Fine Reservoir Description Of Wei2 Block

Wei2 block is located on Chi'an structure, Which is positioned in the north slope of Gaoyou sag. This reservoir is a broken nosing structure with shallow oil, low porosity and low-super-low permeability. The geological reserves of Wei2 block is 619 X 104t, with a total area of 2.6km2, Due to the poor property, complex structure and serious heterogeneity, there are many problems during water-flooding. To solve these problems, the thesis studies the reservoir characteristic, such as high-resolution sequence stratigraphy, depositional microfacies, and builds up the 3D reservoir model, which provides ensure for the development adjustment of remaining oil, Using geology, geochemistry, geophysics and analyzed assay datum. Through the research mentioned above, the following results are achieved:(1) High-resolution sequence stratigraphy framework has been built after basal level cycling analysis.3 levels of basal level cycling have been identified in the cores respectively named short term cycle, middle term cycle and long term cycle. This study section includes 1 long term cycle,5 middle term cycles and 20 short term cycles.(2) Two depositional systems are distinguished on the basis of the detailed observation and description of core, combining with the well logging, areal geology and all kinds of analyzed assay datum. Delta front system developed during the E1f1 sedimentary period and shore shallow lake sedimentation system was deposited during the E1f2 sedimentary period.(3) According to the compositive valuation of reservoir property, the porosity and permeability are poor, which are mainly controlled by the depositional microfacies. And the heterogeneity is serious in intrastratal, interformational and plane due to a complex interplay of stratigraphic and diagenetic effects.(4) Clustering analysis was run to classify the reservoir flow units into 4 classes, including P, E, F, G. The P flow unit is the main reservoir in this area, which is to be 70% of all; the E flow unit is relatively less, appeared in some of the near by area of the distributary channel sandstone; just a few of the F and G flow units in this area.(5) Using Petrel2008 software, Adopting multi-information cooperation and stochastic modeling method, the 3D reservoir models including structural model, facies model, porosity model, permeability model and NTG model are built up. The calculated reserves are excellent agreement with the primary reserves, which indicates that the models are of high accuracy.