Wellbore liquid recovery apparatus and method

An apparatus for recovering liquids from a wellbore includes a primary pump for pumping a primary fluid through a primary fluid conduit positioned in the wellbore, and a secondary, displacement-type pump. The displacement pump includes a recovery section and a drive section, the volume of the recovery section being adapted to vary in inverse proportion with the volume of the drive section. The secondary or displacement pump also includes an inlet arrangement with a suitable one-way valve for allowing wellbore liquid to flow into the recovery section, and an outlet arrangement adapted to carry liquid expelled from the recovery section to the surface. A venturi body is connected in the primary fluid conduit and is adapted to produce a reduced pressure at a venturi outlet as the primary pump pumps the primary fluid through the conduit and venturi body at a first flow rate and with a first pressure differential across the venturi body. A connecting line connects the venturi outlet to the drive section of the displacement pump. A flow control arrangement preferably positioned at the surface controls the flow of fluid through the primary fluid conduit to selectively apply the reduced pressure at the venturi outlet or divert fluid from the primary conduit through the venturi outlet to operate the displacement-type pump to lift fluids to the surface.

BACKGROUND OF THE INVENTION 
This invention is directed to an apparatus and method for recovering 
liquids from a wellbore, and particularly, to an apparatus and method for 
recovering hydrocarbon contaminants from a subterranean water bearing 
formation. 
In many cases hydrocarbon liquids that leak from surface or subsurface 
tanks eventually seep into underground water bearing formations. The 
relatively low density hydrocarbon liquids collect on top of the water in 
the subterranean formation and pose the risk of entering water wells or 
running streams in areas surrounding the point where the leak has 
occurred. The best way to reduce these risks and their associated health 
hazards is to remove the hydrocarbon liquids from the water formation, 
preferably before they spread from the entry area. 
U.S. Pat. No. 4,273,650 to Solomon illustrates one arrangement for 
recovering low density contaminant liquids from a water saturated 
subterranean formation. Solomon uses two separate electrical submersible 
pumps suspended in a wellbore extending substantially into the water 
bearing formation, through the hydrocarbon contaminant zone. The wellbore 
is lined with a perforated casing that allows the hydrocarbon liquid and 
water to collect in the wellbore in position to be pumped to the surface 
by the two submersible pumps. One pump operates to continuously pump water 
from the wellbore at a flow rate sufficient to produce a cone of 
depression in the water bearing formation around the wellbore. The cone of 
depression increases the rate of contaminant flow into the wellbore by 
increasing the gradient to the wellbore. The collected contaminant liquid 
is pumped from the well by the second submersible pump at a relatively 
lower flow rate. 
Although Solomon proposed using two submersible electrical pumps, other 
pump arrangements may include an electrical submersible pump for pumping 
water at the relatively high flow rate, and a lower flow rate pump such as 
a displacement-type pump for recovering the hydrocarbon liquid from the 
well. The submersible pump is well suited for removing water at relatively 
high flow rates and a displacement-type pump, such as a bladder pump or 
reciprocating piston pump, is suitable for recovering the hydrocarbon 
liquids at a lower rate of recovery. 
Where a submersible electric pump was used to lift the collected 
hydrocarbon liquids, downhole level controls were required to operate the 
submersible pump only for short periods of time when a sufficient volume 
of hydrocarbon liquid had built up in the well. The submersible pumps were 
not capable of lifting fluid at a continuous, low flow rate. Although a 
displacement-type hydrocarbon recovery pump could be operated continuously 
at a low recovery rate, and thus eliminated the need for downhole level 
controls, the use of a displacement-type pump for the hydrocarbon in 
conjunction with a submersible electric pump for the water had its own 
disadvantages. Where the hydrocarbon recovery pump was a pneumatic 
operated pump, the recovery system required separate pneumatic control 
lines at the surface and in the well, an air compressor, and a motor for 
powering the compressor. Thus, these prior systems were expensive, and 
required excessive maintenance of surface power and control equipment. 
SUMMARY OF THE INVENTION 
It is a general object of the invention to provide an apparatus for 
recovering liquids from subsurface water formations that overcomes the 
above-described problems and other deficiencies associated with prior 
wellbore liquid recovery devices. Another object of the invention is to 
provide an improved method for recovering liquids, particularly low 
density contaminant liquids, from subsurface water formations. 
An apparatus according to the invention includes primary pumping means for 
pumping or lifting a primary liquid from a well through a primary fluid 
recovery conduit, and a secondary pump for pumping a secondary or 
contaminant fluid from the well through a secondary fluid recovery 
conduit. The apparatus also includes pressure reduction means connected in 
the primary fluid conduit and flow control means for selectively diverting 
primary fluid to the secondary pump. The primary pumping means comprises a 
pump adapted to lift fluid from the well at a substantially constant first 
flow rate and the secondary pump comprises a displacement-type pump. The 
pressure reduction means preferably comprises a venturi body adapted to 
produce a reduced pressure in response to the flow of primary fluid 
through the primary fluid conduit at the first flow rate. This reduced 
pressure is applied to the secondary, displacement-type pump alternately 
with the diverted primary fluid so as to drive the secondary pump and lift 
the secondary fluid from the well. Thus the apparatus according to the 
invention utilizes the primary fluid pumped by the primary pumping means 
to operate the secondary pump, thereby eliminating the need for a separate 
power source for the secondary, displacement-type pump. 
When the apparatus is used to recover hydrocarbon liquids from a water 
formation, the primary fluid pump preferably comprises an electrical 
submersible pump adapted to lift water, the primary fluid, from the well 
at a sufficient flow rate to produce a desired cone of depression in the 
water bearing formation around the wellbore. The secondary or 
displacement-type pump includes a pump housing having a drive section and 
a recovery section separated by a bladder, piston, or other means for 
enabling the volume of the recovery section to vary in inverse proportion 
to the volume of the drive section. Inlet means including an inlet check 
valve is connected to secondary pump housing in position to allow 
hydrocarbon liquids, the secondary fluid, collected in the wellbore, to 
enter the secondary pump recovery section. Outlet means including the 
secondary fluid conduit and an outlet check valve is also connected to the 
secondary pump recovery section. 
The venturi body or pressure reduction means includes a constricted flow 
section and an outlet leading from the constricted flow section. A drive 
conduit connects the venturi outlet to the drive section of the secondary 
pump housing. Thus the pressure at the outlet of the venturi body may be 
applied directly to the secondary pump drive section. 
The preferred flow control means includes a surface valve arrangement for 
controlling the pressure differential across the venturi body connected 
downhole in the primary fluid conduit. The surface valve arrangement 
includes a discharge line connected to the primary conduit and a cut-off 
valve connected in the discharge line. A bypass line is connected to the 
discharge line in position to bypass the cut-off valve and an adjustable 
bypass valve and pressure gauge are connected in the bypass line. 
This preferred flow control means has two states of operation. In a first 
state of operation the cut-off valve is open so as to allow the primary 
fluid pumped by the primary pump to flow freely from the well at the first 
flow rate. This first flow rate produces a sufficient pressure 
differential across the venturi body to produce a desired reduced pressure 
at the venturi outlet. The reduced pressure is applied to the drive 
section of the secondary, displacement-type pump to reduce the volume of 
the drive section and thereby increase the volume of the recovery section, 
allowing secondary fluid to flow into the recovery section through the 
secondary pump inlet means. Once the recovery section is expanded to its 
greatest possible volume and is full of secondary liquid, the cut-off 
valve is closed to direct all output from the primary conduit through the 
bypass line and the adjustable bypass valve. The adjustable bypass valve 
is adjusted to decrease the pressure differential across the downhole 
venturi body and thereby produce an increased pressure at the venturi 
outlet port. This increased pressure diverts fluid from the primary fluid 
conduit through the drive conduit and into the drive section of the 
secondary pump to expand the drive section. As the drive section expands 
it expels secondary fluid previously drawn into the recovery section and 
lifts the secondary fluid from the well through the secondary fluid 
conduit. 
In the preferred form of the invention the apparatus also includes a return 
line connected in the surface discharge line in position to return a 
desired volume of the first primary fluid to the well. This allows the 
primary pump to lift primary fluid through the primary conduit at the 
first flow rate to produce the desired reduced pressure at the venturi 
outlet while maintaining a lower water production rate from the well 
sufficient to produce the desired cone of depression in the water 
formation. 
An alternate flow control means includes surface controlled downhole valves 
connected to supply the desired pressure to the drive section of the 
secondary pump. This alternate downhole valve flow control means includes 
a separate lift conduit connected between the secondary pump drive section 
and the primary fluid conduit, a surface controlled lift valve positioned 
in the lift conduit, and a surface controlled valve connected in the drive 
conduit. These two valves are alternately opened and closed to alternately 
supply the desired reduced pressure and primary fluid pressure to operate 
the secondary, displacement-type pump. 
Although the wellbore liquid recovery apparatus according to the invention 
is particularly well suited for applications in which the primary fluid is 
a fluid being recovered from the well, those skilled in the art will 
readily appreciate that the primary fluid need not be a fluid produced or 
recovered from the well. The primary fluid can be supplied from the 
surface and pumped from the surface to the downhole venturi body through a 
suitable conduit. The primary fluid would then be returned to the surface 
through the primary fluid conduit and eventually recycled downhole to 
drive the displacement pump through the venturi body. 
The method of the invention and the operation of the apparatus described 
above includes first pumping the primary fluid through the primary fluid 
conduit in the wellbore to create a reduced pressure at the downhole 
venturi body and then applying the reduced pressure to fill the secondary, 
displacement-type pump with secondary fluid. Next, the method includes 
diverting primary fluid from the primary fluid conduit to the drive 
section of the displacement-type pump to expel liquid previously collected 
in the secondary pump. The method of the invention may also include 
returning primary fluid to the well in order to maintain the desired first 
flow rate through the primary fluid conduit and venturi body while 
recovering the primary fluid from the well at a lower optimum rate for 
producing the desired cone of depression in the formation. 
These and other objects, advantages, and features of the invention will be 
apparent from the following description of the preferred embodiments, 
considered along with the accompanying drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
FIG. 1 shows a wellbore liquid recovery apparatus 10 embodying the 
principles of the invention. The apparatus 10 is particularly adapted for 
recovering water and a hydrocarbon or other low density liquid pollutant 
or contaminant from a water remediation well generally indicated at 
reference numeral 12. The well 12 extends from the surface substantially 
into a water bearing formation 14 having a distinct hydrocarbon liquid 
phase 15 collected in the formation above the water level. The well 12 
would normally be lined or cased with a perforated casing (not shown) 
having perforations in the length traversing the water bearing formation 
enabling the formation fluids to enter and collect in the well to be 
recovered by apparatus 10. 
The preferred apparatus 10 shown in FIG. 1 includes primary pumping means 
comprising pump 16 and a secondary pump 18. The primary pump 16 is adapted 
to lift a primary fluid, in this case water, from the well 12 through a 
primary fluid conduit 20 at a first flow rate. The secondary pump 18 is 
adapted to lift a secondary fluid, in this case the collected hydrocarbon 
liquid 15, to the surface through a secondary fluid conduit 22. Pressure 
reduction means 24 and flow control means indicated at reference numeral 
26 are also included in the apparatus 10. The pressure reduction means 24 
is connected in the primary fluid conduit 20 and has a outlet port 28 
connected to the secondary pump 18 through drive conduit 30. The flow 
control means 26 is adapted to control the flow of primary fluid through 
the primary fluid conduit 20 and the pressure reduction means 24 to 
alternately produce a reduced pressure or increased pressure at the port 
28. This alternating pressure is applied through the drive conduit 30 to 
operate the secondary pump to lift the hydrocarbon liquid 15 to the 
surface. 
The primary pump 16 in this preferred form of the invention comprises an 
electric submersible pump powered through an electric power supply 32 at 
the surface. The electrical connection to the pump 16 is not shown in FIG. 
1 although those skilled in the art will readily appreciate that such a 
connection is required to operate the pump. Submersible pumps are well 
suited for lifting fluids from a well at a flow rate required in this 
preferred form of the invention. 
The secondary pump 18 comprises a suitable displacement-type pump having a 
housing 36 separated into a recovery section 38 and a drive section 40 
preferably by an expandable bladder 42. Inlet means comprising an inlet 
check valve 44, a length of flexible coil tubing 46, and an inlet float 48 
are connected to feed hydrocarbon liquid 15 collected in the well 12 to 
the recovery section 38 of the secondary pump housing 36. The inlet float 
48 is adapted to float at the water/hydrocarbon interface in the well 12 
and acts to skim hydrocarbon liquid into the secondary pump housing 36. 
Outlet means for carrying the hydrocarbon liquid 15 from the secondary 
pump 18 to the surface includes the secondary fluid conduit 22 and an 
outlet check valve 50 connected to prevent back 1 flow from the conduit 
into the pump housing 36. The bladder pump also includes a drive port 52 
extending into the drive section 40 of the pump and connected to the 
outlet 28 of the pressure reduction means 24 through the drive conduit 30. 
The pressure reduction means 24 preferably comprises a venturi body having 
a constricted section indicated schematically at reference numeral 58. The 
outlet or port 28 opens into this constricted section. The constricted 
section 58 is sized, as is well known in the art, to produce a desired 
reduced pressure at the venturi outlet 28 in response to the flow of 
primary fluid through the primary fluid conduit 20 and venturi body 24 at 
the first flow rate and at a desired pressure differential across the 
venturi body. The pressure at the venturi outlet 28 is preferably 
monitored by a surface gauge 60 connected to the drive conduit by a 
suitable small diameter tubing 62. In alternate forms of the invention, a 
downhole pressure sensor connected to a suitable readout device at the 
surface may be employed for monitoring the pressure in the drive conduit 
30. 
The preferred flow control means 26 shown in FIG. 1 includes a surface 
discharge line 68 connected to the primary fluid conduit, and a control 
valve arrangement. The surface valve arrangement includes a cut-off valve 
70, preferably a solenoid operated valve, connected in the discharge line 
68 and adapted to either reside in a fully open position or a fully closed 
position. A bypass line 72 is connected to the primary fluid discharge 
line 68 in position to bypass the solenoid operated cut-off valve 70. An 
adjustable valve 74 and a pressure gauge 76 are connected in the bypass 
line 72. As shown in FIG. 1, the preferred solenoid operated cut-off valve 
70 is connected to a timer 78 for selectively energizing the solenoid to 
control the condition of the valve. The timer 78 may be operated through 
the same electrical power source 32 used to operate the submersible 
primary pump 16. 
In operation, the primary pump 16 is operated to pump primary fluid through 
the primary fluid conduit 20 at the first flow rate when the cut-off valve 
70 is open. In this form of the invention the primary fluid is water 
collected in the well and the first flow rate is a rate capable of 
producing a cone of depression in the water bearing formation around the 
well 12. The flow of primary fluid through the venturi body 24 at the 
first flow rate produces a reduced pressure at the venturi outlet 28 of 
the venturi body. This reduced pressure is applied through the drive 
conduit 30, and drive port 52 to the drive section 40 of the secondary 
pump 18 defined within the bladder 42. The reduced pressure applied to the 
secondary pump bladder 42 contracts the bladder to increase the volume of 
the pump recovery section 38 which fills with hydrocarbon liquid entering 
through the inlet float 48, coil tubing 46, and inlet check valve 44. 
In order to expel the hydrocarbon liquid received in the secondary pump 
recovery section 38, a portion of the primary fluid from the primary fluid 
conduit 20 is diverted through the venturi outlet 28 to the bladder 42 to 
expand the bladder. As the bladder expands it forces the collected 
hydrocarbon liquid previously collected in the pump recovery section 38 to 
the surface through the conduit 22 and outlet check valve 50. In the 
preferred form of the invention shown in FIG. 1, this step of diverting 
primary fluid from the primary fluid conduit 20 includes closing the 
cut-off valve 70 to direct all of the primary fluid through the bypass 
line 72 and the adjustable bypass valve 74. The adjustable bypass valve 74 
is adjusted to provide a back pressure sufficient to decrease the pressure 
differential across the venturi body 24 to a point at which primary fluid 
flows through the venturi outlet 28, drive conduit 30, and drive port 52 
to expand the bladder 42 of the secondary pump 18 at a pressure required 
to lift the hydrocarbon liquid to the surface. Primary fluid is diverted 
to the secondary pump bladder 42 until the bladder expands to take up 
substantially the entire volume of the pump housing 42. This maximum 
bladder expansion can be monitored at the surface by monitoring the output 
from the secondary fluid conduit 22. Also, the pressure condition in the 
drive conduit 30 is monitored by the gauge 60 connected to the drive 
conduit. 
In the form of the invention shown in FIG. 1 the cut-off valve 70 is 
solenoid operated and the solenoid is energized periodically using the 
timer 78. The timer is set to open the cut-off valve 70 for a sufficient 
period to fully contract the secondary pump bladder 42 with the reduced 
pressure produced at the venturi body 24, and then close the cut-off valve 
for a sufficient period of time to fully expand the bladder. 
The apparatus shown in FIG. 1 also includes primary fluid return means 
comprising a return conduit 80 connected to the discharge line 68, an 
adjustable constant pressure regulator valve 82, and an adjustable return 
valve 84. The primary fluid return means operates to maintain a water 
production rate necessary to produce an optimum cone of depression in the 
reservoir around the well 12 even though a higher flow rate is required 
through the venturi body 24 to produce the desired reduced pressure at the 
venturi outlet 28. Thus the primary fluid return means eliminates the need 
to size the venturi body for each particular well. The pressure regulator 
valve 82 is set to return primary fluid, water, to the well from the 
discharge line 68 at a constant pressure adapted to maintain the desired 
water production rate. Because a portion of the lifted water is returned 
to the well, the flow rate through the venturi body 24 necessary to 
produce the desired reduced pressure at the venturi outlet 28 may be a 
flow rate higher than that flow rate corresponding to the optimum water 
production rate. 
FIG. 2 shows an alternate form of the invention in which a venturi body 88 
is connected in a branch line 90 from a primary fluid conduit 92. The 
branch conduit or line 90 is connected to a branch discharge line 94 with 
a solenoid operated cut-off valve 96, bypass line 98, and bypass valve 100 
similar to the flow control means shown in FIG. 1. The branch discharge 
line 94 also includes a valve 101 for closing off the branch lines 90 and 
94 entirely. The main primary fluid conduit 92 is connected to the main 
surface discharge line 102 that includes a main line flow/pressure 
adjustment valve 104. This alternate embodiment allows adjustment of flow 
through the primary fluid conduit 92 without affecting the discharge side 
of the branch conduit 90 in which the venturi body 88 is connected. Also, 
the volume of flow required through the venturi body 88 may be reduced in 
this alternate embodiment of the invention. The surface valves 96 and 100, 
however, operate similarly to the valves 70 and 74 in FIG. 1 to produce 
the desired pressure at the venturi body 88. 
A primary pump 105 in FIG. 2 operates to lift the primary fluid, water, 
from the well similarly to the pump 16 shown in FIG. 1. The embodiment in 
FIG. 2 also includes a secondary, bladder-type pump 106 similar to the 
pump 18 in FIG. 1, although the pump 106 shown in FIG. 2 is positioned 
above the level of the secondary fluid or hydrocarbon contaminant 15 in 
the well. In this case the secondary fluid inlet means comprising an inlet 
check valve 108, a length of coil tubing 110, and the inlet float 112, 
depends from the secondary pump 106. A secondary fluid outlet line 114 
with the outlet check valve 116 is similar to the embodiment shown in FIG. 
1. This alternate placement of the displacement-type pump 106 and 
secondary fluid inlet means relies entirely on the contraction of the 
bladder 118 to draw hydrocarbon liquid into the lift section of the pump. 
This is in contrast to the embodiment shown in FIG. 1 in which the 
hydrocarbon liquid or other secondary fluid 15 reaches the secondary pump 
18 through gravity drainage along with the drawing force provided as the 
bladder 42 contracts. 
The alternate flow control means of the invention shown in FIG. 3 includes 
a downhole control valve arrangement in contrast to the surface valve 
arrangements shown in FIGS. 1 and 2. The downhole flow control means shown 
in FIG. 3 serves to alternately apply the desired reduced pressure from 
the venturi body 24 to the drive section 40 of the secondary pump 18, or 
divert primary fluid from the primary fluid conduit 20 similarly to the 
embodiment shown in FIGS. 1. A remote or surface controlled venturi outlet 
valve 122 is connected in the drive conduit 30 while a surface controlled 
lift valve 124 is connected in a lift conduit 120. The lift conduit 
extends between the primary fluid conduit 20 and the drive conduit 30. The 
desired pressure applied to the secondary pump drive section 40 is 
controlled by alternately opening and closing the remote controlled valves 
122 and 124 while the submersible pump 16 lifts primary fluid from the 
well through the primary fluid conduit 20 and venturi body 24. 
In operation of the flow control means shown in FIG. 3, the submersible 
pump 16 pumps primary fluid through the conduit 20 and venturi body 24 at 
a flow rate sufficient to produce a reduced pressure at the venturi outlet 
28. Simultaneously, the pump 16 applies a higher lift pressure to lift 
conduit 120. To contract the bladder 42 of the secondary pump 18, the lift 
valve 124 is closed from the surface and the venturi outlet valve 122 is 
opened so as to apply the reduced pressure to the secondary pump bladder. 
Once the secondary pump bladder 42 is fully collapsed, the venturi outlet 
valve 122 is closed from the surface and the lift valve 124 is opened to 
divert primary fluid under the lift pressure to the secondary pump 
bladder. This pressure expands the bladder 42 and expels hydrocarbon 
liquid from the secondary pump housing as described above with reference 
to FIG. 1. As shown in FIG. 3 the lift and venturi outlet valves are both 
solenoid operated valves and may be operated from a common power source 
such as the source 32 in FIG. 1 also used to drive the submersible pump 
16. Alternatively, the lift and venturi outlet valves 124 and 122, 
respectively, may be operated by any other means suitable for operating 
the valves downhole. 
The above described preferred embodiments are intended to illustrate the 
principles of the invention, but not to limit the scope of the invention. 
Various other embodiments and modifications to these preferred embodiments 
may be made by those skilled in the art without departing from the scope 
of the following claims. For example, although a bladder pump is shown in 
the drawings as the preferred displacement-type pump employed as the 
secondary pump 18, those skilled in the art will readily appreciate that 
other types of displacement pumps may be employed in the invention. Also, 
any suitable valves may be used to provide the various cut-off or flow 
adjusting functions described above. Furthermore, the primary fluid may be 
a fluid supplied from the surface to the downhole venturi body rather than 
a fluid actually recovered from the well. In this case the primary fluid 
pump may be positioned at the surface and connected to pump the primary 
fluid to the venturi body through a separate conduit.