Shale Gas Rock Physics Characteristics Of The Weiyuan East-Rongchang North Block In The Sichuan Basin And Their Application In "Sweet Spot" Seismic Prediction

This paper takes the Weiyuan East-Rongchang North block in the Sichuan Basin as the research target area,and conducts seismic petrophysical analysis and "sweet spot" prediction technology research on the Longmaxi Formation shale.Aiming at the target work area,combined with the current achievements of shale gas "sweet spot" prediction technology at home and abroad,the research ideas and research contents of this paper were determined.The Longmaxi Formation shale is currently the main target horizon for shale gas exploration in China,and its seismic petrophysical characteristics are one of the important foundations for the prediction of "desserts" using seismic methods,but the characteristics of the Longmaxi Shale seismic elasticity The study of variation laws and corresponding rock physical characteristics is not systematic enough,which makes the understanding of corresponding laws lack geological significance.In this paper,based on the analysis of the shale logging data and rock physics of the Longmaxi Formation and seismic inversion,combined with the shale reservoir characteristics,this paper analyzes the variation law of the seismic rock physical characteristics of the target horizon,and discusses the corresponding rocks The influence of physical characteristics on the content of shale gas;according to the characteristics of reservoirs and the factors of shale gas enrichment and accumulation,the correlation model between reservoir attribute parameters and elastic parameters is established,and the sensitive parameters are optimized to make a systematic "sweet spot" "prediction.In this paper,the "sweet spot" seismic prediction of the target area is mainly carried out from four aspects: brittleness prediction,lithology prediction,organic carbon content(TOC)prediction and gas content prediction based on seismic wave impedance inversion..Through the analysis of shale reservoir characteristics,in terms of physical characteristics,through the statistical analysis of well 202 and Wei 206 well logging data,the shale porosity of the high-quality shale section is positively correlated with the content of organic carbon(TOC),indicating that the area The pores of the Longmaxi shale are controlled by the content of organic carbon(TOC),and organic pores in high-quality shale sections are more developed;in terms of gas bearing characteristics,the gas content of the shale gas reservoir section of Well Rong 202 and Well 206 is Features of high,low and high;in terms of logging response characteristics,the overall performance is high gamma,low resistance,high acoustic wave time difference,high porosity,and low density;in terms of rock physical characteristics,the following three types of rocks are defined according to rock physical analysis Properties:(1)high-quality shale: TOC> = 0.02,PHIT> = 0.05;(2)dense shale: Vcarb <0.5,TOC <0.02 or PHIT <= 0.05;(3)marl: Vcarb> = 0.5.By analyzing the main control conditions of the shale gas reservoir enrichment and accumulation in the target area,the main control factors of the shale gas reservoir enrichment in the target area are basically determined,including organic geochemical characteristics,physical characteristics,gas content characteristics,and organic carbon content(TOC),shale distribution characteristics,porosity and brittleness conditions,etc.Focusing on the physical property characteristics,gas bearing characteristics,logging response characteristics,and rock physical characteristics of the shale gas reservoir in the target area,combined with the analysis of the main control conditions for the enrichment and accumulation of shale gas reservoirs in the target area,the “sweet spot” prediction of shale gas is carried out Technical research.In this research,work including brittleness prediction,lithology prediction,organic carbon content(TOC)prediction technology,and gas content prediction has been done.Through research,a page for the Weiyuan East-Rongchang North area of the Sichuan Basin has been formed.Rock gas "sweet spot" prediction technology series,the formed technical system mainly includes lithology prediction based on rock physics analysis;TOC prediction gas content method based on rock physics analysis and seismic inversion,this method is mainly through the establishment of TOC and elastic parameters Relevance relationship,and then use the pre-stack and post-stack seismic inversion to obtain elastic parameters such as longitudinal wave impedance,longitudinal and longitudinal wave speed ratio,and then predict the TOC;based on the rock physical analysis and the seismic inversion brittleness index prediction method,the Young’s The relationship between the modulus,Poisson’s ratio and other parameters and the reservoir properties,the results of seismic inversion are used to predict the brittleness of the reservoir;at the same time,the exploration of gas content prediction technology for shale gas reservoirs is carried out,mainly using pre-stack,Post-stack seismic inversion technology,frequency attribute analysis methods,etc.are used to predict the gas content of shale gas reservoirs.