A gradient sensor device includes a support structure providing a surface, and at least three particle motion sensors coupled with and/or arranged on the support structure to measure translational data in a first direction. The particle motion sensors have an arrangement that enables calculation of a spatial gradient of the translational data in a second direction different from the first direction.

This disclosure describes processes and systems for generating a high-resolution velocity model of a subterranean formation from recorded seismic data gathers obtained in a marine seismic survey of the subterranean formation. A velocity model is computed by iterative FWI using reflections, resolving the velocity field of deep subterranean targets without requiring ultralong offsets. The processes and systems use of an impedance sensitivity kernel to characterize reflections in a modeled wavefield, and then use the reflections to compute a velocity sensitivity kernel that is used to produce low-wavenumber updates to the velocity model. The iterative process is applied in a cascade such that position of reflectors and background velocity are simultaneously updated. Once the low-wavenumber components of the velocity model are updated, the velocity model is used as an input of conventional FWI to introduce missing velocity components (i.e., high-wavenumber) to increase the resolution of the velocity model.

Methods and apparatus are described for reducing noise in measurements made by one or more pressure sensors disposed in a cable having a generally longitudinal axis. Estimated axial vibration noise at a location along the cable is determined based at least in part on measurements from one or more motion sensors disposed along the cable. The estimated axial vibration noise is subtracted from pressure sensor measurements corresponding to the location. The result is noise-attenuated pressure sensor measurements corresponding to the location.

Method and apparatus for suppressing cable dynamics in a device towed in water. The apparatus includes at least one section for suppression of motion, wherein the at least one section includes an axial motion suppression section; and the axial motion suppression section comprising equipment for the attenuation of axial vibrations in an electro-mechanical cable. The equipment is configured to produce a digressive stiffness curve.

A seismic apparatus includes one or more seismic cable systems configured to acquire seismic data, each seismic cable system having one or more of a cable jacket, a reservoir for a ballast fluid or other ballast medium, and an actuator or other transfer mechanism configured to transfer the ballast fluid between the reservoir and the seismic cable system during acquisition of the seismic data, e.g., where the ballast fluid is transferred to the seismic cable system within the cable jacket. A controller can be configured to adjust a buoyancy of the seismic cable system responsive to the transfer of the ballast fluid, e.g., where the internal volume expands or contract based on the fluid transfer.

The combination of one or more 3-component microseismic sensors deployed into a wellbore adjacent a microseismic event and a linear array of distributed fiber optic acoustic sensors deployed uphole thereof provides two sets of data for establishing noise-free signals for locating the microseismic event in the formation about the wellbore. The distributed fiber optic signals monitor noise transmitted along coiled tubing used to pump a completion operation or as a result of the fluid flowing through the casing or coiled tubing, or along wireline used to deploy the microseismic sensors. The noise is mapped and extrapolated for estimating noise at the 3-component sensors. The estimated noise is removed from the 3-component sensor data for producing clean signals representing the location of the microseismic events.

The combination of one or more 3-component microseismic sensors deployed into a wellbore adjacent a microseismic event and a linear array of distributed fiber optic acoustic sensors deployed uphole thereof provides two sets of data for establishing noise-free signals for locating the microseismic event in the formation about the wellbore. The distributed fiber optic signals monitor noise transmitted along coiled tubing used to pump a completion operation or as a result of the fluid flowing through the casing or coiled tubing, or along wireline used to deploy the microseismic sensors. The noise is mapped and extrapolated for estimating noise at the 3-component sensors. The estimated noise is removed from the 3-component sensor data for producing clean signals representing the location of the microseismic events.

An apparatus for collecting geophysical information may include a geophysical information station disposed along a seismic communication cable. A bypass circuit responsive to a command signal is in communication with a switching circuit that is operable to route electrical power, commands, data or a combination to bypass the geophysical information station in response to the command signal. An exemplary method for bypassing a geophysical information station in a geophysical information collection system includes sending a command signal to a bypass circuit and activating one or more switching circuits using the bypass circuit to route electrical power, commands, data or a combination to bypass the geophysical information station in response to the command signal.

Various examples are provided for land streamer seismic surveying using multiple sources. In one example, among others, a method includes disposing a land streamer in-line with first and second shot sources. The first shot source is at a first source location adjacent to a proximal end of the land streamer and the second shot source is at a second source location separated by a fixed length corresponding to a length of the land streamer. Shot gathers can be obtained when the shot sources are fired. In another example, a system includes a land streamer including a plurality of receivers, a first shot source located adjacent to the proximal end of the land streamer, and a second shot source located in-line with the land streamer and the first shot source. The second shot source is separated from the first shot source by a fixed overall length corresponding to the land streamer.

Fiber optic cable structures suitable for distributed acoustic sensing that are capable of discriminating between stimuli acting on the cable in different directions, the cable structure including a core structure (202, 203, 204) with an optical fiber wound around the periphery of the core structure, the core further including a mass (203) which is movable in a preferred direction within the cable such that movement of said mass in said preferred direction causes a change in length of the fiber wound around the periphery of the core.