Research On High Resolution Sequence Stratigraphy And Microfacies In Shallow Water Delta

Under the guidance of the theory of high resolution sequence stratigraphy and fully integrating the principles of sedimentology,the accurate identification of different gradation base level cycles of high resolution sequence stratigraphy in the eastern Xing six block of Daqing Oilfield and the fine division of high resolution sequence stratigraphy has been carried out at the same time.On this basis,a high resolution sequence stratigraphic framework conforming to the actual geological development characteristics of the study block is finally established,with the fine depiction of the distribution of sedimentary microfacies in the sequence stratigraphic framework and the contact characteristics between different types of sand bodies,further geographically,the evolution of the short-term sequence of the internal short sequence of the grapevine oil layer in the study block.And finally set up a sedimentary model that can objectively reflect the characteristics of the development of the actual depositional system in the study block;furthermore,it provides a powerful guide for the distribution of various types of oil and gas reservoirs in the study block,at the same time,it also provides an effective geological basis for further exploitation of potential and scientific deployment in the late stage of high High aquifer block.Taking into account the evolution process of palaeo-geomorphology,the evolution law of paleo-structure,paleoclimate evolution process and the influence of these sedimentary backgrounds on sediment supply during the period of Putaohua reservoir in the study block,based on the lithologic and electric data of 530 wells in study block,such as core,well log and drilling,combined with the interpretation of 3D seismic data,fine high-resolution sequence stratigraphy was carried out in the eastern Xing six region Putaohua oil layer.On the basis of the top and bottom interfaces of the oil layer,the sedimentary characteristics of the maximum flood surface are the transition positions from the rise to the decline,hierarchical base level cycles are recognized in reference to two long-term base level cycles(LSC1~LSC2),5 middle-term base level cycles(MSC1~MSC5)and 36 short-term base level cycles(SSC1~SSC36)according to base level cycle theory.Two types of short-term base level cycles,which are vertically stacked in the study block and thus form medium-term base level cycles,are mainly included:(1)Asymmetrical form of upward "darkened",mainly developed in the river controlled shallow water delta plain area;(2)Asymmetrical form of upward "shallow",main development in the far shore area of the river controlled shallow water delta front subfacies with far distance from the source.On the basis of division and comparison of different levels of base level cycles in high resolution sequence stratigraphy,finally,the high resolution sequence stratigraphy of the grapevine oil layer was established.The sedimentary systems and the sedimentary facies of the Putaohua oil reservoir in the eastern part of Xing six block is complex.The main development of long term base level cycle LSC1 is subaqueous sedimentary environment of delta front,mat shaped sand bodies and sand bodies of the estuarine dam mainly developed with strip distribution;on the other hand,the long-term base level cycle LSC2 is mainly delta distributary plain terrestrial deposit,such as large scale channel sand bodies and large overflow river sand bodies,and making the Putaohua oil layer the key to the main production layer.Research results based on predecessors,aimed at the vertical development characteristics of the Putaohua oil layer,summed up 4 unique characteristics of the evolution of the law:(1)The boundary line with the subfacies goes along with the fluctuation of the lake shore line;(2)Relatively stable sedimentary environment in the early and middle stages,but the later changes are fast;(3)High oscillation of main body water system and high frequency energy fluctuation;(4)Different types of microphase development position and its combination law.The stacked forms and forms of contact in space based on the different types of different types of sedimentary bodies,accordingly,the sedimentary model of the study block can be summed up as this 3 kinds:(1)Sedimentary model of shallow water delta distributary plain by rivers;(2)Terminal deposition model of underwater distributary channel in shallow water delta;(3)Shallow water delta front margin deposition model.The distributary plain sedimentary model is in the dominant position in the Putaohua oil layer of the eastern part of Xing six region.