Note: Descriptions are shown in the official language in which they were submitted.
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"DOWN HOLE BLOW OUT PREVENTER AND METHOD OF USE"
The invention relates to a down-hole blow-out
preventer for use in drilling oil and gas wells and
weils that may be drilled for recovery of geothermal
energy, etc.
Surface blow-out preventers are in common
use in the oil industry but so far no blow-out preventer
is in commercial use which can be used successfully
to block off the oil well down the drill hole and
close to the drill bit.
Various proposals have been made for closing
the drill hole but none has ever been used successfully
commercially for various reasons.
For example U.S. Specification No. 3908769
shows a drill hole packer -to be carried by a drill
string but this packer is dependant for its operation
upon a high flow rate of fluid in the reverse direction
on encountering a kick. The device according to the
invention works on detection of a static pressure
difference.
, I, . - :
~L2~
U. S. Specifications Nos. 3941190 and
3503445 both show down hole packers but both packers
are operated by tools which have to be pumped down
the hole which would take several hours.
The invention provides a down hole blow
ou* preventer comprising an elongated tubular housing
having a through bore for the passage of drilling mud
and means for connecting the ends of the housing
into a drilling string, a packer element arranged
circumferentially around the housing and inflatable
into engagement with the bore hole to seal the hole,
passage means extending through the housing wall for
connecting the bore of the housing with the packer
element to inflate the element by mud pressure from
within the housing, a cylindrical valve sleeve mounted
inside the housing for movement between a drilling
position when the sleeYe closes said passage means and
an inflating position when the passage means is open,
a one-way valve for closing the housing bore on the
side of the sleeve to be nearer the drill bit, said
valve means being operable to allow the passage of mud
under pump pressure, but not allowing reverse flow
of mud, said valve sleeve providing a through bore
for the passage of mud, second valve means for closing
the bore in the valYe sleeve and means to close said
second valve means automatically when pressure in the
housing is reduced to a level below the pressure in
the bore hole by a predetermined amount, the arrangement
being such that after closing of the second valve means
the pressure in the housing can be re-applied to urge
the valve sleeve to its inflating position allowing
the packer element to be inflated, means to prevent
closure of the second valve means during running-in,
a mud circulation channel extending through the housing
on the side of the sleeve valve nearer the surface,
means being provided to open said channel when the
paclcer element is inflated whereby mud may be circulated
through the drill string, the channel and the bore hole
to increase the mud density, and means for deflating
the packer element only when the mud density is
sufficient to balance the pressure below the packer
element.
The invention is also concerned with a method
of using such a device.
A specific embodiment of a down hole blow out
preventer (D.~. BOP) in accordance with the invention will
now be described in detail with reference to the
drawings in which:.-
Figure l shows the D.H. BOP connected in a
drill pipe-string run into a hole;
~21.~r~f~ 1l
Figure 2 is a vertical sectional view of
the P.H.BOP in the running-in position;
Figure 3 is a horizontal cross-section along
line III-III in Figure 2;
5Figure 4 is a horizontal cross-section along
line IV-I~ in Figure 2~
Figure 5 is a horizontal cross-section along
line.V-~:in Figure 2;
Figure 6 shows a.vertical cross-sectional
10......................... yiew of the D.H.BOP, in drilling position;
Figure 7 is a horizontal cross-section along
lin.e VII-~II in Figure 6,.
Figure 8 shows a vertical cross-sectional
vie of the D.H.BOP during a wellkick after closing
the flapper valye.
Figure 9 shows cortical cross~sectional
tow of the D.H.BOP, with the packer inflated'
Figure 10 shows.a.~ertical cross-sectional
view of the D.H.BQP, with the circuIating port open.;
20Figure 11 is a horizontal cross-section along
line XI-XI in Figure 10;
Figure 12 is a horizontal cross-section along
line XII-XII in Figure 10,
Figure:13 shows a vertical cross-section.al
view of the D.H.BOP, deflating the packer' and
Al 2~ 4
- s -
Figure 14 shows a horizontal cross-section
on the line XIV-XIV in Figure 13.
As can be seen from Figure 2 the D.H.BOP
comprises two barrels an outer barrel 1 and an inner
barrel 2.
The inside of the outer barrel 1 and the outside
of the inner barrel 2 are fine machined to the required
tolerances.
The various channels and holes are milled and
drillèd in the inner barrel 2 and after being machined
the two barrels are shrunk together by undercooling
of the inner barrei 2.
The position of the two barrels in relation
to each other must be precise.
After shrinking the two barrels 1 and 2
together, the various ra.dial holes can be drilled and
the channels for the fill-up.valve assembly 41, the
grease bolt 1', the check.val~e 53, the circulating
vale 57 and the equalising valve 62 can be drilled
and machined.
The top of the outer barrel 1 is provided
with an external thread 4 for connection with an API
threaded substitute 3 to enable the insertion of the
inner parts of the D.H.BOP from the top.
The outer barrel 1, is provided at its lower
. .. .. .. .. .... .... . . .. .
9L2
end with an internal thread 4' to connect it with a
packersleeve 5.
The packersleeve 5 is at its bottom-end
provided with a threaded API box connection 6 to
connect it with the drilling bit.
Inside the packersleeve 5 a chamber is machined
which is nearly as long as the packersleeve 5, and in
which a floatvalve assembly 7 is inserted for sliding
movement from a lower to an elevated position.
Floatvalve assembly 7 comprises a piston-like substantially
hollow body 7' in which is mounted a conical valve 8
spring-loaded by spring 9 into sealing engagement with
a valve seat, formed inside body 7', Valve 8 is
fixed to valve stem iO which is guided for sliding up
and down movement in guiding sleeve 11 mounted in
bushing 12 which is fixed inside body 7 by means of a
spider.
A snapring sleeve 13 is insexted into the
top of packersleeye 5. The top of packersleeve 5 is
provided with four pressure equalising channels 15 in
the snapring sleeve 13.
Around snapring sleeve 13 a helical spring 16
is inserted before a snapring 17 is pressed over the
snapring sleeve 13. . -
A flappervalve sleeve 18 is pressed o'er the
s
-7-
snapring 17 mounted around snapring sleeve 13 until
it sits in a snapring recess 19.
Flapper~alve sleeve 18 is proyided with a
friction cam 20 which can be forced over the snapring 17
until snapring 17 snaps into snapring s]ot 21 of
flapperyalve sleeve 18, by pump pressure when the
flappervalve 22 is closed. The flappervalve 22 is
pi~otally mounted on top of flapperyalve sleeve 18 and
spring biased towards a closed position in which it is
in sealing engagement with the top edge 18' of flappervalve
sleeve 18. Closing movement is prevented by a
flapperval~e release sleeve 23 during circulating and
drilling.
The flappervalve release sleeve 23 comprises a
plunger holder 24 to which are fixed two plungers 25
which are received into bores formed in a plunger
housing 26.
The plunger holder 24 and the plunger housing
26 are provided with four pressure equalising channels
27 and 28 respectively.
A helical spring 29 bears with its cover end
against the top of the plunger holder 24 with its upper
end against a retainer ring 30 by which the tension
of spring 29 can be adjusted. The retainer ring 30
is also provided with four pressure equalising channels
31~ A steel arresting ball biassed in~axdly by a
calibrated helical spring rests in a circumferential groove
in plunger holder 24.
--8--
By stopring 32 upward movement of the plunger
holder 24 is limited to keep he plungers 25 inside
the plunger housing 26.
Against the top of retainer ring 30 bears a
helical spring 33 which bears with its other end
against a shut-off sleeve 34 to keep the sleeve 34 in
its highest position in which a channel 35 and a fill-up
channel 36 are open see Figure 3).
The fill-up valve assembly 41 is shown in
lO running-in position in Figures2 and 3 and in circulating
or drilling position in Figures 6 and 7. It comprises
a gate 41' having a substantially rectangular cross-
section and running in a hole 42 which hole is closed
at one end by locking nut 45 having a slotted part 46
in communication with a bore 35 in the body part 2. A
screen 47 covers a recess, formed in outer barrel l
which is in communication with fill-up channel 36, and
an inlet 48 which opens into flappervalve release channel
49. Channel 49 extends through inner barrel 2 and
20 opens into circumferential groove 50 formed in plunger
housing 26 and ports 51 extend from g.roove 50 into the
plunger cylinders.
The first purpose of the fill-up valve assembly
41 is to be in open position (Figure 3) to fill up the
25 drill pipe when running thedrill pipe into the hole and
simultaneously to close off the flappervalve release :!
;
.,,
channel 49 when running into the hole so that no pressure
difference between the annulus and drillpipe can lift
the plungers 25 and accidentally cause the flappervalve
22 to close.
Its second purpose is to close off the fill-
up channel 36 once circulation or drilling has commenced.
The greater pressure inside the drill pipe is propagated
through channel 35 to gate 41 and moves the gate 41 to
close the fill-up channel 36, against the lesser pressure
in the annulus as shown in Figure 7. When the gate 41
moves it also closes the fill up channel 36 and mud will
fill the fluid lock 52.
The shut-off sleeve 34 is moyed downardly when
circulation is started and to increase the pressure drop
an aluminium disc 37' with an orifice may be provided
- by means of threaded ring 37 which disc will be
disintegrated during circulation. The position is
shown in Figure 6.
When the shut-off sleeve 34 moves downwardly
against the tension of spring 33, the locking spring
snaps into the locking groove 39 formed in the inner
wall of inner barrel 2 and shuts off the channels 35
and 36. The shut-off sleeve 34 is provided with three
pressure equalising channels 40.
After the shut-off sleeve 34 has mowed
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I] o -
downwardly to close channel 35 the entrapped mud
in the fluid lock 52 will cause khe fill-up channel
36 to be permanently closed while the flappervalve
release channel 49 remains open. The plungers 25
are from now on permanently connected to and subjected
to the pressure in the annulus through inlet 48 and
channel 49.
Another purpose of the fill-up valve
assembly is to provide the possibility to calibrate the
tension of the spring loaded steel ball 23' (Figure 2)
and the spiral spring 29 before running the D.H.BOP into
the hole. The spring loaded steel ball 23' is there
to prevent fluttering of the flapper.valve release
sleeve 23 by pressures lower than the setting of the
spring 29 for releasing the flapper ale 22.
To enable calibration of the spring loaded
steel ball ~3' and the spiral opening 29 the fill-up
valve gate 41 is set in the drilling position as shown
in Figure 7 whereafter a grease pump with a pressure
gauge is connected to the threaded inlet 48 leading to
flapper.val~e release channel 49. The ten.sion set
for the spiral spring 29 depends on the maximum expected
penetration rate per hour, the hole size, the depth
of the hole, the pump volume and the cross sectional
area of the plungers 25.
Easy to read chaxts can be developed for this
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purpose.
The required spriny tension is the tension
required to overbalance the greater hydrostatic head
of the mud column in the annulus caused by the presence
of drilled formation cuttings when the pump is stopped.
A checkvalve 53 is provieed to allow mud to enter and
to inflate the inflatable packer element 54 when the
flappervalve 22 has been released and closed, and
the flapperval~e sleeve 18 has been pumped down to
uncover the inflating port 55. This operation will
be described later. Mud can then be pumped through
port 55 and channel 56 into packer element 54. The
check valve 53 closes and retains the mud in the
inflatable packer element 54 when the pressure in the
drillpipe drops.
It will be seen that the outside diameter
of the outer barrel 1 has a partly enlarged diameter la,
which is proyided with spiral grooves 16 figure 4)
like an undersized solid body stabilizer.
The enlarged diameter provides protection for
the packer element 54. Furthermore a steel ring 54'
at the bottom end of the packer element 54 is connected
to the packer sleeve 5 by means of shearpins 54''.
This to protect the packer element whilst running into
the hole and to withstand rotational forces when drilling.
--`` 3L2~ Z
-12-
The shearpins 5~'' are sheared when the packer 54
is inflated say at a pressure of 700 psi.
A shut-off valve assembly 57 is provided
which is composed of a shut-off piston 57' with O-ring
seals, a helical pressure spring 58 and a bushing
59 with a thread 59' for a grease nipple.
When running in and drilling (Figure 5),
the shut-off piston 57' is isolated from the pressure
inside the tool by the flappervalve sleeve 18 with
which is provided O-ring seals (Figure 2). It
is exposed to the pressure inside the tool when in
inflating the packer element 54 the flappervalve
sleeve 18 is pushed downardly and its friction cam 20
rides over the snapring 17 which then snaps into the
slot 21 as will be described later.
The object of the shut-of-f piston 57' is to
close the channel 60 while pump pressure is present
within the tool, and to open the channel 60 when the
pump is stopped. This is achieved by the pressure
within the tool moving the piston 57l against the
spring 58 to close the channel 60 from the annulus.
An equalising valve 62 is provided (Figure 5)
which comprises an equalising piston 62, hazing a
conical nose, a helical pressure spring 63 and a
threaded bushing 64 in which bolt 65 is screwed.
-13
The purpose of the equalising valve is to
open the packer element to the channel 60 when the
pressure in the annulus below the packer (which is fed
to the valve via channel 66) is exceeded by 300 psi
by the mud pressure which is above the packer. The
mud pressure is present in channel 60 when piston 57'
opens the channel 60 to the annulu.s~
When a kick i.s encountered and the packer
element 54 has been inflated (Figure lO) then during
circulation through the circulating channels 61 the
equalising channel 60 is closed and no extra circulation
pressure is behind the equalising piston 62. However
when the pump is stopped and the shut-off pistion 57'
is pushed back by spring 58 then. the equalising channel
60 is open to the mud pressure in the annulus so that
the hydrostatic pressure acts on the conical nose of
the equalising piston 62.
on the opposite side of the equalising piston 62 the
formation pressure below the packer is received via
equalising port 64 and aligned ports 67 and 68 formed
in flappervalve sleeve 18 and snapring sleeve 13
respectively.
If now the mud weight is sufficiently increased
to overbalance the formation porepressure and the pump
is stopped then the hydrostatic head of the mud column
3l21;~
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in the annulus above the packer exerts pressure
against the equalising piston 62 and moves this piston
until it opens the deflating channel 69 so that the
pressure inside the packer element escapes into the
annulus through equalising channel 60 assisting the
equalising piston 62 to remain in open position
(Figure 4).
The overpressure required to move and open
the equalising piston 62 can be adiusted by means of
the spring loaded ball 84 resting in groove 92 and can
be tested with a grease pump having a pressure gauge
when the grease nipple i5 screwed into the thread 57.
When the flappervalve sleeve 18 is pumped down
after the packer element has been inflated, the mud
below the flappervalve is trapped and, although of
very small volume, the closed floatvalve 7 will move
downwardly and compress the gas or liquid or squeeze
it back into the formation against the formation pore
pressure.
After the ~H.BOP is prepared fox running in,
the D.~l.BOP can be run into the hole, so that it reaches
eventually the position as shown in Figure 1. In
Figure 1 is shown the D.H.BOP 70, interconnected between
the drillpipe-string 71 and drillbit 72 and run into
25 hole 73 so that annulus 74 i5 formed. A casing 75 is
-~15-
cemented in the upper portion 73' of the hole 73,
while at the surface a surface blow out preventer 76
of known type is provided below rotary table 77. Mud
can be pumped by pump 78 t'nrough hose 79 and swivel 80
down into drillpipe-string 71, which mud then is
ejected from drillbit 72 and flows upwardly through
annulus 74. With reference numeral 81 a pressure gauge
is shown.
When running in, the drillpipe is empty and
the floatvalve 7 is closed and in its highest position
(see Figure 2) so that no mud can enter the drillpipe
through the bit nozzles and no formation cuttings can
settle down inside the bit on top of the bit nozzles
causing the bit to become plugged when circulation is
started. The filling of the drillpipe takes place
through the fill-up opening 36 and hole 42 of the
fill-up gate 41.
The mud is screened by the mudscreen 47.
Figures 1 and 3 give a clear insight on the operation
and position of each valve and part when running into
the hole.
Attention should be given to the fact that
when for one reason or the other circulation has been
established during running into the hole, it will be
necessary that the drillpipe will be filled from the
... , . .~............... .. ..
-16-
top of every stand to be run into the hole because
after circulation the fill-up valve will be permanently
closed as described herein aboveO
When the bit has reached the bottom of the
hole the mudpumps are started and circulation is established
through the floatvalve 7 and the bit nozzles. Figure 6
gives a clear insight on the operation and position of
each valve and part when circulating or drilling.
Drilling may continue without encountering a kick and
a roundtrip to change the bit is then made without
having used the D.H.BOP.
When the bit is pulled and unscrewed, the
floatvalve 7, the valve seat inside body 7' and the
valve assembly circumferential body seals should be
inspected and be in a good condition or changed for
new ones before maklng-up a new bit.
ext, take out the threaded ring 37 from
shut-off sleeve 34 with a set and pulling tool, and
screw a set and pulling tool into the same thread and
pull the shut-off sleeve 34 up until its highest
position unscrew tool and screw in threaded ring 37
again.
The fill-up valve gate 41 has to be cleaned
and to be xeset after each roundtrip. Unscrew locking
nut 45, put grease nipple in the thread, pump out the
, . - . . . . ., . ......... . . . .y .
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-17-
housing 44 for gate piston ~3 together with the gate 41,
clean and reinsert gate 41 and housing 44, use grease,
set gate 41 in fill-up position with a set bolt "s"
and screw in locking nut 45, take out set bolt and
tighten locking nut ~5. The D.H.BOP can be run again
and is ready to operate again when necessary.
Figure 8 gives a clear insight of the operation
and the position of each valve and part when a kick is
encountered and the annulus is closed in by the surface
BOP 76.
If a kick is encountered during drilling then the
pumps are stopped, the standard pipe valve closed, the kelly
picked-up and the annular BOP closedr The closed~in
drill pipe pressure is then read and recorded. As soon as
the pumps are stopped the floatvalve 7 will close due to
the tension of spring 9.
As the well is completely closed-in, now
pressure will be built up inside the well.
The floatvalve assembly-7 was in its lowest
position when circulating. Now the pumps 78 (Figure 1)
are stopped so that the closed floatvalve assembly 7
acts like a floating piston and when pressure below
it is building up it can move upwardly making it possible
to read the closed in drillpipe pressure (C.I.D.P.P.)
from the pressure gauge 81 (Figure 1).
-18-
The C.I.D.P.P. + hydrostatic head of the mud
column in the drillpipe = formation pore pressure.
If the kick is observed at an early stage
then the time required for the C.I.D.P.P. to build up
should be about ten (10] minutes, depending on the
column of gas already produced in the annulus 74
(compression).
The C.I.D.P.P. is recored and the required
mud weight calculated with sufficient overbalance over
the formation pore pressure.
Now the C~I~D~PoP~ is slowly bled-off at the
drillpipe. Wait a few seconds and start pump 78 slowly.
In the meantime the following occurs downhole:
When the well is closed in, the C.I.D.P.P. + hydrostatic
head of the mud column in the drillpipe = closed in
annular pressure t hydrostatic head of mud column in
the annulus because these are co}~municating vessels with
the floating floatvalv0 assembly 7 between them.
Say that the C.I.D.P.P. is 300 psi. and
the pressure is bled-off at the drillpipe, now the
annular pressure at the bottom of the hole is 300 psi.
higher than in the drillpipe. The floatvalve assembly 7
moves into its highest position and the pressure in the
annulus 74 is propagated via the inlet 48 and through
hole 42 in fill-up valve gate 41 through the flappervalve
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--19--
release channel 49 underneath the plungers 25, which
are then moved upwardly lifting the flappervalve release
sleeve 23 until the spring biased flappervalve 22 falls
on the seat 18' formed by the upper edge of flappervalve
sleeve 18, which is then closed off (see Figure 8).
All above occurs when the C.I.D.P.P. is bled-off at the
drillpipe.
Now the pump 78 is started very slowly.
Pressure builds up to abt. 1500 pse. and drops. Pump
speed is increased to 100-200 gln/min. depending on the
size of the D.H.BOP and the size of the circulating
channels 59.
As shown in Figure 9 downhole the following
occurs:
The flappervalve 22 is already closed. Pump 78 runs
slowly. The flappervalve sleeve 18 is pushed downwardly
by the pump pressure against the helical spring until
the inlet 55 of the check valve 53 is uncovered and the
1appervalve sleeve 18 hits the snapring 17 with the
calibrated friction cam 20~ Pressure is now building
up and the packer element 5~ is inflated through
inflation channel 56.
At about 1500 psi. the flappervalve sleeve 18
snaps With its friction cam 20 over the snapring 17 which
is locked in the snapring slot 21 and the packer 52 is set.
-.20-
As shown in Figure 10 when the snapring 17 is
snapped into the snapring slot 21 the mud pushes shut-
ofE piston 57' (Figure 8, 52) outwardly so that piston
57 closes channel 60.
In this position of the sleeve 18 mud can
be circulated through the circulation ports 61. When
circulation is established the drillstring is lowered to
put some weight on the packer to make certain that the
packer 54 is set.
. The packer 54 is now isolating the producin.
zone from the remaining portion of the hole.
The tool is closed-off at the bottom by the
float.valve assembly 7 and from the top by the flappervalve
22.
When the mudweight has been increased by
circulation to the required weight so that the
hydrostatic pressure of the mud column above the
packer 54 is overbalancing the pore pressure of the
formation below the packer the pump should be stopped.
The chann.el 60 will then be opened by the pistion 57' and
the equalising valve so that the packer is deflated
and the string can be pulled out of the hole.
As shown in Figure 13 the following occurs
downhole when the mud is overbalancing the formation
pore pressure and the pump is stopped.
~Z~ }4~
-21-
When the pump is stopped the shut-off piston
57 ovens the equalisin~ channel 60.
The hydrostatic pressure of the mud column
above the packer 54 acts on the one side of the equalising
piston 62 which normally shuts off deflating channel 69.
The other side of the equalising piston 62
is connected through channel 66 and pOrtS 67, 68 with
the space between the flapperva.lve 22 and the float
10 .~alve a.ssembly 7, below which the formation pore
pressure acts.
If no the hydrostatic pressure ox the mud
column in the annulus above the packer.54 overbalances
sufficiently the formation pore pressure below the packer
then the equalising piston 62 moves and opens the
deflating channel 69. The pressure of abt. 1500 psi.
behind the packer element 54 i9 now released in the
annulus through channels 69 and.60.and the packer elements
deflates and the packer is free.
If the packer does not deflate then the recorded
C.I.p.P.P. was not correct and the mudweight should be
increased gradually and the pumps stopped at intervals.
When a well starts comin.g in during roundtripping
the same procedure should be followed as during drilling
but instead of pulling out continuously one should kill
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~22-
the well, unseat the packex and run back to bottom
decreasing the mudweight when going deepex and
cirCulating at 2ntervals.
Circulating takes then place through the
circulating ports instead of through the bit nozzles.
When the bottom of the Cole is reached,
condition the mud and pull-out to inspect all parts of
the D.H.BOP.
An alternative use of the D.H.BOP i5 when
drilling on the sea bed with a surface BOP positioned
on the sea bed and it is desired to suspend drilling
operations e.g. when weather us bad.
The surface BOP is first closed and the mud
pressure within the string is bled down. Mud undar
pressure is then forced into the annulus whereby the
pressure in the annulus exceeds the pressure setting
of the arresting ball and helical spring in the tool
by at least the amount necessary to operate the D.H.BOP
to close the flapper valve. The packer element can
then be inflated as before and this will seal the bottom
end of the caslng and the drill string and the surface
pipe from the sea bed to the drilling vessel can be
removed.
Reconnecting the surface pipe and the drill
pipe and releasing the packer can be achieved by closing
-23-
the drill pipe at the surface and pressurising the
annulus, below the clvsed BOP rays a thç surface, to
open the eq~lising valve, whereafter the rams are
opened.
An advantage of the DHP~P described is that
in addition to controlling a well in a novei manner,
a well can be hrought under control in the conventional
manner. Ion this case on detecting a kick the surface BOP
is closed and the closed in drill pipe pressure is
read. Instead of lowering the closed in pressure
to close the flapper valve, the closed in pressure is
maintained. The flapper valve does not close and
the well can be brought under control in the normal
way by the introduction of heavier mud.
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