The binomial productivity equation is a pivotal tool for analyzing data in gas reservoir development

typically resolved using well test data. However

in tight volcanic gas reservoirs

the pressure remains stable and changes slowly

which can lead to challenges during productivity well tests. Specifically

the indication curve generated from measured data may have an intercept less than 0

rendering the equation unsolvable in its standard form

thereby necessitating a correction to the formula. Taking the Well-C2 of tight volcanic gas reservoir as an example

the reason of abnormal indication curve is analyzed. By reviewing and adapting existing equation correction methods

the bottom hole flowing pressure data from the productivity test well is adjusted

leading to the derivation of a new corrected binomial productivity equation. It is applied to the tight volcanic gas well

and the result is more stable than the result of single-point method. It can fully leverage the well test data and provide the basis for the calculation of open flow capacity and the formulation of subsequent development and production plan.