Development of nonconventional resources of natural gas such as coalbed methane (CBM) demands new approaches to reserves’ calculation and economic estimation of coalbed methane fields. Experts of OS «Gazprom promgaz» have developed the method of CBM reserves calculation as independent mineral based on international and russian experience in CBM fields prospecting and production activity of CBM. The article is devoted to basic principles of new technique on an example of Taldinskoe CBM field reserves’ calculation.