Abstract: In order to effectively develop the reservoirs of low porosity and super-low permeability in Daniudi gas field, the underbalanced horizontal well technology drilling is used to the He1 reservoir. Well stability analysis is the key of the technology. Combining with the actual geological conditions of the gas field, the finite element analysis method is used to study the well stability of horizontal wells at He1 reservoir with nitrogen, foam and gassy liquid underbalanced drilling. The results show that case well instability will not occur either in the ?215.9 mm well or in the ?152.4 mm well when applying the three ways of drilling underbalanced horizontal wells. This is entirely consistent with the real drilling situation of DP4 well, DP14 well and DP19 well. The results provide an important theoretical basis for the stability analyisis of underbalanced horizontal wells in the Daniudi gas field.