The Research On Rock-physics Modeling And Pre-stack Seismic Inversion Of Volcanic Hydrocarbon Reservoirs

Volcanic rock reservoirs are a typical unconventional oil and gas resource.With the development of oil and gas exploration of volcanic reservoirs in the Songliao Basin,Bohai Bay Basin,Junggar Basin,etc.,volcanic rocks(including volcanic clastic rocks)have shown good performance for exploration and development.At present,the rock-physical analysis of volcanic reservoirs is not mature enough and the reservoir fluid identification technology needs to be further improved.According to the characteristics of mineral composition,pore structure and heterogeneity of volcanic reservoir,the rock physical modeling method of volcanic rocks is studied and the corresponding rock physical model is constructed.In view of the problems in the pre-stack CRP gather,an optimized processing flow is established.Based on rock-physical analysis,a frequency-dependent pre-stack seismic inversion method is developed,which can effectively detect fluid types.Volcanic rocks have complex lithology and the main mineral compositions of different lithology are obviously different.Each lithology has the possibility to become effective reservoir.According to the lithological and mineral characteristics of volcanic rocks,this paper establishes a volcanic rock volume interpretation model and develops a complex-leaping frog algorithm to calculate the mineral contents.In the early stage of diagenesis,volcanic rocks have low primary porosity and poor connectivity.Affected by the secondary diagenesis in the later stage,secondary pore such as dissolution pore and fractures are generated those enhance the reservoir property.In this paper,the influence of different pore structures is fully considered.The porosity and aspect ratio of different pores are inverted.Considering the frame heterogeneity caused by minerals and pore structures,the physical modeling method of volcanic rocks is studied,and the physical model of volcanic rocks is established.On this basis,the effects of micro-parameters on macro-elastic properties,as well as the dispersion and attenuation characteristics of rocks are analyzed,which lays the rock physical foundation for frequency-dependent pre-stack inversion.Volcanic reservoirs are usually formed by the combination of products from different periods,and the quality of seismic data is generally poor.In order to ensure the accuracy of the subsequent inversion,the filtering,synthesizing super gather,de-noising,gather pulling and so on are carried to improve the signal-to-noise ratio and resolution of seismic data.Because de-noising will lose some of the effective information,the amplitude energy of the near gather is obviously weakened.This paper develops a set of well-control gather optimization method,which uses logging data to synthesize forward gather and restores the amplitude of the near gather through matching analysis between the synthetic gather and the actual gather.There are abundant amplitude and frequency information in pre-stack seismic data.This paper presents a frequency-dependent pre-stack seismic inversion method.The attenuation characteristics of volcanic strata are obtained by rock-physical analysis.Frequency-dependent indicators are constructed and their sensitivity is verified.On this basis,the reflection characteristic equation is deduced.In order to reduce the multi-solution of fluid detection,this paper further obtains the inversion equation of frequency-dependent fluid factor and achieves frequency division processing of seismic data which provides data basis for the inversion.The D_f?section can effectively identify the fluid type of reservoir and reduce the uncertainty of oil and gas exploration...