Effect Analysis of Gradient Air-gun Source for Exploration

Aimed at our nation's request of exploration and exploitation of marine petroleum and gas hydrate, we studied the signature features of marine air-gun source based on nonideal gas equations and actual conditions. By analyzing signature features of air-guns of clustered, tuned, time-delayed and coded in different 3D marine air-gun source, the optimum firing pattern of marine gradient 3D air-gun arrays has been set up. Because of the complexity of ghosts, traditional seismic acquisition using horizontal air-gun arrays cannot eliminate the ghost effectively. The acquisition applying gradient air-gun array utilizes the ghost's feature that its distance to the desired signal grows with the increase of the source's depth, so it can suppress the source ghost relatively easily and improve the frequency band-width of seismic data. By comparing and analyzing the theory and the actual application effect, the signature simulation of the gradient air-gun source has been verified. Using the gradient source, components of high and low frequency of seismic reflection data are enhanced. Meanwhile, the resolution and signal-to-noise ratio of seismic data are improved and the imaging result becomes better.