Sequence Stratigraphy And Distribution Of The Skeletal Sandbodies Of The Upper Paleozoic In The Huanghua Depression

This thesis takes the Huanghua depression as the study area and the above Paleozoic as the target horizon.On the basis of previous studies,outcrop observation,core description as well as lots of data analyzing,this study also use various techniques,such as rock flake identification,wafer identification,scanning electron microscope observation,X-ray diffraction analysis,physical test,constant trace element analysis and high pressure mercury test.According to the theory of sedimentology,sequence stratigraphy and reservoir geology,the sequence stratigraphic characteristics,sedimentary characteristics and skeleton sandbodies of the upper Paleozoic strata in the Huanghua depression were systematically studied.This thesis adopts the theory and method of sequence stratigraphy,through outcrop,logging curves and other data,also ues the identification marks of surface sequence interface such as regional unconformity surface,undercut surface and transgressive direction surface to identify 15 sequence interfaces.The upper Paleozoic strata in the study area were divided into 7 three-level sequences and 15 four-level sequences.Four stratigraphic sequences are summarized in the Paleozoic strata of the study area which reflect the development characteristics of sequence stratigraphy in four sedimentary systems.Based on the combination of outcrop observation,downhole data,core observation and logging data,four sedimentary systems are distinguished:carbonate platform depositional system,fortress island sedimentary system,delta sedimentary system and river-lake composite sedimentary system,nine types of sedimentary facies are also distinguished:lagoon facies,platform facies,tidal flat facies,barrier island facies,shallow water delta facies,meandering river are equal.Sedimentary evolution of the study area which is controled by tectonic evolution and sea level change,has transitional characteristics:in SQ1 to SQ3,study area is thecompound island-platform sedimentary system developed in land surface sea environment,the tidal flat-lagoon facies is widely developed,and limited platform phase and barrier island facies is locally developed;SQ4 is an excessive environment,developing shallow water delta facies,in which leading edge subfacies and plain subfacies vertical frequent overlaps,with "great plains,small leading edge" features in space;SQ5 to SQ7 are terrestrial environment,developing meandering river facies,braided river facies and inland littoral lake facies.By comparing the transverse well of the skeleton sandbodies of the research area,the sectional drawing of the sandbodies and the layout of the plane are made up to discribe the distribution of the connective plane of sandbodies in the sequence lattice and shows that the sandbodies is obviously controlled by sedimentary facies.By means of comprehensive analysis of the reservoir physical characteristics of the skeleton sandbodies development layer,combined with the characteristics of sedimentary facies and the characteristics of sandbodies distribution,it is pointed out that the upper Paleozoic in the study area is favorable for sandbodies development.