U.S. patent application number 13/079083 was filed with the patent office on 2012-10-04 for hydraulically operated wellbore liquid lift using casing gas as energy source.
Invention is credited to Kenneth J. Schmitt.
Application Number | 20120247785 13/079083 |
Document ID | / |
Family ID | 46925740 |
Filed Date | 2012-10-04 |
United States Patent
Application |
20120247785 |
Kind Code |
A1 |
Schmitt; Kenneth J. |
October 4, 2012 |
HYDRAULICALLY OPERATED WELLBORE LIQUID LIFT USING CASING GAS AS
ENERGY SOURCE
Abstract
A system for lifting liquid from a wellbore includes a turbine
selectively coupled to a source of gas flow originating in the
wellbore. The turbine is arranged to convert the gas flow directly
into rotation of the turbine. An hydraulic pump is rotationally
coupled to the turbine. An hydraulic cylinder and piston are
arranged to move a sucker rod string disposed in the wellbore.
Control valves are provided to selectively apply gas flow to the
turbine and hydraulic pressure from the pump to lift the piston and
enable lowering thereof by the weight of the sucker rod string. The
system further comprises control circuits configured to operate the
control valves.
Inventors: |
Schmitt; Kenneth J.;
(Spring, TX) |
Family ID: |
46925740 |
Appl. No.: |
13/079083 |
Filed: |
April 4, 2011 |
Current U.S.
Class: |
166/372 ;
166/105 |
Current CPC
Class: |
E21B 43/121
20130101 |
Class at
Publication: |
166/372 ;
166/105 |
International
Class: |
E21B 43/00 20060101
E21B043/00 |
Claims
1. A system for lifting liquid from a wellbore, comprising: a
turbine selectively coupled to a source of gas flow originating in
the wellbore, the turbine arranged to convert the gas flow directly
into rotation of the turbine; an hydraulic pump rotationally
coupled to the turbine; an hydraulic cylinder and piston arranged
to move a sucker rod string disposed in the wellbore; control
valves to selectively apply gas flow to the turbine and hydraulic
pressure from the pump to lift the piston and enable lowering
thereof by the weight of the sucker rod string; and control
circuits configured to operate the control valves.
2. The system of claim 1 wherein the control valves comprise a gas
supply control valve to cause turbine rotation when the sucker rod
string requires lifting.
3. The system of claim 1 wherein the control valves comprise a
controllable orifice valve in a line connecting the hydraulic
cylinder to a reservoir, the controllable orifice valve arranged to
enable lowering of the sucker rod string at a selected rate.
4. The system of claim 1 further comprising an accumulator in
hydraulic communication with an intake side of the hydraulic pump,
the accumulator charged to a selected pressure and configured to
recharge using hydraulic fluid displaced from the cylinder when the
sucker rod string is allowed to drop.
5. A method for lifting liquid from a wellbore, comprising:
converting flow of gas from a wellbore directly into rotational
energy using a turbine disposed in the gas flow; converting the
rotational energy into reciprocating motion; and using the
reciprocating motion to operate a sucker rod string disposed in the
wellbore.
6. The method of claim 5 wherein the converting rotational energy
comprises rotating an hydraulic pump, and selectively directing
pressure output from the hydraulic pump to an hydraulic
cylinder/piston combination coupled to the sucker rod string.
7. The method of claim 6 further comprising stopping rotation of
the hydraulic pump, and selectively controlling rate of discharge
of hydraulic fluid from the cylinder/piston combination to enable
dropping the sucker rod string at a selected rate.
8. The method of claim 6 further comprising prepressurizing the
pump with pressure stored in an accumulator to at least partially
offset a weight of the sucker rod string.
9. The method of claim 5 wherein the flow of gas from the wellbore
is from an annular space between a wellbore casing and a wellbore
tubing disposed within the wellbore casing.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] Not applicable.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
[0002] Not applicable.
BACKGROUND
[0003] The invention relates generally to the field of removal of
liquid from gas producing subsurface wellbores. More particularly,
the invention relates to energy sources to operate hydraulic
cylinder liquid lifting devices for removal of liquid from such
wellbores.
[0004] The oil and gas industry has undergone rapid development in
the number of wells drilled for natural gas production from "shale"
reservoirs. The number of such gas producing wellbores has
increased the need for improved means for deliquification (removal
of water) of these wells with typical liquid production rates and
depths to as much as 12,000 (can we do 14,000 ft??) feet.
[0005] Hydraulically operated vertical lift cylinders attached to
the "wellhead" (control valves and related components at the
surface to control fluid flow into and out of the wellbore), like
that of electrically or gas engine powered "pump jacks"
(reciprocating beam operated sucker rod pumps), provide advantage
in many situations due to the incremental stroking of the plunger
pump to cause liquids to rise more steadily in a production tubing
disposed within the wellbore "casing" (a protective pipe extending
to proximate the bottom of the wellbore and typically cemented in
place). The action of hydraulic lift cylinders for rod pump well
deliquification overcomes a disadvantage common to plunger lift
apparatus which tends to release a larger burst of liquid when
moved upwardly in the well bore and with such liquid volume comes
associated gas. Such large volumes of liquid and gas released in a
short time may cause the need for larger separation equipment, and
sufficiently large surges of liquid and gas may disturb gas
compressor operation.
[0006] Large surges of gas negatively affect compressor intake
conditions, control and performance, whereas it can be appreciated
that much more attractive and steady flows of both natural gas and
liquids are enabled using hydraulic lift cylinder deliquification
apparatus.
[0007] It is known in the art to use internal combustion (IC)
engines to use a portion of the natural gas being produced from a
wellbore to power a conventional beam pump jack. However, this
method of producing the well has come under increasing regulatory
scrutiny, and more stringent requirements for a well operator to
use costly emissions certified IC engines, purchase and maintain IC
engine exhaust gas treatment equipment, and costly time-consuming
application for and maintenance of air emissions permits has made
such wellbore deliquification techniques less attractive
economically. In some geographic areas, for example California and
the Texas Houston air quality attainment district, increased
regulatory scrutiny and likely additional burdens will be placed on
oil and gas well operators within a relatively large geographic
areas.
[0008] Gas and oil wells tend to decline in production over time,
and some even increase liquid (particularly water) production
relative to natural gas, natural gas condensate and crude oil, the
commonly valued constituents of producing the petroleum well.
[0009] The industry's commonly accepted threshold limit for
producing natural gas and oil wells with the plunger lift method is
described, for example, in E. Beauregard, et al., Introduction to
Plunger Lift: Applications, Advantages and Limitations, Presented
at The Southwestern Petroleum Short Course, Department Of Petroleum
Engineering, Texas Tech University, Lubbock, Tex., Apr. 23-24,
1981. As can be appreciated, when the plunger lift method of
production will no longer suffice, the oil and gas well operator
has previously been faced with having to provide electricity or
burn a portion of his produced hydrocarbons in an IC engine to
provide the power to operate a sucker rod pump to lift the liquids
from the wellbore.
[0010] There exists a need for wellbore deliquification devices
that do not require the use of external power sources, such as
electricity and/or IC engines.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] FIG. 1 shows an example installation of a deliqufication
apparatus.
[0012] FIG. 2 shows example hydraulic control circuits for the
system of FIG. 1.
[0013] FIG. 3 shows a modified form of the example shown in FIG.
2.
DETAILED DESCRIPTION
[0014] The present invention provides a device and method to be
able to produce hydrocarbons from wellbores previously unable to be
produced as a result of excessive liquid production in cases where
electricity is unavailable or costly to install to the site.
Although electricity installation to wellsite would alleviate the
air emissions burden, many wells are located either far from
electricity access or where grid electricity access is difficult
and costly. Since many wells have declined below the ability to
naturally flow as a normal progression in mature production
decline, large numbers of wells exist where no grid electricity
connection has been provided to the wellsite and the costs of
installing it are a substantial burden to profitable production of
the well.
[0015] The present invention may also provide wellbore operators
with the ability to operate a sucker rod pump to remove liquid from
wells to maintain and in many cases increase production, with no
burning of a portion of produced natural gas, nor any costly,
time-consuming requirement to seek regulatory approval for air
emissions permit for IC engines, and thereafter the cost and
maintenance associated with operating the IC engine to the U.S.
Environmental Protection Agency and any state regulatory air
emissions standards.
[0016] FIG. 1 shows an example wellbore liquid lift installed on a
wellbore. The wellbore terminates at the surface at the upper end
of a wellbore casing 22. A casing head 22A may be used to seat
therein a tubing hanger and production tubing (neither shown in
FIG. 1 for clarity), wherein the production tubing is disposed
inside the casing 22. The casing 22 may include a discharge port
and associated control valve, shown at 14, for venting natural gas
pressure that accumulates in annular space between the tubing (not
shown) and the wellbore casing 22. Some of the vented gas may be
transferred through a line 19 to processing equipment (not shown in
FIG. 1) to separate water to disposal, hydrocarbon liquids for sale
and natural gas for eventual compression and transmission to a gas
transmission pipeline (not shown).
[0017] Flow and pressure of the gas from the casing 22 may be
controlled using a control/regulation valve 16. The pressure and
flow regulated gas may be transferred through a hose or piping 17
to a power conversion unit 12. The power conversion unit 12 uses
flow of natural gas from the wellhead connection (discharge port
14) to operate a turbine (30 in FIG. 2), the rotation of which may
be used to operate an hydraulic pump (32 in FIG. 2). The foregoing
components will be further explained with reference to FIG. 2. The
power conversion unit 12 may include control circuitry 12B
including, for example, a microcontroller (not shown separately) to
operate the gas control valve 16, and/or hydraulic valves as will
be further explained with reference to FIG. 2. Electrical power for
the power conversion unit circuitry 12B may be provided by
batteries and/or solar panels 12A.
[0018] Hydraulic power provided by the power conversion unit 12 may
be used to operate an hydraulic lift cylinder 20. The lift cylinder
20 may be connected to the uppermost portion of the casing 22 with
a wellhead connection having an hydraulic oil port, shown generally
at 13. The hydraulic lift cylinder 20 may raise and lower a sucker
rod string 20A. The sucker rod string 20A may be coupled at its
lower end to a conventional wellbore fluid lift pump, including,
for example, a standing valve and traveling valve therein (not
shown in the figures). During operation, the power conversion unit
12 provides hydraulic pressure to cause the hydraulic cylinder 20
to lift the sucker rod string 20A. When the sucker rod string 20A
reaches a predetermined upper travel limit, a switch 20B may
operate to send a signal to the control circuitry 12B to allow
controlled dropping of the sucker rod string 20A within the
hydraulic cylinder 20 by release of hydraulic pressure
therefrom.
[0019] In other examples (not shown) where desirable, the cylinder
20 could also be mounted at lower portion on a pedestal spaced
above the wellhead and coupled to the top of a conventional
polished rod; the cylinder/rod coupling would remain above a
conventional stuffing box throughout its stroke. An adjustable
setting spring over ball backpressure valve is shown at 15. Such
valves are commonly used to hold a backpressure on either the
tubing outlet or the casing outlet 14. Such valve 15 may be used in
the present configuration to direct all flow of gas from the casing
outlet 14 to the turbine (30 in FIG. 2) up to a certain pressure,
for example 100 to 150 pounds per square inch. Pressure exceeding
the setpoint opens the valve 15 and it then releases the gas being
produced by the well in excess of what the turbine needs to go
downstream to processing, possible compression and to a pipeline as
explained above.
[0020] FIG. 2 shows an example turbine powered hydraulic unit to
operate the hydraulic cylinder and sucker rod shown in FIG. 1. A
turbine 30 is disposed in the flow of gas from the casing 22 as
explained with reference to FIG. 1. The turbine 30 is rotated by
the movement of the gas, and such rotation may be coupled to an
hydraulic pump 32 which draws fluid such as hydraulic oil from a
reservoir 34. When it is desired to lift the sucker rod string 20A,
the control circuitry (12B in FIG. 1) may open the control valve 16
to enable turbine rotation and consequent pump 32 rotation, thus
pressurizing hydraulic fluid to flow into the hydraulic cylinder 20
to lift the sucker rod string 20A by applying hydraulic pressure
under a piston 20C connected to the rod string 20A. When the rod
string 20A reaches the upper limit of its travel, the switch (20B
in FIG. 1) may close and cause the circuitry (12 in FIG. 1) to
close the gas supply control valve 16. The flow of gas from
wellhead casing annulus ceases, as does then turbine rotation and
hydraulic pump rotation. A check valve 36 causes the flow of
hydraulic oil from out of the cylinder 20 (caused by the weight of
the rod string 20A) to be directed through a controllable orifice
valve 38, which may be manually or otherwise set to enable the rod
string 20A to drop at a practical, optimal descent rate according
to the well pumping conditions. In another example, both the
controllable orifice valve 38 and the gas supply valve 16 can be
configured to be in signal communication with the control circuitry
12B so that the rate of upstroke lift and downstroke drop of the
sucker rod string 20A may be controlled to optimum benefit, and the
control circuitry 12B may be organized to be in remote
communication via any wired or wireless communication technique
known in the art.
[0021] Shown at 44 is a pilot operated and adjustable set point (46
being the set point adjustment knob) pressure relief valve. Turning
the knob 46 changes the spring pressure on the relief valve 44 to
obtain a selected relief pressure. By addition of pilot components
including an orifice 48 and a pilot valve 42 , the relief valve 44
can also be used to open and let the hydraulic oil return on the
downstroke out of the hydraulic cylinder 20 through the relief
valve 44 into a filter 50 and ultimately into the supply reservoir
34. The hydraulic fluid flow is checked at the hydraulic pump 32
outlet (by valve 40) to prevent reverse rotation of the hydraulic
pump 32. By further explanation, by re-directing the internal pilot
line located upstream of the check valve 40, the relief valve 44
opens by reduced pressure at the pilot. Hydraulic fluid then
returns through the filter 50. The function occurs due to the
position of sourcing pilot pressure port holding the valve 44
closed, (in conjunction with internal pilot valve balance spring)
for the duration of time the hydraulic pump 32 operates to lift the
sucker rod 20A. When the upstroke lift has been completed, and the
control circuitry 12B turns off the gas flow to the turbine 30, the
pressure on the pump side of the check valve 40 drops and the
relief valve 44 opens, letting returning hydraulic oil out of the
cylinder 20 and ultimately into the reservoir 34.
[0022] The upper portion of the hydraulic cylinder 20 located above
the piston 20C may be filled with hydraulic fluid. The flow of
hydraulic fluid out of and into the upper portion may flow through
a fluid conduit 20D in fluid communication with the reservoir 34.
Such configuration may be preferred to accomplish several
beneficial functions. The first is to provide for more stable
hydraulic oil volume in the reservoir 34; this also facilitates
minimal reservoir level change in the reservoir 34 from the
upstroke to the downstroke. Another possible benefit is minimizing
outside air and moisture exchange through a reservoir breather 52.
Further, cooling of the hydraulic oil is facilitated with the
cylinder 20 releasing heat from the oil contained therein to the
outside air, since in many installations the sucker rod string 20A
can remain in its downward most position and at rest a substantial
portion of the time. Any seepage past piston 20C seals may also be
returned to the reservoir 34 because the hydraulic cylinder 20 is
hydraulically closed at both ends. The cyclic influx and discharge
of hydraulic fluid may clean and lubricate the piston/cylinder
interface for longer service life.
[0023] FIG. 3 shows a modified form of the example shown in FIG. 2,
with the addition of an accumulator arrangement useful for purposes
of energy conservation that may be particularly useful when the
system is used in deeper wells. The function of the accumulator 60
is to offset, or balance part or all of the sucker rod string lift
load. The sucker rod string 20A may be made, for example, from
steel and may weigh approximately 1.5 lbs per foot; thus a 10,000
foot length sucker rod string would weigh approximately 15,000
pounds. In such example a 4.00 inch bore diameter cylinder with a
1.5 inch diameter piston rod coupled to the sucker rod string would
require (15,000/10.8) 1389 pounds per square inch pressure applied
under the piston 20C in the hydraulic cylinder 20 to balance the
weight of the sucker rod string 20A of this example. In practice,
only a portion of the total hydraulic fluid pressure required to
offset the full weight of the sucker rod string 20A will be used.
The particular portion may be chosen according to the particular
well conditions, thus to generally maintain a sucker rod string
positive weight bias, yet reduce casing head gas and energy
consumption by almost half. A piston type accumulator may be
preferred, with additional accumulator pressure bottles provided as
needed, but the accumulator 60 can also be of the bladder type,
where a gas exerts force on hydraulic fluid through a flexible
barrier or membrane. The pump 32 receives this hydraulic fluid
under pressure to its suction port from the accumulator 60,
reducing the energy required to be exerted by the pump 32 to lift
the sucker rod string 20A. A filter 64 may be used to remove
contamination from the hydraulic fluid and may be configured in a
manner to prevent contaminants collected therein from being
re-entrained when the hydraulic fluid direction through the filter
64 is reversed. Upon completion of sucker rod lift, the relief
valve 44 opens to return the hydraulic fluid under pressure to the
accumulator 60, preserving energy for the next sucker rod lift
cycle. Pump shaft seal and/or pump case drain hydraulic fluid
seepage losses that may result from the pressure imparted by the
accumulator 60, pump and cylinder circuit can be directed to a vent
to the reservoir 34 and may be re-introduced to the pressurized
hydraulic circuit by a charge pump 62 through a check valve 63. An
adjustable relief valve 61 may mediate the reintroduction of
hydraulic fluid according to the relationship of its pressure
setting to the lowest point of pressure exerted by the accumulator
60 on the pump 32 intake when the cylinder 20 has lifted the sucker
rod 20A to its highest position. The adjustable relief valve 61
also acts to protect the charging circuit from over-pressure
conditions.
[0024] While the example embodiments explained above with reference
to FIGS. 1-3 show the hydraulic cylinder and piston being directly
coupled to the sucker rod string, it will be appreciated by those
skilled in the art that the above described system could also be
used in versions of reciprocating beam pump units (pump jacks) that
are operated by selective expansion and contraction of an hydraulic
cylinder and piston combination. In still other examples, rotation
of the turbine may be converted by devices known in the art to
cause reciprocating motion of the beam in such pump jacks, e.g.,
gearing and rotating pitman arms or cranks.
[0025] A system and method according to the various aspects of the
invention may use flow of natural gas out of a wellbore converted
directly into mechanical energy to operate a liquid lift pump in
the wellbore without the need for external sources of energy, such
as electricity, or without the need to consume the gas to release
its chemical energy (e.g., by internal combustion or catalytic
conversion.
[0026] While the invention has been described with respect to a
limited number of embodiments, those skilled in the art, having
benefit of this disclosure, will appreciate that other embodiments
can be devised which do not depart from the scope of the invention
as disclosed herein. Accordingly, the scope of the invention should
be limited only by the attached claims.
* * * * *