WO2009157762A1

WO2009157762A1 - Device for rotary drilling with a tube into a bottom located under water

Info

Publication number: WO2009157762A1
Application number: PCT/NL2009/000136
Authority: WO
Inventors: Egbert Gerrit Bouwmeester
Original assignee: Conrad Trading B.V.
Priority date: 2008-06-26
Filing date: 2009-06-22
Publication date: 2009-12-30
Also published as: NL1035635C2

Abstract

Device (1) for rotary drilling with a tube (2) in a. bottom (3) located under water, characterized in that the device (1) comprises a frame (4) to be placed on the bottom (3), which frame (4) is provided with rotatable first engaging means (5) for clampingly engaging and rotating the tube (2) for the purpose of rotary drilling with the tube (2) into the bottom (3).

Description

DEVICE FOR ROTARY DRILLING WITH A TUBE INTO A BOTTOM LOCATED UNDER WATER

Description

Field of the invention

The invention relates to a device for rotary drilling with a tube into a bottom located under water. The invention further relates to a method for rotary drilling with a tube into a bottom located under water.

Background of the invention

In order to form a picture of locations suitable for extracting specific minerals, such as tin, the bottom must be analysed. It is important here to take samples of the bottom such that it is quite certain that they come from a determined depth and that these samples have not been contaminated with material from the borehole wall. Accurate maps of the bottom can be made using these samples. The so-called "counterflush" drilling system is a suitable drilling system for this purpose. The "counterflush" drilling system comprises two concentrically arranged tubes, the "outer tube" and the "inner tube", which are generally connected to each other, referred to hereinbelow for the sake of convenience as tube assembly. The bottom is loosened by rotation of the tube assembly. By injecting a medium between the "outer tube" and the "inner tube" and a carefully made passage in the vicinity of the outer end of the tube assembly, through which the medium moves upward again by means of the upward force, the dislodged material situated at the outer end of the tube system is moved upward. The tube assembly can then drill deeper into the bottom again by means of rotation. The downward force of the tube assembly for drilling deeper into the bottom comes from the weight of the tube assembly. However, because the tube assembly undergoes a certain friction from the borehole wall, the effect of the weight of the tube assembly decreases as the drilling goes deeper. This reduces the maximum depth of drilling and likewise reduces the speed of drilling. Another drawback is that movement of the tube assembly at the interface of bottom and water can disturb the structure of the bottom, thereby diminishing the quality of the analysis. A device is known, see US6526818B1, which can be placed on the bottom in order to keep the borehole in the bottom as straight as possible. This known device does not however comprise first engaging means and serves only as guide for the tube assembly and for the purpose of maintaining a straight borehole. A device which can be placed on the bottom is also referred to as Seabed Frame (SBF), see for an example GB2436320A. In drilling systems based on a vibrating or striking movement an SBF is favourable as reaction mass for the force required to press a probe or sample tube into the bottom. Because the tube assembly used in a "counterflush system" is relatively heavy, partly because the tube assembly extends from the vessel to the bottom, and the drilling is rotary, an SBF is not used. The rotatable engaging means for clampingly engaging and rotating the tube assembly are situated above water in a vessel or drilling island, and can also be directly operated there. The advantage hereof is that no special modifications are necessary for the presence under water and for remote control. Because the tube assembly extends from the vehicle or the drilling island to the bottom and is relatively rigid and the engaging means are situated above the water, a correction must however be made for the movement of the water, such as swell of the sea. Means for compensating this movement are not sufficiently suitable in practice. This limits the possibilities, such as the maximum water depth and the maximum drilling depth. There is therefore a need for a device for rotary drilling with a tube, in particular a "counterflush tube assembly", in a bottom located under water, which does not have the above stated drawbacks and which has modifications for driving and operating the rotatable engaging means under water. The object of the present invention is to provide such a device. Summary of the invention

The invention provides for this purpose a device for rotary drilling with a tube in a bottom located under water, wherein the device comprises a frame to be placed on the bottom, which frame is provided with rotatable first engaging means for clampingly engaging and rotating the tube for the purpose of rotary drilling with the tube into the bottom. Rotatable is understood to mean rotatable such that in operative mode the rotation axis coincides with the longitudinal axis of the tube. The advantage of such a device is that in operative mode the rotatable first engaging means, instead of being above water, as on a vessel in known systems, are present in the vicinity of the bottom, whereby the tube can move relatively freely in substantially vertical direction relative to the vessel or the drilling island above water, so that correction can be made more easily for the movement of the water, for instance the swell of the sea. The maximum distance of the vessel or the drilling island to the bottom can hereby be increased. This device moreover reduces the distance between the part of the tube subject to the rotation force of the first engaging means and the part of the tube where it undergoes friction from the bottom. The forces on the tube are hereby limited as far as possible to the rotation forces for loosening the bottom, whereby the chance of the tube brealdng is reduced, so that it is possible to drill in deeper waters, for instance at least 40 metres. The first engaging means can preferably take up a clampingly engaging and a non-clampingly engaging position so that the guiding of the tube can also take place in the vicinity of the bottom. The first engaging means can cause the tube to rotate in clampingly engaging position and lower the tube in non-clampingly engaging position, and then cause the tube to rotate again in clampingly engaging position. The weight of the frame could thus contribute to the downward force of the tube. The tube is preferably the tube assembly, a double-walled tube, of a "counterflush" drilling system or the "outer tube" of a so-called "counterflush" system in the case the "outer tube" and the "inner tube" are not connected to each other. The device is particularly suitable for combining with a vessel. The vessel, which preferably comprises a space for receiving the device, can first sail to the desired location and the frame can then be lowered to the bottom situated at this location. The frame is preferably connected to the vessel using winches such that the tensile force of the cables is held substantially constant not only during lowering of the frame to the bottom and during lifting of the frame, but also during the rotary drilling with the tube. The vessel preferably comprises provisions for lengthening the tube using tube parts suitable for this purpose, receiving means for receiving the fractions of bottom material and analysis means for analysing the fractions of bottom material. If the tube is a "counterflush" tube assembly, it is quite certain that the obtained samples come from the bottom of the borehole. It is then less likely that material from the borehole wall has been disturbed.

The frame is preferably also provided with rotating means for rotating the first engaging means. The forces can thus be transmitted optimally, for instance by means of a coupling body. The rotating means can for instance realize 20 to 40 rotations per minute.

In order to make an appreciable contribution to the downward force of the tube, the frame preferably has a weight such that the gravitational force acting on the frame is at least in the same order of magnitude as the friction force which the tube usually undergoes in the bottom in operative mode. "Friction force" is understood to mean the friction encountered by the tube from the borehole wall. This friction force prevents the tube from rotating and making a downward movement. "Friction force" is not understood to mean the force required to loosen the bottom material. "Usually" is understood to mean that friction force which a determined drilling system encounters in an average bottom with an average drilling depth. This friction force depends on the drilling system, on the bottom and on the length of that part of the tube situated in the bottom. In a "counterflush" drilling system the friction force is much greater when compared to other drilling systems, because the material is brought upward via the inside of the tube assembly instead of via the outside. Depending on the bottom and the movement of the tube in the bottom, the borehole wall remains largely intact here. The weight of the frame is particularly important when drilling takes place in relatively less deep water, for instance several tens of metres deep. In such a situation the weight of that part of the tube situated above the bottom contributes less toward the downward force of the tube. When the tube is a usual "counterflush" tube system, and the tube is usually drilled about 100 metres into the bottom in water of about 40 metres deep, a weight of at least 5,000 kg, for instance about 6,000 kg, is highly suitable for the frame.

Another function of the frame is to support the components of the device. In order to prevent the frame itself sinking too deeply into the bottom, it can be provided with a base plate on which the frame supports on the bottom. The frame can likewise be provided with anchoring means to prevent the frame slipping away.

The frame is preferably provided with lifting means co-acting with the first engaging means for the purpose of lifting the first engaging means situated in a non-clampingly engaging position. The advantage of such a device is that the weight of the frame contributes toward the downward force of the tube on the bottom during rotation of the tube and during lowering of the tube into the bottom. The tube can hereby be drilled deeper and the drilling can proceed more rapidly. The lifting means do not serve to lift the first engaging means situated in a clampingly engaging position. Such lifting means are usual for the purpose of drilling the tube into the bottom with striking force. The lifting means preferably comprise two hydraulic cylinders, which hydraulic cylinders can exert a push and a pull force on the first engaging means. This means that the hydraulic cylinders can also contribute toward the downward force of the tube. The stroke of the hydraulic cylinders can be 1.5 metres, and the downward force can for instance be equal to a weight of 5,000 kg.

The frame is preferably also provided with stationary second engaging means for clampingly engaging the tube. Such second engaging means can clampingly engage and hold the tube in stationary position in situations where the tube can make undesirable movements, such as upward or downward. For instance in situations where the first engaging means are in a non-clampingly engaging position or when the rotating means or lifting means are not functioning. The tube can for instance sink into soft parts of the bottom.

In a preferred embodiment the device comprises a hydraulic system for driving the rotating means from above water. The hydraulic system preferably also drives the first engaging means and the second engaging means and the lifting means, if present. The hydraulic system for instance comprises three lines, two for supply and discharge of the fluid for the hydraulic system and a line for discharge of the leaked fluid. This device preferably comprises a control system for controlling the hydraulic system from above water, such as controlling the supply of hydraulic oil. The control system preferably comprises an electrical cable for communication with the hydraulic system from above water, such as a vessel or drilling island, which hydraulic system can then in turn drive a functionality of the device. The control system preferably likewise comprises a control valve unit, preferably in the vicinity of the frame, which control valve unit can regulate the fluid flow to different functionalities of the frame, if these are also driven by the hydraulic system. The control system preferably also comprises a control unit above water for controlling the control valve unit under water. In such a device all functionalities associated with the device can be operated above water, whereby no forces have to be transmitted from above the water to under the water. The hydraulic system and the control system preferably comprise correcting means for holding the cables required for these systems under constant tensile force.

Other than in known devices for rotary drilling, the mobility of the tube in its longitudinal direction relative to the vessel depends on the swell of the sea. The invention therefore preferably comprises compensating means, such as at least one winch, for compensating in operative mode the movement of tube-handling means, situated above water and particularly connected to a vessel, relative to the tube.

The invention likewise provides a method for rotary drilling with a tube into a bottom situated under water using a device for rotary drilling with a tube into a bottom situated under water, which device comprises a frame to be placed on the bottom, which frame is provided with rotatable first engaging means for clampingly engaging and rotating the tube for the purpose of rotary drilling with the tube into the bottom, wherein the method comprises of lowering the frame from above water to the bottom and extending the tube until it extends from the frame to a position above water. The purpose of extending the tube is to create a situation such that, by rotating the tube, the tube is drilled into the bottom and material from or data about the bottom are carried upward. In the case of a "counterflush" drilling system material from the borehole will be transported to the vessel. Each time the tube is drilled for instance three metres into the bottom, or the frame is lowered for instance three metres, the tube must be extended as a whole with a new tube part of three metres. Above water a hydraulically driven winch can couple a new, 3 metre-long tube part to the tube under constant tensile force. In the case of a "counterflush" system a rotatable element must then be placed on top thereof, this rotatable element being coupled to means for supply and discharge of liquid for "counterflush".

In a preferred method the frame is also provided with rotating means for rotating the first engaging means and with lifting means co-acting with the first engaging means for the purpose of lifting the first engaging means situated in a non-clampingly engaging position, wherein the lifting means comprise at least one, preferably two hydraulic cylinders, which hydraulic cylinders can exert a pushing and a pulling force on the first engaging means, and the device comprises a hydraulic system for driving the first engaging means, the rotating means and the hydraulic cylinder from above water, and the device comprises a control system for controlling the hydraulic system from above water, which method comprises of operating the control system such that the hydraulic cylinder exerts a substantially upward force on the first engaging means and the engaging means are situated in a non-clampingly engaging position, and subsequently operating the control system such that the hydraulic cylinder exerts a substantially downward force on the first engaging means, the first engaging means are situated in a clampingly engaging position and the rotating means rotate the first engaging means. In such a method the weight of the frame will make an optimal contribution toward the downward force of the tube. The device forms a substantially autonomous unit which can be operated above water by means of the control system. The water depth for the rotary drilling using such a method can be 40 metres with such a method, and drilling can take place to a depth of 100 metres.

In an even more preferred method the frame is also provided with second engaging means and the hydraulic system can also drive the second engaging means, and the method comprises of operating the control system such that the first engaging means are situated in non-clampingly engaging position, the lifting means lift the first engaging means and the second engaging means are situated in clampingly engaging position.

Brief description of the figure

The invention is elucidated hereinbelow on the basis of a non-limitative preferred embodiment of a device according to the invention. Herein, figure 1 shows a cross- section of the embodiment in operative mode, i.e. the frame is placed on the bottom and a tube is already some distance in the bottom.

Description of a preferred embodiment of the invention.

In the device (1) according to the invention shown in figure 1 for rotary drilling with a tube (2) into a bottom (3) located under water, frame (4) placed on bottom (3) is provided with rotatable first engaging means (5), situated substantially concentrically relative to tube (2), for clampingly engaging and rotating tube (2) for the purpose of rotary drilling with tube (2) into bottom (3). Frame (4) is also provided with rotating means (8) situated substantially concentrically relative to tube (2) for the purpose of rotating the first engaging means (5), wherein the rotating means are connected to the first engaging means (5) by means of a coupling body (14). The tube is a tube assembly of a "counterflush" drilling system, wherein the arrows in tube (2) indicate the flow of the medium. Frame (4) is moreover provided with lifting means (6) co-acting with the first engaging means (5) for lifting the first engaging means (5) situated in a non- clampingly engaging position, wherein the lifting means consist of two hydraulic cylinders (13) which can exert substantially upward force as well as substantially downward force on the first engaging means (5), and thus indirectly on tube (2). Hydraulic cylinders (13) are connected at their outer ends to a support construction (17), which support construction (17) can move along two rods (23) of the frame which run parallel to hydraulic cylinders (13). Shortening the telescopic hydraulic cylinders (13) moves support construction (17), with rotating means (8), coupling body (14) and the first engaging means (5) connected thereto, upward in operative mode. Frame (4) is likewise provided with stationary second engaging means (7) situated substantially concentrically relative to tube (2) for the purpose of clampingly engaging tube (2). This embodiment of device (1) according to the invention comprises a hydraulic system (9) for driving the first engaging means (5), rotating means (8), lifting means (6) (the two hydraulic cylinders (13)) and the second engaging means (7) from above water. This hydraulic system (9) is controlled by a control system (10) for controlling hydraulic, system (9) from above water, in particular from a vessel. Hydraulic system (9) comprises three lines, two for supply and discharge of fluid (19) for the hydraulic system and a line (20) for discharge of the leaked fluid. Control system (10) comprises an electrical cable (18), a control valve unit (16) and a control unit for above water (21). The line (22) through cables (15, 18, 19, 20) and tube (2) represents the transition between the water and a vessel. This is intended to indicate that the control unit for above water (21) is situated in the vessel. In order to lower frame (4) to bottom (3) the frame (4) is provided with cables (15) which are preferably under constant tensile force, also during drilling with tube (2).

Claims

1. Device (1) for rotary drilling with a tube (2) in a bottom (3) located under water, characterized in that the device (1) comprises a frame (4) to be placed on the bottom (3), which frame (4) is provided with rotatable first engaging means (5) for clampingly engaging and rotating the tube (2) for the purpose of rotary drilling with the tube (2) into the bottom (3).

2. Device (1) as claimed in claim 1, characterized in that the frame (4) is provided with rotating means (8) for rotating the first engaging means (5).

3. Device (1) as claimed in claim 1 or 2, characterized in that the frame (4) has a weight such that the gravitational force acting on the frame (4) is at least in the same order of magnitude as the friction force which the tube (2) usually undergoes in the bottom (3) in operative mode.

4. Device (1) as claimed in claim 1 or 2, characterized in that the weight of the frame (4) is at least 5,000 kg.

5. Device (1) as claimed in any of the claims 1-4, characterized in that the frame (4) is provided with lifting means (6) co-acting with the first engaging means (5) for the purpose of lifting the first engaging means (5) situated in a non- clampingly engaging position.

6. Device (1) as claimed in any of the claims 1-5, characterized in that the frame (4) is provided with stationary second engaging means (7) for clampingly engaging the tube (2).

7. Device (1) as claimed in any of the claims 2-6, characterized in that the device (1) comprises a hydraulic system (9) for driving the rotating means (8) from above water.

8. Device (1) as claimed in claim 7, characterized in that the device (1) comprises a control system (10) for controlling the hydraulic system (9) from above water.

9. Device (1) as claimed in any of the claims 1-8, characterized in that the device (1) comprises compensating means (11), such as at least one winch, for compensating in operative mode the movement of tube-handling means (12), situated above water, relative to the tube (2).

10. Method for rotary drilling with a tube (2) into a bottom (3) situated under water using a device (1) for rotary drilling with a tube (2) into a bottom (3) situated under water, which device (1) comprises a frame (4) to be placed on the bottom (3), which frame (4) is provided with rotatable first engaging means (5) for clampingly engaging and rotating the tube (2) for the purpose of rotary drilling with the tube (2) into the bottom (3), characterized in that the method comprises of lowering the frame (4) from above water to the bottom (3) and extending the tube (2) until it extends from the frame (4) to a position above water.

11. Method as claimed in claim 10, characterized in that the frame (4) is also provided with rotating means (8) for rotating the first engaging means (5) and lifting means (6) co-acting with the first engaging means (5) for the purpose of lifting the first engaging means (5) situated in a non- clampingly engaging position, wherein the lifting means comprise at least one, preferably two hydraulic cylinders (13), which hydraulic cylinders (13) can exert a pushing and a pulling force on the first engaging means (5), and the device (1) comprises a hydraulic system (9) for driving the first engaging means (5), the rotating means (8) and the hydraulic cylinder (13) from above water, and the device (1) comprises a control system (10) for controlling the hydraulic system (9) from above water, which method comprises of operating the control system (10) such that - the hydraulic cylinder (13) exerts a substantially upward force on the first engaging means (5) and the engaging means (5) are situated in a non- clampingly engaging position, and subsequently the hydraulic cylinder (13) exerts a substantially downward force on the first engaging means (5), the first engaging means (5) are situated in a clampingly engaging position and the rotating means rotate the first engaging means (5).

12. Method as claimed in claim 11, characterized in that the frame (4) is also provided with second engaging means (7) and the hydraulic system (9) can also drive the second engaging means (7), which method comprises of operating the control system (10) such that the first engaging means (5) are situated in a non- clampingly engaging position, the lifting means (6) lift the first engaging means (5) and the second engaging means (7) are situated in clampingly engaging position.

Device for rotary drilling with a tube into a bottom located under water

Abstract

The invention relates to a device for rotary drilling with a tube into a bottom located under water, characterized in that the device comprises a frame to be placed on the bottom, which frame is provided with rotatable first engaging means for clampingly engaging and rotating the tube for the purpose of rotary drilling with the tube into the bottom. The invention further relates to a method for rotary drilling with a tube into a bottom situated under water using such a device, characterized in that the method comprises of lowering the frame from above water to the bottom and extending the tube until it extends from the frame to a position above water.