Research On High-resolution Sequence Stratigraphy And Sand Body Sedimentary Facies Of The First Member Of Shaximiao Formation In Longgang Area

Guided by the theories of sedimentology,logging geology,seismic stratigraphy,and high-resolution sequence stratigraphy and grasp previous research results with making an in-depth excavation and analysis of the basic geological data of the first part of Shaximiao group in Longgang area in the middle of Sichuan basin and comprehensively combining the data of core,logging and earthquake,the characteristics of sequence stratigraphy and the sedimentary facies of sand bodies are being discussed in detail in this paper.And relying on this research results,the distribution and evolution law of sand body of the first part of Shaximiao group can be analyzed further.First of all,the author did the research on sequence stratigraphy of the research area by using core,logging,seismic datas under the theory of high-resolution sequence stratigraphy.Different levels of sub-base level cycles and flooding surface are being recognized,this stratum can be divided into 2 long-term base level cycle sequence(LSC1-LSC2),4 medium-term base level cycle sequence(MSC1-MSC4)and 11 short-term datum cyclic sequence(SSC1-SSCll).After that,the high-precision sequence stratigraphic framework that taking the long-term base level cycle sequence as the skeleton,the medium-term base level cycle sequence as the lattice frame,and the short-term base level cycle sequence as the comparison unit was been created and internal structure characteristics as well as the evolution rule of vertical and horizontal upward of each the short-term base level cycle sequence are being discussed.Furthermore,the author have done some analysis of facies marker,and sedimentary microfacies of 79 wells are being divided in the research area with thinking about the core section of a total of 167.17m in the 7 core wells and the regional geological background as well as drilling data.Research results show that this stratum developed the sedimentary model of alluvial fan-delta from and it is considered that the member 1 of Shaximiao Formation mainly develop delta of the curvature River delta front sub-facies deposition,the second is the pre-Delta subfacies.It's clear that the alternating changes of the sedimentary evolution of delta front-pro-delta-delta from the vertical direction.There are some Sedimentary micro-phase such as underwater distributary channel?mouth bar?distal bar?sheet sand?interdistributary?Pre-delta mud and so on,among which the first 4 sedimentary microfacies could be found form the sand bodies.Being taken the short-term datum cyclic sequence as comparison unit,the comparison of the sand bodies sedimentary facies are carried out at the inside of the high resolution sequence stratigraphy frame that has been built at early time and the different short-term base level cycle sedimentary microfacies map was been made with taking the maps of sand ratio and sandstone thickness into account as well as the plane distribution characteristics and the space-time evolution law of sand bodies sedimentary facies are being described carefully in vertical and horizontal with sequence-sedimentary microfacies distribution diagram.After making about sequence stratigraphy and sand bodies sedimentary facies studying,the distribution of the favorable areas are being pointed out and provided the particular basic geological data for progressive rolling exploiting and developing the tight oil and gas of Jurassic stratum with considering the indexes such as sequence stratigraphy?sedimentary facies and the sand bodies distribution?structure conditions as well as the production performance.