Oil extraction and well operation at the fields of Urals and Volga River basin, especially mature ones, is complicated by deposits of inorganic salts as a mixture of one or several main inorganic components and corrosion products, sand particles, with deposits impregnated or covered with asphaltene-tarry-paraffin substances. Deposit control methods may be classified into two groups: prevention and removal. The paper embraces the main methods to control asphaltene-tarry-paraffin substances and their effectiveness in relation with conditions of the Upper Prikamye fields. The study is aimed at comprehensive evaluation of effectiveness of a wellhead chemical injection package, a unit of the equipment of metering reagent feed, which is a basic chemical prevention method against complications in well operations at the Upper Prikamye fields. One of the key factors conditioning effectiveness is a precise selection of inhibitors for the specific field. The results obtained show expedience of a wellhead chemical injection package in difficult wells.