Modular structure for protecting an offshore vessel in a body of water from forces of ice features comprising a protective harbor wall, a flotation support, a pile, and a telescoping connection. The telescoping connection is operatively coupled to the protective harbor wall and the flotation support and constructed and arranged to axially move the protective harbor wall between a retracted position and a raised position. The protective harbor wall is constructed and arranged to enclose a harbor space and to counteract the forces of ice features. The flotation support supports the protective harbor wall and is constructed and arranged to change net buoyancy of the modular protective structure to submerge the structure such that the flotation support is positioned on a seabed. The pile is constructed and arranged to be partially disposed in the seabed to maintain the position of the flotation support on the seabed.

Modular structure for protecting an offshore vessel in a body of water from forces of ice features in the body of water is described. The modular protective structure comprising a protective harbor wall constructed and arranged to enclose a harbor space and to counteract the forces of ice features in the body of water. The modular protective structure also comprising a flotation support supporting the protective harbor wall. The flotation support having a capacity to position the modular protective structure at a raised position where the flotation support maintains at least a portion of the protective harbor wall above the water surface such that a harbor is established and the offshore vessel is protected from the forces of ice features in the body of water. Methods which utilize such a modular protective harbor structure are also described.

A process for drilling a well into the seafloor at an offshore drilling location, in particular in arctic regions, the process comprising: drilling a top hole part of the well during a winter season where the water at the drilling location is at least partly covered by ice; and initiating drilling a lower part of the well extending into a hydrocarbon-bearing formation during a subsequent off-winter season where the water is less ice infested than during the winter season.

A skeg mounts from the stern of a towing vessel and extends below the waterline. A channel in the skeg protects cables for steamers and a source (e.g., air gun array) of a seismic system deployed from the vessel. Tow points on the skeg lie below the water's surface and connect to towlines to support the steamers and the source. A floatation device supports the source and tows below the water's surface to avoid ice floes or other issues encountered at the water's surface. Seismic streamers have head floats supporting the streamers. Each of the floats has adjustable buoyancy preconfigured to counterbalance the weight in water of the towed component that the float supports. Acoustic signals from a transceiver at the vessel find locations of the towed components. A towed fish at a lower level than the towed components also uses acoustic signals with a transceiver to further refine the locations of the towed components.

A skeg mounts from the stern of a towing vessel and extends below the waterline. A channel in the skeg protects cables for steamers and a source (e.g., air gun array) of a seismic system deployed from the vessel. Tow points on the skeg lie below the water's surface and connect to towlines to support the steamers and the source. A floatation device supports the source and tows below the water's surface to avoid ice floes or other issues encountered at the water's surface. Seismic streamers have head floats supporting the streamers. Each of the floats has adjustable buoyancy preconfigured to counterbalance the weight in water of the towed component that the float supports. Acoustic signals from a transceiver at the vessel find locations of the towed components. A towed fish at a lower level than the towed components also uses acoustic signals with a transceiver to further refine the locations of the towed components.

A skeg mounts from the stern of a towing vessel and extends below the waterline. A channel in the skeg protects cables for steamers and a source (e.g., air gun array) of a seismic system deployed from the vessel. Tow points on the skeg lie below the water's surface and connect to towlines to support the steamers and the source. A floatation device supports the source and tows below the water's surface to avoid ice floes or other issues encountered at the water's surface. Seismic streamers have head floats supporting the streamers. Each of the floats has adjustable buoyancy preconfigured to counterbalance the weight in water of the towed component that the float supports. Acoustic signals from a transceiver at the vessel find locations of the towed components. A towed fish at a lower level than the towed components also uses acoustic signals with a transceiver to further refine the locations of the towed components.

A skeg mounts from the stern of a towing vessel and extends below the waterline. A channel in the skeg protects cables for steamers and a source (e.g., air gun array) of a seismic system deployed from the vessel. Tow points on the skeg lie below the water's surface and connect to towlines to support the steamers and the source. A floatation device supports the source and tows below the water's surface to avoid ice floes or other issues encountered at the water's surface. Seismic streamers have head floats supporting the streamers. Each of the floats has adjustable buoyancy preconfigured to counterbalance the weight in water of the towed component that the float supports. Acoustic signals from a transceiver at the vessel find locations of the towed components. A towed fish at a lower level than the towed components also uses acoustic signals with a transceiver to further refine the locations of the towed components.

A retractable thruster for a swimming vessel is provided, wherein the retractable thruster includes a propeller and a lifting and lowering arrangement which is configured to vertically move the propeller between a retracted position and an ejected position. In the retracted position the propeller is substantially inside a bottom well of the swimming vessel and in the ejected position the propeller is substantially outside the bottom well. The retractable thruster includes a water-permeable protective element configured to be located inside the bottom well above the propeller and configured to vertically move with the propeller. In the ejected position the water-permeable protective element is configured to substantially prevent loose ice from drifting inside the bottom well through the water-permeable protective element and when the propeller is moved from the retracted position to the ejected position, the water-permeable protective element is configured to push ice out of the bottom well.

A marine seismic surveying apparatus for obstructed waters includes a deployed device and a buoy. The deployed device is disposed at an end of a streamer and is towed below a surface of water. The buoy extends from the end of the streamer to the water's surface. A coupling connects the buoy to the end of the streamer and is breakable due to tension from the buoy obstructed at the surface of the water. A receiver associated with the buoy obtains location information via the buoy at the water's surface. The deployed device can reckon its location with an inertial navigation system in place of location information obtained with the buoy's receiver. Also, the buoy can be deployed at the surface of the water, and more than one buoy can be available for deployment should one be lost.

A marine seismic surveying apparatus for obstructed waters includes a deployed device and a buoy. The deployed device is disposed at an end of a streamer and is towed below a surface of water. The buoy extends from the end of the streamer to the water's surface. A coupling connects the buoy to the end of the streamer and is breakable due to tension from the buoy obstructed at the surface of the water. A receiver associated with the buoy obtains location information via the buoy at the water's surface. The deployed device can reckon its location with an inertial navigation system in place of location information obtained with the buoy's receiver. Also, the buoy can be deployed at the surface of the water, and more than one buoy can be available for deployment should one be lost.