CASING VALVE Ths invention rebates to a safety meoharn.m such as a vaLve, sleeve, packer 5 or plug, for a well; a well comprising the safety mechanism; and methods to improve the safety of wels; partioulardy but not excluaively subsea hydrocarbon wells. in recent years, oi and gas has been recovered'from subsea wells in very 0 deep water, of the order of over 1km. This poses many technical problems in drilling, securing, extracting and abandoning wells in such depths, In the event of a failure in the integrity otf the well, wellhead apparatus control systems are known to shut the well off to prevent dangerous blow-out, or i5 significant hydrocarbon loss from the well Blow-oupreventers (BOPs) are situated at the top of subsea wels, at the seabed, and can be activated from a control room to shut the well, or may be adapted to detect a blow-out and shut automatically, Should this fail, a remotely operated vehicle (ROV) can directly activate the BOP at the seabed to shut the well. in a completed well, rather than a SOP, a "Christma" tree is provided at the top of the well and a subsurface sfyvave (SSV) is normally added, "downhole" in the well. The SSV is nomialiy activated to close and shut the well if it loses communication with the controlling platform, rig or vessel 25 Despite these known safety controls, accidents still occur and a recent example is the disastrous biow-out from such a subsea well in the Gulf of Mexico, causing a massive explosion resulting in loss of life, loss of the rig and a significant and sustained escape of oi into the Gulf of Mexico, threatening wildlife and marine industries. Whilst the specific causes of the disaster are, at presen, unclear, some $ aspects can be observed: an Emergency Dis-connect System (EDS) controlled from the rig failed to seal and disconnect the vessel rorn the well: a ad-nan/AMF system at the seabed failed to seai th well subsequent Remotely Operated Vehicle (ROV) intervenion also failed to activate the safety mechanirms on the BOP, Clearly the conventional systems focused 10 prinarily on the biow-ouhoreventer did not activate at the time of the blow-out and also failed to stern the tide cf oli into the sea. after control communication was lost with the rig. Thus there is a need to improve the safety of oil wells especially those 15 situated in deep water regions, Given the difficulty inommunitng and controlling downhole tools (that is tools in the wel), especiasiy where communications are severed, one might consider the provision of a further shut off mechanism with the BOP situated 20 at the seabed However the inventors of the present invention have noted that the addition of more equipment at this point will be extremely difficult because it will increase the size and height of the components placed at trhs point, which immediately prior to installation, will be difficult for ngs to accommodate, Moreover. whilst this would add a further protective measure, 2$ it is largely the same concept as the existing safety systems, indeed, increasing the complexity of the control systems to support these additional features may potentialy have a detrimental impact on reliability of the over-il system rather than increasing the level of safety provided, In the case of adding a further conventional control mechanism for devices, such as a valve, or sensor downhole; the inventors of the present invention also note lirttions since, 4n the event of a bkcow-out, the ability to function 5 these devices nay be lost due to the inability to fluctuate pressure to control pressure activated devices, or due to the loss of control lines, Thus it is difficult for a skled person to design a further safety system which can practically add to the safety systems already provided in oil weIs, tO An object of the present invention is to mitigate problems with the prior art, and preferably to improve the safety of wells. According to a first aspect of the present given tion there is provided a safety 15 mechanism comprising: an obstructing member moveable between, normally from, a first position where fluid flow is permitted, and, normally to, a second position where fluid flow is restricted a movement mechanism; 20 and a wireless receiver normally a transceiver, adapted to receive, and normally transmit a wireless sign; wherein the movement mechanism is operable to move the obstructing member from one of the first and second positions to the other of the first and second positions in response to a change in the signal being received by the 25 wireless transceiver, The obstructing member can in certain embodiments therefore start at either u e first or second positions.
4 The transceiver, where it provided, is normally a single device with a receiver functionality and a transmitter functionality; but in priciple a separate receiver and a serate transmitter device may be provided These are nonteless considered to be a transceiver as described herein when the are provided together at cne ocahion Relays and repeaters may be provided to fAciliate transmisson of the wireless ignals from one location to another. The invention alsio provides a well comprising at least one safety mechaism according to the first aspect of the invention, Typically the well has a weilhead, 15 Thus the present invention provides a significant benefit in that it can move. normally shut, an obstructing member, such as a valve, packer, sleeve or plug in response to a wireless signal. Significantly this is independent of the provision of control lines, such as hydraulic or electric lines, between a well 20 and a welihead aoparatus, for example the BOP, Thus in the event of a disastrous blowout or explosion, a wireless signal can be sent to the valve merely by contacting the welihead apparatus typically at the top of the well with a wireless transmitter, which will send the appropna te signal For certain embodiments the wireless transmitter may be mounted onto the welbead 25 apparatus. indeed this can be achieved even if the wellhead apparatus nas suffered extensive damage, and/or the hydraulic, electric and other control lines have been damaged and the conventional safety systems have lost all functionality, since the wireless signal requires no intact control lines in order -5 to shut off the vaive. Thus this removes the present dependence on a funtioning BOP/weilhead apparatus to prevent the egress of oil, gas or other well fluids into the sea, 5 4n certMn embodiments the transmitter may be provided as part of a wellhead apparatus' Welihead aparatus as used herein includes but is not limited to a wellhead, tubing andor casing hanger, a BOP, wireline/coiled tubing lubricator, guide 1O base, well tree, tree frame, wel cap, dust cap and/or wel canopy, Typicaly the wellhead provides a sealing interface at the top of the borehole, Typically any piece of equipment or apparatus at or up to 20 - 30m above the wellhead can be considered for the present purposes as wellhead apparatus. 15 Said change in the signaF' can be a different signal received, or may be receiving the control signal where no control signal was previously received and may also be loss of a signal where one was previously received. Thus in the latter case the safety mechanism may be adapted to operte when 20 wireless communication is lost which may occur as a consequence of an emergency situation, rather then necessarily requiring a control signal positively sent to operate the safety mechanism, Indeed the invention more generally provides a transceiver configured to 25 activate and sand signals after an emergency situation has occurred as defined herein.
6 In pmferred embodiments the transceiver is an acoustic transceiver and the control signal is an acoustic control signal, in alternative embodiments, the transceiver may be an electromagnetic transceiver, and the signal an electromagnetic signal Combinations may be provided - for example part of 5 the distance may be travelled by an acoustic signal part by an electromagnetic signal, part by an electric cable, and/or part from a fibre optic cable: all with transceivers as necessary. The acoustic signals may be sent through elongate members or through well 10 flud, or a combination of both, To send acoustic signals through the fluid, a pressure pulser or mud poser may be used, Preferably the obstructing member moves from the first to the second position, .15 Preferaly the safety mechanism incorporates a battery. The safety mechanism is typically deployed subsea. 20 The transceiver comprises a transmitter and a receiver, The provision of a transmitter asows signals to be sent from the safety mechanism to a controller, such as acknowledgement of a control signal or confirmation of activation. 25 The safety necharrni may be provided on a drill string, completion string, casing string or any other elongate member or on a sub-assemnbly within a cased or uncased section of the weil The safety mechanism may be used in the same wells as a BOP or a welihead, tree, or well-cap and may be provided in addition to a conventional subsurface safety valve, Typical a plurality of safety mechanisms are provided, The transceiver may be spaced apart from the movement mechanism and connected by conventional means such as hydraulic line or electric cable. This allows the wireless signal to be transmitted over a smaller distance. For example the wireless signal can be transmitted from the wellhead apparatus 10 to a transceiver up to 100m, sometimes less than 50m, or less than 20m below the top of the well which is connected though hydraulics or electric cabling to the obstructing member, This allows the safety mechamm in accordance with the present invention to operate even when the wellhead, wellhead apparatus or the top 100m, 50m or 20m of the well is damaged and 15 control lines therein broken. Thus the benefits of embodiments can be focused on a particular areas, Accordingly embodiments of the present invention can be combined with fluid and/or electric control systems. Preferably a sensor is provided to detect a parameter in the well, preferably in 20 the vicinity of the safety mechanism, Thus such sensors can provide important information on the environment in all parts of the wel especially around the safety mechanism and the data trom the sensors may provide information to an operator of an emergency 25 situation that may be occurring or about to occur and may need Intervention tc mitigate the emergency situation, 8 Preferably the information is retrieved wireleasiy, although other means, such as data cables, may be used, Preferably therefore the safety mechanism comprises a wireless transmitter and more preferably a wireless transceiver. 5 The sensors may sense any parameter and so be any type of sensor including but not necessarily limited to temperature, accelieration, vibration, torque, movement, motion, cement integrity, pressure, direction and inclination, load, various tubular/casing angles, corrosion and erosion, radiation, nlIse, magnetism, sesic movements, stresses and strns on t0 tubular/casings including twisting, shearing, compressions, expansion, bucling and any form of deformation; chemical or radioactive tracer detection; fluid identification such as hydrate, wax and sand production and fluid properties such as (but not limited to) flow, density, water cut, pH and viscosity, The sensors may be imaging, mapping and/or scanning devices 15 such as, but not limited to, camera, video, infrared., magnetic reonance, acoustic, uitra-sound, electrical, optical impedance and capacitance. Furthermore the sensors may be adapted to induce the signal or parameter detected by the incorporation of suitable transmitters and mechanisms. The sensors may also sense the status of equipment within the well for 20 example valve position or motor rotation, The wireless transceiver may be incorporated within the sensor, valve or safety mechanism or may be independent from It and connected thereto. The sensors may be incorporated directly in the equipment comprising the 2$ transmitters or may transfer dota to said equipment using cables or short~ range wireless (eg. inductive) communication techniques. Short range is typically less than 5m apart, often less than 3m apart and indeed rray be Less than im apart.
9 The sensors need to operate only in an emergency situation but -an o provide detatis on different parameters at any time. The sensors can be useful for cement tests: testing pressures on either side of packers, sleeves, 5 valves or obstructions and weilhead pressure tests and generaly for well information and monitoring from any locaion in the weit The wireless signals may be sent retroactively, that is after an emergency situation has occurred, for example after a blow out, 0 Typically the sensors can store data for iater retrieval and are capable of transmitting it, The safety mechanism may be adapted to move the obstructing member to/from the first position from/to the second position automatically in response 5 to a parameter detected by the sensor. Thus at a certain "trip point" the safety mechanism can close the well, if for example, it detects a parameter indicative of unusual data or an emergency situation, Preferably the safety mechanism is adapted to function in such a manner in response to a plurality cf different parameters a;l detecting unusual data, thus suggesting an 20 emergency situation, The parameter may be any parameter detected by the sensor, such as pressure, temperature, flow, noise, or indeed the absence of flow or noise for example, Such safety mechanisms are particularly useful during all phases when a 25 SOP is in use and especially during nondriliing phases when a BOP is in Use.
10 Preferaby the trip point can be varied by sending instructions to a receiver coupled to (not necessarily physically connected thereto) or integra! with, the sensors and/or safety mechanism, Such embodiments can be of great benefit to the operator, since the different operations down hole can naturally 5 experience different parameters which may be safe in one phase but indioative of an emergency situation in another phase,. Rather than setting the trip point at the maximum safety level for all phases, they can be changed by communications including wireless communication for the different phases. For example, during a driving phase the vibration sensed would be expected 10 to be relatively high compared to other phases, Sensing vibration to the same extent in other phases may be indicative of an emergency situation and the safety mechanism instructed to change their trip point after the drilling phase. 15 For certain embodiments, a sensor is provided above and below the safety mechanisms and can thus monitor differential parameters in these positions which can in turn elicit information on the safety of the wel. In particular any pressure differential detected across an activated safety mechanism would be of particular use in assessing the safety of the wel especially on occasions 20 where a controlling surface vessel moves away for a period of time and then returns. Sensors anidior transceivers may also be provided in casing annual. 2$ In use, an operator can react t o any abnormal and potentiay dangerous occurrence which the sensors detect. This can be a variety of different parameters including pressure, temperature and also others like stress and strain on pipe s or any other m ssensors referred to herein but not limited to those, Moreover with a plurality of sensors, the data may provide a profile of the 5 parameters (for example, pressure/temperature) along the casing and so aid identification where the loss of integrity has occurred, eg. whether the casing, casing cement, float colar or seal assembly have failed to laoate the reservoir or well Such information can allow the operator to react in a quick, safe and efficient manner; alternatively the safety mechanism can be adapted 10 to activate in response to certain detected parameters or combination of parameters, especially where two or three parameters are showing unusual values. Such a system may be activated in response to an emergency situation. Thus the invention provides a method of inhibiting fluid flow from a well in an emergency situation, the method comprising: in the event of an emergency, sending a wireless signal into the wel to a safety mechanism according to the first aspect of the invention, 20 Preferred and other optonal features of the previous embodiment are preferred and options features of the method according to the invention immediately above, 25 An emergency or eriergency situation is where uncontrolled fluid flow occurs or is expected to occur, from a wel; where an unintended explosion occurs or there is an unacceptable risk that it may occur, where significant structural damage of the well integrity is occurring or there is an unacceptable risk that it may occur, or where human lie, or the environment is in danger, or there is an unacceptable risk that it maybe in danger. These dangers and risks may be caused by a number of factors, such as the well conditions, as wei as other factors, such as severe weather. Thus normally an emergency situation is one where at east one of a BOP and subsurface safety valve would be attempted to be actiated, especialv before/during or after an uncontrolled event in a welL, i Furthermore, normally an emergency situation according to the present invention is one de"ined as the least, more or most severe accordingly to the ADAC Deepwater Well Control Guidelines, Third Printi:ng including Supplement 2000, section 4.12, Thus events which relate to kick control may be regarded as an emergency situation according to the present 5 invention, and especially events relating to an underground blowout are regarded as an emergency situation according to the present invention, and even more especially events relating to a loss of control of the well at the sea floor (if a subsea well) or the surface is even more especially an emergency according to the present invention, 20 Methods in accordance with the present invention may also be conducted after said emergency and so may be performed in response thereto, acting retroactively, 25 The method may be provided during all stages of the drilling, cementing, development: completion, operation, suspension and abandonment of the well. Preferably the method is provided during a phase where a BOP is provided on the welit Optionally the method 4s conducted during operations on the well when attempts have been made to activate the BOP. During these phases, embodiments of the present invention are particularly 5 useful because the provision of physical control lines during these phases would obstruct the many well operations occurring at this tIme; and indeed the accepted practice is to avoid as much as possible installog devices which require communction for this reason, Embodiments of the present invention go against this pracice and overcome the disadvantages by providing 10 wireless cormunicaions. Thus an advantage of embodiments of this invention is that they enable the use of a safety valve or barrier in situations where conventional safety valves or barriers could not, or would not, normally be deployed. 1s The safety mechanism may comprise a valve, preferably a balj or flapper valve, preferably the valve may incorporate a mechanical over-ide controlled, for example, by pressure, wireline, or colled tubing or other intervention methods, The valve may incorporate a 'pump through' facility to permit flow in one direction, 20 The obstructing member of the safety mechanism may be a sleeve, Optionally the safety mechanism may be actuated directly using a motr. but alternatively or additionally may be adapted to actuate using stored pressure, 25 or preferably using well pressure acting against an atmospheric chamber, optionally used in conjunction with a spring actuator.
14 The safety mechanism may incorporate components which are replaceable, or incorporate key partS, such as bateies, or valve bodies which are replaceable without removing the whole component from the well, This can be achieved using methods such as side-pockets or replaceable inserts, 5 using conventional methods such as wireline or ciledhing, In order to retrieve data from the sensors and/or actuated the safety mechanism, one option is to deploy a probe, A variety of means ray be used to deploy the probe, such as an electric line, slick ine wire, coiled I0 tubing, pipe or any other elongate member. Such a probe couid alternatively or addtionaliy be adapted to send signals, Indeed such a probe may be deployed into a casing annulus if required, In other embodiments, the wireless signal may be sent from a device 15 provided at the welihead apparatus or proximate thereto, that is normally within 300m. In one embodiment wireless signals can be sent from a platform, optionally with wireless repeaters provided on risers and/cr downhole, For other embodiments, the wireless signals can be set from the seabed welInead apparatus, after receiving sonar signals from the surface or 20 from an ROV, in other embodiments, the wireless signals can be sent from the wellhead apparatus after receiving a satellite signals from another location, Furthermore if the wellhead is a seabed wellhead, the wirrcess signals can be then sent from the seabed wellhead apparatus, after receiving sonar signals, which had been triggeredactivated after receiving a satellite 25 signal from another location, The surface or surface facility may be for exarnple a nearby production facility standby or supply vessel or a buoy.
15 Thus the device comprises a wtreiess transmitter, or transceiver and preferably also comprises a sonar receiver, to receive signals from a surace facility and especially a sonar transceiver so that tan communicate two-va S with the surface facility. For certain embodiments an electric line may be run inrc a wel and the wirel transCiver atached towards one end of the line, In other embodiments the signal may be sent from an ROV vi a hot-stab connection or via a sonar signal frorn the ROV, ) Therefore the invention also provides a device, in use fitted or retro-fitted to a top of a wel, comprising a wireless transmitter and a sonar receiver; especially for use in an emergency situation, The device is relatively smali, typically being less than 1m, preferably less 5 than 0,25 m, especially less that 0.10 rmaand so can be easy handed on the wellhead apparatus. The resulting physical contact between the wellhead apparatus and the device provides a connection to the well for transmission of the wireless signal. In alternative embodiments the device is built into the wellhead apparatus, which is often at the seabed but may be on land for a 20 land well Thus such devices also operate tirelessly and do not require physical communication between the wellhead apparatus and a controlling station, such as a vessel or ng, 25 Embodiments of the invention also include a satellite device comprsing a sanar transceiver and a saellite communication device, Such embodiments can communicate with the well, such as with said device at the wellhead 16 apparatus in accordance with a previous aspect of the invention, and relay signals onwards via sateite. The sateite device may be provided on a r or vessel or a buoy. 5 Thus according to one aspect of the invention there is provided a welH apparatus comprising a well and a satellite device comprising a satellite communication mechanism, and a sonar, the device configured to relay information received from the sonar by satellite, W0 Preferably the device is independent of the rig, for exa rnpie it may be provided on a buoy, Thus in the event that the rig is lost, the buoy may relay a control signal from a satellite to the well to shut down the wel In a further embodiment the device at the wellhead apparatus smay be wired 1 S to a surface or remote facility, Preferably however, the device is provided with further wireless communication options for communication with the surface facility. Typically the device has batteries to permit operation in the event of damage to the cable, 20 The safety mechanism may comprise a subsurface safety valve, optionally of known type, along with a wireless transceiver, In alternative embordiments, the safety mechanism comprises a packer and an expansion mechanism, The movement mechanism causes the expansion 25 mechanism to activate which expands the packer and so moving the packer from said first position to said second position.
1 7 Thus according to a further aspect of the present invention there is provided a packer apparatus comprising a packer and an activation mechanism, the activation mechanism comprising an expansion mechanism for expanding the packer and a wireless transceiver adapted to receive a wireless control signal S and control the activation mechanism. The wireless signal is preferably an acoustic signal and may travel through elongate members and/or weIl fluid, 10 Aiternatively the wireiess signal may be an r etcor any other wireless signal or any combination of that and acoustic, References throughout to "expanding" and "expansion mechanisms" etc include expanding a packer by compression of an elastomerio element and/or 15 inflating a packer and inflation mechanisms etc and/or explosive actvation with explosive mechanisms, or actuation of a swell mechanism by exposure of a sweilable ernlent to an activating fluid, such as water or oit The packer apparatis may be provided downhole in any suitable location, 20 such as on a dril string or production tubing and, surprisingy, in a casing annulus between two different casing strings, or between the casing and formation or on a sub-assembly within a cased or uncased secton of the well In use after deployment and wireless activation downhola according to the 25 present invention, the packer may be provided in the expanded state to provide a further barrier against fluid movement therepast, espeoialy those provided on an outer face of an eongate mernber in a weil Those between said casig end a drill string/production tubing, are preferably reactive to an emergency situation that is unexpanded. Thus the invention also provides a well apparatus comprising: S a purality of casing strings; a packer apparatus provided on one of the casing stNrIngs the packer apparatus comprising a wireless transceiver, and adapted to expand in response to a change in a wireless signal in order to restrict flow of fluid through an annuus between said casing string and an adjacent 0 ciongate member, As noted above, the packer may be provided in use in the expanded configuration and act as a permanent barrier to resists fluid flow or may be provided in the unexpanded configuration and activated as required, for 15 example in re sponse to an emergency situation. Moreover the packer may be adapted to move from an expanded configuration, corresponding to the second position of the safety mechanism where fluid flow is restricted (normally blocked) and retract to the first position where fluid flow is permitted. 20 The adjacent elongate member may be another of the casing strings or may be a drili pipe or may be production tubing. The invention aiso provides a packer as described herein for use on a 25 production string in an emergency situation. For example in a gas lift operation the packer may be provided on the production tubing and aotivated only in the event of an emergency, Typically the packer is provided as a permanent barber when the adjacent member is another casing string, and in the unexpanded configuration when the elongate member is a dri pipe of production tubing that is they remain 5 unexpanded until they expand in response to an emergency situation Whist the packer of the packer apparatus may expand in an inward or outward direction, preferably it is adapted to expand in an inward direction, 10 The annulus may be a casing annuus, Thus an advantage of Such embodiments is that fILd flow through an annulus can be inhibited, preferably stopped, by provision Of such a packer in an annulus. Normally fluid does not flow through the casing annulus of a well 1$ and so the skilled person would not consider placinga packer in t position. However the inventors of the present invention have realised that the casing anniulus is a flow path through which well fluid may flow in the event of a well failure and blow out Such an event may be due to failure of the fommation, cement andfor seals provided wih the casing system and weihead, 20 Preferably a plurality of packer apparatus are provided. Different packer apparatus may be provided in the same or in different annual, Preferably the packer apparatus islare provided proximate to the top of the 25 wei in this way the packers can typically inhibit fluid flow above the fault or suspected fault, in the casing, Therefore the packer(s) may be provided within I 00m of the wellhead, more preferably within 50m, especially within 20m, and ideally within 10m, 20) The packers provIded in a casing annulus may be non-weight packers, that is they do not necessary have engaging teeth for exam ple the packers may be inflatable or sweil types. The casing packers may be installed above the cemented-in section of the casing and they thus typically provide an additional barrier to flow of fluids above that traditionally provided by a portion of the wel being cased in, 0 In alternative embodiments the packers may be provided on an inner side of the casing adjacent to a cemented in portion of the casing, thus inhibiting a flow path at this point, whilst the cement inhibits the flow path on the outside portion of the casing. 15 The safety mechanism may be a packer-like element without a through bore and so in effect function as a well plug or bridge plug, In certain embodiments, the packer may be provided on a dril strng, 20 Thus the invention provides a method of drilling, comprising during a drilling phase providing a dr!ii string comprising a packer apparatus as defined herein, As dril strings typically rotate and move vertically in a well during a drilling 25 phase, a skilled person would not be minded to provide a packer thereon since a packer resists movement, However the inventors of the present invention note that a packer provided thereof can be used in an emergency situation and so provides advantages, 21 Thus the packer may be provided on drill string, production string, production sb-assembly and may operate in cased or uncased sections of the well, 5 The safety mechanisms and packers described herein may also have additional means of operation such as hydraulic and/or electric lines, Thus the preseAnt invention also provides a method ofdepioying a safety mechanism according to the present invention, monitoring the well using data 10 received from sensors as described herein associated wit the safety mechanism whilst abandoning the weil and/or cementing the wel and/or suspending the well. Unless otherwise stated methods and mechanisms of various aspects of the I S present invention may be used in all phases including drilng, suspension, production/injection, completion and/or abandonment of well operations. The wireless signal for alt embodiments is preferably an acoustic signal although may be an electromagnetic or any other signal or combination of 20 signals. Preferably the acoustic cormmunicalons include Frequency Shift Keying ((FSK) and/or Phase Shift Keying (PSK) modulation methods, and/or more advanced derivatives of these methods. such as Quadrature Phase Shift 25 Keying (QPSK) or Quadrature Amplitude Modulation (QAM), and preferably incorporating Spread Spectrum Techniques, Typically they are adapted to automatically tune acoustic signalling frequencies and methods to suit well conditions Embodiments of the present ivention may be used for onshore wells as well as offshore wells. S An advantage of certain embodiments is that the acoustic signals can travel up and down different strings and can move from one string to another. Thus linear travel of the signal is not required. Direct route devices thus can be lost and a signal can still successfully be received indirectly. The signal can also be combined with other wired and wireless communication systems and 0 signals and does not have to travel the whole distance acoustically, Any aspect or embodiment of the present invention can be combined with any other aspect of embodiment mutat ns 5 An embodiment of the present invention will now be described, by way of example only, and with reference to the accompanying figures in which: Fig, Iis a diagrammatic sectional view of a well in accordance with one aspect of the present invention; Fig, 2 is a schematic diagram of the ele which may be used in 20 a transmitting portion of a safety mechanism of the present invention; ig, 3 is a schematic diagram of the electronics which may be used in a receiving portion of a safety mechanism of the present invention; and, Figs. 4 -- 4c are sectional views of a casing valve sub in various positions. Figure 1 shows a well 10 comprising a series of casing strings 12a, 12b, 12c, and 12d and adjacent annual A,B,C,D between each casing string and the string inside thereof, with a drill string 20 provided inside the innermost casing 12a, As is conventional in the art, sac casing strinqs extends further into the well than the adjacent casing string on the outside thereof Moreover, the lowermost portion of each casing string is cemented in place as it extends below the outer adjacent string, In accordance with one aspect of the present invention, safety packers 16 are 10 provided on the casing above the cemented as well as on the drill string 20. These can be activated acoustically at any time including retroactively ie after the emergency, in order to block fluid flow through the respective annuity Whilst normal operation will not require the activation of such packers, they 15 will provide a barrier to uncontrolled hydrocarbon flow should the casing or other portion of the well control fail. ,,Moreover sensors (not shown), in accordance with one aspect of the present invention, are provided above and below said packers in order to monitor 20 downhole parameters at this point, This can provide information to operators on any unusual parameters and the sealing integrity of the packer(s), Acoustic relay stations 22 are provided on the drill pipe as well as varous points in the annual to relay acoustic data retrieved from sensors in the welIt A safety valve 25 is also provided in the drill string 20 and this can be activated acoustically in order to prevent fiuid flow through the drill sting.
24 in such an instance a device not shown) comprising a sonar receiver and an acoustic transceiver installed or later landed at a wellthead apparatus such as a BOP structure 30 at the top of the well. The operator sends a sonar signal from a surface facility 32 which is converted to an acoustic signal and 5 transmitted into the wefl by the device. The subsea valve 25 pkcks up the acoustic signal and shuts the well downhole (rather than at the surface), even if other communications are entirely severed with the SOP. In alternative embodiments a packer picks up the signal rather than the safety 10 valve 25. The packer can then shut a flowpath eg, an annulus. Thus embodiments of the Present invention benefit in that they obviate the sole reliance on seabed/rig floor/bridge BOP control mecnanisms. As can be observed by disastrous events in the Gulf of Mexico in 2010, the control of a 15 well where the BOP has failed can be extremely difficult and ensuing environmental damage can occur given the unoontrolle leak of hydrocarbons in the environment, Embodiments of the present invention provide a system which reduce the risk of such disastrous events happening and also provide a secondary control mechanism for controlling subsurface safely mechanisms, 20 such as subsurface valves, sleeves, plugs and/or packers, For certain embodiments a control device is provided on a buoy or vessel separate from a rig. The device comprises sonar transmitter and a satellite receiver. The device can therefore receive a signal from a satellite directed 25 from an inland installation, and communicate this to the weii in order to shut down the well; all independent of the rig, In such embodiments, the well can be safely closed down even in the disastrous event of losing the rig, 25 A casing valve sub 400 is shown Figs. 4a - 40 comprising an outer body 404 having a central bore 406 extending out of the body 404 at an inner side through port 408 and an outer side through part 410, A moveable member in the form of a piston 412 is provided in the bore 406 and canr move to seal the 5 port 408, SimliarIy a second moveable member in the form of a piston 414 is provided in the bore 406 and can move to seal the port 410, Actuators 416, 8 control the pistons 412, 414 respectively. The casing valve sub 400 is run as part of an overall casing string, such as a 10 osing string 12 shown in Fig. 1, and positioned such that the port 403 faces an inner annulus and the port 410 faces an outer annuius ln use, the pistons 412, 414 can be moved to different positions, as shown in Figs. 4a, 4b and 40, by the actuators 416, 418 n response to wireess signals IS which have been received, Thus the pressure between the inner and outer annual can be sealed from each other by providing at least one of the pistons 412, 414 over or between the respective ports, 408 410 as shown in Fig. 4a, 4c, 20 in order to eouanse the pressure between the inner and outer annual, the pistons 412, 414 are moved to a position outside of the ports 408, 410 so they do not block them nor block the bore 406 therebetween, as shown in Fig. 4b, The pressures can thus be equaised, 25 Thus such embodiments can be useful in that they provide an opportunity to equauise pressure between two adjacent casing annual if one exceeded a safe pressure and/or if an emergency situation had occurred, "26 The port can then be isolated and pressure monitored to see if pressure IS going to bulid-up again, Thus, in contrast to for example a rmpture disk, where it cannot return to its original position, embodiments of the present invention can equalise pressure between casing springs. be reset, and then 5 repeat this procedure again, and for certain embodiments, repeat the procedure indefinitely. In one scenario the pressure in a casing string may build up due to fluid flow and thermal expansion. A known rupture disk can resolve problems of t excessive pressure, and the well can continue to functon normally. However a further occurrence of such excess pressure cannot be dealt with. Moreover it is sometimes dif fcult to ascertain whether the excess pressure was caused by such a manageable event or whether it is Mdicaive of a more serious problem especially if repeated occurrences of the excess pressure cannot be 15 detected nor aiieviated in known systems. Embodiments of the present invention mitigate these problems. For scome embodiments, a number of different casing subs 401 may be used in one string of casing. Figure 2 shows a transmitting portion 250 of the safety mechanism. The 20 portion 250 comprises a transmitter (not shown) powered by a battery (not shown), a transducer 240 and a thermometer (not shown). An analogue pressure signal generated by the transducer 240 passes to an electronics module 241 in which it is digitized and serially encoded for transmission by a carrier frequency, suitably of 1Hz - 10kHz, preferably 1kHz - 10kHz, utiising 25 an FSK modulation technique, The resulting bursts of carrier are applied to a rmagnetostrictive transducer 242 comprising a coil formed around a core (not shown) whose ends are rigidly fixed to the wel bore casing (not shown) at 27 spaced apart locations, The digitally coded data is thus transformed into a longitudinal sonic wave, The transmitter electronics module 241 in the present embodiment comprises 5 a signal conditioning circuit 244, a digitising and encoding circuit 245, and a current driver 246. The details of these circuits may be varied and other suitable crcuitry may be used. The transducer is connected to the current driver 246 and formed round a core 247, Suitably, the core 247 is a laminated rod of nickel of about 25 mm diameter. The length of the rod is 10 chosen to suit the desired sonic frequency. Figure 3 shows a receiving portion 360 of the safety mechanism. A receiving portion 361 comprises a filter 362 and a transducer 363 connected to an electronics module powered by a battery (not shown). The filter 362 is a mechanical band-pass filter tuned to the data carrier frequencies, and serves to remove some of the acoustic noise which could otherwise swamp the electronics, The transducer 33 is a piezoelectric element. The filter 362 and transducer 363 are mechanically coupled in series, and the combination is rigidly mounted at its ends to one of the elongated members, such as the 20 tubing or casing strings (not shown) Thus, the transducer 363 provides an. electrical output representative of the sonic date signal. Electronic filters 364 and 365 are also provided and the signal may be retransmitted or collated by any suitable means 366, typically of a similar configton to that shown in Fig.2, An advantage of certain embodiments is that the acoustic signals can trave up and down different strings and can move from one string to another. Thus linear trave of the signal is not required. Direct route devices thus can 28 be lost and a siqnal can stsccessfiy be received indirectly, The signal can also be combined with other wires and wireless ornmurdcauon systems and does not have to travel the whole distance acoustically, improvements and modifications may be made without departing from the scope of the invention. Whist the specific example rela tes to a subsea w:it other embodiments may be used on platform or land based wells.