Introduction. Torsional vibrations caused by drilling using a polycrystalline diamond compact (PDC) bit are analysed using wellbore data obtained under various drilling modes. The drilling caused by torsional vibrations are analysed. Two types of torsional vibrations, including those caused by the cutting action of a bit and by frictional forces.Aim. To investigate the induction of torsional vibrations as a result of rock destruction by PDC bits.Materials and methods. The research methodology was based on “Richard-Germay-Detournay” and “Tian-Detournay” bit designs and methods for reducing the critical effects of torsional vibrations induced by PDC bits during rock destruction.Results. Statistical analysis has shown that the drilling efficiency of the bit (DE) correlates well with the occurrence of torsion vibrations caused by the bit. The aggressiveness of the cutting structure of the PDC bit can be represented by an average DE rating. If the PDC bit is designed so that its DE exceeds a critical value, then the occurrence of torsion vibrations on the bit is unlikely during drilling.Conclusion. When drilling with a polycrystalline diamond PCD bit, two types of vibrations occur. If torsional vibration occurs due to the cutting action of the bit, then the fight against this process is focused on the design of the bit and operational parameters, the load on the bit and the speed of rotation of the bit. If the torsional vibration is caused by friction, vibration reduction methods should be focused on changing the design of the BHA and the drill string or the profile of the well. Therefore, it is very important to determine whether the torsional vibration is caused by the friction force of the elements, the cutting action of the bit, or both. In drilling, it is always necessary to search for the maximum penetration speed by changing the load on the bit under specified drilling conditions. To do this, it is necessary to evaluate the drilling efficiency of the DE bit, therefore, this article has evaluated the parameter depending on the size of the bit, which will determine the critical value of the drilling efficiency parameter.
Background. The production of oil and gas by horizontal wells, despite all its advantages, is subject to exploratory and operational complications. At the final stage of their development, such fields become hard-to-recover reserves. Production of oil and gas is often associated with a high water cut, a significant drop in reservoir pressure, and precipitation of asphaltene deposits.Aim. To analyze the problem of early indication of flooding of horizontal wells and do research on existing solutions nowadays.Materials and methods. The dependence of the logarithm of the water-oil ratio on the cumulative oil production was investigated. An analysis of production decline curves was carried out, along with a graphical diagnostics of flooding evolution.Results. The anticipated cumulative production of a well was determined by continuing the linear dependence to its economic limit. A graph was plotted in semi-logarithmic coordinates for the analysis of production decline curves. According to the dependence of the water-oil ratio versus time, the type of early well flooding was determined in logarithmic coordinates.Conclusion. One of the most significant problems in the development of horizontal wells consists in the high water cut of the obtained products. According to the data for 2020, the average water cut in the main fields of Russia comprises at least 85%, with the mass ratio of produced oil and associated water approaching 1:7. The use of water-soluble polymers for waterproofing of horizontal wells can be considered a promising direction due to their efficiency in limiting water inflow in vertical and directional wells.
Background. Drilling vibrations may cause damage to the bit and early failure of downhole instruments. The main approach to solving this problem consists in measuring downhole vibrations while drilling by adding sensors near the bit in to the bottom hole assembly (BHA). When drilling vibrations are registered, measures are taken to avoid their reaching the critical values. If necessary the drilling stoops and the section is worked out to avoid accidents due to the high critical values. Not always drilling companies add such sensors to the BHA due to high price of the equipment. Constant problems with vibrations while drilling, require the creation of domestic low-cost autonomous equipment for measuring downhole vibrations and transmitting respective signals to the surface.Aim. To develop domestic low-cost autonomous downhole vibration measuring equipment.Materials and methods. Analysis of the experimental studies on drilling vibrations. Development technical solution such as domestic low-cost autonomous equipment for measuring downhole vibrations.Results. The problem of drilling vibrations can be controlled by downhole measuring equipment located in the vicinity of the bit. The device under development is presented in the article.Conclusion. In order to achieve maximum economic efficiency and avoid the costs of eliminating the consequences of vibrations, domestic low-cost autonomous downhole vibration measuring equipment should be developed to register torsional and longitudinal vibrations.
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