Proportional-Derivative Control of Stick-Slip Oscillations in Drill-Strings

Stick-slip oscillation in drill-string is a universal phenomenon in oil and gas drilling. It could lead to the wear of drill bit, even cause catastrophic failure of drill-strings and measurement equipment. Therefore, it is crucial to study drilling parameters and develop appropriate control method to suppress such oscillation. This paper studies a discrete model of the drill-string system taking into account torsional degree-of-freedom, drill-string damping, and highly nonlinear friction of rock-bit interaction. In order to suppress the stick-slip oscillation, a new proportional-derivative controller, which can maintain drill bit’s rotation at a constant speed, is developed. Numerical results are given to demonstrate its efficacy and robustness

Continuity in the Development of Judicial Law

The ongoing changes in the legal map of the world reflect the interaction of legal systems. These processes inevitably affect the scope of activities of the judicial authorities associated with such a phenomenon as judicial law. The authors of the article take a narrow approach to understanding it. It implies the manifestation of judicial law as judicial practice and judicial precedents. The relevance of the topic is due to the fact that the phenomenon of judicial law goes beyond the limits of a single legal family, which implies its comparative legal research. At the same time, an important direction of such activity is the study of the development of this law associated with the processes of continuity. The objective of the study is to identify the concept and features of continuity in the development of judicial law. To do this, the authors formulated the following tasks: identify the concept and signs of continuity within the framework of legal development; disclose the peculiarities of understanding judicial law; determine the characteristic features of continuity in the development of judicial precedents; characterize continuity in the evolution of judicial practice. The conducted research is based on a dialectically understood model of continuity. This assumes the use of a systemic paradigm associated with a constellation of different methods, such as comparative, structural-functional, etc. The results allowed the authors to determine the trends and prospects for the development of judicial law within the framework of certain legal spaces. The authors of the article believe it advisable to use these results in subsequent research on this topic

Chages in parameters of deposits No. 301, 302, 303 of Romashkinskoye oil field in modeling reservoir conditions

Parameters of the carbonate rocks of the oil deposits of 301, 302 and 303 of Romashkinskoye field were estimated on 69 core samples. Modelling of reservoir conditions during deposits development was carried out using IFES-1 facility (Republic of Bashkortostan, Oktyabrsky, VNIIGIS). We estimated true resistivity, P-wave velocity and the porosity before loading the sample and after load removal. Samples were placed in a chamber and the measurements were made under conditions close to the reservoir ones. Loading configuration intended constant confining pressure (rock pressure) and changes in pore (reservoir) pressure. At each stage of reservoir pressure changing it has been given a certain period (30 min) to complete the transition process. Two months after the measurement (after full restoration of elasto-mechanical properties) we determined gas permeability of samples again. Porosity of Vereckiann rocks was 3-20 %, of Bashkirian - 1.5-21 %, of Protvinskian - 0.2-23 %. We considered two variants of the technology-related loading: soft and hard. In the soft mode pore (reservoir) pressure reduced from maximum (6.56-7.15 MPa) to an average value (2.24-4.0 MPa) and then restore to maximum. In the hard mode pressure reduced from maximum pore (reservoir) pressure to average value, decreased to minimum (1.0-0.2 MPa) and then restored to maximum. We determined that rocks parameters had not significantly changed under soft mode of technology-related loading. Under hard mode of loading porosity decreased, true resistivity and P-wave velocity grew up. Comparative analysis shows that for the majority of collector of the Vereiskian and Bashkirian productive horizons gas permeability is characterized by reduction of porosity. In case of Protvinskian high fractured rocks gas permeability increases sometimes

Second Order Stochastic Partial Integro Differential Equations with Delay and Impulses

© Published under licence by IOP Publishing Ltd. The aerosol movement at an open end of a pipe at the resonant frequency was experimentally studied. The aerosol flow in an external wave field was visualized. The numerical value of the Rayleigh correction for an open end of an experimental plant was obtained. A good agreement between the numerical and experimental values was demonstrated