A logging evaluation method for shale and calcium-bearing reservoirs based on the effective medium HB resistivity model—a case study on the Sartu Formation and Putaohua Formation West of the Daqing Placanticline

Abstract

In order to solve the problems of low logging interpretation accuracy and fluid identification in shale and calcium-bearing formations in the study area, this paper uses the effective medium theory and electric double layer theory, combined with artificial core technology, to carry out the first quantitative study of the influence of calcareous on rock resistivity, and establishes a conductive model for the evaluation of the oil and gas properties of shale and calcium-bearing formations. First, considering the salt exclusion effect of clay pore water and its dispersion distribution, and an improved Berg model was established. Compared with the original Berg model, the improved Berg model achieved a higher interpretation accuracy. Second, artificial cores with different calcium and clay contents were designed and prepared using artificial core technology. A quantitative formula describing the relationship between the cementation exponent m and the calcium and clay content was established and combined with the improved Berg model to build an effective medium HB resistivity model suitable for shale and calcium-bearing formations. Finally, the hierarchical decomposition crossplot approach was used to identify the calcareous cemented rock layers, then the reservoir parameters were calculated. The new model is applied to the quantitative evaluation of reservoir logging, and the comparison with the oil test results indicates that the new model established in this paper can be applied to the quantitative evaluation of reservoir logging in this area, and the corresponding evaluation techniques provided a good reference for logging interpretation and evaluation in other corresponding areas.