Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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VALVE ASSEMBLY FOR THE REMOTE CONTROL OF FLUID FLOW HAVING
AN AUTOMATIC TIME DELAY __
BACKGROUND OF THE INVENTION
This invention relates to new and useful improve-
ments in the remote control of fluid flow utilizing a valve
incorporating an automatic time delay.
In certain industrial applications, it is benefi-
cial to have control over a distant fluid flow in such a way
that some predictable delay is incorporated automatically
between the actuating means and the function being controlled.
Although the present description and drawings rela-
te to oil well drilling, nevertheless the device can be used
in other industrial applications.
In the drilling of petroleum exploratory wells, it
i5 desirable to control and therefore prohibit, the passage
of natural gas from the downhole drilling bit location to the
earth's surface through the borehole annulus and also through
the hollow drill stem itself.
Such ccmtrol is mandatory for the prevention of
costly "blowouts" that may occur in the process of drilling
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wells for the recovery of petroleum products.
Conventionally, control of gas flow through the
bore-hole annulus is by means of "blowout preventers" in-
stalled at the surface and some control is exercised over
the passage of gas through the interior of the drill stem
by means of a downhole "float valve" and the present inven-
tion relates primarily to improvements in downhole "float
valve" assemblies.
The present downhole float valve assemblies often
! 10 cause what is known as "hydraulic sticking" of the drill
string. As the drill string is lowered into the borehole
subsequen~ to bit changing or the like, the lower members
of the drill string (the drill collars) often become coated ~;
with various matter (e.g. cuttings and/or mudcake) suspended
in the drilling fluid and when the interior of the drill
string is subjected to the drilling fluid pressure imposed by
the surface pumps, the drilling fluid itself causes the down-
hole float valve to open thereby permitting the passage of
drilling fluid down through the drill bit and into the bore-
hole annulus where it normally would proceed back to the sur-
face.
However, the material in suspension in the annulus
fluid sometimes becomes compressed upwardly as a result of
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the surface pump pressure thus causing a complete or par-
tial blocking of the annulus route intended for the return
of the drilling fluid to the surface.
The continuing application of pressure by the sur-
face pumps therefore causes a downhole force imbalance in
such a direction as to cause the float valve to close there-
by leaving a section of the downhole annulus, pressurized,
resulting in a hydraulically "stuck" situation.
In float valve applications, the present state of
! 10 the art requires that some unlocking means by applied from
the surface in order to break this hydraulic lock. Conven-
tionally, a ball or dart or the like is dropped down the
interior of the drill stem from the surface in order to at-
tempt to open the valve, but this practice is generally un-
lS predictable and unsatisfactory~
SUMMARY OF THE INVENTION
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The main purpose of the apparatus disclosed herein
is to permit the balancing of the aforementioned downhole
pressures by means of a float valve that incorporates an
automatic time delay feature, such that bac~ pressure may
be relieved up through the drill string while the valve
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remains in an open condition for a predetermined length of
time.
There is disclosed herein a time delayed float
that may be installed at the lower end of a typical drill
string and having the following features:
(a) The valve is normally closed or partially closed, and
is influenced in this condition by means of a helical
spring.
(b) The application, in the downstream direction, of nor-
mal pressure exerted by surface pumps for the purpose
of circulating drilling fluid down through the inte-
rior of the drill stem, through the drill bit, and
back to the surface through the bore hole annulus,
will cause the present valve to open relatively quick-
ly, permitting the unimpeded flow of drilling fluid.
(c) The removal of the pressure exerted by the surface
pumps, creating at the bit a pressure differential
in the reverse direction to that associated with nor~
mal drilling fluid circulation, will cause the present
valve to close gradually (typically over a four minute
period), thereby permitting th0 pressure to equalize
between the annulus and the drill string interior at
the bit.
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(d) The contained helical spring or other source of axial
pressure shall keep the valve in the closed condition
- until adequate downstream pressure is once more applied.
(e) Additional pressure that may be encountered in, for
example, a downhole gas-bearing formation, will act
in an upstream direction such that addi~ional force is
applied to keep the present valve in the closed posi-
tion - preventing venting of such gas to the surface
through the drill string.
(f) The partially closed valve will also prevent the flow
of relatively large chips or other solids into the
drill stem while the bit is being run to the bottom
of the hole. This will reduce the possibility of sub-
sequent plugging of the bit nozzles by matter suspended
in the drilling fluid.
One aspect of the invention consists of a float
valve assembly for the remote control of the fluid flow com-
prising in combination a cylindrical casing, a fluid passage-
way extending axially through said casing and a valve assem-
bly within said passageway dividing said passageway into one
portion above said valve assembly and another portion below
said valve assembly, said valve assembly including a valve
seat in said passageway, a valve normally engaging said valve
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seat and sealing of said passageway, means normally main-
taining said valve upon said seat until a predetermined
pressure of fluid through said passageway from said one
portion thereof, moves said valve from said seat against
the pressure of said means, means to control the movement
of said valve from said seat and time delay means to con-
trol the movement of said valve onto said seat when back
pressure of fluid from said other portion of said passageway
below said valve is greater than the pressure of fluid with-
in said one portion of said passageway above said valve seat.
With the foregoing in view, and other advantages
as will become apparent to those skilled in the art to which
this invention relates as this specification proceeds, the
invention is hereby described by reference to the accompany-
- 15 ing drawings forming a part hereof, which includes a descrip-
tion of the preferred typical embodiment of the principles of
the present invention, in which:-
DESCRIPTION OF THE DRAWINGS
Figure 1 is a cross sectional partially schematic
view of the invention shown at the bottom of a bore hole.
Figure 2 is a partial longitudinal section and
partially broken away view of the invention incorporated
within a cylindrical casing.
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Figure 3 is an end view of Figure 2 taken from
the right-hand end thereof.
Figure 4 is an end view of Figure 2 taken from
the left-hand end thereof.
Figure 5 is an enlarged cross-sectioned view of
the valve assembly per se.
In the drawings like characters of reference in-
dicate corresponding parts in the different figures.
DETAILED DESCRIPTION
Proceedinq to describe the invention in detail,
reference should first be made to Figure 1 in which the in-
vention collectively designated 10 is situated immediately
above a drill bit 11 to which it is attached. The drill
string 12 is secured to the other end of the invention sub
10 and extends to the surface (not illustrated).
Within the bore hole 13, an annulus 14 is ~ormed
around the invention sub and drill string and it is normal
for drilling fluid to pass downwardly through the drill string,
through the drill bit 11 and then upwardly through the annu-
lus as shown by arrows 15.
As will be seen from the legend attached to Figure
1, back pressure sometimes builds up within the annulus as
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the passageway is blocked by mudcake or other suspended
solids illustrated by reference character 16 thus causing,
in conjunction with the float valve assembly 17, an hydrau-
lic lock or an hydraulically "stuck" region between the
float valve assembly and the blocking matter.
Reference should next be made to Figure 2 in which
the invention collectively designated 10 comprises a sub-
stantially cylindrical casing 18 taking the form of a top
sub 19 threadably engageable with a bottom sub 20 by means
of a modified tool joint 21.
!
A conventional tool joint 22 at one end of the top
sub 19 permits the top sub to be connected to a lower end
of the drill string in the usual manner and a similar tool
joint 22A at one end of the bottom sub, enables the bit 15
to be secured thereto in the usual way.
Situated within the cylindrical casing 18 is the
aforementioned float valve assembly collectively designated
17.
An axial passageway 23 extends through the subs 19
and 20 with the float valve assembly 17 being situated with-
in the passageway.
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A conical valve seat 24 is provided at the lower
end of the passageway 23 extending through the top sub 19
and a conical valve 25 normally engages within this valve
seat 24 thus partially or completely closing off the passa-
geway 23 unless sufficient pressure of fluid through passa-
geway 23, is provided in order to lift the valve 25 from
seat 24 as will hereinafter be described.
Situated within the bottom sub 20, is a cylindrical
housing 26 held axially within the passageway 27 in the bot-
tom sub, by means of top and bottom spiders 28 or the like
and this cylindrical housing includes an upper closed end 29
and a lower closed end 30. The upper closed end is in the
form of a cap screw threadably engaging the main cylindrical
- portion 31 and the lower closed end 30 slidably engages over
a shoulder formed on the lower end of the housing 31 and is
held in position by means of set screws 32.
The valve head 25 includes a cylindrical valve stem
33 secured to the valve head 25 by means of set screws 34 ex-
tending through a flanged end 35 of the valve stem and this
cylindrical valve stem extends through the end caps 29 and 30
in a sliding relationship, seals 36 being provided to maintain
a sealed relationship between the reciprocal valve stem and
the interior of the cylindrical housing 31 which is filled
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with a fluid such as a silicone oil or the like (not illus-
trated).
Secured to the valve stem within the cylindrical
housing 31 is a dashpot type housing 37 including seals 38
thereby dividing the cylindrical housing or hydraulic cham-
ber into a first part 39 and a second part 40.
Reference to Figure 5 will show details of this
portion of the invention. A coiled helical compression
spring (for example) 41 extends around a portion of the val-
ve stem below housing 37 and reacts between the end 30 of
the hydraulic chamber and the housing thereby normally ur-
ging the housing together with the valve stem and valve, in
the direction of the valve seat 24 and thereby normally
maintaining the valve head 25 upon valve seat 24.
When sufficient pressure of drilling fluid from the
surface, is present in order to overcome the pressure of the
spring 41, the valve head together with the valve stem and
housing 37, moves downwardly towards the drill bit and this
movement is controlled by a passageway or bore hole 42
through the housing communicating between the first and se-
cond chambers 39 and 40. A one-way spring loaded check val-
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ve 43 is provided within the bore hole 42 and this moves
from its seat against pressure of the spring 44 thus allow-
ing the transfer of fluid as the first part 39 decreases in
volume and the second part 40 increases proportionally.
The diameter of the bore hole or passage 42 toge-
ther with the nature of the ball valve and spring assembly
43 is such that a relatively fast transfer of fluid from
the part 39 to the part 40 is permitted.
The valve remains in the open condition for as long
as adequate pressure is applied in the downstream direction
indicated by arrows 45.
However, upon removal of downstream pressure, the
typical helical spring 41 together with such upstream pres-
sure as may be present, acts in a direction to close the
valve 25 upon seat 24. It will be observed that under these
conditions the ball valve 43 ia c~osed so that the bore hole
or passage 42 is closed.
.
Various time delays are built into the design of the
device in order to control the time taken for the valve 25 to
close upon seat 24 and in this embodiment, a bleed passage or
jet valve assembly 46 is provided through the dashpot housing
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37. The bleed passage 47 extends through the housing from
the part 39 of the hydraulic chamber and an adjustable jet
valve 48 screw threadably engages an enlarged other end 49
of the bleed passage 50 that the flow of fluid through the
bleed passage is controlled within limits.
Typically, the valve 48 is adjusted so that a time
delay of approximately four minutes occurs between the start
of the closing valve 25 and the engagement thereof with the
seat 24.
It will also be noted that the arrangement of parts
of this assembly is such that the maintenance of the assembly
is improved and that adequate seals are provided with respect
to both the containment of the self-contained hydraulic fluid
within the hydraulic chamber and the flow of fluid being con-
trolled and automatically accommodating inadvertent changes,
e.g. thermal expansion, in the volume of the contained hydrau-
lic system. In this connection, a release valve (not illus-
trated) may be incorporated.
In operation, the time delay float valve is contained
in the lowermost section of the drill string with the drill bit
connected to the lower end thereof.
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As the drill string is lowered into the fluid
filled drill hole (for example, after a bit change), the
valve 25 remains partially closed therefore permitting
drilling fluid within the drill hole to enter the string
from the bottom end, but excluding the larger solid matter.
Once at the bottom of the drill hole, the enrgizing of the
surface "mud" pumps (not illustrated) forces drilling fluid
down into the interior of the drill string creating a pres-
sure that overcomes the helical spring pressure ~1 thereby
permitting valve 25 to move from seat 24 as hydraulic fluid
is transferred from the first part 39 to the second part 40
of the hydraulic chamber or housing 31. This is through
the action of the spring loaded ball valve assembly 43 and
the passageway 42 within the dashpot type housing 37.
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As long as drilling fluid is circulating down
through the drill string stem, through the bit and back to
the surface through the bore hole annulus 14 (see Figure 1),
the valve 25 remains in the open position. However, when
the pressure is discontinued by the surface pump, a pres-
sure differential will be created across the valve 25 so
that force will be applied by the helical spring 41, in a
direction to close the valve 25 upon the seat 24.
However, because the closing of the valve is con-
trolled and delayed by the movement of the hydraulic fluid
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from the second part 40 to the first part 39 through the
: bleed passage 47, there is a deliberate time delay intro-
duced into the valve closing operation.
This will permit the "bleeding" of the pressure
differential back to the surface through the interior of
the drill string, followed after the time delay, by a posi-
tive closing of the fluid flow path in the upstream direc-
tion by means of valve 25 engaging seat 24.
This time delay may, as hereinbefore described, be
-! 10 adjusted within limits, by means of the bleed screw 48.
It is preferable that the valve head 25 be formed
from tungsten carbide or the like and that the valve seat 24
be formed from a similar material. In this connection, the
valve seat 24 is preferably detachable and is inserted with-
in a cylindrical recess 50 and held in position by means of a
split ring 51 seated within an annular groove 52 with annular
seal 53 being provided around the seat and the wall of the
bottom sub 19 as clearly shown in Figure 5.
Mudcake and/or drilling cuttings or other matter
may be removed by bleeding back any pressure through a sur-
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face valve up the drill stem and then moving the drill
string up and down and/or rotating the string and regain-
ing circulation, thus allowing a return to drilling.
Since various modifications can be made in our
invention as hereinabove described, and many apparently
widely different embodiments of same made within the spirit
and scope of the claims without departing from such spirit
and scope, it is intended that all matter contained in the
accompanying specification shall be interpreted as illustra-
tive only and not in a limiting sense.
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