ARRANGEMENT OF LOWER PART OF DRILLING STRING Russian patent published in 1999 - IPC

FIELD: bore-hole drilling machinery and equipment. SUBSTANCE: arrangement of lower part of drilling string includes rock-crushing tool installed on end of lower drilling pipe. Centralizers are installed along axis of drilling pipes. Diameter of at least one of centralizers is less than diameter of rock-crushing tool. Distance of each of centralizers from rock-crushing tool is determined from solution of linear differential equation of fourth order relating to deflection of arrangement of lower part of drilling string with taking into consideration axial force exerted on drilling bit, zenith angle of bore-hole, frequency of lateral oscillations of drilling string, number and diameter of centralizers, number of joints of drilling pipes of various diameter, and also values of lateral force and incline angle preset for bottom-hole of well. Application of aforesaid arrangement of lower part of drilling string allows for reducing lateral oscillations of drilling string and due to that ensures increase of drilling speed by 12% on average. EFFECT: higher efficiency. 2 dwg, 1 tbl