EP2378055A1

EP2378055A1 - A method for the reconstruction of wells through the removal of the old casing by using a single reverse-circulation perforation and relative device

Info

Publication number: EP2378055A1
Application number: EP10425119A
Authority: EP
Inventors: Nicola Cempini; Stefano Chiarugi
Original assignee: Landi Di Stefano Chiarugi & C Sas; Acque Ingegneria SRL
Current assignee: Landi Di Stefano Chiarugi & C Sas; Acque Ingegneria SRL
Priority date: 2010-04-14
Filing date: 2010-04-14
Publication date: 2011-10-19

Abstract

The present invention refers to an innovative method for the maintenance/reconstruction of a well (1) through only one fluid reverse-circulation perforation and the relative device.

In accordance with the method, a drilling device (3) is arranged on a well driller machine (20) comprising a perforating tube (4) provided with one or more cutting utensils (6, 6'). The perforation of the ground is then carried out in such a way as to dig a circular crown (11) substantially concentric to the well. At the same time, the descending of a delivery flow by gravity into the circular crown (11) in formation takes place with the contemporary aspiration along the tube (4) in such a way as to aspirate all the detritus existing around the old pipeline.

The cutting utensils are arranged in such a way that, during all the perforation, the circular crown dug has such a diameter D as to entirely contain inside it the aggregate material (16, 17) arranged around the old well casing.

It is therefore possible to realize in this way the perforation in a single sinking.

Description

Technical Field

The present invention concerns the technical field relative to the construction and the maintenance of water wells.
In particular, the invention refers to an innovative device for the reconstruction/maintenance of a well and the relative method.

Background Art

It is known that the construction of a well implies the overcoming of significant problems, both technical and bureaucratic ones. The construction of a well indeed requires an accurate geological research in order to identify the ground water and therefore the site where the constructive work is to be carried out. However, it is not possible either to foresee or to move the selected zone and, on the basis of its location, it could require a long legislative action in order to overcome some bureaucratic obstacles.
First of all, it is necessary to proceed with an expropriation of the area of interest if it belongs to a private citizen. It is well known how each private citizen accepts unwillingly such an imposition, even if remunerated, and the whole means always a delay in the beginning of the execution of the work, as well as the need to afford various costs of legal nature by both parties.
Moreover, the creation of a well always imposes strong legislative restrictions for a wide surrounding area. Such restrictions should always be evaluated carefully and they are often so constraining as to lead to conclude that it is better to renounce to the construction of the well. An example of this is the prohibition to use manures and fertilizers of chemical type that may result harmful for human health. It is clear that such a prohibition is imposed to avoid the risk of pollution of the ground water, which is reached through the well. In that sense, if the well is destined to be created in an area destined for cultivation, such a prohibition can even lead to the final decision of renunciation to the well. In fact, an industrialized agriculture cannot in any way renounce to such productive techniques, since the penalty of such renunciation would be the incapacity of placing competitive productive volumes on the market.
Bearing in mind what has been stated before, it results clear that the identification of an efficient maintenance technique that allows to lengthen the life of the well as much as possible in an economical and advantageous manner is of utmost importance. It is in fact known, currently, that the wear of all the structural parts constituting the well render it exploitable for no more than about twenty years.
Currently, the "reconstruction" techniques of a well are in fact so costly and at the same time uncertain as regards the result that it is often even preferred the identification and realization of a new well.
A first known technique foresees the use of a coring device, provided with rotating blades or cones for the drilling of the ground, the length of such a device being much inferior with respect to the overall length of the well. Such a device is therefore able to drill the ground concentrically with respect to the well, thus detaching a circular crown of material that covers the casing of the well for the possible overall sinking length of the coring device, realizing at the same time a communication channel (always in the shape of a circular crown) external to the bell of the coring device. With the reverse-circulation perforation technique, a descending liquid flow is injected outside the coring device and it is caused to rise in the crown of material that covers the well casing. In such a manner, the rising flow drags all the material, making it come to light again. Subsequently, the cut of the portion of freed well casing can be carried out, repeating the operation until recovering all the overall length of the well casing and of the filters that constitute the framework of the well.
As per what has been described, it is clear how the main technical inconvenience of this system concerns precisely the configuration of the coring device used, which allows only a partial penetration. In that sense, it is required to proceed by "steps" with partial penetrations followed by cut of portions of casing, the whole meaning a significant waste of realization times and costs.
In order to avoid a regeneration of the well through a succession of coring operations for all the depth of the well, a second technique has therefore been thought of consisting in the execution of a coring by means of a coring device provided with a tube able to cover continuously the hole of the well beyond the depth of the well. The same old well casing therefore remains inside the big coring device to be then recovered when the pre-established depth is reached. Subsequently, the hole is bored or cleaned to eliminate the detritus still present in it.
Nevertheless, such a coring tube is anyway configured in such a way as to perforate a circular crown of material of a diameter only a bit larger than the well itself. As a consequence, the coring device, during all the perforation, always maintains itself in proximity of the well, penetrating deep through the aggregate material that surrounds the well by its length, that is the cementing and the underlying gravel pack. In such a manner, a "bearing" effect is inevitably created due to the physical features of such a casehardening and of the gravel pack by which, once a certain perforation direction (vertical) is set, it is not possible to vary its trajectory. In addition, also the high structural rigidity of such a tube contributes to significantly increase the guidance difficulties during the perforation.
All this implies a great risk of interception of the old well casing, which often results not perfectly perpendicular with respect to the ground plane. It is therefore clear how also slight deviations of the well casing translate anyway into several centimetres of deviation from the vertical when the well is deep. In that case, the risk of interception of the well during the perforation is very high and, once the coring device intercepts the well casing, it makes an accidental transversal cut that wholly compromises the maintenance operation.
It is therefore necessary to abandon the well when the work is not finished yet (also because the old drainage blanket is not totally intercepted) and to proceed with the construction "ex novo" of another well. It is clear how such an extreme condition implies a huge loss of time and money.
In accordance with such a technical solution, in order to reduce to the minimum the risks of interception of the pipe, it is therefore necessary to foresee a perforation in at least two subsequent phases.

Brief description of the invention

It is therefore the aim of the present invention to provide a device and relative method for realizing a work of maintenance/reconstruction of a well that solves at least in part the above-mentioned inconveniences.
In particular, it is the aim of the present invention to provide a drilling device for the realization of a work of reconstruction of a well that reduces to the minimum the risks of interception of the well itself during the operation of perforation, guaranteeing at the same time the total removal of the drainage layer of the old well.
It is also the aim of the present invention to provide a drilling device that allows a perforation that is quick, precise, and therefore economical.
These and other aims are reached with the present drilling device 3 for the reconstruction of a well 1 in accordance with claim 1.
The well (1), in accordance with the background art of realization, is provided with a well casing (2) installed in the ground surrounded by a aggregate material (16, 17) that extends in depth on a part or on the whole length of the well itself. The drilling device (3) therefore comprises a tube (4) provided with one or more cutting utensils (6, 6') to realize the sinking concentrically to the well.
In accordance with the invention, the cutting utensils (6, 6') result configured in such a way as to dig when in use a circular crown (11) substantially concentric to the well, the said circular crown having an external diameter D of length such that the fixing aggregate (16, 17) results wholly arranged substantially inside of the external perimeter (11') of such a circular crown (11).
In other words, the perimeter that delimits the aggregate is contained in the perimeter 11 of the circular crown realized.
In such a manner, the tube 4, during all the sinking of it, does not penetrate moving itself inside the said aggregate material, but it totally removes the aggregate material thanks to the wide area of action of the blades. The bearing effect of the ground is therefore significantly reduced and the manoeuvrability of the device results greatly enhanced. In such a manner, the technical problem related to the potential risk of interception of the old well casing is solved.
It is therefore possible to realize a fluid reverse-circulation perforation in only a single step, the whole with a significant advantage as regards reduction of realization times and costs.
Advantageously, the aggregate material (16, 17) can be arranged around the well in such a way as to form a circular crown of a diameter D' minor with respect to the said external diameter D.
Advantageously, one or more flanged rods (5) can be provided, connectable in a removable manner to the tube (4) in such a way as to vary the overall length of the drilling device (3).
Advantageously, the perforating utensils can comprise fixed blades (6, 6').
Alternatively, the perforating utensils can comprise rotating cones (6, 6').
Advantageously, the diameter D of the circular crown (11) can be comprised between the 900 millimetres and the 1000 millimetres, preferably 1000 millimetres.
Advantageously, the diameter D' of the aggregate is contained within the 700 and the 800mm.
Advantageously, the height H of the drilling device can be comprised between 2,5 metres and 3 metres, and preferably 3 metres.
It is also here described a well driller machine (20) comprising a drilling device (3) as described.
Advantageously, the well driller machine is provided with a tilting top-head driver to which the drilling device (3) described can be connected.
Advantageously, an aspiration group (7, 8) is further provided with for causing the descent by gravity of a washing fluid into the circular crown (11) and the contemporary aspiration of the said fluid along the tube (4) of the drilling device (3).
Last, it is here described also the relative method for the maintenance/reconstruction of a well (1) comprising a well casing (2) installed in the ground and surrounded by an aggregate material (16, 17).
The method therefore comprise the operations of:

Arrangement on a well driller machine (20) of a drilling device (3) comprising a perforating tube (4) provided with one or more cutting utensils (6, 6');
Perforation of the ground in such a way as to dig a circular crown (11) substantially concentric to the well and contemporary descending of a delivery flow into the circular crown (11) in formation with aspiration along the pipe (4).

In accordance with the present method, the perforating operation is controlled in such a way that the dug circular crown (11) results with an external diameter D such that the aggregate material (16, 17) is arranged entirely inside the external perimeter (11') of the said circular crown (11).
In such a manner, the perforation results well controllable and the risk of interception of the well casing is cancelled.
It is therefore possible now to realize the perforation in a single sinking.
Advantageously, the operation of application of a collection container (12) arranged on top of the well (1) is further foreseen, to collect the heavy detritus that is not aspirated.
Last, advantageously, at the end of the perforation, the following operations are foreseen:

Removal of the old well;
Insertion of the new casing of the new well;
Completion of the new well.

Brief description of the drawings

Further features and advantages of the present method and of the relative equipment, according to the invention, will result clearer with the description that follows of one of its embodiments, made to illustrate but not limit, with reference to the annexed drawings, wherein:

Figure 1 represents the configuration of an ordinary well of which to carry out maintenance work;
Figure 2 represents in section the drilling device 3 in accordance with the invention;
Figure 3 represents the drilling string 10 mounted on a well driller machine 20 of a well;
Figures from 4 to 6 represent maintenance phases in accordance with the present method;
Figure 7 represents the final phase of removal of the old well;
Figure 8 represents the reconstruction phase of the new well.

Description of one preferred embodiment

With reference to figure 1, a well 1 is schematically represented comprising a well casing 2 inserted in the ground in such a way as to convey the water of the intercepted ground water. Just for descriptive simplicity purposes, the said ground water has been omitted from the schematic drawing. The well casing 2, as it is well known, is surrounded, at least in part of its length, by an aggregate material, that is a cementing 17 and an underlying gravel pack 16 arranged in the deepest part of the well, below the cementing. Generally, the aggregate material (16, 17) is arranged around the well along its depth in such a way as to form substantially a circular crown indicated in section of figure 1 with an external diameter D'. Indicative values of such extension of the external diameter D' are of about 800 mm, even if such a reference value can be lower, with diameters of the well 1 particularly reduced, for example below the 400 mm. Always figure 1 shows the old filters 18 arranged at the bottom of the well, while a generic depth quota of the well is indicated with h.
Moreover, it is clear how, even if the simplest way to arrange the aggregate is substantially concentric to the well in accordance with the said circular crown, such a material could anyway be arranged around the well also according to various forms.
As shown in figure 2 and in the subsequent figure 3, a drilling device 3, also called rock-bit, comprises a tube 4 provided with an attaching-flange 5 for connecting the tube 4 to a drilling string 10. The drilling string 10, as per figure 3, is composed of one or more flanged rods 7 (axially holed) connectable among them through the flanges in such a way as to realize an extension of the drilling device 3 on the basis of the length of depth that wants to be reached. Such a realization feature of the drilling string through the connection of one or more flanged rods 7 gives it high flexibility and manoeuvrability, particularly when mounted on a well driller 20 with tilting top-head driver.
Always as shown in figure 2, the tube 4, on the opposite part of the attachment flange 5, supports one or more perforating utensils (6, 6') configured with a profile with rotating blades or rotating cones, depending on the basis of the characteristics of the ground to be perforated.
In accordance with the invention, the blades or the cones are arranged along the tube 4 and configured in such a way that, during all the perforation, they realize a circular crown, concentric to the well, with an external diameter D such that the aggregate of material (16, 17) results entirely arranged inside the external perimeter 11' defined by the said crown.
In the case of aggregate arranged in such a way as to realize a circular crown placed in adherence to the well, such a maximum perforating diameter D is pre-chosen in such a way as to result substantially greater with respect to the said overall diameter D' relative to the cementing 17 and to the underlying gravel pack 16 (see figure 1). In such a manner, the aggregate is entirely arranged within the limits of the dug crown.
The schematisation of figure 2 in fact shows a perforating utensil 6 (blade or cone) of an overall diameter D. The tube 4 is then provided with further one or more perforating utensils 6' with a progressively reduced diameter up to arriving to a diameter similar to the one of the well to be removed, in such a way as to detach a thin circular crown 9 of material in adherence to the well.
In such a manner, a very important double technical effect is obtained. The first effect refers to the fact that the drilling string results extremely flexible during the penetration since the wide blades or cones remove entirely all the crown of cementing 17 and the gravel pack 16 surrounding the old well 2. The "bearing" effect of the ground is therefore significantly reduced. In addition, a wide circular crown around the well results now wholly cleaned. As a consequence, during the digging all the materials placed between the tube 4 and the old perforation originally realized for the installation of the well are therefore able to be recovered, removing completely the artificial drainage layer.
In that sense, for the pre-established aims of the present invention, the diameter D is preferably, but not necessarily, of a value of about 1000 mm. The diameter d' of the cutting utensil 6' is chosen on the basis of the diameter of the old well to be recovered in such a way as to detach a crown of material 9 in adherence to the well of a very reduced thickness.
The external diameter d of the tube 4 is preferably a standard value of 368 mm or 406 mm.
The said diameter values (D; d; d') of the tube 4, together with the cutting utensils, can, if need be, take into account particular values of project in use in the realization of the wells and there in that sense eventually move away from the ones indicated before. Also the profile of the utensils can be of any form and nature. In any case, the dug perimeter contains inside the aggregate material.
The realization material of the flanged rods 7 and of the drilling device 3 is generally made of high resistance iron, while the thicknesses vary within a range of 8-10 mm. The overall length H of each flanged rod 7 and of the drilling device 3 does not result superior to three metres. Such constructive values, therefore, further contribute in rendering the drilling string 10 altogether extremely manoeuvrable.
Figure 3 represents schematically the well driller machine 20 on which the drilling string 10 is applied and comprising an aspiration group (7, 8), better described below. As always indicated in figure 3, the rotation direction of the arrow indicates the rotational direction of the drilling string 10 in such a way as to drill the ground. The double direction of the arrows vertical to the ground indicate instead a lifting/lowering direction of the tube to execute the drilling and lifting from the ground. The drilling string 10 allows the aspiration of the fluid and is connected to a flexible waste pipe of the detritus in the tanks.
Figures from 4 to 6 represent the outstanding phases of functioning of the method. Such figures, just for descriptive simplicity purposes, schematise the chisel 3 with an only lame 6 of diameter D.
In figure 4 an initial perforation phase is represented in which the rock-bit initiates its drilling of the ground in a substantially concentric manner to the old well casing 2. Just for descriptive simplicity purposes, figure 4 shows only a part of the overall length of the old well. In accordance with the figure the circular crown 11 is highlighted, of diameter D and with perimeter 11', realized concentrically to the well. The figure highlights well how the aggregate material (16, 17) during all the perforation phase results entirely arranged into the said diameter D. In such a manner, by increasing the diameter D in proportion to the width of are of the aggregate, the enhancement of the manoeuvrability of the device will be obtained.
Always figure 4 highlights the crown of material 9 that surrounds the well and detached from the utensil due to its grazing penetration in the well. In particular, the crown 9 results interposed between the cylindrical wall of the rotating tube 4 and the cylindrical wall of the well casing 2. Always figure 4 shows the remaining part of aggregate, which is intact because it has not been reached by the rock-bit yet.
At the same time that the digging phase is carried out, a fluid flow for washing is injected by gravity into the crown 11 in such a way as to clean all the existing detritus, included the removal of the said crown 9. The movement of the fluid (for example water), called reverse circulation, is caused through the said aspiration system (7, 8) comprising a centrifuge pump 8 with decompressor or more efficiently with a compressor of suitable capacity. In particular, the descending fluid delivery by gravity through the crown 11, is aspirated, for rising, along the conduit formed by the tube 4. In such a manner, always as shown in figure 4, all the residues mixed with the fluid are aspirated during the digging.
A collection container 12 is arranged on top of the well before the beginning of the digging operations. In such a manner, the most part of the material is aspirated while the excessively heavy macroscopic particles, which are not able to be dragged by the flow, are impeded from falling to the bottom of the well.
Figure 5 represents an intermediate digging phase in which the rock-bit is about to reach the bottom of the well while, at the same time, continues the fluid delivery and the aspiration. Always figure 5 shows some heavy detritus fallen into the container 12.
Figure 6 represents the conclusive digging phase in which the utensil reaches the bottom of the well to the quote h below old filters. The fluid delivery continues until the entire hole and the aggregate material has been substantially removed completely.
The great maneuverability of the rock-bit, thanks to a wide digging area that contained the aggregate entirely, therefore allows to realize the sinking with the contemporary washing in only one step, unlike the background art. The risk of interception of the old well casing is in fact absolutely avoided. In such a manner, the process results much more advantageous in terms of time and costs.
The subsequent figure 7 represents the digging phase of the old well once the washing phase is completed. At this point, a circumference of diameter D is obtained completely free from any form of detritus. As shown in figure 8, the reconstruction of the new well can now be carried out with the insertion of the new well casing 30, of the filters 31 and the laying of the gravel pack for the new drainage layer 34, together with the new cementing 35.

Claims

A drilling device (3) for the maintenance/reconstruction of a well (1) comprising a well casing (2) installed on the ground and surrounded by an aggregate material (16, 17), the said drilling device (3) comprising a perforation tube (4) provided with one or more cutting utensils (6, 6') for realizing the sinking concentrically to the well and characterized by the fact that the cutting utensils (6, 6') are configured in such a way as to dig, when in use, a circular crown (11) substantially concentric to the well, the said circular crown having an external diameter D such that the aggregate (16, 17) results entirely arranged inside the external perimeter (11') of the said circular crown (11).
A drilling device (3), according to claim 1, wherein the aggregate material (16, 17) is arranged around the well in such a way as to form a circular crown of a diameter D' minor with respect to the said external diameter D.
A drilling device (3), according to claim 1, wherein are provided, further, one or more flanged rods (7) connectable in a removable manner to the tube (4) in such a way as to vary the overall length of the drilling device (3).
A drilling device (3), according to one or more of the preceding claims from 1 to 3, wherein the perforation utensils comprise fixed blades (6, 6').
A drilling device (3), according to one or more of the preceding claims from 1 to 3, wherein the perforation utensils comprise rotating cones (6, 6').
A drilling device (3), according to one or more of the preceding claims from 1 to 5, wherein the diameter D of the circular crown (11) is comprised between the 900 millimetres and the 1000 millimetres, preferably 1000 millimetres.
A drilling device (3), according to one or more of the preceding claims from 1 to 5, wherein the diameter D' of the aggregate is contained within the 700 and 800mm.
A drilling device (3), according to one or more of the preceding claims from 1 to 5, wherein the height h of the drilling device is comprised between 2,5 metres and 3 metres, preferably 3 metres.
A well driller machine (20) characterized by the fact that it comprises a drilling device (3) according to one or more of the preceding claims from 1 to 8.
A well driller machine (20), according to claim 9, wherein the well driller is provided with a tilting top-head driver to which the said drilling device can be connected (3).
A well driller machine (20), according to claim 9 or 10, wherein the well driller machine (20) further comprises an aspiration group (7, 8) for causing the descent of a washing fluid into the circular crown (11) realized and the contemporary aspiration of the said fluid along the tube (4) of the drilling device (3) .
A method for the maintenance/reconstruction of a well (1) comprising a well casing (2) installed in the ground and surrounded by an aggregate material (16, 17), the said method comprising the operations of:
- Arrangement on a well driller machine (20) of a drilling device (3) comprising a perforation tube (4) provided with one or more cutting utensils (6, 6');

- Perforation of the ground in such a way as to dig a circular crown (11) substantially concentric to the well and contemporary descending of a delivery flow into the circular crown (11) in formation with aspiration along the tube (4);
and characterized by the fact that the said perforating operation is controlled in such a way that the circular crown (11) dug has an external diameter D such that the aggregate material (16, 17) results arranged entirely inside the external perimeter (11') of the said circular crown (11).
A method for the maintenance of a well (1), according to claim 12, wherein the said perforation is realized in a single sinking.
A method for the maintenance of a well (1), according to claim 12 or 13, wherein the operation of application of a collection container (12) is foreseen, arranged on top of the well (1) for collecting the non-aspirated heavy detritus.
A method for the maintenance of a well (1), according to one or more of the preceding claims from 12 to 14, wherein at the end of the perforation, the following operations are foreseen:
- Removal of the old well;

- Insertion of the new well casing of the new well;

- Completion of the new well.