Research On Underwater Secondary Positioning For Ocean Bottom Node(OBN) With Seismic Wave

Ocean bottom node(OBN)multi-component seismic exploration is a new type of marine oil and gas seismic acquisition acquisition method,which can effectively obtain seabed tectonic information and oil and gas storage information using longitudinal wave and converted wave data.In the actual seabed node seismic data acquisition operation,the operating ship puts the geophone at the design geophone point during the traveling process state,which is affected by the hull motion state,equipment environment,artificial throwing error,seawater speed change,current tide,ship speed change,The weather at sea,and other factors have a comprehensive influence.The actual location of the sink and the design position of the geophone are often inconsistent.In order to ensure the quality of the subsequent imaging profile,the secondary positioning of the geophone needs to be processed.The current geophone secondary positioning method is divided into two categories: acoustic wave positioning(equipment)and seismic wave positioning.This paper introduces the classification,basic principles and advantages and disadvantages of the secondary positioning methods of two types of underwater geophones.Aiming at the characteristics of the development of the refraction first wave in the shallow sea high-speed geological environment,the original refraction wave method is improved,and a hybrid positioning method is proposed,which uses the direct first wave and the refraction first wave to jointly invert the position of the seabed node,and the model is calculated The results verify the correctness of the method.On this basis,the parameter error analysis that affects the positioning accuracy is carried out.The error analysis results show that the hybrid positioning method can invert the position of the seabed detector when there is a certain error at the first arrival,the calculation efficiency is higher,and it is more suitable for the shallow sea OBN secondary positioning Good adaptability.In view of the fact that the first arrival is not easy to pick up,this paper proposes a waveform cross-correlation method based on grid search.Through grid division,each grid node is regarded as the actual seabed geophone position,and other parameters are controlled under the same conditions.Analyze the waveform similarity between the synthetic seismic records of different nodes and the model records.If the position of the grid node and the position of the seabed detector are the same,the waveform is most related.The correctness of the method is verified by simulation calculation.On this basis,the error analysis of the parameters such as the speed of the seabed medium and the wavelet type that affect the positioning accuracy is carried out.The results show that the method has strong adaptability and can obtain better positioning results when the signal-to-noise of the seismic data is relatively low.In the processing of actual OBN data,the choice of data in the positioning process is determined by analyzing the characteristics of the multi-wave and multi-component of the submarine node data and the effect of orientation on the positioning accuracy.Finally,through the comparison of the multi-directional direct wave positioning results and the hybrid positioning results,it is verified that the shallow positioning method has its unique advantages and certain practicality in the shallow water environment when the number of direct waves and the orientation are insufficient.