Methods and apparatus are described for performing a 4D monitor marine seismic survey that repeats a previous survey. A number of sources may be used during the 4D monitor survey that differs from a number of sources that were used during the previous survey. Shot points from the previous survey are repeated by the 4D monitor survey, and additional shot points may be produced during the 4D monitor survey that were not produced during the previous survey. Embodiments enable efficiency and data quality improvements to be captured during 4D survey processes, while preserving repeatability.

An autonomous underwater seismic wave generation system includes a housing, and an autonomous navigation system, a propulsion system and a seismic wave generator, each connected to the housing. The autonomous navigation system can navigate the autonomous underwater seismic wave generation system to subsea locations including a location on a seabed. The propulsion system can drive the autonomous underwater seismic wave generation system to the location on the seabed. The seismic wave generator can couple to the location on the seabed to generate seismic waves at the location on the seabed.

The present disclosure is directed to a MEMS-based rotation sensor for use in seismic data acquisition and sensor units having same. The MEMS-based rotation sensor includes a substrate, an anchor disposed on the substrate and a proof mass coupled to the anchor via a plurality of flexural springs. The proof mass has a first electrode coupled to and extending therefrom. A second electrode is fixed to the substrate, and one of the first and second electrodes is configured to receive an actuation signal, and another of the first and second electrodes is configured to generate an electrical signal having an amplitude corresponding with a degree of angular movement of the first electrode relative to the second electrode. The MEMS-based rotation sensor further includes closed loop circuitry configured to receive the electrical signal and provide the actuation signal. Related methods for using the MEMS-based rotation sensor in seismic data acquisition are also described.

An example system can comprise autonomous submarines and an auxiliary station including a power supply. Each autonomous submarine can include a respective power supply and a respective marine survey node coupled thereto. The auxiliary station can be configured to dock the autonomous submarines in a body of water and recharge the respective power supply of each of the autonomous submarines via the power supply of the auxiliary station. Each autonomous submarine can be configured to autonomously navigate from and return to the auxiliary station and position the respective marine survey node on an underwater surface.

Recorded seismic data includes seismic traces having respective source orientation angles, where the source orientation angles represent deviations in seismic source orientation relative to an inline survey direction. A plurality of designature operators corresponding to respective designature orientation angles within a defined set of designature orientation angles may be generated. For a given member of the defined set of designature orientation angles, a corresponding designature operator may be applied to the recorded seismic data to generate designatured seismic data for the given designature orientation angle. For a given seismic trace having a given source orientation angle, the designatured seismic data may be interpolated to generate a designatured version of the given seismic trace. The results may be stored in a tangible, computer-readable medium.

One or more first sensors may be configured to sense seismic signals and one or more second sensors may be configured to sense electromagnetic crosstalk signals. The second sensors are not responsive to the seismic signals. The data from the first and second sensors may be recorded as first data and second data, respectively. The first data may be modified based on the second data to remove the electromagnetic crosstalk noise form the seismic data.

A system to perform marine surveying may include a pair of identical design autonomous marine survey vehicles configured for coordinated operations. The vehicles may navigate and transit from a launch location to a geographically distant designated survey location, continuously survey and transit to a designated recovery location. A pair of vehicles may operate interchangeably at the sea surface, semi-submerged and underwater. Each may generate energy when operating at the surface and store energy in a rechargeable battery to power vehicle operation. The payload may include a sensor system to acquire seabed sensor data. A data storage system may store the sensor data. An on-board payload quality control system may analyze data validity. Positioning when the vehicle is collecting seabed sensor data may be determined with high precision, to provide survey data of high precision.

An autonomous seismic node is configured for free-fall from a water surface to the seabed and is capable of rising from the seabed on its own. The seismic node is positively buoyant in water and is substantially tubular in shape, with a length to a diameter ratio of 4:1 or greater. The node comprises a lower section and an upper section, each of which is inserted into an end of a tubular housing. The lower section has a lower end cap assembly with a release mechanism and the upper section has an upper end cap assembly with a plurality of electronic components and a detachable lifting cage. The seismic node may be coupled to a detachable anchor weight or seabed coupling device to assist in free fall to the seabed, and when detached after seismic recording is performed, allows the seismic node to rise to the water surface.

A method and apparatus for marine surveying. A system includes: a standard-volume source element; a large-volume source element comprising an airgun having a volume greater than 1200 cubic inches; and a long-offset survey streamer. A method includes: towing a standard-volume source element; and towing a large-volume source element; activating the large-volume source element at large shotpoint intervals; and activating the standard-volume source element at standard shotpoint intervals, wherein the large shotpoint intervals are at least twice as long as the standard shotpoint intervals. A method includes: obtaining geophysical data for a subterranean formation; and processing the geophysical data to produce an image of the subterranean formation. A method includes: obtaining a firing plan for a plurality of seismic sources, wherein: a first seismic source of the plurality comprises a large-volume source element, and a second seismic source of the plurality consists of standard-volume source elements.

An acoustic vector sensor has an array of sensors to detect at least the bearing of a target. The acoustic vector sensor or hydrophone with sensor array avoids the need to deploy multiple hydrophones each with a single sensor. The array of sensor signals can be processed using any one of a number of methods.