Sequence Stratigraphic Architecture And Quantitive Simulation Under The Low-angle Normal Fault In The Rifted Basin

The tectonic-sequence-sedimentary response model in continental rift lake basin has been used as a research emphasis, but the research on low-angle normal faults has focused on the genetic mechanism of deposition, under its control the sedimentary sequences development pattern is relatively weak. Deposition through different angle faults under the control of rift basin tectonic-sequence-sedimentary integration research to explore the sag within the high and low-angle normal fault sequence stratigraphic architecture differences, and establish the low-angle normal faults under the control sequence configuration and depositional model, make a guidance to the reservoir prediction and lithologic traps forecast.The Wenchang Formation in Enping Sag has both high and low angle faults control sedimentary sequences filling pattern in the study area. Base on three-dimensional seismic data, this paper makes a quantitative identification of three sequence stratigraphic unit, establishes isochronous stratigraphic framework, determine the type of depositional systems and distribution rule by using seismic phase-seismic attributes, combines with the fault system analysis to determine the internal deposition of the third-order sequence filling characteristics. According to further analog quantitative comparison of the sequence analysis, build a sequence model under the control for low-angle normal faults.The main results obtained in the papers as followings:1) Make a quantitative identify for the seismic sequence stratigraphic units of paleogene Wenchang formation in Enping sag.According to the seismic truncated reflection termination of scale, internal seismic facies and occurrence differences and deposition center migration variation identify internal secondary sequence boundaries and define its properties under no well control conditions in Enping Sag Wenchang formation. On this basis, the application of quantitative identification technology quantitative identify seven third-order sequences, including four in lower Wenchang, three in upper Wenchang.2) explore the typical seismic reflection characteristics and depositional system distribution rules.Establishing the rock electro-physical relationship in the study area, making a analysis and characterization for the typical seismic facies unit combine with seismic attributes determine the sequence of three internal sedimentary system types and their distribution range. Under the control of different angle faults in the sag, there is a big difference between the deposition system, sedimentary facies belts size and shape. Large-scale alluvial fan and fan delta develop in the north of the EP17sag, and the tongue to bird-foot braided river delta and beach bar deposition develop in the southern part, the EP18sag northern development is the point-like alluvial and nearshore subaqueous fan, and the tongue braided river delta develop in the southern part.3) Make a clear understanding for the different angle faults under the control of various stages of deposition-sequence filling characteristicsThe Fl (low-angle normal fault) control sag fault develop in the Wenchang formation, has the property of tension-shear. It combines with the F2(high-angle normal fault) fault systems control the structure of the study area, in the ancient warm and humid climate, combine with the provenance differences between the north and south sides, further affect the depositional system space allocation. The low-angle normal fault under the control of the northern source is relatively rich mud, supply alluvial fan-fan delta deposition along the cross-section channel. The north side of geological eroded sedimentary are transported through high-angle normal fault system to the secondary faults intersection. It mainly develops alluvial fan-nearshore subaqueous fan deposits. Its supplying ability is less than the low-angle normal fault interrupt controller side as a whole. Based on the tectonic subsidence and balance restore, divide the deposition-Sequence evolution into two episodes. The rift Ⅰ episode develop vertical settlement, the southern ramp develops regulatory tilting, rotating, and deflection sequence. Under the control of the low-angle normal fault, the fan delta (alluvial fan)-turbidite-deep lake-the tongue braided river delta sedimentary systems are developed. Under the control of the high-angle normal fault, the point-like nearshore subaqueous fan (alluvial fan)-deep lake-the tongue braided river delta sedimentary systems are developed. The rift Ⅱ episode, under the control of the low-angle normal fault, the slope deposits are formed, fan delta-deep lake-the front slump-bird-foot braided river delta depositional systems are developed. Under the control of the high-angle normal fault, deposition system developed successively.4) Quantitative construct a sequence stratigraphic architecture under the control of low-angle normal faults.Based on sequence simulation, build the quantitative sequence stratigraphic architecture under the control of low-angle normal faults, mainly to the horizontal slip on the tectonic subsidence. The provenance contains high clay contents, along with the relatively abundant sediment supply. With the strong synsedimentary fracture settlement, it forms relatively non-compensatory. Under the condition that depocenter migrates greatly to the opposite direction of the dip of fault, the vertical sequence cycle from base to top can be appeared the combination of break point with type L, deep sag with type T and slope zone with type H. The fault block tilted synsedimentary deflection slope break type model are developed in the late Wenchang age. The north and south sides of the sequence are presented as the synchronized stacking patterns. The deposition slope break type models are developed in the early Wenchang age. Both sides of the sequence are non-synchronous overlap, the north continues to retrogradation overlay.