EP0242307B1 - Device for the under water drilling of foundations - Google Patents

Description

The present invention relates to a device for the submerged drilling of foundations, and more particularly to such a device of the type comprising at least one cutter and a pump for discharging cuttings, and hydraulic motors for driving said cutter and said pump.

The exploitation of hydrocarbon deposits at great depths calls more and more on production platforms which require the use of anchor points of very high capacity. This is the case, for example, of so-called “stretched cable” platforms.

Such anchoring points, capable for example of taking up vertical or horizontal forces of the order of 1000 or 2000 tonnes, require the realization in the ground, under several hundred meters of water, of piles of several square meters of section and several tens of meters in height, and therefore require corresponding holes to be drilled.

Rotary drilling being excluded to make such anchor points, other solutions have already been proposed.

Thus, French patent application No. 8,514,939 (FR-A-2,588,297) describes a device comprising:

• - a drilling apparatus having a head connected by a hydraulic advance cylinder to a body provided with cutters, this apparatus being furthermore provided with a pump for discharging cuttings and with hydraulic motors for driving the cutters and the pump;
• - a rigid tubular assembly comprising a pipe for the delivery of cuttings and pipes for supplying the actuator and the motors with hydraulic fluid;
• - connecting means between the head of the drilling rig and the lower end of the tubular assembly;
• - support means arranged on the seabed at the head of the borehole, arranged to support means for blocking the tubular assembly; and
• - means for suspending the device from a ship; means being provided for the supply of hydraulic fluid, and connecting conduits being provided between these means for supplying fluid and the end of the tubular assembly.

This device is however limited, at a very great depth, by the weight and the cost of the tubular assembly, and by the power required to ensure the circulation of the hydraulic fluid.

The present invention aims to provide a drilling device better suited to very great depths.

To this end, the subject of the invention is a device for the submerged drilling of foundations, comprising at least one cutter and a cuttings delivery pump, and hydraulic motors for driving said cutter and said pump, characterized in that it comprises a hydraulic turbine capable of operating with the aid of a fluid such as sea water, and a hydraulic power unit driven by said turbine and arranged to supply said hydraulic motors.

Contrary to what was the case previously, the device according to the invention consequently comprises its own power installation constituted by the hydraulic power station. Primary energy is very simply supplied from the service vessel in the form, for example, of pressurized seawater, which can be obtained in particular by means of drilling mud pumps with which all vessels are fitted. drilling.

Furthermore, the power required is considerably reduced since there is no longer any circulation of hydraulic fluid between the device and the surface, but only the injection at the inlet of the turbine of fluid such as sea water. under pressure, which is then evacuated to the bottom of the borehole.

It will also be noted that the device according to the invention does not require any electrical transfer of power between the surface and the bottom and consequently avoids the use of a high capacity cable which poses problems difficult to solve due to the depth. of proposed operation.

In a preferred embodiment, the device according to the invention comprises two cutters with horizontal axes rotating in opposite directions.

In order to make the speed regulation of the turbine as simple as possible, it is possible to provide a relief valve opening under the effect of an increase in pressure at the inlet of the turbine caused by an overspeed.

Preferably, the turbine exhaust is directed to the tools of the cutter to ensure cleaning.

The hydraulic power unit can comprise a plurality of hydraulic pumps, for example one per motor, driven by said turbine via a mechanical distribution box.

In a particular embodiment, the device according to the invention may comprise a head forming a first distribution box for the supply of said turbine and the delivery of the cuttings.

This head can be connected to the body of the device by at least one advance cylinder supplied by said hydraulic unit.

The head can also be connected by a two-way pipe to a second connected distribution box, on the one hand to means for supplying the supply fluid to the turbine, and on the other hand to a discharge hose. spoils.

• - la figure 1 est une vue d'ensemble du dispositif selon l'invention ainsi que d'un navire à partir duquel il est mis en oeuvre, et
• - la figure 2 est une vue en élévation de l'ensemble turbine/centrale hydraulique du dispositif.

A particular embodiment of the invention will now be described by way of nonlimiting example with reference to the appended schematic drawings in which:

• FIG. 1 is an overall view of the device according to the invention as well as of a ship from which it is used, and
• - Figure 2 is an elevational view of the turbine / hydraulic unit of the device.

FIG. 1 generally shows the drilling rig 1, connected by a drill string 2, of the drill string type, to a service vessel 3 which may for example be a dynamically positioned vessel.

The drill string 2 is suspended from the ship by its upper part using an operating winch 4. The ship 3 also carries a pump 5 of the slurry pump type, connected by means of a hose

6 to an injection head 7 for the pressurized fluid, for example sea water, in the drill string 2.

A winch 8 allows the unwinding of an electric cable 9 of low power, making it possible to supply the electrical members, such as the measuring instruments, of the apparatus 1, and another winch 10 allows the unwinding of another cable. electric 11, also of low power, allowing the supply of electric jacks to the guiding and blocking device 12 which will be described below.

The rod train 2 ends at its lower part by a distribution box 13 connected by a two-way pipe 14 to another distribution box 15.

The two-way pipe 14 is constituted for example by two concentric tubes.

The path of the pipe 14 coming, via the distribution box 13, from the drill string 2, is directed towards a hydraulic turbine 16, via the distribution box 15 and a flexible conduit 17 .

The other channel of the pipe 14 is connected at its upper part, via the distribution box 13, to a hose 18 for removing the cuttings and at its lower part, via the distribution box. 15, to a telescopic conduit 19 for discharging the cuttings.

The pipe 14 has a length such that the distribution box 13 is located above the guide and blocking means 12 when the device 1 is at the bottom of the borehole.

The turbine 16 is provided with a valve 20 controlled by the inlet pressure of the turbine, that is to say the pressure in the duct 17, for regulating the speed of the turbine according to the power demanded.

The exhaust 21 of the turbine is directed by a conduit, not shown, to the cutters which will be described below in order to clean the drilling peaks.

The rotor of the turbine 16 is connected, by means of a coupling 22, to a mechanical distribution box 23 also serving as a reduction gear, and provided with several outlets capable of driving a set of hydraulic pumps 24.

The primary shaft of the distribution box 23 also carries a speed control device 25.

The distribution box 23, the pumps 24 and the speed control device 25 are placed in an oil pan 26.

The drilling device 1 also comprises two cutters 27 with a horizontal axis and rotating in opposite directions, so as to bring the cuttings back to a suction nozzle 28 connected to a pump 29 for discharging the cuttings. The output of the pump 29 is connected to the discharge conduit 19.

The cutters 27 and the pump 29 are each driven by one of the hydraulic motors supplied by hydraulic pumps 24.

Furthermore, the distribution box 15 is connected to the body of the device 1 by a hydraulic advance cylinder 30, also supplied by one of the pumps 24.

• - L'énergie primaire constituée dans le cas présent par de l'eau de mer sous pression est obtenue à partir de la pompe 5. Cette eau de mer sous pression est transmise au dispositif 1 par l'intermédiaire du flexible 5, de la tête d'injection 7, du train de tiges 2, de la boîte de distribution 13, et d'une des voies de la conduite 14.
• - Cette eau de mer sous pression alimente ensuite la turbine 16 par l'intermédiaire de la boîte de distribution 15 et de la conduite 17, puis est évacuée, de préférence sur les pics des fraises 27.
• - L'énergie mécanique engendrée par la turbine 16 est transmise par l'intermédiaire de l'accouplement 22 à la centrale hydraulique constitué par la boîte de répartition 23 et les pompes 24.
• - Ces pompes 24 alimentent à leur tour en énergie les moteurs hydrauliques des fraises 27 et de la pompe 29.

The energy supply of the device according to the invention can therefore be summarized as follows:

• - The primary energy constituted in this case by pressurized sea water is obtained from the pump 5. This pressurized sea water is transmitted to the device 1 via the hose 5, from the head injection 7, of the drill string 2, of the distribution box 13, and of one of the lines of the pipe 14.
• This pressurized seawater then feeds the turbine 16 via the distribution box 15 and the pipe 17, then is discharged, preferably on the peaks of the strawberries 27.
• - The mechanical energy generated by the turbine 16 is transmitted via the coupling 22 to the hydraulic unit constituted by the distribution box 23 and the pumps 24.
• - These pumps 24 in turn supply energy to the hydraulic motors of the cutters 27 and of the pump 29.

The guide and blocking assembly 12 is composed of a lower structure 31 and an upper structure 32, blocking jaws 33 for the pipe 14 being mounted on the upper structure 32, from which they can be actuated at by means of electric jacks 34 supplied by the cable 11.

The lower structure 31 forms two sets of guide surfaces 35 and 36 respectively. The guide surfaces 35 form a re-entry cone making it possible to guide the drilling device 1 in a borehole already partially carried out when, for whatever reason, it has had to be withdrawn therefrom. The guide surfaces 36 cooperate with other guide surfaces 37 provided on the upper structure 32 to ensure, during such reentry, correct repositioning between the lower structures 31 and upper 32.

The drilling is carried out by an alternative operation of the jack 30 and the jaws 33, as described in French patent application 8 514 939.

Claims (6)

1. A device for the immersed drilling of foundations, including at least one cutter (27) and a discharge pump (29) for the spoil, and hydraulic motors for driving said cutter and said pump, which device includes moreover a hydraulic turbine (16) adapted for operating with the assistance of a fluid such as sea water, a hydraulic power plant (23, 24) driven by said turbine and arranged in such manner as to feed said hydraulic motors, and a head forming a first distribution box (15) for feeding the turbine and discharging the spoil, said head being connected by a twin-channel duct (14) to a second distribution box (13), connected on the one hand to means (2) for providing the feeding fluid to the turbine, and on the other hand to a flexible duct (18) for the spoil discharge.

2. A device according to claim 1, characterised by the fact that it includes two cutters of horizontal axes, rotating in reverse directions.

3. A device according to any one of claims 1 and 2, characterised by the fact that the hydraulic turbine is provided with a discharge valve (20).

4. A device according to any one of claims 1 to 3, characterised by the fact that the exhaust (21) of the turbine is directed towards the cutter tools.

5. A device according to any one of claims 1 to 4, characterised by the fact that said hydraulic power plant includes a plurality of hydraulic pumps (24) driven by said turbine via a mechanical distribution box (23).

6. A device according to any one of claims 1 to 5, characterised by the fact that said head is connected to the device body by at least one advance jack (30) fed by said hydraulic power plant.

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