U.S. patent application number 13/250130 was filed with the patent office on 2012-04-05 for plunger lift and safety valve system.
This patent application is currently assigned to STELLARTON TECHNOLOGIES INC.. Invention is credited to Eric LAING, Geoff STEELE.
Application Number | 20120080196 13/250130 |
Document ID | / |
Family ID | 45888799 |
Filed Date | 2012-04-05 |
United States Patent
Application |
20120080196 |
Kind Code |
A1 |
LAING; Eric ; et
al. |
April 5, 2012 |
PLUNGER LIFT AND SAFETY VALVE SYSTEM
Abstract
A plunger lift production system uses a production string
including a bottom hole assembly, a production tubing having an
inside diameter and including a safety valve having an inside
diameter, and a plunger with an outside diameter which closely
matches the inside diameter of the safety valve, and an expandable
lug and pad assembly, which when expanded closely matches the
inside diameter of the production tubing, and when not expanded
closely matches the inside diameter of the safety valve.
Inventors: |
LAING; Eric; (Calgary,
CA) ; STEELE; Geoff; (Calgary, CA) |
Assignee: |
STELLARTON TECHNOLOGIES
INC.
Calgary
CA
|
Family ID: |
45888799 |
Appl. No.: |
13/250130 |
Filed: |
September 30, 2011 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61388257 |
Sep 30, 2010 |
|
|
|
Current U.S.
Class: |
166/369 ;
166/68 |
Current CPC
Class: |
E21B 2200/05 20200501;
E21B 43/121 20130101; E21B 34/105 20130101 |
Class at
Publication: |
166/369 ;
166/68 |
International
Class: |
E21B 43/00 20060101
E21B043/00 |
Claims
1. A plunger lift production system comprising: (a) a production
string comprising a bottom hole assembly, a production tubing
having an inside diameter and including a safety valve having an
inside diameter; (b) a plunger comprising a plunger body having an
outside diameter which closely matches the inside diameter of the
safety valve, and an expandable lug and pad assembly, which when
expanded closely matches the inside diameter of the production
tubing, and when not expanded closely matches the inside diameter
of the safety valve.
2. A method of producing fluids from a subterranean wellbore having
a production string comprising a bottom hole assembly, a production
tubing having an inside diameter and including a safety valve
having an inside diameter, the method comprising the step of
cycling a plunger within the production string through the safety
valve, wherein the plunger comprises a plunger body having an
outside diameter which closely matches the inside diameter of the
safety valve, and an expandable lug and pad assembly, which when
expanded closely matches the inside diameter of the production
tubing, and when not expanded closely matches the inside diameter
of the safety valve.
Description
FIELD OF THE INVENTION
[0001] The present invention is directed to a system using an
intermittent plunger lift and a subsurface safety valve.
BACKGROUND
[0002] As gas wells age, reservoirs deplete and gas velocities
become insufficient to lift the fluids associated with production
from the subterranean reservoir. The completion equipment alone can
provide significant challenges in maintaining unloaded production
since completion components can act as mechanical restrictions to
the production enhancement equipment designed to optimize
production.
[0003] Completion of a conventional plunger lift well consists of a
no-go seal landing assembly equipped with a standing valve and a
bumper spring disposed in the tubing string at a predetermined
depth coinciding with the uppermost selective profile nipple. The
surface equipment consists of a receiver or lubricator on surface
to receive the plunger above the wellhead. The receiver is
furnished with a manual or pneumatically actuated catcher to catch
and hold the plunger at surface. The plunger lift system cycle is
controlled using an electronic wellhead controller. The wellhead
controller controls the signal to the motor valve which opens and
closes the well to production as required and activates and
releases the catcher to catch and release the plunger at surface in
a timed sequence as programmed in the controller.
[0004] One completion component of note is the subsurface safety
valve (SSSV). These valves are typically landed about 50 m to 300 m
below the surface of the producing well. In many applications,
these SSSVs are required to remain in an active state to provide
well control in the event of an emergency, therefore, they cannot
be disabled during the production operation. Some provisions exist
including re-zoning of a producing well whereby the SSSV may be
deactivated and production of the well can continue. In this case
the SSSV remains intact but functionally disabled in the wellbore
for the remainder of the well's producing life. Therefore the
challenge becomes lifting the produced liquids to surface utilizing
the existing wellbore configuration and thereby avoiding costly
workover expenditures.
[0005] Other alternative workovers including capillary strings
specially designed to pass around a specialty SSSV. These
completions will also require workovers to pull and replace the
SSSV with the special model for capillary string installation.
[0006] Therefore, in conventional completions, bumper spring
assemblies are landed in the bottom of the well below the SSSV, and
the plunger is cycled below the valve. In this method the plunger
cycles without any control below the SSSV and therefore arrivals
cannot be identified and cannot be optimized. This type of system
results in uncontrolled cycling of the plunger between the bottom
hole spring immediately below the SSSV and the lower most spring
assembly landed at or near the end of the tubing string.
Uncontrolled cycling of the tubing plunger can result in
significant damage to many components of the plunger lift
system.
[0007] As is well known in the art, a plunger allowed to free cycle
in any tubing string in an uncontrolled fashion will lead to
significant equipment damage due to uncontrolled free fall and
rapid ascent of the plunger. The most detrimental component of this
operation is the inability to control plunger cycles to ensure that
a sufficient liquid slug travels above the plunger to cushion the
arrival at the wellhead lubricator. Equally important is allowing a
sufficient flow time between cycles to build a fluid column in the
tubing string above the bottom-hole assembly. This fluid head
serves to cushion the landing of the plunger on the bottom-hole
assembly.
[0008] Flowing the well to its best potential requires that no
significant back pressure should be present during the operation.
The addition of a safety valve in the production tubing string acts
as an obstacle to the efficient and consistent cycling of the
plunger.
[0009] Therefore, there is a need in the art for a system which
more efficiently utilizes a plunger lift system and a subsurface
safety valve.
SUMMARY OF THE INVENTION
[0010] The invention relates to a plunger lift system for lifting
produced fluids from a bottom hole spring assembly, wherein the
plunger cycles through a modified safety valve to a wellhead
receiver (lubricator) on surface.
[0011] In one aspect, the invention comprises a plunger lift
production system comprising:
[0012] (a) a production string comprising a bottom hole assembly, a
production tubing having an inside diameter and including a safety
valve having an inside diameter;
[0013] (b) a plunger comprising a plunger body having an outside
diameter which closely matches the inside diameter of the safety
valve, and an expandable lug and pad assembly, which when expanded
closely matches the inside diameter of the production tubing, and
when not expanded closely matches the inside diameter of the safety
valve.
[0014] In another aspect, the invention comprises a method of
producing fluids from a subterranean wellbore having a production
string comprising a bottom hole assembly, a production tubing
having an inside diameter and including a safety valve having an
inside diameter, the method comprising the step of cycling a
plunger within the production string through the safety valve,
wherein the plunger comprises a plunger body having an outside
diameter which closely matches the inside diameter of the safety
valve, and an expandable lug and pad assembly, which when expanded
closely matches the inside diameter of the production tubing, and
when not expanded closely matches the inside diameter of the safety
valve.
[0015] Accordingly, the plunger is able to effectively sweep the
produced liquids from the well bottom to top, through a safety
valve.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] In the drawings, like elements are assigned like reference
numerals. The drawings are not necessarily to scale, with the
emphasis instead placed upon the principles of the present
invention. Additionally, each of the embodiments depicted are but
one of a number of possible arrangements utilizing the fundamental
concepts of the present invention. The drawings are briefly
described as follows:
[0017] FIG. 1 shows a schematic of one embodiment of a production
system.
[0018] FIG. 2A shows a partial cutaway of one embodiment of a
plunger for use in a production system. FIG. 2B shows another
embodiment of a plunger with a lug and pad assembly retracted. FIG.
2C shows an end view of the view of FIG. 2B. FIG. 2D shows the
embodiment of 2B with the lug and pad assembly expanded. FIG. 2E
shows an end view of the view of FIG. 2D. FIG. 2F shows a
cross-sectional view along line 2F in FIG. 2B.
[0019] FIG. 3 shows partial cutaways of one embodiment of a
subsurface safety valve in both open and closed configurations.
[0020] FIG. 4 shows a partial cutaway of another embodiment of a
subsurface safety valve.
[0021] FIG. 5 shows a pressure trend graph in a prior art
production system.
[0022] FIG. 6 shows a pressure trend graph with implementation of a
production system and method of the present invention.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0023] The invention relates to a system and method of using a
plunger lift with a subsurface safety valve. When describing the
present invention, all terms not defined herein have their common
art-recognized meanings. To the extent that the following
description is of a specific embodiment or a particular use of the
invention, it is intended to be illustrative only, and not limiting
of the claimed invention. The following description is intended to
cover all alternatives, modifications and equivalents that are
included in the spirit and scope of the invention, as defined in
the appended claims.
[0024] Bottom hole completions for producing wells using
intermittent plungers are well known. Examples of such completion
systems are described in U.S. Pat. No. 7,347,273 issued on Mar. 25,
2008, the contents of which are incorporated by reference (where
permitted). These bottom hole completions are facilitated by
providing a bottom hole assembly which can be deployed by slickline
through a safety valve, and landed at or near the bottom of the
tubing string.
[0025] To efficiently optimize a producing well using a plunger
lift system the cycles must be controlled. Monitoring the plunger
cycle for optimizing production requires analysis of the signature
plunger arrival which can only be accomplished with recorded
arrivals. The apparatus and system for monitoring and controlling
the plunger cycle are well known in the industry and need not be
further described herein.
[0026] A wellbore schematic is shown in FIG. 1. As a result of the
completion, a bottom hole sliplock and spring assembly (10) is
landed in the production tubular (12) in the wellbore. A
thru-sleeve plunger (14) impacts the spring assembly at the end of
its descent in the wellbore, resulting in the plunger being
prepared to ascend in the production tubular under fluid pressure,
carrying production fluids with it up to the surface.
[0027] Completions of the well in this fashion to maintain unloaded
production is highly economic since the producers can avoid costly
workovers involving pulling the tubing and removing a safety valve
in favor of installing a wireline retrievable model.
[0028] The safety valve (30), one embodiment of which is shown in
FIG. 3, is designed to be placed in the production tubing, to
provide flow control in planned or unplanned shutdowns. The flapper
valve (32) opens and closes a throughbore (34) which is sized to
permit the plunger (14) to pass through. In one embodiment, the
safety valve is tubing retrievable, as contrasted with wireline
retrievable configurations. One embodiment of a tubing retrievable
safety valve or TRSSSV (30) is shown in FIG. 4.
[0029] In contrast to a conventional method of completing a plunger
lift well, a TRSSSV well equipped with a plunger lift will consist
of a hold down selective in nature since the first restriction
which it must pass through is the selective profile nipple within
the TRSSSV. The selective nature of the landing assembly allows
securing of the bottom-hole assembly and bumper spring at any
desired depth below any number of existing selective profile
nipples. This can be accomplished using a device such as that
described in U.S. Pat. No. 7,347,273, the contents of which are
incorporated herein by reference where permitted, or the like.
[0030] As shown in FIGS. 2A-2F, the plunger (14) is equipped with
specialized pad mandrels (16) with spring loaded lugs (20) design
to allow the lugs (20) and pads (18) to collapse to the outside
diameter (OD) of the plunger body and thereby guarantee passage of
the plunger through the safety valve (30). Upon expansion of the
lugs (20) and pads (18) with assistance of the spring (17), the
plunger meets the production tubing ID, while collapsing to pass
through the safety valve (30) and not substantially affecting
performance of the plunger.
[0031] As shown in FIG. 2F, the pads (18) and lugs (20) are
interlocking such that movement of the lugs causes movement of the
pads. In one embodiment, the lugs (20) are equipped with small pins
(24) which travel within radial grooves in the pad mandrel to guide
radial travel of the lug and prevent binding of the lug on the pad
mandrel.
[0032] The top sub of the plunger may incorporate a valve
mechanism, such as that described in U.S. patent application Ser.
No. 12/027,062 filed Feb. 6, 2008, the contents of which are
incorporated herein by reference, where permitted. Therefore, when
the plunger is falling through the wellbore, the top valve of the
plunger remains open, allowing any gas or liquid in the wellbore to
pass through the plunger. The valve closes when the plunger lands
on the bottom hole assembly, and production pressure causes the
plunger to rise up, pushing production fluids above it to the
surface. The spring (17) pressure pushes the lugs and pads radially
outwards, to contact the production tubing surface.
[0033] In one embodiment, the plunger body comprises chamfered
edges (22) at both top and bottom ends, which facilitates entry and
passage of the plunger through the safety valve. The pads
themselves are chamfered or rounded such that when the plunger
enters the reduced diameter bore of the safety valve, the pads are
physically retracted into the plunger, as is shown in FIGS. 2B and
2C. Upon exiting the safety valve, the spring (17) assists in
expanding the pads once again, as is shown in FIGS. 2D and 2E. The
plunger preferably has enough mass to allow easy passage downwards
through the safety valve.
[0034] In this system and method, efficient use of the existing
completion/tubing strings in a given wellbore may be made. The
plunger (14) cycles through the tubing retrieved sub- surface
safety valve (30). In this case, the safety valve (30) valve
remains intact and operational whilst the fluid is produced to
surface cycling the plunger (14) through the safety valve.
[0035] Due to the low reservoir pressures in a typical plunger lift
application, small accumulations of fluid in the tubing string can
dramatically decrease the inflow from the reservoir. This can be
visualized by the discrepancy between the sale pressure and the
casing pressure in FIG. 4. As shown with the production trend in
FIG. 5, with the plunger in place and cycles controlled, the sales
and casing pressure trendlines are tracking very closely indicating
the flowing differential due to the accumulated liquid head in the
tubing has been eliminated. This type of information and degree of
control over the plunger lift system can be achieved by tracking
and recording the plunger arrivals and catching and holding the
plunger at surface using a programmed sequence in the wellhead
controller. The present invention permits such programmed sequences
with an active safety valve in place.
[0036] As will be apparent to those skilled in the art, various
modifications, adaptations and variations of the foregoing specific
disclosure can be made without departing from the scope of the
invention claimed herein.
* * * * *