Tyrlych V. Providing of trouble-free operation of drilling pipes with detected operational defects

Dissertation is devoted to ensuring of trouble-free operation of drilling pipes with operational defects by assessing their stress-strain state and predicting the residual resource. Mathematical models of drilling columns with longitudinal and longitudinal-torsional oscillations containing operational defects are developed. On the basis of the developed models a study of the strain-strain state of the drill column and the effect on it of the vibration protection devices were carried out. It is established that the contribution of the dynamic component to the total intensity of stress varies in the range from 10 to 25 % and depends on the conditions of the drill column. Experimental-estimation estimation of critical sizes of operating defects depending on their type and sizes is carried out. The critical and characteristic depths of the external or internal transverse annular crack for drill pipes of the strength groups G-105, L and S-135 are established taking into account the influence of dynamic loads during the run-up operations. The conditions of critical destruction during the operation of the drill string of drill pipes of strength groups G-105 and S-135 were evaluated.