Abstract: To address the problem such as the complex bedrock lithology, dense reservoirs, fracture development, low calculation accuracy of reservoir parameter and difficult evaluation of reservoir effectiveness in the northern Songliao Basin, a new three-dimensional lithology identification method of "original rock+composition+structure" was proposed; the effective porosity model for variable skeletal density based on M and N was established by calculating the slope M using the acoustic-density rendezvous plot and the slope N using the neutron-density rendezvous plot; the gas saturation model of fracture-containing reservoir was established by studying the conductivity mechanism of bedrock and correcting the additional conductivity of fractures; the effective thickness standard of bedrock reservoir and the classification standard of effective reservoir were determined by considering the effective porosity, secondary porosity and the degree of fracture development. The application results show that the lithologic interpretation compliance rate of this set of technology can reach 87.5%, the gas-bearing formation identification compliance rate reaches 88.5%, and the calculation accuracy of porosity and saturation meets the requirements of the reservoir specification. The study results can provide technical guarantee for the geological exploration and reserve evaluation of bedrock reservoirs in the northern Songliao Basin.

Key words: bedrock reservoir, reservoir effectiveness evaluation, lithology identification, effective porosity, gas saturation, reservoir classification, Songliao Basin