石油套管联接园扣螺纹的合理扣数问题

目前，石油套甘联接的螺纹牙形有脚扣、梯形扣和奥米加扣等几种扣型。固井工程中，最常用的套管螺纹为园扣。关于园扣螺纹的尺寸参数，国产套管及接箍规范(YB690一70)、API套管规范以及苏制套管规范均作了规定。规范中，除规定了螺纹每时长的扣数外，尚有长扣与短扣之分。各种尺寸的套管，螺纹(长扣和短扣)的有效总扣数在18一36扣之间。关于套管联接螺纹有效总扣数的合理扣数问题，应从什么角度出发确定，有必要进行研究探讨。本文将从套管柱受轴向拉伸载荷作用下的弹性静力分析出发，研究联接螺纹中的载荷分配特点，提出设计套管联接螺纹的合理有效总扣数，供设计套管螺纹参考。

ON THE OPTIMAL NUMBER OF TURNS OF THE ROUND JOINTING THREAD OF OIL CASING PIPES

It is necessary to study how to determine the optimum of the total number of effective turns of the round jointing thread of oil casing pipes.In this Paper, the equation of the load of the jointing thread is obtained by analysing elastic of the round jointing thread of the casing string under stretching stress. The optimal number of turns of the round jointing thread of oil casing pipe is deduced by means of numerical calculation of the dimension parameters of Chinese-made casing pipes and casing collar in technical manual (YB690-70) and by analysing the load distribution feature in jointing therad.