Abstract: The embodiments herein describe a seismic source that includes at least two firing heads connected to a shared reservoir of compressed gas. When underwater, a controller can instruct the firing heads to fire at the same time or at different times to create gas bubbles that generate seismic energy for identifying structures underneath a body of water. If the firing heads fire at the same, the resulting gas bubble may coalesce to form a single bubble, depending on the size of the respective bubbles and the separation distance between the firing heads. In one embodiment, the firing heads are attached at opposite ends of the shared reservoir (although this is not a requirement). The length of the reservoir, which dictates in part the separation distance of the firing heads, can be set so that gas bubbles generated by the firing heads at substantially the same time coalesce.

Abstract: An autonomous sensor node for undersea seismic surveying is formed as a sphere with density similar to sea water in order to minimize effects of noise. The node is capable of measuring both seismic pressure waves and water-borne particle velocity in three dimensions. The node floats above the seafloor to greatly decrease the impact of shear wave noise contamination generated by seabed waves. The node is attached to an anchor resting on the seabed by a tether. The tether is configured to prevent transfer of any tensile forces caused by shear waves in the seabed stratum from the anchor to the node. The tether may have a varying density along its length to entirely attenuate any force transfer from the seafloor.

Abstract: The embodiments herein describe a seismic source that includes at least two firing heads connected to a shared reservoir of compressed gas. When underwater, a controller can instruct the firing heads to fire at the same time or at different times to create gas bubbles that generate seismic energy for identifying structures underneath a body of water. If the firing heads fire at the same, the resulting gas bubble may coalesce to form a single bubble, depending on the size of the respective bubbles and the separation distance between the firing heads. In one embodiment, the firing heads are attached at opposite ends of the shared reservoir (although this is not a requirement). The length of the reservoir, which dictates in part the separation distance of the firing heads, can be set so that gas bubbles generated by the firing heads at substantially the same time coalesce.

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. A source is towed behind the acquisition vessel, and at least one other source is towed outside of the swath of streamers.

Abstract: Embodiments of dynamic gain adjustments in seismic surveys are described. One method of acquiring a seismic survey includes determining an arrival time at a seismic receiver of a downgoing seismic wavefield associated with a seismic source based at least in part on an estimated position of the seismic source, an estimated position of the seismic receiver, or combinations thereof. The method also includes adjusting a gain of the seismic receiver based at least in part on the determined arrival time of the downgoing seismic wavefield in order to, for example, help prevent overdriving or clipping of the seismic receiver when the downgoing seismic wavefield arrives at or passes by the seismic receiver.

Abstract: Embodiments of real-time infill in marine seismic surveys using an independent seismic source are described. One method of seismic data acquisition includes acquiring primary seismic data at a plurality of streamers towed by an acquisition vessel based at least in part on energy emitted by a first seismic source, and towing an independent seismic source to acquire infill seismic data at the plurality of streamers based at least in part on energy emitted by the independent seismic source while the primary seismic data is still being acquired at the plurality of streamers based at least in part on the energy emitted by the first seismic source, wherein the independent seismic source is towed independently of the acquisition vessel.

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. A source is towed behind the acquisition vessel, and at least one other source is towed outside of the swath of streamers.

Abstract: Embodiments of dynamic gain adjustments in seismic surveys are described. One method of acquiring a seismic survey includes determining an arrival time at a seismic receiver of a downgoing seismic wavefield associated with a seismic source based at least in part on an estimated position of the seismic source, an estimated position of the seismic receiver, or combinations thereof. The method also includes adjusting a gain of the seismic receiver based at least in part on the determined arrival time of the downgoing seismic wavefield in order to, for example, help prevent overdriving or clipping of the seismic receiver when the downgoing seismic wavefield arrives at or passes by the seismic receiver.

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: Embodiments of real-time infill in marine seismic surveys using an independent seismic source are described. One method of seismic data acquisition includes acquiring primary seismic data at a plurality of streamers towed by an acquisition vessel based at least in part on energy emitted by a first seismic source, and towing an independent seismic source to acquire infill seismic data at the plurality of streamers based at least in part on energy emitted by the independent seismic source while the primary seismic data is still being acquired at the plurality of streamers based at least in part on the energy emitted by the first seismic source, wherein the independent seismic source is towed independently of the acquisition vessel.

Abstract: A method for improving illumination analysis in seismic data having steps of: selecting a model of the medium, a source and a receiver, a reflecting surface, finding a reflection point and the associated Fresnel zone according to Fermat principle using ray tracing, calculating the illumination in the Fresnel zone using the wave equation, repeating the illumination calculation for all frequencies all points on the reflecting surface and all source and the receiver pairs. The resulting illumination image may be used to assess the quality of or improve the seismic image of the same medium.

Abstract: A method for improving illumination analysis in seismic data having steps of: selecting a model of the medium, a source and a receiver, a reflecting surface, finding a reflection point and the associated Fresnel zone according to Fermat principle using ray tracing, calculating the illumination in the Fresnel zone using the wave equation, repeating the illumination calculation for all frequencies all points on the reflecting surface and all source and the receiver pairs. The resulting illumination image may be used to assess the quality of or improve the seismic image of the same medium.

Abstract: A method of determining a reference seismic velocity model that includes lateral and vertical variations in a stratified subterranean medium is disclosed. The invention recognizes that each unknown prestack traveltime curve may be expressed as the sum of a best fit hyperbola and a non-hyperbolic perturbation term. After the best fit hyperbola has been determined and used to correct the traces for normal moveout (NMO), the non-hyperbolic perturbation term is solved for using a simulated annealing technique. In addition, the problem of topologically representing a subsurface having complicated horizon geometries is bypassed by assuming a smooth and continuous, rather than a layered and discontinuous, velocity model. This assumption facilitates raytracing and in most cases, results in a model that more accurately represents the velocity function. Error minimization during model updates is achieved by solving a linear system of equations subject to a set of constraint equations.