EP1525371B1 - Telescopic guide line for offshore drilling - Google Patents

Abstract

The present invention relates to a guide device for an off-shore drilling installation comprising at least one drilling riser extending from a floating support to a said guide device at the sea bottom, said drilling being performable from said floating support via said drilling riser using a drill string fitted at its end with drilling tools. According to the invention, said telescopic guide device comprises a telescopic guide pipe comprising coaxial telescopic pipe elements about an axis, the smallest-diameter innermost telescopic pipe element being fitted at its end for breaking up the ground suitable for progressively burying said telescopic guide pipe in the ground so as to enable a drilling tool to be guided more deeply into the ground.

Description

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

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

As soon as the depth of water becomes important, the exploration and exploitation of production fields, especially oilfields, is generally carried out from a floating support. This floating support generally comprises anchoring means to remain in position despite the effects of currents, winds and waves.

In the case of drilling operations, it also generally comprises means for handling the drill string, as well as guidance equipment associated with safety systems installed at the seabed.

Drilling is usually done vertically from the drill rig and then penetrates the ground vertically to heights of several hundred meters. Then, said drilling is continued to the oil slick called "reservoir", either vertically or with a gradual angular deflection, so as to reach points of said reservoir, more or less distant.

The start phase of the well is generally carried out by descending from the surface a drilling base resting on the seabed provided with guide lines to the surface, then down a length of pipe, called "casing" or casing, strong diameter, generally 0.914 m (36 ") and measuring 50 to 60 m in length, based on unit lengths of pipe approximately 12 m long assembled by screwing on the drilling platform, the level of the floor of the derrick.To withstand the efforts, each unit length of casing has at each end a zone reinforced over a length of 0.5m to 1m, consisting of an extra thickness corresponding to about 0.5 to 2 times the current thickness of the wall of said casing, the thickness in which said threading is machined. Said casing, once assembled, passing through said base, is then simply planted in the ground, generally not consolidated and the depression is often done by jetting (ie by sending water under pressure). This first casing is used to consolidate the walls of the well in the area near the seabed, and therefore serves as a guide device for a second casing, of smaller diameter and, in general, a total length of 150 to 200m, said second casing being also made by pipe assembly of 12m unit length comprising reinforced zones at the ends, has an outer diameter, including reinforced threading areas, much lower than the internal diameter of the outer casing, so that it can slide freely during installation and for the flow of cement grout can be done in the best conditions. Said second casing is then either vibrofoncured or drilled if the terrain requires it, and then cements from the surface the gap between said casings and the ground, as well as between the two said casings. During these phases, open holes are used and there is a risk of being exposed to ground instabilities, or to untimely arrival of water at shallow depths below the seabed ( "Shallow water flow"), seriously disturbing 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 drilling itself.

Thus, the multiple casings have important spaces between each said casing and the following and, furthermore, because each of said casings extends from the level of the sea floor to its lowest end, this implies that sea level and over the entire height of the first and subsequent casings, radially two, three or even four or more successive thicknesses of casing are observed, which will in fact be useless in the pursuit of operations, because in the main phase of drilling and well exploitation, a single casing thickness is required for ensure the support of downhole equipment and the tightness of the whole. These multiple casings, redundant in the zone near the seabed, are made necessary because of the manner of proceeding to start a well drilling according to the prior art, redundancy which represents a considerable amount of steel, and therefore a very important cost.

The patent is known GB-2,338,009 which describes a mode of installation of multiple elements of independent casings successively installed in each other with a reduced game. 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 external casing and intermediate casings, which reduces accordingly the amount of rubble to be evacuated and the power requirements of the drill rig and thereby are hourly cost.

The patent is known US 5307886 which describes a system and or installation mode for performing multiple casings 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 guide device for guiding the drill string and the drilling tool as deep as possible in the basement at the bottom of the sea, so as to avoid these incidents of untimely arrival of water 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, the unit lines used to make 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 Large Funds 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 setting up, ie the depression in the ground, the first casing, the second casing or the following remains acceptable, the manipulations intermediaries consisting in bringing the gripping tools back to the surface and then going down again the next casing, then represent a time considerable, therefore an immobilization cost of the extremely high drilling rig, when the water height reaches 2000, 3000 or even 4000 to 5000m or more. In addition, the cementing phases of the gap between two risers require a very important time which increases the cost of the operation by the same amount.

Another problem is to drastically reduce the quantity of steel necessary for the realization of these casings by minimizing the redundancies as well as the games between said successive casings.

On the other hand, in the case of drilling several deviated wells, it is possible to form a network of wells in the form of an umbrella from the same position of the floating support surface, which allows to group, throughout the operation field, all surface equipment in one place. Such facilities are called DTU (Dry Tree Units), ie units with dry well heads, because in this case the wellheads are collected on the surface, out of water. The 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 life of the facilities that reaches 20 to 25 years and even more.

Such deviated drilling is possible only if the tanks are deep, 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 wells whose radii of curvature of the conduits constituting the well are of the order of 500 to 1000 m.

Patents are known EP 0952300 and EP 0952301 describing methods and devices for deviated drilling by taking advantage of the water body to deviate as far as possible from the vertical of the drill rig and to rest in the seabed substantially tangentially to the horizontal.

In these patents, the guidance devices installed at the bottom of the sea penetrate into the ground and allow to ensure the priming of the wellbore in the seabed at an inclination of a given angle relative to the vertical. The guiding device is connected to the drilling machine by a pipe called "drill riser" which guides the drill string that passes through them and ensures the recovery of sludge and drilling debris.

This guide element installed at the bottom of the sea must allow to respect large radii of curvature of 500 to 1000 m and therefore must be large, while remaining very resistant to absorb the considerable efforts generated by the rod train. drilling which will also be forced to marry the same radius of curvature, which induces very high friction and risk of destabilization of the whole during drilling.

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

More precisely in EP-0952301 , the guide device comprises a conductor element called "conductor" which is actually the guide tube of the wellbore deployed from the floating support through the drill riser to a structure called "skid" resting on the bottom This structure - skid maintains 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 its deployment cooperates with drilling tools so that it sinks partially into the seabed. The establishment of such a guiding device including the driver from the floating support represents an operational constraint important. In addition, this guiding device does not allow any control of the curvature of the conductor. On the other hand, to respect a large radius of curvature, especially greater than 500 m, it is necessary for the driver to deploy tangentially horizontally for several tens of meters beyond the fulcrum which ensures its guidance on the road. skid structure.

Finally, no means are described in these patents to enable the realization of the implementation of said conductor along a large radius of curvature as necessary for the train of rods, and especially 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 driver will reach the ground only 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 excessive local curvature, because uncontrolled. In addition, the cantilever thus created may be detrimental to proper operation during drilling operations as well as throughout the lifetime that may exceed 25 years.

Another problem according to the present invention is therefore to provide a guiding device in a deviated drilling application in the height of the water slice, which can be set up in a large radius of curvature reliably, it is to say being able to control the curvature with a large radius of curvature especially greater than 500 m and whose implementation and implementation are easy to achieve.

In a first aspect providing a solution to the problem of guiding the drill string and the drill bit as deeply as possible, the present invention provides a device for guiding an offshore drilling rig comprising at least one drill riser. extending from a floating support to said guide device at the bottom of the sea, said drilling being made from said floating support through said drill riser using a drill string equipped with its end of drilling tools passing through said drilling riser and said guiding device, said guiding device being characterized in that it comprises a telescopic guide pipe comprising coaxial telescopic pipe elements (XX ') and diameters decreasing, preassembled to each other, so that said telescopic pipe members are slidable in the axial direction (XX ') has In addition, the inner diameter telescopic pipe member being equipped at its end with a soil decohesion means capable of creating a gradual depression in the soil of said telescopic guide pipe by sliding outwardly. said telescopic pipe members to thereby allow deeper guidance in the ground of a drill bit at the end of said drill string.

It will be understood that the progressive depression in the soil of the guide pipe is made from a retracted initial position in which the smaller diameter inner telescopic pipe element is retracted into the telescopic pipe elements of the pipe. larger diameter. Thus, all telescopic pipe members are positioned within an outer telescopic pipe member of larger diameter. The gradual insertion of said decohesion means occurs by progressive sliding outwards of the smaller diameter elements in those of larger diameter, and therefore first of the smaller diameter inner telescopic inner pipe member then progressively telescopic pipe elements of increasing diameter, and until full deployment of all the telescopic pipe elements extending outwards.

By doing so, in the case of conventional vertical drilling, a single guiding device descends from the surface, instead of two or even three in the prior art, which represents a considerable saving of time in the case of drilling in deep sea, for example by 2,000, 3,000m, or more, because they must be descended successively. In addition, in case of unstable terrain, or in case of untimely arrival of water at shallow depths under the seabed, casing being continuous over its entire length, the risk of collapse is considerably reduced. or even drastically suppressed. 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 setting up of a casing in the previous case, as is the case in the casings of the prior art. Indeed, the cementing is performed in one go after complete deployment of the telescopic device.

In a preferred embodiment, said smaller diameter inner pipe member has a diameter substantially the same as that of said drilling riser.

In a particular embodiment said soil decohesion means are constituted by a multiperforated seal allowing a jetting of water or sludge by injection under high pressure.

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

More particularly, 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 initially prefabricated on the ground, then put in 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 drill rig, and finally cabane so that the upper part of said telescopic pipe can be grasped by the handling tool installed at the end of the drill string handled by the derrick, the whole then being lowered in one go, in vertical configuration towards the guide base resting on the bottom of the sea.

Being prefabricated on the ground, each of said telescopic pipe elements will be made by assembling successive lengths of pipe, 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 unit length of 12m, because no thread is machined, and the assembly then has an optimum diameter and significantly reduced compared to the prior art.

The term "retracted telescopic guide pipe" means that the various pre-assembled telescopic pipe elements are such that those of small diameters are returned inside those of larger diameters.

• une extrémité avant reposant sensiblement horizontalement sur le fond de la mer,
• une portion intermédiaire courbe de enfoncée dans le sous-sol du fond de la mer selon un grand rayon de courbure, de préférence un rayon de courbure supérieur à 500 m, et
• une portion arrière sensiblement linéaire enfoncée dans le sous-sol du fond de la mer selon une dite inclinaison donnée α,

ladite conduite de guidage télescopique ou ledit élément télescopique externe coopérant avec des moyens d'enfoncement contrôlé permettant l'enfoncement de ladite conduite de guidage télescopique rétractée dans le fond de la mer lorsque ladite conduite de guidage télescopique rétractée est tractée au fond de la mer à son extrémité avant, depuis une position initiale où ladite conduite de guidage télescopique rétractée repose entièrement par-dessus le fond de la mer dans une position sensiblement horizontale, jusqu'à une dite position enfoncée dans le sous-sol du fond de la mer.According to a second aspect making it possible to solve the problem of setting up a guiding device in a deviated drilling application in the height of the water wafer, the present invention provides a useful guide device in an offshore drilling rig, wherein at least one drill riser extends from a floating support to said guide device at sea bottom, said riser progressively deviating from a substantially vertical position at said floating support to a substantially horizontal or tangential position horizontally at the bottom of the sea, said drilling being possible from said floating support to through said drilling riser and said guide device so that the wellbore in the seabed is initiated at a given inclination α with respect to the horizontal preferably from 5 to 60 °, more preferably 25 at 45 °, said guiding device being characterized in that it comprises a said telescopic guide pipe in a recessed position in the ground in the which said retracted telescopic guide pipe or said outer telescopic pipe element when said telescopic pipe is fully deployed comprises successively:

• a front end resting substantially horizontally on the bottom of the sea,
• a curved intermediate portion of sunken in the basement of the seabed along a large radius of curvature, preferably a radius of curvature greater than 500 m, and
• a substantially linear rear portion sunk in the basement of the seabed according to a given inclination α,

said telescopic guide duct or said outer telescopic member cooperating with controlled driving means for driving said retracted telescopic guide duct into the seabed when said retracted telescopic guide duct is towed to the bottom of the sea; its forward end, from an initial position where said retracted telescopic guide pipe rests entirely over the seabed in a substantially horizontal position, to a said recessed position in the basement of the seabed.

The curvature of the telescopic guide pipe is thus formed by the controlled depression of the guide pipe. Due to long 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 for driving the retracted telescopic guide pipe make it possible to obtain, by driving 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 in the tangential extension of said curved portion and it is the inclination of this linear portion which determines said angle α of priming of the wellbore.

It is also understood that the term "horizontal at the bottom of the sea", a substantially horizontal position depending on the relief of the seabed.

In a particular embodiment, said guide duct has a length of 100 to 600 m, preferably 250 to 450 m with a said given inclination α of the guide duct of about 10 to 60 °, preferably 25 to 45 °. The desired curvature of the guide duct then corresponds to an inclination increase of approximately 1 ° per portion of guide pipe length of 10 m, ie a radius of curvature of approximately 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 flange so that said base maintains said front end of said guide pipe substantially horizontally on the bottom of the base. the sea when it is towed. Said base prevents the depression of the front end of said retracted telescopic guide pipe, as well as its rotation about a substantially horizontal axis perpendicular to the axis of traction.

• on met en place une dite conduite de guidage télescopique rétractée dans une dite position initiale reposant sensiblement horizontalement et de façon rectiligne sur le fond de la mer, ladite conduite de guidage télescopique rétractée coopérant avec desdits moyens d'enfoncement contrôlé, et
• on réalise une traction au fond de la mer de ladite extrémité avant de ladite conduite de guidage télescopique, de préférence dans la direction longitudinale axiale de ladite conduite de guidage télescopique, depuis ladite position initiale jusqu'à une dite position enfoncée.

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

• a said retracted telescopic guide pipe is placed in a said initial position lying substantially horizontally and rectilinearly on the seabed, said retracted telescopic guide pipe cooperating with said controlled driving means, and
• the front end of said telescopic guide duct, preferably in the axial longitudinal direction of said telescopic guide duct, is pulled 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 water portion, said drilling riser progressively deviates from a substantially vertical position at said floating support to a position substantially horizontal or tangential to the horizontal at the bottom of the sea , the drilling being possible from said floating support through said drill riser and said guide device so that the well of drilling starts in the seabed according to a given inclination α with respect to the vertical, preferably from 10 to 80 °.

• on réalise un dispositif de guidage télescopique selon un procédé selon l'invention, et
• on réalise la connexion d'au moins dudit riser de forage à ladite extrémité avant de la conduite de guidage télescopique reposant sur le fond de la mer.

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

• a telescopic guiding device is produced according to a method according to the invention, and
• at least one of said drill riser is connected to said front end of the telescopic guide pipe resting on the bottom of the sea.

Finally, the subject of the present invention is a method of drilling using a drilling rig according to the invention, characterized in that drilling operations are carried out and a borehole is constructed in deploying rod trains cooperating with drilling tools and columns of tubes or casings, through a said riser and a said telescopic guide device according to the invention driven into the seabed.

It is more precisely understood that the drill string firstly makes it possible to deploy the drilling tools, and then to deploy the elements of tubes, called "columns of tubes or casings" which constitute the wellbore as the drilling progresses. and setting them up in the bottom of the sea.

• la figure 1 représente un dispositif de guidage télescopique constitué d'éléments de conduites coaxiaux télescopiques représentés en position rétractée, dans le cas d'un forage vertical conventionnel,
• les figures 2, 3 et 4 sont des coupes en vue de côté détaillant le dispositif de guidage télescopique en position rétractée, représenté en ligne droite, respectivement au moment de sa dépose au fond de la mer, au début de l'opération de forage par lançage et en cours de forage à l'outil rotatif,
• la figure 5 est une coupe en vue de côté du dispositif de guidage télescopique partiellement déployée, représentée en ligne droite, détaillant les forces de poussée s'exerçant sur les divers éléments télescopiques et sur l'outil de forage, dans le cas d'un forage vertical conventionnel,
• la figure 6A est une vue de côté d'un support de surface de type DTU équipé d'un riser de forage connecté à un dispositif de guidage préinstallé sur le fond de la mer pour un forage en eau profonde dévié dans la hauteur de la tranche d'eau,
• la figure 6B représente un dispositif de guidage télescopique constitué de 3 éléments de conduites coaxiaux télescopiques déployés, dans le cas d'un forage dévié dans la hauteur de la tranche d'eau,
• les figures 7 et 8 sont des vues de côté d'un dispositif de guidage associé à une ancre assurant la pénétration dans le sol, représenté respectivement avant et après pénétration dans le fond marin,
• les figures 9 et 10 sont des coupes en vue de côté selon les plans de coupe respectifs AA et BB du dispositif de guidage,
• les figures 11 et 12 sont des vues de côté d'un dispositif de guidage équipé d'ailerons latéraux assurant une pénétration variable dans le sol, représenté respectivement avant et après pénétration dans le fond marin,
• la figure 13 est une vue de gauche du dispositif de guidage selon la figure 6 détaillant les ailerons latéraux,
• la figure 14 est une vue de côté d'un dispositif de guidage équipé de conduites secondaires de lançage facilitant la dé-cohésion du sol lors de la phase de pénétration dans le fond marin,
• la figure 15 est la vue en coupe de la section courante relative à la figure 14,
• les figures 16 et 12 sont des vues de côté d'une structure associée au dispositif de guidage selon les figures 7 et 8, limitant l'enfoncement lors de la pénétration dans le sol, représenté respectivement avant et après ladite pénétration dans le fond marin,
• les figures 18 et 19 sont les sections selon les plans CC et DD relatifs à la figure 16.
• la figure 20 est une vue de côté d'une plateforme de forage installée à la verticale de l'embase de forage d'un futur puits, détaillant la séquence d'installation d'un dispositif de guidage télescopique en position rétractée, lequel a été successivement préfabriqué à terre, puis équipé de flotteurs et remorqué sur site, puis cabané en position verticale, puis enfin repris en suspension par la plateforme de forage, au moyen d'un préhenseur installé à l'extrémité d'un train de tiges, l'ensemble étant alors prêt à être descendu le long de lignes guides vers ladite embase de forage.

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

• the figure 1 represents a telescopic guiding device consisting of telescopic coaxial pipe elements shown in the retracted position, in the case of conventional vertical drilling,
• the Figures 2, 3 and 4 are cross-sectional views detailing the telescopic guidance device in the retracted position, shown in a straight line, respectively at the time of its removal to the seabed, at the beginning of the jetting drilling operation and while drilling at the rotary tool,
• the figure 5 is a cross-sectional view of the partially deployed telescopic guide device, shown in a straight line, detailing the thrust forces on the various telescopic elements and on the drill bit, in the case of conventional vertical drilling ,
• the Figure 6A is a side view of a DTU type surface support equipped with a drill riser connected to a guide device preinstalled on the sea floor for deep water drilling deflected into the height of the slice of water ,
• the Figure 6B represents a telescopic guiding device consisting of 3 telescopic coaxial pipe elements deployed, in the case of a deviated drilling in the height of the slice of water,
• the Figures 7 and 8 are side views of a guide device associated with an anchor ensuring penetration into the ground, respectively represented before and after penetration into the seabed,
• the Figures 9 and 10 are side view cuts according to the respective sectional planes AA and BB of the guiding device,
• the Figures 11 and 12 are side views of a guide device equipped with lateral fins providing variable penetration into the ground, respectively before and after penetration into the seabed,
• the figure 13 is a left view of the guiding device according to the figure 6 detailing the side fins,
• the figure 14 is a side view of a guidance device equipped with secondary jetting pipes facilitating the de-cohesion of the soil during the phase of penetration into the seabed,
• the figure 15 is the sectional view of the current section relating to the figure 14 ,
• the figures 16 and 12 are side views of a structure associated with the guiding device according to the Figures 7 and 8 , limiting the depression during penetration into the ground, respectively represented before and after said penetration into the seabed,
• the Figures 18 and 19 are the sections according to the plans CC and DD relating to the figure 16 .
• the figure 20 is a side view of a drilling rig installed vertically from the well base of a future well, detailing the sequence of installation of a telescopic guidance device in the retracted position, which has been successively prefabricated at earth, then equipped with floats and towed on site, then cabané in vertical position, then finally resumed in suspension by the drilling platform, by means of a gripper installed at the end of a drill string, the whole being then ready to be lowered along guide lines to said drilling base.

For the sake of clarity, the clearance between two adjacent telescopic pipe elements has been considerably magnified on the Figures, so as to facilitate the understanding of the operation of the sliding means, guiding and sealing.

In the figure 1 there is shown a guide device consisting of 3 telescopic pipe elements 3a, 3b, 3c in a straight position, implemented in the context of a conventional vertical drilling. Said guiding device 3, consisting of three telescopic pipe elements 3a, 3b and 3c, is suspended from a drill riser 2 handled by the surface derrick, and down to a drilling base 45 resting on the bottom of the sea 4 A first guiding means 47 has been previously lowered along the guide cables 48, to be centered on guide posts 46, and finally rest directly on the base. For the sake of clarity, the guiding 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 has a funnel shape with a diameter slightly greater than the outside diameter of the portion 3a of the guiding device 3 and which, collaborating with the latter, thus makes it possible to guide it as it descends towards the base 45. During the descent, the guide device 3 is secured to a second guide means 49 embedded in the latter at the plane DD and itself guided along the guide lines 48.

As shown on the figure 20 , the guiding device 3 was prefabricated on the ground, then the various elements were retracted into each other, so that the length of the assembly thus retracted is as low as possible, then the guiding device is launched and equipped with floats 50. It is then towed on site and, near the drilling platform 1, said guide device is cabane by removing the floats before, then transferred to the vertical axis of the derrick where it is taken by the rod train 2 equipped at its end with a gripper tool.

In a preferred embodiment of the invention, the drilling platform 1 is replaced by a simple surface vessel, preferably dynamically positioned, the guide device 3 once cabane is then resumed in suspension by a cable connected to a winch installed on board of ship. The guide device is then lowered to the cable as a simple pendulum, preferably without guide lines, and then inserted into the drilling base. The beginning of penetration is carried out by launching, the hydraulic power being provided by the surface vessel and transmitted to the bottom, for example by a flexible pipe. When the jetting is no longer effective, the surface vessel suspends its operation, the installation will then be completed by the drilling platform upon arrival on site, vertical to said well to be drilled. In doing so, the cost of the casing installation operation is drastically reduced, as the daily cost of the required surface ship is a small fraction of the cost of a drilling rig capable of drilling into depths. 3000m water, 4000m or more. In addition, the drill rig required will be of lower power, and therefore of a lower cost, because it will not have to manipulate the telescopic guide device according to the invention, nor even the single elements of a casing. conventional according to the prior art.

The figure 2 represents the telescopic guiding device 3 in the retracted or folded position with an orifice 31 allowing the sludge and the drilling debris to be evacuated at the level of the sea floor. The telescopic pipe elements of said telescopic guide duct 3 are tubular and of diameter decreasing in size so as to slide into each other. The telescopic intermediate pipe element 3b of the telescopic guide device 3 is provided on its front part with a sealed sliding ring 32b providing the reduced-friction guiding of the terminal telescopic inner pipe element 3c of the telescopic guide device 3. and on its rear part, a non-sealing sliding ring 33b providing reduced frictional guiding of the outer telescopic pipe element 3a of said telescopic guide device 3.

The portion 3a of said guiding device is equipped on the front with a sealed sliding ring 32a ensuring the reduced-friction guiding of the portion 3b and is integral with the rear of the drill riser in chain configuration 2.

The portion 3c of said guide device is equipped on the front with a lid 35 pierced with multiple orifices, or equipped with a series of jets, allowing, by simple injection of water or mud under very high pressure, destroying the cohesion of the soil and thus allow the start of the well by simply launching, and on the back, a non-sealed sliding ring 33c.

Complementary sliding rings 34 are advantageously installed, at regular intervals or not, respectively between the portions 3a-3b and 3b-3c so as to avoid that, when the guiding device portions are strongly curved, as indicated on FIG. figure 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 the 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 they have the possibility of sliding when they are subjected to a major force applying parallel to the longitudinal axis of said portion 3b. Thus, when the portion 3b slides outwardly of 3a, the sliding ring 34 abuts against the sealed sliding ring 32a and because it can slide under significant stress, the outward sliding of 3b in 3a. is not prevented. At the end of sliding, all 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 a member 34 ₁ 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.

The figure 4 represents the start phase of the drilling, the guide 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 surface-mounted derrick on the floating support. Said drilling tool 36 consists of a turbine 36 ₁ actuated by a fluid under pressure, generally a drilling mud brought by the rod train 38, actuating a tool holder 36 ₂ on the front face of which are secured the tools of section 36 ₃ and on the shaft of which are installed retractable cutting tools 36 ₄ , shown in the retracted position on the figure 3 and in working position on the figure 4 . A piston 40, shown on the figure 5 is secured to the drill string 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 beginning of the sinking-drilling operation, the drill bit 36 that is integral with the end of the drill string 38 is lowered from the surface, so as to reach the position described on FIG. figure 3 . The orifice 31 is closed by a valve that is not shown and a fluid under high pressure is sent through the drill string 38. The turbine 36 ₁ rotates in the vacuum and the fluid can come out only through the seal 35 pierced with a multitude of small holes. The jetting thus created at the front of the portion 3c of the guiding device, ensures the loosening of the soil and the piston effect due to the internal overpressure, pushes the portion 3c forward, possibly causing the portion 3b of said device guidance.

When the jetting effect is no longer sufficient to cause forward movement of the frontal section, the jetting is stopped and the drilling tool 36 is moved forward by pushing from the surface the length of the shank 38 necessary. A centering collar 37a secured to the turbine 36 ₁ slides freely inside the portion 3c of the guide device 3; said collar freely passes the sludge and the drilling debris, in both directions, from downstream to upstream. At the end of the advancement phase, the collar 37a abuts with a ring 37b integral with the portion 3c of guiding 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, mechanically secures the body of the turbine 36 ₁ to the portion 3c of the telescopic guide device, as shown on the figure 4 . During this operation in advance of the drill string 38, one continues to inject fluid under pressure, which allows to destroy using the rotary drilling tool, the opening cap 35, but we have taken care to reopen the orifice 31, so that sludge and drilling residues stand out at the bottom of the sea.

To facilitate the progression of the tool 36 inside the riser and then the portion 3c of the telescopic guide device 3, said riser and said guide portion have a substantially identical inner section and the centralizers 38a are advantageously installed. secured to the rod train and sliding freely in said riser. Such centralizers being known to those skilled in the field of drilling, will not be developed in more detail here.

In the figure 4 , the drilling has begun and the extensible arms of the drilling tool 36 ₄ are deployed and enlarge the borehole to a diameter corresponding at least to the diameter of the portion 3b of the guiding device 3. Advantageously control the advancement of the tool by adjusting from the surface, by means of the derrick, the length of the shank. To increase the thrust force, it is advantageously pressurized from the surface annular between the drill riser and the rod train 38. Thus, the pressure P created upstream of the sealed piston 40, creates a thrust F which, by intermediate of the drill string 38, pushes the tool forward, thereby driving the portions 3c and 3b of the telescopic guide device until complete deployment as shown in the figure 1 .

In final position, the drill string is operated from the rotating surface in the unscrewing direction, so as to release the body of the turbine 36 ₁ from the ring 37 _b , thus of the portion 3c of the telescopic guiding device 3.

After tool change, the drilling is then carried out in a conventional manner, after taking care to close the orifice 31 by means of a not shown valve, so as to recover the surface drilling muds 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 may be advantageously square or hexagonal tubular shapes. In the case of circular tubular shape, indexing will advantageously be integrated at 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 in deviated drilling in accordance with the Figure 6A . The equipment and operations remain substantially 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 the Figure 6B , the guide device 3 being secured to the drill base at the plane AA.

In the 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 plane AA in a stiff outer upper structure 20 described later in connection with the figure 17 .

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

The Figure 6A is a side view of a surface support 1 of the DTU type equipped with a drilling rig and processing equipment. A drill riser 2 in a chain configuration is connected to a guide pipe 3 by means of an underwater automatic connector 2 ₁ . Structure 3 ₄ schematizes the controlled driving means. A subsea well control assembly 2 ₂ is associated with this inlet of the well and allows to close the well in case of eruption. The drilling is carried out conventionally from the surface through the drill riser 2 and through the guiding device 3-3 ₄ , until reaching the reservoir.

• depuis une position initiale A1 où ladite conduite de guidage télescopique rétractée 3 repose entièrement par-dessus le fond de la mer dans une position sensiblement horizontale,
• jusqu'à une position enfoncée A2 dans le sous-sol du fond de la mer, position enfoncée dans laquelle ladite conduite de guidage télescopique rétractée 3 comprend successivement :
  • une extrémité avant 3₁ reposant sensiblement horizontalement sur le fond de la mer,
  • une portion intermédiaire courbe de conduite de guidage télescopique rétractée enfoncée dans le sous-sol du fond de la mer selon un grand rayon de courbure, de préférence un rayon de courbure supérieur à 500 m et,
  • une portion arrière sensiblement linéaire inclinée 3₃ à l'extrémité arrière de ladite conduite de guidage télescopique rétractée 3 enfoncée dans le sous-sol du fond de la mer selon une dite inclinaison donnée α.

Said drilling riser 2 progressively deviates from a substantially vertical position 2a at said floating support 1 to a position substantially horizontal or tangential to the horizontal 2b at the bottom of the sea, the drilling being possible from said floating support 1 to through said drill riser 2 and said retracted telescopic guide device 3 so that the wellbore begins in the seabed at a given inclination α with respect to the horizontal, preferably from 10 to 80 °.
The controlled driving means 3 ₄ , 5 ₁ -5 ₃ , 7 ₁ -7 ₃ , 8-9, 13 described in FIGS. Figures 7 to 19 allow depression of said retracted telescopic guide pipe 3 in the seabed when said retracted telescopic guide pipe 3 is pulled T at the bottom of the sea at its front end 3 ₁

• from an initial position A1 where said retracted telescopic guide pipe 3 rests entirely over the seabed in a substantially horizontal position,
• to a depressed position A2 in the basement of the seabed, a depressed position in which said retracted telescopic guide pipe 3 comprises successively:
  • a front end 3 ₁ substantially horizontally resting on the bottom of the sea,
  • a curved intermediate portion of retracted telescopic guide pipe sunk into the basement of the seabed along a large radius of curvature, preferably a radius of curvature greater than 500 m, and
  • a substantially linear rear portion inclined 3 ₃ to the rear end of said retracted telescopic guide pipe 3 sunk in the basement of the seabed according to a given inclination α.

• une semelle avant 5₁ posée sur le fond de la mer et supportant ladite extrémité avant 3₁ de la conduite de guidage télescopique rétractée et solidaire de celle-ci,
• au moins une semelle intermédiaire 5₂, 5₃ supportant ladite portion intermédiaire courbe 3₂ et/ou de la portion arrière 3₃ de ladite conduite de guidage télescopique rétractée et solidaire de celle-ci, dont la surface est plus petite que celle de ladite semelle avant 5₁, de préférence plusieurs dites semelles intermédiaires 5₂, 5₃ réparties le long desdites portion intermédiaire 3₂ et portion arrière 3₃ de ladite conduite de guidage télescopique rétractée 3 dont la surface est de plus en plus petite par rapport à ladite semelle avant au fur et à mesure qu'elles sont plus proches de ladite extrémité arrière 3₃ de la conduite de guidage, et
• une ancre 13 reliée 12 à ladite extrémité arrière 3₃ et apte à s'enfoncer dans le sol sous l'effet de ladite traction de ladite extrémité avant 3₁.

In a first preferred embodiment of the invention, said controlled driving means comprise:

• a front soleplate 5 ₁ placed on the bottom of the sea and supporting said front end 3 ₁ of the telescopic guide duct retracted and secured thereto,
• at least one midsole 5 ₂ , 5 ₃ supporting said curved intermediate portion 3 ₂ and / or the rear portion 3 ₃ of said telescopic guide pipe retracted and secured thereto, the surface of which is smaller than that of said front sole 5 ₁ , preferably several so-called intermediate soles 5 ₂ , 5 ₃ distributed along said intermediate portion 3 ₂ and rear portion 3 ₃ of said retracted telescopic guide pipe 3 whose surface is smaller and smaller with respect to said front flange as they are closer to said rear end 3 ₃ of the guide duct, and
• an anchor 13 connected to said rear end 3 ₃ and able to sink into the ground under the effect of said traction of said front end 3 ₁ .

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

The figure 7 illustrates this first version of the guide device according to the invention, wherein, the guide device is towed on site by means of a cable 10 connected to the front of the guide device via a head traction 11, the rear of said guiding device being connected by a second cable 12 to a very high performance anchor 13 of Stevpriss® or Stevmanta® type VryHOFF Company (Holland). The front part 3 ₁ of the guide device is secured to a sole 5 ₁ large surface 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 retracted telescopic guide pipe, their bearing surface decreasing as one approaches the rear 3 ₃ of said conduct guidance. The front 3 ₁ is further stabilized by a base comprising a load 6 integral with the sole 5 ₁ thus creating a recess of the guide device in said base 6, as shown in FIG. figure 8 .

By pulling on the tow rope 10, all causes the anchor begins to sink 25, resulting in 24 thereby the rear end 3 ₃ of the guide pipe. The circular shape of the guide pipe only moderately restrains the penetration, while the soles 5 ₂ , 5 ₃ distributed along the length oppose penetration with a force proportional to their surface. As the front soleplate 5 ₁ is of large dimensions, the front of the guiding device remains on the surface and the dead body 6 stabilizes the assembly so that the axis of the guiding device remains substantially horizontal, therefore parallel. at the bottom of the sea 4.

A method for producing one of such guide device consists in carrying out a traction of the front end 3 ₁ of said pipe retracted telescopic guide 3 until said intermediate sole 5 _2, 5 ₃ are found embedded in the ground deeper and deeper as they are closer to the rear end 3 ₃ of guide pipe to obtain the desired curvature R, preferably a radius of curvature greater than 500 m, preferably between 500 and 1000 m.

In another preferred embodiment of the invention, illustrated on the Figures 11, 12 and 13 , Said controlled burying means comprise at least one deflector 7 _{1 '7 2'} 7 ₃ secured to the outer telescopic pipe element of said telescopic guide pipe in said intermediate portion 3 3 ₂ or said rear portion 3 ₃ the telescopic outer guide pipe member comprising planar surfaces, preferably symmetrical with respect to the vertical axial plane XX ', YY' of said guide pipe in the longitudinal direction when it is in a straight horizontal position, and said planar surfaces of the baffles being inclined with respect to a horizontal axial plane XX ', ZZ' of said guide duct when the latter is in a horizontal position on the bottom of the sea, said deflector 7 ₁ , 7 ₂ , 7 ₃ being inclined an angle α ₁ , α ₂ , α ₃ so as to create a depression of said guide duct when the latter is pulled from said substantially horizontal initial position A1 to a said depressed position A2 in the seabed .

These deflectors 7 ₁ , 7 ₂ , 7 ₃ make it possible to control the curvature of the retracted telescopic guide pipe driven into the seabed because, once said deflectors are in a horizontal position, as shown in FIG. figure 12 they prevent further driving of the pipe and stabilize it in the desired position A2. It is understood that it is the spacing and the inclination of the baffles which determine the curvature and more generally the shape of the retracted telescopic guide pipe in the depressed position A2.

Preferably, the guiding device comprises a plurality of deflectors 7 _{1 '} , 7 _2' , 7 ₃ distributed along the outer pipe element of said telescopic guide pipe, inclined at angles α ₁ , α ₂ , α ₃ , decreasing as said deflector 7 ₁ -7 ₃ is closer to said front end 3 ₁ .

The guide duct is therefore equipped with several deflectors 7 ₁ -7 ₃ secured to the guide duct and oriented α ₁ -α ₃ with respect to the axis XX 'of the latter. The deflector 7 ₁ -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 pipe of guiding device as shown in the illustration figure 12 . This angle is adjusted beforehand during the manufacture of the guiding device, so as to act as the anchor 13 described in the Figures 7, 8 that is to say to create a depression of the retracted telescopic guide pipe, this depression being limited because of the angle α. Indeed, during the traction T exerted on the towing cable 10, the deflectors 7 ₁ -7 ₃ sink, driving 24 locally the guide pipe, until the deflector is substantially parallel to the force of the tow. traction on the cable 10, that is to say substantially parallel to the seabed 4, or substantially horizontal position in which it will then no longer exert vertical force downwards, tending to bring down the whole.

Advantageously, a plurality of deflectors 7 ₁ -7 ₃ , identical or different, will be advantageously disposed along the guide device, each of them having an angle α ₁ - α ₃ decreasing as one moves closer to the front end 3 ₁ , as illustrated on the figure 11 . During the penetration into the ground, when the set of deflectors 7 ₁ -7 ₃ have reached a substantially horizontal position, the desired curvature is obtained, as shown in FIG. figure 12 .

A method of making a guide device according to this second embodiment is to achieve the end T of front wheel 3 ₁ of said retracted telescopic guide pipe 3 until said deflectors 7 _1, 7 _2, 7 ₃ are buried in the ground in a horizontal position to obtain a said curvature sought preferably at a radius of curvature greater than 500 m, preferably between 500 and 1000 m.

• des conduites secondaires 8 de lançage de fluide 18 solidaires de l'élément de conduite télescopique externe de ladite conduite de guidage 3, s'étendant parallèlement à celle-ci et en sous-face de celle-ci, et
• lesdites conduites secondaires 8 présentant un diamètre réduit par rapport à celui desdits éléments de ladite conduite de guidage télescopique 3 et comprenant des perforations 9 en sous-face permettant d'expulser un fluide 18 en direction du fond de la mer lorsque lesdites conduites secondaires 8 sont alimentées par un dit fluide 18 sous pression.

The Figures 14 and 15 illustrate another preferred version of the invention wherein said controlled driving means comprises:

• fluid jetting secondary conduits 8 integral with the outer telescopic pipe element of said guide duct 3, extending parallel thereto and on the underside thereof, and
• said secondary pipes 8 having a reduced diameter relative to that of said elements of said telescopic guide pipe 3 and comprising perforations 9 on the underside for expelling a fluid 18 towards the seabed when said secondary pipes 8 are fed by a said fluid 18 under pressure.

Preferably, said secondary lines 8 are connected by their ends 8 ₁ , 8 ₂ to the front and rear ends 3 ₁ , 3 _{3 of} said outer pipe member of said telescopic guide pipe and communicate with said front ends 3 ₁ and rear 3 ₃ so that he is possible to feed them by the same supply pipe 19 from said front end 3 ₁ of said telescopic guide pipe 3.

On the figure 15 two secondary lines 8 are shown arranged symmetrically with respect to the guide duct 3.

On the figure 14 , the secondary pipe 8 is connected at their two ends to the guide pipe 3 by non-return valves 8 ₁ , 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, the surface vessel 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 ₁ , 8 ₂ , then through the orifices 9 of the 8. As soon as the assembly is deposited on the bottom 4, is injected, by the same pipes 8, advantageously water under high pressure, which will have the effect of weighing the assembly by filling the pipe guide 3, then to perform a de-cohesion of the ground in the underside, which facilitates the depression of the guide pipe.

• on injecte un gaz sous pression dans lesdites conduites secondaires 8 lorsque l'on veut remorquer la conduite de guidage télescopique rétractée 3 sur le fond de la mer et
• on injecte un liquide sous pression de préférence de l'eau dans lesdites conduites secondaires 8 et de préférence dans ladite conduite de guidage télescopique 3 obturée à ces extrémités 3₁, 3₂ et communicant avec lesdites extrémités 8₁, 8₂ desdites conduites secondaires 8 lorsqu'on veut enfoncer ladite conduite de guidage télescopique rétractée 3.

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

• a pressurized gas is injected into said secondary lines 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 with water into said secondary lines 8 and preferably into said telescopic guide duct 3 closed at these ends 3 ₁ , 3 ₂ and communicating with said ends 8 ₁ , 8 _{2 of} said secondary lines 8 when it is desired to depress said retracted telescopic guide pipe 3.

In another preferred version of the invention illustrated on the Figures 16 to 19 , it is advantageously added to any one of the devices according to the Figures 7 to 15 , a rigid outer upper structure 20, recessed on the front 3 ₁ of the telescopic outer pipe element of the guide pipe 3, the assembly resting on the ground via lateral flanges 21, as shown in FIG. figure 19 , detailing the section according to the plan DD.

• une structure supérieure externe rigide 20 recouvrant et maintenant rectiligne ladite conduite de guidage télescopique rétractée 3 lorsque celle-ci est sensiblement horizontale et repose sur le fond de la mer,
• ladite structure externe 20 présentant une ouverture centrale longitudinale en sous-face permettant à ladite conduite de guidage télescopique rétractée 3 de s'enfoncer dans le sol lorsque celle-ci est tractée T, et
• au moins un lien 17₁, 17₂, 17₃ reliant au moins la partie arrière 3₃ de l'élément de conduite télescopique externe de ladite conduite de guidage télescopique rétractée à ladite structure externe 20 de manière à empêcher un enfoncement de celle-ci au delà d'une profondeur donnée de manière à limiter la courbure R de ladite portion courbe, et
• ladite structure supérieure externe 20 reposant sur le sol au fond de la mer 4 de préférence par l'intermédiaire de semelles latérales 21 situées de part et d'autre de ladite ouverture centrale longitudinale 22, lesdites semelles latérales 21 empêchant l'enfoncement de ladite structure externe rigide 20, et
• ladite structure externe 20 étant solidaire de ladite embase 6 dans laquelle ladite portion avant 3₁ de l'élément de conduite télescopique externe de ladite conduite de guidage télescopique rétractée 3 est encastrée.

More specifically, the guiding device comprises:

• a rigid outer upper structure 20 covering and now rectilinear said retracted telescopic guide pipe 3 when it is substantially horizontal and rests on the bottom of the sea,
• said outer structure 20 having a longitudinal central aperture 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 ₁ , 17 ₂ , 17 ₃ connecting at least the rear part 3 ₃ of the outer telescopic pipe element of said retracted telescopic guide pipe to said external structure 20 so as to prevent a depression thereof beyond a given depth so as to limit the curvature R of said curved portion, and
• said outer upper structure 20 resting on the ground at the bottom of the sea 4, preferably by means of lateral flanges 21 situated on either side of said longitudinal central opening 22, said lateral flanges 21 preventing the embedding of said structure external rigid 20, and
• said outer structure 20 being integral with said base 6 wherein said front portion 3 ₁ of the outer telescopic pipe element of said pipe retracted telescopic guide 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 shown in FIG. figure 18 detailing the section according to the plane CC, structure elements 23 limiting the lateral displacements.

• une pluralité de liens souples 17₁, 17₂, 17₃ répartis le long de l'élément de conduite télescopique externe de la conduite de guidage télescopique 3 et présentant une longueur croissante au fur et à mesure qu'ils sont plus proches de l'extrémité arrière 3₃ de la conduite de guidage 3 et dont la longueur est telle que ladite conduite de guidage présente une dite portion courbe à la courbure R voulue et une dite portion arrière 3₃ linéaire.

Preferably, the guiding device comprises:

• a plurality of flexible links 17 ₁ , 17 ₂ , 17 ₃ distributed along the outer 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 to the desired curvature R and a said rear portion 3 ₃ linear.

These flexible links 17 ₁ , 17 ₂ , 17 ₃ are, for example, cables or chains connected on the one hand to the outer structure 20 in 26 and to the guide duct in 27. Said attachment points 26-27 are represented on the figure 17 . These flexible links 17 ₁ -17 ₃ are spaced along the guide pipe, uniform or not, and have a variable length, decreasing when it approaches the front 3 ₁ of the telescopic pipe element external guide pipe. Their position and their length are determined, so that at the end of penetration in the ground, when they are all in tension, the sought-after curve is obtained as illustrated on the figure 17 . To avoid the insertion into the ground of the structure 20, a multitude of lateral flanges 21 is installed on the underside, so as to create a sufficient base.

A method for producing one of such guide device essentially consists in carrying one end of T FWD 3 ₁ of the outer pipe element of said telescopic guide pipe 3 of said external rigid structure 20 integral with said guide duct until the one or more links 17 ₁ -17 ₃ prevent additional depression of at least said rear portion 3 ₃ of said retracted telescopic guide duct to obtain the desired curvature R preferably a higher radius of curvature at 500 m, more preferably between 500 and 1000 m.

All these controlled driving means 5 ₁ -5 ₃ , 7 ₁ -7 ₃ , 13, 20, 17 ₁ -17 ₃ according to the invention described in the various embodiments above can be implemented, either individually , either in combination, the nature of the soil requiring in the case of strong cohesion extremely powerful means.

The outer structure 20 is preferably continuous along the guide pipe and represents an additional mass of 25 to 75 tons. Jetting is carried out with pressurized water from the surface at pressures of 20 to 100 bar in secondary lines 8.

In the case of the telescopic guiding 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 150m each.

For example, in the case of the guide device for vertical drilling as explained on the figure 20 the telescopic pipe elements are five in number, 30 ", 24", 21 "1/2, 18", 3/4 and 16 "in diameter, each of the telescopic pipe elements measuring approximately 200m, which represents a The total length of the casings according to the prior art would have a same internal diameter of 16 "and the respective decreasing diameters would then be 36", 30 ", 24", 20 "and 16". also about 1000m, but since each casing element extends downwards from the sea floor level, the whole represents a cumulative length of about 3000m of pipe, which then represents a weight of steel approximately 2 to 2.5 times greater than the weight of steel required to make the telescopic casing according to the invention.

Claims (24)

1. A guide device (3) for an off-shore drilling installation comprising at least one drilling riser (2) extending from a floating support (1) to said guide device (3) on the sea bottom (4), said drilling being performable from said floating support using a drill string (38) fitted at its end with drilling tools (36) passing through said drilling riser (2) and said guide device (3), said guide device (3) being characterised in that it comprises a telescopic guide pipe (3) comprising coaxial telescopic guide elements (3a, 3b, 3c) about an axis (XX') and of decreasing diameters, the elements being preassembled one in another in such a manner that said telescopic pipe elements are suitable for sliding in the direction of said axis (XX') one inside another, the smallest diameter, innermost telescopic pipe element (3c) being fitted at its end with breakup means (35) for breaking up the ground suitable for enabling said telescopic guide pipe (3) to be progressively buried in the ground by sliding said telescopic pipe elements (3a, 3b, 3c) outwards, thereby enabling a drilling tool (36) at the end of said drill string (38) to be guided more deeply in the ground.
2. A guide device according to claim 1, characterised in that said smallest-diameter innermost pipe element (3c) presents a diameter substantially equal to the diameter of said drilling riser (2).
3. A guide device according to claim 1 or claim 2, characterised in that said means (35) for breaking up the ground are constituted by a multiply-perforated capsule enabling water or mud to be jetted into the ground by being injected under very high pressure.
4. A guide device according to one of claims 1 to 3, characterised in that it has at least three coaxial telescopic pipe elements (3a, 3b, 3c).
5. A device according to one of claims 1 to 4, characterised in that each of said telescopic coaxial pipe elements (3a, 3b, 3c) presents a length of 50 m to 300 m, preferably of 100 m to 200 m, said deployed guide pipe presenting a length of 150 m to 600 m, and preferably of 200 m to 300 m.
6. A guide device (3) according to one of claims 1 to 5, characterised in that it comprises a said telescopic guide pipe (3) suitable for use in an off-shore drilling installation, in which at least one drilling riser (2) extends from a floating support (1) to a said guide device (3) at the sea bottom (4), said drilling riser (2) deflecting progressively from a substantially vertical position (2a) at said floating support (1) to a position that is substantially horizontal or tangential to the horizontal (2b) at the sea bottom (4), said drilling being performable from said floating support via said drilling riser (2) and said guide device (3) in such a manner that the borehole in the sea bottom is begun at a given angle of inclination (α) relative to the horizontal that preferably lies in the range 5° to 60°, and more preferably in the range 25° to 45°, said guide device (3) being characterised in that it comprises a said telescopic guide pipe (3) in a buried position (A2) in which said telescopic guide pipe (3) in the retraced position or the outer telescopic pipe element (3a) when said telescopic pipe (3) is deployed, comprises in succession:

   . a front end (3₁) resting substantially horizontally on the sea bottom;

   . a curved intermediate portion (3₂) buried in the subsoil of the sea bottom with a large radius of curvature (R), preferably a radius of curvature greater than 500 m; and

   . a rear portion (3₃) that is substantially linear and buried in the subsoil of the sea bed at said given angle of inclination (α);

   said telescopic guide pipe (3) or said outer telescopic element (3a) co-operating with controlled burying means (3₄, 5₁-5₃, 7₁-7₃, 8-9, 13) enabling said retracted telescopic guide pipe (3) to be buried in the sea bottom while said retracted telescopic guide pipe (3) is being towed (T) along the sea bottom from its front end (3₁), starting from an initial position (A1) in which said retracted telescopic guide pipe (3) rests entirely on the sea bottom in a substantially horizontal position, to a said buried position (A2) in the subsoil of the sea bottom.
7. A guide device according to claim 6, characterised in that said retracted telescopic guide pipe (3) presents a length of 100 m to 600 m, preferably of 250 m to 450 m, with a said given angle of inclination (α) of the guide pipe lying in the range about 10° to 60°, and preferably in the range 25° to 45°.
8. A guide device according to claim 6 or claim 7, characterised in that said front end (3₁) is engaged in a baseplate (6) including a load and resting on a front soleplate (5₁) such that said baseplate (6) maintains said front end (3₁) substantially horizontally on the sea bottom while it is being towed (T).
9. A guide device according to one of claims 6 to 8, characterised in that said controlled burying means comprise:

   - a front soleplate (5₁) placed on the sea bottom and supporting said front end (3₁) and secured thereto;

   - at least one intermediate soleplate (5₂, 5₃) supporting said curved intermediate portion (3₂) and/or the rear portion (3₃) and secured thereto, of surface area that is smaller than that of said front soleplate (5₁), preferably a plurality of said intermediate soleplates (5₂, 5₃) distributed along said intermediate portion (3₂) and said rear portion (3₃) of surface area that becomes smaller relative to said front soleplate on approaching said rear end (3₃); and

   - an anchor (13) connected (12) to said rear portion (3₃) and suitable for becoming buried in the ground under the effect of said traction applied to said front end (3₁).
10. A guide device according to one of claims 6 to 9, characterised in that said controlled burying means comprise at least one deflector (7₁, 7₂, 7₃) secured to said outer telescopic pipe element (3a) of said telescopic guide pipe (3) in said intermediate portion (3₂) or said rear portion (3₃) of said retracted telescopic guide pipe, comprising plane surfaces that are preferably symmetrical about a vertical axial plane (XX', YY') of said guide pipe in the longitudinal direction when it is in a rectilinear horizontal position, and said plane and deflector surfaces being inclined relative to a horizontal axial plane (XX', ZZ') of said guide pipe when it is in a horizontal position on the sea bottom, said deflector (7₁, 7₂, 7₃) being inclined at an angle (α₁, α₂, α₃) in such a manner as to cause said retracted telescopic guide pipe (3) to become buried when it is towed from said substantially horizontal initial position (A1) to a said buried position (A2) in the sea bottom.
11. A guide device according to claim 10, characterised in that it has a plurality of deflectors (7₁, 7₂, 7₃) distributed along the outer telescopic pipe element (3a) of said telescopic guide pipe, said deflectors being inclined at respective angles (α₁, α₂, α₃) that become smaller for said deflectors (7₁, 7₂, 7₃) that are closer to said front end (3₁).
12. A guide device according to one of claims 1 to 11, characterised in that said controlled burying means comprise:

    - secondary pipes (8) for jetting fluid (18) and secured to said telescopic guide pipe (3), extending parallel thereto along the underface thereof; and

    - said secondary pipes (8) being of smaller diameter than said telescopic guide pipe (3) and having perforations (9) in their underfaces enabling a fluid (18) to be expelled towards the sea bottom when said secondary pipes (8) are fed by a said fluid (18) under pressure.
13. A guide device according to claim 12, characterised in that said secondary pipes (8) are connected via their ends (8₁, 8₂) to the front and rear ends (3₁, 3₃) of said retracted telescopic guide pipe (3), communicating with said front and rear ends (3₁, 3₃) in such a manner as to make it possible to feed them using a single feed pipe (19) connected to said front end (3₁) of said guide pipe (3).
14. A device according to one of claims 1 to 13, characterised in that the guide device comprises:

    - a rigid outer top structure (20) covering and holding rectilinear said retracted telescopic guide pipe (3) when it is substantially horizontal and rests on the sea bottom;

    - said outer structure (20) presenting a longitudinal central opening in its bottom face enabling said retracted telescopic guide pipe (3) to become buried in the ground when it is towed (T);

    - at least one connection (17₁, 17₂, 17₃) connecting at least the rear portion (3₃) of the outer telescopic pipe element (3a) of the telescopic guide pipe (3) to said outer structure (20) in such a manner as to prevent it from becoming buried beyond a given depth so as to limit the radius of curvature (R) of said curved portion;

    - said outer top structure (20) resting on the ground of the sea bottom (4), preferably via lateral soleplates (21) situated on either side of said longitudinal central opening (22), said lateral soleplates (21) preventing said rigid outer structure (20) from becoming buried; and

    - said outer structure (20) being secured to said baseplate (6) in which said front portion (3₁) of the guide pipe (3) is engaged.
15. A guide device according to claim 14, characterised in that it has a plurality of flexible connections (17₁, 17₂, 17₃) distributed along the outer telescopic pipe element (3a) of said telescopic guide pipe (3) and presenting lengths that become longer for connections that are closer to the rear end (3₃) of the guide pipe (3) and of lengths that are such that said guide pipe presents a said curved portion having a desired radius of curvature (R) and a said rear portion (3₃) that is linear.
16. A method of making a guide device according to claims 6 to 15, characterised in that the following steps are performed:

    - placing a said telescopic guide pipe in the retracted position (3) in a said initial position (A1) where it rests substantially horizontally and in rectilinear manner on the sea bottom, said telescopic guide pipe (3) co-operating with said controlled burying means (3₄, 5₁-5₃, 7₁-7₃, 8-9, 13); and

    - towing (T) the front end (3₁) of said telescopic guide pipe (3) in the retracted position along the sea bottom, preferably in the axial longitudinal direction XX' of said guide pipe, from said initial position (A1) to a said buried position (A2).
17. A method of making a guide device according to claim 16, characterised in that guide devices according to claim 8 or claim 9 are used and the front end (3₁) of said retracted telescopic guide pipe (3) is towed (T) until said intermediate soleplates (5₂, 5₃) are buried in the ground at increasing depth on coming closer to the rear end (3₃) of the guide pipe so as to obtain the desired radius of curvature (R), preferably greater than 500 m, and more preferably lying in the range 500 m to 1000 m.
18. A method of making a guide device according to claim 16 or claim 17, characterised in that a guide device according to claim 10 or claim 11 is used and the front end (3₁) of said retracted telescopic guide pipe (3) is towed (T) until said deflectors (7₁, 7₂, 7₃) are buried in the ground in a horizontal position so as to obtain a said desired radius of curvature preferably greater than 500 m, and more preferably lying in the range 500 m to 1000 m.
19. A method of making a guide device according to one of claims 16 to 18, characterised in that a guide device is used according to claim 12 or claim 13, and:

    - injecting gas under pressure into said secondary pipes (8) when it is desired to tow said guide pipe (3) on the sea bottom; and

    - injecting a liquid under pressure, preferably water, into said secondary pipes (8) and preferably into said telescopic guide pipes (3) closed at both ends (3₁, 3₂) and communicating with said ends (8₁, 8₂) of said secondary pipes (8) when it is desired to bury said guide pipe (3).
20. A method of making a guide device according to one of claims 16 to 19, characterised in that a guide device is used according to claim 14 or claim 15, and the front end (3₁) of said retracted telescopic guide pipe (3) and said rigid outer structure (20) secured to said guide pipe are towed (T) until said connection(s) (17₁-17₃) prevent at least said rear portion (3₃) of said retracted telescopic guide pipe (3) from becoming buried deeper so as to obtain the desired radius of curvature (R) preferably greater than 500 m, and more preferably lying in the range 500 m to 1000 m.
21. An off-shore 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. An off-shore 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) deflecting progressively from a substantially vertical position (2a) at said floating support (1) to a position that is substantially horizontal or tangential to the horizontal (2b) at the sea bottom, drilling being performable from said floating support (1) via said drilling riser (2) and said guide device (3) in such a manner that a borehole begins in the sea bottom at a given angle of inclination (α) relative to the horizontal, preferably lying in the range 10° to 80°.
23. A method of making a drilling installation according to claim 21 or claim 22, characterised in that the following steps are performed:

    - making a guide device according to a method according to one of claims 16 to 20; and

    - connecting at least one said drilling riser (2) to said front end (3₁) of the guide pipe resting on the sea bottom (4).
24. A method of drilling using a drilling installation according to claim 21 or claim 22, characterised in that drilling operations are performed and a borehole is constructed by deploying drill strings co-operating with drilling tools and columns of tubing via a said drilling riser (2) and a said guide device (3) buried in the sea bottom (4).

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