Calculation Of Unconformity Surfaces Denudation Thickness And Its Significance In Rift-subsidence Basin

Renminzhen-Lanxi rift is located in the eastern part of the Songliao Basin faultzone. So far, the study area has the features of low exploration degree in deeplayer, and the existence of denudation in Shahezi formation affects explorationdeployment. The research proceeds centering on the denudation scope and thicknessof Shahezi formation and the prototype of rift basin in the study area, and striveto re-understanding the structure and development characteristics of the rift in order toprovide a reference for further exploration.This paper figures the distribution characteristic of Shahezi residual stratum byreviewing and interpreting seismic data. Combined with regional tectonic setting, thestudy identifies the truncation from the seismic data，analyses the denudation ofShahezi formation, and eventually confirms erosion degree and scope. The studypoints out that the research area experienced a strong tilting and uplifting in thelater-Shahezi Period，so that，in the middle of the rift，there are significantlydenudation in Shahezi formation and in the east area of the rift，the formation erosionexists almost in the whole fault trough.After comeback of denuded strata，in thisresearch,the author holds that two fault troughs,including south one ofpro-renminzhen rift and pro-Lanxi rift，which actually accepted deposition at the sametime，made up a big whole rift,called Lanxi rift, as a opposite arrangementdouble-half graben rift striking nearly SN direction,in the Shahezi Period. Basing onthe work above,the study calculates amount of erosion using tendency analyticmethod and vitrinite reflectance rate,and furtherly recovers the evaluation anddevelopment characteristics of prototype rift-basin. Then, by analysing drilling and seisemic data of, the paper defines the drilling-seisemic data response features ofhigh quality source rocks, evaluates characteristics of source rocks, developed in theshallow-deep-lake、coastal shallow-lake、lake delta and alluvial fan facies,thus,predicts distribution of favourable hydrocarbon,that means source rocks with goodcontinuity and layering showing in the seismic sections are relatively affirmatory.Finally, according to patterns of natural gas accumulation and enrichment described asfault-through controlling source and gas accumulating near source,the study startscomprehensive appraisal of Renminzhen-Lanxi rift by evaluating source rocks、reservoir and reservoir forming condition, furthermore, prefers favorable explorationbelts in the residual basin.