The invention is a method for detecting or mapping potential influx zones (z1, z2, z3,...) for gas (g) from a geological formation to a gas well (1) with a well head (b) with a valve tree or a choke (12), comprising the following steps of: - marking (100) the potential influx zones (z1, z2, z3,...) with tracer systems (ts1, ts2, ts3,...) with corresponding unique tracers(tr1 tr2, tr3,...) - filling (200) the gas well form the surface, through the well head (b) with liquid (v) wherein the tracers (tr1, tr2, tr3,...) have affinity (a) to the liquid (v), - producing (300) liquid (v) form the well (1), - consecutively sampling (400) samples (s1, s2, s3,...) from the produced liquid (v), - to analyze (500) the samples (s1, s2, s3,...) to prove possible presence of one or more tracers (tr1, tr2, tr3,...) or even measure the tracers concentrations(cl, c2, c3,...). [for then proving possible influx of a back flow of liquid (v) from the influx zones (z1, z2, z3,...) one assume implies the gas pressure and the inflow of a gas (g) form the influx zones (z1, z2, z3,...)].