The Effects Of Explosive Parameters On Seismic Source Wavelet Response In Different Surface Media

In land seismic exploration for oil and gas,the explosion parameters,including exciting media,explosive detonation velocity,charge weight,charge diameter,coupling material and geometry coupling,have important effects on amplitude and frequency features of signals in seismic records.Until recently,the recognition of the effect of the explosion parameters mainly comes from field tests,and lacks theoretical verification.Based on mechanics of explosion and plastoelasticity,this paper proposed the method for calculation of seismic source wavelet generated by explosion in rock and soil,with the combination of numerical simulation and the spherical source model.The source wavelet calculation proposed in this paper consist of three steps:the first step is the numerical simulation of explosion in rock and soil,and analyze the plastic-elastic boundary(PEB)size and pressure curve.Then,a curve fitting is performed on the pressure curve with the function which is the product of the sine function and the exponentially decay function.Last,the source wavelet is calculated using the spherical source model,by inputting medium elastic properties,PEB size and pressure function.Based on the proposed method and different types of surface medium,this paper calculated the source wavelet generated by different explosion parameters,and analyzed the relationship between its amplitude and frequency features and the explosion parameters.The research shows that the source wavelets of limestone and sandstone have high main frequency and lack amplitude in low frequency,which can be enlarged by applying a high detonation velocity explosive,a large charge weight,a large charge diameter and water coupling.The main frequency and frequency band of source wavelet of loess is small,which can be increased by using a low detonation velocity explosive,a small charge weight,a large charge diameter and clay coupling.The comparison between theoretical analysis and field observation result by previous scholars shows that,there is similarity in aspects including surface media and source wavelet shape,amplitude and frequency,detonation velocity and source wavelet amplitude,charge weight and source wavelet frequency in loess,coupling parameter and source wavelet amplitude in limestone.The result explained some experience and real data from field tests,and can serve as a guide to the selection of detonation velocity,charge mass,charge diameter and coupling parameters concerning specific surface medium condition.