A Method for Reservoir Effectiveness Evaluations of Altered Igneous Reservoirs based on Logging data: A Case Study of the Nanpu Structure in Eastern China.

The igneous reservoirs in China's Nanpu area are characterized by diverse lithology, complex pore structures, and alterations, which has made it very difficult to accurately evaluate the reservoir effectiveness using logging methods. The influence of alteration and the singularity of the interpretation method are the main problems that limit the interpretation accuracy. Therefore, a solution to the problem of logging evaluation of altered igneous reservoirs is proposed in this paper. Firstly, a least square method combined with particle swarm optimization-support vector machine (PSO-SVM) is used to identify the lithology of igneous reservoirs. Secondly, a volume model of altered clay was designed in order to calculate the porosity and other physical parameters of the study formations. Finally, based on such single reservoir effectiveness evaluation methods such as mercury injection, nuclear magnetic T2 spectrum, and Formation MicroScanner Image porosity spectrum, comprehensive evaluation factors were designed for the purpose of analyzing the reservoir effectiveness of the igneous formations in the study area. The combination of multiple evaluation pore structure methods adequately considers the influence of reservoir storage capacity, pore size distribution, and fractures, which effectively improves the evaluation accuracy. The final evaluation results were found to be consistent with the actual production test conclusions, which confirmed that the proposed method of logging evaluation is suitable for the altered igneous reservoirs in the Nanpu area of eastern China. We believe that this approach can be extended to other areas of altered igneous reservoirs. [ABSTRACT FROM AUTHOR]