The principle of construction of stochastic and deterministic mathematical models for prediction of operating modes of gas pumping units at compressor stations of main gas pipelines and their optimization in conditions of incomplete loading of the gas transmission system is proposed. Calculation of the parameters of the technological mode of operation of the compressor stations of gas pumping units is based on the use of combined characteristics of centrifugal superchargers, the processing of which by means of mathematical statistics allowed to obtain analytical expressions for the characteristics models. The calculation method can be implemented for forecasting the operation modes of the compressor station in conditions of both single-stage and multi-stage compression of gas. The source data for the calculation comprise the upstream and downstream pressure and temperature of gas, the volume of pumping and physical properties of the gas. In order to predict operating modes of compressor stations, the optimal distribution of load between workshops equipped with multi-type gas-pumping units is carried out provided that the energy consumption is reduced to compress the given volume of gas under known boundary conditions. The principle of constructing an optimality criterion for conditions of incomplete loading of the gas transmission system is shown. To illustrate the proposed method of optimizing the operation modes of compressor stations under incomplete loading, we give an example of the calculation of optimal operating modes of a hypothetical two-seater compressor station with various types of aggregates. The calculation is based on the construction of analytical mathematical models of their characteristics on the criterion of minimum capacity for gas compression at a given output and upstream and down stream pressures at the station.

Insufficient energy performance of ejection equipment and a high probability of non-operating modes of its operation reduce the efficiency of downhole jet pumps. The method of determining the design and operating parameters of the well ejection system, which provide the maximum efficiency of the jet pump, is presented.  The proposed algorithm for determining the optimal values of the geometric dimensions of the flowing part of the jet pump involves the construction of a series of pressure characteristics for different values of its geometric parameter, the calculation of the efficiency and the determination of the injection ratio and the relative pressure corresponding to its maximum values.  During the studies, the main geometric parameter of the jet pump varied in the range from 2 to 6, given that these geometric dimensions are used in jet devices common in the oil industry. The optimal dimensions of the current part of the jet pump are obtained in the process of studying its pressure characteristics, and the optimal dimensions of the washing system of the bit - in the process of studying the characteristics of the hydraulic system. The design of an at-bit ejection system, which allows to increase the mechanical drilling speed, the passage of the bit, to stabilize the moment on the bit, to reduce its level of vibration and to control the antiaircraft angles of the well is considered. The efficiency of using at-bit jet pumps is in the following: an increase in the mechanical drilling speed up to 18.7%, the passage of the bit up to 50.8%. The research established the optimal diameters of the working nozzle, mixing chamber and bit nozzles, the distance between the working nozzle and the mixing chamber, the injection ratio and the relative pressure of the at-bit jet pump. The obtained values ​​of design and mode parameters exclude the occurrence of cavitation modes of operation of the ejection system and allow the operation of jet pumps with maximum efficiency.

Directional drilling of complementary holes in a cased well is an effective method of restoring decommissioned, emergency and abandoned wells. It enables the possibility to save on drilling new oil and gas wells. Today, sidetracking is considered to be the most efficient technology which makes use of milling casing window. Cutting into the column wall is a very important process. The milling cutter makes a slot-like hole in it due to the force response of the wedge deflection device in the casing. The upper part of the hole becomes elliptical with a smooth contour due to the small angle of the wedge during the axial moving of the tool. At the same time, the lower edge of the hole is straight and forms right angles with its side edges.  The vertices of these angles create a stress concentration in the wall, weakened by the hole, under the condition that a significant tensile force of its own weight acts on the casing. These stresses reach their maximum values in those pipe cross-sections where the window width becomes maximum (design), and their area is the smallest one. The topicality and novelty of the solved problem lie in studying the stress-deformed state of the casing pipe under tension while cutting a window, close to a rectangular shape, in its wall, as well as in calculating the maximum stresses that arise around the right angles of the hole. These solutions make it possible to specify stress concentration factors depending on the geometrical parameters of the hole, and thereby ensure the development of engineering methods for designing a trouble-free process for window cutting in casing pipes. The operating results are as follows: a developed mathematical model of a nonaxisymmetric stress state that occurs during tension-compression of a cylindrical shell with rectangular holes, for which the analytical methods of calculating the stress-strain state of non-thin shells with non-canonical stress concentrators have been used, and theoretical and experimental studies of the stress concentration in the walls of this shell.

On the basis of the analysis of the existing criteria of hydraulic similarity, the rules of transferring the results of laboratory tests of jet pumps to the conditions of their operation in the well are considered.  The geometric similarity of the flow part of the jet pump is determined by the diameters of the working nozzle, the mixing chamber and the diffuser, the lengths of the mixing chamber and the diffuser, and the distance between the working nozzle and the mixing chamber.  The kinematic similarity of mixed flows is determined by the ratio of the speeds or costs of the injected and the workflows, and the dynamic one by the relative pressure in the form of the pressure ratio of the mixed, injected and workflows.  To characterize the similarity of motion modes and physical properties of flows in the flowing portion of a jet pump, a Reynolds number for working, injected, and mixed flows can be used.  The functional relationship between the quantities that characterize the process of mixing threads can be represented as a relationship between the similarity criteria that are made of them.  The equality of any two relevant similarity criteria made up of the basic parameters and initial boundary conditions is a sufficient sign of the similarity of the two systems.  A generalized Eulerian criterion is proposed for modeling a wellbore jet pump workflow that provides a relationship between geometric, kinematic, and dynamic dimensionless complexes.  Due to the structural features of the ejection systems, the generalized criterion is presented in the form of a ratio of Euler criteria of mixed and working flows, the numerical values of which do not differ from the magnitude of the relative pressure of the jet pump.  As a result of the conducted researches, the values ​​of dimensionless complexes are determined, which determine the conditions for transferring the results of experimental studies of the jet pump model to the real design of the well ejection system.

The problem of monitoring and preventing deposit inundation is becoming increasingly important in Ukraine. The solution to this problem is one of the ways to ensure the energy independence of the state. The operation of producing wells is complicated by the accumulation of liquid at the bottom. Subsequently, it leads to premature shutdown of the wells. Inundation determines the need to isolate the influx of formation water. Considering the significant residual reserves of gas trapped in water, it is important to improve existing technologies and to develop new ones for the development of depleted fields under the conditions of dynamic water drive in order to ensure maximum hydrocarbon recovery rates. This paper summarizes domestic and foreign field development technologies under water pressure conditions and analyzes the main disadvantages and advantages of the existing methods of stimulating hydrocarbon inflows in waterlogged gas and gas condensate wells. The main factors that determine the causes and nature of flooding of productive formations and ways to prevent them are analyzed. Based on the results of the analysis of laboratory and experimental studies, the  behavior of gas trapped by brine water has been established.But the issue of determining the localization of residual reserves has not been studied sufficiently. Considering the above mentioned ideas, the author asserts the necessity to and to use geological and technological models constantly. It ensures better extraction of the residual gas from depleted fields under the condition of intensive advance of reservoir water into productive formations. In the case of adapting the three-dimensional model to the actual data of the production history and the simulation of  the exact breakthrough of produced water in production wells, there comes the possible to determine the most promising zones and sections of the field, the reservoirs of which are characterized by the best filtration-capacitive properties and significant gas reserves. The use of a constantly operating geological and technological model of the field will make it possible to develop ways of extracting the residual gas reserves trapped in produced water, to improve existing production technologies and to  ensure maximum recovery factors.