Аннотация:When justifying the remediation projects of aquifers from pollution, as a rule, field studies are in preference. In comparison with laboratory experiments, they cover a larger volume of rocks that contain groundwater, and therefore better reflect the average properties of the reservoir. The most important parameter determined in field trials is the porosity. It determines migration velocity of the contamination front and characterizes the amount of pollutants in the reservoir, etc. Depending on the objectives of the study, it can be determined under field conditions in different ways: injection of chemical or thermal indicators, or vice versa pumping or injection–pumping. There are examples of three studies presented below. In the first example, one well-experienced results of injection–pumping of clean water into the contaminated aquifer are presented. As a result, the active porosity of gravel and pebble reservoir with sand filling is equal to 0.15. The data obtained by the experience have been required to support the interception of contaminated flow. The second example shows the results of pumping heated water into the reservoir folded by fractured carbonate sediments (limestones and dolomites). The resulting value of the active porosity is 0.005. Field trial was needed to validate the use of groundwater for cooling of process equipment. The third example is related to the processing of man-made pumping oil. As a result, we obtained porosity of 0.39, residual water saturation of 0.05, and residual oil saturation of 0.25. The need to determine the parameters has been associated with the need to optimize the remediation works.