FR2584448A1 - Method and installation for drilling and casing into ground - Google Patents

Abstract

Method for drilling and casing into ground 16 and installation implementing this method including : a drill string 2 comprising, at its lower end, a drill bit 4 and, near its upper end, a shoulder facing downwards; a pipe string 6 in which the drill string 2 is fitted, the upper end of the pipe string 6 being capable of receiving a thrust device 42 comprising a shoulder facing upwards and pierced with an orifice through which the drill string 2 passes; and a stop-piece placed between the said shoulders, which is capable of enabling a vertical force to be transmitted from the drill string 2 to the pipe string 6 and leaving the drill casing 2 to rotate freely with respect to the pipe string 6.

Description

Method and installation of drilling and casing in
a floor
The present invention relates to a method of drilling and casing in a soil and an installation implementing this method. The invention is particularly applicable to the starting of wells at sea or of f - sh or e
On sites whose surface land is poorly consolidated, the start of conventional "offshore" drilling is often very difficult.

 In fact, since the starting diameter is always large, the flow rates required for good removal of cuttings are often incompatible with the capacity of the suction pumps. In addition, high flows generally result in erosion of the walls, which results in poor recovery of the cuttings to which is sometimes added a collapse of the ground.

 These phenomena make drilling very difficult, require the production of a very large quantity of mud (drilling in lost sludge) and can even cause destabilization of the underbody of the feet of the platform, in the case of drilling carried out from of a self-elevating platform.

 Finally, at the end of the drilling, it is not rare that the casing cannot descend to the desired level.

 On large diameter boreholes conventionally drilled in reverse circulation air ("airlift"), the risk of collapse is even greater because in this case, the well is not filled with mud.

 In the two cases cited (conventional drilling and large diameter drilling), the most commonly used solution consists in driving a guide tube into the ground by threshing and then drilling inside this guide tube. This operation is long, dangerous and expensive.

 In addition, although these tubes are beaten "until the refusal", that is to say until the moment when they can no longer sink, the constancy over time of their bearing capacity is nevertheless not insured. Some tubes can slide into the well after drilling, which is very disadvantageous and expensive.

 The subject of the invention is therefore a method of drilling and casing in a soil and a drilling and casing installation making it possible to overcome the drawbacks mentioned above.

 The process of drilling and casing in a ground consists in simultaneously carrying out drilling and casing by placing a drilling string inside a line of tubes, so that it sinks as. the drill string digs the ground.

 The method according to the invention therefore consists in tubing the well while drilling, which eliminates the risk of collapse and saves several days of work on site.

The drilling and casing installation comprises - a drilling string having at its end
lower a drill bit and close to its ext re-
upper mite a downward-facing shoulder, - a line of tubes in which the
drill string, The upper end of the
line of tubes being provided with a cap comprising a shoulder oriented upwards and pierced with an orifice traversed by the drill string, - a stopper disposed between said shoulders, suitable
to allow the transmission of a vertical force of
the drill string to the tube line and
leaving the drill string free to rotate
compared to the tube line.

 Preferably, at least one support shoulder is formed on the drill string, inside the tube line, and retractable stops capable of folding inwardly of the tube line are fixed on that here, said support shoulder being capable of abutting on the retractable stops.

 Advantageously, base plates capable of being applied to the ground are fixed to the line of tubes at a level corresponding to the desired depth of casing.

 Preferably, the stop disposed between said shoulders is a ball stop comprising a lower ring and an upper ring, the lower ring being fixed to the shoulder of the cap and the upper ring being fixed to the shoulder of the drill string.

 Advantageously, the lower part of the drill string is provided with at least one roller bearing ensuring the guiding in rotation and translation of the drill string in the line of tubes.

Other advantages and characteristics of the invention will emerge more clearly from the description which follows, given by way of explanation but in no way limiting, with reference to the appended figures, in which
FIG. 1 represents, in longitudinal section and in a simplified manner, the drilling and casing installation according to the invention,
FIG. 2 represents, in section, the thrust device allowing the transmission of a vertical force from the drill string to the line of tubes,
FIG. 3 represents, in section and in a simplified manner, the device for supporting the line of tubes by the drill string,
FIG. 4 represents, in longitudinal section, the part of the line of tubes comprising the base plates and the retractable stops,
FIG. 5 represents, in transverse section, along the plane AA of FIG. 1, the line of tubes and more precisely a base plate seen from above,
FIG. 6 schematically represents the positioning of the line of tubes under the platform, and
- Figure 7 shows schematically the successive stages of drilling and casing according to the method of the invention.

 The drilling and casing installation according to the invention is shown in FIG. 1.

 The installation comprises a drill string 2 consisting of a series of tubes 3 fixedly aligned carrying at its lower end a drill bit 4. This drill string 2 is threaded in a line of tubes 6 intended for casing.

 The drill bit 4 is fixed to the last tube 3 by a rod 8 of larger diameter. This rod 8 has two bearings 10, 12, with rollers for example, allowing its guiding in rotation and in translation in the line of tubes 6. The bearing 12 is placed near the drill bit and the bearing 10 is sufficiently distant to support it. forces due to drilling. The outside diameter of the drill bit is substantially smaller than the inside diameter of the line of tubes 6, thus allowing it to pass through it.

 Base plates 14, capable of being applied to the ground 16 at the bottom of the sea 17, are fixed to the line of tubes 6 at a level corresponding to the desired casing depth.

 These base plates 14, for example four in number, are shown in more detail and enlarged in FIGS. 4 and 5. They each comprise a horizontal plate 18, in the form of a sector of a circular crown, reinforced by gussets 20, pa-r example four in number, vertical, substantially triangular in shape. Reinforcement ribs 22 connect the gussets 20. All these parts are welded together so as to constitute a single rigid part.

 The two gussets 20, arranged near the middle of the horizontal plate 18, are each placed against a vertical fixing rib 24, itself fixed on the line of tubes 6; two pins 26 fix each gusset 20 to the corresponding fixing rib 24 passing through holes 26a aligned in the two parts 20 and 24. Each of the base plates 14 is thus fixed firmly on the line of tubes 6.

 The fixing ribs 24 extend above the gussets 20 and are each pierced at their upper end by a hole 28. A shackle can take place in this hole 28 also called "ear" 28, and is then used to hang cables allowing the suspension of the line of tubes 6 from a platform 80 for example (Figure 1).

A device 30 for supporting the line of tubes 6 by the drill string 2 is shown in FIGS. 4 and 5 and more specifically on
Figure 3.

Two rectangular openings 32, 34 are formed in the line of tubes 6, above the base plates 14. These openings 32, 34 are diametrically opposed and located between two base plates 14. Two retractable stops 36, 38 are fixed sure
The line of tubes 6 opposite the openings 32, 34 respectively. These stops 36, 38 are hinged in such a way that they can occupy two extreme positions. In the first position occupied by the stop 36 in Figure 3, the stops are arranged vertically along the line of tubes. In the second position occupied by the stopper 38 in the same figure 3, the stops protrude horizontally at
The interior of the line of tubes 6. In this second position, a support shoulder 40, formed on the drill string 2 and more particularly on a tube 3, can then come to be applied under the underside of the stops. The stops are then locked in this second position and the drill string 2 can support the line of tubes 6 by
The intermediary of the support shoulder 40 and of the retractable stops 36, 38. In practice, it goes without saying that the two stops 36, 38 always occupy simultaneously the nêae position, contrary to what is shown by way of explanation on Figure 3.

 The drilling and casing installation also includes a pushing device 42 which is shown in FIG. 1 and in more detail and enlarged in FIG. 2.

 This device 42 is mounted on the lining 2 so as to bear against the upper end of the line of tubes 6, in order to transmit to it the thrust exerted by the drilling lining 2.

 The pushing device 42 comprises a cap 44 comprising vertical gussets 46 disposed radially with respect to a vertical axis substantially corresponding to the axis of the drill string 2. The gussets 46 are arranged in such a way that they provide a central orifice 48 crossed by the drill string 2. The gussets are linked together by cylindrical rings 50, 52 at the bottom and in the middle and by a circular angle 54 at the top. All these parts are welded together so as to constitute a single rigid part.

 The cap 44 has on its lower face a shoulder 56 capable of coming to bear against the upper end of the line of tubes 6 while being centered therein by a circular chamfer 58.

 The horizontal inner face 60 of the circular angle 54 is oriented upwards. The tube 3 of the drill string 2 disposed at the level of the cap 44 comprises at the level of this angle 54 a shoulder 62 oriented downwards and reinforced by ribs 64 vertical and radial. A ball bearing 66 provided with an upper ring 68 and a lower ring 72 is disposed between the face 60 of the cap 44 and the shoulder 62 of the drill string 2. The upper ring 68 of the stop 60 comes to be fixedly housed against the shoulder 62 and is linked in rotation with the lining 2 by drive pins 70. The lower ring 72 is fixedly housed in the angle 54 of the cap 44 against said face 60.

 A flange 74 fixed on an upper face of the cap 44 is disposed above the upper face of the shoulder 62 in order to prevent the separation of the two rings 68 and 72 from the stop 66 when the cap 44 is not resting on the line of tubes 6.

 The pushing device 42 is therefore capable of transmitting a vertical force, for example the weight of the drilling string 2, of this string 2 towards the line of tubes 6 via the cap 44 without this line of tubes 6 being rotated by the drill string 2.

 The drilling and casing procedure using the installation described above will now be explained with reference to Figures 6 and 7A, B, C, D, E and F.

 The procedure relates for example to the drilling and casing of an "off-shore" well in soil 16 from a platform referenced 80 in FIGS. 1 and 6.

FIG. 6 represents the first stages of the installation of the drilling string 2 in the line of tubes 6. The line of tubes 6 is assembled in particular by welding and then towed near the platform 80 by flotation or in the water. using floats arranged under the line of tubes 6. When the upper end of the line of tubes 6 is at
Plumb with a "rotation table" 82 of the platform 80, two cables fixed on this table 82 are hooked to the "ears" 28. The line of tubes 6 can then be raised and placed vertically by removing the floats or the flotation elements of this. These phases are shown in phantom in Figure 6.

 Another procedure could be envisaged which would consist of storing the tubes on the platform 80 and then mounting them end to end until the line of tubes 6 is formed.

 Once the line of tubes 6 is suspended vertically from the table 82, the base plates 14 are fixed to the fixing ribs 24 of the line of tubes 6 by the pins 26 (FIGS. 4 and 5).

 The drill string 2 is then lowered into the line of tubes 6 until the support shoulder 40 is below the support device 30 and more particularly of the openings 32, 34 (FIG. 3). The retractable stops 36, 38 are then tilted, for example manually, inside the line of tubes 6. The drill string 2 is then reassembled and the support shoulder 40 bears against the stops 36, 38. The cables attached to the ears 28 can then be removed since the drill string 2 supports the line of tubes 6. This position is shown in FIG. 7A. The pushing device 42 is then fixed to the drill string 2.

 The drill string assembly 2 and tube line 6 is then lowered until the tube line 6 sinks into the ground 16 under the effect of its own weight (FIG. 7B). At this instant, the lower end of the drill bit 4 is clearly above the surface of the ground 16. Indeed, it is necessary that the drill string 2 can descend without turning a sufficient distance to allow the retraction of the stops 36 , 38. When this automatic retraction is carried out and therefore that the support device 30 is no longer in operation, the drilling operation can begin (FIG. 7C).

 The various elements of the drill string 2 are placed in such a way that the pushing device 42 does not exert any force on the upper end of the line of tubes 6 during drilling as shown in FIG. 7C or a slight space between the cap 44 of the thrust system and the line of tubes 6 symbolizes this absence of relative effort.

It is estimated that the distance between the drill bit 4 and the lower end of the line of tubes 6 must be close to 2 meters when the pushing device 42 comes to bear on said line of tubes 6.

 During drilling, the line of tubes 6 follows the drill bit 4. If a stone 84 or a hard ground prevents the progression of the line of tubes 6, the pushing device 42 is applied against the line of tubes 6; the weight of the drill string 2 is added to the weight of the line of tubes 6, which makes it possible to force it to continue its downward progression (FIG. 7D).

 When the base plates 14 come to rest on the ground 16 (FIG. 7E), the drilling and casing operation is finished.

 We can then remove the drill string 2 as shown in Figure 7F and start subsequent operations such as cementing.

 This simultaneous drilling and casing procedure carried out using the above-described installation saves appreciable time compared to conventional procedures such as threshing. In addition, the risks of jamming and breakage are limited.

 Of course, the above description has been given by way of example only, any modifications in the embodiments being able to be envisaged without modifying the fundamental principle of the invention.

 For example, it is possible to envisage removing the support device 30 and simultaneously lowering the line of tubes 6 and the drill string 2 using cables.

Claims (6)

 1. Procedure for drilling and casing in a ground (16), characterized in that it consists in simultaneously carrying out drilling and casing by placing a drilling string (2) inside a line of tubes ( 6) so that it sinks in as the drill string (2) digs into the ground.  2. Drilling and casing installation characterized in that it comprises - a drilling string (2) comprising at its end  lower mite a drill bit (4) and close to its  upper end an oriented shoulder (62)  downwards, - a line of tubes (6) into which the  drill string (2), the upper end of  the line of tubes (6) being able to receive a ch  apeau (44) having an oriented shoulder (60)  upwards and pierced with a through hole (48)  by the drill string (2), r a stop (66) disposed between said shoulders  (60, 62) able to allow the transmission of an ef  strong vertical of the drill string (2) towards the  line of tubes (6) and leaving the rotation free  drill string (2) relative to the line of  tubes (6).  3. drilling and casing installation according to claim (2), characterized in that at least one support shoulder (40) is formed on the drilling string (2) included inside the line of tubes R6 ), and that retractable stops (36, 38) able to fold inwards towards the inside of the line of tubes (6) are fixed on this line of tubes (6), said support shoulder (40) being able to come abutting on the retractable stops (36, 38).  4. drilling and casing installation according to any one of claims 2 and 3, characterized in that base plates (14) adapted to be applied on the ground are fixed on the line of tubes (6) to a level corresponding to the desired casing depth.  5. drilling and casing installation according to any one of claims 2 to 4, characterized in that said stop (66) disposed between said shoulders (60, 62) is a ball stop (66) having a lower ring ( 72) and an upper ring (68), the lower ring (72) being fixed to the shoulder (60) of the cap (44) and the upper ring (68) being fixed to the shoulder (62) of the gasket drilling (2).  6. drilling and casing installation according to any one of claims 2 to 5, characterized in that the lower part of the drilling string (2) is provided with at least one roller bearing (10, 12) ensuring guiding in rotation and translation of the drill string (2) in the line of tubes (6).