Structural And Sedimentary Evolution Of Funing Formation In West Slop Of Jinhu Sag

Based on theories of structural geology, sedimentology and petroleum geology, combining previous research achievements, using lots of the information of core hole, seismic data, well-logging data and methods with combining together qualitative analysis and quantitative calculation, geological and geophysical, structural study, sedimentary analysis and hydrocarbon accumulation, fault system, structural evolution, sedimentary systems and reservoir characteristics of Funing Formation in the western slope of Jinhu sag are systematically researched, and the relationships of structures, sediments and hydrocarbon accumulation and favorable oil-bearing areas are analyzed.According to both structural evolution sections characteristics and quantitative analysis of fault activity intensity, it is held that the structural evolution of Funing Formation in the west slope area in the Cenozoic Era can be divided into four periods: Funing period-slope growth, Dainan and Sanduo period-different subsidence, the end of Sanduo period-thrust-fold and Neogene and Quaternary-structures stable.Through the structural stress field numerical simulation of Funing period in the western slop of Jinhu sag, regularities of fault development in ancient structural stress field are analyzed in detail. The results show that the maximum principal stress of Funing period in the west slope area is compressive stress with two low value areas in the southwest and the northwest and high value area in the middle. The minimum principal stress is almost tensile stress with high value area in the southwest with dense faults. The shear stress distribution is regional. The levorotatory shear stress distributional areas are in the middle and the northeast with development of the near east-west faults, and the dextrorotatory shear stress distributional areas are in the southwest and the northwest with development of the north-east and north-northeast faults.North-northwest fault systems and the development of anticline related to fault in the study area are identified by comprehensively using the conventional three-dimensional seismic interpretation techniques and the ant-tracking fracture systems automatic analysis technology. Combined with the analysis of structural evolution section and regional tectonic background, it is considered that the Cui2 thrust fault and of anticline related to fault in its upper wall formed in the tectonic reversal period of the end of Sanduo period.On the basis of core observation, well logging data analysis and stratigraphic classification and correlation, individual well profiles, cross well profiles and planes of sedimentary facies sedimentary are reseached. The results show that there has two sedimentary sources of Zhangbaling upheaval and Jianhu upheaval. Delta front sub-facies are main facies in the upper of the first Member of Funing Formation (Fu-1), coastal and shallow lake sub-facies are main facies of Fu-2, and there are most delta front sub-facies in Fu-3 and lake facies in Fu-4.Based on the research of structural evolution, fault activity intensity and sedimentary facies, combining with regional tectonic background, the controlling effects of structures on sediments were analyzed. It is considered that the slope topography and the intensive active east boundary fault confine distribution of stratigraphic thickness of Funing Formation as wedge-shaped sediment from northwest to southeast. The location of the sand into the lake in the long axis is controlled by the middle structural transfer zone in, the west Jianhu upheaval, and the location of the short axis of the lake is controlled by the slope topography, the southwest Zhangbaling upheaval and intensive active area with faults, The modes of the control of the en-echelon fault and the forked fault on the sand, the control of the faulty-step on the sand, and the control of the horst, the faulty-step of the reverse fault and the middle slop zone on the beach dam of carbonate rock can be established.Combining the studies on structural and sedimentary characteristics with analysis of reservoir characteristics and hydrocarbon accumulation conditions, it is summarized that sandstone reservoirs in Funing Formation are mainly in the Fu-1, the low part of Fu-2, Fu-3 and the bottom of Fu-4, with the area developing subaqueous distributary channel, estuary dam, distal dam of delta front sub-facies, and sand dam of coastal and shallow lake sub-facies. Carbonate reservoir is in the middle of Fu-2 with the beach dam of carbonate rock dam of coastal and shallow lake sub-facies. Reservoirs with permeability are the lateral migration pathway of hydrocarbon, and active faults are vertical migration pathway of hydrocarbon. Anticlines related to fault cut half ringing the sag in the slop are the favorable complex faulted traps group blocks.