| The technology of multi-source blended seismic acquisition is a new method which can improve the acquisition efficiency,reduce the exploration cost,increase the acquisition density,and improve the imaging quality.The mindset of seismic acquisition is changed from the traditional low-efficiency acquisition method that shooting successively and recording discontinuously to the high-efficiency acquisition method that shooting simultaneously and recording continuously.The new technology has also been developed from the simultaneous land vibrators acquisition to today’s simultaneous marine impulse source acquisition,which is highly favored by the industry.Multi-source blended acquisition is specially proposed for the uncontrollable characteristics of marine impulse sources.The sources of different spatial locations are shot by a certain time delay,and a large amount of seismic information is obtained in a short time.However,there is overlap of multi-source wave fields in the seismic data received by the detector,so it is necessary to separate the blended seismic data into single seismic data.In this paper,the principle of multi-source blended acquisition and the overlap of multi-source wave fields is mainly introduced,and the method to effectively separate blended seismic data is proposed.Both simulated data and actual data certify that this method can separate the blended data effectively,which provides theoretical support and technical reserves for the development and application of this technology.In this paper,both mathematical and physical aspects about multi-source blended acquisition principle is explained and the theoretical basis of this technique is illustrated by the derivation of mathematical formulas and the analysis of physical aspects.In the interpretation process,the acquisition parameters related to blended acquisition are introduced: source density ratio,survey time ratio and blending degree,and two different methods of marine blended acquisition,single-ship blended acquisition and multi-ship blended acquisition,which is simulated in this paper.In the derivation of mathematical formulas,the acquisition modes are classified by introducing the blended source operators.For the under-determined blended acquisition method,the introduction of the concept of pseudo-separation provides theoretical preparation for the separation of subsequent blended acquisition data.The pseudo-separation processing of the blended acquisition data does not eliminate the interference of adjacent sources during the blended acquisition,and the signal appears as random impulse noise in the non-common shot field.Based on this feature and through the study of common separation methods,this paper combines common filtering methods,iterative threshold methods and prediction noise methods to achieve the separation of blended data.By suppressing the noise of the pseudoseparated data of the non-common shot field,the effective signal is extracted,which is re-blended and pseudo-separated,and subtracted by the noise suppression result to obtain prediction noise.With iterations,the prediction noise is closer to the original blended noise,and the separation result is closer to the original single shot record.In order to better protect the effective information in the data,this paper proposes the ROD-ROAD detection noise method.Firstly,the noise is detected and then the inverse distance weighting method is used to suppress the noise.Combined with the prediction noise method,the effective information is well preserved.A high signal to noise ratio can be obtained in the first iteration.For complex seismic data,this paper proposes to use omnidirectional multi-level median filtering for noise by large filter windows and for non-noise by small filter windows after noise detection,and optimize the separation results through multiple iterations,which can suppress noise effectively and protect effective information.By testing the simulated data and the actual data,the correctness and effectiveness of the proposed separation method are verified.The above research results show that the technological innovation brought by multi-source blended acquisition technology will change the mindset of seismic data acquisition.The data of overlap wave field obtained by the blended acquisition can be separated into ordinary single shot records by the separation technique,which is convenient for subsequent processing. |
