ADAPTABILITY ANALYSIS AND IMPROVEMENT OF THE API CALCULATING METHOD OF THE PERMISSIBLE STRESS FOR H-GRADE SUCKER ROD

Based on the much better mechanical properties of H-grade uhra-high strength sucker rod good, it has been applied in Changqing Oilfield since 2009, and moreover by the end of 2015, the applied well number reached more than 26 thousand. But in the application process, the conventional API calculating method has always been used ; there is no specific calculating method for H-grade sucker rod allowable stress, this results in the conservative design, serious waste and indirectly increased oilfield development costs. On the basis of analyzing the API calcu- lating method of the permissible stress, the API calculating method for H-grade sucker rod was established specific- ally, and furthermore the main influencing factors were analyzed. So the evidences were provided for the string opti- mized design and rational utilization of H-grade ultra-high strength sucker rod.