EP0523951B1

EP0523951B1 - Downhole tool with actuator

Info

Publication number: EP0523951B1
Application number: EP92306422A
Authority: EP
Inventors: Roger L. Schultz; Craig L. Zitterich
Original assignee: Halliburton Co
Current assignee: Halliburton Co
Priority date: 1991-07-15
Filing date: 1992-07-14
Publication date: 1996-03-13
Anticipated expiration: 2012-07-14
Also published as: DE69208959T2; EP0523951A2; DE69208959D1; CA2073801A1; EP0523951A3

Description

The present invention relates generally to a downhole tool such as a downhole shut-in tool, including an actuator therefor.
Draw down and build up tests are often performed on production wells at regular intervals to monitor the performance of the producing formations in the well. A typical test setup usually includes a downhole closure valve, i.e. a shut-in valve, which is placed in the well and manipulated by slick line. There is usually a pressure recording gauge below the downhole shut-in valve which records the pressure response of the formation being tested as the valve is opened and closed. The formation is allowed to flow for a sufficient length of time to ensure that it is drawn down to a desired level. After this draw down period is complete, the shut-in valve is used to shut in the well. The formation pressure is allowed to build up for a sufficient interval of time to allow it to reach a desired level, before another draw down period is started. The entire process is then sometimes repeated immediately to acquire more pressure data from another draw down/build up test.
US-A- 4 094 359, which represents the prior art as referred to in the pre-characterising portion of claim 1, describes a bypass sub for drill stem testing.
In operation, the sub is lowered into the well on the drill string and anchored above the formation to be tested. The sub incorporates a sleeve value which is moved between open and closed positions by a wireline tool.
Shut-in valves of the prior art have typically been actuated by mechanical means and particularly by means of mechanical actuators lowered on a slick line.
We have now devised an improved actuator apparatus which is particularly, but not exclusively, useful with shut-in valve tools.
According to the present invention, there is provided a downhole tool which includes an actuator apparatus for actuating said tool, which apparatus comprises mechanical actuator means for actuating said tool; and drive means, operably associated with said mechanical actuator means, for moving said mechanical actuator means; characterised in that the actuator apparatus includes abutment means for abutting said mechanical actuator means to limit movement thereof and thereby define at least one position of said mechanical actuator means; and control means for controlling said drive means, said control means including and being responsive to a load sensing means for sensing an increased load on said drive means when said mechanical actuator means abuts said abutment means.
The invention will hereafter be mainly described with reference to downhole tools including shut-in valves, but it is to be understood that it is not limited thereto.
The present invention provides two substantial improvements in shut-in valves used in downhole tools. First, an improved shut-in valve is described which utilizes a pilot valve to direct a pressure differential across a piston which in turn closes the shut-in valve, so that the force for closing the shut-in valve is provided by the pressure differential which is defined between a low pressure zone of the tool and the higher pressure well fluid contained in the production tubing. A second improvement is provided in the context of an electric timer and control system which opens the pilot valve after a predetermined time delay. The electric timer and control system is also applicable to other types of downhole tools, such as for example, a sampler tool like that shown in our European patent specification no. 0482748A to which reference should be made for further details.
The downhole shut-in apparatus provides an apparatus for shutting in a production tubing string of a well. It includes a housing having a housing bore with a flow port means defined through the housing for communicating the housing bore with an interior of the production string to allow production fluid flow into the flow port means and up through the housing bore. The housing has a low pressure zone defined therein.
A shut-in valve element is disposed in the housing bore and movable between an open position wherein the flow port means is open and a closed position wherein the flow port means is closed.
A differential pressure actuating piston has first and second sides, the first side being communicated with the low pressure zone. The piston is operably associated with the shut-in valve element to move the shut-in valve element between its open and closed positions in response to movement of the actuating piston.
A pilot valve means is provided for communicating the second side of the actuating piston with the interior of the production tubing so that a pressure differential between the interior of the production tubing and the low pressure zone moves the actuating piston and thus moves the shut-in valve element to its closed position.
A drive and control means is provided for opening the pilot valve means. The drive and control means may more generally be described as an actuator apparatus for a downhole tool, and it is useful with the shut-in tool disclosed herein and other types of downhole tools.
The actuator apparatus includes a mechanical actuator means for actuating the tool. For example, the mechanical actuator means may actuate the pilot valve of the shut-in valve means described above.
The actuator apparatus further includes an electric motor drive means operably associated with the mechanical actuator means for moving the mechanical actuator means. The apparatus further includes abutment means for abutting the mechanical actuator means to limit movement thereof and define at least one position of the mechanical actuator means. A load sensing means, preferably a current sensing means, is provided for sensing an increased load on the electric motor drive means when the mechanical actuator means abuts the abutment means. Control means are provided for controlling the electric motor drive means in response to the load sensing means.
The actuator apparatus preferably includes an electric timer means which starts timing upon assembly of the apparatus. The control means then causes the electric motor drive means to run in a first direction to move the mechanical actuator means in a first direction until it abuts a first abutment thus stalling out the electric motor. This is sensed by the load sensing means and the control means then shuts down the electric motor. After the time interval determined by the timer means has fully elapsed, the control means will again activate the electric motor drive means and cause it to run in a second direction thus moving the mechanical actuator to actuate the tool, such as for example to open the pilot valve of the shut-in valve apparatus. When the mechanical actuator means abuts a second abutment which defines the fully open position of the pilot valve means, the electric motor drive means will again stall out. Again the load sensing means will sense this condition and the control means will subsequently again shut down.
A reset means is provided wherein the timer can be restarted by disconnecting the control means from its power supply and subsequently reconnecting the control means.
In order that the invention may be more fully understood, reference is made to the accompanying drawings, wherein:
FIGS. 1A-1B comprise a schematic elevation sectioned view of the downhole tool of the present invention in place in a production tubing string of a well.
FIGS. 2A-2E comprise an elevation partially sectioned view of the downhole tool of the present invention.
FIGS. 3 and 4 are illustrations similar to FIG. 2C showing sequential positions of the actuating apparatus as the pilot valve means is opened.
FIG. 5 is a sequential function listing for the operations carried out by the control system.
FIG. 6 is a block diagram of the control system.
FIG. 7 is a schematic circuit diagram implementing the block diagram of FIG. 6.
Referring now to the drawings, and particularly to FIGS. 1A-1B, an oil well is there shown and generally designated by the numeral 10. The well 10 is defined by a casing 12 disposed in a borehole which intersects a subterranean hydrocarbon producing formation 14. A production tubing string 16 is in place within the well casing 12 and is sealed against the casing 12 by upper and lower packers 18 and 20. A plurality of perforations 22 extend through the casing 12 to communicate the interior of the casing 12, and a lower interior 24 of the production tubing string 16 with the subsurface formation 14, so that well fluids such as hydrocarbons may flow from the formation 14 through the perforations 22 and up through the production tubing string 16.
A landing nipple 26 is made up in the production tubing string 16 before the production tubing string 16 is placed within the well 10. A landing locking tool 28 is shown in place locked within the landing nipple 26. The landing locking tool 28 carries packing 30 which seals within a seal bore 32 of landing nipple 26.
The shut-in valve apparatus 34 is connected to the landing locking tool 28 and suspended thereby from the landing nipple 26. A pressure recording apparatus 36 is connected to the lower end of the shut-in valve apparatus 34.
The shut-in valve apparatus 34 has a plurality of flow ports 38 defined through the housing thereof as seen in FIG. 1A. When the shut-in valve apparatus is in an open position, well fluids can flow from the formation 14 up through the interior 24 of production tubing string 16 as seen in FIG. 1B, then up through an annular space 40 defined between the production tubing string 16 and each of the shut-in valve apparatus 34 and pressure recording apparatus 36, then inward through the flow ports 38 and up through an inner bore of the shut-in valve apparatus 34 and the landing locking tool 28 up into an upper interior portion 42 of production tubing string 16 which carries the fluid to the surface. When the flow port means 38 of shut-in valve apparatus 34 is closed, no such flow is provided and the fluids in subsurface formation 14 are shut in so that they cannot flow up through the production tubing string 16 past the landing nipple 26.
The landing nipple 26 and landing locking tool 28 are themselves a part of the prior art and may for example be an Otis® X® landing nipple and lock mandrel as is available from Otis Engineering Corp. of Dallas, Texas.
The landing locking tool 28 with the attached shut-in valve apparatus 34 and pressure recording apparatus 36 is lowered down into the production string 16 on a slick line (not shown) and locked in place in the landing nipple 26 when it is desired to run a draw down/build up test. After the test is completed, the slick line is again run into the well and reconnected to the landing locking tool 28 in a known manner to retrieve the landing locking tool 28 with the attached shut-in valve apparatus 34 and pressure recording apparatus 36.
Referring now to FIGS. 2A-2E an elevation section view is thereshown of the shut-in tool apparatus 34.
The shut-in valve apparatus 34 includes a housing assembly 44 extending from an upper end 46 to a lower end 48. The housing assembly 44 includes from top to bottom a plurality of housing sections which are threadedly connected together. Those housing sections include an upper housing adaptor 50, a ported housing section 52, a shear pin housing section 54, an intermediate housing section 56, an intermediate housing adaptor 58, an air chamber housing section 60, a pilot valve housing section 62, a guide housing section 64, a control system housing section 66, and a lower housing adaptor 68.
The housing 44 has a housing bore 70 generally defined longitudinally through the upper portions thereof. The flow ports 38 previously mentioned are disposed in the ported housing section 52 seen in FIG. 2A and communicate the housing bore 70 with the annular space 40 of interior 24 of production tubing string 16.
The upper housing adaptor 50 has internal threads 72 for connection to the landing locking tool 28. The lower housing adaptor 68 includes a threaded extension 74 for connection to the pressure recording apparatus 36.
As seen in FIGS. 2A-2B, a shut-in valve assembly 76 comprised of upper portion 78, intermediate portion 80, and lower portion 82 is slidably received within the housing bore 70 below the flow ports 38. Shear pin means 84 initially holds the shut-in valve assembly 76 in its open position as seen in FIGS. 2A-2B. The shut-in valve assembly 76 carries upper and lower packings 85 and 86, respectively, of such a size as to seal the housing bore 70 above and below flow ports 38 when the shut-in valve assembly 76 is moved upward to a closed position as further described below. When the shut-in valve assembly 76 is moved upward to its closed position, the shear pin means 84 will shear and the shut-in valve assembly 76 will move upward until an upward facing shoulder 88 thereof engages a lower end 90 of the upper housing adaptor 50 thus stopping upward movement of the shut-in valve assembly 76 in a position defined as a closed position. When the shut-in valve assembly 76 is in that closed position, the upper and lower packings 85 and 86 will be sealingly received within housing bore portions 92 and 94, respectively.
A differential pressure actuating piston 96 has an elongated upper portion 98 and an enlarged lower end portion 100. The enlarged lower end portion 100 carries a sliding O-ring seal and backup ring assembly 102 which is sealingly slidingly received within a bore 104 of air chamber housing section 60. The elongated upper portion 98 of differential pressure actuating piston 96 is closely received within a lower bore 106 of intermediate housing adaptor 58 with an O-ring seal 108 being provided therebetween. Thus a sealed annular chamber 110 is defined between upper seal 108 and lower seal 102, and between the elongated upper portion 98 of differential actuating piston 96 and the bore 104 of air chamber housing section 60. This sealed chamber 110 is referred to as an air chamber 110 or low pressure zone 110 and is preferably filled with air at substantially atmospheric pressure upon assembly of the tool at the surface.
A pilot valve port 112 is defined through the side wall of pilot valve housing section 66 and communicates the interior 24 of production tubing string 16 with a passageway 114 which extends upward and communicates with a lower end 116 of the differential pressure actuating piston 96.
The differential pressure actuating piston 96 can be described as having first and second sides 118 and 116. The first side 118 is the annular area defined on the upper end of enlarged portion 100 and has an area defined between seals 108 and 102. The first side 118 is in communication with the low pressure air chamber 110.
A pilot valve element 120 is slidably disposed in housing 44 and carries a pilot valve seal 122 which in a first position of the pilot valve element 120 is sealingly received within a lower bore 124 of air chamber housing section 60 to isolate the lower end 116 of actuating piston 96 from the pilot valve port 112.
In a manner further described below, the pilot valve element 120 can be moved downward relative to housing 44 to move the seal 122 out of bore 124 thus communicating pilot valve port 112 with the lower end 116 of differential pressure actuating piston 96 so that a pressure differential between the well fluid within production tubing string 16 and the low pressure zone 110 acts upwardly across the differential pressure of actuating piston 96 to move the same upwards within housing 44. As the differential pressure actuating piston 96 moves upward, its upper end 126 engages a lower end 128 of shut-in valve assembly 76. The shear pin means 84 will then be sheared and the differential pressure actuating piston 96 will move upward pushing the shut-in valve assembly 76 upward until its shoulder 88 engages lower end 90 of upper housing adaptor 50 thus defining a second position of the actuating piston 98 corresponding to the closed position of the shut-in valve assembly 76.
Located below the pilot valve element 120 are a number of components which collectively can be referred to as an actuator apparatus 130 for a downhole tool and particularly as an actuator apparatus 130 for opening the pilot valve 120 of the shut-in valve apparatus 34.
The actuator apparatus 130 includes a mechanical actuator means 132 for actuating or opening the pilot valve 120. The actuator apparatus 130 also includes an electric motor drive means 134 operably associated with the mechanical actuator means 132 for moving the mechanical actuator means 132.
The mechanical actuator means 132 includes a lead screw 136 defined on a rotating shaft 138 of electric motor drive means 134. Mechanical actuator means 132 also includes a threaded sleeve 140 which is reciprocated within a bore 142 of guide housing section 64 as the lead screw 136 rotates within a threaded inner cylindrical surface 144 of sleeve 140. Mechanical actuator means 132 can also be described as including a lower extension 135 of the pilot valve 120 and an annular flange 137 extending radially outward therefrom.
Sleeve 140 has a radially outward extending lug 146 received within a longitudinal slot 148 defined in a lower portion of the guide housing section 64, so that the sleeve 140 can slide within guide housing section 64, but cannot rotate therein. Similarly, the sleeve 140 has a slot 150 defined therein within which is received a lug 152 attached to the lower extension 135 pilot valve element 120. Thus, a lost motion connection is provided between the sleeve 140 and the pilot valve element 120. Further, the threaded engagement between sleeve 140 and the lead screw 136 translates rotational motion of the shaft 148 into linear motion of the sleeve 140 which is in turn relayed to the pilot valve element 120.
In FIG. 2C, the components just described are illustrated in their initial or first position wherein the pilot valve element 120 is closed, and more particularly, where an annular shoulder 154 of flange 137 is abutted against a first abutment 156 of housing 44 which is defined by a lower end 156 of the air chamber housing section 60.
In the view of FIG. 2C, the shaft 138 and lead screw 136 have been rotated to move the sleeve 140 upward until the lower end of slot 150 engages lug 152 which in turn then caused pilot valve element 120 to move upward until shoulder 154 abutted first abutment 156 of housing 44.
The abutment 156 may be generally described as a first abutment means 156 for abutting the mechanical actuator means 132 to limit movement thereof and thereby define a first position of the mechanical actuator means 132 corresponding to a closed position of the pilot valve 120.
As will be further described below, in a subsequent operation the electric motor drive means 134 will be run in a reverse direction so as to rotate the lead screw 136 in a reverse direction and cause the sleeve 140 to move downward in housing 44. The sleeve 44 will move downward until the upper end 158 of slot 150 engages the lug 152 thus pulling pilot valve element 120 downward until lower annular shoulder 160 abuts a second upward facing abutment 162 of the housing 44. The upward facing second abutment 162 can be generally described'as a second abutment means for abutting the mechanical actuator means 132 and defining a second position thereof corresponding to the open position of pilot valve element 120.
FIGS. 3 and 4 are similar to FIG. 2C and they illustrate the movement of the mechanical actuator means 132 from its first or closed position of FIG. 2C through an intermediate position in FIG. 3 to its second or open position in FIG. 4.
In FIG. 3, the sleeve 140 has moved downward until the upper end 158 of slot 150 engages lug 152 so that further movement of the sleeve 140 will pull the pilot valve element 120 downward.
FIG. 4 shows the sleeve 140 having moved downward to its fullest extent thus pulling the pilot valve element 120 completely open, with the shoulder 160 abutting the second abutment 162.
The electric motor drive means 134 includes a gear reducer (not shown). Connected to the lower end of the electric motor drive means 134 is an electronics package or control system 164. Below that is an electrical connector 166 which connects an electrical battery power supply 168 with the control system 164.
The electric motor 134, control system 164, and power supply 168 are schematically illustrated in the block diagram of FIG. 6. FIG. 5 is a sequential function listing which represents the operating steps performed by the control system 164. It will be appreciated that the control system 164 may be microprocessor based, or may be comprised of hard wired electric circuitry.
As described above, as the electric motor drive means 134 drives the mechanical actuator means 132 in either direction, the mechanical actuator means 132 will ultimately run up against an abutment means which prevents further movement thereof. When this occurs, the shaft 138 of electric motor drive means 134 can no longer rotate and the electric motor drive means 134 is stalled. When the electric motor drive means 134 stalls it will draw an increased current from electronics package 164 which controls the flow of current from power supply 168 to the electric motor drive means 134.
The control system 164 includes a load sensing means 174 for sensing an increased load on the electric motor drive means 134, and preferably for sensing an increased current draw thereof, when the mechanical actuator means 132 abuts an abutment so that further motion thereof is prevented. The control means 164 provides a means for controlling the electric motor drive means 134 in response to the load sensing means 174 as is further described below with reference to FIGS. 5, 6 and 7.
The control system 164 further includes a timer means 176 for providing a time delay before the drive means 134 moves the mechanical actuator means 132 to open the pilot valve 120.
The control system 164 further includes a start-up initialize means 178 for setting and/or resetting the timer means 176 and starting a timing period thereof upon assembly of the apparatus 34 as further described below.
The control system 164 also includes a power switching means 179 which includes motor power switching circuit 181 and control logic circuit 183.
The start-up initialize means 178 also activates a first start-up means 180 of power switching means 179 for starting the electric motor drive means moving in a first direction so as to move the sleeve 140 upward to the position shown in FIG. 2C wherein the shoulder 154 is abutted with first abutment 156. The load sensing means 174 operates a first shut-down means 182 of power switching means 179 for shutting down the electric motor drive means 134 when it stalls out in the position of FIG. 2C.
The power switching means 179 further includes a second start-up means 184 for starting up the electric motor drive means 134 to run in a second direction so as to move the sleeve 140 downward after a time delay programmed into the timer means 176 has elapsed. A second shut-down means 186 shuts off the electric motor drive means 134 in response to a signal from the load sensing means 174 indicating that the drive motor 134 has again stalled out when the mechanical actuator means 132 has engaged the second abutment 162.
The start-up and shut-down means 180, 182, 184 and 186 are provided by various combinations of logic states A and B of the detailed circuitry shown in FIG. 7. Those logic states are further described below.

Summary of Operation

The general operation of the control system 164 is best described with reference to the sequential function listing of FIG. 5.
When the apparatus 34 is first assembled at the surface before it is placed within the production tubing string 16, the initial connection of the power supply 168 to the control system 164 by connector 166 starts a series of operations represented in FIG. 5. First the timer 174 is reset (see SET and SET in the FIG. 7 embodiment) and then starts running. It will be appreciated that the timer 174 is previously set (see Program Jumper of FIG. 7) for a predetermined time delay which is needed before the shut-in tool apparatus is to be actuated. This time delay must be sufficient to allow the shut-in tool apparatus 34 to be placed in the production tubing string 16 as shown in FIGS. 1A-1B and for the flow of production fluid up through the production fluid string 16 to reach a steady state at which point it is ready to be shut in so that the shut-in pressure test can be conducted.
Additionally, upon initial connection of the control system 164 to the power supply 168, the first start-up means 180 starts the electric motor drive means 134 running in a first direction so as to move the sleeve 140 upward (A = logic 1 and B = logic 0 in FIG. 7 embodiment).
When the mechanical actuator means 132 engages the first abutment 156 the load sensor 174 will sense that the motor 134 has stalled, and the first shut-down means 182 will then shut down the electric motor 134 (A = logic 0 and B = logic 0 in FIG. 7 embodiment).
Nothing further will happen until the timer means 176 generates a command signal indicating that the full time delay programmed therein has elapsed. In response to that command signal, the control system 164, and particularly the second start-up means 184 thereof will cause the electric motor drive means 134 to start up in the opposite direction from which it originally turned so as to cause the sleeve 140 to be moved downward thus pulling the pilot valve element 120 to an open position (A = logic 0 and B = logic 1 In FIG. 7 embodiment).
This will continue until the mechanical actuator means 132 abuts the second abutment 162 at which time the motor 134 will again stall. The load sensor 174 will again sense that the motor 134 has stalled, and in response to a signal from the load sensor 174 the second shut-down means 186 will shut down the electric motor drive means 134 (A = logic 1 and B = logic 1 in FIG. 7 embodiment).
Thus the pilot valve 120 will remain in an open position which allows the pressure differential between the production fluid and the low pressure zone 110 to move the differential pressure actuating piston 96 upwardly thus moving the shut-in valve element assembly 76 upwardly to close the flow ports 38 thus shutting in the well.
After the well is shut in, the pressure will rise and that pressure rise will be monitored and recorded as a function of time by the pressure recording apparatus 36 in a well known manner.
Subsequently, a retrieving tool (not shown) is run into the production string 36 and engages the locking landing tool 28 to retrieve the locking landing tool 28, shut-in tool apparatus 34, and pressure recording apparatus 36 from the well.
After the shut-in valve apparatus 34 is retrieved from the well, it can be reset so as to be subsequently run back into the well very simply. All that is necessary is for the power supply 168 to be disconnected from control system 164, and then subsequently reconnected. When the power supply 168 is reconnected to the control system 164 the timer 176 will be reset, the motor 134 will be started up in a first direction so as to move the mechanical actuator means 132 and the pilot valve element 120 back to the closed position of FIG. 2C, and then the other steps illustrated in FIG. 5 will be performed in sequence. Of course it is necessary for the shut-in valve apparatus 34 and particularly the shut-in valve assembly 76 to be manually reset and for the shear pins 84 to be replaced therein.
The use of the load sensing means 174 to sense the position of the electric motor drive means 134 and particularly of the mechanical actuator means 132 replaces limit switches which are typically used to determine such positions. As will be appreciated by those skilled in the art, limit switches are often unreliable in operation, and further take significant room in the assembly.
Additionally, the use of limit switches requires that fairly close tolerances be kept on the various mechanical components to insure that the limit switch will in fact be actuated when the mechanical components reach their desired locations. These close mechanical tolerances are eliminated by use of the present system which merely provides the abutments 156 and 162 which rigidly limit the movement of the moving mechanical parts. This allows relatively loose tolerances to be used on the various mechanical parts since they need only be sized so as to insure that the abutments will in fact be engaged.

Detailed Operation Of Circuitry Of FIG. 7

The following is a description of the operation of the preferred circuitry for control system 164 shown in FIG. 7. FIG. 7 is a circuit diagram implementing the block diagram of FIG. 6. Functional portions of the circuitry corresponding to the block diagram of FIG. 6 are enclosed in phantom lines and like reference numerals indicate like elements.
At the application of power, a positive going pulse of about 20 mS is generated by the NAND gate UII (pin 10). This pulse is labelled SET, and it is used to initialize the flip flop U9, and the counter-dividers U2 and U3. The SET pulse is inverted by U5, which creates SET. SET is used with the gating arrangement U4 and U5, and the U6 configure line "Kb", to provide preset requirements for U6, the divide by N counter. During this first 20 mS, U9, U2 and U3 are initialized, and U6 is loaded with the desired delay count, selected by the program jumper U7. The oscillator, U1 and Y1, is allowed to start running immediately at power up, because its 32 KhZ output is required during the first 20 mS, again for preset requirements of U6. The timer system, U1, U2, U3 and U6 begins to count down at the end of the SET pulse.
The one-shot U8a provides a greater than one second delay from power up before issuing a START signal. This was done to allow the circuitry to be initialized and stabilized before the motor load is connected. At START, the flip flop U9a produces a high at A, which starts the motor reversing. This mode gives the operator easy means to initialize the valve assembly when readying the tool for a job.
At the end of valve travel, a mechanical stop is encountered, which causes the motor to stall, causing an increase in motor current. This current increase becomes sufficient at a point to cause transistor Q5 to switch on, generating a trigger for the one-shot U8b. U8b along with the three NAND gates U11, form a timed event qualifier, which requires that the stall indication from Q5 be present for at least 200 mS (approximately), before a STALL pulse will be generated. This prevents the system from stalling from start-up surges, or other brief load surges. The first legitimate STALL resets U9a, bringing A low, and removing power from the motor.
The timer continues to count down until T0̸ occurs, which brings B high, and starts the motor in the forward direction to open the valve assembly. Again valve travel continues until a mechanical stop is encountered, which again generates a STALL pulse. This second STALL pulse clocks the high level at B through the flip flop U9b, which latches into a condition with its Q output high. This also provides a high to the set input of U9a, which causes its Q output also to latch high. This gives a high level at both A and B, and again removes power from the motor.
The system remains in this state until power is removed, and reapplied.
The states of the A and B outputs resulting from the foregoing are as follows:

Event A B Motor

SET 0 0 Off

START

1 0 Reverse (close valve)

STALL 0 0 Off

T∅ 0 1 Forward (open valve)

STALL 1 1 Off

Claims

A downhole tool which includes an actuator apparatus for actuating said tool, which apparatus comprises mechanical actuator means (132) for actuating said tool; and drive means (134), operably associated with said mechanical actuator means, for moving said mechanical actuator means; characterised in that the actuator apparatus includes abutment means (156) for abutting said mechanical actuator means to limit movement thereof and thereby define at least one position of said mechanical actuator means; and control means (164) for controlling said drive means (134), said control means including and being responsive to a load sensing means (174) for sensing an increased load on said drive means when said mechanical actuator means abuts said abutment means.
A downhole tool according to claim 1, wherein said control means includes a timer means (176) for providing a time delay before said drive means (134) moves said mechanical actuator means (132) to actuate said tool.
A downhole tool according to claim 1 or 2, wherein said control means includes initializing means (178) for setting said timer means (176).
A downhole tool according to claim 3, wherein said initializing means (178) is a means for setting said timer means upon assembly of said apparatus.
A downhole tool according to claim 3 or 4, wherein said drive means (134) is an electric motor drive means; and said apparatus further includes an electric power supply (168); and said initializing means (178) is a means for setting said timer means upon connection of said electric power supply to said control means.
A downhole tool according to claim 5, wherein said abutment means includes first (156) and second (162) abutments for defining an unactuated position and an actuated position of said tool, upon abutment of said mechanical actuator means with said first and second abutments, respectively; and said control means further includes first start-up means (180) for starting said electric motor drive means (132) running in a first direction to move said mechanical actuator means (132) toward said first abutment (156) upon connection of said power supply (168) to said control means (164), and first shut-down means (182) for shutting off said electric motor drive means in response to a signal from said load sensing means (174) indicating that said mechanical actuator means has abutted said first abutment.
A downhole tool according to claim 6, wherein said control means includes second start-up means (184) for starting said electric motor drive means running in a second direction to move said mechanical actuator drive means (132) toward said second abutment (162) and thereby actuate an operating element after said time delay has elapsed.
A downhole tool according to claim 7, wherein said control means includes second shut-down means (186) for shutting off said electric motor drive means in response to a signal from said load sensing means (174), indicating that said mechanical actuator means (132) has abutted said second abutment (162).
A downhole tool according to claim 5, 6, 7 or 8, wherein said apparatus can be reset by disconnecting said electric power supply (168) from said control means (164) and then reconnecting said electric power supply to said control means.
A downhole tool as claimed in any of claims 1 to 9, which tool is a downhole shut-in valve tool.