U.S. patent application number 11/825219 was filed with the patent office on 2008-01-10 for pump-down pressure plug.
This patent application is currently assigned to Grinaldi LTD. Invention is credited to Scott Anthony Benzie, Andrei Gregory Filippov.
Application Number | 20080006403 11/825219 |
Document ID | / |
Family ID | 38918142 |
Filed Date | 2008-01-10 |
United States Patent
Application |
20080006403 |
Kind Code |
A1 |
Benzie; Scott Anthony ; et
al. |
January 10, 2008 |
Pump-down pressure plug
Abstract
A pressure plug system comprising a pressure plug with a tapered
section, a receiving landing receptacle having a tapered section
with substantially the same tapering angle as tapered section of
the pressure plug, and tapering angle being less than the friction
angle corresponding to the coefficient of friction between the
pressure plug and the landing receptacle. The pressure plug engages
the receiving landing receptacle providing reliable seal and
locking the plug against landing receptacle preventing axial
movement under cycling pressure and rotation of the plug during
drillout.
Inventors: |
Benzie; Scott Anthony;
(Houston, TX) ; Filippov; Andrei Gregory;
(Houston, TX) |
Correspondence
Address: |
Dimitri Filippov
3532 West TC Jester Blvd.
Houston
TX
77018
US
|
Assignee: |
Grinaldi LTD
Houston
TX
|
Family ID: |
38918142 |
Appl. No.: |
11/825219 |
Filed: |
July 5, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60818875 |
Jul 6, 2006 |
|
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|
Current U.S.
Class: |
166/285 ;
166/120 |
Current CPC
Class: |
E21B 43/103 20130101;
E21B 33/16 20130101 |
Class at
Publication: |
166/285 ;
166/120 |
International
Class: |
E21B 33/12 20060101
E21B033/12; E21B 33/128 20060101 E21B033/128 |
Claims
1. A pressure plug system comprising: a pressure plug comprising a
first tapered section with a first tapering angle; a landing
receptacle comprising a second tapered section with a second
tapering angle substantially equal to the first tapering angle of
the first tapered section of the pressure plug; whereby the first
tapered section of the pressure plug is adapted to engage in the
second tapered section of the landing receptacle; and whereby the
first tapering angle of the pressure plug is less than a friction
angle corresponding to a coefficient of friction between the first
tapered section of the pressure plug and the second tapered section
of the landing receptacle.
2. The pressure plug system of claim 1, wherein the tapering angle
is in the range of substantially from 0.5 to 6 degrees.
3. The pressure plug system of claim 1, wherein the tapering angle
is in the range of substantially from 1 to 3 degrees.
4. The pressure plug system of claim 1, wherein the ratio of the
length to the diameter of the tapered section of the pressure plug
is substantially from 1 to 6.
5. The pressure plug system of claim 1, wherein the ratio of the
length to the diameter of the tapered section of the pressure plug
is substantially from 2 to 4.
6. The pressure plug system of claim 1 comprising a cylindrical
section of constant diameter, wherein the cylindrical section of
the pressure plug having at least one groove with elastomeric ring
adapted to sealingly engage in a cylindrical section of the landing
receptacle.
7. The pressure plug system of claim 1 comprising at least one
elastic cup extending outwardly and rearwardly.
8. A method of providing a pressure containment comprising:
providing a pressure plug system comprising a pressure plug with a
tapered section, a receiving landing receptacle having a tapered
section with substantially the same tapering angle as said tapered
section of the pressure plug, and said tapering angle being less
than the friction angle corresponding to the coefficient of
friction between the pressure plug and the landing receptacle;
pumping said pressure plug down through the drill pipe and landing
pressure plug in receiving landing receptacle; applying pressure
not less than maximum expected back pressure.
9. The method of providing a pressure containment of claim 8,
wherein said applied pressure is approximately twice higher that
the expected maximum back pressure.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a non-provisional of U.S. Application
Ser. No. 60/818,875 filed on Jul. 6, 2006, which is incorporated by
reference herein in its entirety.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
[0002] Not applicable.
BACKGROUND OF THE INVENTION
[0003] 1. Field of the Invention
[0004] This invention relates to tools for use in drilling of oil
and gas wells and more particularly to pump-down pressure plugs for
use in tubular expansion tools.
[0005] 2. Background of the Invention
[0006] Pressure plugs, such as pump-down plugs and wiper plugs, are
frequently used in operations in which there is a need for creating
pressure chambers or separation of fluids. For example, in a
conventional tubular expansion process, the expandable tubular
string is deployed in the well on a drill string with the bottom of
the remainder segment of the tubular string, usually referred as a
bottom shoe, being open allowing pumping cement slurry into the
wellbore annulus or circulation of drilling fluids. Commencement of
the expansion process requires the bottom shoe to be pressure
sealed to provide a pressure chamber between the shoe and the
expansion swage. This is usually done by pumping a pressure plug
through the drill pipe which lands in the landing receptacle of the
shoe. The pressure liquid is pumped in the chamber between the shoe
and the expansion swage which urges the swage to propagate through
the tubular and expand the tubular. During this process, the drill
pipe is attached to the swage and moves out of the well. At the end
of every stand of drill pipe, the pressure is released, the stand
is removed, and then pressure is reapplied. These cycles continue
until the entire tubular string is expanded.
[0007] A typical conventional pressure plug has several elastic
cups for wiping the drill pipe and/or for providing a pressure
differential for the plug to be pumped down. The front portion of
the plug includes a so called nose section having a forward end and
back end. The nose section is tapered to provide a stop shoulder. A
pair of annular grooves is provided for seal rings. The back end of
the nose has a recess in which is disposed a latch ring. In
operation, the pressure plug is pumped down through the drill pipe
until it is latched in a landing receptacle in the shoe in which
the forward motion of the plug is limited by the stop shoulder and
the rearward displacement is limited by the latch ring. The
conventional pressure plugs are generally reliable when used in
conventional cementing operations. However, using conventional
pressure plugs in tubular expansion operations has caused problems
due to the plug's inherent slack movement between its lower
position defined by the stop shoulder against the landing
receptacle and its upper position defined by the latch ring and the
receiving groove in landing receptacle. This slack displacement of
the plug between its upper and lower positions is necessary to
ensure the latching of the latch ring in the receiving groove.
During the tubular expansion process, the cycles of pressurization
and depressurization of the system cause movements of the plug
between its upper and lower positions which may result in loss of
the seal provided by the rings and jeopardize the expansion
process. A failed expansion process often requires an expensive
sidetracking of the well or abandonment.
[0008] After expansion of the tubular, the shoe with the pressure
plug needs to be drilled-out to continue drilling the well. It is
desirable to prevent the rotation of the plug during drillout in
order to considerably reduce drillout time. The conventional
anti-rotational plugs include locking clutches in the nosepiece and
in the landing receptacle in the shoe. The locking clutches prevent
the rotation of the plug in the shoe but occasionally interfere
with the latching of the plugs and may allow fluid back-flow and
impede the sealing of the plug.
[0009] Several solutions of these problems, such as using multiple
plug systems, have been attempted, but, none have proven
satisfactory. Consequently, there is a need for a pump-down
pressure plug system which provides a reliable seal capable of
withstanding multiple high pressure cycles. There is a further need
for a non-rotational plug that provides fast drillout.
BRIEF SUMMARY OF SOME OF THE PREFERRED EMBODIMENTS
[0010] These and other needs in the art are addressed in one
embodiment by a pressure plug system comprising a pressure plug
with a tapered section, a receiving landing receptacle having a
tapered section with substantially the same tapering angle as
tapered section of the pressure plug, and tapering angle being less
than the friction angle corresponding to the coefficient of
friction between the pressure plug and the landing receptacle. The
pressure plug engages the receiving landing receptacle providing a
reliable seal and locking the plug against landing receptacle
preventing axial movement under cycling pressure and rotation of
the plug during drillout.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] For a detailed description of the preferred embodiments of
the invention, reference will now be made to the accompanying
drawings in which:
[0012] FIG. 1 shows a typical prior art pump-down pressure
plug.
[0013] FIG. 2 shows a cross-sectional view of a pressure plug in
accordance with the present invention.
[0014] FIG. 3 shows a cross-sectional view of a pressure plug
engaged in a landing receptacle in accordance with the present
invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0015] FIG. 2 shows main geometrical features of the pump-down
pressure plug 20 according to the present invention. The pressure
plug 20 comprises a nose section 10, having a forward end 12 and a
rearward end 18. The plug 20 has a conical section of the length L
which is tapered towards the front 12 under the tapering angle
.alpha.. The plug 20 also comprises an optional cylindrical section
15 of a constant diameter D with a pair of external annular grooves
in which are disposed a pair of seal rings such as O-rings 16. A
pair of rubber cups 14 is disposed on the rod as shown and are
abutted against the rearward side of the plug nose 18.
[0016] FIG. 3 shows the pressure plug system with the pressure plug
20 being engaged in the landing receptacle 30 having a tapered
section 31 under the same angle .alpha. as the plug 20, and an
optional cylindrical section 32 of a constant diameter. During
normal operation the plug 20 is pumped down through the drill pipe
until the plug is landed in the landing receptacle 30. Under the
applied pressure P.sub.t, a certain interference stress between the
plug 20 and the landing receptacle 30 in the tapered section 31 is
developed. Then, if the tapering angle .alpha. is substantially
small, the plug will be locked in the landing receptacle, since it
will be so firmly seated in the landing receptacle that there will
be considerable frictional resistance to any force tending to
remove or rotate the plug relative to the landing receptacle.
[0017] In general, in order to achieve locking of the plug in the
landing receptacle, the tapering angle, .alpha., should be less
than the friction angle corresponding to the coefficient of
friction between the plug and the landing receptacle. The friction
angle, .rho., is related to the friction coefficient, .mu., as:
.mu.=tan(.rho.)
The maximum back pressure, P.sub.b, see FIG. 3, which can be held
by the pressure plug 20 after it has been engaged in the landing
receptacle 30 by applied pressure P.sub.t can be estimated as:
P b = tan ( .rho. - a ) tan ( .rho. + a ) P t ##EQU00001##
For example, if friction coefficient .rho.=0.1 and pressure plug
tapering angle .alpha.=1.5 degrees, the maximum back pressure
P.sub.b will be approximately 58% of the pressure P.sub.t applied
at the engagement of the pressure plug in the landing receptacle.
It was found through experimentation and finite element modeling
that pressure plugs with tapering angle .alpha. from approximately
0.5 to approximately 6 and preferably from 1 to 3 degrees are most
useful.
[0018] The ratio of the length, L, to the diameter, D, of the
tapered section of the pressure plug, see FIG. 2, should be
selected based on the maximum expected pressure, P.sub.t, the yield
stresses of the pressure plug and the landing receptacle material,
and on the geometry of the landing receptacle. It was found through
experimentation and finite element modeling that pressure plugs
with L/D ratios of approximately 1 to approximately 6 and
preferably of 2 to 4 are most useful.
[0019] In this embodiment, pressure plug described above provides
both resistance to back pressure and resistance to rotation of the
plug relative to the landing receptacle, and creates a
metal-to-metal seal between the plug and landing receptacle.
However, in cases having the possibility of the tapered area of the
plug to be scratched or damaged during pump-down deployment, it is
desirable to provide another embodiment with a secondary sealing
mechanism. This can be accommodated by incorporating an optional
cylindrical section 32, see FIG. 3. The cylindrical section 15 of
the plug includes grooves with elastomeric rings 16 adapted to
sealingly engage in a cylindrical section of the landing
receptacle.
[0020] One of the main advantages of the pressure plug system
according to present invention compared to conventional pressure
plugs is the lack of a slack movement upon cycling of pressure and
thus the pressure plug system according to present invention
provides a more reliable pressure seal. The other advantage of the
pressure plug system according to present invention is its
resistance to rotation of the pressure plug during drill-out
operations without utilizing locking clutches. Thus, the latching
of the plug is more reliable than the latching of conventional
anti-rotational plugs.
[0021] It should be understood that a pressure plug according to
present invention can be made of any suitable material, preferably
easily drillable material such as, but not limited to, metal
alloys, aluminum, brass, cupper, bronze, phenolic resins, polymeric
materials, or reinforced plastics.
[0022] The foregoing description and drawings of the invention are
explanatory and illustrative thereof, and various changes in sizes,
shapes, materials, and arrangements of parts may be made within the
scope of the appended claims without departing from the spirit of
the invention.
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