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Study On The Characteristics Of Pressure System Of Medium-deep Strata And Its Evolution In Donghing Depression

Posted on:2012-03-22Degree:MasterType:Thesis
Country:ChinaCandidate:X D WangFull Text:PDF
GTID:2210330338993476Subject:Mineral prospecting and exploration
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So as to research the characteristicsof pressure system of medium-deep strata and its evolution and the main controlling factors which cause the overpressure in Dongying Depression, the thesis has developed 4 respects of research, including pressure system division, the top overpressured surface confirming, overpressure quantitative calculation, and paleo-pressure reconstruction, based on previous study and underground data. After the research, the thesis further clarified the characteristics of pressure system of medium-deep strata and its evolution in Dongying Depression, and establishshed the coupling-matching associations between the process of overpressure evolution and the controlling factors which cause the overpressure.The overpressure located mainly in the middle and lower 3rd member and the middle upper 4th member of Shahejie Formation. And the top overpressured surface located mainly in the middle 3rd member of Shahejie Formation (between the seismic reflector T4 and T6). The seal formed by a group of dark gray mudstone, calcareous mudstone and sandy mudstone. Mudstone diagenesis reaches the rapid transformation of the illite-montmorillonite interlayer minerals, and corresponds to the mass outcrop sections of the first and second carbonate minerals.These characteristicss are primarily controlled by both sedimentation and tectonism. On one hand, the lithologic character and sedimentation speed of sediments controlled the distributed horizon of the top overpressured surface. On the other hand, the controlaction of tectonism on the distribution of the top overpressured surface could be divided into two different stages. In the stage of faulting, tectonic movements controlled the formation of overpressured bodies, and in the stage of depression, tectonic movements controlled the current burial depth of the top overpressured surface by controlling differential settlement of formation in two fault walls.The thesis proved that the inside of overpressure system is composed of 3 sections, which are the overpressured seal, overpressured belt and overpressured blowdown belt on the basis of prolific illustrations. According to this, the author inferred that the pressure situation in the lower 4th member of Shahejie Formation and its following formations was mainly weak overpressure to atmospheric pressure. On this basis, and combined with the structural characteristics and the top overpressured surface distribution of the basin, the author established the pressure system distribution pattern of single well and profile in Dongying Depression.Through numerical simulation and thermodynamic modeling of fluid inclusions, the pressure evolution history of medium-deep strata was studied. It is concluded that the overpressure was first developed in the upper 3rd member of Shahejie Formation depositional stage, and the excessive pressure was growing until the late Dongying formation sedimentary period. The excessive pressure was lowering in the period of Dongying Movement due to the uplift and erosion of formations, and it gradually increased again with the deposition in the basin.It is concluded that the formation of seal, the undercompaction, hydrocarbon generation and stratum denudation are the 4 main controlling factors to fluid pressure buildup. Then, the thesis researched the occurrence and development of these factors, and finally established the appropriate coupling-matching associations between these factors and the process of overpressure evolution.
Keywords/Search Tags:Pressure system, Overpressure, Evolution history, Main controlling factors, Medium-deep strata, Dongying Depression
PDF Full Text Request
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