THERMITE METHOD OF ABANDONING A WELL

Abstract

A method of conveying materials or tools into a well, the well including a plurality of lengths of concentric tubing, comprising the step of permitting at least one cartridge to free-fall under gravity into the well. No line may be connected to the cartridge. The cartridge is selected from a group of cartridges which may comprise, a cartridge including thermite, hermetically sealed from well fluids, a cartridge including low temperature alloy, hermetically sealed from well fluids, a cartridge formed from low temperature alloy, a cartridge including a detonator triggered by impact, a cartridge including a detonator triggered by an electronic or mechanical clock, a cartridge formed from tungsten carbide, a bridge plug cartridge including slips to retain the bridge plug in a position against the wall of well tubing, a thermal barrier material, or a shock absorber that absorbs energy from subsequent cartridges being dropped.

Description

Over the past 20 years or so a large number of offshore structures have been constructed which are now or will soon be exhausted and will need to be abandoned. These offshore structures may comprise production platforms which are either steel or concrete structures resting on the sea bed or floating platforms. Numerous conduits are connected to these offshore structures to carry the various fluids being gas, oil or water etc., which are necessary for the production of oil and/or gas from the well.

In abandoning a well, consideration has to be given to the potential environmental threat from the abandoned well for many years in the future.

In the case of offshore structure there is usually no rig derrick in place which can be used to perform the required well abandonment procedure. Therefore it is typically necessary to install a new derrick or alternatively a mobile derrick can be positioned above the well. This requirement adds considerable expense to the task of abandoning the offshore well, compared to a land based well.

A typical production well will comprise a number of tubular conduits arranged concentrically with respect to each. The method of abandoning the well which is presently known in the art involves the separate sealing of each of the concentric conduits which requires a large number of sequential steps.

In the abandonment method known in the art the first step is to seal the first central conduit usually by means of cement or other suitable sealant. The first annular channel between the first and second conduits is then sealed and the first central conduit is then cut above the seal and the cut section is removed from the well.

The second annular channel between the second and third conduits is then sealed and the second conduit cut above the seal and the cut section is removed from the well.

This process is repeated until all the conduits are removed. The number of separate steps required is typically very large indeed and the number of separate operations is five times the number of conduits to be removed. This adds considerably to the cost of the well abandonment due to the time taken and the resources required at the well head.

It is the purpose of the present invention to provide a method of abandoning a well which avoids the disadvantageous and numerous operations which are required by the existing known methods. This will greatly reduce the costs of safely abandoning a well. It is a further objective of the invention to provide a method of abandoning a well without the requirement of a rig which involves significant expense particularly in subsea based wells.

It is a further advantage of the invention to isolate all the conduits and annuli with no return of the well bore tubulars to the surface. Furthermore, the method of abandonment of the well will comply with all the regulatory guidelines for the isolation of a well.

According to the present invention there is provided a method of abandoning a well, by connecting a set of cartridges together by a connection means and either dropping them into a well or lowering them on a cable into a well. The cartridges could consist of an ignitor, a low temperature thermite, a high temperature thermite, low temperature alloys (bismuth), bridge plug, thermal barrier to protect the bridge plug, shock absorber.

According to another aspect of the present invention to install the cartridges using a highly automated means of deploying into a subsea well

According to another aspect of the invention, once the subsea apparatus is connected to the well, it has sufficient materials (cartridges), plug removal and storage tool, cartridge lowering means to perform all tasks without having to be disconnected from the well.

According to a further aspect of the invention significant tubing is consumed to expose a large length of the next casing outside it. The operation above can be repeated until the open hole formation is exposed.

According to a further aspect of the invention, while the thermite and surround formation is still hot and above the natural formation temperature, a low melting point alloy can be distributed within the thermite, this alloy has a very low viscosity and flows into any crack, void or fissure. During cool down all the fissures and conductive passages are plugged by the then cooled down to ambient temperature solidified metal alloy. Thus the well is plugged well out into the natural rock formation away from the well in multiple zones and wellbore itself is permanently plugged by a magma mass.

According to a further aspect of the invention the sealing material could be a two part resin deployed cartridges by gravity.

According to a further aspect of the invention, the sealing material could comprise a low melting point alloy deployed using gravity and melted in situ using an electric heating element.

According to a further aspect of the invention, a cartridge with super reactive thermite could be used to cut the tubing or casing at a pre-defined place in the well.

According to a further aspect of the invention, a cartridge with bauxite could combine with the thermite and fuse resulting in additional sealing capability.

According to a further aspect of the invention, retarded thermite could heat the tubing or casing to a temperature below its melting point. This will result in the tubing or casing losing its mechanical strength, but not melting it.

According to a further aspect of the invention, the ignitor could be deployed as a cartridge.

According to a further aspect of the invention the thermite is used to sever the riser pipe the required distance below the mud line (typical 10-20 ft)

According to a further aspect of the invention ceramic balls are deposited on top of the thermite to contain the thermite and increase its temperature and direct the thermite energy to part the tubing or casing.

According to a further aspect of the invention tungsten carbide balls could be deposited on top of the thermite

According to a further aspect of the invention a ceramic barrier with a deflector surface on it to contain the thermite energy and direct it to part the tubing.

According to a further aspect of the invention many tools can be deployed and docked together downhole to form a long assembly.

According to a further aspect of the invention, the ceramic balls or tungsten carbide balls could be dropped from surface to form a heavy barrier onto of the thermite.

Thus by means of the method according to the invention the number of operations required is greatly reduced, thus resulting in a considerable reduction in the cost of carrying out the well abandonment.

The following is a more detailed description of an embodiment according to the invention by reference to the following drawings in which:

FIG. 1 is an illustration of a section side view through a well with various cartridges deposited inside the tubing lining the well;

FIG. 2 is a similar view to FIG. 1, after the different materials in the cartridges have reacted and have returned to the stable wellbore temperature;

FIG. 3 is section side view through a well with a casing and production tubing, with different cartridges installed inside the production tubing;

FIG. 4 is a similar view to FIG. 3, showing a subsequent stage in the process;

FIG. 5 is a similar view to FIG. 4, showing a subsequent stage in the process;

FIG. 6 is a similar view to FIG. 5, showing a subsequent stage in the process;

FIG. 7 is a similar view to FIG. 6, showing a subsequent stage in the process;

FIG. 8 is a similar view to FIG. 7, showing a subsequent stage in the process;

FIG. 9 is a section side view through a cartridge with features a top and bottom to enable the rapid assembly or more than one cartridge to another;

FIG. 10 is a section side view through a cartridge with a male and female thread top and bottom;

FIG. 11 is a section side view through a cartridge with a male and female mating features and a cross hole for a dowel pin to lock subsequent cartridges together;

FIG. 12 is a section side view through a cartridge with a timer, battery, electric circuitry, and a solid state ignitor material to set off the thermite reaction;

FIG. 13 is a section side view through a cartridge with a shock absorber built into it;

FIG. 14 is a section side view through a cartridge with low temperature pellets stored inside it;

FIG. 15 is a section side view through a cartridge which is machined from low temperature alloy;

FIG. 16 is a section side view through a cartridge with a pressure sensitive switch, which enables slips to be energised and set the cartridge at a controlled depth in the well;

FIG. 17 is a similar view to FIG. 16, with the slips activated;

FIG. 18 is a section side view of a subsea wellhead, Christmas tree and various workover packages installed on top of it to enable the cartridges to be deployed into the well in a controlled way;

FIG. 19 is a similar view to FIG. 18 at a different stage of the operation;

FIG. 20 is a similar view to FIG. 19 at a different stage of the operation;

FIG. 21 is a similar view to FIG. 20 at a different stage of the operation;

FIG. 22 is a section side view of a platform wellhead, Christmas tree and a workover package installed to enable cartridges to be installed in the well in a controlled way;

FIG. 23 is a section side view of an apparatus to rapidly supply cartridges to drop them into the well;

FIG. 24 is a section side view of a platform with an apparatus to enable the rapid positioning of a slickline lubricator over any of the wells without the use of a crane;

FIG. 25 is a similar view to FIG. 24 with the lubricator connected to a wellhead;

FIG. 26 is a similar view to FIG. 24 with the lubricator orientated horizontally to enable a tool to be loaded or unloaded;

FIG. 27 is a plan view of a platform work deck with the equipment previously described performing multiple concurrent operations;

FIG. 28 is a section side view of a well, with a bridge plug installed and a crumple type shock absorber dropped onto of it;

FIG. 29 is a similar view to FIG. 28 with a cartridge dropped on top of the shock absorber;

FIG. 30 is a similar view to FIG. 29 with the crumple shock absorber absorbing the impact from the cartridge above it and protecting the bridge plug below it;

FIG. 31 is a side view of a cartridge designed to separate the tubing outside it;

FIG. 32 is a section plan view XX of FIG. 31;

FIG. 33 is a section side view of FIG. 31;

FIG. 34 is a section side view of another embodiment of the cartridge;

FIG. 35 is a section side view through a tubing string in a well with another embodiment of tubing separating using thermite, a ceramic or tungsten directing face and ceramic or tungsten carbide balls;

FIG. 36 is a section side view through a well with the resulting parted tubing by the tool operation in FIG. 35;

FIG. 37 is a subsequent operation to FIG. 36 in which and ignitor and thermite cartridges are deposited through the tubing and they land on top of the ceramic or tungsten carbide balls and additional balls are deposited onto of the thermite;

FIG. 38 is a subsequent operation to FIG. 37 with the thermite ignited and the ceramic or tungsten carbide balls act like a stop and cause the casing to be severed;

FIG. 39. A,B,C,D,E Is a section side view through a different versions of a cartridge;

FIG. 40 is a section side view through an ignitor type cartridge; and

FIG. 41 A,B Is a section side view through second embodiment of a ignitor type cartridge;

FIG. 42 A, B, C is a sections side view through a slickline or wireline deployed and ignitor, the ignitor being activated by a mass or further cartridges being dropped on top of it;

FIG. 43 is a section side view of the wellhead deck, and the upper deck, with a BOP attached to the well and an automated cartridge loading system, loading cartridges into the well.

Referring to FIGS. 1 and 2 our cartridge method of deployment would enable us to deploy different combinations and quantities of the different materials. We could for example deploy normal thermite 1 if we wanted to melt the casing, or retarded thermite (not shown) if we did not want to melt the casing, we could deploy distributed ignitors 2, as a back up or to ignite at different depths in different sequence, and we could distribute the low temperature alloy 3, so when the thermite magna cools, it forms a solid magna in the borehole 4 with a small amount of slag 5 on top of it, any cracks or fissures 6 or small leak paths in the adjacent formation will still have low viscosity low melting point alloy 7 free to fill these which when cooled down to the formation temperature set hard and provide multiple seals 8 deep into the formation along the open hole. This combination of materials can enable any length of open hole seal to be achieved, without removing any of the tubing, casing or other equipment in the well.

Referring to FIGS. 3 to 8, an objective of this process is to get an access window to the open hole. How we achieve this is as follows; The cartridge assembly, consisting of a bridge plug 10, thermal barrier 11, ignitors 12, low temperature or retarded thermite 13, high temperature thermite 14, a running tool 15 and either slickline 16 or electric wireline used to lower the assembly into the well.

The running tool could contain electronics to initiate the setting of the bridge plug 10 and ignitors 12, or the bridge plug and ignitors could have internal timers to initiate their operation after a set period of time. The bridge would first have to set, and be pull tested by the slickline tool to ensure it had set correctly. The slickline tool could then be disconnected and returned to surface, or at least a safe distance above the top of the assembly. The lower ignitor 12 would ignite the low temperature thermite, this will react up to about 1250 C, this is below the melting point of the steel of the tubing it is inside, but it is sufficiently hot, and sufficient mass to make the whole glow red and loss all its mechanical strength, the upper ignitor 17 will ignite the high temperature thermite, this will reach 3000 C and will result in parting the adjacent tubing 18, and because the well is near vertical, gravity and the mass of the tubing and thermite will result in it collapsing against the internal diameter of the casing 19 outside it. This will result in a window 20 of significant length exposing the ID of the casing 19. As a rule of thumb, if we put inside the tubing 600 ft of cartridges we would create a window of about 300 ft. Clearly this depends on the tubing wt. its diameter relative to the ID of the casing 19. The tubing steel and thermite will form a solid metal magma mass, with a quantity of slag 21 on top. Now additional cartridges 22 can be either lowered into the well or dropped from surface to repeat the operation on the next casing 19 outside.

Referring to FIGS. 9 to 17 there are shown various embodiments of the cartridge, FIG. 9 shows a thin wall tube 220 with a lower end 221 bonded to the ID of the lower end of the thin wall tube 220, a circular wall 222 enclosing the lower end. A collet feature 23 extends from the enclosing surface 222. At the upper end, is top cap 24 which is bonded 25 into the ID of the tube 20. It has a closed in circular wall 26 which hermetically seals the contents of the tube. The contents 27 could be thermite, bauxite, or other material. The upper cap includes a recess 28 where it can be gripped by automated handling equipment, with the contents providing additional rigidity. An upper opening 29 allows the collet 23 of another cartridge to dock with this cartridge and a recess 30 allows the collet to permanently engage and lock the cartridges together, requiring no orientation.

An alternative method of connecting the cartridges would be have a male 31 and female 32 course thread incorporated into the end fittings 33,34 respectively. These would include a recess 35 for a handling system to engage, and a circular double-sided shoulder 36,37 with a shoulder angle of 27.5 degrees on each side. These act as a torque shoulder and prevent the threads from unscrewing.

Another alternative is to a simple male pin 40 and female hole 41, with a cross drilled hole 42 in which would be driven a dowel pin (not shown) this would need to be orientated to achieve this.

The lowest most cartridge could include a bull nose 50 this could be a separate part to be attached to a string of cartridges, or it could be integral with the end cap if the cartridge was to be dropped into the well on an individual basis.

Referring to FIG. 12, the cartridge could also contain a battery powered electronic timer ignitor. This would ignite a mixture 60 of barium peroxide and aluminium powder in a weight ratio of about 15:4. This is a stable mixture and can ignite at a relatively low temperature.

The electronic timer would be in a hermetically sealed unit 61 in the cap 62. It would consist of a battery 63, which cannot be active until a rip cord 64 is pulled. Once this is pulled the circuit is complete, and an LED 65 provides positive indication it is active. An electronic timer 66 counts a set amount of time (1 hr to 4 hrs typically) Once the time has elapsed, the circuit over heats the resistor 67 which initiates the ignition mixture 60, which then sets of the thermite 68.

Referring to FIG. 13, if the cartridges are dropped into the well using gravity, when they would come to rest on a bridge plug, the impact could sufficient especially when repeated many times be dropping many of these cartridges (100's meters potentially) they could unset the slips which hold the bridge plug to the tubing ID. By fitting a shock absorber cartridge (described below) between the bridge plug the thermite or ignitor cartridge the impact forces seen by the bridge plug slips will be significantly reduced. The shock absorber is quite simple, its principle parts consist of a cylinder 70 with a reduced ID 71 which traps a piston 72 of a long mandrel 73 of the moving part of the assembly. A spring 74 inside the cylinder keeps the tool fully extended, when a cartridge impacts the upper end 75 of the tool wellbore fluid inside the chamber has to exit through the narrow gap between the piston 72 and the cylinder wall 70, on the return stroke, wellbore fluid can easily enter the chamber 76 via a passage 77 and check valve 78.

Referring to FIGS. 14 and 15, the inside of the cartridge could be filled with low temperature alloy bismuth, in the form of small pellets 80 or the entire cartridge could be machined from bismuth 81. The bismuth would be heated by the thermite reaction, and it becomes extremely low viscosity, and remains very liquid as the thermite cools down, the benefit of combining this material is it fills any cracks or fissures that are created by the thermite reaction.

Referring to FIGS. 16 and 17, a cartridge module could be a electronically activated bridge plug, this could be time delayed, or pressure activated, so that slickline operations can be eliminated and the bridge plug can be dropped into the well and be activated at the required depth, there would be some degree of inaccuracy in its exact placement but it would eliminate the slickline operation completely. Or it could be deployed with a complete cartridge assembly as described in FIGS. 1 and 2. So a single slickline run could deploy the complete cartridge assembly. The bridge plug cartridge would consist of a standard upper and lower connection in this case 31, 32. Slips 90 would be retained in the unset position by pins 91, the pressure activated sensor 92, when at the pre-set hydrostatic pressure will release a cord 93 which allows the piston 94 move downwards into a chamber 95 with only atmospheric pressure in it. As the piston moves, the tapped pins 91 are naturally pushed inwards 96 allowing the spring 97 to push the slips upwards and push them up on the tapered surface 98 pushing the teeth 99 of the slips into the production tubing.

Referring to FIGS. 18 to 21 there is shown an apparatus which can be attached to a subsea well to access the well and deploy a string of cartridges into the well to perform the function as discussed earlier.

There is shown a subsea wellhead 100, connected to it is a subsea horizontal Christmas tree 101, to access the well a crown plug 102 has to be removed. The well workover package consists of an adaptor 103 which connects to the top of the tree.

The work over package consists of the following;

a tree plug removal and park tool 104,

a well control package 105

a slickline and lubricator package 106

a cartridge store and automatic loader package 107

From the top of the assembly, a rod 110 is extended from the plug storage area 111, it latches into the plug 102, unsets it and retracts together with the plug back into the plug garage 111. This is then rotated 180 degrees on its base 112, so that it is out of the way and the slickline lubricator 113 is aligned over the wellbore. Access to the well is now possible.

An automated cartridge deployment system can load the cartridges to be deployed in the well in a sequential manner. Cartridges are stored in a large storage container 114, are feed into the main bore 115 and gripped by a travelling gripper 116, this holds onto a cartridge 117 and latches it into a cartridge below it already in the well 118. Once connection confirmed, static grippers 119 release from cartridge 120, the assembly can be lowered down one cartridge and the static gripper can grip onto cartridge 118. Once this is confirmed, the travelling gripper 116 can release from cartridge 117 and then repeat the operation. This can be repeated until the required number and type of cartridges have been installed 121. The slickline tool 122, can then be lowered and latched into the upper receptacle 123 of the upper cartridge 124. The connection is first tested, and then the static gripper 119 on 125 can be released and the assembly can be run into the well with full control.

Once at the required setting depth the slickline can set the bridge plug and release from the top cartridge. It can return to surface and the process can be repeated to deploy another set of cartridges.

Referring to FIGS. 22 and 23 there is shown a platform wellhead, Christmas tree 131, well control package 132 and a loading mechanism 133. Cartridges are stored in hoppers 134, 135, a gate 136, 137 is opened to allow the controlled feed of cartridges onto a conveyor 138. The conveyor can be moved in the horizontal direction 139 so that it will be over the wellhead being serviced. Once the cartridge arrives at the wellhead it can be selectively picked up, orientated vertically 140 and dropped into a rotating barrel feeder 141. The rotating barrel feeder can access a pressurised well to drop the cartridge into the well, or an automated feeder described in FIGS. 18 to 21 to latch the cartridges together and deploy them using slickline can be positioned over the wellhead. The line feed hoppers 134, 135 can be topped up in real time with top up hoppers 142, 143.

Referring to FIGS. 24 to 26 the slickline lubricators 150 will be mounted in a swivel 151 which can orientate them from the vertical 152 to horizontal 153 for tool string loading and service.

The arm 154 holding the lubricators is mounted to a pillar 155 which can jacked up and down 156, rotated 157 and traversed 158 along a rail 159 so it can access any one of the 20 wells 160 on the platform shown.

Once in position the crane is no longer required for lubricator connection and disconnection from the BOP, this will significantly improve well operations.

Referring to FIG. 27 shows a plan view of all the equipment required, and it shows the philosophy of a factory abandonment process, that is concurrent operations, i.e. 3 wells can be in different sequence of abandonment

Well 1 Slickline operation 170

Well 5 Pressure test 171

Well 9 Thermite cartridges deposited in it 172

Referring to FIGS. 28 to 30. There is shown a bridge plug 180 described earlier in FIGS. 16, 17 set in the tubing 181. A shock absorber 182 is dropped from surface to protect the bridge plug from the subsequent cartridges 190 to be dropped. As the first cartridge hits the top 183 of the shock absorber, the end of the shock absorber flares open 185 because of the slits 184, this flaring open cascades down the shock absorber, as each recess 186, 187 are natural fold lines and the slits 188 readily collapse. As the folds expand they contact the ID of the tubing 189 and this prevents further collapse, preventing any serious forces being applied to the bridge plug, so any number of cartridges can be dropped and the bridge plug will be isolated from the impact loads.

Referring to FIGS. 31 to 38 there is shown a cartridge with a high temperature housing 200 and base 201, inside the housing is high temperature thermite 202, the base has a profile 203 which directs the ignited thermite out of ports 204, the ports 204 are filled with a low temperature material such as bismuth or plastic to keep the thermite isolated from the wellbore fluids. When the thermite exits the port it hits the ID tubing 205 and cuts through it. Above the thermite are cartridges of ceramic or tungsten carbide balls, these provide both a weight and sealing effect to contain the thermite and ensure the maximum heat and force is located at the pipe serving jet.

An alternative arrangement could be a plug 210 which has a ceramic or tungsten carbide deflector 211, and ceramic or tungsten carbide piston rings 212, these contain the thermite reaction 213 and direct the energy to sever the tubing 214, in addition the plug could have a set of one way slips 215 which prevent the plug being displaced up the tubing, but allow the free movement down of the plug. Above the plug could be additional weight provided by cartridges of ceramic or tungsten carbide balls 216.

Once the tubing is severed, the remaining tubing, thermite and ceramic balls form a plug 220 and a window or access 221 to the next casing out is available. More thermite cartridges 222 and ignitor 223 can be deposited into the space 221 via the tubing 224, then either cartridges of tungsten carbide balls can be deposited on top 225 of the thermite, or they can be poured into the well from surface, as small and heavy and will fall on top 225 of the thermite inside the larger casing diameter 221 and form a seal and weight ensure the thermite can get to a temperature and energy sufficient to sever the casing 226. This casing will then drop and form a plug with the thermite and tungsten carbide balls.

If another casing is outside this one (not shown) this operation can be repeated, until access to the cap rock is achieved. Once access to the cap rock is achieved bismuth can be deposited on top of the hot mass and it will melt and seal all cracks and fissures. Then when the thermite cools down to formation temperature the bismuth will go solid and expand by up to 3% to provide a permanent abandonment seal to the well.

Referring to FIGS. 39 to 44 there is shown a slickline tool assembly to achieve the same goal. It would be installed into the well in several runs, so any desired length of thermite can be deployed. Typically in well operations, tool strings of about 30 ft are only possible, in this example we have 5 separate runs into the well, so this assembly could be in the order of (5×30 ft) 150 ft.

Referring particularly to FIG. 42, the first module consists of a pressure set anchor, known pressure is applied and the check valve 340 moves a sleeve 341 downwards, this activates two slips 342, 343, this lock the anchor to the tubing, and the seal 344 provides a mechanical barrier. Above the seal is a thermal barrier 345 this is a ceramic or silica flour or sand material to protect the anchor from the heat generated by the thermite 346 above. At the very top of the tool is a standard GS running profile 347, in which a standard slickline tool can engage and disengage.

The next tool has a collet 348 to dock into the profile 347. This tool just contains thermite 349, and any number of these can be run depending how long a thermite plug is desired.

The next tool is similar to the previous tool, but with the addition of a mechanically operated ignitor. It has a slightly modified upper profile 350, which works in combination with the lower profile of the next tool 351. When 350 and 351 are connected, the collet 352 locates into the profile 353, a second collet 354 connects to the profile 355, now these rods are permanently connected, finally, a tool with tungsten carbide balls is connected to provide a seal and weight. This could also be like to deflector 310.

To activate the ignitors, the tool string is extended, the collet 352 can travel longitudinally in the recess 353, the rods 354, 355 move which breaks the seals 360, 361, on one side of the seal is glycerine 362, 363, and on the other is potassium permanganate 364, 365 and magnesium ribbon 366, 367. This we have two ignitors for the thermite.

At the top of the chamber 370 is a deflector 371 and ports 372 and it function has been described earlier.

Referring to FIGS. 39 to 41, there is shown a cartridge assembly 301, which is either a hollow container which could be made from plastic, aluminium, low temperature alloy, or a solid billet 302 of low temperature alloy as shown in E. It could be a made from a continuous tube 303, with bottom 304 and top 305 ends, the ends could be shaped with a male point 306 at the bottom and a corresponding female receptacle 307 at the top, this would allow them to stack together, and help guide the cartridge into the well without hanging up on any edges.

The inside of the tube could be filled with regular thermite, which can burn at up to 2,500° C., or be a retarded thermite powder 308 which will burn at around 1,000-1,250° C. when ignited. This powder consists of a mixture of aluminium, iron oxide and silica sand present in the ratios of 25:75:44. The silica sand acts as a moderator has an 100-200 mesh particle size and the iron oxide is dry roasted and has an oxygen content of approximately 16% to 18% by weight

The inside of the tube could also be filled with pellets of low temperature alloy 309

The end could be attached via friction welding, glue 310, or threads 311

The cartridge could also contain an ignitor, this could consist of a chamber 312 filled with KMnO4. A glass barrier 313, hermitically sealing this upper chamber. A small lower chamber 314 below the glass barrier containing glycerine. A pin 315 positioned to fracture the glass barrier. A shear pin 316 prevents the pin 315 from moving until sufficient weight of cartridges is above it. A further shipping safety pin 317 is added, additional safety.

The cartridge could also contain a battery powered electronic timer ignitor. This would ignite a mixture 320 of barium peroxide and aluminium powder in a weight ratio of about 15:4. This is a stable mixture and can ignite at a relatively low temperature.

The electronic timer would be in a hermetically sealed unit 321 in the cap 322. It would consist of a battery 323, which cannot be active until a rip cord 324 is pulled. Once this is pulled the circuit is complete, and an LED 325 provides positive indication it is active. An electronic timer 326 counts a set amount of time (1 hr to 4 hrs typically) Once the time has elapsed, the circuit over heats the resistor 327 which initiates the ignition mixture 320.

Referring to FIGS. 42 A, B, C, D, a slickline ignitor tool consists of two sections;

The upper section, this consists of the following. A GS running profile 331, A chamber 332 filled with KMnO4. A glass barrier 333, hermitically sealing this chamber. A small chamber 334 above the glass barrier containing glycerine. A pin 335 positioned to fracture the glass barrier.

The lower section, this consists of the following;

A length of blank pipe 336 to space out the slips 337 away from the ignitor reaction, inside the blank pipe is sand 338 or other thermal barrier material. A slip arrangement 337 to set the tool inside the tubing at any desired depth. A cup seal 339 to provide a pressure barrier, and a check valve 340 to allow well fluid pass the cup seal while installing or lowering the tool in the well.

A heavy weight 341 could be dropped from surface and its tip 341′ would land on the pin 335, resulting in it cracking the glass and initiating the ignitor.

Alternatively, the upper housing 342, could be held in an extended position by shear pins 343, when the weight of sufficient cartridges above it are present, it will shear the pins and again initiate the ignitor. Each cartridge will weigh about 7 lbs so, possibly we could set the shear pin value to be 500 lbs, so we would need in excess of 72 cartridges above it to shear the pins.

Referring now to FIG. 43, there is shown a wellhead housing 360 and Christmas tree 361 on top of which is attached a blow out preventer (BOP) 362, then a short extension tube 363 from the top of the BOP to the upper deck 364. The cartridges previously described would be loaded into containers 365, these would be mounted on a skid 366. Inside the containers they would be arranged on their side and on a sloping lower surface 367 so they would flow out of an open exit passage 368 freely under gravity. On exit, each cartridge would be oriented vertically and be conveyed on a conveyor to the upper entrance of the tube 363, the conveying belts 369 grip the cartridges and provide positive placement along the belt. At the end above the tube 363 the belts are positively disengaged from the cartridge 370 so the cartridge can free fall into the tube 363. Many containers can be linked together. The conveyor system 380, can be stored out of the way for transport, and can be positioned over any well by a combination of telescopically extending it 381, moving it axially 382 and adjusting its height over the well 383.

Claims

1. A method of conveying materials or tools into a well, the well including a plurality of lengths of concentric tubing, comprising the steps:

permitting at least one cartridge to free-fall under gravity into the well.

2. The method according to claim 1, wherein no line is connected to the cartridge.

3. The method according to claim 1, wherein the cartridge is selected from a group of cartridges which may comprise:

a cartridge including thermite, hermetically sealed from well fluids;

a cartridge including low temperature alloy, hermetically sealed from well fluids;

a cartridge formed from low temperature alloy;

a cartridge including a detonator triggered by impact;

a cartridge including a detonator triggered by an electronic or mechanical clock;

a cartridge formed from tungsten carbide;

a bridge plug cartridge including slips to retain the bridge plug in a position against the wall of well tubing;

a thermal barrier material; and

a shock absorber that absorbs energy from subsequent cartridges being dropped.

4. The method according to claim 1, wherein the cartridges are automatically fed into the top of the well.

5. A cartridge for use in a well, adapted to be allowed to free fall under gravity through the well, wherein the cartridge comprises a housing hermetically sealed from well fluids.

6. The cartridge according to claim 5, wherein the cartridge houses either thermite, a low temperature alloy, or a heat-shielding material.

7. The cartridge according to claim 5 wherein for the bottom of the cartridge being pointed.

8. The cartridge according to claim 7, wherein the top of the cartridge has a concave shape corresponding to the pointed bottom end.

9. The cartridge according to claim 5 further comprising a bridge plug which includes slips which are capable of being activated to retain the bridge plug in a position against the wall of well tubing.

10. The cartridge according to claim 5 further comprising a collapsible section which absorbs shock from items which fall on top of the cartridge.

11. The cartridge according to claim 5 further comprising which includes a detonator capable of triggering a thermite reaction.

12. The cartridge according to claim 11, wherein the cartridge includes an electronic or mechanical clock to trigger the detonator.

13. The cartridge according to claim 11, wherein the detonator is triggered by the action of the cartridge being brought to a halt in the well after being allowed to free fall down the well.

14. The cartridge according to claim 11, wherein the detonator is triggered by the action of another cartridge being dropped on it from above.

15. A cartridge for use in a well, formed predominantly of low temperature alloy or of tungsten carbide.