GB2280013A

GB2280013A - Trigger module for explosive actuator

Info

Publication number: GB2280013A
Application number: GB9413856A
Authority: GB
Inventors: Simon Benedict Fraser; Glenn Weldan Holcombe
Original assignee: Individual
Current assignee: Individual
Priority date: 1993-07-13
Filing date: 1994-07-08
Publication date: 1995-01-18
Anticipated expiration: 2014-07-08
Also published as: GB9314464D0; GB2280013B; GB9413856D0

Abstract

A trigger module is assembled with an explosive actuator (11) which form an assembly which is lowered to a required depth at which remote operation of the actuator is required e.g. lowered down a borehole to perforate the tubing (12), in which the module comprises means for attaching the module to a cable e.g. a slickline (13) to permit the module to be lowered to the required depth, a monitoring device (17) provided in the module to monitor a predetermined parameter e.g. fluid pressure or temperature prevailing in the region of the module, and responding to a predetermined change or value of the measured parameter in order to issue a monitoring signal, a trigger device (18) which responds to receipt of the monitoring signal and which issues a trigger signal to initiate operation of the actuator, and a battery operated electronics package (19) in the module which controls the operation of the monitoring device and the trigger device. <IMAGE>

Description

TRIGGER MODULE This invention relates to a trigger module for use with an associated actuator which together form an assembly which is lowerable e.g. via a cable to a required depth at which remote operation of the actuator is required e.g. a required depth down a borehole, in which the module is operable in response to a predetermined change or predetermined value of a measured parameter prevailing at the required depth.

The invention has been developed primarily (though not exclusively) in connection with a trigger module for detonating an explosive device, and which has particular application to a production installation for extracting underground liquid and / or gaseous hydrocarbons. However, it should be understood that, while this is a particularly preferred application of the invention, the trigger module of the invention may be employed in other technological fields where it is require to initiate operation of a remote device.

In the extraction of hydrocarbons, it is usual to provide production tubing which conveys the hydrocarbons from an underground reservoir to a surface installation, but when it is required to "kill" the well, it is normal practice to "blow" holes in the production tubing using explosive charges, and which thereby provide communication between the tubing and casing annulus so that a heavy "kill" fluid can be supplied to provide overbalance on the producing formation thereby killing the well.

This is usually done prior to removing the production tubing for maintenance purposes, or for safety reasons or other operations.

One existing method to detonate the explosive device (typically comprising 10 to 20 charges) uses'electric line (7 3/32 inch cable) which has an inner conductor, braided inner wire core and braided outer wire, and which line is used to lower the explosive device down the production tubing until the required level is reached, and then an electric charge from the surface is transmitted down the line to detonate the charges.

This method is the industry standard, but is expensive and time-consuming, and also requires great care to be taken owing to the nature of the equipment which is involved. There is a risk of premature firing of the charges, by reason of the line being struck by lightning (which can occur especially in a marine environment), and also because the line may act as an aerial for stray radiowaves, and therefore radio silence is necessary. There is also operational difficulty of ensuring that the explosive device is properly lowered to the required position.

An alternative method uses so-called "slickline" wire (which is not electrically insulated) to lower an explosive package to the required position, and in which the package includes a trigger mechanism having a timer and a trembler switch to detect vibration and hence motion. A pre-set time is set on the timer, which operates in conjunction with a signal from the trembler when motion ceases, in order to fire the charge. However, this method is unreliable, since it is possible for the package to become snagged while it is being run down the hole, whereby time is lost and a spurious signal for cessation of motion may be issued by the trembler switch, thereby causing the explosive charges to be fired prematurely and at the wrong position i.e. a higher position in the production tubing than is required.

The invention therefore seeks to provide an improved trigger module for initiating operation of a remote device (such as an explosive device lowered down a borehole), and which is operable in response to a predetermined change of a parameter sensed or monitored by the trigger module, so as (1) to provide more reliable triggering of the remote device and (2) which does not rely upon an electrical signal line running from a remote operating station to the trigger module to enable remote triggering of the module by an electrical signal, as occurs in known arrangements.

According to one aspect of the invention there is provided a trigger module for use with an associated actuator which together form an assembly which is lowerable to a required depth at which remote operation of the actuator is required, said module comprising: means for attaching the module to a cable to permit the module to be lowered to the required depth; a monitoring device provided in the module to monitor a predetermined parameter prevailing in the region of the module, and responsive to a predetermined change or value of the measured parameter so as to issue a monitoring signal; -a trigger device provided in the module and arranged to respond to receipt of the monitoring signal, said trigger device being operative thereafter to issue a trigger signal to initiate operation of the actuator; and, a battery-operable electronics package in the module arranged to be energised by an electrical battery pack when the latter is mounted in the module, said package being operable to control the operation of the monitoring device and the trigger device.

According to a further aspect of the invention there is provided a method of initiating a triggering action at a required depth, using a trigger module and an associated actuator which together form an assembly, said module comprising means for attaching the module to a cable, to permit the module to be lowered to the required depth, a monitoring device provided in the module to monitor a predetermined parameter prevailing in the region of the module, and responsive to a predetermined change or value of the measured parameter so as to issue a monitoring signal, and a trigger device provided in the module and arranged to respond to receipt of the monitoring signal and being operative thereafter to issue a trigger signal to initiate operation of the actuator, and the method comprising:: lowering the assembly to a required depth at which remote operation of the actuator is required; monitoring the predetermined parameter prevailing in the region of the module, and responding to a predetermined change or value of the measured parameter when the required depth is reached, so as to issue a monitoring signal; and, supplying the monitoring signal to the trigger device and causing the trigger device to issue a trigger signal which initiates operation of the actuator.

The monitoring device may be arranged to monitor one or more of any convenient prevailing parameter in the region of the module e.g. fluid pressure and / or temperature of the surrounding medium, and this enables the module to be lowered to a required depth e.g. down a borehole at which the predetermined change, or predetermined value of the measured parameter may be used to indicate (a) that the required depth has been reached and (b) thereafter to initiate operation of the actuator of the assembly (module plus actuator).

In one preferred application of the invention, the actuator may comprise an explosive charge. having an electrically energisable detonator, in which case the trigger signal issued by the trigger device will be an electrical signal of sufficient strength to trigger the detonator which, in turn, will set off the explosive charge(s).

When the assembly is used to "kill" a well (which is one particularly preferred application), the assembly is lowered by a suitable cable e.g. a "slickline" which does not need to convey any electrical current, and therefore can be designed purely with tensile load in mind, and the cable lowers the assembly to the required depth at which the monitoring device responds to the prevailing parameter to indicate the depth has been reached, and this sets in train a sequence of events which results in perforation of the tubing by the explosive charge(s) at this region, and followed by usual application of "kill fluid".

As an alternative to use of the assembly as a "perforating gun" or "tubing punch", in which the assembly may be conveyed to the bottom of the borehole on a single strand wire (slickline) which is normally .108 inch diameter in order to "blow" holes in the production tubing, there are other preferred applications of the assembly as discussed below.

Tubing / casing cutter A large explosive charge may be conveyed to a set point in the borehole, in order that the exploding charge can separate the pipe or tubing. This becomes necessary when the pipe or tubing becomes stuck fast, and normal means of recovery fail to dislodge the pipe or tubing. Present methods involve use of electric wireline to convey an explosive charge to the required region, and then trigger explosion of the charge via an electrical signal sent down the wireline. The trigger module of the invention, conveyed via slickline, is an advantageous alternative to this existing technique.

Packer / bridge plug setting tool A packer is a device for isolating the production tubing from the annulus with the casing at the bottom of the wellbore.

This prevents well pressure migrating up the annulus. Bridge plugs are a means of isolating pressure across a wellbore.

Both devices (packers and bridge plugs) in use have large elastomeric sealing rings and metal "slips" which grip the tubing or casing when energised. Some of these devices require a small explosive charge to set them. Again, tis is presently being carried out by use of an electric line. Another method of setting currently in use is by conveying an hydraulic set device on the end of a pipe and using pressure to energise it.

The trigger module of the invention is an advantageous alternative to existing techniques for this also.

Coiled tubing conveyed perforating / setting systems Newly developing technology being developed for use in the North Sea and other hydrocarbon extraction zones use coiled tubing as a means of drilling, side tracking and completing wells, and especially horizontal wells. Drilling and production pipes are normally approximately 30 foot long and are screwed together. By contrast, coiled tubing may be many thousands of feet long and coiled or spooled onto a large drum.

The diameter of coiled tubing is relative small, (typically one inch to two and seven eights inch), so as to be capable of being spooled onto a drum, and when used in conjunction with a drilling motor (the pipe does not rotate but high pressure mud is pumped down the tube to power a drill) and with a small bore directional or horizontal drill can be drilled relative cheaply. A drilling rig is not require for this.

The same coiled tubing may be used to complete or case a well instead of production tubing or casing. Coiled tubing may also be used to convey tools to the end of a horizontal section of a wellbore by "pushing" from the surface.

Conventional perforating techniques using the "electric wireline" discussed above may be utilised for this purpose, but this requires a special coiled tubing with an electric wireline fitted to the inside of the tubing, which is both expensive and clumsy. Also, because of the very small diameters of the tubing in a coiled tubing arrangement, most if not all conventional setting, perforating and cutting tools will not be able to be taken along the small diameter passages defined by the coiled tubing.

If perforation is required after the well casing has been cemented in place and the production tubing and packer has been set, holes are blown through the casing by explosives adjacent to the production formation to allow the well to be "brought in".

It is envisaged that the trigger module of the invention may be adapted for this use also, with technical advantage, by being screwed or otherwise attached to the bottom of the coiled tubing.

Perforating for production Again, it can be desirable to use explosive charges to blow holes in a casing or tubing as described above. Present systems used comprise the electric line conveyed system discussed above, and also so-called "perforating guns" conveyed via tubing. The trigger module according to the invention may be used as an alternative, in conjunction with a reliable means of depth correlation.

Mudline recovery When it is required to abandon an off-shore well, explosive blasting of the tubing I casings below the mudline takes place. The wellhead or other subsea equipment is recovered following the severance of the well tubulars. This is presently carried out using the electric wireline conveyed system. The trigger module of the invention is an advantageous alternative to this, using a slickline to convey the trigger module and explosive actuator.

Platform abandonment Platforms having steel jackets can be separated from their supporting legs by use of explosive charges, prior to toppling or removal of the platform components. It is envisaged that the trigger module and explosive actuator according to the invention, conveyed via a slickline, may be used for this also.

The prevailing parameter which is monitored in the bore hole e.g. within production tubing, or along any other passage through which the trigger module is taken, may comprise gas pressure, liquid pressure, and / or temperature, and the value of the measured parameter may change as the module moves to progressively lower depths. However, this is not essential to the invention, and controlled application of pressure to a fluid column may take place e.g. from a surface installation, to generate a pressure signal which can be monitored by the monitoring device, and then set in train the initiation of the actuator.This is a particularly advantageous way of enabling control of the operation of the module to be exercised remotely, by an operator at a time and / or depth of his choosing during descent of the module, without need for any electrical signals to be transferred to the module.

The module will normally be provided with its own battery pack, so that it is self operated electrically, without need for any external power supply.

A preferred embodiment of the invention will now be described in detail, by way of example only, with reference to the accompanying schematic drawings, in which: Figure 1 shows a trigger module according to the invention being lowered down a borehole within production tubing, and coupled with an associated explosive actuator which is to be positioned at a required depth and then triggered to explode by the module; Figure 2 is a block circuit diagram of the electronic components of the module; Figure 3 shows schematically the operating components of the monitoring device of the module; and Figure 4 is a graph of pressure sequence against time with tolerances for each parameter.

Referring first to Figure 1 of the drawings, a trigger module according to the invention is designated generally by reference 10 and is intended for use with an associated actuator 11, which is closely coupled therewith, or indeed incorporated within the overall module, and which comprises a set of explosive charges and electrically energisable detonators. The module 10 and explosive actuator 11 form together an assembly which is lowerable down a borehole to a required depth at which remote operation of the explosive actuator 11 is required. Figure 1 shows the assembly being lowered within production tubing 12 via a slickline 13 which will normally be readily available and which is a type of carrying line which is not required to convey electrical current, and therefore is designed solely for tensile load purposes.

It should be understood that lowering of the module to a required depth in a borehole is only one example of use of the module of the invention, and which may be lowered to required depth in other environments e.g. down a mineshaft, or from a surface location to a required height above the seabed, or to the seabed itself.

However, going back to use in a borehole, the assembly may perforate the tubing 12 with explosive charges so that communication can be established between the production tubing 12 and annulus 14 with in casing 15, so that the tubing contents can be displaced with a heavy "kill" fluid to provide overbalance on the production formation, thereby "killing" the well.

The methods currently used to kill a well have been described above and the trigger module according to the invention provides more reliable triggering of the explosive charge (which forms a remote device) and which does not rely upon an electrical signal line running to the trigger module from the surface to trigger its operation.

The module 10 has any suitable attaching means (shown schematically only by reference 16), to enable the module to be attached to slickline 13, and this can comprise any standard type of "rope socket". This enables the module 10 and explosive actuator 11 to be lowered to a required depth down the borehole.

The module includes a monitoring device 17 which monitors a predetermined parameter prevailing in the bore hole e.g.

fluid pressure and / or temperature, and is arranged to respond to a predetermined change, or predetermined value of the measured parameter, so as to issue a monitoring signal.

The module also includes a trigger device shown schematically by reference 18, and which responds to receipt of the monitoring signal from the monitoring device 17, so as then to be operative thereafter to issue a trigger signal to initiate operation of the explosive actuator 11.

A battery-operable electronics package 19 is also arranged in the module 10 to be energised by an electrical battery pack when the latter is mounted in the module, the package 19 being operable to control electrically the operation of the monitoring device 17 and the trigger device 18.

The monitoring device 17 can monitor any one or more of any convenient prevailing parameters in the borehole e.g. fluid pressure and ! or temperature, and this enables the module to be lowered to required depth at which predetermined change, or predetermined value of the measured parameter may be used to indicate (a) that the required depth has been reached and (b) thereafter to initiate operation of the explosive actuator 11.

It should be understood that figure 1 is a schematic illustration only, and the monitoring device 17 will be provided with any suitable electrically operated monitoring devices able to monitor the prevailing parameters adjacent thereto as the module descends down the borehole, and which can issue an appropriate monitoring signal. The trigger device 18 then responds to receipt of the monitoring signal and issues a trigger signal which conveys a required level of electrical power to the detonator at the head of the explosive actuator 11.

Figure 2 shows a block circuit diagram of the internal arrangement of the components 17, 18 and 19 of the module 10.

The components comprise a microcontroller 25 which runs a machine code programme contained in programme memory device 27. This programme causes the pressure and temperature to be measured at intervals, based on time derived from a crystal oscillator 26, using analogue to digital converter 29 and pressure sensor 30 and temperature sensor 31.

The programme will also allow the microcontroller 25 to execute time delays by means of counting time from the crystal oscillator 26. The operator will set-up with operating parameters in a manner which will be described below. The parameters will be stored in a non-volatile data memory 28.

The means for entering the parameters will be via the communications interface 35. At such time as the programme determines that the detonator should be fired, a high voltage generator 32 will be used to step-up the voltage from battery 34 to the level required. By way of example, the voltage stepup could be from 7 volts to 100 volts. When the required voltage is achieved, the microcontroller 25 will employ electronic switch 33 to apply the voltage via output 36 to electrically energise the detonators in the explosive actuator.

Methods in which the apparatus may be used will now be described, by way of example only.

Method A - Timer activation with pressure plus temperature lock-out.

A borehole will normally be filled with a fluid, and the approximate depth can be judged by measuring the static pressure at a particular point. For deep boreholes a temperature gradient will also be observed, whereby the deeper the hole, the greater will be the temperature. With some small local knowledge of the area in which a particular borehole is located, it is possible to estimate the pressure and temperature at any particular depth. The trigger module is capable of measuring these parameters, and therefore can determine the approximate depth of the equipment at any particular point. In addition, a mechanical pressure switch within the module will be set to operate at just below the pressure for the required depth, and a mechanical temperature switch in the module will be selected to operate at just below the expected temperature.

The operator will then set-up a number of parameters as follows: 1. Time delay.

2. Temperature threshold.

3. Pressure threshold.

When the electronics section is activated, the controller 25 will first wait until the time delay has elapsed, and then start to measure the temperature periodically. When the required temperature threshold has been exceeded, the controller 25 will start to measure the pressure periodically.

When the required pressure threshold has been exceeded, the controller will operate high voltage circuitry which charges a bank of capacitors (not shown in detail) to 100 volts. When the voltage is reached, the controller 25 will close an electronic firing switch. This will place 100 volts across the detonator only if both mechanical pressure and temperature switches have already operated. If either the pressure switch or the temperature switch has not - been operated, then a short circuit will be presented to the capacitor bank, and the voltage will be discharged immediately without energising of the detonator.

Method B - Timer plus pressure plus temperature lock-out with surface pressure triggering.

The trigger module according to the invention does not need to be triggered into operation solely as a result of monitoring change of parameters as the module descends down the borehole, but can be arranged to be remotely operated (without use of electrical signals to the module) by remote influence on the parameters to which the module is exposed. This can be carried out by applying pressure to fluid in the borehole by remote operation, whereby the monitoring device of the module can respond to this change in pressure, and then trigger operation of the explosive actuator.

To carry this out, it is necessary to seal the borehole effectively at the surface, in such a way that an over-pressure can be applied at the surface using a pump.

The various steps of method A, described above, will be performed, but an additional condition for firming will be the detection of a pressure signal. This pressure signal could be, for example, a pulse of 500 psi height and 30 second duration.

The operator will set the parameters within the controller 25 to determine the size and duration thought necessary. This pressure sequence may be extended to comprise multiple pressure pulses of various heights and durations as necessary, to allow the remote application of pressure parameter variations to trigger operation of the module.

Figure 4 shows schematically a typical pressure pattern with tolerances for each parameter.

The preferred mode of lowering the trigger module to a required depth at which triggering of operation of the actuator coupled therewith is a slickline, but evidently many other types of means may be adopted in order to lower the module to a particular depth. The module may be carried on the end of a tool, tubing or any other component typically lowered down boreholes.

Claims

1. A trigger module for use with an associated actuator which together form an assembly which is lowerable to a required depth at which remote operation of the actuator is required, said module comprising: means for attaching the module to a cable to permit the module to be lowered to the required depth; a monitoring device provided in the module to monitor a predetermined parameter prevailing in the region of the module, and responsive to a predetermined change oI value of the measured parameter so as to issue a monitoring signal; a trigger device provided in the module and arranged to respond to receipt of the monitoring signal, said trigger device being operative thereafter to issue a trigger signal to initiate operation of the actuator; and, a battery-operable electronics package in the module arranged to be energised by an electrical battery pack when the latter is mounted in the module, said package being operable to control the operation of the monitoring device and the trigger device.

2. A module according to Claim 1, in which the monitoring device is arranged to monitor more than one prevailing parameter.

3. A module according to Claim 1 or 2, in which the monitoring device is arranged to monitor one or more of fluid pressure and / or temperature of the surroundiny medium.

4. A module according to any one of Claims 1 to 3, in which the monitoring device is arranged to respond to said predetermined change, or predetermined value of the measured parameter, in order to indicate (a) that the required depth has been reached and (b) thereafter to initiate operation of the actuator.

5. A module according to any one of Claims 1 to 4 and in combination with said actuator.

6. A module according to Claim 5, in which said actuator comprises an explosive charge having an electrically energisable detonator, and in which the trigger signal issued by the trigger device is an electrical signal of sufficient strength to trigger the detonator, which, in turn, will set off the explosive charge(s).

7. A module according to Claim 4, in which the actuator comprises an explosive charge and arranged in such a way that the module can form a tubing / casing cutter.

8. A module according to Claim 4, in which the actuator includes an explosive charge, and in combination with a packer for isolating production tubing from the annul us with the casing at the bottom of a wellbore, said actuator being operable to set said packer into operation.

9. A method of initiating a triggering action at a required depth, using a trigger module and an associated actuator which together form an assembly, said module comprising means for attaching the module to a cable, to permit the module to be lowered to the required depth, a monitoring device provided in the module to monitor a predetermined parameter prevailing in the region of the module, and responsive to a predetermined change or value of the measured parameter so as to issue a monitoring signal, and a trigger device provided in the module and arranged to respond to receipt of the monitoring signal and being operative thereafter to issue a trigger signal to initiate operation of the actuator, and the method comprising:: lowering the assembly to a required depth at which remote operation of the actuator is required; monitoring the predetermined parameter prevailing in the region of the module, and responding to a predetermined change or value of the measured parameter when the required depth is reached, so as to issue a monitoring signal; and, supplying the monitoring signal to the trigger device and causing the trigger device to issue a trigger signal which initiates operation of the actuator.

10. A method according to Claim 9, in which the trigger module is lowered down a borehole to a required depth at which remote operation of the actuator is required.

11. A method according to Claim 9 or 10, in which the actuator includes an explosive charge having an electrically energisable detonator, and issuing an electrical trigger signal from the trigger device which triggers the detonator which, in turn, sets off the explosive charge.

12. A method according to any one of Claims 9 to 11, in which the assembly is used to kill a well, and is lowered by a cable which is not capable of conveying any electrical current, and which lowers the assembly to the required depth at which the monitoring device responds to the prevailing parameter to indicate the depth has been reached, and which then sets in train a sequence of events which results in perforation of the tubing by the explosive charge at this region, and followed by application of kill fluid.

13. A method according to Claim 9, in which the actuator include a large explosive charge which is conveyed to a set point in the borehole, and which is then triggered to explode and to separate the pipe or tubing, whereby the assembly operates as a tubing / casing cutter.

14. A method according to Claim 9, in which a packer / bridge plug setting tool is coupled with the assembly, and the actuator includes an explosive charge, and comprising lowering the assembly and the tool to a required depth, and triggering operation of the actuator to set the operation of the packer / bridge plus setting tool.

15. A method according to Claim 9, in which the module is conveyed along coiled tubing of a conveyed perforating / setting system.

16. A method according to Claim 9, in which the trigger module is screwed or otherwise attached to the bottom of coiled tubing, and is conveyed thereby to a required depth if perforation is required after a well casing has been cemented in place and the production tubing and packer have been set, in order to blow holes through the casing by explosives adjacent to the production formation to allow the well to be "broughtin".

17. A method according to Claim 9 and used in mud line recovery.

18. A method according to Claim 17, in which the well tubulars are severed during abandonment of an off-shore well, comprising lowering the assembly to required depth, and then triggering explosive operation of the actuator to severe the well tubulars.

19. A method according to Claim 9, and used during platform abandonment.