Study On High-resolution Sequence Stratigraphy Correlation And Sedimentary Facies Distribution Of Fuyu Formation, South Zhao Yuan Area

The South Zhaoyuan area of the Songliao Basin, northeastern China, is located between the central sag and the southeast uplift, including the Chaoyanggou terrace and the Changchunling anticlinal belt. The major oil pay zones in this area are formed by fluvial channel sandstones within the first and second layer of the Fuyu Formation. The sequence stratigraphy and sedimentary facies distribution of Fuyu Formation, south Zhaoyuan area,are studied, which are on the basis of sedimentary study and high-resolution sequence stratigraphy theory.Six types of sedimentary micro-facies are recognized based on the core descriptions. Many channel sandstones are interpreted as meandering, based on consistency of thickness, facies successions through the channel sandstones and into the splays and floodplain strata above them, and presence of epsilon mud drapes in several cores. Other thinner channels, usually with more mud partings and a high percentage of ripple lamination in core, are interpreted as anastomosed crevasse channels on the floodplain. In addition to the two types of channel sandstone, we recognize crevasse splay/crevasse channel complexes, floodplain vertical accretion deposits, ponds and lakes.Further more the criteria for recognition of the cores and well logs are setup according to the sedimentary micro facies.In this study of fluvial and floodplain strata, using cores, geophysical logs and 3-D seismic reflection volumes, the Fuyu Formation was divided into three medium-scale base-level cycles and five small-scale cycles, named in stratigraphic order the FII-2, FII-1, FI-3, FI-2, and FI-1. Cycles were recognized by a recurring facies succession motif of channel sandstone→splay/floodplain mudstone→calcic soil.Calcic soils which are thick and laterally pervasive, also the isolated channel sandstones, are developed during a period of basel-level rise and high accommodation. Steno's law was applied to provide consistency in correlations. The characters of the vertical and horizontal distribution of the facies and the facies model of the study area are concluded.On the basis of the studying of the facies distribution and the analysis of the porosity and permeability of the reservoir, the favorable reservoir facies belts are predicated. Both the crevasse channel and the meandering channel sandbodies are the main favorable reservoirs belts in the study area. And the favorable exploration layers are mainly lie in the cycles FII-1, FI-3 and FI-2.