Methods and systems for deriving S-wave velocity information from the low-frequency content of ambient noise are described. The ambient noise can be collected on a dedicated record or on a production record associated with the receivers of a three-dimensional seismic survey. The methods and systems use one of a plurality of analysis models selected based on quality factors of the ambient noise data. The methods and systems analyze the data at a plurality of single frequencies then transform the velocity versus frequency data into velocity versus depth data.

Noise signals can be attenuated on a trace-by-trace basis from traces of marine seismic survey data to yield a signal component and a noise component. A signal-to-noise ratio (SNR) variance of a plurality of traces comprising the signal component can be less than an SNR variance of the plurality of traces comprising the marine seismic survey data. Signal leakage can be attenuated from the noise component to yield a signal leakage component. A seismic image of a subsurface location can be generated based on the signal component and the signal leakage component.

Noise is removed from a data set by performing an integral transform operation that converts instances of noise into identifiable artifacts in the transformed data set. A model of the artifacts is constructed by creating a full-domain or partial-domain noise model and performing the same integral transform operation on the noise model. The resulting transformation of the noise model is adaptively subtracted from the transformed data set to remove the noise. The adaptive subtraction may employ a least-square error filter.

A method can include receiving data in a data domain where a first portion of the data domain includes a signal to noise ratio that exceeds a signal to noise ratio in a second portion of the data domain; generating a model; in a transform domain, based at least in part on the model, filtering at least a portion of the data in the second portion of the data domain; and, based at least in part on the filtering, outputting noise attenuated data for at least a portion of the data in the second portion of the data domain.

The present disclosure describes methods and systems, including computer-implemented methods, computer program products, and computer systems for applying orthogonalization filtering to wavefield separation. One computer-implemented method includes obtaining multi-component wavefields, performing wavefield separation on the multi-component wavefields to obtain separated wavefields, and applying a local orthogonalization weight (LOW) filtering to the separated wavefields to obtain filtered wavefields.

Systems and methods are provided for de-noising seismic data recorded by seismic receivers. A first portion of the seismic data having a first signal-to-noise ratio (SNR) to is processed to generate a de-noising operator or function. The de-noising operator is applied to a second portion of seismic data having a second SNR to remove noise from the second portion of the seismic data, where the first SNR is greater than the second SNR.

Acquired data that corresponds at least in part to a target structure is received. One or more subsets of a first type are formed from the acquired data. The one or more subsets of the first type are converted to one or more subsets of a second, different type.

A method for angle-domain common image gather (ADCIG) of a subsurface formation includes the step of converting seismic incident waves and seismic scattered waves at each of a number of image locations from time domain to frequency domain using Fourier transform. At each image location, the seismic waves in the frequency domain are decomposed into a number of local plane waves. Applying a cross-correlating imaging condition amongst the local plane waves to obtain a partial image at each image location. The plurality of partial images are then sorted into the angle domain.

A method is described for seismic imaging that may include receiving digital seismic data; processing the digital seismic data to create a digital seismic image in a seismic domain; flattening the digital seismic image to generate a digital flattened image; identifying artifacts in the digital flattened image; transforming the artifacts back into the seismic domain; and reprocessing the digital seismic data based on the artifacts in the seismic domain to generate a digital image with reduced artifacts. The method may be executed by a computer system.

A method and system for acquiring spectral information from an energy sensitive nuclear detector is disclosed. The method includes detecting nuclear radiation at a detection device and generating an electronic input pulse indicative of energy deposited in the detection device. The method further includes integrating the electronic input pulse at an integrating device to produce an integrated output signal and digitally sampling the integrated output signal of the integrating device at intervals to produce a stream of digital samples. The method further includes resetting the integrator synchronously with a sampling clock when a limit condition is reached.