Study On Hydrocarbon Accumulation In The Southwest Part Of Gudao Oilfield

On the basis of reservoir-forming theories of petroleum geology, using the seismic data, logging data, well core, geochemical analysis and many other methods and techniques synthetically, to conduct systematical research on the faults activity, hydrocarbon migration pathways and the dynamic migration and accumulation in the southwest part of Gudao oilfield from the buried-hills to the upper caps, and established three kinds of reservoir- forming models.Used the structure evolvement as the main research direction, fully used the three dimensional seismic data and structural maps, by combining seismic sections and planes together, and concerning with wholes as well as separated parts, the stages of faults activity, structure evolvement and the holistic evolving characteristics are clarified. Among which the Dongying movement at the evening of Oligocene had positive significance at the early reservoir forming stage because of the increased activity of main faults. While the Neotectonic movement not only formed large number of new small faults in Neocene strata, but also made some old growth faults become active again, so it also had significant contribution on the late reservoir forming process.Starting form the geological background, researched the distribution and migration mechanism of the migration pathways such as the fault, unconformity and sand body etc. detailedly, and fully used many methods such as the oil trace show, characters of the formation water and biomarkers, the migration dynamics to analyzed the favorable migrated and accumulated orientation step by step. The research showed that the configuration of different migration pathways and their time-space effectiveness had distinguished control on the formation and distribution of reservoirs: fault-sand configuration is the main factor which resulted the oil accumulation of research area is mainly from Es3 oil source of Bonan sag and Es1 oil source of Gunan sag. The active intensity of main faults which deeply cutting into oil source beds as well as their fault-plane shape and the seismic pumping effect control the vertical migration of hydrocarbon together. The source of seismic pumping will become the critical accumulation place at the structural active stage because it usually has less residual fluid pressure, and it has very important significance for the research area forming composite hydrocarbon accumulation belt.The research on the geometry, kinematics and dynamics of hydrocarbon accumulation showed that the structural evolvement stage is the essential reason which controlled the dynamic composite accumulation of hydrocarbons: different structural movement generated different structural configuration and migration pathways; different structural movements had different influence on traps formation and development, impel the trap's type changed complicatedly, and so early petroleum pools were adjusted or reconstructed together. Therefore, hydrocarbons migration and accumulation of research area had dynamic linkage characters.According to the intensive research on the plane and profiling distribution of hydrocarbon accumulations, draw the conclusion that different oil-bearing series have different master control factor. Summing up the trap condition control the reservoir-forming of deep buried-hills,unconformity-sand beds control the reservoir- forming of middle Eogene system,faults-transforming sand bodies control the reservoir-forming of the upper Neocene. Established three kinds of reservoir-forming models: fault control reservoir-forming at the first step actic region, consequent stepped fault slope control reservoir-forming at the second step region, and the unconformity control reservoir-forming at Guxi slope region. At last predicted favorable places for the next prospecting.