Seismic Facies Study Of Jurassic In Western Sichuan Depression

As we all know, the study of sedimentary facies plays a particularly important role on the extraction of oil and gas. But it is difficult to directly determine its sedimentary environment because stratigraphic buried deep underground. Then this study of seismic facies is important. All seismic wave response to the underground sediment very intuitively, and seismic facies is the sum of the main characteristics of the response of sediments on the seismic section.It reflects the process of evolution of sedimentary body, lithological association, sedimentary characteristics. So not only can be used to divide the seismic facies sedimentary phase as reference, can also be used to verify the correctness of the allocation.Further, the seismic facies analysis, which is based on the division of seismic sequence, makes use of the different feature of seismic parameters to acquire the division of seismic sequence by different phase, and then make a reasonable inference of seismic facies and depositional environment. Therefore, seismic facies is a comprehensive reflection the underground geologic body. We can think that seismic facies is the sum of the main characteristics of the response of sediments on the seismic section. The facies changes will cause some change of physical parameters of seismic reflection wave, therefore, the characteristics of seismic phase can show lithofacies in a certain extent, and thus we put the same seismic sequence and seismic stratigraphic units with similar parameters into the same seismic facies. And the purpose of studying seismic facies is not only to analyze the paleogeography and depositional environment, and to reshape the basin, but also to understand the tectonic history, sedimentation history and to predict the reservoir, the stratigraphic trap and lithologic trap.The West Sichuan depression is located in the northwestern margin of the Yangtze plate and the North China block, adjacent to the Tethys ocean and it is not only a combining site of a few plates but also the most active tectonic activitiese with the most spectacular landscape.The depression is in the west of Longmen mountain Orogenic belt, extending outward to the Songpan Ganzi fold belt.It connected KunLun-Qinling Mountains tectonic belt oblique in the NorthEast, South toEmei, Leshan, southward to the Kang Yunnan meridional structural belt,East to the Kawanaka Takashiki.It is approximately North East extension.The total area is about50000square kilometers. The surface stratum mainly of Quaternary and Cretaceous, followed by deposition of a thick Jurassic,Triassic-Cretaceous strata of late three. It is a typicalMeso Cenozoic Basin.At present,sedimentology and logging geology principle have been used.We have established the markof the single well core section facies,subfacies,microfacies and also maked the use of coring wells core and logging data to establish the lithologic and electric relations, which determined the different facies, sub facies and loggingfacies facies characteristics and rock electric conversion model.In comparison with earthquake by using well profile well, we initially established the basic characteristics of sedimentary facies types of system geometry and seismic facies unit.The study of Western Sichuan Depression seismic facies makes use of the2D seismic profile construction since the last century90’s to2008because construction time interval is large. So that the data is loose by the use of instruments and equipment acquisition, processing and display method. The factors are not consistent,and the seismic profile resolution is low. And the corresponding waveform characteristics is poor, coupled with too long profile and less well.So this study selected only22long section with length of2000km.In this study, we make use of the combination of well and seismic,2dimensional and3dimensional profile comparison,comprehensive seismic,geological,logging, mining and other data,seismic stratigraphy new recognition method.We have a new understanding of the characteristics of petroleum geology in the area:First of all,there are5types of sedimentary facies in the area.Braided River Delta:mainly distributed in the northern area,Js J2q sequence from the small holeWest Yuquan north area in.Alluvial·fan deposition:the main distribution areanorth,southwest of all sequence in addition to the above sequence in addition to the.The river facies:mainly distributed in the southeast area and southern Luodai gas field area.Delta(fan) front sedimentary facies: mainly distributed in the middle area of delta(alluvial fan and fluvial facies)between the areas. Shallow lake facies:mainly distributed in the area south and Midwest regions. Secondly, in addition to the area(Northern alluvial fan braided river delta sand body),in the southern part of the sedimentary facies belt also explain the1591ayer of sand body, the air of a total of21layer with the159layer of sand bodies in combination for the27composite sand body(a total of136layers of sand body).And to search119layer dome shaped body,we combine into8composite dome shaped body, and search45layer channels. Finally, through the above study source area there are6sources. Most of the distribution in the area of North Longmen Mountain foothills front:such as the Xiaoyudong, White Hart field north,Hanwang,Dujiangyan north, Dayi to the northwest, Chengdu South.They belong to sedimentary system in the plane.They overlapped each other with no obvious boundary between each other.