Method for using tracer flowback for estimating influx volumes of fluids from different influx zones

A method of estimating an influx profile for at least one of the well fluids (oil, gas, or water) to a petroleum producing petroleum production well with two or more influx zones or influx locations to a production flow, comprising the following steps:

• arranging tracer sources with distinct tracer materials in known levels near two or more of said influx zones of the well, at least one of said tracer sources arranged downstream and exposed to the fluids in at least one of said influx zones,
• wherein one or more of said tracer sources is arranged in separate corresponding one or more delay chambers, said delay chamber having one or more apertures to the fluid flow in a central pipe,
• each said tracer sources having even release rate to said well fluid,
• inducing a transient in the production rate of the entire production flow, thereby changing the local exposure times of the tracer sources to the fluid for locally accumulating said tracer material near said tracer sources,
• collecting samples by using a sampling device, downstream at known sampling times,
• analysing, by a tracer analyser, said samples for concentration and type of tracer material from said possible tracer sources,
• based on measured concentrations and their sampling sequence and the well geometry, calculating said influx volumes from production well transient flow models,
• wherein after said step of calculating, a model well of said well is established, including a model transport path corresponding to said well's transport path downstream of said influx profile,
• said model well having model influx rates to corresponding model influx locations corresponding to said real influx locations, with model tracer sources with distinct tracer materials in known levels of said model well corresponding to said real tracer sources,
• each said model tracer sources having even model leak rate (diffusion) to a model fluid of said model well,
• whereby model concentration for each tracer material is calculated in said modelled downstream well flow transport path as a function of time under a modelled transient occurring in said model,
• comparing measured concentration and type of tracer material with calculated model concentration for a corresponding model type of tracer material, and adjusting said model influx rates so as for improving the consistency between a model influx profile and said influx profile
• using the calculated influx volumes as parameters for controlling the production flow or for characterizing the reservoir.