Methods and systems to separate seismic data associated with impulsive and non-impulsive sources

A method to survey a subterranean formation, the method comprising:

• activating an impulsive source above the subterranean formation to generate an impulsive source wavefield having an impulsive source band of frequencies;
• simultaneously activating a non-impulsive source above the subterranean formation to generate a non-impulsive source wavefield having a non-impulsive source band of frequencies that overlap the impulsive source band of frequencies;
• recording seismic data generated by a receiver, the seismic data represents the response of the subterranean formation to the impulsive and non-impulsive source wavefields;
• and
• separating the seismic data into impulsive source seismic data and non-impulsive source seismic data over the overlap band of frequencies.

A computer system comprising:

• one or more processors;
• one or more data-storage devices;
• and
• machine-readable instructions stored in one or more of the data-storage devices and executed by the one or more processors directed to
• receiving seismic data generated by a receiver that represents a response of a subterranean formation to an impulsive source wavefield generated by an impulsive source and a non-impulsive source wavefield generated by a non-impulsive source;
• receiving a near-field signature of each impulsive source element of the impulsive source and a near-field signature of each non-impulsive source element of the non-impulsive source;
• determining an impulsive source far-field signature of the impulsive source at a location of the receiver based on the near-field signatures of the impulsive source elements and a non-impulsive source far-field signature of the non-impulsive source at the location of the receiver based on the near-field signatures of the non-impulsive source elements;
• and
• separating the seismic data into impulsive source seismic data and non-impulsive source seismic data based on one of the impulsive source far-field signature and the non-impulsive source far-field signature.

A non-transitory computer-readable medium having machine-readable instructions encoded thereon that enables one or more processors of a computer system to perform the operations of

• receiving seismic data generated by a receiver that represents a response of a subterranean formation to an impulsive source wavefield generated by an impulsive source and a non-impulsive source wavefield generated by a non-impulsive source;
• receiving a near-field signature of each impulsive source element of the impulsive source and a near-field signature of each non-impulsive source element of the non-impulsive source;
• determining an impulsive source far-field signature of the impulsive source at a location of the receiver based on the near-field signatures of the impulsive source elements and a non-impulsive source far-field signature of the non-impulsive source at the location of the receiver based on the near-field signatures of the non-impulsive source elements;
• and
• separating the seismic data into impulsive source seismic data and non-impulsive source seismic data based on one of the impulsive source far-field signature and the non-impulsive source far-field signature.

A method of surveying a subterranean formation, the method comprising

• towing an impulsive source above the subterranean formation behind a first survey vessel;
• towing a non-impulsive sources above the subterranean formation behind a second survey vessel;
• activating the impulsive source above the subterranean formation to generate an impulsive source wavefield having an impulsive source band of frequencies;
• simultaneously activating the non-impulsive sources above the subterranean formation to generate non-impulsive source wavefields having a non-impulsive source band of frequencies that overlap the impulsive source band of frequencies;
• and
• recording seismic data generated by a receiver, the seismic data represents the response of the subterranean formation to the impulsive and non-impulsive source wavefields.