Scientific and technological progress over the last century has led to an enormous increase in the consumption of minerals, including energy resources. Most of the exploited oil and gas fields are already considerably depleted, so it is necessary to search for new hydrocarbon resources, particularly at great depths. Deep drilling plays a special role in solving this problem. The article considers the world and Russian experience of ultra-deep wells drilling. The methods and technologies used in the construction of wells, as well as complications and accidents occurring during their drilling were analyzed. The analysis revealed that the existing limitations for drilling parameters of deep and ultra-deep wells are caused by the technical characteristics of surface and bottomhole drilling equipment, which do not meet the extreme drilling conditions. The directions for development of deep and ultra-deep well drilling machinery and technologies are suggested. The notion of extreme rock and geological drilling conditions is introduced, which describes drilling in conditions of hydrostatic pressure of flushing fluid column and high bottomhole temperature both at stable and unstable wellbore conditions, coming close to the upper limit of operating technical characteristics of bottomhole assembly, the drill string and flushing fluid.
The importance of hydrocarbon resources and the oil and gas industry is currently difficult to overestimate. About one third of the world’s natural gas reserves are concentrated on the territory of the Russian Federation; in terms of oil reserves Russia is second only to five states, but even this is enough to develop and improve this branch of production. The Strategy for the Development of the Mineral Resource Base of the Russian Federation until 2035 outlines promising directions for economic modernization. They include rational use of the created mineral resource base by means of engaging hard-to-recover oil and gas reserves and undeveloped solid mineral deposits, reducing the negative impact of subsoil development on the environment, qualitative improvement of the information support system for subsoil use, monitoring and control over the development of the mineral resource base of the Russian Federation by developing information technologies. This requires, among other things, introduction of automated management and regulation systems in the field of geology and subsoil use, as well as systems for processing, interpretation, storage and provision of geological data to subsoil users.
The paper presents the results of investigations on the influence of low bottomhole temperatures in the intervals of productive formations on the technological properties of solutions used for drilling and completion of wells in order to determine the possibility of increasing gas recovery coefficient at the field of the “Sila Sibiri” gas pipeline. The analysis of technological measures determining the quality of the productive horizon drilling-in was carried out. It was found out that the dispersion of bridging agent in the composition of the hydrocarbon-based drilling mud selected from the existing methods does not have significant influence on the change in the depth of filtrate penetration into the formation in conditions of low bottomhole temperatures. The main reason for the decrease in the near-bottomhole zone permeability was found out – the increase in plastic viscosity of the dispersion medium of the hydrocarbon-based drilling mud under the influence of low bottomhole temperatures. A destructor solution for efficient wellbore cleaning from hydrocarbon-based solution components in conditions of low bottomhole temperatures was developed. The paper presents the results of laboratory investigations of hydrocarbon-based drilling mud and the developed destructor solution, as well as its pilot field tests. The mechanism of interaction between the destructor solution and the filter cake of the hydrocarbon-based drilling mud ensuring the reduction of the skin factor in the conditions of the geological and hydrodynamic structure of Botuobinsky, Khamakinsky and Talakhsky horizons of the Chayandinskoye oil and gas condensate field has been scientifically substantiated.
Article provides a brief overview of the complications arising during the construction of oil and gas wells in conditions of abnormally high and abnormally low formation pressures. Technological properties of the solutions used to eliminate emergency situations when drilling wells in the intervals of catastrophic absorption and influx of formation fluid have been investigated. A technology for isolating water influx in intervals of excess formation pressure has been developed. The technology is based on the use of a special device that provides control of the hydrodynamic pressure in the annular space of the well. An experiment was carried out to determine the injection time of a viscoelastic system depending on its rheology, rock properties and technological parameters of the isolation process. A mathematical model based on the use of a special device is presented. The model allows determining the penetration depth of a viscoelastic system to block water-bearing horizons to prevent interformation crossflows and water breakthrough into production wells.
Modern trends in the global energy market linked to the Sustainable Development Goals often lead to the adoption of political decisions with little basis in fact. Stepping up the development of renewable energy sources is an economically questionable but necessary step in terms of its social and ecological effects. However, subsequent development of hydrogen infrastructure is, at the very least, a dangerous initiative. In connection with mentioned above, an attempt to examine hydrogen by conducting an integral assessment of its characteristics has been made in this article. As a result of the research conducted, the following conclusions concerning the potential of the widespread implementation of hydrogen in the power generation sector have been made: as a chemical element, it harms steel structures, which significantly impedes the selection of suitable materials; its physical and volume characteristics decrease the general efficiency of the energy system compared to similar hydrocarbon solutions; the hydrogen economy does not have the necessary foundation in terms of both physical infrastructure and market regulation mechanisms; the emergence of widely available hydrogen poses a danger for society due to its high combustibility. Following the results of the study, it was concluded that the existing pilot hydrogen projects are positive yet not scalable solutions for the power generation sector due to the lack of available technologies to construct large-scale and geographically distributed infrastructure and adequate international system of industry regulation. Thus, under current conditions, the risks of implementing such projects considerably exceed their potential ecological benefits.
Article presents results of study on possibility of increasing the efficiency of drilling directional straight sections of wells using screw downhole motors (SDM) with a combined method of drilling with rotation of drilling string (DS). Goal is to ensure steady-state operation of SDM with simultaneous rotation of DS by reducing the amplitude of oscillations with adjusting the parameters of drilling mode on the basis of mathematical modeling for SDM – DS system. Results of experimental study on determination of extrema distribution of lateral and axial oscillations of SDM frame depending on geometrical parameters of gerotor mechanism and modes ensuring stable operation are presented. Approaches to development of a mathematical model and methodology are conceptually outlined that allow determining the range of self-oscillations for SDM – DS system and boundaries of rotational and translational wave perturbations for a heterogeneous rod with an installed SDM at drilling directional straight sections of well. This mathematical model of SDM – DS system's dynamics makes it possible to predict optimal parameters of directional drilling mode that ensure stable operation of borehole assembly.
Paper presents the analysis of the investigation results of vibrational accelerations and beating amplitudes of the downhole drilling motor, which help to define the ranges of optimum energy characteristics of the gerotor mechanism, ensuring its stable operation. Dependencies describing the operation of the «drilling bit – rotary steerable system with power screw section – drilling string» system and the values of the self-oscillation boundaries and the onset of system resonance when it is used jointly, were defined as a result of computational and full-scale experimental research. A mathematical model is proposed, which allows determining the optimal range of technological parameters for well drilling, reducing the extreme vibration accelerations of the bottomhole assembly by controlling the torque-power and frequency characteristics of the drilling string, taking into account the energy characteristics of the power screw section of the rotary steerable system. Recommendations on the choice of drilling mode parameters were given.
The main directions of increasing the efficiency of drilling wells by improving methods for designing profiles of directional and horizontal wells are identified. The feasibility and necessity of using at drilling with rotary controlled systems the trajectories of directed wells' profiles with continuous curving, that do not contain conjugated sections, on the basis of plane transcendental curves are theoretically substantiated and experimentally confirmed. An algorithm and software are developed that allow optimal selection of a profile or a trajectory section, taking into account minimization of twisting, bending, compressive and tensile stresses that ensure the efficiency of technical and technological parameters of well drilling.
An analysis of operational capabilities of inclined drilling equipment and technology is presented. Two options of rotary drilling are reviewed as technical and technological solutions, facilitating construction of wells with difficult profiles. The first option implies that the driver unit of the drill bit is represented by downhole drilling motor, the second one utilizes sophisticated rotary steerable systems. Practical results of drilling wells with difficult profiles are presented. A quality assessment of drilling is provided through the example of comparing designed and actual trajectories, using different driver units for the drill bit, as well as properties of surrounding rocks, rheology of the drill fluid and other characteristics of dynamically active systems. A range of rotation speed has been determined that allows rotary steerable systems to have minimal oscillation amplitude of the bottom-hole assembly. Analysis of investigation results showed that the main source of oscillations is linked to bending and compressing stresses, caused by well deviations as well as rigidity of the drilling tool. In effect, in the bottom-hole assembly occur auto-oscillations, making it impossible to correct azimuth and zenith angles. Alteration of rigidity in the bottom part of the tool and drilling parameters, implying reduced rotation speed of the drill string and regulation of drill bit pressure, can partially solve this problem, though increase in rotation speed is limited by technical characteristics of existing top drive systems.
The article shows research analysis of engineering and technological solutions that aimed at improving the efficiency of drilling wells using optimization of dynamic of work downhole drill-ing motors. As the technical solutions that reduce vibration, considered two options of construc-tion of the power section. A first embodiment involves the production of a hollow rotor which can reduce its moment of inertia. The second solution is the production of modular rotor, which are changing the eccentricity (misalignment) of rotating parts of the engine. The research of fluctuations throughout the length of the power section of the working bodies and the spindle of the engine, taking into account changes in its energy characteristics has been con-ducted to ensure stable operation of the engine in a well, identifying optimal loading parameters. Indicators of shaft speed ensuring minimum vibration amplitude of the engine has been Iden-tified. Optimal speed range of the rotor to prevent buckling of the BHA and to sustain its operation is shown to be between 15-20 % of the frequency of the engine at idle. The maximum reduction in speed during the drilling process should not exceed 30 % by conducted research.
