Patent Description:
Aspects of the present disclosure relate to a float valve assembly for use in a drill string to control fluid flow through the drill string when drilling a wellbore.

Float valves are downhole safety valves that prevent unwanted uphole flow of fluids through a drill string when drilling a wellbore. A highly density fluid, commonly referred to as drilling mud, is usually pumped down through the drill string to assist a drill bit connected to the lower end of the drill string when drilling the wellbore. However, sometimes a sudden high pressure area in the wellbore can cause fluid to flow back up the drill string. The float valves are configured to permit fluid flow down through the drill string and prevent fluid flow back up the drill string.

Although there are many different types of float valves, there is a continuous need for new and/or improved float valve assemblies.

<CIT> describes a check valve for a drill string, where the check valve may be incorporated in a drilling bottom hole assembly. A drilling method is also described, the method comprising running a drill string into a bore, and reconfiguring a check valve located towards the distal end of the drill string from a running configuration.

In a first embodiment, a float valve assembly according to claim <NUM> is provided.

In a second embodiment, a drill string assembly comprises an upper drill string portion; a lower drill string portion; and a float valve assembly according to the first embodiment, wherein the float sub is disposed between the upper drill string portion and the lower drill string portion.

In a third embodiment, a method for drilling a wellbore according to claim <NUM> is provided.

So that the manner in which the above-recited features of the disclosure can be understood in detail, a more particular description of the disclosure, briefly summarized above, may be had by reference to embodiments, some of which are illustrated in the appended drawings.

The disclosure contemplates that terms such as "couples," "coupling," "couple," and "coupled" may include but are not limited to welding, interference fitting, and/or fastening such as by using bolts, threaded connections, pins, clips, and/or screws. The disclosure contemplates that terms such as "couples," "coupling," "couple," and "coupled" may include but are not limited to direct coupling and/or indirect coupling, such as indirect coupling through components such as links.

<FIG> is a perspective view of a float valve assembly <NUM>, according to one embodiment. <FIG> is another perspective view of the float valve assembly <NUM>. <FIG> is a side view of the float valve assembly <NUM>. <FIG> is a sectional view of the float valve assembly <NUM>.

With reference to <FIG>, the float valve assembly <NUM> comprises a first float valve <NUM> coupled to a second float valve <NUM> in a stacked configuration. The coupling of the first and second float valves <NUM>, <NUM> together prevents independent movement relative to each other. If not connected together, the first and second float valves <NUM>, <NUM> may potentially impact one another if simply placed next to each other when installed in drill string. Specifically, pressurized fluid flow through the float valve assembly <NUM> may push one against the other and cause damage to the first and second float valves <NUM>, <NUM>.

The first float valve <NUM> comprises an outer housing <NUM>, a seal assembly <NUM>, and a plunger valve <NUM>. The outer housing <NUM>, also referred to as a cage, may be in the form of a cylindrical body <NUM> having a bore <NUM> formed through the cylindrical body <NUM>. One or more openings <NUM> are formed through the sidewalls of the cylindrical body <NUM>.

The seal assembly <NUM> is coupled to an upper end of the outer housing <NUM>. The seal assembly <NUM> comprises an upper seal <NUM> and a lower seal <NUM> disposed about the upper end of the outer housing <NUM>. The upper seal <NUM> seals against fluid flowing down against the outer surface of the outer housing <NUM>, and the lower seal <NUM> seals against fluid flowing up against the outer surface of the outer housing <NUM>. The seal assembly <NUM> therefore is configured to seal against fluid flow in both directions across the seal assembly <NUM>.

The plunger valve <NUM> is coupled to the outer housing <NUM> and disposed in the bore <NUM>. The plunger valve <NUM> comprises a valve member <NUM>, a seal <NUM>, a seal support member <NUM>, a biasing member <NUM>, and a valve guide <NUM>. The valve member <NUM> comprises an upper valve head <NUM> and a lower valve stem <NUM>. The upper valve head <NUM> is in the shape of a cone, and the lower valve stem <NUM> is in the shape of a cylindrical rod. The seal <NUM> is positioned against a lower surface of the upper valve head <NUM>, and the seal support member <NUM> is positioned against a lower surface of the seal <NUM>. The biasing member <NUM> is positioned between the seal support member <NUM> and the valve guide <NUM>, which is coupled to and at least partially extends through an inner shoulder <NUM> of the outer housing <NUM>.

The valve guide <NUM> comprises a bore <NUM> through which the lower valve stem <NUM> extends, and an outer shoulder <NUM> which abuts the inner shoulder <NUM> of the outer housing <NUM>. One end of the biasing member <NUM> pushes against the outer shoulder <NUM> of the valve guide <NUM>, and the opposite end of the biasing member <NUM> pushes against the seal support member <NUM>. In this arrangement, the biasing member <NUM> forces the upper valve head <NUM> and the seal <NUM> against an inner sealing surface <NUM> of the outer housing <NUM>.

When the seal <NUM> is in sealing contact with the inner sealing surface <NUM>, the plunger valve <NUM> of the first float valve <NUM> is in a closed position, which prevents fluid flow through the first float valve <NUM>. When an amount of pressurized fluid is applied to the upper surface of the upper valve head <NUM> sufficient to overcome the bias force of the biasing member <NUM>, the upper valve head <NUM> and the seal <NUM> are moved out of sealing contact with the inner sealing surface <NUM>, thereby compressing the biasing member <NUM> between the seal support member <NUM> and the valve guide <NUM>, and allowing fluid flow through the bore <NUM> and past the plunger valve <NUM>. When the seal <NUM> is not in sealing contact with the inner sealing surface <NUM>, the plunger valve <NUM> of the first float valve <NUM> is in an open position, which allows fluid flow through the first float valve <NUM>.

The second float valve <NUM> comprises an outer housing <NUM>, a seal assembly <NUM>, and a plunger valve <NUM>. The outer housing <NUM>, also referred to as a cage, may be in the form of a cylindrical body <NUM> having a bore <NUM> formed through the cylindrical body <NUM>. One or more openings <NUM> are formed through the sidewalls of the cylindrical body <NUM>.

When the seal <NUM> is in sealing contact with the inner sealing surface <NUM>, the plunger valve <NUM> of the second float valve <NUM> is in a closed position, which prevents fluid flow through the second float valve <NUM>. When an amount of pressurized fluid is applied to the upper surface of the upper valve head <NUM> sufficient to overcome the bias force of the biasing member <NUM>, the upper valve head <NUM> and the seal <NUM> are moved out of sealing contact with the inner sealing surface <NUM>, thereby compressing the biasing member <NUM> between the seal support member <NUM> and the valve guide <NUM>, and allowing fluid flow through the bore <NUM> and past the plunger valve <NUM>. When the seal <NUM> is not in sealing contact with the inner sealing surface <NUM>, the plunger valve <NUM> of the second float valve <NUM> is in an open position, which allows fluid flow through the second float valve <NUM>.

The lower end of the outer housing <NUM> of the first float valve <NUM> comprises a female threaded connection <NUM>, and the upper end of the outer housing <NUM> of the second float valve <NUM> comprises a male threaded connection <NUM>. Alternatively, the lower end of the outer housing <NUM> may comprise the male threaded connection <NUM>, and the upper end of the outer housing <NUM> of the second float valve <NUM> may comprise the female threaded connection <NUM>. The female threaded connection <NUM> is threadedly coupled to the male threaded connection <NUM> to couple the outer housings <NUM>, <NUM> together such that the first float valve <NUM> and the second float valve <NUM> are connected together in a stacked configuration. When the first and second float valves <NUM>, <NUM> are coupled together in a stacked configuration, the outer housings <NUM>, <NUM> are not able to move relative to each other. The benefit of the outer housings <NUM>, <NUM> not being able to move relative to each other is that damage to the outer housings <NUM>, <NUM> is prevented, which may be caused when pressurized fluid flows through the first and second float valves <NUM>, <NUM> and forces one of the outer housings <NUM>, <NUM> to impact against the other outer housing if not coupled together.

<FIG> is a sectional view of the float valve assembly <NUM> coupled to a drill string <NUM> in a wellbore <NUM>, according to one embodiment. <FIG> illustrates the float valve assembly <NUM> in an open position. <FIG> is another sectional view of the float valve assembly <NUM> coupled to the drill string <NUM> in the wellbore <NUM>, according to one embodiment. <FIG> illustrates the float valve assembly <NUM> in a closed position.

The drill string <NUM> comprises one or more tubular members coupled together above the float valve assembly <NUM>, referred to as an upper drill string portion 200A, and below the float valve assembly <NUM>, referred to as a lower drill string portion 200B. The lower drill string portion 200B comprises a drill bit <NUM> configured to drill the wellbore <NUM>. The upper drill string portion 200A extends to the surface from which the wellbore <NUM> is drilled. The drill string <NUM> is coupled to opposite ends of a float valve sub <NUM> of the float valve assembly <NUM>. Thus the float valve assembly <NUM> itself forms part of the drill string <NUM> that is lowered into the wellbore <NUM> to drill the wellbore <NUM>.

The float valve sub <NUM> is in the form of a cylindrical body <NUM> having a bore <NUM> disposed through the float valve sub <NUM>. The first and second float valves <NUM>, <NUM> are coupled together and disposed within the bore <NUM> of the float valve sub <NUM>. The lower end of the float valve sub <NUM> comprises a female threaded connection <NUM>, and the upper end of the lower drill string portion 200B comprises a male threaded connection <NUM>. The female threaded connection <NUM> is threadedly coupled to the male threaded connection <NUM> to couple the float sub <NUM> and the lower drill string portion 200B together such that the first and second float valves <NUM>, <NUM> are secured within the float valve sub <NUM>. Specifically, the upper end of the first float valve <NUM> abuts against an inner shoulder <NUM> of the float valve sub <NUM>, and the upper end of the lower drill string portion 200B abuts against the lower end of the second float valve <NUM>.

Similarly, the upper end of the float valve sub <NUM> comprises a female threaded connection <NUM>, and the lower end of the upper drill string portion 200A comprises a male threaded connection <NUM>. The female threaded connection <NUM> is threadedly coupled to the male threaded connection <NUM> to couple the float sub <NUM> and the upper drill string portion 200A together. Alternatively, the female and male threaded connections may be switched between the float valve sub <NUM> and the drill string <NUM>.

The seal assemblies <NUM>, <NUM> of the first and second float valves <NUM>, <NUM> seal against an inner surface <NUM> of the float valve sub <NUM>. The seal assemblies <NUM>, <NUM> are configured to prevent fluid flow between the outer surface of the first and second float valves <NUM>, <NUM> and the inner surface <NUM> of the float valve sub <NUM>.

With reference to <FIG>, as the drill string <NUM> is being lowered into and/or while drilling the wellbore <NUM>, a fluid <NUM> is pumped down through the upper drill string portion 200A, through the float valve assembly <NUM>, and out through the lower end of the lower drill string portion 200B. The fluid <NUM> is pumped at a pressure sufficient to overcome the bias force of the biasing members <NUM>, <NUM>, and move the plunger valves <NUM>, <NUM> of the first and second float valves <NUM>, <NUM> to an open position to allow fluid flow through the float valve assembly <NUM>.

With reference to <FIG>, in the event that the pressure in the wellbore <NUM> is sufficient to push a fluid <NUM> back up through the drill string <NUM> in the opposite direction, the fluid <NUM> and/or the biasing members <NUM>, <NUM> then move the plunger valves <NUM>, <NUM> of the first and second float valves <NUM>, <NUM> to the closed position to prevent fluid flow up through the float valve assembly <NUM>. Although the second float valve <NUM> itself can stop the upward fluid flow, the first float valve <NUM> is provided as a back-up if the second float valve <NUM> fails. The float valve assembly <NUM> allows fluid flow down and out through the lower end of the drill string <NUM> and prevents fluid flow back up through the drill string <NUM>.

The float valve assembly <NUM> is similar to the float valve assembly <NUM>, the primary difference being that the float valve assembly <NUM> comprises flapper valves <NUM>, <NUM> instead of plunger valves <NUM>, <NUM>. Corresponding components between the float valve assembly <NUM> and the float valve assembly <NUM> are identified with the same reference numbers. A full description of the corresponding components with respect to the float valve assemblies <NUM>, <NUM> will not be repeated for brevity.

The flapper valves <NUM>, <NUM> are configured to allow fluid flow through the float valve assembly <NUM> in one direction, and prevent fluid flow through the float valve assembly <NUM> in the opposite direction. The first float valve <NUM> comprises the flapper valve <NUM>, and the second float valve <NUM> comprises the flapper valve <NUM>.

The flapper valve <NUM> comprises a valve member <NUM>, a seal <NUM>, a seal support member <NUM>, a biasing member <NUM>, and a biasing retention member <NUM>. The valve member <NUM> is pivotably coupled to the outer housing <NUM> by a pin member <NUM> that extends through a shoulder of the outer housing <NUM>. The seal <NUM> is positioned within a recessed portion formed in the bore <NUM> of the outer housing <NUM>. The seal support member <NUM> is positioned about the seal <NUM> to help secure the seal <NUM> in place. The biasing member <NUM> is disposed about the pin member <NUM> and biases against a lower surface of the valve member <NUM>. The biasing retention member <NUM> helps secure the biasing member <NUM> to the valve member <NUM>. In this arrangement, the biasing member <NUM> forces the valve member <NUM> against the seal <NUM>.

When the valve member <NUM> is in sealing contact with the seal <NUM>, the flapper valve <NUM> of the first float valve <NUM> is in a closed position, which prevents fluid flow through the first float valve <NUM>. When an amount of pressurized fluid is applied to the upper surface of the valve member <NUM> sufficient to overcome the bias force of the biasing member <NUM>, the valve member <NUM> is moved out of sealing contact with the seal <NUM>, thereby compressing the biasing member <NUM>, and allowing fluid flow through the bore <NUM> and past the flapper valve <NUM>. When the valve member <NUM> is not in sealing contact with the sea <NUM>, the flapper valve <NUM> of the first float valve <NUM> is in an open position, which allows fluid flow through the first float valve <NUM>.

When the valve member <NUM> is in sealing contact with the seal <NUM>, the flapper valve <NUM> of the second float valve <NUM> is in a closed position, which prevents fluid flow through the second float valve <NUM>. When an amount of pressurized fluid is applied to the upper surface of the valve member <NUM> sufficient to overcome the bias force of the biasing member <NUM>, the valve member <NUM> is moved out of sealing contact with the seal <NUM>, thereby compressing the biasing member <NUM>, and allowing fluid flow through the bore <NUM> and past the flapper valve <NUM>. When the valve member <NUM> is not in sealing contact with the sea <NUM>, the flapper valve <NUM> of the second float valve <NUM> is in an open position, which allows fluid flow through the second float valve <NUM>.

<FIG> is a sectional view of the float valve assembly <NUM> coupled to the drill string <NUM> in the wellbore <NUM>, according to one embodiment. <FIG> illustrates the float valve assembly <NUM> in an open position. <FIG> is another sectional view of the float valve assembly <NUM> coupled to the drill string <NUM> in the wellbore <NUM>, according to one embodiment. <FIG> illustrates the float valve assembly <NUM> in a closed position.

Similar to the float valve assembly <NUM>, the drill string <NUM> is coupled to opposite ends of the float valve sub <NUM> of the float valve assembly <NUM>. Thus the float valve assembly <NUM> itself forms part of the drill string <NUM> that is lowered into the wellbore <NUM> to drill the wellbore <NUM>.

With reference to <FIG>, as the drill string <NUM> is being lowered into and/or while drilling the wellbore <NUM>, the fluid <NUM> is pumped down through the upper drill string portion 200A, through the float valve assembly <NUM>, and out through the lower end of the lower drill string portion 200B. The fluid <NUM> is pumped at a pressure sufficient to overcome the bias force of the biasing members <NUM>, <NUM>, and move the flapper valves <NUM>, <NUM> of the first and second float valves <NUM>, <NUM> to an open position to allow fluid flow through the float valve assembly <NUM>.

With reference to <FIG>, in the event that the pressure in the wellbore <NUM> is sufficient to push the fluid <NUM> back up through the drill string <NUM> in the opposite direction, the fluid <NUM> and the biasing members <NUM>, <NUM> then move the flapper valves <NUM>, <NUM> of the first and second float valves <NUM>, <NUM> to the closed position to prevent fluid flow up through the float valve assembly <NUM>. Although the second float valve <NUM> itself can stop the upward fluid flow, the first float valve <NUM> is provided as a back-up if the second float valve <NUM> fails. The float valve assembly <NUM> allows fluid flow down and out through the lower end of the drill string <NUM> and prevents fluid flow back up through the drill string <NUM>.

<FIG> illustrate different types of connections that can be used to couple the outer housings <NUM>, <NUM> together for either float valve assembly <NUM>, <NUM>. <FIG> illustrates that the outer housings <NUM>, <NUM> can be coupled together by a welded connection <NUM>, and/or by a set screw/pin connection comprising one or more set screws or pins <NUM> that can be disposed through the side wall of the outer housing <NUM> and protrude into one or more corresponding slots or holes <NUM> in the side wall of the outer housing <NUM>. <FIG> illustrates that the outer housings <NUM>, <NUM> can be coupled together by a conical, taper, cam, magnetic, spring enabled, and/or glue type lock, schematically illustrated as a locking connection <NUM>, that is integrally formed with or coupled to the connecting ends of the outer housings <NUM>, <NUM>. <FIG>, which is not forming part of the claimed subject-matter, illustrates that the outer housings <NUM>, <NUM> may be integrally formed as a single, monolithic outer housing <NUM> configured to support both of the plunger valves <NUM>, <NUM> and/or the flapper valves <NUM>, <NUM>.

Claim 1:
A float valve assembly (<NUM>, <NUM>) for use in a drill string (<NUM>) while drilling a wellbore (<NUM>), comprising:
a float sub (<NUM>);
a first float valve (<NUM>) having a first outer housing (<NUM>) and a first seal assembly (<NUM>) including a first upper seal (<NUM>) and a first lower seal (<NUM>) each disposed about the first outer housing; and
a second float valve (<NUM>) having a second outer housing (<NUM>) and a second seal assembly (<NUM>) including a second upper seal (<NUM>) and a second lower seal (<NUM>), wherein the first outer housing and the second outer housing are disposed within the float sub in a stacked configuration, wherein the first outer housing and the second outer housing are coupled together such that the first outer housing and the second outer housing are prevented from moving independently from one another, and wherein
the first seal assembly and the second seal assembly seal against an inner surface (<NUM>) of the float sub.