Currently, during opening and testing of productive formations, as well as during repair work in wells, specialized technical fluids are used on a ater or oil basis. All of them are characterized by compatibility to varying degrees with the lithological and physical properties of reservoirs in Western Siberia and have different effects on the filtration properties of the pore reservoir of reservoirs It is known that when using drilling washing fluids made on fresh water, due to the interaction of the fresh water filtrate with rock cement and some rock-forming minerals, the permeability of the bottom-hole zone changes. The paper presents the results of an experimental study of the effect of drilling washing fluids on terrigenous rocks of one of the fields. The impact on the core of drilling washing fluids, with the exception of FLO-PRO and Nacl, led to some decrease in the permeability of core samples in oil. In the core of terrigenous reservoir, filtering FLO-PRO does not cause a negative result. The of permeability changes with increasing filtration pressure before and after FLO-PRO flow are identical in dynamics. According to the results of the study, it can be concluded that technical fluids FLO-PRO and Invert emulsion mud can be recommended for use as they do not violet the structure of the reservoir space and do not lead to a significant decrease in core permeability of all layers in oil.