The Study Of Sequence Stratigraphy And Sedimentary System Of Lower Paleogene Of Fushan Depression Of Northern Gulf Basin

Fushan Depression in the northern Gulf Basin near the southeastern margin of a NEE trending in the Cenozoic rift half graben, south to the Dingan fracture, northwest to the Lingao fracture, east to the Changliu fracture, showed overall depression over the North off the south and east-west graben tectonic pattern.In this paper, the Liushagang of Fushan Depression as research object, sequence stratigraphy and sedimentology, the latest theoretical basis of seismic, well logging and lithology, etc., on the Liushagang for comprehensive study of sequence stratigraphy and sedimentology, aim to clear the sequence stratigraphy framework and temporal evolution of sedimentary systems, to study the different mechanism between the east and west of Fushan Depression. It has important theoretical significance to looking for lithologic.Firstly, based on the core, logging, drilling and seismic data, combined with the analysis of geological and technology of geophysical interpretation, combined with the sequence stratigraphy and sedimentology of basic theory and research methods, to study the development history of construction-sedimentation of Fushan Depression by identifying the sequence boundary characteristics of the drilling, interpretation of seismic layer and the results of well-seismic calibration, established the sequence stratigraphic correlation framework of the Liushagang of Fushan Depression, divided Liushagang into 3 third-order sequences: SQ1, SQ2, SQ3, 4 third-order sequence boundaries: SB1, SB2, SB3, SB4, 3 largest flooding surface: MFS1, MFS2, MFS3.Secondly, based on the establishment of sequence stratigraphic framework, using the logging phase and core information to establish electric-rock template to support and determine the deposition system types of the Liushagang of Fushan Depression: braided delta, fan delta, lacustrine facies and Gravity flow. Through the thickness of sand and the percentage of sandstone, outlined the distribution of deposition system during the each sequence, and studied, analysised, summaried the characteristics of sedimentary system and the changes of distribution of Fushan Depression. Finally, based on the basic research, combined with the structure characteristics and evolution of Fushan Depression, studied and analysised the factors of geological mechanisms ledding to the significantly difference of oil and gas production of the Eastern and Western:(1) The type of fault of Lingao and Changliu fracture are different. Lingao fault is extensional faults, and Changliu fault is a long stream of fault. Under the control of the two faults, the stratigraphic and structural styles of the eastern and western are different;(2) Under the interaction of Lingao fracture, Changliu fracture and Hainan uplift, the deposition center of each sequence of Fushan Depression migrated. The deposition center of SQ1 located at the east of Lingao fracture migrated to the Huachang-Bailian structure of SQ3;(3) The reverse fault closed the reservoirs inner the SQ1 stratigraphic framework, leading to the trap of the eastern SQ1 difficult to form reservoirs.