Field of invention. The claimed invention relates to water wells that has not been provided with a sufficient annular seal and where the spacing between the borehole and the casing of the well allows surface water and contaminants to travel along the casing to the aquifer or where two or more adjacent aquifers becomes interconnected by the spacing between borehole and casing. The spacing between the casing and borehole is in older wells often filled with gravel, but often water can travel through this gravel and carry pollutants from the surface to the aquifer or allow higher aquifers of lower quality to flow through the gravel filled spacing to a lower aquifer of better quality from where the water is acquired.

Systems to repair such wells by preventing flow of contaminated water along the well casing in the annular spacing by injecting a sealing material exists, but the use of these systems introduce a risk of damage to the well, that may necessitate a very expensive renewal of the entire borehole and well casing.

The invention discloses two tools and a method of introducing seals in the gravel-filled spacing in existing wells to terminate flow from surface to aquifer or between aquifers interconnected by the well casing and borehole without the risk of permanent damage to the well casing.

Summary of invention.

The claimed invention concerns a method of sealing insufficiently sealed annulus between well casing and borehole in wells and a preparation tool able to melt valve inserts through the plastic material wall of a drinking water well casing to enable the injection of Bentonite slurry to seal leaks and prevent possibly contaminated surface water from reaching the aquifer of the well through the borehole annulus. The preparation tool further enables the plugging of penetrations made where obstacles outside the well casing prevent valve inserts from being properly placed and secured for injection purposes and thus eliminates the risk of damaging the well casing by introducing a perforation that cannot be sealed. The invention concerns: method of inserting valve inserts in a well casi (Claims 1-2)

-a method of sealing the annulus around a well casing. (Claim 3)

-valve inserts to be inserted in a well casing (Claims 4-7)

-a tool for inserting valve inserts in a well casing (Claim 8)

-a tool for sealing the annulus around a well casing (Claim 9)

-a combined tool for inserting valve inserts and sealing a well casing. (Claim 10)

The valve inserts acts as temporary passages through which sealing material can be injected into the surroundings and seals off the injected areas automatically as soon as injection is completed.

The invention further describes a sealing tool able ensure uniform injection and sealing through said valve inserts.

Background of invention. Water wells are established by creating a borehole from the ground surface to an aquifer (at water containing layer) and installing a pipe structure normally referred to as a casing from above surface level to the desired aquifer. In the lower end of the casing, a large number of small holes are pre-made in the pipe section is placed in the aquifer to allow water to enter the casing. Usually a filter surrounds the perforated section of the casing. The well may go through several aquifers and allow water from one or more to enter the casing. In some cases however, the purity of the water of an aquifer is insufficient and is intentionally prevented from entering the casing by not installing a perforated section in the casing in this layer.

Since aquifers of different water quality can exist in different layers, these must by nature be essentially hydraulic isolated from each other, meaning that water from an upper aquifer of poor quality cannot penetrate the isolating layers between the aquifers and mix with a lower aquifer of better quality water. Likewise the most upper aquifer must by nature be protected from surface water pollutants and contamination either by filtering or isolation, if such pollutants or contamination are present at the surface, for the water in the aquifer to remain unpolluted.

For obvious reasons these isolating layers are penetrated by the borehole and to install a casing within the borehole, the diameter of the borehole is required to exceed that of the casing. It is therefore required to fill the spacing (normally referred to as the annular spacing or annulus) with a sealing material the prevent water from the surface or an upper aquifer to flow along the outside of the casing in the annular spacing through the penetration of the isolating layers. The most common sealing materials for this are cement and Bentonite. The sealing has to extend from above surface level down to just above the (upper) perforated section of casing that allows water to enter.

However, in a large number of wells, gravel has been used to fill the annular spacing or the sealing has been insufficient, damaged or incorrectly carried out, all resulting in water transport between surface and upper aquifer or from an upper aquifer to a lower. The common solution to such a problem is either to replace the entire borehole and casing, by removing the casing and increase the diameter of the borehole and install new casing and annular sealing or to plug the well entirely by removing the casing and increase the diameter of the borehole and fill it completely with sealing material and create a new well at a different location. Both solutions require removal of the casing, at least an increase of borehole (essentially a new borehole with an increased diameter concentric with the original borehole) and in case of renewal of the well, instalment of new casing and filter and the risk of a new leak in the sealing. This is obviously a very expensive procedure and often results in closure of a well without establishing a new one.

Both from an economical and environmental point of view, it would be desirable if such leaks could be sealed and existing wells repaired and thus prevent permanent pollution and contamination of the involved aquifers.

Technical solutions to enable such sealing have been suggested prior, but none without significant drawbacks and insufficiencies that has prevented practical use of these. Prior technical solutions are based on penetrating the casing from the inside and thereby gain access the annular sealing at the area of the leak and pump sealing material into the void in the filler/sealing material or lack of sealing/filler material in a volume of the annular spacing. Leaks in the sealing of the annular space could be cracks in the cement or the void between the pebbles of the gravel used as an (insufficient) sealing. However, the prior art solutions are based on pumping in cement, which is not a very good material for such purpose, and the solutions does not provide a solution of plugging the temporary access penetration of the casing, but relies on the sealing material to seal the casing as well as the leak.

Cement is for several reasons not a very good material for the purpose. First of all, cement is not a very good sealing, since water can travel through cement, second cement will settle and shrink, third it may crack and last but not least it presents a risk of damaging the casing, if the casing is penetrated at a location of non-porous surroundings. If the casing is penetrated at an area of non-porous surrounding, which could be a large piece of rock right next to the casing, cement cannot be pumped in and seal the access hole and the potentially polluted water then has direct access to the inside of the well casing, actually worsening the problem the system was designed to solve.

The lack of ability to plug the penetration hole in the casing after sealing is an even larger problem if the preferred sealing material Bentonite is to be used. Bentonite is preferred as a sealing material for this purpose for two main reasons. First of all, it is practically impervious to water and seals effectively and second, it swells when being hydrated and thereby fills voids more effectively. The latter presents a problem if the penetration of the casing cannot be plugged after injection of the Bentonite into the area of defective sealing, since the Bentonite expands during swelling in the direction of least resistance, which would obviously to some extend be back through the penetration of the casing and into the well.

The claimed invention provides a technical solution to enable injection of a swelling sealing material through a penetration of the casing by enabling plugging of this penetration regardless of surrounding porosity by use of a single apparatus to perform all necessary tasks, thereby eliminating both the risk of damage to the well casing as well as eliminating the need for detection of accurate position of penetration and subsequent accurate positioning of a plugging or repair tool.

Prior art. The present invention is related to the repair of old or inadequately sealed annulus of water wells, but the majority of related prior arts are from the field of oil and gas wells. Means to penetrate an installed well casing at a chosen depth are described in several documents. The most relevant of these documents are:

A) US Pat. No. 4.765.173, Well penetration apparatus, Herman J. Schellstede, Filed

August 21 ^st . 1986

B) EP 0962624A1, Device for making or regenerating water wells, Idropalm s.a.s. di

Gattuso C. & Co. (Francesco Palamara), Filed June 4 ^th . 1998

C) US. Pat. No. 4.158.388, Method of and apparatus for squeeze cementing in boreholes, Pengo Industries, Inc. (Harold D. Owen, Wayne O. Rosenthal), Filed June 20 ^th . 1977

D) GB2340158A, Hydraulic tubing punch, Baker Hughes Incorporated (Larry Thomas Palmer, Gary E. Cooper, Jonathan Price), Filed July 29 ^th . 1999.

E) WO 2012/069634A1, Downhole punch component, Welltec (J0rgen Hallundbaek and Paul Hazel), Filed November 25 ^th . 2011

F) DE 102 15 689 Al, Vorrichtung zum Injizieren eines viskosen Mediums in einen

Ringraum eines brunnen, Manfred Thumler, Filed April 4 ^th . 2002

The invention disclosed in US Pat. No. 4.765.173 (A) is a puncher intended to punch holes in a downhole bore by means of hydraulic actuation of a ramp mechanism that force a punch through the well casing and allows a built-in hose with pressure jets to extend out through the created opening in the well casing and wash out small particles in the surrounding strata, to increase the flow of oil into the well casing.

In EP 096262A1 (B) a device for simultaneously creating multiple penetrations in a water well casing and delivery of a slurry of cement or other supporting or sealing material through the punched openings are described. The device punch holes in the well casing through a ramp mechanism much like the one described in document A) (US Pat. No. 4.765.173) and delivers sealant through a valve in the puncher.

The device described in US Pat. No. 4.158.388 (C) is also a device for creating holes in a well casing to gain access to the annulus and inject cement or other supporting or sealing material. In this device the punch is performed by a gun powder driven projectile.

In DE 102 15 689 Al (F) a device containing two pistons, each equipped with hollow puncher, is fitted in a chamber connected through a pipe or hose to a surface reservoir. By pumping fluid under pressure in the chamber, the pistons are forced outward until the pistons are resting firmly against the inside of the well casing wall. During the pistons movement, the hollow punches penetrates the well casing and establish a flow channel from the chamber inside the well casing to the annulus outside the well casing. The fluid being pumped inside the chamber will flow through the chamber and out through the hollow punches and into the annulus. When pressure is released, at spring pulls the pistons back inside the chamber and the punches are retracted from the penetrations of the well casing.

The devices described in the above mentioned documents (A, B, C and F) are all capable of creating a penetration in a well casing to allow some sort of fluid or slurry to be injected in the annulus or surroundings of the well casing. However, these solutions are not very well suited for restoring the sealing of the well casing of water wells, since they suffer from some significant drawbacks.

Cement is well suited for supporting a well casing, but not for sealing purposes. First of all cement is permeable to water and second, cement will often crack due to shrinking while curing and thus leave open paths to water. In oil wells this is not a problem, but when sealing water well casings to prevent contamination to reach aquifers by flowing along the well casing even a limited flow is unacceptable. For such reason Bentonite is the preferred material of sealing, but Bentonite swells where cement shrinks, which worsens the main drawback of prior art. Both when using cement or Bentonite is it important that the slurry is of fairly low viscosity to enable penetration of small cracks and eliminate voids. This requires a high content of carrying fluid which again increases settling time. Since the proposed solutions mentioned above all basically leave the well casing perforated, the sealing of the well casing after filling the voids and cracks in the annulus of the well casing, rely on the sealing material. None of the prior art documents (A, B, C and F) solves the problem of restoring the well casing wall integrity in regard of plugging the penetration made to allow the injection of sealant. Since the repair will often have to be carried out under water in the well casing, there is a significant risk of the sealant being washed out after injection or during later operation of the well, leaving the well in worse condition after the sealing attempt than prior to the sealing attempt. If the device for introducing the sealing material is removed prior to settling, the sealing material will to some extend flow into the well casing, leaving a void and may very well leave a significant leak in the well casing barrier, worsening the original problem of contamination the well.

If the device is left for the sealing material to settle, time consumption and costs will increase significantly, the device will be blocked with settled sealing material and need

dismantling/repair and will still leave the well casing unclosed and may allow future contamination to enter the well directly through the insufficiently sealed perforations of the well casing. Especially when using Bentonite that doesn't settle or cure, there is a risk of the Bentonite sealing of the penetration of the well casing wall will be washed out during operation of the water well and the injected seal will not only deteriorate, but also leave an additional opening for contaminants to enter the well.

The documents D) and E) both describe devices to create perforations in a well casing and during the process, fit a valve in the perforation, thus creating a one-directional flow option between the well casing and the annulus or strata.

In GB2340158A (D) a device primarily intended for the creation of perforations in oil well casing through a hydraulically actuated ramp mechanism, similar to the devices described in documents A)- to C), is described. In the description it is however mentioned, that these perforations could be used for squeezing in cement for support purposes around the well casing, but the document includes no further teachings concerning the injection of cement other than referring to other equipment. The document also reveals an option of inserting a valve in the perforation made by the puncher and from the description of preferred embodiment, it is obvious that the intended method is to use the valve elements as the punching tool and detach it from the punching actuator mechanism and leave the valve in the well casing. The valve is not intended to allow flow from the device inside the well casing out through the wall of the well casing or from inside the well casing to outside the well casing, but to allow flow into the well casing.

WO 2012/069634A1 (E) discloses a device that carries a number of insertion elements into a well casing, able to insert these insertion elements in the well casing wall by either punching the elements through the well casing wall or by rotating the insertion elements to cut or grind through the well casing wall. These insertion elements are equipped with a cutting or grinding edge in the front to be able to penetrate the well casing wall and may have a slightly larger diameter of the body than the cutting edge to secure the insertion element by press fitting or have a threading of the body to enable the insertion element to cut through the well casing wall, cut a threading and screw itself in. It is furthermore described how these insertion elements could have a build-in valve and the invention disclosed does hence reveal how to insert a valve in a well casing and fix it by use of a threading in one process using a single tool. The invention disclosed furthermore teaches how to enable the insertion of multiple valves at different locations of the well casing without retracting the tool from the well casing between each insertion.

What is not disclosed in prior art, is how to use the inserted valves to create a temporary opening in a well casing to allow injection of sealing or supporting material through the well casing wall in to the annulus and ensure sealing of the well casing immediately after injection. None of the devices described in prior art presents a solution to the problem of squeezing in sealing material in the annulus through the inserted valves and thus seal the well casing wall immediately hereafter, nor does any combination of use of the described devices solve the problem. Furthermore, a combination of solutions are not obvious even to the skilled person which is clearly indicated in document D) GB2340158A where it is mentioned that the perforation can be used for squeezing in cement or that the punch can be fitted with different types of fittings to be left in the casing, but does not mention or indicate any teachings of combining the two. Nor does it mention the idea of inserting a valve through which cement or sealing material can be injected and immediately and permanently thereafter seals the well casing or give any teachings on how to inject sealant through such an inserted valve. Likewise, document E) WO 2012/069634A1 teaches how different fittings can be inserted into a wall and allow one-directional flow into the well casing or insert a controllable valve, as well as how to place the cutting edge of the punch on the fitting to be inserted and enable the fitting to be fastened by a threading, but does not teach how to inject sealant through an inserted valve and use said inserted valve as a temporary access to the annulus surrounding the well casing and leave the valve no longer functioning but as a simple plug after sealing of the annulus.

In all prior art describing the injection of sealant through a penetration of the well casing, the injection of sealant is performed through an opening in the well casing wall with no valve restricting the flow direction and none of the prior art describes a solution of other than injecting sealant through penetrations in the well casing wall without the need of inserting an injection tool or nozzle placed directly in each penetration, thereby actually preventing sealing of the well casing penetration itself because the injector itself creates a void in the sealant inside the penetration itself to ensure sealant enters the penetration and proceeds out in the annulus and not back inside the well casing.

Furthermore, none of the prior art or any parts or combinations thereof, teaches how to ensure the ability to create a temporary access channel through a well casing made of a plastic material and seal the said plastic material well casing even in the event of a rock or other obstacle preventing a punch with a preceding cutting edge to penetrate and fasten in the relatively soft material of plastic. The latter presents a significant risk of destroying the well casing and thereby the well bore completely during the attempt to repair or improve it.

As it is of high importance to be able to insert either a valve or a plug for sealing if a valve cannot be inserted due to obstacles on the outside of the well casing, it is necessary to be able to remove a valve that fails to fully insert and the cut out section of well casing wall that was intended to be replaced by a valve insert. In prior art describing inserting of a valve in the well casing wall, it is assumed that a valve can either be inserted or replaced by forcing the insert containing the cut out section of well casing wall beyond the outside of the well casing steel wall and securing the insert by threading cutting its way in the well casing steel wall. This assumption is only valid if the well casing steel wall is strong enough to allow crushing or moving the obstacle preventing full insertion and securing of the insert.

However, when operating on well casing walls in plastic materials this will most often not be the case. Furthermore, the intended use of prior art may not suffer much from one or two failed insertions leaving a leak in the well casing wall, since the primary use of prior art is to ensure flow into an oil well. Therefore the use of prior art in a water well with a well casing wall made in at plastic material introduces a risk of creating a penetration that cannot be sealed and the well casing is damaged, necessitating expensive renewal. The ability to remove both a failed valve insert and the cut out section of well casing wall is therefore essential to solve a potential problem even worse than the initial problem the sealing procedure was intended to solve.

Thus, the invention presented in this document presents a solution to a technical problem that prior art does neither solve nor give any teachings on how to solve. Since prior art through decades of development of well equipment describes options of either inserting a valve to ensure flow is allowed in only one direction or creating a penetration through which cement/sealing material can be introduced in the annulus, the idea of using a valve as a combined puncher and sealing, not relying on the sealant itself to seal the well casing penetration, is clearly non-obvious even to the skilled person. The invention described in this document must therefore be considered novel and inventive.

Description of invention. The claimed invention is a tool system that enables the repair of water wells in which possibly contaminated surface water is able to flow along the well casing into the aquifer from which drinking water is extracted. This phenomenon is known as the chimney effect and is common to older water wells where the annulus between the well casing and the borehole are filled with gravel or cement rather than Bentonite as newer water wells. The borehole is often reinforced with a cement lining, that can either be damaged, be settling in the ground or be made in insufficient height above ground level and thus allow surface water to enter the annulus and travels along the well casing to the aquifer. Furthermore the well casing penetration between aquifers may also allow communication of water between the aquifers that are not desirable. The tool system is divided in two tools, both intended to be successively suspended in a wire system and lowered into the well casing from ground level and connected to a hydraulic pressure supply and control system at ground level. The preparation tool is intended for fitting one-way valves in the well casing. The sealing tool is intended for injection of slurry though the valves to seal the well casing. The sealing tool is furthermore through a hose connected to a Bentonite slurry supply through a feeding pump.

The preparation tool is divided into sections carrying out different tasks and subtasks. The tool is of a cylindrical shape with a diameter smaller than the inner diameter of the well casing. At the upper and lower end of the tool, hydraulic supports are fitted with the purpose of fixing the tool during operation when having been placed in correct depth and circumferential position by the carrying wire system.

A sub-frame linked and guided to the main frame structure is hydraulically operated and able to perform a linear motion in the radial direction of the cylindrical tool and thus in radial direction of the well casing. The sub-frame carries a drive unit driven by a chain or belt connected to a hydraulic motor fixed to the main structure of the preparation tool. The drive unit is equipped with a drive shaft, at the front end of which a hydraulically operated clutch mechanism enables inserts and plugs to be fixed in shafts rotational and axial direction when clutch is engaged. In front of the drive shaft a magazine containing inserts and plugs is placed. This magazine is able to move up and down through two hydraulically actuated mechanisms, one for each direction.

When the sub-frame moves forward in radial direction, the drive shaft engages with an insert and the clutch mechanism is engaged as to lock insert with drive shaft. The sub-frame is then moved back and the insert is pulled backwards out of the magazine. The magazine can then be lowered by use of the magazine actuators. The sub-frame is then moved forward and press the insert against the well casing wall. While the hydraulic actuator of the sub-frame ensures sufficient force to press the insert against the inner surface of the well casing wall, the hydraulic motor drives the drive unit through the chain or belt drive, causing the shaft and insert to rotate.

The combined rotation and force perpendicular to the well casing wall applied by the insert on the inner surface of the well casing wall, causes the contact area between the front edge of the insert and the well casing wall to heat up due to the friction between the rotating insert and the well casing wall. The plastic material of the well casing wall begins to melt in the contact zone and the melted plastic is displaced by the intruding insert. The front part of the insert is shaped to guide the melted plastic away from the edge of the insert to the inside of the insert. Inside the insert a recess is filled by the molten plastic. By melting the insert through the well casing wall instead of cutting, the release of shavings and cutting residuals are minimised. Such particles could otherwise clog filters or contaminate the water in the well.

When the insert has penetrated the well casing wall, the insert protrudes through the well casing until the threading of the rear part of the insert connects with the well casing wall due to the larger diameter of the threading. The combined rotation and force applied on the insert will then cause the threading to cut into the well casing wall and cut a mating threading herein and thus help pulling the insert into place until rear end of insert is essentially flush with inner surface of well casing wall. When insert is essentially flush with inner surface of well casing wall, the carrier of the shaft transmitting the torque to the insert can be disengaged and the shaft released from the insert now attached in the well casing.

The section of well casing cut out to allow insert to penetrate well casing wall is now firmly fixed inside the front end of the insert.

The tool is then ready for a new insert and injection procedure. If however an immoveable obstacle prevents the insert from being inserted and secured properly by the threading, the forward motion would either be blocked before the threading of the insert starts cutting a mating threading in the well casing wall or while the treading of the insert is cutting a mating threading in the well casing wall. In the latter case, the insert will start working like a drill and increase the diameter of the perforation, if torque applied on the insert is excessive.

If an obstacle prevents the proper insertion and securing by threading, a new leak has been introduced to the well casing and closer to the surface than the leak it was the intention to repair, which will often mean that the degree of contamination level of the downdraft water is even higher since some of the contaminants will most likely be filtered out as the polluted water travels through the gravel of the annulus between the well casing wall and the borehole cement reinforcement (if any). Furthermore the introduced leak will most likely be even larger than the original leak. Such scenarios are the major disadvantages of prior art in the field, since none of them provide a feasible solution other than renewal of the entire well. With this tool however, the driveshaft rotation can be reversed, thereby unscrewing the insert to release from any partially cut mating threading in the well casing wall and allowing the hydraulically actuated sub-frame to pull the insert out of the perforation, move the magazine up and place the insert back in the magazine. The drive shaft clutch mechanism is disengaged and releases the insert and the drive shaft can be further retracted to allow movement of the magazine.

The magazine can then be moved up or down until a shorter plug is positioned in front of the drive shaft. The drive shaft is then moved forward by hydraulic actuation of the sub-frame and through engagement of the clutch, fixed to the drive shaft. The plug is retracted from the magazine and the magazine lowered and the drive shaft with the plug moved forward, into the perforation of the well casing made by the insert, where it is screwed into place and secured by the treading. The clutch can then be released and the drive shaft be retracted by the sub- frame and the leak introduced by the failed attempt to install an insert is repaired.

If the section cut out of the well casing is not firmly fixed in the insert, the section will most likely be caught at the edges and be replaced in the penetration from where it was cut out. Since the insert could not be inserted all the way because of an obstacle, it would prevent the insertion of a plug, if the cut-out section of the well casing is not removed by the insert, but left to block the penetration. When an insert has been placed in the well casing, the hydraulic supports are released and the tool rotated a number of degrees in axial direction within the well casing and the hydraulic supports reactivated. A new insert can be placed and the preparation rotated a number of degrees again, until a number of insets are placed along the circumference of the well casing. The preparation tool can then be removed from the well casing and the sealing tool inserted.

The sealing tool consist of two inflatable or hydraulically operated units designed for expansion primarily in radial direction inside the well separated by a section of reduced diameter, where the section of reduced diameter is connected through a hose or other channel to allow flow from a reservoir containing a Bentonite slurry (or other sealing material) placed at the ground surface (or higher). A valve is placed close to the reduced diameter section to allow control of flow from reservoir into reduced diameter section.

The sealing tool is suspended in a wire suspension system and lowered into the well casing. The sealing tool the secured by inflating or expanding the sections at each end of the section of reduced diameter. The expansion pressure or force should be adequate to seal of reduced diameter section in both ends in axial direction. The sealing tube is placed, secured and sealed in a position where the volume defined by the well casing and the upper and lower sealing includes the circumference on which a number of inserts are placed.

The Bentonite slurry can then be pumped through the hose into the volume of the sealed section of reduced diameter of the sealing tool and into the insert. Inside the insert the pressure of the Bentonite slurry cause the spring loaded ball valve to open and allow the

Bentonite slurry to pass through the insert and out through the exit channels of the insert on the outside of the well casing wall. The Bentonite slurry is thus injected into the voids in the gravel of the annulus or the ground surrounding the well casing with a uniform pressure along the circumference of the well casing. As the Bentonite slurry travels through the voids and fills these, flow resistance or back pressure of the Bentonite slurry flow builds up and at some point the back pressure and the spring load of the ball valve equals the inlet pressure of the insert and the ball valve close. If hydraulic pressure in the sealing volume due to failure in one or both expansion seals or Bentonite slurry pump pressure is suddenly lost, a similar situation will occur and the ball valve will close. In the event that Bentonite injection is interrupted due to malfunction as mentioned above, injection can just be resumed when malfunctioning equipment is repaired and continued until desired pressure or filling volume is reached. Different means as ground radar, ultrasound or other detective means to determine extend of slurry injection can also be used as a controlling parameter for when to stop Bentonite injection.

When the controlling parameter (pressure, volume, detected filling, etc.) is reached, the valve controlling the flow into the sealed volume is shut. The spring loaded ball valves of the inserts will then close and prevent the injected slurry to run out and into the well casing. The expansion units can be deflated and the sealing tool is released and can be retracted or moved vertically into the next injection position.

Description of drawings. Figures a illustrates the use of the method and figures b illustrates examples and details of preferred embodiments.

List of figures:

Method/use

Fig. la: Cross sectional sketch of water well Fig. 2a: Positioning of tool in a well.

Fig. 3a: Key components in tool

Fig. 4a: Drive shaft engaging with valve insert.

Fig. 5a: Positioning valve insert for penetration of well casing wall.

Fig. 6a: Penetration of well casing by valve insert melting through well casing wall. Fig. 7a: Securing valve insert in well casing wall.

Fig. 8a: Disengagement of drive shaft and retraction from secured valve insert.

Fig. 9a: Positioning insert for engagement with drive shaft.

Fig. 10a: Valve insert secured in well casing

Fig. 11a: Overview of well system prepared for sealing with valves inserted. Fig. 12a: Detailed view of inserted valves in well casing. Fig. 13a: Positioning of sealing tool in well.

Fig. 14a: Filling of sealing tool void with sealant.

Fig. 15a: Sealing of well.

Fig. 16a: Detailed view of sealing process.

Fig. 17a: Removal of sealing tool from well.

Fig. 18a: Overview of sealed well system.

Fig. 19a: Detailed views of sealing of well.

Fig. 20a: Illustration of partially inserted valve due to tools failure.

Fig. 21a: Illustration of failed tool recovery and sliding out magazine.

Fig. 22a: Illustration of obstacle preventing valve insertion and securing.

Fig. 23a: Retraction of valve insert and melted out section of well casing wall.

Fig. 24a: Storage of failed valve insert in magazine.

Fig. 25a: Engagement of drive shaft and plug insert in magazine.

Fig. 26a: Insertion and securing of plug insert in well casing wall.

Fig. 27a: Inserted and secured plug and retraction of drive shaft.

Fig. 28a: Detailed view of plug inserted and secured in well casing wall.

Embodiment:

Fig. lb: Overview of preferred embodiment of Preparation tool unit.

Fig. 2b: Overview of preferred embodiment of sealing tool unit.

Fig. 3b: Details of valve inserts.

Fig. 4b: Details of drive shaft.

Fig. 5b: Magazine. Fig. 6b: Magazine actuation.

Fig. 7b: Detailed views of retaining recess in valve inserts.

Description of use. Fig, la:

In fig. la a cross sectional view of a water well is sketched. Pumps and internal piping is removed for simplicity. The sketch is not depicting actual proportions and the distance between the aquifer and ground surface may be several hundred meters.

In the ground (101a) contamination of pollutants at ground surface level is prevented from reaching an aquifer (103a) by a layer of clay or other sediment (102a). This is not manmade, but the basic principal in natural water reservoirs.

Inside a borehole (104a), a well casing (105a) extracts drinking water from the aquifer (103a) and is surrounded by a gravel filled annulus (106a).

The left side of the sketch illustrates a situation where surface water with contaminants (107a) flowing through the ground (101a) along the borehole (104a), through a crack or other void in the isolating clay layer (108a) to enter and pollute the aquifer (103a). As a result, the extracted water aquifer (103a) is contaminated with polluted surface water.

The right side of the sketch illustrates a situation where contaminated surface water (107a) enters the gravel filled annulus (106a) and flows inside the borehole (104a) through the gravel along the well casing (105a) into the aquifer (103a). Inside the gravel filled annulus (107a) there is a large piece of rock (109a) that does not present a problem, but presents a risk if prior art is used in an effort to repair the well.

Due to inadequate sealing, the contaminated water from the ground surface flows within the gravel filled borehole annulus (106a) along the well casing (105a) into the aquifer (103a) and contaminates the extracted drinking water of the well.

Fie- 2a. To repair the well, a preparation tool (201a) is inserted at level where the drive shaft (206a) is aligned with the intended level of sealing (205). Prior to insertion pump and piping (not shown is removed from the well casing). The preparation tool (201a) is lowered into position by a wire (not shown) and fixed by hydraulic supports (202a). In some of the following figures only key components located within the area (203a), necessary for the understanding of working principal are shown.

F'g- 3a.

Inside the cylindrical preparation tool casing (not shown) a drive unit (301a) is fitted on a sub- frame (302a) able to move linearly in the tool casings radial direction. The drive unit (301a) is connected to a hollow shaft (304a) that through a locking mechanism (305a) is able to connect and lock-up with an insert (306a). The sealing level/vertical position (312a) is given by the vertical position of the drive shaft (304a) when the preparation tool is fixed in the well casing (303a). The drive unit (301a) is driven by a hydraulic motor (not shown) though a chain or belt (307a) to allow the said linear motion of the drive unit. The drive unit (301a) is hydraulically connected (308a) with the inside of hollow shaft (304a) to allow engagement and release of ball lock mechanism (309a). The hollow drive shaft (304a) can be rotated in both directions. A magazine (310a) containing both valve inserts (306a) and plug inserts (311a) can be moved up and down in front of the drive shaft (304a) by actuator mechanisms not shown here.

Fig. 4a.

The magazine (401a) is driven up by actuators (not shown) to place a valve insert (402a) in front of the drive shaft (403a). The drive shaft (403a) is moved forward to engage with the valve insert (402a) and the ball lock (404a) is engaged to interlock the drive shaft (403a) with the valve insert (402a).

F'g- 5a. The magazine (501a) is driven down by actuators (not shown) to allow drive shaft (503a) and valve insert (502a) to pass above magazine (501a). The drive shaft (503a) is then moved forward until the front of the valve insert (502a) collides with the well casing wall (504a).

Fig. 6a.

The drive unit (not shown) applies a combination of force in radial direction and a rotational movement through the drive shaft (601a) on the insert (602a). Due to friction between the rotating insert and the well casing wall (603a), heat is generated and the plastic material of the well casing wall (603a) begins to melt at the contact zone between the well casing wall (603a) and the edge (604a) of the insert (602a). Thus the insert (602a) melts through the well casing wall (604a) and creates a perforation. The part of the well casing wall (603a) melted out (605a) is retained in the insert (602a) and carried out into the gravel filled well casing annulus (606a).

F'g- 7a. As the insert (701a) protrudes into the gravel (702a) in the annulus surrounding the well casing (703a), retaining the melted out section (704a) of the well casing wall (703a), the rotating motion of the insert (701a) applied by the drive shaft (705a) cause the threading (706a) on the insert (701a) to cut into the well casing wall (703a) and secure the valve insert (701a) in the well casing wall (703a).

Fig. 8a.

When the valve insert (801a) is secured by its threading in the well casing wall (802a), the ball lock (803a) is released and the drive shaft (804a) retracted.

Fig. 9a. The magazine (901a) can then be moved up by the actuators (not shown) to position a new valve insert (902a) in front of the shaft. The preparation tool can then be released and moved to a new circumferential position within the well casing (903a), by retracting the hydraulic supports (See fig 2a) and turning the preparation tool.

Fig. 10a.

Valve insert (1001a) secured in well casing wall (1002a). The melted out section (1003a) of well casing wall (1002a) is retained in the front of the valve insert (1001a) in front of the ball valve (1004a) and the exit holes (1005a) of the valve insert (1001a) and located in the gravel (1006a) of the borehole annulus.

Fig. 11a.

Valve inserts (1101a) inserted in well casing (1102a) prepared for sealing at essentially same level (1103a). Here shown at a level at which a layer of clay (1104a) seals the aquifer (1105a) from surface water penetrating the permeable layers (1106a) above.

Fig. 12a.

Detailed view of well casing (1201a) prepared for sealing. Valve inserts (1202a) is secured in well casing wall (1201a) at essentially same level (1203a) and protrudes into gravel (1204a) in well casing annulus. Water (1205a) is running down through the gravel filled borehole annulus and may contaminate the well.

Fig. 13a.

A sealing tool (1301a) is inserted in the well casing (1302a) such that the area (1305a) between the two sealing units (1303a) is covering the level (1304a) of the circumference of the well casing (1302a) at which the valve inserts (1306a) are placed. The sealing tool (1301a) is carried by a suspension system (not shown) and the two sealing units (1303a) are expanded by hydraulic pressure to seal of the volume of well casing (1302a) at which the valve inserts (1306a) are placed.

Fig. 14a. A Bentonite slurry or other sealing filler is pumped through a hose (not shown) and through the tube (1401a) and into the volume (1402a) between the sealing units (1403a) within the well casing (1404a).

Fig. 15a. As the pressure of the sealant increases within the volume (1501a) between the sealing units (1502a), the ball valves in the valve inserts (1503a) opens and any water trapped within the sealed of volume (1501a) and the Bentonite slurry flows out into the porous zone of the borehole annulus (1504a), filling all the voids and forms a sealing (1505a) of the well casing (1506a) in an area around the insert (1503a).

Fig. 16a

When the voids in the porous zone of the borehole annulus (1601a) have been filled with slurry (1602a), back pressure increases as slurry is pumped in. When back pressure reaches near inlet pressure in the valve inserts (1603a), or inlet pressure is reduced because required volume has been injected, the ball valve (1604a) close. Water (1605a) is now prevented from passing.

Fig. 17a.

The hydraulic pressure of the sealing units (1701a) can then be released whereby the diameter of the sealing units are slightly reduced, at the sealing tool can be extracted from the well casing (1702a). Some sealant in the volume between the sealing units may be washed out during the extraction, but the limited amount of sealant in the sealing tool does not present a risk of clogging the filter (1703a) of the well.

Fig. 18a. After sealing (1801a) the surface water running down through the gravel in the borehole annulus (1802a) and the surface water running through the permeable layers in the ground and entering the aquifer (1803a) through "cracks" in the isolating layer (1904) adjacent to the borehole (1805a) is now prevented from reaching the aquifer (1803a).

Fig. 19a.

Figure 19a shows a cross section of the well at sealing level (1901a) prior to sealing (A-A 1) and after sealing (A-A 2). Prior to the well establishment, pollution of the water in the aquifer (not shown) from layers above and at ground surface (not shown), is prevented by the presence of an isolating layer (1902a) of clay, rock or other layers impermeable to water. When establishing a well, a borehole (1903a) is introduced to gain access to the water of the aquifer (not shown). A well casing (1904a) is placed within the borehole (1903a) to allow the water of the aquifer to be pumped up. This leaves an annulus between the borehole (1903a) and the well casing (1904a) to be filled to prevent direct access of pollutants from ground level to enter the water of the aquifer. In the cross sectional view A-A 1 of the well area prior to sealing, the annulus is filled with gravel (1905a) or other material allowing water to travel from ground surface level through the gravel filled annulus (1905a) to the aquifer. Sealing has been prepared by insertion of valve inserts (1906a) to allow sealing of the gravel filled annulus (1906a).

In the cross sectional view A-A 2, the well is shown after sealing. The circumferential distributions of valve inserts (1906a) has allowed a uniform distribution of sealing material

(1907a) in the borehole annulus and seals the lower layers from the upper layers and prevent pollutants to travel through the borehole annulus and reach the aquifer.

Fig. 20a. If one or more hydraulic connections are lost during preparation, a situation may occur where a valve insert (2001a) is partially inserted, but the drive unit (2002a) is no longer able to apply force and/or rotation o the drive shaft (2003a) to fully insert and secure valve insert (2001a) in the well casing wall (2004a). Since loss of hydraulic pressure may also prevent the drive unit (2002a) to be able to pull the partially inserted valve insert (2002a) back out of the well casing, either because the ball lock (2005a) can no longer be maintained engaged and/or the drive unit (2002a) and drive shaft (2003a) can no longer be forced back due to lack of hydraulic pressure for the sub-frame actuator (not shown). The preparation tool then needs to be extracted from the well casing (2004a) to have the failed hydraulic connections re-established. However, the partially inserted valve insert (2001a) is in the way of the insert magazine (2006a) during extraction.

Fig. 21a.

During extraction of the preparation tool due to failed mechanic or hydraulic connections, the magazine (2101a) may collide with a partially inserted valve insert (2102a) that cannot be removed before preparation tool has been extracted and repaired. By securing the magazine only with a spring loaded ball lock (see fig. 5b), the magazine (2101a) is able to slide out of the preparation tool when forced to do so by colliding with the partially inserted valve insert (2102a) during extraction of the preparation tool. The magazine can be attached to the preparation tool with a wire to ensure recovery of the magazine (2101a) as well, when the preparation tool (2003a) is extracted.

Fig. 22a. During preparation by insertion of valve inserts in the well casing wall (2201a), the valve insert (2202a) to be inserted has melted through the well casing wall (2201a), but collides with ad obstacle (could be a large part of rock or other immovable and impenetrable material). This obstacle (2203a) prevents the valve insert (2202a) from being fully inserted and secured in the well casing wall (2201a). Fig. 23a.

The valve insert (2302a) that failed to be correctly inserted in the well casing wall (2301a) due to an obstacle (2303a) is pulled out of the well casing wall (2301a) by the sub-frame actuator (not shown) pulling the sub-frame (not shown) carrying the drive unit (not shown) with the drive shaft (2304a) back. The ball lock mechanism (2305a) allows the valve insert (2302a) to be pulled out of the well casing wall (2301a) by the Drive shaft (2304).

This situation presents a major risk in the well sealing preparation process, since the well casing wall (2201a) is now perforated by the valve insert (2202a) and surface water with pollutants can potentially enter the well casing, which is in essence what the intended sealing should prevent and furthermore, well water will leak from the well casing if not repaired prior to use of well.

Fig. 24a.

The magazine (2401a) is moved up by the magazine actuators (not shown) and the valve insert (2402a) that penetrated the well casing wall (2403a) is placed in the position from which is came in the magazine (2401a). Note the melted out section (2404a) of the well casing wall has been removed from the penetration area of the well casing wall (2405a) and is retained in the valve insert (2402a). The ball lock mechanism (2406a) is released and the drive shaft (2407a) can be retracted to allow movement of the magazine (2401a).

Fig. 25a.

The magazine (2501a) is moved up by the magazine actuators (not shown) and the drive shaft (2502a) is moved forward to engage with a plug insert (2503a) in the magazine (2501a). The ball lock mechanism (2504a) is engaged to attach the plug insert (2503a) to the drive shaft

(2502a) and the drive shaft (2502a) and the plug insert (2503a) can now be retracted to allow movement of the magazine (2501a). Fig. 26a.

The drive shaft (2602a) is moved forward towards the well casing wall (2603a) while rotating; thereby ensuring the plug insert (2603a) is secured in the well casing wall (2601a) by the threading of the plug insert (2603a).

Fig. 27a.

When the plug insert (2703a) is fully inserted and secured by its threading in the well casing wall (2701a), the plug insert (2703a) is released from the drive shaft (2702a) by releasing the ball lock mechanism (2704a) and the drive shaft (2702a) can be retracted. The preparation tool can now be moved to a new circumferential position to insert a valve insert.

Fig. 28a.

The plug insert (2803a) seals the penetration (2804a) in the well casing wall (2801a) from the failed insertion of a valve insert due to the obstacle (2802a). When valve inserts have been inserted at other circumferential positions and sealant injected through these, the plug insert (2803a) in the well casing wall (2801a) will be further sealed from the outside, when sealant (2805a) from both sides of the plug will meet and filled the volume outside the plug.

Preferred embodiment.

Examples of preferred embodiments of the claimed invention are described in details in the following, with reference to illustrating figures.

Fig, lb. Fig. lb provides an overview of the components in a preferred embodiment of the claimed invention. The components are attached either directly to each other or to a supporting structure (not numbered). The apparatus is suspended in a wire (not shown) and connected to hoses providing hydraulic pressure and providing Bentonite slurry for sealing purposes. None of the hoses are shown in fig. lb.

At each end of the apparatus, a support unit is fitted. The support units consists of pads (101b) to provide friction against the inner surface of the well casing and cylinder units (114b & 119b) in which pistons (113b & 120b) can be hydraulic or pneumatically actuated to apply force in radial direction inside the well casing through the adjustable pads (112b). These pads (112b) can be replaced and thus adapt the apparatus to different diameters of well casings. Below the upper support unit, a hydraulic motor (102b) is positioned. The hydraulic motor (102b) drives a cogwheel (104b) and through a chain (103b) the cock wheel (107b) on the drive shaft (116b). The main part of the apparatus is placed in some distance for the hydraulic motor (102b) to get some length of the chain (103b) to allow sufficient travel distance of the sub-frame (108b). The main part or body of the apparatus is mechanically fixed to the hydraulic motor and the upper support unit through the structural elements (105b), which could be metal bars or composite bars, such as fibre glass or carbon fibre bars.

The sub-frame (108b) carrying the drive shaft (116b) slides on a guide (109b) and is actuated by a hydraulic cylinder/piston unit (106b), that also acts as an upper linear guide for the sub- frame (108b). To prevent jamming, a torsion bar stabiliser (111b) is connected to the upper and lower part of the sub-frame (108b) by sub-frame carriers (110b) and linked to the structural frame of the apparatus.

The purpose of the sub-frame (108b) is to provide the linear motion of the drive shaft (116b) to carry the inserts and plugs (117b) out of the magazine (118b) and into the well casing wall, where the drive shaft (116b) provides the necessary rotational movement of the insert or plug. The magazine (118b) contains both inserts and plugs (117b). A plug or insert (117b) is positioned in front of the drive shaft by use of the magazine actuator mechanisms (115b) on each side of the magazine.

Fig. 2b. In fig. 2b a cross sectional view of a preferred embodiment of a sealing tool unit is shown. The sealing tool unit is placed in position within the well casing by use of external means of positioning (not shown). Such external means can be wire systems, connectable sections of rods and pipes, crawlers and other remote controlled manipulators. External means of positioning are attached to the structure member (201b) that is attached to the combined structure member and manifold (204b). A hydraulic hose (202b) connected to a pump (not shown) supplies manifold with hydraulic pressure. Further into the manifold (204b) is a fitting (203b) to be connected with a hose for sealant supply (not shown). The fitting is in open connection with the hollow connecting member (212b), that connects the manifold (204b) with the upper expansion unit (213b) and the lower expansion unit (214b).

From the manifold (204b) the hydraulic pressure supplied to the manifold (204b) through the inlet (202b), is split into the outlets (205b) inside the upper expansion unit (213b) and through a hydraulic hose (206b) inside the connecting member (212b), into the outlet (210b) in the lower expansion unit (214b). By applying pressure to the inlet (202b), pressure is applied to the volumes (207b and 211b) of the upper and lower expansion units (213b and 214b) and the diameter of the expansion units increase and seal against the inner surface of the well casing (not shown)

Sealant can then be pumped into the inlet at the fitting (203b) and through the hollow connecting member (212b) in the channel (208b) also containing the hydraulic line (206b) for the lower expansion unit (214b) and out of the outlet (209b). Thus the volume limited by the expansion units (213b and 214b), the connecting member (212b) and the inner surface of the well casing (not shown) can be filled with sealant under pressure.

Fie- 3b.

The preferred embodiment of a valve insert consists of an essentially cylindrical insert housing (313b), in which a valve seat (304b) is made. In one end a number of "wings" (301b) between which the wings of the drive shaft (not shown) will fit and enable rotational force and movement to be transmitted in both directions from drive shaft to insert. A ball groove (302b) is placed at the base of the "wings" (301b) to engage with balls of ball lock of drive shaft (not shown), as to allow transmission of force from drive shaft to insert in both directions along the axial line of the insert.

The outer diameter of the insert housing (313b) is slightly increased towards the end designed to engage with the drive shaft, to make a tight fit with the well casing.

At the end of the insert housing (313b) opposite the end designed to engage with the drive shaft, the thickness is reduced and the edge (311b) rounded to decrease contact area between insert and well casing, to increase pressure and thus friction and heat generated. The rounded edge has a short cone-shaped section (314b) to guide the majority of the melted plastic material of the well casing wall into the cylindrical cavity (310b). Within the cylindrical cavity (310b) is a small recess (312b) in which some of the melted plastic material will cure and thereby secure the melted out section of well casing wall material contained in the cavity (310b). In the bottom of the cavity (310b) a plate (307b) is placed and secured by a Seeger ring (308b) or similar. The purpose of the plate (307b) is both to prevent melted plastic in the cavity (310b) to enter the valve or block the exit-holes (309b) in the insert housing (313b) and to provide a base for the valve spring (306b) that closes the ball (305b) with the valve seat (304b).

Fig. 4b.

The drive shaft (401b) is fitted with a groove (409b) that is in hydraulic connection with an inside channel (403b) of the drive shaft (401b) though the hole (402b). Hydraulic pressure can be applied to compress the spring (405b) through the piston (404b). The coned shape of the piston end opposite the end subjected to the pressure in channel (403b), cause the ball (408b) to be forced out against its seat in the mating part of the drive shaft (407b) to fit inside the coupling end of the inserts (not shown). Thus when fitted in an insert, the balls (408b) and the "wings" of the sleeve (410b) will create a locked coupling between insert (not shown) and drive shaft in both axial and rotational direction.

When hydraulic pressure at (402b) and subsequently in channel (403b) is reduced, or if pressure is lost by failure or leak, the spring load (405b) acting between the piston (404b) and the end cap (406b) will cause ball lock to release between insert (not shown) and drive shaft. Fie- 5b.

The structure (501b) of the preparation tool is designed to accommodate a magazine (502b) such that the magazine (502b) is able to slide up and down within the structure (501b). The magazine (502b) contains compartments (503b) for storage of both valve inserts and plug inserts. Along one or both sides of the magazine, notches (504b) mark positions where a compartment (503b) is aligned with the drive shaft (not shown). A spring (505b) applies force to a ball (506b) made of steel or other suitable material, inside a housing preventing the ball to drop out. The spring (505b) is pre-loaded and compressed even more during movement of the magazine (502b) and acts as a ball lock with the notches (504b) in the side(s) of the magazine (502b). This spring loaded ball lock mechanism keeps the magazine in position and allows the preparation toll to be pulled up, even if an insert is only partially inserted and blocks passage of the magazine (502b). Upon collision with partially inserted insert, the magazine (502b) will simply be forced down relative to the upwards moving preparation tool structure (501b) and the spring (505b) of the ball lock mechanism will allows the ball (506b) to disengage from the notch (504b) the ball (506b) is resting in. The lower support of the preparation tool is designed to allow the magazine to slide out underneath the preparation tool. The magazine (502b) can be secured by a wire to the structure, so when the magazine (502b) slides out of the structure completely, it doesn't drop to the bottom of the well, but remains attached to the structure (501b) and can be refitted in the structure at ground level.

Fig. 6b.

To move the magazine (610b) between the positions at which a compartment is aligned with the drive shaft (not shown), the preparation tool is equipped with two magazine actuators, one for each direction (up/down). On each side of the magazine (610b) a number of teeth (601b) cut out. These teeth are tilted downwards on one side (601b) and upwards on the opposite side of the magazine (610b). A tooth (602b) with an opposite tilt is attached to the actuator, such that the tooth (602b) can slide off a tooth 601b) of the magazine (610b) if moved in the magazine tooth (601b) tilt direction (here down) and engage with the tooth (601b) of the magazine (610b) if moved opposite the tilt direction of tooth of the magazine (610b) (here up). The Tooth (602b) of the actuator is attached to the actuator arm (604b) through at rotational joint (605b) and a spring (603b) between the actuator arm (604b) and the tooth (602b) ensures that the tooth (602b) will engage with opposing teeth (601b) of the magazine (610b) if possible. A tooth carrier (606b) allows the actuator tooth (602b) to rest without risk of engaging with the teeth (601b) of the magazine between magazine

movements. This ensures the ability of the magazine (610b) to slide out of the preparation tool in case a partially inserted insert blocks the way of the magazine (610b) if the preparation tool has to be pulled up from the well. The actuator arm (604b) is attached to a piston rod (607b) of a hydraulic actuator (608b). A second hydraulic actuator (609b) controls a similar magazine actuation mechanism on the other side of the magazine (610b) for actuation of magazine motion in the opposite direction.

Fig. 7b.

In fig. 7b different stages of insertion and removal of a valve insert is shown for a valve insert with a retaining recess as disclosed by the invention and a potential problems related to the use of valve inserts not having such a retaining recess is illustrated, to illustrate to purpose of the retaining recess. A valve insert (701b) is forced against the inside of a well casing wall (702b) while rotating. The friction between the rotating valve insert (701b) and the well casing wall (702b) cause the front end of the valve insert (701b) and the adjacent well casing material (703b) to heat up and a thin layer of well casing wall material begins to melt (703b) due to the heat. At stage (I) the valve insert (701b) has melted its way halfway through the well casing wall (702b). Due to the cooling of the water surrounding the valve insert (701b) and the inner surface of the well casing wall (702b), only a very thin boundary layer (703b) between the vale insert (701b) and the well casing wall (702b) melts.

At stage (II) the valve insert has melted its way almost through the well casing wall and the melted layer of material almost reach the outer surface of the well casing wall. As the melted layer gets near to the outer surface, the mechanical strength of the little remaining material (704b) connecting the well casing wall material inside the valve insert (707b) with the well casing wall (702b) outside the valve insert is reduced both due to the limited thickness and the increased temperature. The force applied by the valve insert cause plastic deformation of the thin connecting material to occur. Meanwhile the molten material inside the valve insert flows into the recess of the valve insert (705b). At stage (III) the material left has been so weakened, that the part of well casing wall material connecting the piece of material inside the valve insert (707b) with the surrounding well casing wall deforms further and snaps (706b) and the part of well casing material inside the valve insert (707b) starts to follow the rotating motion of the valve insert. Since there is no longer any relative movement between the plug of material (707b) inside the valve insert and the valve insert, the molten material in the recess of the valve insert (75b) cools off and hardens.

At stage (IV), the valve insert has penetrated the well casing wall and the part of the well casing wall melted out (707b) is retained within the cavity of the valve insert. The deformed edge (708b) of the outside of the penetration results in a slightly reduced diameter of the penetration, whereas the deformed edge (709b) of the melted out plug (707b) retained in the valve insert results in a slightly increased diameter of the melted out section (707b) at the outer end. Since the increased outer diameter section does not have to pass the reduced inner diameter during further protrusion of the valve insert, the valve insert can now be screwed in and secured in the well casing wall (702b) by the valve insert threading, by further applying force and rotation on the valve insert.

The details of stages (l)-(IV) are identical if using valve inserts without a retaining recess. If however the valve insert retaining a plug of well casing wall material has to be retracted due to an obstacle on the outside of the well casing preventing fully insertion and securing the valve insert by its threading, there is a significant difference between the behaviour of a valve insert with a retaining recess and a valve insert without a retaining recess.

If trying to pull out a partially inserted valve insert (stage V) with a valve insert without a retaining recess, the increased diameter of the plug of material at the outer edge (709b), where the material was deformed and pulled from the well casing wall, may collide with the slightly reduced diameter at the outer edge of the penetration (708b), due to the deformation that lead to the material to snap (706b). The force required to overcome this obstacle of the necessary elastic deformation of the edges (708b and 709b) for the edges to pass each other may be larger than the friction between the plug of material (707b) and the inner surface of the cavity of the valve insert (710b). If so, the plug (707b) is pulled out of the valve insert (710b) and remains in the penetration when the valve insert is pulled back. This means that now the well casing wall is now open for the potentially polluted water on the outside of the well casing, which it was the purpose to prevent access to the well by the preparation and later sealing. Thus the situation is now actually worse than prior to the beginning of the preparation procedure.

Since the valve insert (710b) was pulled out because of an obstacle on the outside of the well casing preventing insertion of the valve insert (710b), a plug insert cannot be installed by pushing out the plug (707b) of the penetration.

The obstacle if the edges (708b) and (709b) colliding and having to deform to pass each other may also cause a partial slip (711b) between the melted out section (707b) and the inner surface of the valve insert cavity (710b) as shown in the upper part of VI. Such a slip (711b) results in the combined length of the valve insert (710b) and the melted out section (707b) is increased by the length of the slip (711b). This situation increases the necessary distance the drive shaft (not shown) has to be retracted to allow the magazine (713b) to pass in front of the valve insert (710b) containing the melted out section (707b). (The magazine (713b) is shown schematic and out of proportions to allow more important details to be visible in the illustrations). In smaller well casing diameters, a sufficient increase in retraction of the drive shaft (not shown) may not be possible and the increased combined length (711b) of the valve insert and melted out section (707b) retained within the valve insert (710b) caused by the slip between the two, may result in the clearance (712b) between the well casing wall (702b) and the front of the melted out section (707b) retained in the valve insert (710b) being insufficient for the magazine (713b) to pass in front of the melted out section (707b). The magazine (713b) can then not be moved up and allow the valve insert (710b) retaining the melted out section (707b) to be placed and stored in the magazine (713b) and a plug insert taken from the magazine (713b) to plug the penetration in the well casing wall (702b). Thus, the preparation tool needs to be taken to the ground surface to have the valve insert (710b) retaining the melted out section (707b) removed. It may then be impossible to refit the preparation tool in the necessary position to fit a plug insert in the penetration, given the depth at which the penetration may be located, the required reposition accuracy and poor visibility that can be the situation.

In both situations (V and VI), the well casing may have to be renewed by making a new and bigger borehole to remove the damaged well casing and the borehole annulus or the well has to be closed along with other wells producing water from the same aquifer. Both options will introduce a significant increase in costs and the latter furthermore result leave the water reservoir useless and polluted.

When using a valve insert with a retaining recess, the molten material hardened in the recess significantly increase the force able to be transmitted from the valve insert (714b) to the plug of material (707b), since it is no longer only depending on friction between the surfaces, but now requires deformation of the plug of material (707b) and/or the valve insert (714b) for the part of the plug with increased diameter (in the recess) (715b) to pass the area in front with regular (and smaller) diameter (716) of the valve insert (714b). The valve insert (714b) with a retaining recess is hence able to pull the plug of material past the point where the increased diameter edge of the plug of material (709b) collides with the reduced diameter edge of the penetration (708b) and back out through the penetration of the well casing wall (702b). The valve insert (714b) can then be replaced by a plug insert (not shown) and the integrity of the well casing wall (702b) restored.

Insertion of a new valve insert can then be attempted at a different circumferential location and the preparation process finalized and the sealing process subsequently performed.

While the invention as herein shown and disclosed in detail is fully capable of solving the stated tasks and providing the advantages hereinbefore stated, it is to be understood that this disclosure is merely illustrative of the presently preferred embodiments of the invention and that no limitations are intended other than as described in the appended claims.