively, but also serves as a casing head for supporting inner casing 
hangers and casing strings. Where casing hangers 18, 30, 36, and 60 are 
serving as a casing head, they may be referred to as a casing head rather 
than a casing hanger. 
During the drilling of each borehole, the mud returns flow upwardly in the 
annulus formed between the drill string and the next outer casing string 
and riser. After each successively smaller diameter wellbore is drilled, 
the casing string, which is to line that wellbore, is cemented into place. 
The annulus serves as a means for returning drilling mud to the pressure 
control apparatus on the drilling rig at the platform 12 and for flowing 
cement into the well. Each of the hangers 18, 30, and 36 have flow 
passages (not shown) for communicating the annulus above and below the 
hanger to the flow of drilling mud and cement returns such that when the 
hanger is landed at the mudline, the drilling mud and cement returns may 
pass upwardly therethrough. These and other practices are well known in 
the art, and therefore form no part of the present invention and 
consequently require no further detailed description. 
The larger casing strings, such as conductor casing 16 and surface casing 
22, have sufficient annular space therebetween to permit flow passages 
through the landing and support shoulders for allowing an adequate 
circulation of drilling mud and cement returns through the annulus. The 
mudline casing hanger system of the present invention is particularly 
directed to suspension systems for casing strings of a relatively smaller 
diameter such as for supporting a production casing string within an 
intermediate casing string. The diameters forming the annular space 
between these casing strings severely restrict the space allowed to form 
bypasses or flutes through the hangers to allow for the adequate 
circulation of drilling mud and cement returns. The mudline casing hanger 
system of the present invention is particularly directed to casing hangers 
of this diameter or smaller and thus the invention, for purposes of 
illustration, will be described in suspending a production casing string 
within an intermediate casing string. However, it should be understood 
that the mudline casing hanger system of the present invention may also be 
used in the suspension of other sized casing strings and in particular, 
smaller diameter strings as for example an innermost casing string such as 
a seven inch casing string. 
Referring now to FIG. 3, there is shown an enlarged view of the profile 40 
of outer intermediate casing head 36. Outer casing head 36 includes a 
tubular body 62 having an inner cylindrical wall 64 forming a 
non-restrictive flow bore 66. The inner cylindrical wall 64 forms the 
inner diameter of casing head 36. Profile 40 is formed by a plurality of 
recessed circumferential grooves in cylindrical wall 64 including a lower 
annular groove 70, a medial groove 72, and a upper groove 74. Each of the 
grooves 70, 72, 74 form an upwardly facing, downwardly tapering 
frusto-conical bearing surface 76 and a downwardly facing, upwardly 
tapering frusto-conical camming surface 78. Lower bearing surface 76 
tapers approximately 20.degree. from horizontal and upper camming surface 
78 tapers approximately 45.degree. from horizontal, horizontal being 
perpendicular to the longitudinal flow axis 65 of outer casing head 36. 
Medial and upper annular grooves 72, 74 form an annular segment 80 
therebetween and medial and lower annular grooves 72, 70 form a lower 
annular segment 82 therebetween. Upper annular segment 80 includes an 
annular locator recess 84 forming an upwardly facing and upwardly tapering 
arcuate locator surface 86 and a downwardly facing and upwardly tapering 
arcuate camming surface 88. Locator surface 86 has a taper of 15.degree. 
with horizontal and upper camming surface 88 has taper of approximately 
30.degree. from the longitudinal direction, i.e. the flow axis 65. 
Referring now to FIGS. 4A, B, and C, there is shown the hanger body 90 of 
inner production casing hanger 60. Hanger body 90 is a generally 
cylindrical member forming a flow bore 92 therethrough and an outer 
cylindrical surface 94 forming the outer diameter of body 90. Three sets 
96, 97, and 98 of three load bearing members or lugs 100, 102, 104 are 
milled into the hanger body 90 thereby forming outer surface 94. Each of 
the three sets of lugs 96, 97, 98 are separated by longitudinal, linear 
flow passages or channels 106, 107, 108. Linear flow passages 106, 107, 
108 are generally straight and parallel to the flow axis 65 and have 
radial boundaries formed by the inner diameter of hanger 60 and the outer 
diameter of head 36. This provides a maximum radial width to flow passages 
106, 107, 108 for the circulation of drilling fluids and cement returns. 
Since each of the three sets 96, 97, 98 of lugs 100, 102, 104 are the 
same, a description of one lug set will be illustrative of the description 
of the other lug sets. 
Each of the lugs 100, 102, 104 include an outer arcuate, longitudinal 
bearing surface 110 and an inner arcuate longitudinal bearing surface 112 
extending below outer arcuate bearing surface 110. An arcuate, downwardly 
facing upwardly tapering load bearing member 114 is formed by the 
transition between the diameters of outer surface 110 and inner surface 
112. A longitudinal channel 116 extends through the mid section of lower 
lug 100 and intermediate lug 102. Channel 116 extends into upper lug 104 
forming an expanded flat 118 in inner surface 112 and an expanded flat 119 
in outer surface 110. The channel 116 at expanded flat 119 has a smaller 
depth, i.e. radius, than channel 116 at expanded flat 118, thus forming a 
step 121 between flats 118, 119. Annular horizontal recesses 120, 122, 124 
are formed below each of the lugs 100, 102, 104, respectively, for 
receiving a hanger assembly 125 including a cage 130, trigger 170 and 
trigger guard 200 hereinafter described (See FIG. 9). Lower lug 100 and 
intermediate lug 102 include upwardly facing, upwardly tapering 
frusto-conical surfaces 101, 103, respectively, for supporting hanger 
assembly 125. Each of the lugs 100, 102, 104 have downwardly facing, 
upwardly tapered lower terminal surfaces 105 for engaging hanger assembly 
125 as hereinafter described. 
The inner casing hanger 60 is provided with upper and lower sets 123,126, 
respectively, of centralization lugs 127 having a tapered surface 128. 
Channels 106, 107, 108 separate each of the lugs 127. Centralization lugs 
127 centralize inner casing hanger 60 within outer casing hanger 36 and 
also provide protection for the three sets of hanger assemblies 125 as 
inner casing hanger 60 is lowered or raised within the bore 66 of outer 
casing hanger 36. The tapered surfaces 128 of centralization lugs 127 
assist in the centralization of inner casing hanger 60 within outer casing 
hanger 36. 
Referring now to FIGS. 5A, B, and C, there is shown a cage 130 formed by a 
set of three arcuate support members or dogs 132, 134, and 136 attached by 
a transverse longitudinal member 138. A cage 130 is mounted, as 
hereinafter described in further detail, on each of the three lug sets 96, 
97 and 98 on hanger body 90. The three dogs 132, 134, 136 and transverse 
member 138 are investment cast. A longitudinal channel 140 is provided 
through the center of dogs 132, 134 and 136 and three blind bores 144 are 
provided in the outer surface of longitudinal member 138 in alignment with 
the center line of each of the dogs 132, 134, 136 for housing one end of a 
biasing member or spring 150, hereinafter described with respect to FIG. 
7. Further, a threaded bore 146 is provided through longitudinal member 
138 above lower dog 132 for assembly purposes, as hereinafter described. 
Since each of the dogs 132,134, 136 is substantially the same, a 
description of lower dog 132 will also describe the other two dogs 134, 
136. Lower dog 132 is an arcuate segment having an inner arcuate bearing 
surface 148 and an outer arcuate bearing surface 152. The radius of inner 
arcuate surface 148 conforms to the radius of the wall 94 of hanger body 
90. The thickness of arcuate dog 132 is less than the difference in radius 
between the inside diameter and outer diameter of outer casing head 36 and 
the inner casing hanger 60 respectively. The outer bottom arcuate comer of 
dog 132 is chamfered at 154 while the downwardly facing bottom surfaces 
156, 157 of dogs 134, 136 respectively are tapered upwardly and outwardly 
for supporting engagement with upwardly facing surfaces 101,103 of lugs 
100, 102 respectively. Each dog 132 includes an arcuate notch 160 on the 
upper inner surface 148 forming an upwardly facing bearing surface 161. An 
expanded notch 158 is coaxial with channel 140 to form a pair of inwardly 
directed flanges 159 for engagement with ears 182, 183 on trigger 170, as 
hereinafter described. 
Referring now to FIGS. 6A and B, there is shown a trigger 170 to be mounted 
on each of the three cages 130, as hereinafter described in further 
detail. Trigger 170 has an elongated body 172 sized to be received within 
the vertical channel 140 of each cage 130. The lower terminal end 174 
includes horizontal projecting ears 176, 177 projecting from each side 
thereof. Likewise, the upper terminal end 178 of elongated body 172 also 
includes horizontally projecting ears 182, 183. Three blind bores 180 are 
provided in the inner side of elongated body 172 for alignment with blind 
bores 144 on cage 130 so as to receive the other end of springs 150 shown 
in FIG. 7. 
Referring particularly to FIG. 6B, the outer surface of trigger 170 
includes a profile 190 configured and dimensioned such that profile 190 
may be received within profile 40 on outer casing hanger 36. In 
particular, trigger 170 includes a lower projecting portion 184, an 
intermediate projecting portion 186, and an upper projecting portion 188 
to be received within annular grooves 70, 72, and 74, respectively, of 
profile 40 on hanger 36. A slot 192 is formed between portions 184, 186 
and a slot 194 is formed between portions 186, 188 for receiving segments 
82, 80, respectively, on profile 40. An aperture 164 is provided through 
portion 184 for assembly purposes in conjunction with threaded bore 146 as 
hereinafter described. 
Trigger 170 includes a projecting, deformable, alignment member or button 
such as a tang 196 which projects from the base of slot 194. Tang 196 has 
a generally triangular bearing surface which may have a truncated apex 
such as 197 or a pointed apex. The apex 197 extends approximately 0.020 
inches below upwardly facing and upwardly tapering arcuate shoulder 86 
formed by annular recess 84 in annular segment 80 of profile 40 on outer 
casing hanger 36. The apex 197 of tang 196 is adapted to deform upon the 
misalignment of trigger 170 with profile 40 so as to ensure that the dogs 
132, 134, 136 are received within annular grooves 70, 72, 74 forming 
profile 40 on outer casing head 36. Tang 196 avoids the requirement of 
stringent tolerances in the alignment of dogs 132, 134, 136 with annular 
grooves 70, 72, 74, respectively. 
;Referring now to FIG. 7, the trigger 170 is mounted on cage 130 by sliding 
ears 182, 183 at the upper terminal end 178 of trigger 170 into expanded 
notch 158 of upper dog 136 behind flanges 159. Springs 150 are received 
within each of the aligned blind bores 180 in trigger 170 and blind bores 
144 in member 138 of cage 130. As trigger 170 is received within channel 
140, each of the springs 150 is compressed so as to bias trigger 170 
outwardly. An installation bolt 168 is received through aperture 164 and 
threaded into threaded bore 146 of cage 130 to maintain trigger 170 and 
cage 130 in the assembled position. 
Referring now to FIGS. 8A and B, there is shown a hinged trigger guard 200. 
Trigger guard 200 includes three hinged sections 201,202, and 203 hinged 
at 204, 205 and 206. Each of the sections 201,202, 203 includes cut outs 
207, 208, 209, respectively, for alignment with flow passages 106, 107, 
and 108 of hanger body 90. Referring particularly to FIG. 8B, there is 
shown hinge 206. The terminal ends of segments 203 and 201 forming hinge 
206 form a T-slot 210. T-slot 210 is configured and dimensioned to 
radially, slidably receive ears 176, 177 on the lower terminal end 174 of 
trigger 170. It should be appreciated that hinge 206 has a construction 
which is identical to hinges 204 and 205. 
It should be appreciated that all components with the exception of hanger 
body 90 and springs 150 may be cast. The present invention separates the 
load carrying function from the triggering function such that the external 
components, with the exception of springs 150, are subjected to 
compressive loads only. This condition allows the use of casting. 
Referring now to FIG. 9, the hanger assemblies 125 are shown mounted on 
inner casing hanger 60. In assembling hanger assembly 125 on one of the 
sets of three lugs, the longitudinal member 138 on cage 130 is aligned 
with vertical channel 116 formed between each of the segments 100, 102, 
104. Further, arcuate dogs 132, 134, 136 are received within the slots 
120, 122, 124, respectively, on hanger body 90. Upon mounting an assembly 
of cage 130 and trigger 170 on each of the three sets 96, 97, 98 of 
segments 100, 102, 104 on hanger body 90, trigger guard 200 is assembled 
with screws at 204, 205 and 206 around the lower terminal end 174 of 
triggers 170 to hold cages 130 and trigger 170 in position on hanger body 
90. Installation bolts 168 are removed to finalize the installation of 
hanger assembly 125. As can be appreciated, ears 176, 177 on the lower 
terminal end 174 of each of the triggers 170 are radially, slidably 
received within each T-slot 210 at each of the hinges 204, 205,206 of 
trigger guard 200. The upper terminal end 178 of trigger 170 is adjacent 
flat 118 of upper segment 104. Hanger assembly 125 is axially, slidably 
mounted on hanger body 90 of inner hanger 60 and is radially contractible 
and expansible with respect to hanger body 90 of inner hanger 60. 
Referring now to FIGS. 10, 11, and 12, FIG. 10 illustrates the assembly of 
cage 130 and trigger 170 on hanger 60 in the running position. FIG. 11 
illustrates the assembly of cage 130 and trigger 170 on hanger 60 in the 
location or triggering position. FIG. 12 illustrates the assembly of cage 
130 and trigger 170 on hanger 60 in the suspending position. 
Referring now to FIGS. 10A, B, C and D in the running position, the 
production casing string 42 suspended in inner casing hanger 60 is lowered 
into the newly drilled borehole on production riser 44. The trigger 170 is 
biased outwardly by springs 150 against the walls of the various tubular 
members forming bore 66. The radial movement of the upper end 178 of 
trigger 170 is limited by the engagement of ears 182, 183 and flanges 159. 
The trigger 170 maintains the cage 130 in its radial inward and contracted 
position. 
Referring now to FIGS. 11A, B, C and D in the triggering position, upon the 
projecting portions 184, 186, 188 of trigger 170 becoming aligned with 
grooves 70, 72, 74, respectively, as inner hanger 60 is lowered with the 
bore 66 of outer head 36, locator tang 196 engages locator surface 86 on 
profile 40 and is received within annular groove 84. Tang 196 is deformed 
if there is a misalignment. Trigger 170 then expands radially outward due 
to springs 150 and is received within profile 40 of outer intermediate 
casing head 36. As trigger 170 moves radially outward into profile 40, 
upper ears or wings 182, 183 and lower ears or wings 176, 177 move 
radially outward within notches 158 and T-slots 210. In this expanded 
radial position, the upper terminal end 178 of trigger 170 moves radially 
out of engagement with downwardly facing stop shoulder 123 on upper lug 
104. 
Referring now to FIGS. 12A, B, C, and D in the suspending position, the 
reception of trigger 170 into profile 40, halts the downward travel of 
trigger 170 with respect to casing head 36. Upon the clearance of the 
triggers 170 with stop shoulders 123, the hanger body 90 of inner hanger 
60 continues its downward longitudinal travel with respect to triggers 
170. In particular, the upper terminal ends 178 of triggers 170 
longitudinally slide onto flat 119 of upper lug 104. As casing hanger 60 
continues to travel downwardly, ears 176, 177 on the terminal end 174 of 
trigger 170 and ears 182, 183 on the upper terminal end 178 of trigger 170 
move out of T-slot 210 of trigger guard 200 and recess 158 at the upper 
end of cage 130 thereby allowing the further downward travel of inner 
hanger 60 and releasing cage 130 from its contracted position. The dogs 
132, 134, 136 of cage 130 are then allowed to also be received within 
grooves 70, 72, 74 of profile 40 with bearing shoulders 154, 156, 157 
engaging bearing surfaces 76 in recesses 70, 72, and 74, such that cages 
130 halt further downward travel. As casing hanger 60 continues its 
downward travel, the inner bearing surfaces 112 of each of the segments 
100, 102, 104 on hanger 60 move into bearing engagement with bearing 
surfaces 148. Likewise outer bearing surface 110 moves into notches 160. 
The further downward movement of hanger 60 allows inner bearing surfaces 
112 of segments 100, 102, 104 to be cammed into engagement with the inner 
arcuate surface 148 of dogs 132, 134, 136 while simultaneously the outer 
bearing surfaces 110 of segments 100, 102, 104 are received within notches 
160 of dogs 132, 134, 136. In its lowermost position, bearing shoulder 161 
engages bearing member 114 and hanger 60 maintains each of the three sets 
of segments in the radially expanded and locked position for supporting 
the casing string 142 within outer casing string 34. 
The present invention provides a hanger suspension system which increases 
the load carrying capacity of the inner hanger 60 by providing a plurality 
of load bearing shoulders between the load bearing members 100, 102, 104 
of inner hanger 60 and dogs 132, 134, 136 of cage 130 and a plurality of 
load bearing shoulders between dogs 132, 134, 136 of cage 130 and load 
bearing surfaces 76 in recesses 70, 72 and 74 of profile 40 and outer head 
36. 
In a cementing operation, a borehole is drilled through the outer casing 
string 34, and hanger 60, supporting inner casing string 42, is lowered 
into the borehole. Upon the inner hanger 60 being received within the bore 
66 of outer head 36, locator tang 196 engages locator shoulder 86 in 
profile 40 due to trigger member 176 being biased outwardly by springs 
150. Upon the alignment of profile 40 with hanger assembly 125, triggers 
170 expand radially outward into profile 40. Inner hanger 60 thereby 
releasing cages 130. Cages 130 are then cammed outwardly into 
circumferential grooves 70, 72, 74 with lugs 100, 102, 104 further 
traveling downward behind cages 130 to maintain cages 130 in load bearing 
relationship with inner hanger 60 and outer head 36. 
Upon the suspension of inner casing string 42 within outer casing string 
34, cement is pumped down the flow bore 92 of inner casing string 42. The 
cement flows around the lower terminal end of inner casing string 42 and 
first up the annulus formed between inner casing string 42 and the earth 
wall of the borehole and then up the annulus formed between inner and 
outer casing strings 42, 34, respectively. As the cement flows through the 
well, the inner hanger 60 and inner casing string 42 may be raised within 
outer casing head 36 and outer casing string 34. The camming shoulders of 
dogs 132, 134, 136 engage the camming surfaces of grooves 70, 72, 74, 
respectively, initially halting the upward movement of cage 130 with 
respect to hanger body 90. Upon bearing surfaces 110, 160 and 112, 148 
disengaging, cages 130 contract radially inward allowing load bearing 
shoulders 154, 156, 157 to disengage load bearing surfaces 76 in grooves 
70, 72, 74. After disengagement, the inner casing string may be raised and 
lowered above profile 40 to assist in the flow of the cement around the 
outside of inner casing string 42 to ensure that the cement fills all 
portions of the annulus around inner casing string 42. The drilling mud 
and cement returns are allowed to pass through linear flow passages 106, 
107, and 108 until the cementing operation is completed. 
Upon the completion of cementing operation, the inner casing string 42 and 
inner hanger 60 are again lowered within bore 66 to re, engage load 
bearing shoulders 154, 156, 157 with load bearing surfaces 76 of 
circumferential grooves 70, 72, 74. The cement is then allowed to set up 
to complete the cementing of the inner string 42 within the borehole. 
While the present invention is described, for purposes of illustration 
only, as used in a mudline casing hanger system, the present suspension 
system may also be useful in other applications in suspending an inner 
tubular member from an outer tubular member in a well such as subsea 
wellheads, through bore surface wellheads, and downhole well tools such as 
liner hangers and well packers.