Boring or penetrating the earth – Processes – Boring curved or redirected bores
Reexamination Certificate
2000-10-04
2003-12-09
Lee, Jong-Suk(James) (Department: 3673)
Boring or penetrating the earth
Processes
Boring curved or redirected bores
C175S107000, C166S381000
Reexamination Certificate
active
06659200
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to improved apparatus and methods for operating a downhole actuator system, and more particularly to a downhole actuator system for driving another downhole component with a large actuation force, and still more particularly to a valveless and reversible hydraulic piston actuator system that actuates a piston to drive another downhole member with a large actuation force and then resets the piston to its pre-actuation position.
BACKGROUND OF THE INVENTION
The conventional practice for actuating a piston downhole under high loads requires a hydraulic actuation system having many component parts, including valves.
FIG. 1
illustrates a typical prior art downhole actuation system, which includes a closed hydraulic system
100
having a cylinder
110
with an internal piston
120
disposed therein, a reservoir
130
to store hydraulic fluid, a pump
140
to move the hydraulic fluid, and valves
150
,
160
to direct the hydraulic fluid flow. The pump
140
is driven by a prime mover such as an electric motor.
The cylinder
110
includes a high-pressure chamber
112
on one side of the piston
120
and a low-pressure chamber
114
on the other side of the piston
120
. The piston
120
includes a shaft
122
that drives another downhole member when piston
120
is actuated. The reservoir
130
is a separate, closed container used to store the hydraulic fluid under high pressure. The pump
140
is disposed between the reservoir
130
and the cylinder
110
such that the pump suction line
142
communicates with the reservoir
130
and the pump discharge line
144
communicates with high-pressure chamber
112
. Valve
150
, with solenoid or motor operator
152
, is located on the pump discharge line
144
leading into cylinder
110
. Valve
160
, with solenoid or motor operator
162
, is located on the reservoir return line
132
connecting the pump discharge line
144
to the reservoir
130
. Valves
150
,
160
direct the flow of hydraulic fluid between the reservoir
130
and the high-pressure chamber
112
, and the fluid path depends upon whether valves
150
,
160
are open or closed.
The hydraulic system
100
has three operating configurations: 1) actuating, 2) recirculating, and 3) reverse, determined by the open or closed positions of valves
150
,
160
. To actuate the piston
120
, the operator places the hydraulic system
100
in the actuating configuration by opening valve
150
, closing valve
160
, and turning on the pump
140
. Hydraulic fluid flows along flow path
170
out of the reservoir
130
, into the pump suction line
142
, through the pump
140
, which increases the hydraulic fluid pressure, and into the pump discharge line
144
. With valve
160
closed, the flow path into the reservoir return line
132
is blocked, and as indicated by flow arrow
172
, the hydraulic fluid flows through valve
150
and into high pressure chamber
112
to actuate the piston
120
. As the piston
120
moves forward within cylinder
110
, shaft
122
drives a downhole member associated with the piston shaft
122
.
To momentarily maintain the piston
120
in a stationary position without shutting down the pump
140
, the operator can place hydraulic system
100
in the recirculating position by closing valve
150
and opening valve
160
. With valve
150
closed, the flow path into cylinder
110
is blocked, and as indicated by flow arrow
174
, the hydraulic fluid flows through valve
160
, into the reservoir return line
132
, and back to the reservoir
130
along flow path
178
. The piston
120
is therefore maintained in a stationary position because hydraulic fluid is prevented from entering or exiting cylinder
110
. To maintain piston
120
in a stationary position for a longer duration, the pump
140
can be shut off and both valves
150
,
160
closed to prevent hydraulic fluid flow.
To move the piston
120
back up in cylinder
110
and reposition it for another actuation, the hydraulic system
100
is placed in a reverse configuration by opening both valves
150
,
160
and shutting off the pump
140
. As indicated by flow arrow
176
, if the pressure in the reservoir
130
is lower than the pressure in the high-pressure chamber
112
, hydraulic fluid will tend to flow out of chamber
112
through valves
150
,
160
, through reservoir return line
132
, and back into reservoir
130
along flow path
178
, thereby allowing piston
120
to move upward in cylinder
110
.
The conventional hydraulic actuation system
100
of
FIG. 1
comprises a complex configuration of parts working together in a closed system. In particular, the valves
150
,
160
of the conventional hydraulic actuation system
100
are problematic because they have close internal tolerances and small diameter ports and holes for hydraulic fluid flow, making the valves
150
,
160
susceptible to clogging due to small particles entering the valve internals. To ensure the valves
150
,
160
do not fail or operate ineffectively, filters and screens are required to prevent small particles from entering the valve internals. It would be advantageous to have a less complex configuration than the conventional hydraulic actuation system
100
. In particular it would be advantageous to have a closed hydraulic system that eliminates the need for valves
150
,
160
and can also operate bi-directional to actuate a piston under high loads and then reset the piston. It would further be advantageous to have an actuation system that provides a precise movement of the actuation shaft.
The present invention overcomes the deficiencies of the prior art.
SUMMARY OF THE INVENTION
The actuator system of the present invention is a valveless, high pressure, positive displacement, axial drive system including a hydraulic fluid reservoir, a hydraulic enclosure, a bi-directional pump assembly driven by an electric motor, and a piston assembly, all contained within an actuator housing. The actuator system may also include a piston repositioning assembly connected to the hydraulic enclosure but separated from the actuator housing.
The hydraulic fluid reservoir maintains fluid communication with the hydraulic enclosure and has an internal compensating piston that adjusts with the changes in fluid level in the reservoir. The hydraulic enclosure encapsulates the pump assembly and piston assembly in hydraulic fluid and provides a closed system that prevents hydraulic fluid contamination, such as by drilling fluids. The hydraulic enclosure includes a low-pressure cavity and a low-pressure chamber above the pump, a high-pressure chamber below the pump, and a piston cylinder defined as the area within which the piston reciprocates.
An electric motor drives the pump and includes electrical conductors, a power section, and a driveshaft. The electrical conductors provide power to the power section. The power section of the motor, which is mounted internally of the actuator housing but outside the hydraulic enclosure, turns the drive shaft, which extends into the hydraulic enclosure. The drive shaft is supported by combination thrust and radial bearings, and there is fluid communication across the bearings so that the motor is exposed to the same pressure as the hydraulic enclosure. Because the drive shaft support bearings do not seal the motor from the hydraulic enclosure pressure, the bearings do not create frictional loses that reduce the force capacity of the system. The lower end of the drive shaft is connected to a linkage, and the linkage is connected to the rotor of the bi-directional pump.
The bi-directional pump assembly preferably utilizes a moineau pump, but can use any type of reversible pump capable of providing adequate pressure to drive the piston with a high actuation force. The pump includes a stator through which the rotor is disposed. The lower end of the rotor extends through a bearing pack, which supports the rotor as it moves. There is a passageway through the bearing pack so that hydraulic fluid can readily flow from the pump to the positioning piston. The lower
Conley & Rose, P.C.
Halliburton Energy Service,s Inc.
Lee Jong-Suk(James)
LandOfFree
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