Method for reducing inline directivity of air-gun source signature by optimizing spatial distribution of air-guns

A method for reducing inline directivity of an air-gun source signature by optimizing a spatial distribution of air-guns, comprising:

• for an air-gun array, setting a constraint condition in which a spacing between adjacent air-guns and a horizontal spacing between adjacent air-guns satisfy a preset range, and setting an objective function based on the spatial distribution of the air-guns,
• wherein the objective function is expressed by:
• F
• con
• =
• n
• ∑
• i
• =
• 1
• n
• ⁢
• (
• x
• i
• -
• x
• _
• )
• 2
• where Fcon represents a concentration-degree parameter objective function, xi represents a location of the i-th air-gun in a seismic source array inline direction, x represents an average inline location of all the air-guns in the seismic source array inline direction, and n represents the total number of air-guns;
• in a vertical plane, determining a maximum of the objective function by changing an inline location and a depth location of each single air-gun, in a case of a constant spacing between two adjacent air-guns, and obtaining inline locations and depth locations of air-guns corresponding to the maximum of the objective function, as an optimized air-gun array;
• and
• arranging air-guns at different depths based on the optimized air-gun array, setting a respective firing time for each of the air-guns, and firing each of the air-guns with the respective firing time to produce an optimized air-gun combination source, so as to align downgoing primaries of air-guns at different depths and to reduce an inline directivity of the air-gun source signature.