层流顶替钻井液滞留层厚度研究

A study on drilling mud stagnant layer thickness under the condition of laminar displacement

固井注水泥顶替后,在套管壁和井壁上滞留的钻井液会严重危害固井质量。为对环空壁面上钻井液滞留层开展理论研究,将井眼环空看作由无数个变宽度的两平板组成。该文首先分析了注水泥顶替时环空间隙内流体切应力的分布特征,确定了壁面处钻井液产生滞留的条件,进而建立钻井液滞留层厚度计算模型,并采用"二分法"对模型进行了数值求解,计算了在不同套管偏心、井斜角及流体性质条件下钻井液滞留层在壁面上的厚度。并根据钻井液滞留层厚度计算模型,推导了环空壁面上不存在钻井液滞留时流体性质之间所需满足的定量条件。

After the process of cementing displacement, drilling mud left on the wall of casing and borehole affects cementing quality severely. In order to conduct theoretical research on the mud stagnant layer, the annulus can be thought to be composed of numerous slots with a changing width. Shear stress distribution in the annular was analyzed firstly, and the condition leading to existing of drilling mud stagnant layer was determined. Then model of drilling mud stagnant layer thickness was founded and calculated by bisection method. The model can help to get the thickness of mud stagnant layer in situations of different eccentricity, deviated angles, and fluid properties. In the end, quantitative condition of no drilling mud stagnant layer exist was derived, which provided theoretical basis for adjusting rheological parameter reasonably and improving displacement efficiency.