Patent Publication Number: US-9835008-B2

Title: Method and apparatus for retaining weighted fluid in a tubular section

Description:
FIELD OF THE INVENTION 
     This disclosure relates generally to offshore well drilling operations. More particularly, the invention pertains to installing a well casing into an offshore subsea well using a full column of weighted fluid inside a casing. Specifically, the disclosure relates to a high pressure opening valve assembly designed to be utilized with a full column of weighted fluid inside a casing. 
     BACKGROUND 
     Typically, after a well for the production of oil and/or gas has been drilled, casing will be lowered into and cemented in the well. During cementing, cement is forced down the bore of the casing, through an aperture in the guide shoe at the bottom of the casing, and up the annulus surrounding the casing and between the casing and the wellbore to the desired level. One or more valves, commonly termed float valves, are installed in the casing to prevent back flow of the cement into the casing from the annulus if pressure in the casing is reduced. Such a float valve may be in the form of a collar or an integral part of the guide shoe. The closed float valve or valves also seal the bottom of the casing and prevent fluids in the wellbore from filling it when the casing is lowered into the wellbore. 
     Some offshore applications and in particular, shallow water applications, have a requirement to maintain a full column of weighted fluid (typically drilling fluid or drilling mud), inside the casing string while running it from the rig floor to the sea-floor and into the borehole in riserless applications. Running the casing string full aids in getting the casing to the borehole in a controlled manner, helps to prevent kick and minimizes fluid contamination of wellbore fluids in the well. Kick is a condition where there is an influx of formation fluids into the wellbore. It occurs because the hydrostatic pressure exerted by the column of fluid contained within the wellbore and the drilling riser is not great enough to overcome the pressure exerted by the fluids in the formation drilled. Weighted fluids, such as drilling fluids, are heavier or denser than sea water and exert sufficient pressure to prevent kick. However, a common problem with offshore applications is that, during lowering of the casing to the borehole, the pressure differential between the drilling mud in the casing and the sea water surrounding the casing causes premature actuation of the float valve and allows sea water to displace the drilling mud. The sea water, being less dense than the drilling mud, exerts less of a hydrostatic pressure and thus, can allow kick to occur. 
     Past solutions to this problem have focused on increasing the activation pressure for the float valve; however, such techniques have proven to be problematic and impractical. Accordingly, it would be advantageous to provide a solution to this problem that did not involve increasing the activation pressure of the float valve. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a cross-sectional view of a float apparatus having a float assembly and high opening pressure (HOP) nose in accordance with an embodiment. 
         FIG. 2  is a cross-sectional view of a HOP nose in accordance with an embodiment. The HOP nose is illustrated with the valve element engaging the valve seat. 
         FIG. 3  is a cross-sectional view of the embodiment of  FIG. 2  illustrated with the valve element resiliently disengaged from the valve seat. 
         FIG. 4  is a cross-sectional view of the embodiment of  FIG. 2  illustrated with the valve element non-resiliently disengaged from the valve seat when the differential pressure is above the predetermined high-pressure threshold. 
         FIG. 5  is a cross-sectional view of the embodiment of  FIG. 2  illustrated with the valve element non-resiliently disengaged from the valve seat when the differential pressure is below the predetermined high-pressure threshold. 
         FIG. 6  is a cross-sectional view of an alternative embodiment of a HOP nose suitable for use in the float apparatus. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring now to the drawings, and more particularly to  FIG. 1 , the floating apparatus of the present one embodiment is shown and generally designated by the numeral  10 . Apparatus  10  includes a float assembly  11  and a high opening pressure (HOP) nose  100 . It should be understood that HOP nose  100  can be used on a casing string separately from float assembly  11 ; however, benefits are obtained in using float assembly  11  with HOP nose  100 , especially in offshore applications as hereinafter explained. 
     Focusing now on float assembly  11 , the assembly includes an outer sleeve or outer case  12  which has a first or upper sleeve end  14  and a second or lower sleeve end  16 , an outer surface  18  and an inner surface  20 . In the embodiment shown in  FIG. 1 , the float assembly  11  includes an inner thread  24  at its upper end  14 , and an inner thread  26  at its lower sleeve end  16 , thereby configuring the float assembly  11  to be integrally attached to a casing string thereabove and HOP nose  100  therebelow. Inner surface  20  defines a central flow passage  22 . As illustrated, central flow passage  22  extends from first sleeve end  14  to lower sleeve end  16  and thus, is in fluid flow communication with the interior of a casing string thereabove and with a HOP nose  100  therebelow. 
     A check valve  28  is disposed in outer case  12 . Check valve  28  governs fluid flow through central flow passage  22 . Check valve  28  includes a check valve housing  30  having an upper end  32 , a lower end  34 , an exterior surface  36  and an interior surface  38 . Interior surface  38  defines a central chamber or bore  40  extending from upper end  32  to lower end  34 . Check valve housing  30  may also include a radially outwardly extending lip  42  at its upper end  32 . An annulus  70  is defined between check valve housing  30  and outer sleeve  12 . 
     A check valve seat  44  is defined on interior surface  38 . Check valve  28  further includes a check valve element  46  having a sealing surface  48 , which sealingly engages check valve seat  44 . A lip seal  49  may be defined on sealing surface  48 . A check valve guide  50  disposed in check valve housing  30  slidingly receives a check valve stem  52 , which extends upwardly from check valve element  46 . A check valve cap  54  is attached to an upper end  56  of check valve stem  52 . A check valve spring  58  is disposed about check valve stem  52  between check valve cap  54  and check valve guide  50 . Check valve spring  58  biases check valve cap  54  upwardly thereby sealingly engaging check valve seat  44  and sealing surface  48  of check valve element  46 . 
     The check valve  28  may further include an auto-fill strap  60  attached to the check valve element  46 . Auto-fill strap  60  has a rounded end or bead  62  disposed at each end. Bead  62  may be placed between check valve seat  44  and sealing surface  48  prior to lowering the casing string into a well, thereby allowing fluid to flow through check valve  28  as apparatus  10  is lowered into the well. Once the casing is in place, fluid is pumped into the float equipment forcing check valve element  46  down and releasing the bead  62 . Once fluid flow is stopped, check valve spring  58  will urge check valve stem  52  upwardly, so that sealing element  48  of check valve element  46  sealingly engages check valve seat  44 . In offshore applications, such as described below, this auto-fill function will generally not be utilized. 
     Looking again at annulus  70 , a body portion  72  is disposed in annulus  70 . The body portion  72  has an upper end  74 , which terminates approximately at upper end  32  of check valve housing  30 , and a lower end  76 , which terminates approximately at lower end  34  of check valve housing  30 . Body portion  72  is typically comprised of a high compressive strength cement. 
     Attached to and beneath float assembly  11  is HOP nose  100 . The shoe includes an outer housing  102 , which has a first housing end  104 , a second housing end  106 , an exterior face or surface  108  and an interior face or surface  110 . Interior face  110  defines a central bore  114 . In the embodiment shown in  FIG. 1 , the HOP nose  100  includes an exterior thread  112  at its first housing end  104 , thereby configuring the HOP nose  100  to be integrally attached to float assembly  11 . As illustrated, central bore  114  extends from first housing end  104  to second housing end  106  thus, is in fluid flow communication with the central flow passage  22  of float assembly  11  at first housing end  104  and forms an aperture in exterior face  108  at second housing end  106  therebelow. As can best be seen in  FIG. 2 , central bore  114  has an upper portion  116 , a middle portion  118  and a lower portion  120  (also called stem bore  120 ). Upper portion  116  has an upper diameter  117 , which is greater than middle diameter  119  of middle portion  118  thereby forming an upward facing shoulder referred to as upper interior shoulder  122 . Middle diameter  119  is greater than lower diameter  121  of lower portion  120  and thereby forms an upward facing shoulder referred to as lower interior shoulder  124 . Additionally, lower portion or stem bore  120  can be further defined into three portions: first portion  126 , second portion  128  and third portion  130  having lower diameter  121 , secondary diameter  129  and tertiary diameter  131 , respectively. Secondary diameter  129  is greater than lower diameter  121  and, thus, forms a downward facing shoulder referred to as first stem bore shoulder  125 . Secondary diameter  129  is greater than tertiary diameter  131  and thus, forms an upward facing shoulder referred to as second stem bore shoulder  127 . Preferably, lower diameter  121  is greater than tertiary diameter  131 . In another embodiment, the lower diameter  121  and secondary diameter  129  are equal and, thus, each have lower diameter  121  so that stem bore  120  has second stem bore shoulder  127 ; however, this embodiment does not provide for facilitating the movement of valve guide retainer  148  through stem bore  120  as explained below. 
     As can best be seen from  FIGS. 3 and 4 , an aperture  103  extends from the exterior face  108  to interior face  110 . Aperture  103  is located in middle portion  118  of central bore  114  and, thus, provides fluid flow communication between middle portion  118  and the outside of HOP nose  100 . While only one such aperture  103  is illustrated, generally, there will be a plurality of such apertures located circumferentially about middle portion  118  of HOP nose  100 . 
     Looking now at  FIGS. 1 and 2 , a valve  132  is disposed in central bore  114  of outer housing  102 . Outer housing  102  serves as the housing for the valve and as the outer case for HOP nose  100 . Valve  132 , as illustrated, is a check valve and governs fluid flow through central bore  114 . A valve seat  134  is provided in upper portion  116  of central bore  114 . Valve seat  134  is an insertable valve seat, which can be introduced through central bore  114  at first housing end  104 . Valve seat  134  rests against upper interior shoulder  122 , which holds it in place against downward movement in outer housing  102 . During the lowering of the casing into the wellbore, valve seat  134  is held securely in place from upward movement by friction and drilling fluid pressure in the casing and floating apparatus  10 . If additional restraint is required, pins or a retaining ring can be used to hold valve seat  134  in place. 
     Valve seat  134  has a cylindrical outer surface  136  to match and sealingly engage interior face  110 . Valve seat  134  can be manufactured from any suitable material that is drillable and can withstand the pressures and temperatures encountered during the casing operation. The material can be a plastic, composite or a metal, such as aluminum. Additionally, o-rings (not shown) can be utilized between cylindrical outer surface  136  and interior face  110  to ensure a suitable sealing engagement is achieved. Valve seat  134  has a central aperture  138 , which can have a cylindrical portion  140  and a conical portion  142 . 
     Valve  132  further includes a valve element  144  having a sealing surface  146 , which sealingly engages valve seat  134  at conical portion  142 . A valve guide retainer  148  is disposed in first portion  126  of stem bore  120 . Valve guide retainer  148  has an outer surface  152  and a threaded inner surface  154 . As can be seen from the figures, valve guide retainer  148  has an outer diameter approximately equal to lower diameter  121  such that it fits within lower diameter  121  with outer surface  152  adjacent to the interior face  110  within first portion  126 . Valve guide retainer  148  fits slidingly within first portion  126  but is shearingly attached to interior face  110  by shear pins  156  to prevent movement. The shearing attachment is configured to provide release of valve guide retainer  148  when the pressure above it (towards first housing end  104 ) exceeds a predetermined high-pressure threshold. Thus, before the pins are sheared, valve guide retainer  148  is fixedly attached to interior face  110  and held in place. When the pins are sheared, valve guide retainer  148  can move downwardly (towards second housing end  106 ) through stem bore  120 . 
     A valve guide  158  is disposed in valve guide retainer  148 . Valve guide  158  has a first end  160 , a second end  162  and a threaded outer surface  164 . Threaded outer surface  164  is threadedly engaged with threaded inner surface  154  of valve guide retainer  148 . The threading engagement allows valve guide  158  to be rotated about its longitudinal axis and thereby move towards first housing end  104  (inwardly) or towards second housing end  106  (outwardly). Valve guide  158  slidingly receives a valve stem  168 , which extends downwardly (towards second housing end  106 ) from valve element  144 . A valve sleeve  172  is fixedly mounted on valve stem  168  adjacent to valve element  144 . Stem sleeve  172  has lip  174 . A valve spring  170  is disposed about valve stem  168  between lip  174  and first end  160  of valve guide  158 . Valve spring  170  biases valve element  144  upwardly towards valve seat  134  thereby sealingly engaging valve seat  134  and sealing surface  146  of valve element  144 . In an alternative embodiment illustrated in  FIG. 6 , valve spring  170  is disposed about valve stem  168  between valve element  144  and first end  160  of valve guide  158  without use of stem sleeve  172 . 
     In use in offshore operations, i.e. where a wellbore is at the bottom of a body of water (typically salt water), the float apparatus is first attached to said casing string. While only the HOP nose described above can be attached to the casing string, generally the float assembly and HOP nose will be attached to the casing string. Use of both the float assembly and the HOP nose allows for advantageous control of fluid in the casing based on the differing pressures involved in lowering the casing, drilling fluid circulation processes and cementing processes. 
     If used, the check valve  28  in float assembly  11  will be activated or opened when the pressures differential across the check valve is above a predetermined low-pressure threshold. Because check valve  28  can only activate or open in one direction, the pressure must be greater on the first sleeve end  14  side of check valve  28  than on the second sleeve end  16  side of the check valve  28 . In other words, the check valve will open when the pressure differential across the check valve is greater than the predetermined low-pressure threshold and the fluid pressure is greater in the central flow passage  22  at the first sleeve end  14  than in the central flow passage  22  at the second sleeve end  16 . The predetermined low-pressure threshold will generally be greater than about 5 psi but lower than 50 psi and, typically, from 5 psi to 10 psi. 
     The valve  132  will be resiliently activated or opened when the pressures differential across valve  132  is above a predetermined mid-pressure threshold. Because valve  132  can only activate or open in one direction, the pressure must be greater on the first housing end  104  side of valve  132  than on the second housing end  106  side of valve  132 . In other words, the valve will resiliently open or resiliently allow fluid flow when the pressure differential across the valve is greater than the predetermined mid-pressure threshold and the fluid pressure is greater in the central bore  114  at the first housing end  104  than in the central bore  114  at the second housing end  106 . The predetermined mid-pressure threshold will be greater than the predetermined low-pressure threshold and thus, generally greater than 10 psi. More typically, the predetermined low-pressure threshold can be from about 50 psi to about 150psi, but can be from 50 psi to 100 psi, can be from 100 psi to 150 psi and, typically, can be from 75 psi to 125 psi. 
     Additionally, because valve guide retainer  132  is shearingly attached to outer housing  102 , valve  132  will be non-resiliently activated or opened when the pressures differential across the check valve is above a predetermined high-pressure threshold. The predetermined high-pressure threshold will be greater than the predetermined mid-pressure threshold and thus, with generally be greater than about 150 psi. More typically, the predetermined high-pressure threshold can be greater than about 200 psi and can be greater than 250 psi. Although thresholds are indicated above, generally the basic requirement is that the predetermined low-pressure threshold is lower than either the predetermined mid-pressure threshold or the predetermined high-pressure threshold. Generally, the predetermined mid-pressure threshold is lower than the predetermined high-pressure threshold; however, it is within the scope of the invention that the predetermined mid-pressure threshold not be utilized, i.e. that valve  132  not have a resiliently open mode or that the predetermined mid-pressure threshold be set higher or equal to the predetermined high-pressure threshold. If the predetermined mid-pressure threshold is not utilized, then valve  132  will only open non-resiliently. As used herein, “resiliently open”, “resiliently activate”, “resiliently allow flow” and similar terms refers to a valve opening and allowing flow in a resilient or elastic manner so that if the pressure differential is reduced the valve will close and prevent flow through the valve. As used herein, “non-resiliently open”, “non-resiliently activate”, “non-resiliently allow flow” and similar terms refer to a valve opening and allowing flow in a non-resilient or inelastic manner so that if the pressure differential is reduced the valve will not close and prevent flow through the valve. In other words, when valve  132  resiliently allows flow, it can close and open repeatedly as the pressure differently fluctuates around the predetermined mid-pressure threshold; however, when valve  132  non-resiliently allows flow, it will open when the pressure differential exceeds the high-pressure threshold but will not thereafter close if the pressure differential drops below the high-pressure threshold. 
     As will be understood from the above, the HOP nose contains a one-way check valve that will retain fluid inside the casing at the elevated fluid pressure within a casing string caused by maintaining a full column of weighted fluid (typically drilling fluid or drilling mud), inside the casing string while running it from the rig floor to the sea-floor and into the borehole in riserless applications. The predetermined mid-pressure threshold and/or predetermined high-pressure threshold support a specific predetermined differential pressure caused by the fluid pressure within the casing being greater than the fluid pressure outside the casing. Additionally as explained below, the one-way check valve of the HOP nose can be adjusted to support various hydrostatic forces resulting from fluid inside the casing; that is, the specific predetermine differential pressure supported can be adjusted in accordance to the specific conditions encountered. 
     Prior to lowering the casing string into the well, valve  132  can be adjusted to change the predetermined mid-pressure threshold. Valve guide  158  can be turned so that it is moved inward (toward first housing end  104 ) or outward (toward second housing end  106 ) because of its threaded engagement with valve guide retainer  148 . Moving valve guide  158  inward increases the compression of valve spring  170  thereby increasing the predetermined mid-pressure threshold. Moving valve guide  158  outward decreases the compression of valve spring  170  thereby decreasing the predetermined mid-pressure threshold. 
     The casing string is then lowered through the water and into the wellbore. During the lowering of the casing string the casing is kept full of a weighted fluid. Generally, the weighted fluid is introduced into the casing as it is lowered. Typically, the weighted fluid is a drilling fluid or drilling mud. The density of the weighted fluid is greater than the density of the surrounding water, because of this, in offshore, check valve  28  can be prematurely opened due to the weight or fluid pressure of the weighted fluid. When this happens the weighted fluid can be displaced by water in the casing. Valve  132  prevents this since it opens at a higher pressure differential than check valve  28 . 
     After the casing string is lowered into place in the wellbore, well fluid can be circulated within the casing and wellbore by increasing the fluid pressure of the weighted fluid so that the pressure differential across valve  132  exceeds the predetermined mid-pressure threshold and thereby allowing resilient fluid flow through valve  132 . The fluid flowing through valve  132  can flow into the borehole through aperture  103 , as illustrated in  FIG. 3 . 
     During such resilient fluid flow valve, the increased pressure in the weighted fluid overcomes the biasing of valve spring  170  so that valve element  144  is moved toward second housing end  106  and, hence, disengaged from valve seat  134 . Valve spring  170  is thereby compressed between valve element  144  and valve guide  158  or, if stem sleeve  172  is used, between lip  174  and valve guide  158 . Valve guide retainer  148  remains attached to interior face  110  of outer housing  102 . If the pressure is subsequently reduced below the predetermined mid-pressure threshold, the biasing of valve spring  170  is no longer overcome and valve element  144  returns to engage valve seat  134 . 
     When use of valve  132  is no longer needed or desired, such as during cementing of the casing, the pressure of the weighted fluid can be increased so that the pressure differential across valve  132  exceeds the predetermined high-pressure threshold and thereby allowing non-resilient fluid flow through valve  132 . During such non-resilient fluid flow valve, as the pressure increases so that the pressure differential is between the predetermined mid-pressure threshold and the predetermined high-pressure threshold, the increased pressure in the weighted fluid overcomes the biasing of valve spring  170  so that valve element  144  is moved toward second housing end  106  and, hence, disengaged from valve seat  134 . Valve spring  170  is thereby compressed, as described above, and valve guide retainer  148  remains attached to interior face  110 . As the pressure differential exceeds the predetermined high-pressure threshold, shear pins  156  shear and release valve guide retainer  148  so that it moves toward second housing end  106 . As it passes through second portion  128  of stem bore  120  the increased diameter of second portion  128  facilitates movement by reducing friction between the outer surface  152  of valve guide retainer  148  and interior face  110 . Valve guide retainer  148  next encounters second stem bore shoulder  127 , which stops its movement through stem bore  120  as illustrated in  FIG. 4 . Valve guide retainer  148  has a diameter greater than tertiary diameter  131 ; thus, it can not pass into third portion  130  of stem bore  120  but is stopped by second stem bore shoulder  127 . When the pressure differential is above the predetermined high-pressure threshold valve element  144  can be pushed down into contact with lower interior shoulder  124  as illustrated in  FIG. 4 . Because valve  132  is now non-resiliently open, it is effectively inoperable and, if the pressure differential is subsequently reduced below the predetermined high-pressure threshold or the predetermined mid-pressure threshold, valve element  144  will not return to engage valve seat  134 , as illustrated in  FIG. 5 . 
     At this point, wellbore operations are controlled by check valve  28 . Cement can be flowed down and out the lower end of the casing string. The cement fills an annulus between the outer surface of the casing string and the wellbore, thus cementing the casing in place. Next a displacement fluid is pumped down the casing string to move all the cement through check valve  28  and into the annulus between the outer surface of the casing string and the wellbore. After displacement operations are completed, the casing is filled with displacement fluid and cement is located in the annular space between the casing and the wellbore. At which point, the surface pressure is released such that pressure above check valve  28  is less than the pressure below check valve  28  and check valve  28  closes; that is check valve element  46  comes into sealing contact with check valve seat  44 . Thus, check valve  28  holds the cement in place by creating a barrier for holding differential pressure. 
     In accordance with the above description, several specific embodiments will now be described. In one embodiment there is provide a HOP assembly for a fluid filled casing string. The HOP assembly comprises a housing configured to attach to the casing string. The housing contains an adjustable one-way check valve. Hydrostatic forces resulting from fluid inside the casing string creates a pressure differential across the adjustable one-way check valve. The adjustable one-way check valve supports the hydrostatic forces such that it remains closed up to a first predetermined pressure differential so as to retain the casing string in a fluid filled sate. The one-way check valve is adjustable such that the first predetermined pressure differential can be increased or decreased. 
     Additionally, the adjustable one-way check valve can non-re-resiliently allow fluid flow when a second predetermined pressure differential is exceeded. The second predetermined pressure differential being equal to or greater than the first predetermined pressure differential. 
     Further, the second predetermined pressure differential can be greater than the first predetermined pressure differential and, when the pressure differential is between the first predetermined pressure differential and the second predetermined pressure differential, the adjustable one-way check valve resiliently allows fluid flow. 
     In another embodiment there is provided a HOP nose for a casing string. The HOP nose comprising a housing and a valve positioned within the housing. The housing has a first housing end configured for attachment to a casing string; a second housing end; an exterior face extending from the first housing end to the second housing end; an interior face extending from the first housing end to the second housing end and defining a central bore; and an aperture extending from the exterior face to the interior face. The valve is positioned in the bore. The valve is configured such that, when there is a pressure differential between the first housing end and the aperture below a predetermined mid-pressure threshold, the valve element prevents fluid flow between the first housing end and the aperture. The valve is further configured such that, when the pressure differential exceeds a predetermined high-pressure threshold, the valve non-resiliently allows fluid flow from the first housing end to the aperture. 
     In a first application of the above embodiment, the predetermined mid-pressure threshold can be equal to the predetermined high-pressure threshold. In a second application of the above embodiment, the predetermined mid-pressure threshold is less than the predetermined high-pressure threshold. In this second application, when the pressure differential is from the predetermined mid-pressure threshold to the predetermined high-pressure threshold, the valve resiliently allows fluid flow from the first housing end to the aperture. 
     In a further embodiment, the valve can comprise a valve seat, a valve element, a valve guide retainer, a valve guide, a valve stem and a spring. The valve seat can be located in the central bore. The valve element can have a sealing surface sealingly engageable with the valve seat. The valve guide retainer can be attached to the housing and have an interior face defining a retainer passage. The valve guide can have a stem passage there through. The valve guide extending through the retainer passage and attached to the interior face of the valve guide retainer. The valve stem can extend from the valve element and through the valve guide with the valve stem being slidably received through the valve guide. A spring can be between the valve element and valve guide, and provide a biasing force such that the valve element sealingly engages the valve seat until the pressure differential reaches the predetermined mid-pressure threshold. 
     Further, the valve element can sealing engage the valve seat when the pressure differential is below the predetermined mid-pressure threshold; resiliently disengages from the valve seat when the pressure differential is from the predetermined mid-pressure threshold to the predetermined high-pressure threshold and non-resiliently disengages from the valve seat when the pressure differential is above the predetermined high-pressure threshold. Also, the valve guide can be threadedly connected to the valve guide retainer such that turning the valve guide increases the biasing force exerted on the valve element and the valve guide and, thusly, increases the predetermined mid-pressure threshold. Additionally, the valve guide retainer can be shearingly attached to the housing such that when the pressure differential exceeds the predetermined high-pressure threshold, the valve guide retainer detaches from the housing. 
     In a further embodiment the first housing end of the HOP nose can be attached to a float assembly comprising an outer sleeve, a check valve and a body portion. The outer sleeve can have a first sleeve end configured to be connected to the well casing, a second sleeve end attached to the first end of the housing of the HOP nose, an outer surface and an inner surface, wherein the inner surface defines a central flow passage. The check valve can be disposed in the central flow passage. The check valve comprising a check valve housing having an interior surface defining a central chamber in fluid flow communication with the central flow passage and an exterior surface opposing the inner surface of the outer sleeve. The exterior surface and inner surface define an annulus between the valve housing and the outer sleeve. The body portion fixedly attached to the housing and the outer sleeve. The body portion fills the annulus. 
     In the float assembly, the check valve can further comprise a check valve seat, a check valve guide, a check valve element and a check valve stem. The check valve seat can be defined on the check valve housing. The check valve guide can be disposed in the central chamber of the check valve housing. The check valve element can have a sealing surface sealingly engageable with the check valve seat. The check valve stem can extend upwardly from the check valve element and be slidably received through the check valve guide. 
     In another embodiment there is provided a float apparatus comprising a float assembly and a HOP nose. The float assembly has an outer sleeve, a check valve and a body portion. The outer sleeve has a first sleeve end configured to be connected to the well casing, a second sleeve end, an outer surface and an inner surface. The inner surface defines a central flow passage. The check valve is disposed in the central flow passage. The check valve comprises a check valve housing. The check valve housing has an interior surface defining a central chamber in fluid flow communication with the central flow passage and an exterior surface opposing the inner surface of the outer sleeve. The exterior surface and inner surface define an annulus between the valve housing and the outer sleeve. When there is a first pressure differential between the first sleeve end and the second sleeve end less than a predetermined low-pressure threshold, the check valve prevents fluid flow through the central passage. When the first pressure differential is greater than the predetermined low-pressure threshold, the valve allows fluid flow through the central passage. The body portion is fixedly attached to the housing and the outer sleeve such that the body portion fills the annulus. 
     The float shoe has a housing and a valve positioned in the housing. The housing has a first housing end attached to the second sleeve end; a second housing end; an exterior face extending from the first housing end to the housing second end; an interior face extending from the first housing end to the second housing end and defining a central bore; and an aperture extending from the exterior face to the interior face. The valve is positioned in the bore. The valve is configured such that, when there is a second pressure differential between the first housing end and the second housing end below a predetermined mid-pressure threshold, the valve element prevents fluid flow between the first housing end and the aperture. The valve is further configured such that when the pressure differential exceeds the predetermined high-pressure threshold, the valve non-resiliently allows fluid flow from the first housing end to the aperture. 
     In yet another embodiment there is provided a method of placing a casing string having an interior into a wellbore at the bottom of a body of water. The method comprising:
         (a) attaching a HOP nose to the casing string, the HOP nose having an interior and an aperture, which allows fluid flow communication between the interior of the HOP nose and the outside of the HOP nose;   (b) lowering the casing through the water and into the wellbore;   (c) introducing a fluid into the interior of the casing, the fluid having a fluid pressure;   (d) during the lower lowering step (b), preventing fluid flow communication between the interior of the casing and the aperture of the HOP nose when the fluid pressure is below a predetermined mid-pressure threshold;   (e) after the lowering of step (b), preventing fluid flow communication between the interior of the casing and the aperture of the HOP nose only when the fluid pressure is below a predetermined low-pressure threshold, wherein the predetermined low-pressure threshold is less than the predetermined mid-pressure threshold.       

     In the above method the density of the fluid can be less than the density of the water of the body of water. Further, fluid flow communication is controlled by a first check valve and a second check valve. The first check valve resiliently allowing fluid flow communication when the fluid pressure is at or above the predetermined low-pressure threshold and the second check valve resiliently allowing fluid flow communication when the fluid pressure is at or above the predetermined mid-pressure threshold. 
     The method can further comprise, after the lowering step (b), the step of disabling the second check valve such that it non-resiliently allows fluid flow communication above and below the predetermined mid-point threshold. Also, the step of disabling the second check valve can comprise increasing the fluid pressure to above a predetermined high-pressure threshold wherein the predetermined high-pressure threshold is greater than the predetermined mid-pressure threshold. 
     In the above description terms such as up, down, lower, upper, upward, downward and similar have been used to describe the placement or movement of elements. It should be understood that these terms are used in accordance with the typical orientation of a casing string; however, the invention is not limited to use in such an orientation but is applicable to use with other orientations. Also, it will be seen that the apparatus of the present invention and method of use of such an apparatus are well adapted to carry out the ends and advantages mentioned as well as those inherent therein. While the presently preferred embodiment of the invention has been shown for the purposes of this disclosure, numerous changes in the arrangement and construction of parts may be made by those skilled in the art. All such changes are encompassed within the scope and spirit of the dependent claims.