U.S. patent number 3,698,426 [Application Number 05/058,825] was granted by the patent office on 1972-10-17 for mud saver valve and method.
This patent grant is currently assigned to Smith International, Inc.. Invention is credited to Mason Rawleigh Litchfield, Floyd Logan Scott, Jr..
United States Patent |
3,698,426 |
Litchfield , et al. |
October 17, 1972 |
MUD SAVER VALVE AND METHOD
Abstract
A mud saver valve assembly is connected between the lower end of
the kelly and uppermost joint of drill pipe, the assembly including
a downwardly opening spring loaded poppet valve and an upwardly
opening ball check valve. The downstream face of the poppet is
shielded from line pressure by a sealed air chamber at atmospheric
pressure in such a manner that the resultant force of downstream
pressure on the poppet tends to open the poppet. Before adding
another joint to the drill string the mud pump is shut down and the
pressure gage checked to make sure there is no pressure in the
drill string, any pressure in the drill string being transmitted
through the ball check valve. If there is pressure it is bled off
through a bleed off valve, if possible. With pressure down, the
connection between the mud saver valve assembly and drill string is
broken and a connection is made between the mud saver valve
assembly and a joint of pipe in the mouse hole. No mud escapes from
the kelly since the hydrostatic head of mud in the kelly is not
sufficient to open the poppet valve in the mud saver valve
assembly. The added joint of pipe is connected to the drill string
still in the hole and the mud pump is turned on, automatically
opening the poppet valve to restore circulation. The new joint is
checked for leaks and if okay the drill string is lowered and
drilling resumed. Since the downstream side of the poppet is
shielded from mud pressure the pressure drop across the valve need
not equal the spring force to hold the valve open, whereby pump
horsepower is not wasted and whereby rapid valve erosion is
eliminated. If on opening the bleeder valve, drill string pressure
is not relieved, it is possible to close the blow out preventers
and reverse circulate to kill the pressure in the formation, the
poppet valve being full open under well pressure thereabove in the
kelly transmitted by the ball check valve, the atmospheric chamber
below the poppet enabling the poppet to stay open when there is
well pressure in the kelly sufficient to overcome the spring bias
tending to close the poppet.
Inventors: |
Litchfield; Mason Rawleigh
(Houston, TX), Scott, Jr.; Floyd Logan (Houston, TX) |
Assignee: |
Smith International, Inc.
(N/A)
|
Family
ID: |
22019152 |
Appl.
No.: |
05/058,825 |
Filed: |
July 29, 1970 |
Current U.S.
Class: |
137/512.1;
137/496; 166/325 |
Current CPC
Class: |
E21B
21/106 (20130101); Y10T 137/7783 (20150401); Y10T
137/7839 (20150401) |
Current International
Class: |
E21B
21/00 (20060101); E21B 21/10 (20060101); F16k
003/02 () |
Field of
Search: |
;137/512,512.1,515,515.3,515.5,515.7,536,537,496,516.25,327
;166/106,224 ;251/360 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Nelson; M. Cary
Assistant Examiner: Wright; William H.
Claims
We claim:
1. Drilling fluid saver valve assembly comprising a tubular body
having means at both ends thereof for making connection with other
fluid conducting members,
wall means dividing said body into first and second portions,
said wall means having a passage therethrough interconnecting said
portions, with means around said passage forming a valve seat,
valve closure means having a seating surface engageable with said
seat to prevent fluid flow through said passage,
resilient means urging said valve closure means to a position in
which said seating surface engages said seat,
means providing an area subject to pressure in said first portion
for moving said closure to a position in which said seating surface
is away from said seat,
means in said second portion defining a chamber sealed off from the
rest of the interior of said tubular body,
a portion of said closure being exposed to the pressure of the
fluid within said chamber, and
valve means to transmit fluid pressure from said second portion to
said first portion when the said seating surface is in engagement
with said seat.
2. Assembly according to claim 1 wherein said chamber is
substantially filled with air at substantially atmospheric
pressure.
3. Assembly according to claim 1 wherein said seat is of hyperbolic
radial cross section and said closure is of elliptical radial cross
section.
4. Assembly according to claim 3 including an O-ring seal in said
seating surface.
5. Assembly according to claim 1 wherein said valve means comprises
at least one ball check valve in said wall means.
6. Assembly according to claim 5 including a plurality of said ball
check valves azimuthally spaced apart around said seat.
7. Assembly according to claim 1 wherein the effective area of said
closure means exposed to pressure in said second portion of the
valve acts, when subjected to such pressure, in a direction to move
said seating surface away from said seat.
8. Assembly according to claim 1 wherein the effective area of said
surface subjected to pressure in said first portion of the valve
body when the seating surface moves away from the seat acts, when
subjected to said pressure, in a direction to move said seating
surface away from said seat.
9. Assembly according to claim 1 wherein said resilient means
exerts a force sufficient to hold said seating surface against said
seat when said area means tending to move the seating surface away
from said seat is subject to a pressure of 60 pounds per square
inch.
10. Drilling fluid saver valve assembly comprising a tubular body
having means at both ends thereof for making connection with other
fluid conducting members,
means forming a valve seat between said ends of said body, the
portion of said body between one of said ends and said seats
constituting a first portion of said body and the remainder of said
body constituting a second portion,
said seat having a passage therethrough interconnecting said
portions, said seat extending around said passage and facing from
said first portion toward said second portion,
an axially movable member mounted in said body and including valve
closure means having a seating surface engageable with said seat to
prevent fluid flow through said passage,
resilient means urging said valve closure means to a position in
which said seating surface engages said seat,
means providing an area subject to pressure in said first portion
for moving said closure to a position in which said seating surface
is away from said seat,
means in said second portion defining a chamber sealed off from the
rest of the interior of said tubular body,
a portion of said axially movable member being exposed to the
pressure of the fluid within said chamber, and
valve means to transmit fluid pressure from said second portion to
said first portion when the said seating surface is in engagement
with said seat.
11. Assembly according to claim 10 wherein said chamber comprises
first chamber forming means stationary relative to said body and
defining a cavity, said chamber further comprising second chamber
forming means extending from said closure means sealingly engaged
with said cavity defining means but allowing relative motion of
said closure means and said cavity defining means.
12. Assembly according to claim 11 wherein one of said chamber
forming means is spaced radially inwardly from said tubular body
forming a fluid path therebetween for fluid flowing in said second
portion of said body and fluid passage means through said one of
said chamber forming means to connect said fluid path with said
second portion of the valve body at the adjacent end of said valve
body.
13. Assembly according to claim 11 wherein said first chamber
forming means is a cup having support means at its bottom to
support it on said valve body in radially spaced relationship,
forming therebetween an annular flow passage, there being fluid
passages past said support means connecting said annular flow
passage with the second portion of said valve body at the adjacent
end thereof.
14. Assembly according to claim 13 wherein said valve body includes
a main section to which is screwed a sub which engages said support
means.
15. Assembly according to claim 14 wherein said resilient means
bears at one end against said first chamber forming means and at
the other end against the second said chamber forming means, said
seat faces said second portion of said valve body and said closure
means is limited in its travel by engagement of said seating
surface thereof with said seat.
16. Assembly according to claim 15 wherein said means forming a
seat is screwed into said valve body.
17. Assembly according to claim 11 wherein said means extending
from said closure is a tube telescopically engaging said cavity
defining means which is also tubular.
18. Assembly according to claim 17 wherein there is a sliding seal
means between said cavity defining means and said means extending
from said closure means.
19. Assembly according to claim 17 wherein said cavity defining
means is a cup having support means spacing it radially inwardly
from said valve body providing an annular fluid passage
therebetween for conducting fluid from said first portion of the
valve body past said chamber to the second portion of said valve
body at the adjacent end thereof.
20. Assembly according to claim 19 wherein said support means
includes azimuthally spaced apart webs at the bottom of said cup
engaging a shoulder on the inner periphery of said valve body.
21. Assembly according to claim 20 wherein said valve body includes
a main section and a sub screwed thereto providing said
shoulder.
22. Assembly according to claim 17 wherein a part of said tubular
cavity defining means is of larger interior cross sectional area
than the cross-sectional area of the outer perimeter of an adjacent
part of said tubular means extending from said closure whereby
there is defined between said parts an annular space, said
resilient means being disposed in said annular space.
23. Assembly according to claim 17 wherein there is port means
through one of said parts of said tubular means that form said
cavity, said port means communicating said annular space with
another space.
24. Assembly according to claim 22 wherein said resilient means is
a Belleville spring.
25. Assembly according to claim 22 wherein said closure means is
adapted to enter said annular space and close off the end thereof
against entrance of fluid passing through the assembly.
26. Assembly according to claim 17 wherein said cavity defining
means is a cup, said tube and cup providing means guiding said
poppet in its reciprocation relative to the seat.
27. Assembly according to claim 26 wherein said cup has a bottom
providing a stop contacted by the end of said tube to limit opening
movement of said poppet.
28. Assembly according to claim 9 wherein said spring force is
insufficient to hold said seating surface against said seat when
said pressure on said area means exceeds 350 pounds per square
inch.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention pertains to valves and more particularly to a valve
assembly of the type known as a kelly foot valve or mud saver valve
used in the rotary system of drilling oil wells.
2. Brief Description of the Prior Art
A gravity opened, stinger closed kelly foot valve is shown in U. S.
Pat. No. 3,191,905 to Brown. This valve will open when the kelly is
connected to the joint of drill pipe in the mouse hole, whereby the
mud in the kelly will be lost. The valve is therefore not adapted
for mouse hole operation.
A full opening flapper gate type spring loaded pressure release,
kelly foot valve is shown in U.S. Pat. No. 3,289,691 to Kennard.
However flapper gate valves may not seal tightly to retain mud in
the kelly.
A spring loaded poppet type pressure release kelly foot valve is
shown in U.S. Pat. No. 3,331,381 to Taylor. However no means is
provided to communicate drill pipe pressure to the mud pressure
gage after the mud pump is shut down to warn the operator prior to
breaking the drill pipe connection to the valve.
A later U. S. Pat. No. 3,433,252 to Kennard shows a kelly foot
valve of the pressure and spring actuated rotary plug type. This
valve may be rather expensive to manufacture.
The combination of an upwardly opening ball check valve in the seat
of a downwardly opening spring loaded poppet type pressure release
valve is shown in U. S. Pat. No. 2,749,992 to Hill. However there
is no suggestion that such a valve assembly be used as a kelly foot
valve to indicate the presence of drill string pressure to warn the
operator prior to breaking the connection between the kelly and
drill pipe whereby the pressure can be relieved before the
connection is broken.
Various means have been used to keep a spring loaded, kelly foot
valve open without the necessity of a pressure drop across the
valve equal to the force exerted by the bias spring. In the Kennard
rotary, ball plug, kelly foot valve construction, an annular piston
is geared to the ball and the upper piston head is exposed to
upstream pressure and the lower piston head is sealed off from the
fluid passage. In the Kennard flapper gate kelly foot valve
construction shown in his earlier patent a similar annular piston
drive is used, the piston being exposed to upstream pressure on one
side and to the pressure in a sealed chamber on the other side.
Such arrangements require a more complicated valve structure than
the simple poppet valve employed in the present invention.
Furthermore, in none of these constructions is there incorporated
any means to admit drill string pressure to the kelly when the
poppet is closed, such as to cause the poppet to open and permit
reverse circulation.
SUMMARY OF THE INVENTION
According to the invention the difficulties with the foregoing
prior art constructions are avoided by providing at the lower end
of a kelly a mud saver valve assembly including a downwardly
opening spring loaded poppet valve and between the seat of the
poppet and the valve body an upwardly opening ball check valve. The
lower face of the poppet is shielded from upwardly acting line
pressure by being disposed in a sealed gas chamber at atmospheric
pressure, the sides of the poppet slidably, sealingly engaging the
sides of chamber. The shielding is such that the resultant force on
the poppet due to downstream pressure acts to close the poppet;
this being accomplished by making the chamber of larger diameter
than the poppet seat. This has the further advantage that when the
poppet opens it enters the top of the chamber to keep out flowing
mud which might deposit cuttings in the chamber.
With such construction a novel method of adding a joint of drill
pipe to a drill string becomes possible comprising shutting down
the mud pumps, determining from the mud pressure gage the existence
of any drill string pressure. If any exists, eliminating it, and
thereafter breaking in the connection between the drill pipe and
mud saver valve assembly, which is automatically closed against
downflow of mud due to hydrostatic pressure in the kelly, making a
connection between the mud saver valve assembly and a joint of pipe
in the mouse hole while leaving the kelly foot valve closed to
prevent loss of the mud, elevating the joint of pipe out of the
mouse hole and connecting it to the drill pipe in the hole,
starting the mud pump which automatically opens the mud saver valve
and starts mud circulation, checking the newly added joint of drill
pipe for leaks, and if no leaks are found, lowering the drill
string to resume drilling. In eliminating drill string pressure
prior to breaking the connection of the drill pipe and mud saver
valve, as is desirable to prevent injury to the operator, the bleed
off valve in the stand pipe is first opened. If that is not
effective, it is then possible to close the blow out preventers and
reverse circulate, e.g. with heavy mud, to kill formation pressure,
the poppet valve of the mud saver valve assembly being full open
due to drill string pressure being transmitted to the kelly above
the poppet by the ball check valve and the lower face of the poppet
being sealed off from line pressure.
BRIEF DESCRIPTION OF THE DRAWINGS
For a detailed description of a preferred embodiment of the
invention reference will now be made to the accompanying drawings
wherein:
FIGS. 1-3 are half sections through the upper sub, body, and lower
sub of a mud saver valve assembly embodying the invention;
FIG. 4 is a bottom view of the sealed chamber forming part of the
assembly shown in FIG. 2, as indicated by line 4--4 of FIG. 3;
and
FIG. 5 is a pictorial view of a drill rig and well bore
illustrating the method of the invention.
DESCRIPTION OF PREFERRED EMBODIMENT
Referring to FIGS. 1-3, there is shown a mud saver valve assembly
comprising an upper sub or short length of pipe 10, a tubular valve
body 11 and a lower sub 12. The upper sub is provided with a
tapered threaded box 13 forming part of a susual rotary shouldered
connection by means of which the mud saver valve can be connected
on to the pin at the lower end of a kelly or other drill string
member. The lower end of sub 12 is provided with a tapered threaded
pin 14 forming part of a usual rotary shouldered connection by
means of which the mud saver valve assembly can be connected to a
box at the upper end of a drill pipe or other drill string
member.
The lower end of sub 13 is provided with a cylindrically threaded
box 17 at the upper end of the valve body 11, there being shoulders
18, 19 on the box and pin to form a seal as the pin root and box
mouth are axially stressed by tight makeup. Also, there is an
O-ring seal 20 provided around the small end of the pin 16 seal
with the inside of body 11.
The upper end of sub 12 is provided with a cylindrically threaded
pin 26 which is screwed into a cylindrically threaded box 27 at the
lower end of the valve body 11, there being shoulders 28, 29 on the
box and pins to form a seal as the pin root and box mouth are
axially stressed by the tight make up. Also, there is an O-ring
seal 30 provided around the small end of the pin 26 to seal with
the inside of body 11.
There is a fluid passage axially through the mud saver valve
assembly including passage 32 through sub 10, passage 33 through
body 11, and passage 34 through sub 12.
Referring now particularly to FIG. 2, a seat ring 40 is provided
with an external cylindrical thread 41 by means of which it is
screwed into a cylindrical thread 42 on the interior of the valve
body. An O-ring 43 provides a seal at the upper end of the threads
and a further O-ring 44 carried by the seat ring at its upper end
provides a further seal between the seat ring and valve body.
Annularly disposed about the seat ring are one or more upwardly
opening ball check valves 50 such as shown at 50. Each valve 50
includes an inlet passage 51, a seat tube 52 screwed into the seat
ring at the upper end of passage 51, and a ball 53 adapted to rest
on and seal with an annular tapered seat 54 in the seat tube. There
are a plurality of outlet ports 55 in the seat tube. A plug 56 is
screwed in to the upper end of the seat tube to retain the
ball.
There is a flow passage 60 through the seat ring 40. At the lower
end of the flow passage the flow passage flares downwardly
providing a hyperbolically tapered seat 61.
A poppet or valve closure 70 has an elliptically tapered upper face
providing a seating surface 71 in which is disposed an O-ring 72
adapted to seal with seat 61 when the valve is closed. Depending
from poppet 70 is a tubular skirt 75 which slides telescopically
inside the cylindrical interior 76 of a tubular cup 77 (see also
FIG. 4). The outer periphery 78 of the side wall 79 of the cup is
generally cylindrical and is spaced radially from the enlarged
inner periphery 79 of the valve body forming an annular flow
passage 80 therebetween. The cup 77 is provided with webs 81 at its
lower end which rest on the bevel 82 at the upper end of pin 20 of
the lower sub.
There is an enlarged cylindrical bore 90 in the upper part of the
side 79 of cup 77, forming a shoulder 91 at the end of the enlarged
bore. A belleville spring 92 bears at its lower end against
shoulder 91 and at its upper end against an annular flange 93
around skirt 75. A pair of oppositely facing annular lip seal 94,
95 carried by flange 93 seal between the flange 93 of skirt 75 and
the bore 90 of the tubular cup 77.
A port 96 communicates the annular space 97 between cup and skirt
occupied by spring 92 with the space 98 inside cup 77 and skirt 75
whereby any mud leaking past seals 94, 95 will pass into the sump
space 98 to prevent hydraulic locking of the valve. The chamber
defined by the cup and skirt, enclosing spaces 97, 98, contains air
at atmospheric pressure when the mud saver valve assembly is
initially assembled and it is intended that sliding seal means 94,
95 will keep mud, water, or other drilling fluid out of the
cup-skirt chamber whereby the gas pressure in the chamber will
remain substantially atmospheric. Since mud is not an elastic
fluid, a considerable amount of mud leakage can occur without the
gas pressure in the chamber formed by the cup and skirt rising
greatly above atmosphere.
The forces beneath poppet 70 tending to close the poppet are the
force of spring 92 (prestressed in compression when assembled) plus
the force of atmospheric pressure in spaces 97, 98 on the underside
of flange 93 and the underside of the poppet skirt and the
underface of the poppet inside the skirt.
The downstream line pressure acts upwardly on the annular area 99
of the underside of the poppet outside skirt 75, but this pressure
also acts downwardly on the larger annular area of the upper face
of flange 93 and the annular area on top of the poppet outside
O-ring 72, the net effective area being such as to create a
downward force.
Other forces acting down on poppet 70 tending to open the valve are
initially the force of gravity on the poppet plus the force of the
upstream pressure acting on the exposed area of the upper-face 100
of the poppet plus the force of an indeterminate pressure between
upstream and downstream pressure acting on the seating surface 72
of the poppet.
When the valve opens, seating surface 72 will be exposed to
upstream line pressure, and the net effective area of the poppet
previously exposed to downstream line pressure will be exposed to a
pressure equal to upstream line pressure less the pressure drop
across the poppet. This will tend to open the valve fully once it
starts to open despite the slight increase in the force exerted by
long prestressed belleville spring 92 as it is compressed and
despite the slight increase in the air pressure in the cup-skirt
chamber as the poppet moves down and compresses the gas. The
chamber is large compared to the poppet travel from closed to open
position, e.g. a ratio of 5 to 1, so that such gas pressure
increase is not great.
The spring 92 is prestreassed to exert sufficient force on the
poppet to keep it closed under the hydrostatic pressure of a column
of drilling mud in the kelly beneath which the mud saver valve
assembly is connected. For example, assuming a 43 foot kelly full
of 16 pounds per gallon density drilling mud, the mud pressure
would be about 40 pounds per square inch. Assuming further, as an
approximation, that the net effective area exposed to downstream
pressure where zero and that the area of the poppet exposed to mud
weight equaled the area of the poppet, skirt and flange exposed to
air pressure of the chamber, the spring force would have to exceed
that due to the difference between the mud pressure and air
pressure acting over the area exposed to the mud. With a pressure
difference of 40 minus 15 or 25 pounds per square inch and an area
of 3 square inches, the spring load would be somewhat in excess of
75 pounds, e.g. 100 pounds to insure tight closure of the poppet
valve.
With a mud pump pressure of the order of 1,000 pounds per square
inch, the valve will of course open fully when the mud pump is
turned on. Since the mud pressure is shielded by the skirt-cup
chamber from the underside of the poppet except for a net effective
area directed downwardly, and since the seat area of the poppet is
exposed to full upstream pressure when the valve opens, once the
valve opens it opens fully without the need for a pressure drop
across the valve just to keep it open.
When the poppet opens, it can move down until the skirt 75 bottoms
in cup 77. The lower part of the cup acts as a guide for the skirt
during this motion. The volume reduction of the air or gas in the
cup-skirt chamber will be equal to the area circumscribed by bore
90 multiplied by the poppet travel. As previously stated, the
initial volume of the chamber is large compared to this volume
reduction, e.g. a ratio of 5 to 1. The poppet moves down to the cup
preventing drilling mud flowing through the valve from depositing
any debris or, especially in the case of reverse circulation, any
cuttings, into the cup, and preventing erosion of the cup, skirt,
and seals 94, 95 by the turbulent abrasive mud.
The belleville spring 97, which comprises a plurality of
alternately oppositely directed conical washers, preferably exerts
an initial force not in excess of 100% of the weight of a column of
drilling mud in the kelly to which the mud saver valve assembly is
connected which mud has a specific gravity of three. Since most
drilling muds have a density of not over 24 pounds per gallon, this
will insure that the spring will hold the poppet shut with only the
hydrostatic pressure of mud in the kelly but will open when the mud
pump is turned on. It may be noted here that it is uncertain what
gas pressure will exist in the kelly above the mud column when the
pump is shut down, but if there exists atmospheric pressure at the
top of the kelly, e.g. as the result of opening a bleed valve to
reduce the drill string pressure, there may be atmospheric pressure
in the kelly above the mud column. However the atmospheric pressure
above the mud column will be offset by the atmospheric pressure in
the cup-skirt chamber acting in opposition. Therefore the poppet
will stay closed if there is no fluid pressure in the kelly other
than that of the mud and the atmosphere.
Since the belleville spring urges the poppet towards its seal and
urges the cup 77 down against pin 20 which supports the webs 81, it
is apparent that the poppet and the cup-skirt chamber are captured
between the seat ring 40 and the pin 20 on the lower sub. The
spaces between the azimuthally spaced apart webs 81 provide fluid
paths through the cup connecting with the fluid passage 80 formed
between the cup and valve body.
When the valve assembly needs to be cleaned it is easily
disassembled by unscrewing the lower sub 12. On reassembly, the
spacing between shoulder 28 and seat 40 is set so that the
belleville sping is properly compressed when the lower sub is made
up tight. If for any reason it is desired not to break the
connection with the lower sub, the upper sub can be disconnected,
the seat ring unscrewed and the poppet and cup withdrawn by the
tools screwed into sockets 103, 104.
In the foregoing description of the mud saver valve assembly
reference has been made to the net effective area. By effective
area is meant the projection of the area subject to pressure on a
plane perpendicular to the direction of the force that is most
effective and cause a desired effect, e.g. in the case of the
poppet, forces most effective to open and close the valve are
directed axially. By net is meant the algebraic sum, e.g. in the
case of oppositely directed areas, the difference between such
areas, or in the case of like directed areas, the sum thereof. By
direction of an area is meant the direction perpendicular to the
area going into the surface presenting such area.
In considering the operation of the poppet valve, it is perhaps
best to consider the poppet, skirt, and flange 73 as one part,
which may be called the valve closure. Reference may be made to
such element in the claims appended hereto, especially in
connection with the specification of the net effective areas
thereof subject to various pressures.
Although the invention is described as relating to a mud saver
valve assembly it is clear that it is also useful with other
drilling fluids such as water or oil. Therefore the device may also
be called a drilling fluid saver assembly. Furthermore, though the
assembly has been described as being made as a separate unit, it
could be integrated with the kelly saver sub or even with the
kelly. For example upper sub 10 could be the usual kelly saver sub,
since the upper sub does not serve to retain any of the inner parts
of the valve which are captured between the seat ring and lower
sub. It is only necessary that enough area on the outer surfaces be
provided to accommodate tongs for making and breaking connections
where desired. For example, if sub 10 is to be the kelly saver sub,
the sub 10 and valve body 11 should have enough length and be soft
enough to accommodate tongs.
Referring not to FIG. 5 there is shown the mud saver valve assembly
110 whose details are shown in FIGS. 1-4. The valve assembly 110 is
connected to the lower end of a kelly 111, the kelly being a tube
of non-circular, e.g. square outer periphery having screw
connection means at its opposite ends, e.g. a pin 112 at its lower
end connected to the box of a kelly saver sub 114 whose pin is
connected to the box 13 (FIG. 1) of the mud saver valve assembly
110 and a pin 115 at its upper end connected to a swivel 116. The
combination of the aforedescribed mud saver valve assembly and the
kelly (and kelly sub) constitutes the heart of the present
invention since the purpose of the valve is to prevent loss of mud
from the kelly when additional joints of drill pipe are to be added
therebelow.
The kelly is connected at its upper end to a swivel 116 which
includes a lower part 120 adapted to connect to and rotate with the
kelly and an upper part 121 rotatably connected to the lower part
and adapted to remain stationary while the lower part rotates. The
upper part 121 is connected to hose 122. The swivel provides means
to transmit drilling fluid from the hose to the kelly while
allowing relative rotary motion therebetween.
The swivel 116 is provided with a bail 125 whereby it is suspended
on hook 126 carried by travelling block 127. The travelling block
is suspended by cable 128 from the conventional crown block (not
shown) at the upper end of derrick 130. By this means the kelly and
mud saver valve assembly can be raised and lowered relative to the
earth's surface.
An earth bore 130 is provided with casing 131 and a casing head
132. Above the casing head is mounted blowout preventer 133. On top
of the preventer is disposed rotary table 134 adapted to receive a
master bushing 135.
As shown, a set of slips 136 is received in the master bushing
whereby is suspended a drill string including drill pipes 137, 138,
139. However when it is desired to rotate the drill pipe the kelly
is lowered and pin 14 (see also FIG. 3) of the mud saver valve
assembly is stabbed and screwed into the box 140 at the upper end
of the drill string. The slips are then removed and the string
lowered until kelly bushing 150 disposed around the kelly and held
up by kelly saver sub 114 is received in the square recess 151 in
the top of the master bushing. Thereupon the rotary table can
rotate the drill string through the master bushing and kelly
bushing and drilling can proceed.
During drilling motor 160 drives mud pump 161 to withdraw mud from
pit 162 through pipe 163 and pump it through it and pipe 164 to
hose 122. The mud then goes through the swivel and down the kelly,
the kelly, saver sub, and the mud saver valve assembly into the
drill string. Mud returns from the bottom of the earth bore through
annulus 167 and thence out through side port 168 in the casing
head; the mud passes through wing valve 170 and pipe 171 back to
the mud pit.
When drilling has progressed to the point where the kelly has moved
down to the point where the pin is right on top of the kelly
bushing, it is necessary to add another joint, i.e., piece of drill
pipe. The drill string is lifted with the derrick until the kelly
bushing is out of the master bushing and slips are inserted to
suspend the drill string as shown. The motor 160 is stopped,
thereby shutting down pump 161. At this time the pressure in the
drill string, as indicated by gage 180, should drop to
substantially zero. If it does not, bleeder valve 181 is opened to
bleed off the residual pressure. It will be recalled that at this
time ball check valve 50 will communicate drill string pressure
upwardly through the mud saver valve assembly into the kelly and
thence through the hose 122 to stand pipe 164 and gage 180.
Assuming that the pressure has been reduced to zero, the mud saver
valve assembly is unscrewed from the box 140 of the upper joint of
pipe 137. The ball check valve 50 closes; the spring 92 keeps the
poppet valve closed; no mud leaks out of the kelly. This is the
condition shown in FIG. 5.
The lower end of the kelly is then pushed over to one side to align
the mud saver valve assembly pin 14 with the box 190 of the joint
of pipe 191 disposed in the mouse hole, a hole drilled close to the
main bore 130 and slightly inclined relative thereto. The pin 14 is
stabbed and screwed into box 190, the joint 191 is lifted out of
the mouse hole, and pin 192 on the joint 191 is stabbed and screwed
into box 140. The pump motor 160 is then restarted restoring
circulation, and the newly added joint 191 and its connections are
checked for leaks. If there are no leaks, the joint 191 is lowered
into the hole and kelly 111 is lowered until kelly bushing 150 is
again in recess 151. Drilling can then resume.
If there should be difficulty in lowering the drill string pressure
after shutting down the pump, it may be desirable to reverse
circulate the mud. Since there is pressure in the kelly
communicated thereto by the ball check valve, the poppet valve will
also be open so that mud can flow upwardly through the mud saver
valve assembly. The cup-skirt chamber below the poppet largely
shields the poppet against the dynamic force of the upwardly
flowing mud.
To reverse circulate, the blowout prevention is closed, the pump
outlet 195 and return line valve 196 are closed, and by pass valve
197 and bleeder valve 181 are opened. After the pressure has been
brought under control the joint 191 can be added as previously
described, circulation returned to its normal direction, and
drilling resumed.
Although it has been pointed out that the drilling fluid saver
assembly of the present invention is such as to allow reverse
circulation should that be desirable, the assembly of course is
intended for normal circulation during drilling and such normal
direction of circulation can be employed in adding heavy mud to
reduce drill string pressure. It is only desired to distinguish the
present valve assembly from an ordinary upwardly closing check
valve which would prevent reverse circulation.
While a preferred embodiment of the invention has been shown and
described, modification thereof can be made by one skilled in the
art without departing from the spirit of the invention.
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