The present application concerns a method for monitoring the hydrocarbon and water production from different production zones in a hydrocarbon reservoir and/or injection wells and detection of different phenomena such as e.g. local variations in pH, salinity, hydrocarbon composition, temperature, pressure, microorganisms, and the difference/ratio between production of formation and/or injection water from various zones in a hydrocarbon reservoir. The method comprising dividing regions around wells in the reservoir into a number of sections, and injecting or placing specific tracers with unique characteristics for each section into the formation in these regions. The tracers are chemically immobilized/integrated in the formation or in constructions/filters around the wells, the tracers (tracer carriers) being chemically intelligent and released as a function of specific events. Detecting the tracers downstream provides information about the various zones. The invention may be used as a local alarm system for water breakthrough, or for improved oil and gas recovery (IOR) in horizontal production and injection wells.