Wide-band Seismic Data Mining And Identification Of Oil And Gas

The complexity and concealment feature of oil and gas exploration goals call for higher exploration precision and better identification methods of oil and gas,so it has become a urgent problem for geophysical workers to develop new and more effective methods of oil and gas identification. After decades of research and development, people have proposed a number of methods of oil and gas identification which have made many successful exploration examples in practical application. However, each method is not size-fits-all effective and has some limitations because of the complexity of geological structure and lithology underground which is one of the reasons that make the research carried out step by step.In view of the shortcomings that people tend to use the seismic information within pass band and hardly use the information out of cut-off and roll-off during conventional seismic data processing and interpretation, this paper explores a variety of methods to identify oil and gas from perspective of full-frequency band by self-programming. Among them, the use of low-frequency seismic information is divided into two sides: first, low frequency information can be directly used for hydrocarbon detection whose theoretical foundation is that when seismic waves go through oil and gas formation, low-frequency information has weaker attenuation which makes sure that low frequency information retain richer lithology-related information; second, identification method of oil and gas based on low frequency shadow which is mainly due to the attenuation characteristics when seismic??es propagate in medium filled with fluid: frequency-selective absorption and phase delay, which result in that low-frequency high-energy zone of seismic wave field appears in the bottom of layer filled with fluid,that is low frequency shadow. In this paper, high frequency information is mainly used to identify oil and gas by its high frequency attenuation characteristics besides the direct use in subtle structure characterization of oil and gas geological body by its high-resolution characteristic, because while high frequency components go through oil and gas layer and attenuate,its absorption coefficient significantly increase,which provides basis and ideas for us to predict oil and gas by absorption and attenuation characteristics of high frequency information.In this paper,firstly,we begin from conventional time-frequency analysis methods, propose a new high-precision time-frequency analysis method-Adaptive Generalized S transform based on deep research and exploration the advantages and disadvantages ofShort-timeFouriertransform,wavelettransform,Wigner-Ville distribution,S transform and other signal analysis methods, this method is achieved by adding a new parameter in S transform to adjust the width of window adaptively according to characteristics of different components,and finally optimizes the time-frequency distribution,which provides a more effective tool and means for us to extract various seismic slice,single frequency section and attenuation propertie section based on time-frequency analysis in the following chapter.Then, after recognizing and analyzing the basic concept, causes and laboratorial physical simulation results abroad of low frequency shadow, we make detailed discussion about oil and gas identification method and principle based on low frequency shadow, deduce the solution of two dimentional viscous and diffusive wave equation,analyze and conclude the change characteristic and law of seismic wave field in medium filled with fluid which changes versus the change of viscous coefficient and diffusive coefficient, make numerical simulation on theoretical mod??and obtains the similar results to that of physical modeling, theoretically verifies the existence of low frequency shadow below layer filled with fluid, also offers basis for the feasibility of oil and gas identification based on low frequency shadow and demonstrates application prospect of the method.Then,this paper explores oil and gas identification methods based on high frequency attenuation property,of which two methods called energy absorption analysis and frequency attenuation gradient are introduced to analyse high-frequency attenuation property of seismic wave and directly be used for oil and gas identification. Theoretical models reveal the feasibility and effectiveness of the methods.The last chapter gives the application examples of wide-band seismic information in oil and gas identification,whose results achieve high conformity with drilling data and the effects are remarkable.Theoretical models together with actual data applications show that the methods and research thoughts proposed in this paper are feasible, and have certain significance for oil and gas identification and reservoir prediction in complex areas.