油气井眼井斜角、方位角对盐岩蠕变的影响

 盐岩在应力作用下发生蠕变导致井眼闭合，常引起钻具卡钻事故。现有分析盐岩蠕变模型大都基于二维平面模型，很难有效地分析定向井的蠕变卡钻问题。在空间坐标变换的基础上建立定向井三维蠕变模型，将应力在井斜角方位角的变化转换为井轴坐标系下的变化。利用所建立的数字模型，分析在一定应力条件下井斜角与方位角变化对蠕变的影响，同时提出定向井眼参数存在蠕变“敏感区”的理论，为顺利钻穿盐岩层提供优化设计的定向参数。经过现场实例验证，利用建立的三维数字模型计算得出的安全泥浆密度在盐岩层定向钻井时，能够安全顺利钻穿盐岩层，为盐岩层的定向钻井推荐安全泥浆密度提供参考方法。

INFLUENCE OF INCLINATION ANGLE AND AZIMUTH ANGLE OF BOREHOLE ON CREEP OF SALT ROCK

Salt rock can make borehole close in the effect of creep，which often leads to stuck. However，many analytical models for creep of salt rock are based on the two-dimensional models currently，which are hard to analyze the problems of stuck because of creep in controlled directional well. Based on space coordinate transformation，the 3D model of creep of controlled directional well is established，and the variations of stresses with the actual deviation and azimuth angle are transformed to the hole axis. The established model analyses the influence of the variation of deviation and azimuth angle on creep under certain stress，and also propounds the concept that the “sensitive zone”of creep exists in parameters of some borehole of the directional well，which offers references to optimize the design of some parameters to drill out the salt formation successfully. Through actual example，it is verified that the security mud density based on the 3D numeral model is suitable during drilling the salt layer，which gives instruction of security mud density in practicing directional drilling in salt formation.