The Study Of Stratigraphy Sequence And Sedimentary System Of The Northern Songliao Basin Of The Period Of Fault-depression Transform

After about60years’ exploration, the Songliao basin has succeed in oil and gasexploration of the depression formation and fauted formation, but the study offault-depression transform formation has made less study. The maximum thicknessof formation is more than800m, which showing a certain exploration potential. It isworthy of study and exploration that whether can be future exploration succeedhorizon. It is no doubt that the sequence stratigraphy and sedimentary systemresearch of the Songliao Basin fault-depression transform the Denglouku strata is animportant and urgent subject. Based on sequence stratigraphy, sedimentologytheory，comprehensive applying core, logging, well logging, seismic data, by thestudy of genetic characteristics, identification and development scale of sequenceboundary，the stratigraphy of the period of fault-depression transform is divided intoSQ1, SQ2, SQ3and SQ4four third-order sequences. Based on joint well contrastand seismic trace, the sequence stratigraphic framework of northern Songliao basinof the period of fault-depression transform is established.Through the sequencestratigraphy analysis, SQ1is filled by coarse clastic sedimentary of proximal alluvialfan system; the sedimentary characteristics similar to the fault sedimentation; Thesedimentary range is small and separated by the central paleouplift. SQ2sedimentaryis mainly coarse-grained sedimentary of fan delta and braided delta transitional typesystem; the sedimentary range is expanded and not separated by the centralpaleouplift; the sedimentary range is northward advancing rapidly advancing. SQ3isfilled by braided river-delta depositional system; the sedimentary range is notobvious expansion.SQ4is filled by the atypical braided river-lacustrine deltasedimentary system; the sedimentary range expand significantly to bothsides.Sequence stratigraphic models of fault-depression transform period issummarized, which is ‘vertical fault to depression, plane layers overlap, depositionalfilling Transform from coarse clastic alluvial fan to the river delta’.On the basis of this, using the principle of source formation process–response,the synthetic recognition of sedimentary source system is carried on under thecontrol of sequence stratigraphic framework. This work is according to corelaboratory testing (heavy mineral, grade, etc.), and the sedimentary characteristics of cores, logging facies, seismic reflection and properties, etc. comprehensive analysisof the combination of heavy mineral, gravel/than, graded gravel thickness, lithologyor the horizontal distribution of components, ancient landform, phase sequence,seismic reflection with attributive character is made. Through comprehensive study,SQ1sequence identified eight proximal ring basins, SQ2identified seven nearsource system, SQ3identified6from the proximal to the far source transitionalsource system, and SQ4identified seven far source provenance systems. It presentedthe gradually evolution characteristics of central combination, such like northlandNeHe provenance, eastern BaiQuan source, southeast of SuiHua source, northwestof qiqihar source, westward Yingtai source; the direction, location, characteristics,types and intersection of the source system is figured out. Further more, the problemof alluvial environment of the period of fault-depression transform sedimentarysource system identification under the conditions of non/thin exploratory well issolved.Taking the early continental basins deposition theoretical model as a guide,4categories24kinds of subfacies and40kinds of sedimentary microfacies depositionsystem is identified based on core. Its detailed characteristics are summarized.Combining the depositional setting paleoecology，paleoclimate and geochemicalcharacteristics with ancient sedimentary environment and the hydrodynamiccharacteristics，the analysis of corresponding core to electrical measuring curve, thelogging sedimentary microfacies mode is established. After carrying out single-welllogging identification, the sedimentary vertical sequence of target layer is recognized.Using seismic reflection and the attributes, the seismic facies are identified andconverted to sedimentary facies. Using the core, logging and seismic, the flatsedimentary facies and combination are identified. The problems of planesedimentary facies division of thick alluvial formation under the conditions of diluteexploratory well are solved.Based on the study of sedimentary system and the types, characteristics andspatial distribution of sedimentary facies, this paper carries out the study of sequence,sedimentary fill type, style and process. And then establishes sedimentary fillingevolution model of near and multi-source alluvial fan-coarse-grained sediments infan deltaâ†'medium and multi-source alluvial fan-braided river-braided riverdeltaâ†'far and main source of alluvial fan-braided river-meandering river-meandering river delta during the fault-depression Transform Period, at last gets thesedimentary filling mechanism combined with tectonics, climate and lake level etc.Under the guidance of sedimentary filling evolution model, this paper researches theevolution stage and area of hydrocarbon source rock, seal and reservoirs, the type, size, distribution, characterized determined by above all, then makes a predictioncombined with the actual data.