钻井液触变性评价方法的合理性探索

Study on Rationality of the Evaluation Method for the Thixotropy of Drilling Fluids.

目前评价钻井液触变性的方法有静切力法、浮筒切力计法、滞后环法、滞后总能量法以及储能模量法, 它们都或多或少地存在着一定的局限性。选用聚磺、聚合物以及三磺钻井液体系,通过实验验证了目前通用的评价钻井液触变性的方法——静切力法的合理性,考察了热历史和静置时间对钻井液静切力的影响。研究结果表明:钻井液体系经热处理后,其静切力都有不同程度的降低,并在钻井液结构恢复的过程中保持这一特性,但最终的触变性变化不大。单从触变性这一角度出发,钻井液受热历史的影响不大;在40 min以内随静置时间的延长,3 种钻井液体系的静切力一直增加,且还有进一步增大的趋势,在静切力曲线上有两个急剧增加的阶段,第二个急剧增加阶段一般出现在10 min之后,因此10 min时的静切力无法真实地反映钻井液最终切力的大小,现行静切力法不能真实地评价钻井液的触变性。

At present, the evaluation methods for the thixotropy of drilling fluids are gel strength, flotating buoy shear stress meter, hysteresis loop, hysteresis total energy and storage modulus, but these methods exist some limitations more or less. This paper verified the rationality of the method-gel strength that is generally used through experimental justification, checked the effect of heat history and stewing time on the gel strength of drilling fluids. It was shown that: only from the view of thixotropy, the heat history has little effect on the drilling fluids. The gel strength at 10 minutes cann't reflect the final shear stress of drilling fluids, the current method of gel strength cann't evaluate the thixotropy of drilling fluids authentically.