Abstract: A seismic spread is constructed having an arrangement of towed components to be neutrally buoyant in water when towed in a seismic survey. The towed components at least include streamers and paravanes. Immersed weight and drag of the towed components is determined, and drag forces versus buoyancy required to neutrally buoy the towed components at at least one tow speed in the water is calculated based on the determined weight and drag of the towed components. Floatation is configured for the seismic spread based on the calculated drag forces versus buoyancy; and the arrangement of the towed components in the seismic spread is constructed with the configured floatation.

Abstract: In seismic survey for icy waters, streamers are towed behind a vessel under the water's surface to avoid ice. GPS readings may not be consistently obtained because the ice prevents a tail buoy with a GPS receiver from trailing from streamer at the surface. Instead, a device tows on the streamer under the water's surface. The streamer's absolute position is tracked by intermittently bringing the towed device toward the surface so GPS readings can be obtained. The streamer's absolute position can then be used in conjunction with compass readings and can correlate various seismic sensor signals obtained along the streamer during the survey. The compass readings can be corrected for declination using declinometer readings, which can be compensated for iron effects from the vessel or other device carrying the declinometer.

Abstract: 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.

Abstract: Methods, systems, and apparatuses are disclosed for conducting reconnaissance marine seismic surveys. In one example method of acquiring a marine seismic survey, a plurality of streamers are towed behind an acquisition vessel, the plurality of streamers defining a swath. An independent source is towed by an independent source vessel above one or more of the plurality of towed streamers.

Abstract: 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.

Abstract: A marine seismic survey is performed in icy waters by initially planning a survey track traversing a survey area. The initial track is planned based on initial ice conditions in the survey area having the icy waters. After preparing the system, a seismic system is deployed into the water from a survey vessel at the survey area. This is typically done in an area relatively free of ice. At least one escort vessel escorts the survey vessel as it traverses the survey track and obtains seismic data. The survey vessel tows the seismic system under the surface of the icy water to avoid the ice. All the while, systems and operators monitor the survey area along the survey track for actual ice conditions. In this way, the escort vessel can handling the actual ice conditions along the survey track so the survey vessel does not need to halt.

Abstract: 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 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 source. A floatation device supports the source and tows below the water's surface to avoid ice floes. The streamers can have vehicles deployed thereon for controlling a position on the streamer. To facilitate locating the streamers, these vehicles on the streamers can be brought to the surface when clear of ice floes so that GPS readings can be obtained and communicated to a control system. After obtaining readings, the vehicles can be floated back under the surface. Deploying, using, and retrieving the system accounts for ice at the surface in icy regions. In addition, handling the seismic record can account for noise generated by ice impact events.

Abstract: 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 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 source. A floatation device supports the source and tows below the water's surface to avoid ice floes. The streamers can have vehicles deployed thereon for controlling a position on the streamer. To facilitate locating the streamers, these vehicles on the streamers can be brought to the surface when clear of ice floes so that GPS readings can be obtained and communicated to a control system. After obtaining readings, the vehicles can be floated back under the surface. Deploying, using, and retrieving the system accounts for ice at the surface in icy regions. In addition, handling the seismic record can account for noise generated by ice impact events.

Abstract: 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 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 source. A floatation device supports the source and tows below the water's surface to avoid ice floes. The streamers can have vehicles deployed thereon for controlling a position on the streamer. To facilitate locating the streamers, these vehicles on the streamers can be brought to the surface when clear of ice floes so that GPS readings can be obtained and communicated to a control system. After obtaining readings, the vehicles can be floated back under the surface. Deploying, using, and retrieving the system accounts for ice at the surface in icy regions. In addition, handling the seismic record can account for noise generated by ice impact events.

Abstract: In seismic survey for icy waters, streamers are towed behind a vessel under the water's surface to avoid ice. GPS readings may not be consistently obtained because the ice prevents a tail buoy with a GPS receiver from trailing from streamer at the surface. Instead, a device tows on the streamer under the water's surface. The streamer's absolute position is tracked by intermittently bringing the towed device toward the surface so GPS readings can be obtained. The streamer's absolute position can then be used in conjunction with compass readings and can correlate various seismic sensor signals obtained along the streamer during the survey. The compass readings can be corrected for declination using declinometer readings, which can be compensated for iron effects from the vessel or other device carrying the declinometer.

Abstract: 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 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 source. A floatation device supports the source and tows below the water's surface to avoid ice floes. The streamers can have vehicles deployed thereon for controlling a position on the streamer. To facilitate locating the streamers, these vehicles on the streamers can be brought to the surface when clear of ice floes so that GPS readings can be obtained and communicated to a control system. After obtaining readings, the vehicles can be floated back under the surface. Deploying, using, and retrieving the system accounts for ice at the surface in icy regions. In addition, handling the seismic record can account for noise generated by ice impact events.

Abstract: Maleic anhydride is recovered by evaporating the effluent from the production of phthalic anhydride at from 40.degree. to 150.degree.C and from 50 to 760 mm to a water content of less than 10% by weight, heating the concentrate in a thin-film or falling-film evaporator at from 100 to 600 mm at from 120.degree. to 180.degree.C and distilling it in a column. The pure maleic anhydride is withdrawn laterally and the aqueous condensate is recycled to the offgas scrubber.