GB2231601A

GB2231601A - Extracting and conveying a layer of material which is underwater

Info

Publication number: GB2231601A
Application number: GB9002297A
Authority: GB
Inventors: Reiner Bruggemann; Theo Fromme; Cornelis Heuvelmann; Bernd Kummeter; Dee Huibert Van
Original assignee: Bilfinger und Berger Bau AG
Current assignee: Bilfinger SE
Priority date: 1989-06-22
Filing date: 1990-02-01
Publication date: 1990-11-21
Also published as: NL8902028A; DE3920392A1; GB9002297D0

Description

tjt:23 X CZ50 X EXTRACTING AND CONVEYING A LAYER OF MATERIAL WHICH IS

UNDERWATER The invention relates to a method of and an apparatus for extracting and conveying a layer of material which is situated under water, for example sand and gravel, where the deposit is overlaid with non-exploitable or unwanted layers.

A method and an apparatus are disclosed in DE-A-27 28 853 and GB-A1529522 (Shell) whereby minerals are mined from a subsurface deposit. In this method a bore-hole is made first of all in a manner not explained in detail. In the upper and lower regions the bore-hole is protected against collapse of the bore-hole walls by means of casings which are, for example, cemented to the bore-hole walls. In the region of the bore-hole where there is no casing, the minerals are stripped and reduced by liquid jets which escape through jet nozzles in an outer liquid feed pipe, sink into the sump between the lower casing and an intermediate liquid feed pipe and are conveyed upwards in an inner pipe by means of a water jet pump. The outer pipe can be rotated continuously or intermittently as required and moved up and down.

This method known from DE-A-27 28 853 and GB-A-1529522 (Shell) and the associated apparatus are highly suitable for loosening, reducing and conveying minerals which are present in the form of solid rock. From a technical viewpoint, the method and the apparatus may also still be used for the removal of sedimentary rocks such as sand or gravel. They are however uneconomic. With solid rock the cost and time-intensive separation of the drilling, the lining of the bore-hole and the extraction and conveyance operations is justified, since the time spent on the extraction itself is far greater than with sedimentary rocks and the value of the minerals extracted is also very much higher than that of sedimentary rocks. Rare ores, manganese or similar materials, may well be involved here. In the extraction of sedimentary rocks, which can be loosened far more easily and rapidly and also do not have to be reduced, the same extraction volume can be achieved in a far shorter time. A far larger volume has to be removed overall, and the extraction and conveying plant has to be moved rapidly and frequently.

In one aspect the invention provides a method of extracting and conveying a layer of material situated under water, for example sand and gravel, where the layer is overlaid with unwanted material comprising: passing a casing-conveying pipe with a swivelling displacement drill bit in an initially closed or partially opened bit position through the unwanted bottom layer or layers with an oscillating rotational movement and simultaneous flushing with water and/or air in the drill bit region, opening the displacement drill bit within the bottom layer for extraction and introducing compressed air and/or water within the casing-conveying pipe to initiate an upward-directed conveying flow which carries away with it the material for extraction, and after the extraction of a roughly cylindricallyor conically-shaped volume with a length equal to the depth of the bottom layer for extraction raising the casing-conveying pipe and taking it to the next extraction location.

1 In another aspect the invention provides apparatus for extracting and conveying a layer of material which is situated under water, for example sand and gravel, where the layer is overlaid with unwanted material, comprising:

a) a casing-conveying pipe, having an inner pipe, through which the extracted material is to be removed, and an outer pipe which surrounds the inner pipe and serves as the casing pipe and is rotatable relative to the inner pipe, the inner pipe and outer pipe forming an annular intermediate space, b) a displacement drill bit at the lower end of the pipe which can be opened to expose the lower end of the casing-conveying pipe, c) a rotating mechanism movable alternately in opposite directions, which in use of the apparatus, is positioned at the water level on the outer pipe, and d) at least one air feed pipe which is positioned between the inner pipe and the outer pipe, through which air can be introduced into the inner pipe in the lower region of the casing-conveying pipe.

The method according to the invention and the apparatus according to the invention are preferably used when sedimentary rocks (= loose sediments), for example sand or gravel, are to be extracted from underneath a nonexploitable layer. The non-exploitable or unwanted layers are mostly ooze, clay or marl and can consist of densely packed and lithified regions. The loose sediment for extraction is usually required as building material or for in-fill purposes in land reclamation, which necessitates the development of efficient extraction and conveying methods and equipment.

A major advantage of the apparatus according to the invention is the absence of pumping units susceptible to wear, for example piston or centrigual pumps. The air-lift method known in itself is used for lifting the water-loose sediment suspension. A pipe open at the bottom is immersed in a water-course and compressed air is blown into it in the bottom region, whereby the specific gravity of the water column in the pipe compared with the water outside the pipe is reduced. The water column in the pipe is pressed upwards and a conveying flow is initiated through the continuous injection of compressed air. Pumping rates of for example 3 000 M3/h of suspension can thereby be achieved with minimum expenditure on equipment.

A further major advantage of the apparatus according to the invention lies in the combination of the drilling and extraction functions and the possibility of rapid switching from one mode of operation to the other. Also very advantageous is the use of the rotating mechanism (see for example DE-C-1634404 (Hochstrasser). A rotating rocker movable in opposite directions is preferred for this purpose. The rocker operates on compressed air. At least two working cylinders are activated alternately with compressed air by way of a control cylinder on the rocker, whereby the to and fro movement, the oscillating movement, is obtained. The rotating pulses of the rocker are transferred to the casing pipe by way of lug cams. Torques of up to 40 KNm can be generated in this way. The number of oscillations varies between 30 and 60 per minute, depending on the type of rocker. The independence of this rotating mechanism from a fixed support, for example a drilling platform or a vessel or pontoon, makes operation independent of the swell and rapid relocation of the equipment is possible. The skin friction of the casing- conveying pipe is reduced by the oscillating rotational movement, so that the dead weight of the casing-conveying pipe, which may be approximately 40 tonne in one exemplifying embodiment, is sufficient to produce a rapid drilling process. On safety grounds the rotating mechanism will usually remain suspended from a cane. Problem-free raising of the casing- conveying pipe is also possible with the rotating mechanism described, that is the crane generates the required tractive power, the skin friction being sharply reduced by the oscillating rotation. Even when the casing-conveying pipe adopts out-of-true positions, which can occur for example with subsidence of the non-exploitable layer, the function of the rotating mechanism is not affected. The rotating mechanism works satisfactorily with deflections of up to 450 from the perpendicular.

In the accompanying drawings:

Figure 1 is a general overview of the layout of a casing-conveying pipe; Figure 2 is a section on II-II of Figure 1; Figure 3 to 5 show the entire equipment layout on a pontoon; Figure 6 shows various process stages in the drilling and conveying; Figure 7 is a view of the upper region of the casing-conveying pipe; Figure 8 is a section on VIII-VIII of Figure 7; Figure 9 is a view of the lower region of the casing-conveying pipe; and Figure 10 is a section on X-X of Figure 9.

Figures 1 and 2 show a casing-conveying pipe 1 which is suspended from a crane hanger 22 in the erected state. The crane (not illustrated) stands on a pontoon 28. An erecting scaffold 27 is used for the initial erection. The upper end of the casing-conveying pipe 1 includes: a discharge pipe 23 for the suspension, a flushing water inlet pipe 24, a jet water inlet pipe 25 and an air inlet pipe 26. In the middle region of the casing- conveying pipe 1 a rotating mechanism 4 and a floating body 9 are located, the rotating mechanism 4 being supported and capable of rotation on the floating body 9. In the upper region of the casing-conveying pipe 1 a keyway 21 is located. At the lower end of the casing-conveying pipe 1, a displacement drill bit 2 and flushing water openings 7 can be seen.

Figures 3 to 5 show the entire equipment layout on the pontoon 28. The casing-conveying pipe 1 is suspended in all operating states from a crane 8. On the pontoon 28 are mounted all items of electrical and mechanical equipment, such as generators 31, compressors 32, a jet water pump 33 and a flushing water pump 34. The feeding of air, jet water and flushing water takes place by way of hoses 29 to the casing-conveying pipe 1. A feed hose 30 feeds the conveyed suspension to flushing pipes 35, through which the suspension passes into transport ships.

Figure 6a to 6e show various operating states of the casing-conveying pipe 1. Figure 6a shows the casing-conveying pipe 1 in the initial position at the start of the drilling on a non-exploitable layer c 1 or layer of unwanted material 12. The rotating mechanism 4 with the floating body 9 are located at their lowermost position, namely at the bottom end of the keyway 21. They are free to move over the whole length of the keyway 21. On reaching the water surface 36, as shown in Figures 6c to 6e, the casing-conveying pipe 1 is relieved of the weight of the rotating mechanism 4 and the floating body 9. This confers major advantages in the raising of the casing-conveying pipe 1, since the crane 8 will at least in certain regions not be burdened with this weight, which can reach 25 tonne.

In Figure 6b the casing-conveying pipe 1 has already drilled through the non-exploitable layer 12. The drilling has been carried out forming a clearance bore 18 with simultaneous flushing with pressurised water through openings 15 (see Figure 9) in the drill bit 2. The loosened bottom material in front of the drill bit 2 is transported upwards by way of the clearance bore 18, and a hollow space is thus created so that the casing-conveying pipe 1 can penetrate deeper into the bottom. Figure 6c shows the casing-conveying pipe 1 on further drilling through to a bottom layer 3 due to be extracted. The floating body 9 with the rotating mechanism 4 supported on it has in the meantime reached the water surface 36. Figure 6d and 6e show the casing-conveying pipe 1 in the conveying position. The displacement drill bit 2 is opened, the flushing water now escapes through the flushing openings 7 in the lower region of an outer pipe 1.2 (see Figures 7 to 10) loosens the bottom layer 3 for extraction and brings it into a suspension which is drawn up through an inner pipe 1. 1 (See Figures 7 to 10). The flushing water throughput can be up to 3 000m3/h, is which corresponds to the throughput of the conveyed suspension. This high throughput of flushing water is necessary on the one hand because only a small amount of water is contained in the bottom layer 3, and on the other because it must be anticipated that the clearance bore 18 will be blocked in the non-exploitable layer 12 and thus no water will be able to flow downwards from above by way of the bore 18. In Figure 6e, a roughly cylindrically- or concially-shaped volume 6 which can be conveyed away from an extraction site is shown. The greatest diameter 37 of this volume 6 can reach approximately 30m. The possibility must always be considered of the non-exploitable layer 12 above the volume 6 collapsing and sinking into the hollow space of the volume 6. In so doing the casing-conveying pipe 1 can become jammed. The casing-conveying pipe 1 can be released again and then raised by oscillating rotation of the mechanism 4 and flushing through the flushing openings 7.

Figures 7 and 8 show the upper region of the casing-conveying pipe 1. The inner pipe 1.1, through which the suspension containing the material for extraction is conveyed, ends in the discharge pipe 23, to which the feed hose 30 (see Figures 3 and 5) is connected.

The outer pipe 1.2 is in three parts:

An upper part 38 is connected securely to the inner pipe 1.1. An hydraulic cylinder 17 is also connected to the upper part 38 by a tie-rod 42. A middle part 39 can be displaced in a longitudinal direction relative to the upper part 38; this is made possible by a sliding bearing 41. This displacement, which serves for the opening or closing n t of the drill bit 2, is effected by extension or retraction of the hydraulic cylinder 17, which is connected to a lower part 40 of the outer pipe 1.2 by a bracket 43. The rotating mechanism 4 engages with the lower part 40 by way of the keyway 21. A pivot bearing 19 ensures that on rotation of the lower part 40, the middle part 39 and hence the whole upper region of the casing-conveying pipe 1 does not rotate at the same time. Also shown are the jet water inlet pipe 25, which feeds the jet water by way of an annular chamber 44 and a water feed pipe 10, to an opening 11 in the inner pipe 1.1 in the lower part 40 (see Figure g). The air for raising the water column is introduced into the inner pipe 1.1 by way of the air inlet pipe 26 and an air feed pipe 5. The flushing water inlet pipe 24 opens into the intermediate space 13 between the inner pipe 1.1 and the outer pipe 1.2. Between the inner pipe 1.1 and the outer pipe 1.2 there are located two water feed pipes 10 and the air feed pipe 5, which are supported by a stiffening tubular element 45 and welded stiffening plates 46.

Figures 9 and 10 show the lower region of the casing-conveying pipe 1. In the region of the displacement drill bit 2 the drawing shows two operating states. The left-hand half shows the closed state during drilling and the right-hand half shows the opened state during conveying. The air feed pipe 5 ends in an annular duct 48, from which the injected air escapes through air outlet openings 47 into inner pipe 1.1. Jet water can also be injected into the inner pipe 1.1 through the water feed pipe 10 and the opening 11. In this way either the conveying flow can be reinforced and/or the water content of the suspension be increased. Since the __10 - lower part 40 of the outer pipe 1.2 can be rotated together with the displacement drill bit 2 during the drilling and at times also during the conveying, and the inner pipe 1.1 is not rotatable, a pivot bearing 20 is positioned in the lower region of the inner pipe 1.1.

on a rotatable end piece 51 of the inner pipe 1.1 a tie-piece 52 is fixed, on which, by means of a hinge 53, guide bars 54 are located, which open drill head segments 55 on downward movement of the inner pipe 1.1. The drill head segments 55 are fixed to the lower part 40 of the outer pipe 1. 2 by hinges 56. On the rotatable end piece 51 of the inner pipe 1.1 a large annulus 49 with a valve 16 having valve openings 14 is also fixed. on downward movement of the inner pipe 1.1 the annulus 49 with its valve openings 14 comes to rest on valve cones 50, causing the flushing water, flowing out of the intermediate space 13 to the displacement drill bit 2, to be arrested and at the same time the openings 7 in the outer pipe 1.2 to be uncovered. The opening angle a of the drill bit segments 55 is determined according to the requirements of the respective material for extraction.

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Claims

1. Method of extracting and conveying a layer of material situated under water, for example sand and gravel, where the layer is overlaid with unwanted material comprising: passing a casing-conveying pipe (1) with a swivelling displacement drill bit (2) in an initially closed or partially opened bit position through the unwanted bottom layer or layers (12) with an oscillating rotational movement and simultaneous flushing with water and/or air in the drill bit region, opening the displacement drill bit (2) within the bottom layer (3) for extraction and introducing compressed air and/or water within the casing-conveying pipe (1) to initiate an upward-directed conveying flow which carries away with it the material for extraction, and after the extraction of a roughly cylindricallyor conically-shaped volume (6) with a length equal to the depth of the bottom layer for extraction (3), raising the casing-conveying pipe (1) and taking it to the next extraction location.

2. Method according to claim 1, wherein the extraction and conveyance of the bottom layer (3) takes place continuously with simultaneous raising and/or lowering of the casing-conveying pipe (1).

3. Method according to claim 1, wherein the casing-conveying pipe (1) is lowered to the lower boundary of the bottom layer for extraction (3) and the extraction and conveyance takes place with the casing-conveying pipe (1) only in this position.

4. Method according to any one of claims 1 to 3, wherein during the extraction of the bottom layer (3) water is injected under pressure into the bottom layer (3) for extraction through openings (7) in the lower region of the outer pipe (1.2).

5. Method according to any one of claims 1 to 4, wherein the casingconveying pipe (1) is suspended from a crane (8) in any operating position.

6. Method according to any one of claims 1 to 5, wherein the rotating mechanism (4) is supported on a floating body (9) during the lowering of the casing-conveying pipe (1) and during the extraction process.

7. Method according to any one of claims 1 to 6, wherein during the drilling through of the unwanted layers (12) and the bottom layer for extraction (3) with a closed displacement drill bit (2), flushing water is pumped into the intermediate space (13) between the inner pipe (1.1) and the outer pipe (1.2) by way of a valve opening (14) to the displacement drill bit (2), where it escapes through flushing openings (15).

8. Method according to any one of claims 1 to 7, wherein upon opening of the displacement drill bit (2), a valve (16) in the intermediate space (13) between the inner pipe (1.1) and the outer pipe (1.2) arrests the flow of flushing water to the displacement drill bit (2) and at the same time openings (7) in the lower region of the outer pipe (1.2) are opened, through which the flushing water flows outwards.

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9. A method of extracting and conveying a layer of material situated under water substantially as herein described with reference to and as shown in the accompanying drawings.

10. Apparatus for extracting and conveying a layer of material which is situated under water, for example sand and gravel, where the layer is overlaid with unwanted material, comprising: a) a casing-conveying pipe (1), having an inner pipe (1.1), through which the extracted material is to be removed, and an outer pipe (1.2) which surrounds the inner pipe and serves as the casing pipe and is rotatable relative to the inner pipe (1. 1), the inner pipe (1.1) and outer pipe (1.2) forming an annular intermediate space (13), b) a displacement drill bit (2) at the lower end of the pipe which can be opened to expose the lower end of the casingconveying pipe (1), c) a rotating mechanism (4) movable alternately in opposite directions, which in use of the apparatus, is positioned at the water level on the outer pipe (1.2), and d) at least one air feed pipe (5) which is positioned between the inner pipe (1.1) and the outer pipe (1.2), through which air can be introduced into the inner pipe (1.1) in the lower region of the casing-conveying pipe (1).

11. Apparatus according to Claim 10, wherein between the inner pipe (1.1) and the outer pipe (1.2) an additional water feed pipe (10) is positioned, which is connected by way of an opening (11) with the inside of the inner pipe (1.1) in the lower region.

12. Apparatus according to claim 10 or 11, wherein, 1 in the lower region of the casing-conveying pipe (1), a valve (16) is positioned, by means of which the intermediate space (13) can be sealed with simultaneous uncovering of openings (7) in the outer pipe (1.2).

13. Apparatus according to any one of Claims 10 to 12, wherein the displacement drill bit (2) can be opened by lowering the inner pipe (1.1) relative to the outer pipe (1.2), the lowering being effected by means of hydraulic cylinders (17), which are positioned on the upper end of the casing-conveying pipe (1).

14. Apparatus according to any one of Claims 10 to 13, wherein the displacement drill bit (2) has a greater diameter than the outer pipe (1. 2), so that a clearance bore (18) is obtained during the drilling.

15. Apparatus according to any one of Claims 10 to 14, wherein pivot bearings (19, 20) are positioned one in the upper region of the outer pipe (1.2) and one in the lower region of the inner pipe (1.1).

16. Apparatus according to any one of Claims 10 to 15, wherein at least one keyway (21) for the rotating mechanism (4) is positioned in the outer pipe (1.2).

17. Apparatus according to any one of Claims 10 to 16, wherein the rotating.mechanism (4) is rotatably supported by a floating body (9).

is. Apparatus for extracting and conveying a layer of material which is situated under water substantially as herein described with reference to and as shown in the accompanying drawings.

Published 1990 at The Patent Office. SateHo,.ise.66 71 High Holborn. LondonWC1R4TP Further copies maybe obtainedfrom The Patent OfficeSales Branch, St Mary Cray, Orpington. Kent BR5 3RD. Printed by Multiplex teChIUques ltd, St Mary Cray, Kent, Con. 1187 41