FR2974141A1 - NON-DESTRUCTIVE DRILLING METHOD AND DEVICE - Google Patents

Abstract

The invention relates to a method for performing drilling in a non-destructive and large diameter drilling zone D1, comprising the steps of: a. perform a first guide bore, of diameter D2 less than D1, b. producing a cylindrical gap, of diameter D1, positioned in a controlled manner relative to the guide bore, delimiting a cylindrical zone of the drilling zone between the cavity and the gap, c. insert a containment basket into the circular gap, d. burst the materials constituting the cylindrical zone of the drilling zone, and e. extract the previously exploded material by evacuation of the containment basket. The invention also relates to a drill and a basket adapted to implement the method.

Description

FIELD OF THE INVENTION

The object of the present invention generally relates to the field of geological or geotechnical drilling, and particularly the field of core drilling of large diameters (diameter greater than 400 mm, for example between 600 and 700 mm) in clay rocks.

The invention can be implemented for any type of drilling, particularly for the study or the realization of very long-term geological storage of radioactive waste from spent fuel from nuclear power plants.

STATE OF THE ART

The radioactive waste considered in the context of the present invention is high-level long-lived waste (HAVL) having an average activity greater than one million Becquerels per gram for hundreds of thousands of years. Given this order of magnitude, deep storage is one of the possible solutions that can limit the risk of transfer of radioelements to populations, and generally a maximum of living organisms, for the duration of storage .

Potential storage locations include some very impervious rock layers in areas with stable geodynamics.

The storage of certain types of nuclear waste in these layers requires the realization of suitable boreholes, preferably of diameter between 600 mm and 700 mm, and the establishment of plugs which 30 ensure the sealing of boreholes containing packages waste, for example bentonite plugs. 1 In order to ensure a good seal, the geological layer surrounding the packages must be as undisturbed as possible (by creating cracks or other), and the techniques used for the drilling must preserve the sealing properties of the rock, and in particular avoid the creation of cracks in this geological layer. Indeed, the presence of cracks in the rock wall would deteriorate the impermeability that one wishes to preserve, and increase the risk of leakage of radioactive material.

However, there is no drilling in the state of the art to drill diameters as large - 600 to 700 mm - with a good finish of the walls, a low disturbance of the rock, and a recovery of the rock drilled at a moderate cost.

In fact, the drills used until now for large boreholes require the use of destructive drill bits. It is specified that in this text "destructive" means likely to damage the wall of the borehole (that is to say the inner wall of the cavity created by drilling). Non-destructive drilling instruments - which are known as coring tools - only concern diameters up to about 250 mm. An example of such an instrument is a core drill which comprises a corer with a crown for example diamond or tungsten, and an extractor which breaks the core at its base and allows its recovery.

Consequently, one of the aims of the present invention is to enable drilling of large diameter, that is to say of diameter greater than 400 mm, non-destructive, of good surface finish and allowing the reduction of damage. of drilled material (eg, rock, concrete) for a low cost.

Another object of the invention is to make it possible to carry out a sampling by coring of materials constituting the drilling zone during the drilling, so as to be able to analyze said materials.

In this regard, the invention provides a method for carrying out drilling in a drilling zone, and of large diameter D1, comprising the steps of carrying out a first guide borehole, of diameter D2 less than D1, producing a cylindrical interstice, of diameter D1, positioned in a controlled manner with respect to the guide bore, delimiting a cylindrical zone of the drilling zone between the cavity and the gap, inserting a confinement basket into the cylindrical gap, bursting the materials forming the cylindrical zone of the drilling zone, and extract the previously exploded material by evacuation of the containment basket.

Advantageously, but optionally, the invention comprises at least one of the following characteristics: the guide bore is cylindrical, and concentric with the cylindrical gap, the diameter D1 is greater than 400 mm, and preferably between 600 and 700 mm, - the diameter D2 is between 60 and 100 mm, and preferably equal to 100 mm, - the first guide bore is made by coring, - the circular gap is made by sawing, - the guide borehole has a length equal to the desired length of the large-diameter borehole, during which the steps of making a cylindrical gap, inserting a containment basket, bursting the materials of the zone and extracting said materials until it is drilled desired length, - the method further comprises a step during which the bottom of the drilling of desired length is leveled.

The invention further proposes a containment basket adapted to be used during the steps of making a cylindrical gap, inserting a containment basket, bursting the materials of the zone and extracting said materials from the process according to the invention, the basket being able to deform plastically under the effect of shock waves generated by the material bursting step.

Advantageously, but optionally, the containment basket may further comprise at least one of the following features: it is able to deform radially outward - it is cylindrical in shape, and has a longitudinal slot all over its length.

Finally, the invention proposes a drill for carrying out drilling in a drilling zone, and having a large diameter D1, comprising: a means for producing a guide bore, of diameter D2 less than D1, means for producing a cylindrical interstice, of diameter D1, positioned in a controlled manner relative to the guide borehole, defining a cylindrical zone of the drilling zone comprised between the cavity and the gap, a containment basket, adapted to be inserted into the cylindrical interstice, - a spark gap, adapted to burst the materials of the cylindrical zone 25 of the drilling zone, and - a set of rods of adjustable length, and adapted to be fixed at least to the basket of containment to extract previously exploded material by evacuation of the containment basket.

Advantageously, but optionally, the drill according to the invention may also comprise at least one of the following characteristics: the drill further comprises a surfacer of diameter D1, adapted to flatten the bottom of a drill obtained with said drill, - The means for producing the guide bore is a core drill, - the means for producing the gap is a diamond crown - the diamond crown further comprises a centralizer, - the centralizer is cylindrical, concentric with the diamond ring, and suitable to be inserted into the guide bore.

DESCRIPTION OF THE FIGURES Other characteristics, objects and advantages of the present invention will appear on reading the detailed description which follows, with reference to the appended figures, given by way of non-limiting examples and in which: FIGS. to 1g represent the various steps of the method according to the invention, for sectional view of the wall of the drilling zone, axis YY defined in Figure 2. - Figure 2 shows a front view of the surface of the drilling zone, during the implementation of the method according to the invention. FIGS. 3a and 3b respectively represent, for perspective and right view, an exemplary containment basket used in the method and the device according to the invention. FIGS. 4a and 4b illustrate various embodiments of a diamond crown that can be used during the implementation of the invention. - Figures 5a and 5b schematically illustrate the operation of a type of spark gap that can be used in the method and the device according to the invention. - Figure 6 is a photograph of the drilling in progress.

FIGS. 7a and 7b are respectively perspective and side views of a surfacer that can be used during the process according to the invention.

DETAILED DESCRIPTION OF THE INVENTION Device used for drilling

According to the invention, a drilling 20 of diameter D1 of length L (see FIG. 1f), which is a few meters, for example of the order of 6 to 10 meters, will be produced in a drilling zone F. , see more. The diameter D1 is large, greater than 400 mm and for example between 600 and 700 mm.

The materials that can be drilled with the aid of the invention may be, by way of nonlimiting example, sedimentary rocks (argillite, limestone), crystalline rocks (for example granitic), or building materials (for example). example concrete).

To do this, a sender S is used on which one can attach a string of rods 16 (Figure 1c) at one of its ends. This drill is equipped with a rack to exert a thrust on the drill string to advance it. It is also able to rotate the drill string 16.

The drill can be a medium power drill. The Applicant has successfully used a Hilti DD750HY Drill. The invention only implements rock attacks on limited sections, thus making it possible to treat volumes of rocks or other important materials without necessarily involving the use of drills of very high power.

Limiting the leading section of the material also significantly reduces the generation of dust, especially in comparison with known destructive techniques. The drill string 16 can be lengthened when necessary by inserting an additional rod, for example when the rack reaches the stop, then the drill string is repositioned at the head of the rack and drilling continues. A drill string support is also provided to maintain it in the axis of drilling.

At the other end of the drill string 16, it is possible to attach various tools involved in carrying out the various steps of the method according to the invention. The assembly formed by the sander S and the tools used to carry out the process is a drill 1 according to the invention. Thus one can attach to the drill string 16 a core 11, allowing the realization and extraction of carrots of diameter D2.

It is also possible to fix a ring 12, comprising on its leading edge 20 of the material drilled a diamond portion for sawing said material. This ring 12 is of diameter D1, and thus makes it possible to make a gap or groove 22 in the material, of cylindrical shape and of diameter D1.

It is also possible to attach to the drill string 16 a spark gap 14, the actuation of which, when it is in a borehole, makes it possible to blow up part of the drilling zone against which it is located. This spark gap can be of any known type. Typically, and as illustrated schematically in FIG. 5, it may be a tool which comprises a jack 141 situated between two plates 142 forming an angle, the jack allowing its advance between the plates to move them apart in order to increase the angle between these two plates 142, which thus press the wall of the borehole in which the spark gap is located, and burst locally.

It is also possible to attach to the drill string 16 a containment basket 13 used for extracting the drilled rocks in the bore 20 of diameter D1. It is a metal structure, preferably having a cylindrical shape so as to be inserted into the gap 22 made by the ring 12. In addition, the basket 13 is preferably closed at its rear end 130 (the closest of the drill string 16), with the exception of: an opening 131 of diameter D2, made in this end to allow the insertion of the spark gap 14 into the guide bore 21 through the basket 13, and hanging tabs 132 of the drill string 16 (Figure 3b).

In general, the basket 13 is able to deform radially outward under the effect of pressure waves applied on its inner face. In a particular embodiment of the basket, in order to deform radially, the basket 13 has, as illustrated in FIG. 3a, a longitudinal slot 133 of width preferably less than or equal to 1 cm, and which preferably extends over the entire length from the basket 13.

In alternative embodiments, it is possible that the basket does not cover the 360 ° of the gap 22, but only an angular sector, and where appropriate the slot 133 is replaced by a wider opening, which can reach an opening angular of 90 °. This solution is better suited for hard ground, which can lead to significant deformation of the basket at the time of bursting. Alternatively, the basket may not cover the entire length of the gap 22, but only a portion.

Drilling

With reference to FIGS. 1a to 1g, the various steps of a method for producing, in a drilling zone F, a non-destructive drilling of given diameter D1 and length L according to the invention are represented.

1. Performing a guide bore Firstly, and as shown in FIG. 1a, a first guide bore 21 of diameter D2 is produced in the drilling zone F.

This guide bore is preferably made over the entire length L to be drilled. The diameter D2 of the guide borehole is smaller than the diameter of the borehole D1. D2 is preferably between 60 and 100 mm and more preferably equal to 100 mm. This guide bore will make it possible to progress the large diameter bore 20 by successive digs of portions 201 of diameter D1, illustrated in FIGS. 1b and 1c. This guide bore 21 can be made by the drill, fixed on the drill 1 through the drill string 16. This makes it possible to obtain a core of the material of the drilling zone F, allowing the analysis of the materials forming said drilling zone F. The guide bore 21 may be perpendicular to the wall P but this is not mandatory.

A gas, or water, can be used as drilling fluid. In some cases, it is preferable to use a gas to preserve the physico-chemical and mechanical characteristics of the drilling zone F. The gas employed may be air, argon or nitrogen. This embodiment then requires that the core drill 11 is also equipped with a gas injection system (not shown in the figures) typically consisting of a pump, a cooling system, a compressor and preferably an aspirator 9 dust generated by coring, whose mouth is preferably positioned on the surface of the drilling area.

In order to carry out the guide bore 21 over the entire length to be drilled, the drill string is progressively lengthened, by inserting additional rods, each time the rack of the drill S comes to a stop. The extracted core, and therefore this first guide bore 21, have a length of for example between 20 and 1000 cm, corresponding to the total length L of the borehole 20 of large diameter that it is desired to drill.

2. Realization of a gap of diameter D1 Then, with reference to Figures 2 and 1d, is hollowed in the drilling zone F a gap 22 of cylindrical shape, of diameter D1 equal to the diameter of the borehole that is desired, and preferably concentric with the guide bore 21.

This gap 22 is preferably made by sawing, by means of a diamond ring 12 as mentioned above. Thus, as indicated above, the leading section of the material is limited to the surface of the crown, which reduces the dust generated at the time of this step.

During the realization of the gap 22 with the diamond ring 12, preferably injects compressed air A into the borehole to evacuate the dust generated. For this, several embodiments are possible, as illustrated schematically in FIGS. 4a and 4b. Referring to Figure 4a, the ring 12 may have a full rear face 121 with the exception of an orifice arranged to be able to insert the compressed air supply A, whose path is illustrated by arrows. Thus, the air leaves the side of the front face 122 of the ring, and is discharged along the edges of the borehole. This allows to cool the leading edge of the crown 12, and to permanently evacuate the debris, which avoids any risk of blockage of the crown. In addition, and with reference to Figure 4b, the ring 12 may have, on its rear face 121, 123 openings, in addition to the compressed air injection port. The openings 123 allow the release of the rock or any other material in the ring 12 when necessary. It is also possible to plug these openings 123 when the ring 12 is not blocked, to improve the flow of air on the front face 122 of the ring, and thus to improve the cooling of the leading edge of the ring.

The length of the gap 22 thus produced is equal to that of the diamond ring 12, that is to say of the order of 50 to 60 cm.

According to a particular embodiment of the invention, it is possible to insert in the exploration bore 21 a centraliser 15 (not shown in the figures), which may be a reference integral with the diamond ring 12 and fixedly placed by relative to it (e.g., at its center), to ensure that the gap 22 has a defined position relative to the guide bore 21 (typically concentric), and that the distance between these two cavities be constant.

The guide bore 21 and the gap 22 delimit a cylindrical zone C of the drilling zone F, shown in FIG. 2. The following steps of the method according to the invention aim at extracting the materials constituting this zone C in order to obtain a hole 20 of diameter D1.

3. Formation of a first portion of the diameter of drilling Dl According to a preferred embodiment of the invention, the materials forming the cylindrical zone C are exploded. To do this, a spark gap 14 is inserted into the guide bore 21 as described above. Its actuation, illustrated very schematically in FIGS. 5a and 5b, makes it possible to press the material of the cylindrical zone C in order to burst it. The bursting of the material generates generally radial cracks which, if not confined inside the cylindrical zone C, could propagate beyond the gap 22 and damage the drilling zone F. The process and the device according to the invention make it possible to avoid this damage by confining these cracks inside the cylindrical zone C.

To do this, and with reference to FIG. 1 e, prior to the bursting of the materials of the cylindrical zone C, it will be necessary to insert in the gap 22 a containment basket 13 as described above. Advantageously, the containment basket 13 has the same length as the diamond crown 12, and therefore the gap 22.

Its cylindrical shape allows it on the one hand to be inserted in the interstice 22, and on the other hand to cover a wide angular opening of the gap 22, and this over the entire length of the gap.

The spark gap 14 is then passed through the guide bore 21 through the opening 131 in the closed portion 130 at one end of the basket. Optionally, a support block CS may be placed under the drill string to support it and prevent it from bending under its own weight. The spark gap is then actuated to burst the materials of the cylindrical zone C, while confining these materials through the basket 13, as illustrated in FIG. 1f.

Thus, the basket 13 makes it possible to confine all of the radial shock waves generated by the bursting step of the materials of the cylindrical zone C.

In addition, the slot 133 that this containment basket 13 presents gives the latter a certain plasticity: under the stresses transmitted by the shock waves, the basket 13 can deform radially outwards (typically, the deformation can be a distance), which allows it to absorb the energy of the waves and to avoid its transmission outside the gap 22.

This also makes it easy to remove the basket 13 after the bursting of the materials. Indeed, if the containment basket 13 did not have this slot, the rocks or other materials exploded and remaining inside the basket would form a significant pressure on the inner walls of the basket and block the basket against the walls of the borehole, preventing thus his evacuation. It would also be difficult or impossible to extract the pieces of rock, as well as the spark gap 14 of the basket 13. The basket used in the invention solves these difficulties.

After the material of the cylindrical zone C has burst, the basket 13, containing these materials and the spark gap 14, is removed, for example by means of a withdrawal cable actuated by a winch T or any other known means.

Thanks to these steps, one obtains, as represented in FIG. 1g and illustrated in FIG. 6, a guide bore 21 of diameter D2, which preferably extends over a length equal to the total length L that it is desired to drill , as well as a first portion 201 of the final bore 20 of diameter D1, of length equal to the diamond crown 12. 4. Complete realization of the diameter of drilling D1 The rest of the process consists in reiterating the steps implementing the diamond ring 12 , the spark gap 14 and the containment basket 13, to advance the realization of the bore 20 of diameter D1.

If the guide bore 21 does not extend over the entire length of the bore 20 that it is desired to drill, it is also possible to repeat the step using the core drill 11.

To reiterate these steps, and with reference to FIG. 1g, each of the tools necessary for carrying out the various steps on the extended drill string 16 is successively fixed in order to obtain a length sufficient to reach the bottom of the first portion 201 of the drilling 20, and that we complete as the drilling progresses. For example, the diamond ring 12 is mounted on the drill string 16 to make the gap 22, then it is removed, and replaced by the containment basket 13, which is inserted into the gap. Finally this basket is separated from the drill string 16 and left in place, then the spark gap is fixed to the drill string 16 and inserted into the guide bore 21 before being actuated. After bursting, the spark gap 14 and the containment basket 16 are pulled out to extract the exploded material. Finally, an additional rod is added to the drill string 16 to repeat these steps further in the drilling zone F.

This drilling has a particularly regular surface, and free from defects such as cracks, which could degrade the properties of the wall, and particularly its impermeability.

Optionally, for a good completion of the drilling performed, it is possible to use a tool called "surfacer" 17, which allows to level the surface 202 located at the bottom of the final drilling 20. Indeed, at the moment when the materials of the last cylindrical zone C are exploded, they are not detached from the surface 202 in a regular manner. It is therefore possible to implement a complementary step of "surfacing" of the surface 202, that is to say flattening of this surface. The surfacer 17 that can be used for this step is illustrated schematically in FIG. 7a. This is a particular form of diamond ring, rotatably mounted as the latter on the drill string 16, and having on its front face 170 a projecting diamond portion for leveling the wall of the borehole. Preferably, the front face 170, illustrated in greater detail in FIG. 7b, is of circular section of diameter D1, and comprises several spiral sections 171 extending from the center of the front face towards its periphery, the sections being regularly distributed. to cover homogeneously the 360 ° of the surface of the front face 170. The sections are toothed to attack the drilling material (rocks, concrete, etc.). The spiral sections 171 may rest on a metal frame 172 such as a grid, which allows to lighten the structure. In addition, in the case where the compressed air is injected according to the same technique as explained above, the compressed air can pass through the grid and cool the leading edge of the surfacer 17. Ref. in Figure 1g is obtained, after evacuation of the exploded materials and surfacing, a bore 20 of diameter Dl between 600 and 700mm, whose bottom has a plane surface 202 and devoid of crack, and around which the drilling zone F is entirely preserved.

Claims (17)

REVENDICATIONS1. A method for producing a borehole (20) in a drilling zone (F), and a large diameter D1, comprising the steps of: a. performing a first guide bore (21), of diameter D2 less than D1, b. producing a cylindrical gap (22), of diameter D1, positioned in a controlled manner relative to the guide bore (21), delimiting a cylindrical zone (C) of the drilling zone (F) between the cavity (21) and the interstice (22) c. inserting a containment basket (13) into the cylindrical gap (22), d. burst the materials constituting the cylindrical zone (C) of the drilling zone (F), and e. extracting the previously exploded materials by evacuation of the containment basket (13). The method of claim 1, wherein the guide bore (21) is cylindrical, and concentric with the cylindrical gap (22). 3. Method according to claim 1, wherein the diameter D1 is greater than 400 mm, and preferably between 600 and 700 mm. 4. The method of claim 1, wherein the diameter D2 is between 60 and 100 mm, and preferably equal to 100 mm. The method of claim 1, wherein the first guide bore (21) is made by coring. 6. The method of claim 1, wherein the circular gap (22) is made by sawing. 7. Method according to one of claims 1 to 6, wherein the guide bore (21) made in step a. has a length equal to the desired length (L) of the borehole (20) of large diameter, and during which iterates the steps b. to e. until a borehole (20) of desired length (L) is obtained. The method of claim 7, further comprising a step in which the bottom of the bore (20) of desired length (L) is leveled. 9. Containment basket (13) adapted for use during steps c. to e. method according to claim 1, characterized in that it is able to deform plastically under the effect of shock waves generated by step d. bursting materials of the cylindrical zone (C). 10. Containment basket (13) according to the preceding claim, characterized in that it is able to deform radially outwardly. 11. Containment basket (13) according to the preceding claim, the basket (13) being of cylindrical shape, and having a slot (133) longitudinal along its entire length. 12. Drilling machine for carrying out a drilling (20) in a drilling zone (F), and a large diameter D1, comprising: - a means for producing a guide bore (21), of diameter D2 less than D1, - a means for producing a cylindrical interstice (22), of diameter D1, positioned in a controlled manner relative to the guide bore (21), delimiting a cylindrical zone (C) of the drilling zone (F) included between the cavity (21) and the gap (22), - a containment basket (13), adapted to be inserted into the cylindrical gap (22), - a spark gap (14), adapted to burst the materials of the cylindrical zone (C) of the drilling zone (F), and - a set of rods (16) of adjustable length, and adapted to be fixed at least to the containment basket (13) in order to extract the materials previously exploded by evacuation of the containment basket (13). 13. Drill according to claim 12, further comprising a surfacer (17) of diameter D1, adapted to flatten the bottom of a borehole obtained with said drill. 14. Drilling machine according to claim 12, wherein the means for producing the guide bore (21) is a core drill (11). 15. Drill according to claim 12, wherein the means for producing the gap (22) is a diamond crown (12). 16. Drilling machine according to the preceding claim, wherein the diamond crown further comprises a centralizer (15). 17. Drilling machine according to the preceding claim, wherein the centralizer (15) is cylindrical, concentric with the diamond ring (12), and adapted to be inserted into the guide bore (21).