Development of Technology for Hydromechanical Breakdown of Mud Plugs and Improvement of Well Cleaning by Controlled Buckling of the Drill String  
[PERSON]  
11 20222202  
is the timely regulation of key parameters: DS rotation speed, flow rate and axial load on bit. An increase in the flow rate leads to an increase in the upward flow velocity in the annular space and an improvement in well cleaning [11]. The dynamic component of the ECD strongly depends on the consumption of drilling mud. However, it is impossible to improve cleaning by increasing the consumption of mud alone, especially under conditions of a narrow range of fluid loss and kick pressures [12]. Increasing the rotation speed of the DS has a hydrodynamic effect on the cuttings, creating a circumferential flow that does not carry particles out of the well, but has a \"turbulent\" effect, which contributes to the removal of particles from stagnant zones [13; 14]. It has been empirically established that an increase in the rotational speed of the DS to 140 rpm has a positive effect on the quality of cleaning, and a subsequent increase in the rotational speed has practically no effect on the removal of mud. A significant increase in the rotation frequency of the bottom hole assembly (BHA) can have a negative impact on the elements of the BHA, such as reactive torque increase--twists-off, increase vibrations and beats--irreversible deformations and breaks-off. The use of special technical means that are part of the DS and improve well cleaning [15; 16; 17], such as turbulators, circulating subs, etc., do not obtain the desired effect, due to the complexity of the trajectories, limitations in the number of installed devices, vugular porosity and rock stability. In oil production, there were situations when the presence of turbulators had a negative effect--the reactive twisting moment increased, and the area of the annular space decreased, which led to an increase in hydraulic shocks and an increase in ECD [16]. The rheology of the mud is one of the factors that have a significant impact on the cleaning of deviated wells, ECD and the state of the bottomhole zone [18; 19]. Undoubtedly, mud chemical treatment makes it possible to increase the efficiency of well cleaning and prevent technological complications in the drilling process. However, there are risks of contamination of the oil and gas saturated formation [20], and the selection of complex rheological profiles for drilling with a complex trajectory in specific geological and technical conditions requires significant financial costs. The increase in drilling speed is affected by the axial load on the bit, as well as the quantity and quality of mud, which must promptly clean the bottomhole from cuttings during drilling. The axial load applied to the entire area of contact with the drilling tool must exceed the strength of the rock and break it down. However, it is known that in directional wells, and especially in wells with complex profiles and large deviations from the vertical, the axial load applied to the bit does not reach the bottom hole in full [14; 21]. This is due to the complex stress-strain state of the drilling tool in cramped downhole conditions. The initial increase in the axial load that does not reach the bottom leads to the loss of the longitudinal stability of the DS and the acquisition of the shape of a sinusoid--a bend of the first kind (sinusoidal buckling) is formed. With a subsequent increase in the load, the DS takes the form of a spiral--a bend of the second kind (spiral buckling) is formed [22]. Longitudinal loss of stability of the drilling tool contributes to the occurrence of lapels and fractures of the drilling tool. In drilling practice, engineers try to avoid situations in which the DS loses its stability and takes any form of buckling [14; 21; 22; 23]. However, the positive effects of artificially created and controlled buckling of the DS on the destruction of mud plugs and cleaning the well from cuttings are proposed in this paper.