The article discusses researches performed in the Well Drilling Department of the St. Petersburg Mining University. The directions of development of the department are shown. Special attention in this article is paid to research in the field of developing drilling fluids for drilling wells in various mining and geological conditions. It is shown that the gas-liquid mixtures studied by the department will be effective for under balanced drilling under conditions of abnormally low reservoir pressures when using a binary mixture of sodium lauryl sulfate 0.5% + linear sodium alkyl benzene sulfate 0.5% as a surfactant and polyacrylamide FP complex 107 (0.05%) as a forming and stabilizing additive + carboxymethyl starch BUR-2 (1%). Studies in the field of development of inhibitory fluids have shown that an increase in the concentration of polar compounds in the drilling fluid compared to their concentration in the rock Cp> Cn by 0.25 mol/L makes it possible to increase the stability of the rocks around the wellbore compared to the initial conditions. Studies of lubricating additives showed that introducing 1.5-2.0% of FRW additive reduces the friction coefficient of the metal-metal pair in a clay solution by 70-75% and in an aqueous solution up to 65%. The findings suggest that drilling fluids developed at the Well Drilling Department of the St. Petersburg Mining University have a high potential for their application in oil and gas fields in order to improve the efficiency of drilling and completion of wells. It is also noted that the scientific and technical potential of the department allows for input control of reagents in drilling fluids, as well as the development and research of various compositions not only for drilling and completion of wells, but also for development and repair, which are applicable in real field conditions.

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The aim of the work is to increase the well completion efficiency when using oil-based drilling fluids. In this study, the effect of the aqueous phase content on the change in the rheological parameters of the solutions and the effect of the type of asphalt on the structural-rheological and filtration parameters of the oil-based solution was conducted. Studies have shown the effectiveness of various types of asphalt in OBM systems, the obtained dependencies on the effect of the Oil-water ratio can be used in production to select the optimal ratio for the selection of specific properties of solutions.

In this paper water cut of well products problem is considered. To solve this problem it is proposed to use a technology of water inflows isolation during the drilling process developed by the authors. Not only does our approach stimulates the production of hard-to-recover hydrocarbons but it also protects local water and undisturbed geological formations against the impact of hydraulic fracturing operations. This approach also enables higher well potential due to a longer service life of the wellbore. The use of a device-pressure regulator with synchronous injection of the developed blocking fluid is presented. Mathematical modeling of the experiment was performed, aimed at determining the dependence of the change in pressure drop in the annular space of the well on the flow conditions of the blocking composition with a device installed in the bottom hole assembly that will effectively apply the controller device, taking into account the drilling parameters of a particular well. The novelty of this approach lies in the fact that this work offers an aquifer isolation technology, which suggests applying a pressure regulating device, and provides a layout of a blocking viscoelastic system.

Current research on the stability of well walls when drilling in fractured rocks and also when drilling inclined sections of the well profile are based on the assessment of the effect of drilling fluid filtrate. The novelty of this work lies in studying the complex effect of a water-swellable polymer on the stability of well wall, on the one hand, and on the controlled loss of circulation on the other. For preparing rock samples, a method was used based on standard laboratory equipment fordrilling fluid properties. The well wall stability tests are performedon a direct shear apparatus.The WSP composition based on alcohol, ether, and surfactant (Polyecanol Flora) showed its efficiency by increasing the stability coefficient with the engagement of less and more internal friction angle.PHPA-based viscoelastic composition showed the best result by increasing the stability coefficient in the hazardous areas by 50-60%.