(NO309884-B1)   NOVELTY - Monitoring and detecting different phenomena, e.g. local variations in pH, salinity, hydrocarbon composition, temperature, pressure and microorganisms by chemically immobilizing/integrating tracers in the formation or constructions or filters around the wells, and detecting the tracers downstream providing information about the various zones/sections, is new.    USE - For monitoring the hydrocarbon and water production from different production zones/sections in a hydrocarbon reservoir and/or injection wells and detection of different phenomena, e.g. local variations in pH, salinity, hydrocarbon composition, temperature, pressure, microorganisms, and the difference between production of formation and/or injection water from various zones/sections. The method is used in a local alarm system for water breakthrough and is used for oil and gas recovery (IOR) in horizontal production and injection wells.    ADVANTAGE - The invention determines the local and detailed information about the phenomena, using a fluid intelligent and reliable tracer technique together with a relatively simple data detection system, which requires no equipment downhole during production. Thus, the well hole remains unchanged resulting lower pressure drop. Since there is no equipment down-hole, there is no need for equipment maintenance either. The method gives both short time and long time information, which can be used for, e.g. for early warning, start phase detection, or long time monitoring. It also uses no radioactive isotopes, or any material harmful to the environment. It enables measurement of the difference between productions of formation and/or injection water from various zones/sections in a hydrocarbon reservoir.    DETAILED DESCRIPTION - Monitoring the hydrocarbon and water production from different production zones/sections in a hydrocarbon reservoir and/or injection wells and detection of different phenomena, e.g. local variations in pH, salinity, hydrocarbon composition, temperature, pressure, microorganisms, and the difference between production of formation and/or injection water from various zones/sections, includes:    (a) dividing around wells in the reservoir into a number of zones/sections;    (b) injecting or placing specific tracers with unique characteristics for each zone/section into the formation in these regions so that the tracers are placed as integrated parts of the well completion of placed and immobilized in these regions through injection, squeeze or by other techniques, or the tracers can be immobilized or placed on a filter, a casing or constructions surrounding the well in each zone/section;    (c) chemically immobilizing or integrating the tracers in the formation of constructions or filters around the wells; and    (d) detecting the tracers downstream providing information about the various zones/sections.    The tracers are specific or introduced to give specific information from each zone/section. They (tracer carriers) are chemically intelligent and released as a function of specific events.