Research On Sequence Stratigraphy And System Tracts In Key Sequences, West Depression Of Liaohe Offshore Area

Liaohe offshore area is part of Liaohe Depression, which is located in the join of sea and land, and the west of area is focused in this paper. The structure of study area is similar with Liaohe Depression on the whole, which is characterized with faulted depression in the early state and subsidence depression in the late state. However, because of exist of Huludao and Bijialing buried hills, its structure is relatively more complex.Under the instruction of classic sequence stratigraphy and high resolution sequence stratigraphy, based on the data of drilling, well logging and 3D seismic, fourteen sequence boundaries in the study area are defined in Shahejie Formation, Dongying Formation and Guantao Formation. After integrated analysis of well and seismic data, thirteen three-order sequences (SQ1-SQ13) are defined and 3D chrono-stratigraphic framework is finally established.Within the sequence framework, system tract characters are discussed, especially in the key sequences (SQ2-SQ7). And pay much attention to the Low Stand Tract (LST), which refers to the formation mechanism, distribution domain and evolution process, then find the relationship between LST and reservoirs which have been found.LST is characteristic with sand and conglomerate deposition, which is mostly made up of two or three up-coarse prograde parasequences and an aggradational parasequence.It is usually a mud-sand transition across the top of LST in the corn, which is respondent to the change of sediment base level. In the well logging profile, it is a sharp contact at the bottom in SP, GR and RT. In the seismic profile, it is usually characteristic with flank and disorder reflection, and the top onlap a sequence boundary, and terminates on the slope belt.The distribution of low stand tract is controlled by flexured slop break belt and faulted slope break belt in east and west respectively, and LST is absence locally in central out. It is characteristic with slop controlling the boundary and compartmentation by buried hills. From south to north in the study area, there are 4 different developing styles in all.In the period of LST sediments, there are a lot of sand types which are good for reservoir. Especially in the northeast of Huludao and the area of Yudong structure, all kinds of fan sediments which are bounded by...