Failure Analysis And Prevention Of The Oil Drilling Tools

With the development of world economy and the growth of population, the demand of energy is more and more big, and the energy has become one of the most serious problems humanity must facing. China has a large population, so the energy problem of our country is more urgent. Oil occupies the important position in the world's energy, and the drilling tools play an important role in the oil and gas drilling process. But in the condition of complex geological structures and poor working conditions, the failure of drilling tools is common, which cause a large number of economic loss.As the failure reasons for the drilling tool joint with FH-box is analyzed in this paper, we can include that under the combination of axial tensile stress, circular tensile stress and sensitive corrosion medium, the stress corrosion cracking occurs in the position which perpendicular to the tensile stress because the transverse mechanical property of the tool joint is poor. The cracks nucleate in the inner surface, propagate intergranularly, and cause the final stress corrosion fracture. Through the analysis of failure drill pipe, we can include that the service life of the drill pipe can be enhanced by improve the drill-pipe-body internal upset taper length (miu) to reach more than 102mm, used internal coating and PD series double shoulder. For the working condition which the formation temperature is close to 90? and the drilling mud is prepared by sea water, the drilling pipe can be corroded by CO2 and O2. As to achieve the aim of reducing corrosion rate, the materials contained high Cr can be used to manufacture the drilling tools. For the failure drill collar, we can include that the fracture of this drill collar is failure. The fatigue cracks formed at the last 1-2internal screw thread, where the stress is concentrated and the stress in unite area is relatively higher. Stress distribution in the position of internal thread disappear can be improved by the stress-relief grooves machining and cold rolling for the thread root and stress-relief grooves, which can improve the fatigue life.