While the accounting rule of the successful efforts method is applied to evaluate oil and gas production projects, positive and negative effects on the values of the projects are produced, and the latter is greater. Hence, the values of projects are under-valued. The evaluation results of a coalbed methane development project reveal that the unconventional projects such as coalbed methane and shale gas development, which are already in an economic critical state, will be delayed because of the dealing method based on the successful-efforts. The problem shall be corrected.