WO2004001180A1

WO2004001180A1 - Telescopic guide pipe for offshore drilling

Info

Publication number: WO2004001180A1
Application number: PCT/FR2003/001867
Authority: WO
Inventors: Stéphane ANRES; Hans P. Hopper
Original assignee: Saipem S.A.
Priority date: 2002-06-19
Filing date: 2003-06-18
Publication date: 2003-12-31
Also published as: EP1525371A1; NO20045161L; US20050152749A1; BR0311923A; FR2841293B1; AU2003260605A1; FR2841293A1; ATE389777T1; DE60319833D1; EP1525371B1

Abstract

The invention relates to a guide device (3) for an offshore drilling installation comprising at least one drilling riser (2) which extends from a floating support to the aforementioned guide device (3) at the bottom of the sea (4), whereby the drilling can be performed from said floating support via the drilling riser (2) by means of a drill string which is equipped with drilling tools at the end thereof. According to the invention, the telescopic guide device (3) comprises a telescopic guide pipe (3) consisting of coaxial (xx') telescopic pipe elements (3a, 3b, 3c), the end of the inner telescopic pipe element (3c) having the smallest diameter being equipped with a means of breaking up the sea floor in order to drive said telescopic guide pipe (3) progressively into the ground so that a drilling tool can be guided deeper therein.

Description

TELESCOPIC GUIDANCE PIPE FOR SEA DRILLING

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 comprises means for handling the drill string, as well as guiding equipment associated with safety systems installed at sea level.

Drilling is usually carried out vertically from the drilling rig, then penetrates 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. The well start-up phase is generally carried out by descending from the surface a drilling base resting on the seabed provided with guide lines to the surface, then descending a length of pipe, called "casing" or casing, of strong diameter, in general 0.914 m (36 ") and measuring 50 to 60 m long in total. Said casing is carried out from unit lengths of pipe measuring approximately 12 m long assembled by screwing on board the drilling platform, at derrick floor level. To withstand the stresses, each unit length of casing has a zone at each end reinforced over a length of 0.5m to 1m, consisting of an additional thickness corresponding to approximately 0.5 to 2 times the current thickness of the wall of said casing, thickness in which said thread is machined. Said casing, once assembled, passing through said base, is then simply planted in the ground, generally poorly consolidated and the insertion is often carried out by launching (that is to say by sending water under pressure). This first casing serves to consolidate the walls of the well in the area close to the bottom of the sea, and therefore acts as a guiding device for a second casing, of smaller diameter and, in general, of a total length of 150 to 200m, said second casing also being produced by a pipe assembly of 12m in unit length comprising reinforced zones at the ends, has an outside diameter, including the reinforced thread zones, much smaller than the internal diameter of the external casing, so that it can slide there freely during installation and so that the cementing grout can travel in the best conditions. Said second casing is then either vibro-drilled or drilled if the terrain requires it, then the gap between the said casings and the ground is cemented from the surface, as well as between the two said casings. During these phases, one works with an open hole (“open hole”) and one risks being exposed to ground instabilities, or to untimely inflows of water occurring at shallow depth below the sea bottom ( "Shallo ater flo"), seriously disrupting the start-up phase of the well.

Depending on the nature of the soil, it may be necessary to consider a third casing, or even a fourth, so as to reach a sufficient depth to initiate the actual drilling.

Thus, the multiple casings present significant spaces between each said casing and the following and, moreover, because each of said casings extends from the sea level to its lowest end, this implies that at sea level and over the entire height of the first casing and those following, there are radially two, three, even four or more, successive casing thicknesses, which will in fact be useless in the pursuit of operations, because in the main phase of drilling and operating the well, only one casing thickness is required to support the downhole equipment as well as the watertightness of the assembly. These multiple casings, redundant in the area close to the seabed, are made necessary because of the manner of proceeding for the starting of a well drilling according to the prior art, redundancy which represents a considerable quantity of steel, and therefore a very significant cost.

GB-2,338,009 is known, which describes an installation method for multiple independent casing elements installed successively one inside the other with a reduced clearance. Said casings being installed in sequence, one after the other, this makes it possible, because of said reduced clearance, to minimize the maximum diameter of the hole to be drilled, both for the external casing and the intermediate casings, which therefore reduces the quantity of rubble to be evacuated as well as the power requirements of the drilling rig and thereby are cost per hour. The patent US Pat. No. 5,307,886 is known, which describes a system and or mode of installation enabling multiple casings to be produced with reduced clearance, and minimizing the space between said casing and the wall of the hole drilled in the ground.

A first problem underlying the invention is to provide a guiding device making it possible to guide the drill string and the drilling tool as deeply as possible in the subsoil at the bottom of the sea, so as to avoid these incidents of untimely water arrival occurring at shallow depth during the installation of the casings.

Another problem is to reduce the handling and assembly phases on board the drilling platform, of the individual pipes used to produce the said casings in order to reduce the difficulty, the duration and therefore the cost of installing the casings, particularly in the case of an installation in Ultra Grands Fonds, ie for depths of 2000 to 3000 meters or more. Indeed, these manipulations being carried out in successive and independent sequences, if the actual time of installation, that is to say the sinking into the ground, of the first casing, of the second casing or of the following remains acceptable, the manipulations intermediaries consisting in bringing gripping tools to the surface, then lowering again the following casing, then represent a time considerable, therefore an extremely high cost of immobilizing the drilling rig, when the water height reaches 2000, 3000 or even 4000 to 5000m or more. In addition, the phases of cementing the gap between two risers require a very long time which increases the cost of the operation.

Another problem is to radically reduce the quantity of steel necessary for the production of these casings by minimizing the redundancies as well as the clearances between said successive casings.

On the other hand, in the case of drilling several deviated wells, it is possible to constitute a network of wells in the form of an umbrella originating from the same position of the floating support on the surface, which makes it possible to group, during all of 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 any of the wells from the DTU, to carry out all the control and maintenance operations on the wells, and this throughout the lifetime of the installations which reach 20 to 25 years and even more. Such deviated 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 wells whose radius of curvature of the pipes constituting the well are of the order of 500 to 1000 m. We know the patents EP 0952300 and EP 0952301 which describe methods and devices making it possible to carry out deviated drilling while 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 "drilling riser" which guides the drill string passing through them and ensures the recovery 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 conductor 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 along a large radius of curvature as is necessary for the drill string, and above all the casing elements can operate with a minimum of 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 a too strong local 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.

Another problem according to the present invention is therefore to provide a guiding device in a drilling application deviated in the height of the water slice, which can be set up along a large radius of curvature in a reliable manner, that is that is to say, being able to control the curvature over a large radius of curvature, in particular greater than 500 m and the implementation and positioning of which are easy to perform.

According to a first aspect providing a solution to the problem of guiding the drill string and the drilling tool as deeply as possible, the present invention provides a device for guiding an offshore drilling installation comprising at least one drilling riser extending from a floating support to said guide device at the bottom of the sea, said drilling being able to be carried out from said floating support through said drilling riser using a drill rod train equipped with its end of drilling tools passing through said drilling riser and said guide device, said guide device being characterized in that it comprises a telescopic guide pipe comprising telescopic coaxial pipe elements (XX ′) and of diameters decreasing, pre-assembled to each other, so that said telescopic pipe elements are capable of sliding in the axial direction (XX ') a other, the inner telescopic pipe element of smaller diameter being equipped at its end with a means of decohesion of the ground capable of creating a progressive depression in the ground of said telescopic guide pipe by sliding outwards said telescopic pipe elements so as to allow a drilling tool to be guided deeper into the ground at the end of said drill string.

It is understood that the progressive insertion into the ground of the guide pipe is done from an initial retracted position in which the internal telescopic pipe element of smaller diameter is returned inside the telescopic pipe elements of larger diameter. So all the telescopic pipe elements are positioned inside a larger diameter external telescopic pipe element. The progressive insertion of said decohesion means occurs by progressive sliding towards the outside of the elements of smaller diameter in those of larger diameter, and therefore first of all of the internal telescopic internal pipe element of smaller diameter then gradually telescopic pipe elements of increasing diameters, and until complete deployment of all telescopic pipe elements extending outwards.

By doing so, in the case of conventional vertical drilling, a single guide device is lowered from the surface, instead of two or even three in the prior art, which represents a considerable time saving in the case of drilling in deep sea, for example by 2000, 3000m, or even more, because they must be descended successively. In addition, in the event of ground instability, or in the event of untimely inflow of water occurring at a shallow depth below the seabed, the casing being continuous over its entire length, the risk of collapse is considerably reduced , or even radically removed. Finally, the cementing operations of the device according to the invention are reduced to a minimum, since it is no longer necessary to perform it after each installation of a casing in the previous casing, as is the case in the casings of the prior art. Indeed, the cementing is carried out in only one time after complete deployment of the telescopic device.

In a preferred embodiment, said inner pipe element of smaller diameter has a diameter substantially identical to that of said drilling riser. In a particular embodiment, said soil decohesion means are constituted by a multi-perforated cover making it possible to launch water or mud by injection under high pressure.

More particularly, said telescopic guide pipe comprises at least 3 elements, of coaxial telescopic pipe.

More particularly still, each of said coaxial-telescopic pipe elements has a length of 50 to 300 meters, preferably 100 to 200 meters and said deployed guide pipe has a length of 150 to 600 meters, preferably 200 to 300 meters. The guiding device according to the invention is first prefabricated on the ground, then put into a retracted configuration by introducing the pipes into each other so as to reduce the total length to a minimum, then put into the water and equipped with flotation elements, then towed on site to the axis of the drilling derrick, and finally cabin so that the upper part of said telescopic pipe can be gripped by the handling tool installed at the end of the drill string handled by the derrick, the assembly then being lowered in one go, in vertical configuration towards the guide base resting on the sea floor. Being prefabricated on the ground, each of said telescopic pipe elements will be produced by assembling lengths successive pipes, said pipes being simply butt welded in a conventional manner as in the case of the manufacture of pipelines . It is thus not necessary to reinforce the ends of each of the unit lengths of 12 m, because no thread is machined there, and the assembly then has an optimal diameter and markedly reduced compared to the prior art.

The term “retracted telescopic guide pipe” means that the various preassembled telescopic pipe elements are such that those of small diameters are brought inside those of larger diameters.

According to a second aspect which makes it possible to solve the problem of installing a guide device in a deviated drilling application in the height of the slice of water, the present invention provides a guide device useful in an offshore drilling installation, installation in which at least one drilling riser extends from a floating support to said guidance device to the bottom of the sea, said drilling riser gradually deviating 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 at 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 at 45 °, said guide device being characterized in that it comprises a said telescopic guide pipe in a position sunk into the ground in the which said retracted telescopic guide pipe or said external telescopic pipe member when said telescopic pipe is fully deployed successively:

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

. a curved intermediate portion of sunken into the subsoil of the sea floor along a large radius of curvature, preferably a radius of curvature greater than 500 m, and. a substantially linear rear portion driven into the basement of the sea floor at a said given inclination α, said telescopic guide pipe or said external telescopic element cooperating with controlled driving means allowing the driving of said guide pipe telescopic retracted into the sea floor when said retracted telescopic guide pipe is towed to the sea bottom at its front end, from an initial position where said retracted telescopic guide pipe rests entirely over the sea bottom in a substantially horizontal position, up to a so-called sunken position in the sea floor underground.

The curvature of the telescopic guide line is therefore formed by the controlled sinking of the guide line. Due to significant length of said guide pipe in the retracted position, each of the retracted section will take the same curvature, without generating significant efforts within the assembly.

The means of driving in the retracted telescopic guide pipe make it possible to obtain, by driving in the pipe, a curvature of the pipe with a large radius of curvature to 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 retracted telescopic 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 bottom of the the sea when it is towed. Said base prevents the front end of said retracted telescopic 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 retracted telescopic guide pipe is put into place in a said initial position resting substantially horizontally and in a straight line on the seabed, said retracted telescopic guide pipe cooperating with said controlled insertion means, and

- Pulling is carried out at the bottom of the sea from said front end of said telescopic guide pipe, preferably in the axial longitudinal direction of said telescopic 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. In the case of drilling deviated in the height of the slice of water, said drilling riser gradually deviates 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. , the drilling being able to be carried out from said floating support through said drilling riser and said guiding device so that the drilling well begins in the sea bottom at a given inclination oc relative to the vertical, preferably from 10 to 80 °.

The present invention also relates to a method for producing a drilling installation according to the invention, characterized in that steps are carried out in which:

a telescopic guide device is produced according to a method according to the invention, and

- The connection of at least said drilling riser is made to said front end of the telescopic guide pipe resting on the bottom of the sea.

The present invention finally relates to a drilling method using a drilling installation according to the invention characterized in that drilling operations are carried out and a drilling well is constructed in deploying rod trains cooperating with drilling tools and columns of tubes or casings, through a said drilling riser and a said telescopic guide device according to the invention sunk into the sea floor. It is understood more precisely that the drill string makes it possible firstly to deploy the drilling tools, then to deploy the tube elements, called "columns of tubes or casings" which constitute the wellbore as the drilling progresses and their setting in place in the bottom of the sea. 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:

FIG. 1 represents a telescopic guide device made up of elements of telescopic coaxial pipes shown in the retracted position, in the case of conventional vertical drilling,

• Figures 2, 3 and 4 are sectional side views detailing the telescopic guide device in the retracted position, shown in a straight line, respectively at the time of its deposit at the bottom of the sea, at the start of the drilling operation by launching and during drilling with the rotary tool,

• Figure 5 is a sectional side view of the partially deployed telescopic guide device, shown in a straight line, detailing the thrust forces exerted on the various telescopic elements and on the drilling tool, in the case of conventional vertical drilling,

FIG. 6A is a side view of a DTU type surface support equipped with a drilling riser connected to a guidance device preinstalled on the seabed for deep water drilling deviated in the height of the slice of water,

FIG. 6B represents a telescopic guide device made up of 3 elements of telescopic coaxial pipes deployed, in the case of a bore deviated in the height of the water section, FIGS. 7 and 8 are side views of a guiding device associated with an anchor ensuring penetration into the ground, represented respectively before and after penetration into the seabed,

FIGS. 9 and 10 are sections in side view along the respective section planes AA and BB of the guide device,

• Figures 11 and 12 are side views of a guide device fitted with lateral fins ensuring variable penetration into the ground, shown respectively before and after penetration into the seabed, • Figure 13 is a view from the left of the guide device according to FIG. 6 detailing the lateral fins,

• Figure 14 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, • Figure 15 is the sectional view of the current section relating to figure 14,

• Figures 16 and 12 are side views of a structure associated with the guide device according to Figures 7 and 8, limiting the penetration during penetration into the ground, shown respectively before and after said penetration into the seabed ,

• Figures 18 and 19 are the sections according to the CC and DD plans relating to Figure 16.

FIG. 20 is a side view of a drilling platform installed vertical to the drilling base of a future well, detailing the sequence of installation of a telescopic guide device in the retracted position, which has was successively prefabricated ashore, then fitted with floats and towed to site, then cabin in vertical position, then finally resuspended by the drilling platform, by means of a gripper installed at the end of a drill string, the assembly then being ready to be lowered along guide lines towards said drilling base.

For clarity of explanation, the play between two adjacent telescopic pipe elements has been considerably increased on the figures, so as to facilitate the understanding of the functioning of the sliding, guiding and sealing means.

In Figure 1 there is shown a guide device consisting of 3 telescopic pipe elements 3a, 3b, 3c in the rectilinear position, implemented as part of a conventional vertical drilling. Said guide device 3, consisting of three telescopic pipe elements 3a, 3b and 3c, is suspended from a drilling riser 2 handled by the derrick on the surface, and descended towards a drilling base 45 resting on the bottom of the sea 4 A first guide means 47 has been lowered beforehand along the guide cables 48, to come to center on guide posts 46, and finally rest directly on the base. For clarity of the drawing, the guide device 3 has been shown in a position slightly above said base 45, just before being deposited on the latter. This first guide means 47 comprises a funnel shape with a diameter slightly greater than the outside diameter of the portion 3a of the guide device 3 and which, collaborating with the latter, thus makes it possible to guide it during its descent towards the base 45. During the descent, the guide device 3 is integral with a second guide means 49 embedded in the latter at the level of the plane DD and itself guided along the guide lines 48.

As shown in FIG. 20, the guide device 3 was prefabricated on the ground, then the various elements were tucked into each other, so that the length of the assembly thus retracted is as short as possible, then the guide device is launched and equipped with floats 50. It is then towed to site and, near the drilling platform 1, said guide device is hut by removing the front floats, then transferred to the vertical to the axis of the derrick where it is taken up by the rod train 2 fitted at its end with a gripping tool. In a preferred variant of the invention, the drilling platform 1 is replaced by a simple surface vessel, preferably with dynamic positioning, the guiding device 3 once a cabin is then suspended by a cable connected to an installed winch on board of ship. The guide device is then lowered to the cable in a simple pendulum, preferably without guide lines, then inserted into the drilling base. The beginning of penetration is carried out by launching, the hydraulic power being supplied by the surface vessel and transmitted to the bottom, for example by a flexible pipe. When the launch is no longer effective, the surface vessel suspends its operation, the installation will then be terminated by the drilling platform as soon as it arrives on site, vertically above said well to be drilled. By doing so, the cost of the operation of setting up the casing is radically reduced, since the daily cost of the surface vessel required represents a small fraction of the cost of a drilling platform capable of drilling in depths of water of 3000m, 4000m, or even more. In addition, the required drilling machine will be of lower power, therefore of lower cost, since it will not have to handle the telescopic guide device according to the invention, or even the unitary elements of a casing. conventional according to the prior art.

FIG. 2 represents the telescopic guide device 3 in the retracted or folded position with an orifice 31 allowing the mud and drilling debris to be evacuated at sea level. The telescopic pipe elements of said telescopic guide pipe 3 are tubular and of decreasing diameter diameter so that they can slide into each other. The intermediate telescopic pipe element 3b of the telescopic guide device 3 is provided on its front part with a sealed sliding ring 32b ensuring reduced friction guiding of the internal telescopic terminal pipe element 3c of the telescopic guide device 3 and on its rear part, a non-sealed sliding ring 33b ensuring reduced friction guidance of the external telescopic pipe element 3a of said telescopic guide device 3.

The portion 3a of the said guiding device is equipped on the front with a sealed sliding ring 32a ensuring the guiding with reduced friction of the portion 3b and is integral with the rear of the drilling riser in chain configuration 2. The portion 3c of said guide device is equipped on the front with a cover 35 pierced with multiple orifices, or even equipped with a series of nozzles, allowing, by simple injection of water or mud under very high pressure, destroying the cohesion of the soil and thus allowing the start of the well by simple launching, and on the rear, of an unsealed sliding ring 33c.

Additional sliding rings 34 are advantageously installed, at regular or irregular intervals, respectively between the portions 3a-3b and 3b-3c so as to avoid that, when the portions of the guide device are strongly curved, as indicated in FIG. 1 , the outer wall of the inner guide, for example 3b, does not rub directly on the inner wall of the portion 3a. In the case of portion 3b, these sliding rings 34 are secured to said telescopic portion 3b so as to have a high friction with respect to this portion 3b, that is to say that they have the possibility of sliding when they are subjected to a significant force applying parallel to the longitudinal axis of said portion 3b. Thus, when the portion 3b slides towards the outside of 3a, the sliding ring 34 abuts against the sealed sliding ring 32a and, because it can slide under significant force, the sliding towards the outside of 3b in 3a is not prevented. At the end of sliding, all of the sliding rings 34 will be in contact with said sliding ring 32a, the sliding ring 33b itself being in contact with said sliding rings 34. Each of the sliding rings 34 is advantageously provided in its external part of an element 34 _j with reduced friction, so as to minimize the longitudinal contact forces between the walls of the various portions of the guide device 3, when the latter has a significant curvature.

FIG. 4 represents the start-up phase of drilling, the guiding device being installed at the bottom of the sea, the portions 3a, 3b and 3c being in the retracted position.

The drilling tool 36 is integral with the lower end of the drill string 38 actuated from the derrick installed on the surface on the floating support. Said drilling tool 36 consists of a turbine 36 ₁ actuated by a pressurized fluid, in general a drilling mud brought by the rod train 38, actuating a tool holder 36 ₂ on the front face of which the tools are secured. section 36 ₃ and on the barrel of which retractable cutting tools 36 ₄ are installed, represented in the retracted position in FIG. 3 and in the working position in FIG. 4. A piston 40, represented in FIG. 5 is integral with the train of rods 38 and slides inside the riser 2 so as to provide a seal between the upstream and downstream of said piston 40. Thus, at the start of sinking-drilling operation, the tool is lowered from the surface. drilling 36 secured to the end of the drill string 38, so as to reach the position described in FIG. 3. The orifice 31 is closed by a valve not shown and a fluid is sent through the drill string 38 under strong pressure. The turbine 36 _j turns in a vacuum and the fluid can only come out through the cover 35 pierced with a multitude of small holes. The launching thus created at the front of the portion 3c of the guide device, ensures the decohesion of the soil and the piston effect due to the internal overpressure, pushes forward the portion 3c, possibly causing the portion 3b of said device guide. When the launching effect is no longer sufficient to cause the advancement of the front section, the launching is stopped and the drilling tool 36 is moved forward by pushing from the surface the length of drill string 38 necessary. A centering collar 37a secured to the turbine 36j, slides freely inside the portion 3c of the guide device 3; said collar allows mud and drilling debris to pass freely, in both directions, from downstream to upstream. At the end of the advancement phase, the collar 37a comes into abutment with a ring 37b secured to the portion 3c of the guide device, inside the latter. The collar 37a and ring 37b have corresponding threaded portions, not shown, which, by simple rotation of the rod train from the surface, makes it possible to mechanically secure the body of the turbine 36j to the portion 3c of the telescopic guide device, such as shown in FIG. 4. During this advance operation of the drill string 38, we continues to inject fluid under pressure, which makes it possible to destroy, using the rotating drilling tool, the launching cap 35, but care has been taken to reopen the orifice 31, so that the mud and drilling residues come out at the bottom of the sea. To facilitate the progression of the tool 36 inside the riser and then of the portion 3c of the telescopic guide device 3, said riser as well as said guide portion have a substantially identical internal section and advantageously centralizers 38a are installed integral with the rod train and sliding freely in said riser. Such centralizers being known to those skilled in the art in the field of drilling, will not be developed in more detail here.

In FIG. 4, the drilling has started and the extendable arms of the drilling tool 36 ₄ are deployed and enlarge the drilling to a diameter corresponding at least to the diameter of the portion 3b of the guide device 3. Advantageously, the advancement of the tool by adjusting from the surface, by means of the derrick, the length of the rod train. To increase the pushing force, advantageously pressurizes from the surface the annular between the drilling riser and the rod train 38. Thus, the pressure P created upstream of the sealed piston 40, creates a thrust F which, by l 'intermediate of the drill string 38, pushes the tool forward, thereby driving the portions 3c then 3b of the telescopic guide device until complete deployment as illustrated in FIG. 1.

In the final position, the drill string is operated from the rotating surface in the unscrewing direction, so as to release the body of the ring 36j of the turbine 37 _b, thus the portion 3c of the telescopic guide device 3.

After changing the tool, drilling is then carried out in a conventional manner, after having taken care to close the orifice 31 by means of a valve, not shown, so as to recover the drilling mud on the surface for recycling in the drilling process.

To prevent the various portions 3b and 3c from being rotated during the screwing-unscrewing of the turbine body on the front end of the portion 3c, said portions 3a, 3b and 3c can be advantageously square or hexagonal tubular shapes. In the case of circular tubular shape, indexing will advantageously be integrated at the level of the sliding bearings 33.

The telescopic guide pipe 3a, 3b, 3c has been described above in an application related to vertical drilling, but it also applies to deviated drilling in accordance with FIG. 6A. The equipment and operations remain essentially the same, it being understood however that the telescopic guide pipe 3 has a curvature due to its inclined position, in accordance with the representation of FIG. 6B, the guide device 3 being made integral with the base of drilling at level AA.

In Figure 6B there is shown, in side view, a curved guide device 3, consisting of three telescopic pipe elements 3a, 3b and 3c. The telescopic pipe element 3a is embedded at the level of the plane AA in a rigid external upper structure 20 described below in connection with FIG. 17.

In FIGS. 7 to 19, the telescopic guide pipe 3 is shown in the context of a deviated drilling, that is to say in an inclined and curved position on the one hand, and on the other hand in the retracted position, this is ie with the different telescopic pipe elements 3a, 3b, 3c, the smallest inside the largest. This is why in the following description when reference is made to said guide pipe, it is a telescopic guide pipe in the retracted position, ie the telescopic pipe elements of smaller diameters being all slid inside the external telescopic pipe element. When reference is made to elements cooperating with said telescopic guide pipe, it is the element cooperating with the external telescopic pipe element 3a, in FIGS. 1 to 5.

FIG. 6A is a side view of a DTU-type surface support 1 equipped with a drilling machine 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 _t . The structure 3 _{4 shows} diagrammatically the means of controlled insertion. A subsea well control assembly 2 ₂ is associated with this input to the well and allows the well to be closed 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 retracted telescopic guide device 3 so that the drilling well starts in the sea bottom at a given inclination oc relative to the horizontal, preferably from 10 to 80 °.

The controlled insertion means 3 ₄ , 5 _α -5 ₃ , 7 ^ 7 ^ 8-9, 13 described in FIGS. 7 to 19 allow the said retracted telescopic guide pipe 3 to be pushed into the seabed when said retracted telescopic guide pipe 3 is towed T to the bottom of the sea at its front end 3 _{l 3}

- from an initial position A1 where said retracted telescopic guide pipe 3 rests entirely over the sea floor in a substantially horizontal position, - to a sunken position A2 in the basement of the sea floor, position in which said retracted telescopic guide pipe 3 successively comprises:

. a front end 3 _t resting substantially horizontally on the bottom of the sea,. a curved intermediate portion of the retracted telescopic guide pipe driven into the subsoil of the sea floor with 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 retracted telescopic guide pipe 3 pressed into the basement of the sea floor according to a said given inclination α. In a first preferred embodiment of the invention, said controlled insertion means comprise:

- a 5 _t front sole placed on the sea bottom and supporting said front end _X of the retracted telescopic 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 retracted telescopic guide pipe and integral with it, the surface of which is smaller than that of said front sole 5 _ls preferably several said intermediate soles 5 ₂ , 5 ₃ distributed along said intermediate portion 3 ₂ and rear portion 3 ₃ of said retracted telescopic guide line 3 whose surface is smaller and smaller compared 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 able to sink into the ground under the effect of said traction from said front end 3 _t .

It is understood that in the first preferred embodiment described above, in connection with FIG. 6B, said flanges in fact support the outer telescopic pipe element of larger diameter 3a.

FIG. 7 illustrates this first version of the guiding device according to the invention, in which the guiding device is towed to the site by means of a cable 10 connected to the front of the guiding 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 VRYHOFF (Holland). The front part 3 _α of the guide device is integral with a sole 5 ₁ of large surface area and resting on the seabed so as to limit penetration into the ground. In the same way, footings 5 ₂ , 5 ₃ of smaller dimensions are distributed along the retracted telescopic guide pipe, their bearing surface decreasing as one approaches the rear 3 ₃ of said conduct guide. The front 3 ₁ 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 Figure 8. By exerting traction on the cable towing 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 _l being large, the front of the guide device remains on the surface and the mooring 6 stabilizes the assembly so that the axis of the guide device remains substantially horizontal, therefore parallel at the bottom of the sea 4.

One method of producing a guide device of this type consists in pulling the front end 3 _X of said retracted telescopic guide pipe 3 until said intermediate flanges 5 ₂ , 5 ₃ are found pressed into the ground becomes deeper and 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.

In another preferred embodiment of the invention, illustrated in FIGS. 11, 12 and 13, said controlled insertion means comprise at least one deflector 7 _{l 3} 7 ₂ , 7 ₃ secured to the external telescopic pipe element of said telescopic guide pipe 3 in said intermediate portion 3 ₂ or said rear portion 3 ₃ of the telescopic external guide pipe element comprising planar 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 a horizontal rectilinear position, 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 sea bottom, said deflector 7 _{l 3} 7 ₂ , 7 ₃ being inclined of an angle oc _{l 5} 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 position depressed A2 in the bottom of the sea These deflectors, 7 ₂ , 7 ₃ make it possible to control the curvature of the retracted telescopic guide pipe driven into the sea floor because, once said deflectors are in a horizontal position, as shown in FIG. 12, they prevent the further depression of the pipe and stabilize it in the desired position A2. It is understood that it is the spacing and the inclination of the deflectors which determine the curvature and more generally the shape of the telescopic guide pipe retracted in the depressed position A2.

Preferably, the guide device comprises a plurality of deflectors 7 ^ 7 ₂ , 7 ₃ distributed along the external pipe element of said telescopic guide pipe, inclined at angles oc _{l 3} cc ₂ , ₃ , reducing as said deflector 7 _d -7 ₃ is closer to said front end 3 _t .

The guide pipe is therefore equipped with several deflectors 7 _j -7 ₃ integral with the guide pipe and oriented oc _j -o ^ relative to the axis XX 'of the latter. The deflector 7 _j -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 guide device as illustrated in Figure 12. This angle is adjusted beforehand during the manufacture of the guide device, so as to act as the anchor 13 described in Figures 7, 8 ie to create a depression of the retracted telescopic guide pipe, 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 cable 10, that is to say substantially parallel to the bottom of the sea 4, or even substantially horizontal, 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 a ₁ - oc ₃ which decreases as we get closer to the front end 3 _{l 3} as illustrated in FIG. 11. When penetrating 24 into the ground, we then obtain, as soon as all of the deflectors 7 _! ~ 7 ₃ have reached a substantially horizontal position, the desired curvature, as illustrated in FIG. 12. A method of producing a guide device according to this second embodiment consists in pulling T from the front end 3 of said retracted telescopic guide pipe 3 until said deflectors 7 _{l 3} 7 ₂ , 7 ₃ are driven into the ground in a horizontal position to obtain said desired curvature preferably at a radius of curvature greater than 500 m preferably still between 500 and 1000 m.

FIGS. 14 and 15 illustrate another preferred version of the invention in which said controlled driving means comprise: - secondary pipes 8 for launching fluid 18 integral with the external telescopic pipe element of said guide pipe 3, extending parallel to and beneath it, and

- Said secondary pipes 8 having a reduced diameter compared to that of said elements of said telescopic 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 a said fluid 18 under pressure. Preferably, said secondary pipes 8 are connected by their ends 8 _{] 3} 8 ₂ to the front and rear ends 3 _{l 5} 3 _{3 of} said external pipe element of said telescopic guide pipe and communicate with said front ends 3 _t and rear 3 ₃ so that he it is possible to supply them by a same supply line 19 from said front end 3 of said telescopic guide pipe 3.

In FIG. 15, two secondary pipes 8 have been shown arranged symmetrically with respect to the guide pipe 3.

In FIG. 14, 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

19, 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 retracted telescopic guide pipe 3 to the bottom of the sea and

- a liquid under pressure is preferably injected, preferably water, into said secondary pipes 8 and preferably into said telescopic 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 retracted telescopic guide pipe 3. In another preferred version of the invention illustrated in FIGS. 16 to 19, any of the devices according to FIGS. 7 to 15, a rigid external upper structure 20, embedded on the front 3 _t of the telescopic external pipe element of the guide pipe 3, the assembly resting on the ground by means of flanges side 21, as illustrated in FIG. 19, detailing the section according to the plan DD.

More specifically, the guide device comprises:

a rigid external upper structure 20 covering and now rectilinear said retracted telescopic 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 retracted telescopic guide pipe 3 to sink into the ground when the latter is towed T, and - at least one link 17 _l3 17 ₂ , 17 ₃ connecting at least the rear part

3 ₃ of the external telescopic pipe element of said telescopic guide pipe retracted to said external structure 20 so as to prevent it from sinking beyond 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 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 _X of the external telescopic pipe element of said retracted telescopic 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. 18 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 ^ 17 ₂ , 17 ₃ distributed along the external telescopic pipe element of the telescopic guide pipe 3 and having an increasing length 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 a said 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 Figure 17. These flexible connections 17 _t -l 7 ₃ are distributed along the guide pipe, uniformly or not, and have a variable length, decreasing when one approaches the front 3 _t the external telescopic pipe element of the guide pipe. Their position and length are determined, so that at the end of penetration into the ground, when they are all under tension, the desired curve is obtained as illustrated in FIG. 17. 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 for producing a guide device of this type essentially consists in pulling T from the front end 3 _X of the external pipe element of said telescopic guide pipe 3 of said rigid external structure 20 integral with said guide line until said link (s) 17 _d -17 ₃ prevent further depression of at least said rear portion 3 ₃ of said retracted telescopic guide line to obtain the desired curvature R preferably a greater radius of curvature 500 m, more preferably between 500 and 1000 m.

All these controlled insertion means δ ^ δ ^ 7 ^ 7 ₃ , 13, 20, 17 _J -17 ₃ according to the invention described in the different embodiments above can be implemented, either individually or in combination, the nature of the soil requiring in the case of strong cohesion extremely powerful means.

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.

In the case of the telescopic guide device, by way of illustration, the portions 3a-3b-3c have a respective diameter of 0.55 m (21 "), 0.45 m (18") and 0.40 m ( 16 ") and a length of 100 to 150 m each. By way of example, in the case of the guide device for vertical drilling as explained in FIG. 20, the telescopic pipe elements are five in number, of respective diameter 30 ", 24", 21 "l / 2, 18" 3/4 and 16 ", each of the telescopic pipe elements measuring approximately 200m, which represents a total deployed length of approximately 1000m. A set of casings according to the prior art would have the same internal diameter of 16 "and the respective decreasing diameters would then be 36", 30 ", 24", 20 "and 16". The set would also measure around 1000m, but since each casing element extends downwards from the sea floor level, the set represents a cumulative length of around 3000m of pipe, which then represents a steel weight approximately 2 to 2.5 times greater than the steel weight required to make the telescopic casing according to the invention.

Claims

1. Guide device (3) of an offshore drilling installation comprising at least one drilling riser (2) extending from a floating support (1) to said guide device (3) at the bottom of the sea (4), said drilling being able to be carried out from said floating support, using a drill rod train (38) equipped at its end with drilling tools (36) passing through said drilling riser ( 2) and said guide device (3), said guide device (3) being characterized in that it comprises a telescopic guide pipe (3) comprising telescopic pipe elements (3a, 3b, 3c) coaxial (XX ¹ ) and of decreasing diameters, preassembled to each other so that said telescopic pipe elements are able to slide in the axial direction (XX ') one inside the other, the internal telescopic pipe element (3c) of smaller diameter being equipped at its end with a means of th cohesion (35) of the ground capable of creating a progressive depression in the ground of said telescopic guide pipe (3) by sliding outwards of said telescopic pipe elements (3a, 3b, 3c) to thus allow to guide more deeply in the ground a drilling tool (36) at the end of said rod train (38).

.

2. Guidance device according to claim 1 characterized in that said inner pipe element (3c) of smaller diameter has a diameter substantially identical to that of said drilling riser (2) -

3. Guide device according to claim 1 or 2 characterized in that said soil decohesion means (35) are constituted by a multi-perforated cover allowing the launching of water or mud by injection under very high pressure.

4. Guide device according to one of claims 1 to 3 characterized in that it comprises at least 3 telescopic coaxial pipe elements (3a, 3b, 3c).

5. Device according to one of claims 1 to 4 characterized in that each of said coaxial-telescopic pipe elements (3a, 3b, 3c) have a length of 50 to 300 meters, preferably 100 to 200 meters and said pipe of deployed guide has a length of 150 to 600 meters, preferably 200 to 300 meters.

6. Guide device (3) according to one of claims 1 to 5 characterized in that it comprises a said telescopic guide pipe (3) useful in an offshore drilling installation in which at least one drilling riser ( 2) extends from a floating support (1) to said guide device (3) at the bottom of the sea (4), said drilling riser (2) gradually deviating from a substantially vertical position (2a) at said level floating support (1) to a substantially horizontal or tangential horizontal position (2b) at the bottom of the sea (4), said drilling being able to be carried out from said floating support through said drilling riser (2) and said guide device (3) so that the wellbore in the seabed is started at 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 takes a said telescopic guide line (3) in a depressed position (A2) in which said telescopic guide line in the retracted position (3) or the external telescopic line element (3a) when said telescopic line (3) is deployed , successively include:

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

. a curved intermediate portion (3 ₂ ) sunk into the subsoil of the sea floor according to a large radius of curvature (R), preferably a radius of curvature greater than 500 m and,

. a rear portion (3 ₃ ), substantially linear, driven into the basement of the sea floor at a given given inclination (α), said telescopic guide pipe (3) or said external telescopic element (3a) cooperating with controlled insertion means (3 ₄ , δ ^ δ ^

7 _! -7 ₃ , 8-9, 13) allowing the insertion of said guide pipe retracted telescopic (3) in the sea floor when said retracted telescopic guide pipe (3) is towed (T) to the sea bottom at its front end (3 ^, from an initial position (Al) where said retracted telescopic guide (3) rests entirely over the sea floor in a substantially horizontal position, to a so-called sunken position (A2) in the sea floor basement.

7. Guide device according to claim 6, characterized in that said retracted telescopic guide pipe (3) has a length of 100 to 600 m, preferably 250 to 450 m with said given inclination (oc) of the guide pipe from about 10 to 60 °, preferably 25 to

45 °.

8. Guide device according to claim 6 or 7, characterized in that said front end (3) 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 (3 _t ) substantially horizontally on the bottom of the sea when the latter is towed (T).

9. Guide device according to one of claims 6 to 8, characterized in that said controlled driving means comprise:

- a front sole (5 _d ) placed on the sea bottom and supporting said front end (3 _X ) 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 ) and integral with it, the surface of which is smaller than that of said front sole (5 _d ), preferably several said intermediate soles (5 ,, 5 ₃ ) distributed along said intermediate portion (3 ₂ ) and rear portion (3 ₃ ) whose surface is smaller and smaller compared to said front sole as they are closer to said rear end (3 ₃ ), and - an anchor (13) connected (12) to said rear portion (3 ₃ ) and able to sink into the ground under the effect of said traction from said front end (3 _t ).

10. Guide device according to one of claims 6 to 9, characterized in that said controlled insertion means comprise at least one deflector (7 _ls 7 ₂ , 7 ₃ ) integral with said external telescopic pipe element (3a) of said telescopic guide pipe (3) in said intermediate portion (3 ₂ ) or said rear portion (3 ₃ ) of the retracted telescopic guide pipe, comprising planar 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 a horizontal rectilinear position, and said planar surfaces of the deflectors being inclined relative to a horizontal axial plane (XX', ZZ ') of said guide pipe when that -this is in a horizontal position on the bottom of the sea, said deflector (7 _X , 7 ₂ , 7 ₃ ) being inclined at an angle (α _{l 5} oc ₂ , ₃ ) so as to create a depression of said conduit e retracted telescopic guide (3) when the latter is towed from said initial position (Al) substantially horizontal to a said pressed position (A2) in the sea floor.

11. Guide device according to claim 10, characterized in that it comprises a plurality of deflectors t ₁ , ^ ₂ , _$ ) distributed along the external telescopic pipe element (3a) of said telescopic guide pipe, said deflectors being inclined at angles (oc _{l 5} α ₂ , oc ₃ ) reducing as said deflector (7 _{l 5;} 7 ₂ _,; 7 ₃ ) is closer to said front end (3 _t ) .

12. Guide device according to one of claims 1 to 11, characterized in that said controlled driving means comprise: - secondary pipes (8) for launching fluid (18) integral with said telescopic 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 telescopic guide pipe (3) and comprising perforations ( 9) on the underside allowing a fluid (18) to be expelled towards the bottom of the sea when said secondary pipes (8) are supplied with a said fluid (18) under pressure.

13. Guide device according to claim 12, characterized in that said secondary pipes (8) are connected by their ends (8 _{l 5} 8 ₂ ) to the front and rear ends (3 _{l 3} 3 ₃ ) of said telescopic guide pipe retracted (3) and communicate with said front (3j) and rear (3 ₃ ) ends so that it is possible to supply them by the same supply line (19) from said front end (3 _d ) of said line guide (3).

14. Device according to one of claims 1 to 13, characterized in that the guide device comprises:

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

- Said external structure (20) having a central longitudinal opening on the underside allowing said retracted telescopic guide pipe (3) to sink into the ground when the latter is towed (T), and - at least one link (17 _{l 3} 17 ₂ , 17 ₃ ) connecting at least the rear part

(3 ₃ ) of the external telescopic pipe element (3a) of the telescopic guide pipe (3) 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 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 outer structure (20) being integral with said base (6) wherein said front portion (3 _j) of the guide pipe (3) is embedded.

15. Guide device according to claim 14, characterized in that it comprises a plurality of flexible links (17 _t , 17 ₂ , 17 ₃ ) distributed along the external telescopic pipe element (3a) of said pipe telescopic guide (3) and having an increasing length 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 a said rear rear portion (3 ₃ ) linear.

16. A method of producing a guide device according to claims 6 to 15, characterized in that steps are carried out in which: - a said telescopic guide pipe is put in place in the retracted position (3) in a said initial position (A1) resting substantially horizontally and rectilinearly on the seabed, said telescopic guide pipe (3) cooperating with said controlled insertion means (3 ₄ , δ ^ δ _g , 7, -7 ,, 8-9, 13), and

- Pulling (T) is carried out at the bottom of the sea of said front end (3j) of said telescopic guide pipe in the retracted position (3), preferably in the axial longitudinal direction XX 'of said guide pipe, from said initial position (Al) to a said depressed position (A2).

17. A method of producing a guiding device according to claim 16, characterized in that guiding devices according to claim 8 or 9 are used and traction is carried out (T) of the front end (3 _X ) of said retracted telescopic 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 ) of guide pipe to obtain the curvature sought (R), preferably a radius of curvature greater than 500 m more preferably between 500 and 1000 m.

18. A method of producing a guiding device according to claim 16 or 17, characterized in that a guiding device according to claim 10 or 1 1 is used and traction is carried out (T) from the front end ( 3 _t ) of said retracted telescopic guide pipe (3) until said deflectors (7 _{l 3j} 7 _25ι 7 ₃ ) are driven into the ground in a horizontal position to obtain said _desired curvature preferably at a radius curvature greater than 500 m, more preferably between 500 and 1000 m.

19. A method of producing a guide device according to one of claims 16 to 18, characterized in that a guide device according to one of claims 12 or 13 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 telescopic guide pipe (3) closed at these ends (3 _{l 3} 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).

20. A method of producing a guide device according to one of claims 16 to 19, characterized in that a guide device according to one of claims 14 or 15 is used and a traction (T) is produced. the front end (3 _X ) of said retracted telescopic guide pipe (3) of said rigid external structure (20) integral with said guide pipe until said link (s) (17 _α -l 7 ₃ ) prevent an additional depression of at least said rear part (3 ₃ ) of said retracted telescopic guide pipe (3) to obtain the desired curvature (R) preferably a radius of curvature greater than 500 m, more preferably between 500 and 1000 m.

21. offshore drilling installation comprising a drilling riser (2) extending from a floating support to a said guide device (3) according to one of claims 1 to 15 to which said drilling riser (2) is connected.

22. offshore drilling installation according to claim 21, comprising a drilling riser (2) extending from a floating support (1) to a guide device (3) according to one of claims 6 to 15, - to which said drilling riser is connected, 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 to horizontal position (2b) at the bottom of the sea, drilling can be carried out from said floating support (1) through said drilling riser (2) and said guide device (3) so that the wellbore starts in the bottom from the sea at a given inclination (α) relative to the horizontal, preferably from 10 to 80 °.

23. A method of producing a drilling installation according to claim 21 or 22 characterized in that steps are carried out in which:

a guiding device is produced according to a method according to one of claims 16 to 20, and

- We realize the connection of at least said drilling riser (2) to said front end (3 _α ) of the guide pipe resting on the seabed (4).

24. A drilling method using a drilling installation according to claim 21 or 22, characterized in that drilling operations are carried out and a drilling well is constructed by deploying drill rigs cooperating with tools drilling and columns of tubes or casings, through a said drilling riser (2) and a said guide device (3) driven into the seabed (4).