Abstract This paper presents a well test interpretation methodology using characteristic points and lines found on the pressure and pressure derivative versus time log–log plot for the characterization of a finite-conductivity fractured vertical hydrocarbon well in a double-porosity (heterogeneous) formation considering a new and practical analytical Laplacian model which require less computational time and have more accuracy than semi-analytical models. Some existing equations are found to work well for the new model, and new expressions are developed. The accuracy of the developed equations is successfully tested with synthetical examples.