Hydraulic and earth engineering – Marine structure or fabrication thereof – Floatable to site and supported by marine floor
Reexamination Certificate
2002-02-25
2004-01-27
Pezzuto, Robert E. (Department: 3671)
Hydraulic and earth engineering
Marine structure or fabrication thereof
Floatable to site and supported by marine floor
C114S260000, C114S265000
Reexamination Certificate
active
06682265
ABSTRACT:
The present invention relates to a method of establishing and/or operating a bore well in a bed or floor under a body of water by means of a drilling barge having a derrick and associated drilling equipment. Such drilling barges may be used for drilling in shallow and calm water areas, such as shallow lakes, river mouths etc. When a drilling barge is to be moved from one drilling site to another distant location it can not be moved over rough waters.
The present invention provides a method, which may improve the usability of a drilling barge. Thus, the present invention provides a method of establishing and/or operating a bore well in a bed or floor under a body of water by means of a drilling barge having a derrick and associated drilling equipment, said method comprising: arranging the drilling barge on top of another, larger floatable vessel, moving the floatable vessel to a location of operation, and anchoring the drilling barge in relation to a bed under said body of water so as to substantially align the derrick with an existing or planned bore well.
By using the method according to the invention an existing drilling barge may be made more versatile. While the existing drilling equipment and auxiliary equipment on the drilling barge may be fully utilised, the larger vessel on which the barge is arranged may lift the derrick to an elevated position, whereby also existing bore wells extending downwards from a platform positioned well above the water surface may be serviced and operated. Furthermore, because the drilling barge is arranged on top of a relatively large vessel anchored to the seabed or sea floor, the drilling barge may be used also in less calm and deeper areas than if the barge had been used separately. Finally, the larger vessel carrying the drilling barge may be used as a means of transportation, which is more resistant to less favourable weather conditions than the drilling barge in itself.
The drilling barge may be positioned on the other floatable vessel in any known manner, for example by means of a stationary or floating crane. However, according to the invention the arranging step may include submerging at least one end of the larger vessel, towing the drilling barge into a desired position in relation to the larger vessel, and raising the submerged end of the larger vessel so as bring the deck of the larger vessel into contact with the bottom of the drilling barge and to lift the drilling barge out of the water.
The larger vessel may be submerged and later raised by pumping water into and out from selected water tanks or chambers contained in the larger supporting vessel. Therefore, the drilling barge may be positioned on top of the other vessel, such as a larger barge or another ship, exclusively by means present on the larger vessel. It is possible to submerge the whole supporting vessel. However, it is more preferred to submerge only the end of the vessel on which the drilling barge should be positioned. Thus, the stern of the larger vessel may be submerged and the drilling barge may thereafter be towed into the said position by towing means arranged on the larger vessel. The towing means may, for example, be a winch with a wire, which may be connected to the stem of the drilling barge. The drilling barge is preferably towed or pulled to a position in which the major part is supported on the deck of the larger vessel, while the part of the drilling barge carrying the derrick and other drilling equipment extends beyond the stern of the larger supporting vessel.
The larger vessel carrying the drilling barge may be floating when the equipment on the drilling barge is operating for drilling a bore hole or bore well in the sea floor or for operating or servicing an existing bore well. In such case the anchoring of the drilling barge includes anchoring of the larger vessel in relation to the bed under the body of water, the drilling barge being fastened immovably in relation to the vessel. The larger floatable vessel may be anchored to the sea floor by mooring lines or other known anchoring means. Such anchoring means may be of the quick-release type such that the drilling vessel may be released quickly if required due to weather conditions or for other reasons. However, alternatively or additionally anchoring may be obtained by submerging the larger vessel so as to position the vessel in contact with said bed, whereby a very stable positioning of the vessel in relation to the sea floor may be obtained.
In order to allow selective adjustment of the height of the lower end of the derrick in relation to the water surface or existing bore well installations supporting spacing means may be arranged between the drilling barge and the larger vessel, so as to position the drilling barge and the drilling equipment thereon in a desired position in relation to the bed or installation. Such spacing means may be replaceable spacing members. In the preferred embodiment, however, the spacing means may comprise hydraulic rams for adjusting the height of the drilling barge and of the derrick positioned thereon.
The drilling barge occupies only a minor part of the deck space of he larger vessel. Therefore, a crane may be positioned on the deck of the larger vessel and may be used for preparing the drilling site, such as for replacing damaged or defective parts of bore well installations.
Even though the main purpose of the larger vessel is to support the drilling barge it may also be used for transporting the drilling barge from one location to a distant second location or drilling site. Because the larger vessel is more seaworthy than the drilling barge the combined vessel may be towed over more rough waters than the separate drilling barge. However, when the transport takes place along more calm waterways it may be preferred to tow the drilling barge and the larger vessel separately, and if the waterways are so narrow that the larger vessel is not allowed to pass as a separate unit, the larger vessel may be divided longitudinally into two separate sub-vessels so as to allow transportation of the vessel on rivers and other narrow waterways, the sub-vessels being subsequently reunited to re-establish said vessel, whereupon the drilling barge may be lifted or pulled into position on top of the large vessel so as to establish the combined drilling vessel, which may then be put into operation. The sub-vessels may advantageously be reunited by pulling them together by means of wires and associated drawing equipment, such as anchor winches, bollards and other standard marine equipment arranged on these sub-vessels.
The drilling barge may later again be disconnected from the larger vessel and used separately at said second drilling site, when the height or depth of the water body does no exceed a predetermined low value, and where larger waves do not occur.
The larger vessel does not function only as a support or base for the drilling barge, but the space on deck of the larger vessel not occupied by the drilling barge may be used for several other useful purposes in support of the activities performed by the equipment on the drilling barge. As examples such space may be used for personnel accommodation storage area and/or workshop area, etc. to support various offshore operations.
The method according to the invention may be used in connection with drilling and related activities, including activities in connection with the preparation, operation and service of production wells. Thus, as an example, the combined drilling barge and larger vessel may be used for assembling and laying a pipeline on the seabed below the body of water, pipe lengths from the storage area being interconnected at the workshop area so as to form a pipeline, which is gradually immersed into the body of water as it is being formed. Preferably, when the pipeline is being immersed it may pass through a tensioning system suspended in the derrick of the drilling barge.
The present invention further provides a drilling vessel comprising a drilling barge having a derrick and associated drilling equipment, an
A.P. Moller-Maersk A/S
Beach Thomas A.
Pezzuto Robert E.
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