A novel heterogeneity analysis method for clastic reservoir through multiscale entropy analysis of logging data: A case study of the Yanchang Formation, Ordos Basin, China

Abstract Heterogeneity is one of the core content of reservoir characterizations for hydrocarbon exploration and development. However, most heterogeneity studies are conducted based on statistical calculations using permeability and porosity data. Although there have been attempts to evaluate heterogeneity by quantifying the complexity of the logging data, these evaluations rarely consider the spatiotemporal multiscale of strata systems, which may lead to an inadequate understanding of multicycle sedimentation and incorrect analysis results. To fill this research gap, in this study, a novel heterogeneity analysis method was developed based on multiscale entropy analysis (MSEA). Using the natural gamma (GR) logging data of the strata, the method can be used to accurately depict the heterogeneity of the formation. Furthermore, based on the geological background and multiple spatiotemporal scales, the relationship between the obtained MSEA values and oil production is presented. To demonstrate the effectiveness of the proposed method, the Chang-8 member in the Yanchang Oilfield was selected as a case study. The results show that a positive correlation exists between the MSEA values of the GR logging data and the heterogeneity. Additionally, there is a significant negative correlation between the MSEA values of the GR logging data and production. For single-wells, the correlation coefficients between the MSEA values and oil production range from −0.64 to −0.95, with an average of −0.76.