Thin Wall Active Casing Hanger

Abstract

A wellbore system includes a housing assembly and first and second position casing hangers supported by the housing assembly. A load member is provided that is adapted to extend between the first position casing hanger and the housing assembly to enable the housing assembly to support the first position casing hanger. The second position casing hanger is stacked onto the first position casing hanger, and an interface is defined between the first and second position casing hangers to aid in alignment and centralization of the second position casing hanger during installation. The interface also provides radial support to the first position casing hanger and enables loads associated with the second position hanger to be transferred to the housing assembly through the load member.

What is claimed is: 
     
         1 . A wellhead system comprising:
 a wellhead with a bore;   a first position casing hanger in the bore and comprising an upper end, a lower end, and an axial passage, the lower end of the first position casing hanger including a first connector connected to a first casing string;   a second position casing hanger in the bore and comprising an elongated annular body that extends into the axial passage of the first position casing hanger, and a second connector connected to a second casing string; and   a centralizing ring set in an annular space between the elongated annular body and the first position casing hanger, so that when the first position casing hanger deflects radially inward in response to axial loads, the centralizing ring supports the first position casing hanger.   
     
     
         2 . The wellhead system of  claim 1 , wherein the first position casing hanger is supported by at least one upward-facing shoulder defined within the bore of the wellhead, and wherein the centralizing ring defines a support surface that is disposed at a longitudinal elevation of the at least one upward-facing shoulder. 
     
     
         3 . The wellhead system of  claim 2 , wherein the at least one upward-facing shoulder comprises a toothed profile that selectively receives a radial expandable load member therein, and wherein the support surface of the centralizing ring is disposed longitudinally between upper and lower ends of the toothed profile. 
     
     
         4 . The wellhead system of  claim 1 , wherein the first position casing hanger includes a circumferential shelf extending around an upper end thereof, wherein the second position casing hanger includes an upper end extending radially outward from the elongated annular body and defining a downward-facing ledge thereon, the downward-facing ledge abutting the circumferential shelf to support the second position casing hanger. 
     
     
         5 . The wellhead system of  claim 1 , wherein an annular space is between a support surface of the centralizing ring and the first position casing hanger when the first position casing hanger is unloaded. 
     
     
         6 . The wellhead system of  claim 1 , wherein an interference fit is established between a support surface of the centralizing ring and the first position casing hanger when the first position casing hanger is unloaded. 
     
     
         7 . The wellhead system of  claim 1 , wherein the axial passage selectively receives a drill bit prior to installation of the second position casing hanger. 
     
     
         8 . The wellhead system of  claim 1 , wherein the centralizing ring includes a lower taper extending between an exterior surface of the elongated annular body and a support surface defined at a radially outer edge of centralizing ring for guiding the second position casing hanger to a central location with respect to the axial passage of the first position casing hanger. 
     
     
         9 . The wellhead system of  claim 1 , wherein the centralizing ring includes a plurality of radially spaced segments defining flow channels therebetween, and wherein a support surface defined around an outer periphery of the centralizing ring is interrupted by the flow channels. 
     
     
         10 . The wellhead system of  claim 9 , wherein the flow channels occupy about half a cross-sectional area of an annulus defined between an exterior surface of the elongated body and the first position casing hanger. 
     
     
         11 . The wellhead system of  claim 1 , wherein the centralizing ring defines a continuous support surface circumscribing the centralizing ring, and where at least one bore extends longitudinally through the centralizing ring to provide fluid communication through the centralizing ring. 
     
     
         12 . A wellhead system comprising:
 a wellhead housing;   an upper hanger mounted in an axial bore in the wellhead housing;   a lower hanger mounted in the axial bore and circumscribing the upper hanger, and comprising sidewalls that deflect radially inward in response to axial loading of the upper hanger; and   a centralizing ring strategically disposed adjacent to where the sidewalls deflect and between the upper and lower hangers.   
     
     
         13 . The wellhead system of  claim 12 , wherein the upper hanger is stacked onto the lower hanger such that weight suspended from the upper hanger is transferred to the lower hanger. 
     
     
         14 . The wellhead system of  claim 12 , wherein the centralizing ring includes a longitudinally elongated support surface defined at a radially outer edge thereof. 
     
     
         15 . The wellhead system of  claim 12 , wherein the centralizing ring is strategically disposed in a longitudinal support region from which a weight suspended from the first hanger is transferred to the wellhead housing. 
     
     
         16 . The wellhead system of  claim 12 , wherein at least one fluid flow channel extends longitudinally through the centralizing ring. 
     
     
         17 . A wellhead system, comprising:
 a wellhead with an axial bore;   a first position casing hanger in the bore and comprising an axial passage;   a first casing string connected to the first position casing hanger;   a second position casing hanger in the bore and comprising an elongated annular body that extends into the axial passage of the first position casing hanger;   a second casing string connected to the second position casing hanger;   a centralizing ring in an annular space between the elongated annular body and the first position casing hanger, so that when the first position casing hanger deflects radially inward in response to axial loads, the centralizing ring supports the first position casing hanger;   an annular load ring comprising an inner profiled circumference that engages an outer surface of the first position casing hanger, and an outer profiled circumference that engages an inner surface of the wellhead within the axial bore to define a longitudinal support region; and   a first channel in the wellhead that intersects the axial bore above and below the longitudinal support region.   
     
     
         18 . The wellhead system of  claim 17 , further comprising a second channel in the second position casing hanger extending between the axial bore and the axial passage.