The Identification On Oil-Water Layer Of Chang9in Wubao-yongning Oil-Field, Ordos Basin

The oil reservoirs of chang9in Wubao-Yongning oil-field is basicly inherited the characteristics of lithologic reservoir with low permeability and low porosity in Ordos Basin. In addition, because of the deeply buried, big changes of reservoir lithology, complicated pore structure, serious property heterogeneity and complicated oil-water layer distribution rule, the "four property relationship" of reservoir, and its logging response characteristics, key parameter study has also become very difficult, going against the effective recognition of oil-water layer. According to the difficult problems with identificating the chang9oil-water layer, the paper starts with the research results by the former people in this area, on the basis of the basic geology, core logging, analysis and assay, logging data and tried-oil and tried-production materials, then studis the chang92and chang91oil reservoirs, referring to the sedimentary facies and sandbody distrubition, reservoir geological characteristics,"four property relationship" of typical wells, and reservoir key parameters characteristic, eventually use the single well logging curves longitudinal comparison, overlapping chart, comprehensive’s analysis of more wells material intersection, and established logging interpretation plate’s formula method to gradually identify the oil-water layer of chang9in research area. The main achievements are made as follows:1. The oil reservoirs of chang9is mainly lakes-delta facies, and oiliness show is mainly occurred in lithology favorable positions, which are often stored in underwater distributary channel sand body of delta front. The area where sandbody is connected distribution is good, and the greater the more thickness, the higher the oil-water yield.2. Chang9oil reservoirs of the study on formation water CaCl2main type and salinity changes range, in addition, local area existences Na2SO4type. General relatively oil are located enrichment region reservoir water salinity is relatively high value on the background value low area, or is high and low salinity alternate area. Reservoir water salinity and high and low resistivity reservoirs overall relationship exists between the reverse.3. Under the premise of the core calibration, the research results on reservoir’s "four property relationship" show that:the area exist conventional and relatively lower resistivity oil layers, conventional and relatively higher resistivity water layers, which leads to the relative relationship of oil-water is complex. Will the natural potential-acoustic time curve, deeply should resistivity-acoustic time curves overlapping according to certain principles, curve range difference between the relative size can reflect the overall reservoir physical property disadvantages, the greater the range difference, the better reservoir physical property, and the oil-water layer liquid producing quantity is high.4. Based on the geological data and the condition of the well logging data, it is difficult to use only one kind of methods to identify fluid properties, so it is "2+4+1" effective steps that could identificate oil-water layer effectively. Namely, it uses the single well longitudinal analysis and two superposed graph methods which could determine fluid properties initially. Then, it adopts the comprehensive analysis with more wells materials, and extracts reservoir key parameters to compile four intersection, in ordor to gradually identify conventional water reservoir, relatively low resistivity oil layers, relatively high resistivity water reservoir. Ultimately, it recognizes fluid properties by quantitatively calculating oiliness saturation that based on litho-electric experiment and single or more wells materials.5, The differences beteewn the reservoir lithology, pore type and structure, property and other aspects of chang9oil reservoir, decided the differences between reservoir property and stronger heterogeneity, then control the reservoir oily characteristics, also control identification standard of chang9oil reservoirs in the different oil-water layer, and the same oiliness region.