Study On Subtle Trap Prediction Of Dainan Formation At Jinhu Sag

The exploration of subtle reservoir is the key point that needs breakthrough of the whole exploration work on Jinhu sag,the geologists had built the subtle trap growth mode and hydrocarbon accumulation model of this area to develop the right method of trap identification and description,then recommend targets to move the exploration process.After sedimentary system and sand modeling study,the researchers thought that the sources here mainly growth ZhangBaLin ridge in the west and LiuBao-Lingtang low uplift in the east,and party in the north and south also have Jianhu ridge and Tianchang uplift.Five sedimentary facies such as delta,fan delta,lake,submarine fan,sub-lacustrine fan and twelve micro facies have been discovered in E₂d₁;the sand distribution of E₂d₁³,E₂d₁² and E₂d₁¹ in this area had been recognized,the first time fine sand study take the sands group as one unit on the Sanhe-Longgang area had been finished,the ancient landform,slope break,source and hydropower was realized to have important influence to the sand distribution;the results indicate that in this area,there mainly exist trap types as strata overlap and sand lens,sandstone up dip pinch-outs,fault-lithology.By reservoir study and accumulation conditions analysis,the team though the mature source rocks distribution of E₁f₄,source fault development,reservoir cap association and suitable NTG are the main control factors of the subtle reservoir accumulation of E₂d₁.The hydrocarbon accumulation models of deep sag,slope zone and rift zone had been built,the Sanhe area,Duntang-Xiaoguan in eastern part of Longgang and the throw side of Yangcun fault were realized as good prospects of subtle reservoir accumulation.After petrophysics property and seismic data quality analysis,and the feasibility of seismic forward analysis on reservoir in different area,the influential factors of overlap point picking deviation was identified and the deviation was estimated.Also the overlap position of the subsegments had been preliminary identified by top structure description of the subsegments and sand group interpretation.Considered the well-seismic data and reservoir properties,the team used well-seismic velocity associated modeling and Jason-Strata associated inversion constrained by logging data,finished the reservoir quantitative prediction of E₂d₁ after seismic attribute analysis.The seismic data in Sanhe deep sag has features like high SNR and low resolution ratio,lack well data and sub-lacustrine fan grows,so the researchers had to use frequency-broadening processing to improve resolution ratio,use seismic section analysis,attribute analysis and wave impedance inversion associated with modeling based on wavelet edge analysis results to identify the trap.For Gaoji-Lvliang area on the Sanhe slope,there're enough well data and the wave impedance could effectively distinct sand from shale.The reservoir prediction and subtle trap identification was proceeded by using post-stack wave impedance inversion associated with seismic attribute analysis.