Abstract: As an unconventional gas reservoir, the reserves assessment of shale gas are affected by both geological characteristics and engineering factors. The estimate ultimate recovery (EUR)of a single producing well in the developed zone is usually directly assessed based on the production decline law. The practices of shale gas exploration and development in North American show that within the same geological zone and under the similar technical conditions of well drilling and completion, the EUR of a single well completed in different years exhibits repeatable statistical distribution, and its cumulative probability curve usually follows lognormal distribution. Therefore, producing wells with long production time and more accurate evaluation results can be selected for analogical analysis, so as to further analyze the statistical distribution law of the single well EUR for the analogous evaluation of the single well EUR in the undeveloped area. In practice, it is necessary to divide the production wells into different plays based on the heterogeneity of the developed zone (P₁₀/P₉₀), taking into account the differences between geological characteristics and engineering factors, aiming to set up the chart of single well EUR probability statistical distribution in different zones and analogically evaluate single well EUR in an undeveloped area adjacent to a producing well when using the similar drilling and completion technology. The value taking methods of single well EUR in the undeveloped zone includes the Swanson method, P^ method, and correction coefficient method. The application conditions of various value taking methods are different, and values should be selected reasonably according to the progress of exploration and development and the degree of understanding, thus providing a reliable basis for project decision.