Logging Interpretation Method for Complex Lithology Reservoirs Using Pore Structure Comprehensive Index (基于孔隙结构综合指标的复杂岩性储层测井解释方法)

Abstract

The complex pore structure influences the seepage and electrical conductivity of the reservoir, and it plays an important role in the identification of reservoir fluid properties and the evaluation of reservoir parameters. There are a variety of lithologies in the Paleogene reservoirs of the Bozhong Sag, including conventional sandstone, dolomite, sandy conglomerate and others. The types of pore spaces in reservoirs are diverse and heterogeneous. As a result of the complex pore structure, fluid identification is difficult and reservoir parameters are calculated with substantial errors. The paper analyzes the pore structure characteristics of reservoirs with different lithologies. Classifying the pore structure and regressing the macroscopic physical parameters against the pore structure parameters, the sensitive parameters of the reservoir pore structure change are identified. The pore structure CI comprehensive index was then constructed, which is consistent with the production capacity. Specifically, this paper proposes a fluid identification correction cross plot that corrects for the effect of pore structure on fluid identification. The method of calculating the permeability of reservoirs with different lithologies can be achieved by using pore structure composite index (CI), and this method has a high degree of accuracy in calculating permeability. Due to the complex pore structure of the reservoir, lithoelectric parameter m varies with the reservoir when using the Archie formula for saturation calculations. In spite of this, it has been found that the pore structure comprehensive index CI is highly correlated with the m value, which leads to the development of a model for the saturation of variable rock electrical parameters. Results indicate that the new model is more accurate in calculating saturation.This paper provides a new approach for logging interpretation of reservoirs with complex lithology and pore structure, which has a positive impact on exploration and development.

Keywords: Logging interpretation method, Complex lithology reservoir, Pore structure comprehensive index, fluid identification