| Changling sag,located in the south of SongLiao Basin,is a "rich-oil sag",which has entered the exploration phase of lithologic oil reservoir. In order to understand the accumulation characteristics of lithologic oil reservoir, based on the theories of sedimentology ,sequence stratigraphy, high-resolution sequence stratigraphy and reservoir geology, comprehensively using various data such as core,seismic, logging and well logging, porosity and permeability as well as oil-bearing data et.al, the thesis studies the sequence control on reservoir and accumulation of Qingshankou formation in Yaoyingtai Area in Changling Sag.The study result shows that sequence controls the development position of reservoir and types of reservoir facies determine the advantage and disadvantage of reservoir properties and oil-bearing.Based on the the study of core logging, well logging and seismic sequence, the Qingshankou formation high-resolution sequence framework and the correspondence between sequence and sand member as well as oil layer set are built up in Yaoyingtai Area in Changling Sag. The Qingshankou formation is divided into 3 third-order sequence (SQ1～SQ3) and 5 fourth-order sequence (SC1～SC5). It shows that each sequence approximately has the characteristics of "thinning from east to west and north to south",and all sequences completely develop in most areas.Analyzing the characteristics of sedimentary facies in the sequence stratigraphic framework. By means of core and logging curve analyzing, it is pointed out that delta -lacustrine depositional system develops in Qingshankou formation, and the main microfacies are distributary channels, inter-distributary bays,under water distributary channels, underwater interdistributory bays,river mouth bars, sheet sand, distal bars, sandy beach-bars, mixed beaches and muddy beaches. According to sequences thickness, percentage of sandstones and seismic features,it concludes that the provenances of Qingshankou formation are mainly from Tongyu in northwest,Baokang in southwest and Changchun-Huaide in northeast.Meanwhile, combining with the vertical evolution of single well and comparison of connecting-wells,it is confirmed that sedimentary facies in plane in study area are mainly the advance and retreat development of delta in the shallow lake.Through core observation and reservoir properties analysis, it is found out that reservoirs rock is mainly fine-coarse arcose, the sandstones can be compositionally classified as immature and lower structural maturity.The reservoir space is maily influenced by diagenesis such as compaction and pressure solution et.al, which make the reservoir belong to an low-porosity and extra low-permeability reservoir.In macroscopic aspect, the porosity and permeability of river mouth bar and distributary channel are relatively good,and the under water distributary channel and are the second ,and distal bar is the last.Sequence controls the features of reservoir and accumulation.In the sequence framework, the combination of accumulation are mostly self-generation and self-preservation, down-generation and up-preservation from Qingshankou 1 member to Qingshankou 3 member.In the fourth-order sequence,the oil-bearing of the rising half-cycle is better than the falling half-cycle.Specific to the micro-phase, the oil-bearing of mouth bar facies is the best, and distributary channel,underwater distributary channel and beach bar microfacies are the second, and sheet sand facies are the worst.The transition zone between delta frontal subfacies and shallow lake subfacies as well as the transition zone between delta frontal subfacies and delta plain subfacies is enriched with oil and gas in the form of lithologic oil reservoir,which will be as a favorable exploration area. |
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