EP1438478A1

EP1438478A1 - Guide device in an offshore drilling installation

Info

Publication number: EP1438478A1
Application number: EP02793173A
Authority: EP
Inventors: Stéphane ANRES
Original assignee: Saipem SA
Current assignee: Saipem SA
Priority date: 2001-10-24
Filing date: 2002-10-21
Publication date: 2004-07-21
Also published as: US20050002740A1; US7048470B2; FR2831204B1; FR2831204A1; WO2003040515A1

Abstract

The invention relates to a guide device (3) which is used in an offshore drilling installation in which at least one drilling riser (2) extends from a floating support (1) to the guide device (3) on the seabed. The inventive guide device (3) is characterised in that it comprises a sunken guide pipe (3) which comprises, successively: a front end which rests horizontally on the seabed; a curved, intermediary portion of guide pipe which is sunk into the seabed subsoil with a large radius of curvature, preferably a radius greater than 500 m; and, better still, an essentially-linear, inclined rear portion at the rear end of said guide pipe (3) which is sunk into the seabed subsoil along a given inclination (α) of between 5 and 60°. Said guide pipe (3) co-operates with controlled driving means (3 4).

Description

GUIDANCE DEVICE IN A SEA DRILLING INSTALLATION

The present invention relates to the known field of drilling at sea from a floating support anchored to the surface and more particularly to devices for guiding drill string trains installed at the bottom of the sea.

It relates more particularly to drilling deviated in deep water, so as to reach points distant from the vertical of the axis of the surface drilling machine.

As soon as the water depth becomes significant, the exploration and exploitation of production fields, particularly oil fields, is generally carried out using a floating support. This floating support generally comprises anchoring means to remain in position despite the effects of currents, winds and swell.

In the case of drilling operations, it also generally includes means for handling the drill string, as well as guidance equipment associated with safety systems installed at sea level. Drilling is usually carried out at the of the drilling rig, then penetrate the ground vertically over heights of several hundred meters. Then, said drilling is continued up to the oil slick called "reservoir", either vertically or with a gradual angular deviation, so as to reach more or less distant points of said reservoir.

By thus drilling several deviated wells, it is then possible to constitute a network of umbrella-shaped wells originating from the same position of the floating support on the surface, which makes it possible to group, throughout the exploitation of the field, all surface equipment in one place. Such installations are called DTU (Dry Tree Units), that is to say units with dry well heads, because in this case the well heads are collected on the surface, out of water. Operation is thus greatly facilitated, since it is possible to have access to one any of the wells from the DTU, to carry out all control and maintenance operations on the wells, and this throughout the lifetime of the installations, which reaches 20 to 25 years or even more.

Such drilling is only possible if the reservoirs are at great depth, for example 2000 to 2500 m, because it is imperative to have a vertical length of several hundred meters in the seabed, before initiating the deviation of the well whose radius of curvature of the pipes constituting the well are of the order of 500 to 1000 m.

We know the patents EP 0 952 300 and EP 0 952 301 which describe methods and devices making it possible to carry out deviated drilling by taking advantage of the slice of water to deviate as much as possible from the vertical of the drilling machine and to rest in the seabed substantially tangentially to the horizontal.

In these patents, the guiding devices installed at the bottom of the sea penetrate into the ground and make it possible to prime the wellbore in the seabed at an inclination of a given angle relative to the vertical. The guide device is connected to the drilling machine by a pipe called a "drilling riser" which guides the drill string which passes through them and ensures the lifting of mud and drilling debris.

This guide element installed at the bottom of the sea must make it possible to respect large radii of curvature of 500 to 1000 m and therefore must be large, while remaining very resistant to absorb the considerable forces generated by the rod train of drilling which will also be forced to follow the same radius of curvature, which induces very high friction and risks of destabilization of the assembly during drilling.

In addition, this guide element of considerable size and mass must be pre-installed in the ultra deep sea, that is to say in water depths of 1000 to 2500 m, or even more.

More specifically in EP 0 952 301, the guide device comprises a pipe element called "conductor" which is in fact the guide tube of the wellbore deployed from the floating support through the drilling riser to a structure called "skid" resting on the seabed. This skid structure holds and guides the conductive tube horizontally above the seabed at a certain height. Then this conductor adopts a curvature towards the bottom of the sea under the effect of its own gravity. The driver during his deployment cooperates with drilling tools so that he partially sinks into the sea floor. The installation of such a guidance device and in particular of the driver from the floating support represents an operational constraint important. In addition, this guide device does not allow any control of the curvature of the conductor. On the other hand, to respect a large radius of curvature, in particular greater than 500 m, it is necessary for the driver to deploy tangentially to the horizontal over several tens of meters beyond the fulcrum which guides it on the skid structure. Finally, no means is described in these patents to allow the implementation of said conductor over a large radius of curvature as is necessary so that the drill string, and especially the casing elements can operate with a minimum lateral friction inside the pipe. For a radius of 600 m, if the well head is 2 m above the ground, the conductor will only reach the ground 50 m further, which means a portion of conductor of 50 m, cantilevered , free and not maintained, which is unacceptable because the driver may break or bend due to too strong a curvature, because uncontrolled. In addition, the overhang thus created risks being detrimental to proper operation during drilling operations as well as during the entire service life which may exceed 25 years.

The problem according to the present invention is therefore to provide a guiding device which can be set up over a large radius of curvature in a reliable manner, that is to say by being able to control the curvature over a large radius of curvature, in particular greater than 500 m and whose realization and installation are easy to carry out. To do this, the present invention provides a guidance device useful in an offshore drilling installation, installation in which at least one drilling riser extends from a floating support to said guidance device at the bottom of the sea, said riser deviating drilling progressively from a substantially vertical position at the level of said floating support to a substantially horizontal or tangential position horizontally at the bottom of the sea, said drilling being able to be carried out from said floating support through said drilling riser and said guiding device so that the wellbore in the seabed is primed at a given inclination α relative to the horizontal preferably from 5 to 60 °, more preferably 25 to 45 °, said device guide being characterized in that it comprises a guide line in a depressed position in which said guide line successively comprises is lying : . a front end resting substantially horizontally on the bottom of the sea,

. a curved intermediate portion of guide pipe driven into the subsoil of the sea floor over a large radius of curvature, preferably a radius of curvature greater than 500 m and more preferably,

. a rear portion, substantially linear, inclined at the rear end of said guide pipe driven into the basement of the sea floor according to a said given inclination α, said guide pipe cooperating with controlled driving means allowing the driving said guide pipe into the seabed when said guide pipe is towed to the seabed at its front end, from an initial position where said guide pipe rests entirely over the seabed in a substantially horizontal position, to a so-called position sunk into the subsoil of the sea floor.

The curvature of the guide pipe is therefore formed by the controlled sinking of the guide pipe. The means of driving in the guide pipe make it possible to obtain, by driving in the pipe, a curvature of the pipe with a large radius of curvature at a desired and controlled value, the radius of curvature being in fact dependent on the characteristics and the arrangement of said driving means.

It is understood that said inclined linear portion is located in the tangential extension of said curved portion and, it is the inclination of this linear portion which determines said angle of initiation of the wellbore. It is also understood that by "horizontal at the bottom of the sea" is meant a substantially horizontal position as a function of the relief of the sea bottom.

In a particular embodiment, said guide pipe has a length of 100 to 600 m, preferably 250 to 450 m with a said given inclination α of the guide pipe of approximately 10 to 60 °, preferably 25 to 45 °. The desired curvature of the guide pipe then corresponds to an increase in inclination of about 1 ° per portion of the guide pipe length of 10 m, ie a radius of curvature of about 560 m. In a preferred embodiment, said front end of the guide pipe is embedded in a base comprising a load resting on a front sole so that said base keeps said front end of said guide pipe substantially horizontally on the seabed when it is towed. Said base prevents the front end of the guide pipe from being pushed in, as well as its rotation about a substantially horizontal axis perpendicular to the axis of traction.

The present invention also provides a method for producing a guiding device according to the invention, characterized in that steps are carried out in which:

- a so-called guide pipe is put into place in a said initial position resting substantially horizontally and rectilinearly on the seabed, said guide pipe cooperating with said controlled driving means, and

- A traction is carried out at the bottom of the sea of said front end of said guide pipe, preferably in the axial longitudinal direction of said guide pipe, from said initial position to a said depressed position.

The present invention also relates to an offshore drilling installation comprising a drilling riser extending from a floating support to a guide device according to the invention to which said drilling riser is connected, said drilling riser gradually deviating from a substantially vertical position at the level of said floating support to a substantially horizontal or tangential horizontal position at the bottom of the sea, the drilling being able to be carried out from said floating support through said drilling riser and said guide device for so that the wellbore begins in the seabed at a given inclination α relative to the vertical, preferably from 10 to 80 °.

The present invention also has for its object and a method for producing a drilling installation according to the invention, characterized in that steps are carried out in which: - a guiding device is produced according to a method according to the invention, and

- The connection of at least said drilling riser to said front end of the guide pipe resting on the seabed is made. The present invention finally relates to a drilling process using an installation of drilling according to the invention characterized in that drilling operations are carried out and a drilling well is constructed by deploying drill rigs cooperating with drilling tools and columns of tubes or casings, through a so-called drilling riser and a said guidance device driven into the bottom of the sea.

It will be understood more precisely that the drill string initially makes it possible to deploy the drilling tools, then to deploy the elements of tubes, called "columns of tubes or casings" which constitute the borehole as the drilling proceeds and their placement in the seabed.

Other characteristics and advantages of the present invention will appear in the light of the description of several preferred embodiments which will follow, with reference to the following figures in which:

• Figure 1 is a side view of a DTU-type surface support equipped with a drilling riser connected to a guidance device pre-installed on the sea floor. • Figures 2 and 3 are side views a guide device associated with an anchor ensuring penetration into the ground, represented respectively before and after penetration into the seabed,

• Figures 4 and 5 are sectional side views along the respective sectional planes AA and BB of the guide device, • Figures 6 and 7 are side views of a guide device equipped with lateral fins ensuring variable penetration into the ground, represented respectively before and after penetration into the seabed,

FIG. 8 is a view from the left of the guide device according to FIG. 6 detailing the lateral fins,

FIG. 9 is a side view of a guide device equipped with secondary launching pipes facilitating the de-cohesion of the ground during the phase of penetration into the seabed,

FIG. 10 is the sectional view of the current section relating to FIG. 9,

• Figures 11 and 12 are side views of a structure associated with the guide device according to Figures 2 and 3, limiting the penetration during penetration into the ground, shown respectively before and after said penetration into the seabed , • Figures 13 and 14 are the sections according to the planes CC and DD relating to Figure 11. • Figures 15 and 16 are diagrams representing the values of the angles OCj and the spacings of the deflectors to obtain the desired curvature relating to Figures 7 and 12 respectively.

Figure 1 is a side view of a DTU type surface support 1 equipped with a drilling rig and processing equipment. A drilling riser 2 in chain configuration, is connected to a guide pipe 3 by means of an automatic submarine connector 2. The structure 3 _{4 shows} diagrammatically the means of controlled insertion. A subsea well control assembly 2 ₂ is associated with this well entrance and makes it possible to close the well in the event of an eruption. The drilling is carried out in a conventional manner from the surface through the drilling riser 2 and through the guide device 3-3 ₄ , until reaching the reservoir.

Said drilling riser 2 gradually deviates from a substantially vertical position 2a at the level of said floating support 1 to a substantially horizontal or tangential horizontal position 2b at the bottom of the sea, drilling can be carried out from said floating support 1 to through said drilling riser 2 and said guiding device 3 so that the drilling well starts in the sea bottom at a given inclination α relative to the horizontal, preferably from 10 to 80 °. The controlled driving means 3 ₄ , 5 ₁ -5 ₃ , 7 - ^, 8-9, 13 allow the driving of said guide pipe 3 into the seabed when said guide pipe 3 is towed T to bottom of the sea at its front end 3 _1;

- from an initial position A1 where said guide pipe 3 rests entirely over the sea bottom in a substantially horizontal position,

- Up to a depressed position A2 in the basement of the sea floor, depressed position in which said guide pipe 3 successively comprises:. a front end 3 resting substantially horizontally on the bottom of the sea,

. a curved intermediate portion of guide pipe driven into the subsoil of the sea floor in a large radius of curvature, preferably a radius of curvature greater than 500 m and,

. a substantially linear rear portion inclined 3 ₃ at the rear end of said guide pipe 3 pressed into the basement of the sea floor at a given inclination given oc. Example 1

In a first preferred embodiment of the invention, said controlled driving means comprise: - a 5 _t front sole placed on the seabed and supporting said 3 _t front end of the guide pipe and integral with it,

at least one intermediate sole 5 ₂ , 5 ₃ supporting said curved intermediate portion 3 ₂ and / or of the rear portion 3 ₃ of said guide pipe and integral with it, the surface of which is smaller than that of said sole before 5 _1; preferably several said intermediate flanges 5 ₂ , 5 ₃ distributed along said intermediate portion 3 ₂ and rear portion 3 ₃ of said guide pipe 3, the surface of which is smaller and smaller with respect to said front flange as and when that they are closer to said rear end 3 ₃ of the guide pipe, and

- An anchor 13 connected 12 to said rear end 3 ₃ and able to sink into the ground under the effect of said traction from said front end 3.

FIG. 2 illustrates this first version of the guide device according to the invention, in which the guide device is towed to the site by means of a cable 10 connected to the front of the guide device via 'A traction head 11, the rear of said guide device being connected by a second cable 12 to a very high performance anchor 13 of the Stevpriss® or Stevmanta® type from the company NRYHOFF (Holland). The front part 3 _X of the guide device is integral with a sole 5 _j of large surface area and resting on the seabed so as to limit penetration into the ground. In the same way, soles 5 ₂ , 5 ₃ of smaller dimensions are distributed along the guide pipe, their bearing surface decreasing as one approaches the rear 3 ₃ of said guide pipe. The front 3 is further stabilized by a base comprising a load 6 secured to the sole 5 _t thus creating an embedding of the guide device in said base 6, as illustrated in FIG. 3.

By exerting traction on the towing cable 10, the assembly drives the anchor which then begins to sink 25, thereby causing 24 the rear end 3 ₃ of the guide pipe. The circular shape of the guide pipe only moderately brakes penetration, while the soles 5 ₂ , 5 ₃ distributed over the length oppose penetration with a force proportional to their surface. The front sole 5 _γ being large, the front of the guide device remains on the surface and the mooring 6 stabilizes the assembly in such a way that the axis of the guide device remains substantially horizontal, therefore parallel at the bottom of the sea 4.

A method of producing a guide device of this type consists in pulling the front end 3 _λ of said guide pipe 3 until said intermediate flanges 5 ₂ , 5 ₃ are found sunk into the ground increasingly deeper as they are closer to the rear end 3 ₃ of the guide pipe to obtain the desired curvature R, preferably a radius of curvature greater than 500 m more preferably between 500 and 1000 m. Example 2

In another preferred embodiment of the invention, illustrated in FIGS. 6, 7 and 8, said controlled insertion means comprise at least one deflector 7 _{l 5} 7 ₂ , 7 ₃ secured to said guide pipe 3 in said intermediate portion 3 ₂ or said rear portion 3 ₃ of the guide pipe comprising flat surfaces, preferably symmetrical with respect to the vertical axial plane XX ', YY' of said guide pipe in the longitudinal direction when the latter is in position horizontal rectilinear, and said planar surfaces of the deflectors being inclined with respect to a horizontal axial plane XX ', ZZ' of said guide pipe when the latter is in horizontal position on the bottom from the sea, said deflector 7 _{l 5} 7 ₂ , 7 ₃ being inclined at an angle oq, oc ₂ , ₃ so as to create a depression in said guide pipe when the latter is towed from said initial position Al substantially horizontal up to a said depressed position A2 in the sea floor. These deflectors 7, 7 ₂ , 7 ₃ make it possible to control the curvature of the guide pipe driven into the sea floor because, once said deflectors are in horizontal position, as shown in FIG. 7, they prevent the further driving of the pipe and stabilize it in the desired position A2. It is understood that it is the spacing and the inclination i of the deflectors which determine the curvature and more generally the shape of the guide pipe in the depressed position A2.

Preferably, the guide device comprises a plurality of deflectors 7i (7 _d -7 ₃ ) distributed along said guide pipe inclined at angles ai (a ₁ -a ₃ ) reducing as said deflector 7i (7 ^ 7 ₃ ) is closer to said front end _X.

The guide pipe is therefore equipped with several deflectors 7j-7 ₃ integral with the guide pipe and oriented oq-oq relative to the axis XX 'of the latter. The deflector 7 _! -7 ₃ is for example a simple flat sheet, preferably reinforced, preferably symmetrical along the vertical axial planes XX ', YY' and horizontal XX ', ZZ' of the guide pipe, welded to the guide pipe guide device as illustrated in FIG. 8. This angle is adjusted beforehand during the manufacture of the guide device, so as to act as the anchor 13 described in FIGS. 2-3, that is to say to create a depression in the pipe. guide, this depression being limited due to the angle oc. In fact, during the traction T exerted on the towing cable 10, the deflectors 7 ₁ -7 ₃ sink, locally causing the guide pipe 24, until the deflector is substantially parallel to the force of traction on the cable 10, that is to say substantially parallel to the bottom of the sea 4, or even substantially horizontal, a position in which it will then no longer exert a vertical downward force, tending to cause the assembly to descend. A multitude of deflectors 7 ₁ -7 ₃ , which may or may not be identical, will advantageously be disposed along the guide device, each of them having an angle o ^ - oc ₃ which decreases as we get closer to the front end 3 _{l 5} as illustrated in FIG. 6. When penetrating 24 into the ground, we then obtain, as soon as all the deflectors 7 _! -7 ₃ have reached a substantially horizontal position, the desired curvature, as illustrated in FIG. 7.

A method of producing a guide device according to this second embodiment consists in pulling T from the front end 3 _t of said guide pipe 3 until said deflectors 7 _{l 5} 7 ₂ , 7 ₃ find themselves sunk into the ground in a horizontal position to obtain a said desired curvature preferably with a radius of curvature greater than 500 m more preferably between 500 and 1000 m. In Figure 15, there is shown the outline of a guide pipe 3 of length 400m initially resting horizontally on the bottom, then in the depressed position with successively a front portion 3 _t in straight configuration, a central portion 3 ₂ in configuration curve and a substantially straight rear part 3 ₃ , fitted with driving means 7i (7 _r 7 ₇ ) as described in connection with FIG. 7. Said deflectors 7i are spaced along said pipe and inclined at an angle ai with respect to the latter according to the values shown in Table 1 below, so as to obtain a radius of curvature R = 550 m. Table 1

Example 3

FIGS. 9 and 10 illustrate another preferred version of the invention in which said controlled insertion means comprise:

secondary pipes 8 for launching fluid 18 integral with said guide pipe 3, extending parallel to the latter and beneath it, and - Said secondary pipes 8 having a reduced diameter compared to that of the guide pipe 3 and comprising perforations 9 on the underside making it possible to expel a fluid 18 towards the bottom of the sea when said secondary pipes 8 are supplied by said fluid 18 under pressure.

Preferably, said secondary pipes 8 are connected by their ends 8 _{l 3} 8 ₂ to the front and rear ends 3 _{l 5} 3 ₃ of said guide pipe and communicate with said front ends 3 _X and rear 3 ₃ so that it is possible to feed them through the same supply line 19 from said front end 3 _t of said guide line 3.

In FIG. 10, two secondary pipes 8 are represented, arranged symmetrically with respect to the guide pipe 3.

In FIG. 9, the secondary pipe 8 is connected at their two ends to the guide pipe 3 by non-return valves.

8 _{l 3} 8 ₂ . Said guide pipe 3 is itself hermetically closed at its two ends, on the one hand by the traction head 11 and on the other hand by a plug 14. An orifice is connected by a water supply pipe

35, to the surface ship 1 having the necessary pumping means. Thus, during towing, the guide pipe can be lightened by filling pressurized gas through the pipe, the excess pressure escaping through the non-return valves 8 _{l 5} 8 ₂ , then through the orifices 9 of the secondary pipes 8. As soon as the assembly is deposited on the bottom 4, water is injected via the same pipes 8, advantageously under high pressure, which will have the effect of weighing down the assembly by filling the pipe guide 3, then perform a de-cohesion of the ground on the underside, which facilitates the driving in of the guide pipe.

A method for producing a guidance device of this type comprises steps in which:

a gas under pressure is injected into said secondary pipes 8 when it is desired to tow the guide pipe 3 over the sea bottom and a liquid under pressure is preferably injected, preferably water, into said secondary pipes 8 and preferably into said guide pipe 3 closed at these ends 3 _{l 5} 3 ₂ and communicating with said ends 8 _{l 5} 8 _{2 of} said secondary pipes 8 when it is desired to push said guide pipe 3.

Example 4

In another preferred version of the invention illustrated in FIGS. 11 to 14, there is advantageously added to any of the devices according to FIGS. 2 to 10, a rigid external upper structure 20, embedded on the front 3 _j of the guide line 3, the assembly resting on the ground by means of lateral flanges 21, as illustrated in FIG. 14, detailing the section according to the plane DD.

More specifically, the guide device comprises:

a rigid external upper structure 20 covering and now rectilinear said guide pipe 3 when the latter is substantially horizontal and rests on the bottom of the sea,

said external structure 20 having a longitudinal central opening on the underside allowing said guide pipe 3 to sink into the ground when the latter is towed T, and

- At least one link 17 _{l 5} 17 ₂ , 17 ₃ connecting at least the rear part 3 ₃ of said guide pipe to said external structure 20 so as to prevent it from sinking beyond a given depth so limiting the curvature R of said curved portion, and

- Said external upper structure 20 resting on the ground at the bottom of the sea 4 preferably by means of lateral soles 21 located on either side of said longitudinal central opening 22, said lateral soles 21 preventing the sinking of said rigid external structure 20, and

- Said external structure 20 being integral with said base 6 in which said front portion 3 of the guide pipe 3 is embedded. The current portion of the guide pipe is free to move vertically through the central opening 22 of the structure 20, as illustrated in FIG. 13 detailing the section along the plane CC, of the structural elements 23 limiting the lateral displacements. Preferably, the guide device comprises:

- A plurality of flexible links 17 _{l 5} 17 ₂ , 17 ₃ distributed along the guide pipe 3 and having an increasing length as they are closer to the rear end 3 ₃ of the pipe guide 3 and whose length is such that said guide pipe has a said curved portion with the desired curvature R and a said rear rear portion 3 ₃ linear.

These flexible links 17 _{l 5} 17 ₂ , 17 ₃ are for example cables or chains connected on the one hand to the external structure 20 at 26 and to the guide pipe at 27. Said attachment points 26-27 are shown in FIG. 12. These flexible connections 17 ₁ -17 ₃ are distributed along the guide pipe, uniformly or not, and have a variable length, decreasing when one approaches the front 3 _X of the guide line. Their position and their length are determined, so that at the end of penetration into the ground, when they are all in tension, the desired curve is obtained as illustrated in Figure 12. To avoid sinking into the ground of the structure 20, a multitude of lateral soles 21 is installed on the underside, so as to create sufficient seating.

A method of producing a guide device of this type essentially consists in pulling T from the front end 3 _X of said guide pipe 3 of said rigid external structure 20 integral with said guide pipe until the one or more links 17 ₁ -17 ₃ prevent further depression of at least said rear portion 3 ₃ of said guide pipe to obtain the desired curvature R preferably a radius of curvature greater than 500 m, more preferably between 500 and 1000 m.

In FIG. 16, there is shown a sketch of a guide pipe 3 of length 400 m equipped with driving means in accordance with those of FIG. 12, the insertion of the guide pipe being limited by a plurality of flexible links 17i (17 ₁ -17 ₇ ) connecting said pipe at a _; to a frame of the structure 20 (not shown). Table 2 below gives by way of illustration the values of the length li and of the spacing of said flexible links 17i, corresponding to a curvature of the pipe with a radius of curvature = 550 m.

Table 2

All of these controlled insertion means 5 ₁ -5 ₃ , 7 ₁ -7 ₃ , 13, 20, 17 _α -17 ₃ according to the invention described in examples 1 to 4 above can be used, either individually , or in combination, the nature of the soil requiring, in the case of strong cohesion, extremely powerful means. By way of illustration, the guide pipe 3 has a diameter of 0.40 to 0.76 m (16 to 30 ") and measures approximately 200-400 m for a mass of 30 to 80 tonnes. The external structure 20 is preferably continuous along the guide pipe and represents an additional mass of 25 to 75 tonnes The launching is carried out with pressurized water from the surface at pressures of 20 to 100 bars in secondary pipes 8.

Claims

1. Guide device (3) useful in an offshore drilling installation, installation in which at least one drilling riser (2) extends from a floating support (1) to said guide device (3) at the bottom from the sea (4), said drilling riser (2) gradually deviating from a substantially vertical position (2a) at the level of said floating support (1) to a substantially horizontal or tangential horizontal position (2b) at the bottom from the sea (4), said drilling being able to be carried out from said floating support through said drilling riser (2) and said guiding device (3) so that the drilling well in the seabed is started according to a given inclination (α) relative to the horizontal preferably from 5 to 60 °, more preferably from 25 to 45 °, said guide device (3) being characterized in that it comprises a guide pipe ( 3) in a depressed position (A2) in which said guide pipe e (3) successively includes:

. a front end (3J resting substantially horizontally on the bottom of the sea,

. a rear portion, substantially linear, inclined at the rear end (3 ₃ ) of said guide pipe (3) pressed into the basement of the sea floor according to a said given inclination (α), said guide pipe ( 3) cooperating with controlled driving means (3 ₄ , 5 ₁ -5 ₃ , 7 ^ ₃ , 8-9, 13) allowing the driving of said guide pipe (3) in the sea bottom when said guide line (3) is towed (T) to the sea bottom at its front end (3 _X ), from an initial position (Al) where said guide line (3) rests entirely over the sea bottom in a substantially horizontal position, to a so-called sunken position (A2) in the basement of the sea floor.

2. Guide device according to claim 1, characterized in that said guide pipe (3) has a length of 100 to 600 m, preferably 250 to 450 m with said given inclination (α) of the guide pipe. about 10 to 60 °, preferably 25 to 45 °.

3. Guide device according to claim 1 or 2, characterized in that said front end (3J is embedded in a base (6) comprising a load resting on a front sole (5 _X ) so that said base (6) maintains said front end (3J of said guide pipe substantially horizontally on the bottom of the sea when the latter is towed (T).

4. Guide device according to one of claims 1 to 3, characterized in that said controlled driving means comprise:

- a front sole (5J placed on the sea bottom and supporting said front end (3J of the guide pipe and integral with it,

- at least one intermediate sole (5 ₂ , 5 ₃ ) supporting said curved intermediate portion (3 ₂ ) and / or of the rear portion (3 ₃ ) of said guide pipe and integral with it, the surface of which is more smaller than that of said front sole (5J, preferably several said intermediate soles (5 ₂ , 5 ₃ ) distributed along said intermediate portion (3 ₂ ) and rear portion (3 ₃ ) of said guide pipe (3) the surface is smaller and smaller with respect to said front sole as they are closer to said rear end (3 ₃ ) of the guide pipe, and

- An anchor (13) connected (12) to said rear end (3 ₃ ) and capable of sinking into the ground under the effect of said traction from said front end (3 _j ).

5. Guide device according to one of claims 1 to 4, characterized in that said controlled driving means comprise at least one deflector (7 _{l 5j} 7 ₂ , 7 ₃ ) integral with said guide pipe (3) in said intermediate portion (3 ₂ ) or said rear portion (3 ₃ ) of the guide pipe comprising preferably flat surfaces symmetrical with respect to the vertical axial plane (XX ', YY') of said guide pipe in the longitudinal direction when the latter is in horizontal rectilinear position, and said planar surfaces of the deflectors being inclined with respect to a horizontal axial plane (XX ¹ , ZZ ') of said guide pipe when the latter is in a horizontal position on the sea floor, said deflector (7 _X , 7 ₂ , 7 ₃ ) being inclined at an angle (α _{l 3} oc ₂ , oc ₃ ) so as to create a depression of said guide pipe when the latter is towed from said initial position (Al) substantially horizontal to a said pressed position (A2) in the bottom of the sea.

6. Guide device according to claim 5, characterized in that it comprises a plurality of deflectors (7 _t , 7 ₂ , 7 ₃ ) distributed along said guide pipe inclined at angles (oq, ₂ , ₃ ) is reducing progressively as said deflector (7 _{l 3j} 7 _{_2;} 7 ₃₎ is closer to said front end (3 _X).

7. Guide device according to one of claims 1 to 6, characterized in that said controlled driving means comprise:

- secondary pipes (8) for launching fluid (18) integral with said guide pipe (3), extending parallel to it and on the underside thereof, and - said secondary pipes (8) having a reduced diameter compared to that of the guide pipe (3) and comprising perforations (9) on the underside for expelling a fluid

(18) towards the bottom of the sea when said secondary pipes (8) are supplied with a said fluid (18) under pressure.

8. Guide device according to claim 7, characterized in that said secondary pipes (8) are connected by their ends (8 _{l 5} 8 ₂ ) to the front and rear ends (3 _1; 3 ₃ ) of said guide pipe and communicate with said front (3 _t ) and rear (3 ₃ ) ends so that it is possible to supply them by the same supply line (19) from said front end (3 _X ) of said guide line (3 ).

9. Device according to one of claims 1 to 8, characterized in that the guide device comprises: - a rigid external upper structure (20) covering and now rectϋigning said guide pipe (3) when the latter is substantially horizontal and rests on the bottom of the sea,

said external structure (20) having a longitudinal central opening on the underside allowing said guide pipe (3) to sink into the ground when the latter is towed (T), and

- At least one link (17 _{l 5} 17 ,, 17 ₃ ) connecting at least the rear part (3 ₃ ) of said guide pipe to said external structure (20) so as to prevent it from sinking beyond d '' a given depth so as to limit the curvature (R) of said curved portion, and

- Said external upper structure (20) resting on the ground at the bottom of the sea (4) preferably by means of lateral flanges (21) located on either side of said longitudinal central opening (22), said flanges lateral (21) preventing the sinking of said rigid external structure (20), and

- Said external structure (20) being integral with said base (6) in which said front portion (3f) of the guide pipe

(3) is recessed.

10. Guide device according to claim 9, characterized in that it comprises a plurality of flexible links (17 _1; 17 ₂ , 17 ₃ ) distributed along the guide pipe (3) and having an increasing length as and as they are closer to the rear end (3 ₃ ) of the guide pipe (3) and whose length is such that said guide pipe has a said curved portion with the desired curvature (R) and said linear rear portion (3 ₃ ).

1 1. A method of producing a guide device according to claims 1 to 10, characterized in that steps are carried out in which:

a so-called guide pipe is put into place in a said initial position (Al) resting substantially horizontally and rectilinearly on the sea bottom, said guide pipe (3) cooperating with said controlled driving means (3 ₄ , 5 ^ 5 ^ 7 ^ ₃ , 8-9, 13), and

- traction is carried out (T) at the bottom of the sea from said front end (3 _t ) of said guide pipe (3), preferably in the axial longitudinal direction XX ′ of said guide pipe, from said initial position ( Al) to a said depressed position (A2).

12. A method of producing a guide device according to claim 11, characterized in that guide devices are used according to claim 3 or 4 and a traction (T) is carried out of the front end ( _X ) of said guide pipe (3) until said midsoles (5 ₂ , 5 ₃ ) are driven deeper and deeper into the ground as they are closer to the rear end ( 3 ₃ ) guide pipe to obtain the desired curvature (R), preferably a radius of curvature greater than 500 m, more preferably between 500 and 1000 m.

13. A method of producing a guide device according to claim 11 or 12, characterized in that a guide device according to claim 5 or 6 is used and traction is carried out (T) from the front end (3J of said guide pipe (3) until said deflectors (7 _{l 5j} 7 ₂ , _j 7 ₃ ) are driven into the ground in a horizontal position to obtain said desired curvature preferably at a greater radius of curvature 500 m preferably between 500 and 1000 m.

14. A method of producing a guide device according to one of claims l i to 13, characterized in that a guide device according to one of claims 7 or 8 is used and

- A gas under pressure is injected into said secondary pipes (8) when it is desired to tow the guide pipe (3) over the sea floor and

- A liquid under pressure is preferably injected, preferably water, into said secondary pipes (8) and preferably into said guide pipe (3) closed at these ends (3 _{l 5} 3 ₂ ) and communicating with said ends (8 _{l 3} 8 ₂ ) of said secondary pipes (8) when said guide pipe (3) is to be pushed in.

15. A method of producing a guide device according to one of claims l i to 14, characterized in that a guide device according to one of claims 9 or 10 is used and traction is carried out

(T) of the front end (3J of said guide pipe (3) of said rigid external structure (20) integral with said guide pipe until the link (s) (17 _d -l 7 ₃ ) prevent an additional depression of at least said rear portion (3 ₃ ) of said guide pipe to obtain the desired curvature (R) preferably a radius of curvature greater than 500 m, more preferably between 500 and 1000 m.

16. offshore drilling installation comprising a drilling riser (2) extending from a floating support (1) to a guide device to which said drilling riser is connected according to one of claims 1 to 10, said drilling riser (2) gradually deviating from a substantially vertical position (2a) at said floating support (1) to a substantially horizontal or tangential to horizontal position (2b) at the bottom of the sea, the drilling being able to be made from said floating support (1) through said drilling riser (2) and said guide device (3) so that the drilling well starts in the seabed at a given inclination (α) relative to the horizontal, preferably 10 to 80 °.

17. A method of producing a drilling installation according to claim 16, characterized in that steps are carried out in which:

a guiding device is produced according to a method according to one of claims 1 to 15, and

- The connection of at least said drilling riser (2) is made to said front end (3 _d ) of the guide pipe resting on the seabed (4).

18. A drilling method using a drilling installation according to claim 16, characterized in that drilling operations are carried out and a borehole is constructed by deploying drill pipes cooperating with drilling tools and columns of tubes or casings, through a said drilling riser (2) and a said guide device (3) driven into the bottom from the sea (4).