Abstract: Theoretically, the binomial coefficient B does not allow being negative value. But the abnormal situation (B<0) still occurs in practice without consideration of influence of bottom hole liquid loading, causing unable to make in-situ deliverability interpretation and evaluation. The study suggests that for a gas pool with low pressure and low permeability, if ignoring the influence of pre-working system on post-performance, especially under the pressure build-up insufficiency after each working-system operation, productivity curve style of a gas well will be reversed. This theoretical deduction presents recommended equation that not only accords with deliverability regularity, but also represents real productivity of a gas well after correcting curves. The case study with the recommended equation indicates its reliability and applicability to similar gas pools.

Key words: gas well, deliverability equation, binomial coefficient, abnomity