Analysis on development and production law of CBM in Fanzhuang Block of Qinshui Basin

In order to estimate scientifically the development trend and predict reasonably the production of high-rank coalbed methane (CBM) fields, the Fanzhuang block of southern Qinshui basin is chosen as the major objective of study which has been developed for a long time and thus is typical in high rank CBM fields. Based on the theory of "three elements", development units are divided reasonably, and the concept of effective producing reserves is put forward. Using the statistical analysis of thee production data and the numerical simulation technique, we investigated the production law. The results show that the development of Fanzhuang Block has three features. Firstly, for various development units, higher the gas production rate is, shorter the stable production period is and higher the initial decline rate is. Secondly, when the recovery percent reaches about 20% in Fanzhuang Block, the output enters the declining stage while the reserve recovery percent is closely related to the well pattern and spacing. Thirdly, the decline rate of CBM wells which coincides with exponential form is relatively fast in the initial stage, but it that is in accordance with hyperbolic function becomes slow in the later stage.