Large difference in productivity and unbalanced development of OGIP（original gas in place） are common issues during CBM production. Based on the production history of south Yanchuan coalbed methane reservoir and A-PDA（advanced production data analysis） method

numerical simulation is employed to study the depressuring degree and the distribution of residual gas as well as the development potential considering the sorption and matrix shrinkage effects. The results show that the 300 m×350 m rectangular well pattern cannot effectively utilize the reserves of CBM

and there is a great difference in the recovery degree o

f OGIP horizontally. The recovery degree in the northwest is low

and the average drainage radius is only 78 m

which is lower than that in the southeast. Through the mathematical model analysis

the residual gas in place in the northwest parts with the area of 2.8 km

2

reached 2.53×10

8

m

3

but the recovery degree is only 4.2 %. From the perspective of influencing factors

the typical remaining gas in the study area are mainly undeveloped well control type and imperfect well pattern type. Infilling well pattern or repeated fracturing can be used for undeveloped well control type

the former can make a raise in recovery degree by 9.6 % according to the numerical model

while for the latter

the well pattern needs to be further improved to promote area pressure reduction. The research provides a guild-line for adjustment disposition and measures.