压差卡钻新模型的建立与分析

压差卡钻的准确预测对于预防和减少钻井过程中卡钻事故的发生具有重要意义，目前的压差卡钻模型缺乏对钻井液泥饼与井壁压力关系的研究，模型不完善。在前人研究的基础上，根据钻井液泥饼的性质，结合压差、钻具与井壁的封闭接触面三因素建立压差卡钻预测新模型。通过压差卡钻机理分析和实例计算表明，钻井液在井壁上所形成的内泥饼与外泥饼的渗透率越接近，井壁处的压力越高，有利于预防压差卡钻的发生；如果外泥饼的质量越好，泥饼薄且耐压缩性好，发生压差卡钻后，所产生的黏附力就越小，也易解除，从而真正预防压差卡钻的发生。该研究为现场预防压差卡钻事故和钻井液设计提供了理论指导。 

The Establishment of a New Model for Differential Sticking Analysis

Accurate prediction of differential sticking plays an important role in minimizing and even preventing pipe sticking. Models presently in use for the prediction of differential sticking are not perfect, lacking studies on the relationship between mud cakes and pressures on the borehole wall. A new differential sticking prediction model has been established based on the studies made by other researchers, taking into account those factors such as the properties of mud cakes, differential pressure and the closed contact interface between drill string and borehole wall. Analyses of differential sticking mechanisms and calculation with drilling data indicated that the closer the permeability of an external mud cake to the permeability of a mud cake formed inside the formation, the higher the pressure exerted on the borehole wall, and this is beneficial to the prevention of differential sticking. A thin high quality external mud cake with good compressibility generates a low adhesion force at the time of differential sticking which is also easy to be unloaded, thereby fundamentally realizing the prevention of differential sticking. This study will provide theoretical guidance to the prevention of differential sticking in field operations and to drilling fluid program design.