不同剪切作用下CMC水溶液的微观结构研究

针对聚合物钻井液重要组分之一的羧甲基纤维素钠盐(CMC),考虑钻井液在井底钻头与环空处所受的不同剪切作用,测试了其水溶液在相应近似剪切作用(分别为600,6 000 r/min)下的流变性,并结合冷冻干燥方法,利用扫描电子显微镜观测了这两种剪切作用后CMC水溶液相应的微观结构.结果表明高速剪切作用使CMC水溶液的空间网络骨架拉伸变细,甚至破坏,溶液黏度有所降低,流动性增大.这样,热量更容易通过这些网络骨架,使充填其中的小分子物质以热传导、对流传热等方式传递到钻屑表面,分解钻屑表面的水合物.水合物分解产生的气体和水则以分子扩散的形武向内向外进行传质,但会受到钻井液微观骨架结构和其中填充物质的阻碍.

Microstructure Research of CMC Solution at the Different Shearing Action

The dissociation of hydrates on the sidewall and the dissociation or reformation of hydrates in annulus can cause some hole problems,such as the change of properties of drilling fluids,blocking in annular and wellbore collapse,which have a direct influence on drilling operation.With the influence of flow shearing action,the microstructures of drilling fluids have played an important role in the process.The drilling fluids microstructures are very complex,but sodium carboxy methyl cellulose(CMC) is only researched as one of the most important components of the polymer drilling fluids.Considering the different shearing action on the drills and in annulus,the rheological properties of CMC solution are tested at the different corresponding shearing action(600 r/min and 6 000 r/min respectively).Using the freeze-drying method and scanning electron microscopy,the corresponding microstructures of the CMC solution are observed after the two kinds of shearing action.Results show high-speed shearing action can change and even destroy the net framework structures of CMC solution,then the viscosity of solution decreases.Thus,heat and mass around the drilling cuttings can transfer more easily to the surface of the drilling cuttings through the net framework and the micro molecules in the form of heat conduction and convection heat transfer,and lead to the hydrates dissociation.Gas and water that the hydrates decomposition produced transfer to outward and inward in the form of molecular diffusion,but mass transfer is blocked by the drilling micro-skeleton structure and the obstacles of implants.