Reservoir Architecture Research On Deep-water Gravity Flow Deposition In Shishen 100 Area,Dongying Depression

The deep-water gravity flow reservoirs in rifted lacustrine basins have preferable value for exploration and development.Although significant progress has been made in the research on the macroscopic distribution of such sandbodies,the reservoir architecture is still insufficient.The poor understanding of the superimposed relationship and connectivity among sandbodies has affected the efficient development of such oilfields.Therefore,this thesis takes the example of the 1^st and 2^nd sand formations of the middle submember of Shahejie3 formation(the 3^rd member of the Shahejie formation)in the Shishen 100 area of Dongying Depression,Bohai Bay basin.Based on core,well logging,seismic,and production dynamic data,a precise iso-chronological stratigraphic framework is established for the study area to clarify the sedimentary microfacies types and characteristics.The study clarifies the architecture characteristics of single sandbodies in the study area and the controlling factors of the reservoir architecture.The conclusions are as follows:（1）The sublacustrine fan with supplying channels are developed in the study area,including seven sedimentary microfacies:main channel,branch channel,channel overflow,lobe body,lobe fringe,slump and deep lacustrine to semi-deep lacustrine mud.（2）Two distribution patterns of architectural units are developed in the study area:channel to fan-shaped lobes and channel to finger-shaped lobes.For the channel to fan-shaped lobes,the connectivity between lobes is strong,and the main bodies are often laterally stacking or side-joint.The width of a single fan-shaped lobe is 360–1290 m,and the thickness is 4–10 m.The channel to finger-shaped lobes extend farther.For this pattern,the lobes are relatively isolated with weak connectivity,and they are often laterally stacking or side-joint at the lateral margin.The width of a single finger-shaped lobe is 170–1170 m,and the thickness is 3–13 m.（3）The reservoir architecture of the sublacustrine fan in the study area is mainly controlled by paleogeomorphology prior to deposition and base-level cycles.The macro-distribution and composite pattern of sandbodies are controlled by paleogeomorphology.The scale of architectural units is controlled by base-level cycles.The sublacustrine fan is developed at the low terrain areas formed by faults and uplifts.In the gentle slope zones,it mostly forms finger-shaped lobes.In the steep slope zones,it mostly forms continuous fan-shaped lobes.With the decrease of the base level,sediment supply is increased,the scale of channels and lobes become larger,and it is easier to form slump disposition.