The genetic algorithm based velocity structure waveform inversion for gas hydrate bottom simulating reflection (BSR)
Huo Yuan-yuan1,2,4, Zhang Ming3
1. Research Institute of Exploration and Development,North China Branch of Sinopec,Zhengzhou City,Henan Province 450006,China;
2. China University of Geosciences,Beijing City 00083,China;
3. Guangzhou Marine Geological Survey,Guangzhou City,Guangdong Province 510760,China
Abstract：The velocity anomaly of Bottom Simulating Reflection (BSR) is an important sign for detection of gas hydrate.Based on genetic algorithm a full waveform inversion method which can be utilized to identify gas hydrate BSR was presented in this paper.The method contains two steps,the global searching and the local searching,at first the genetic algorithm is utilized to conduct travel time inversion so that the background velocity model is obtained,then with the velocity model as initial model the full wave form inversion is conducted by using of conjugate gradient algorithm.Numerical testing for noisy data shows that the algorithm has a good stability,and the generic operator which is used to conduct gas hydrate BSR full wave form inversion was determined.By applying the wave form inversion algorithm in gas hydrate studies in northern part of South China Sea,The BSR velocity structure whose resolution is higher than routine velocity structure is obtained,and the velocity anomaly of the BSR was also identified,the studies laid foundation for detection of gas hydrate layers and free gas layers and for studies of their distribution and formation.The inversion results proved that the algorithm is very stable and it is applicable for studies of gas hydrate BSR's velocity structure.