Patent Grant
8678110
Not applicable
Not applicable
1. Field of the Invention
The present invention relates to oilfield valves. More particularly, the present invention relates to a mud saver valve when installed to prevent the loss of drill fluid during starting operation in deep water wells using a combination of static fluid pressure and flow pressure to open the valve and mechanical spring forces to close the valve.
2. General Background of the Invention
When drill pipe and other tubular strings are lowered into or raised out of a well bore, including, but not limited to, during the drilling of the wellbore, it is quite common, particularly in the oil and gas field, for the drill pipe and other tubular strings to be filled with mud of the type used in drilling techniques. The mud would typically be pumped into the upper end of the drill string after it has been connected to the drill string below it and/or as it is being lowered into a wellbore. As the next joint is added to the drill string, the connection is typically disconnected from the drill string to allow the next section of drill pipe to be connected to the string. When the fluid connection is disconnected, there should preferably to be a mud saver valve in place to retain this fluid and prevent it from flowing out onto the work area and environment. The advantages of using such a valve are well known and include saved mud cost, decreased chances of pollution, and increased safety to rig personnel. To avoid this loss of mud during these types of operations there is needed a mud saver valve which could be positionable just above the drilling bit or just below the bend sub to prevent the loss of drill fluid during starting operation in deep water wells, which reduces the amount of drilling fluid required to start a well and reduces the pollution of the mud bottom with drilling fluid and weighting material.
This invention replaces the original Mud Saver Valve, as disclosed U.S. patent application Ser. No. 12/652,547, noted above, which utilized a pre charged nitrogen dome chamber to feed pre charge pressure to the closing side of multiple pistons that are arranged in an equally spaced circular pattern around the center axis of the valve. The force created by the pre charge pressure acting on the multiple pistons force a slidable sleeve to close the fluid pathway through the valve.
To force the original Mud Saver Valve to open its fluid pathway through the valve, pressure inside the drill pipe at the valve's location in the well bore has to rise above the pre charge pressure of the nitrogen dome plus whatever pressure is required to overcome the friction force of the piston seals. To accomplish this either direct hydrostatic head pressure or the combination of direct hydrostatic head pressure and flow pressure generated by the mud pumps are required.
With the original Mud Saver Valve the amount of pump pressure required to open the valve is a function of the depth of the tool in the well bore. The deeper the tool, the higher the hydrostatic head pressure and the lower the pump pressure required to open the valve.
With the original Mud Saver Valve the valve could be set to open at any particular depth by adjusting the nitrogen pre charge pressure prior to entering the well bore.
The following U.S. patents are incorporated herein by reference:
The mud saver valve of the present invention solves the problems in the art in a simple and straightforward manner.
In summary, the new Mud Saver Valve II replaces the nitrogen dome with a mechanical compression spring that is compressed during the valve assembly process to a certain pre load found in the original Mud Saver Valve discussed above. This mechanical spring pre load provides the closing force acting on the valve's Mud Saver Valve II also opens the closing side of the multiple pistons to the annulus pressure at the valve location depth in the well bore.
Further, as with the original Mud Saver Valve, the opening side of the multiple pistons are fed with the pressure in the drill pipe at the valve's location depth in the well bore.
Further, in a static condition without flow if the fluid mud in the annulus and the fluid mud in the drill pipe are the same weight per unit volume then (neglecting friction in the piston seals) the differential pressure working across the multiple actuator pistons is zero.
The new pump pressure required to open the new Mud Saver Valve II is no longer a function of the depth of the valve in the well bore. The pump pressure required to open the new Mud Saver Valve II, at any well bore depth, is only a function of the mechanical compression spring pre load and whatever pressure is required to overcome the friction of the piston seals.
In the new Mud Saver Valve II design the amount of friction of the piston seals can be dramatically reduced by converting to mechanical labyrinth type seal. Labyrinth seals have no physical contact between the sealing surfaces. As a consequence of this the friction of the seal is eliminated. However, a small amount of leakage will pass through the seal. The amount of fluid following through the valve can be 12 barrels per min. (504 gal./min (1908 Liters/min)). The small amount of leakage past the two (2) 0.625 inch (1.59 cm) diameter pistons is thought to be negligible.
For a further understanding of the nature, objects, and advantages of the present invention, reference should be had to the following detailed description, read in conjunction with the following drawings, wherein like reference numerals denote like elements and wherein:
Prior to a discussion of the drawing figures, it should be kept in mind that the overall function of the Mud Saver Valve II and Mud Saver Valve with Concentric Pistons is the same as the original Mud Saver.
When the rig's mud pumps that circulate mud down the drill pipe to the drill bit at the bottom of the well bore and then return the mud, contaminated with drilled shavings, up the annulus to the BOP stack and finally either take the returning mud up the (subsea riser/spool) or (choke/kill lines) are off, a mechanical device in the original Mud Saver Valve and modified mechanical devices in the Mud Saver Valve II and Mud Saver Valve with Concentric Pistons force these valves to their closed positions and do not allow mud to flow through them.
When the rig's mud circulating pumps are turned on pressures working on respective mechanical devices in each of these three (3) Mud Saver Valve designs force the valves to open and allow the mud to flow through the valves.
The overall function of these valves is to capture the large volume of conditioned clean mud that is in the drill pipe from just above the drill bit at the bottom of the well bore up to the rig floor. These Mud Saver Valves will not allow the clean mud in the drill pipe to drain out of the bottom of the pipe and into the contaminated mud in the annulus as individual pipe stands are tripped in and out of the well bore.
The original Mud Saver Valve uses a pre charged nitrogen dome chamber to feed pre charge pressure to the closing side of multiple pistons that are arranged in an equally spaced circular pattern around the center axis of the valve. The force created by the pre charge pressure acting on the multiple pistons force a slidable sleeve to close the fluid pathway through the valve.
To force the original Mud Saver Valve to open its fluid pathway through the valve, pressure inside the drill pipe at the valve's location in the well bore has to rise above the pre charge pressure of the nitrogen dome plus whatever pressure is required to overcome the friction force of the piston seals. To accomplish this either direct hydrostatic head pressure or the combination of direct hydrostatic head pressure and flow pressure generated by the mud pumps are required.
With the original Mud Saver Valve the amount of pump pressure required to open the valve is a function of the depth of the tool in the well bore. The deeper the tool, the higher the hydrostatic head pressure and the lower the pump pressure required to open the valve.
With the original Mud Saver Valve the valve could be set to open at any particular depth by adjusting the nitrogen pre charge pressure prior to entering the well bore.
The new Mud Saver Valve II replaces the nitrogen dome with a mechanical compression spring that is compressed during the valve assembly process to a certain pre load. This mechanical spring pre load provides the closing force acting on the valve's Mud Saver Valve II also opens the closing side of the multiple pistons to the annulus pressure at the valve location depth in the well bore.
As with the original Mud Saver Valve, the opening side of the multiple pistons are fed with the pressure in the drill pipe at the valve's location depth in the well bore.
In a static condition without flow if the fluid mud in the annulus and the fluid mud in the drill pipe are the same weight per unit volume then (neglecting friction in the piston seals) the differential pressure working across the multiple actuator pistons is zero.
The new pump pressure required to open the new Mud Saver Valve II is no longer a function of the depth of the valve in the well bore. The pump pressure required to open the new Mud Saver Valve II, at any well bore depth, is only a function of the mechanical compression spring pre load and whatever pressure is required to overcome the friction of the piston seals.
In the new Mud Saver Valve II design the amount of friction of the piston seals can be dramatically reduced by converting to mechanical labyrinth type seal. Labyrinth seals have no physical contact between the sealing surfaces. As a consequence of this the friction of the seal is eliminated. However, a small amount of leakage will pass through the seal. The amount of fluid following through the valve can be 12 barrels per min. (504 gal./min (1908 liters/min)). The small amount of leakage past the two (2) 0.625 inch (1.59 cm) diameter pistons is thought to be negligible.
Turning now the drawing Figures, first
The annulus pressure is fed through annulus pressure feed port 3 to the closing side of valve actuator-piston 34 at valve actuator-piston close valve pressure side 42.
The pressure inside the drill string or pipe 17 which with the same weight fluid in the pipe 17 and annulus is equal to the annulus pressure is fed down inlet fluid conductor 6 to the valve actuator radial port through valve actuator radial port 7 and into inlet fluid cavity between the valve actuator housing and the valve actuator sliding sleeve 8, where it is blocked by sliding sleeve 32 and fed to valve actuator-piston open valve pressure side 41. Since the annulus and pipe pressure are equal the differential pressure across the pistons 34 is zero and the springs 24 pre load holds the valve closed.
From Alternate Embodiment Operation
Recent testing of the Mud Saver Valve II, as represented in
The first area of interest is the two (2) small pistons represented in
Piston 74, 84 of
This design represented in
The second area of interest is the Pin End (bottom) Sliding Sleeve Seal represented as sliding sleeve main seal 33 of
The Pin End (bottom) Sliding Sleeve Seal may be cut or otherwise damaged as it passes over the radial ports. The relatively low closing force of the spring may not allow the valve to close if part of the damaged seal gets caught up in the Sliding Sleeve mechanism.
In the alternate embodiment the Pin End (bottom) Sliding Sleeve Seal is made larger in diameter and moved to an alternate embodiment of the Cage. Reference
The new alternate embodiment of the Sliding Sleeve, alternate valve actuator-sliding sleeve (Open/close) 82 of
The annulus pressure is fed through Alternate Annulus Pressure Feed Port-Kidney Shaped 71 at Valve Actuator-Piston Close Valve Pressure Side 42.
The pressure inside the pipe which with the same weight per unit volume of fluid in the pipe and annulus is equal to the annulus pressure is fed down Inlet Fluid Conductor 6 to the Valve Actuator Radial Port 7 and into Inlet Fluid Cavity 8 between the Valve Actuator Housing 40 and the Valve Actuator Sliding Sleeve 82 where it is blocked by alternate valve actuator-sliding sleeve (open/close) 82 and fed to Valve Actuator-Piston Open Valve Pressure Side 41.
Since the mud pumps are turned off and the fluid in the pipe has the same weight per unit volume as the fluid in the annulus then the pipe and annulus pressures are equal and the differential pressure across the pistons 84, 74 is zero and the pre load force of the spring 24 holds the valve closed.
Fluid flows down inlet fluid conductor 6 and then through the radial ports 7 where the fluid then enters inlet fluid cavity 8 before flowing through Cage Radial Ports 55 and entering The Orifice Inlet 56. The flow across Fixed Orifice 52 creates a pressure differential across Fixed Orifice 52. For all practical purposes the pressure differential across fixed orifice 52 is approximately equal to the pressure differential across pistons 84, 74. The pressure at Orifice Inlet 56 is approximately equal to the pressure at valve actuator-piston open 41 and the pressure at Orifice Outlet 57 is approximately equal to the pressure at valve actuator-piston close 42.
Practically the Orifice can be considered to be anything from valve actuator-piston open 41 through the drill bit 83 that creates any pressure drop (restriction). High flow rates with high pressure drops will insure that the valve stays completely open. If the flow rate drops the valve will throttle itself working the pressure differential across the pistons 84, 74 against the spring preload of spring 24.
Finally, if the fluid in the drill string or pipe 17 and the fluid in the annulus have the same weight per unit volume then the cracking pressure of the valve at any depth is equal to the cracking pressure of the valve at sea level. Therefore, there is no longer a concern about the valve opening because the hydrostatic pressure due the tool's depth and the weight of the fluid per unit volume in the pipe exceeded the spring cracking pressure.
The following is a list of parts and materials suitable for use in the present invention.
All measurements disclosed herein are at standard temperature and pressure, at sea level on Earth, unless indicated otherwise. All materials used or intended to be used in a human being are biocompatible, unless indicated otherwise.
The foregoing embodiments are presented by way of example only; the scope of the present invention is to be limited only by the following claims.
Priority of U.S. Provisional Patent Application Ser. No. 61/320,037, filed 1 Apr. 2010, incorporated herein by reference, is hereby claimed.
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| Number | Date | Country | |
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| 20110240300 A1 | Oct 2011 | US |
| Number | Date | Country | |
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| 61320037 | Apr 2010 | US |
