微流变学研究钻井液静态黏弹性特征

Study on Static Viscoelastic Characteristics of Drilling Fluid Using Micro-rheology

钻井液在静止时微观结构和性能逐渐变化,通过微流变技术研究了钻井液在静止状态下黏弹性的变化过程。配制了6种不同配方的油基钻井液,在高速搅拌后使用Rheolaser流变仪测试了钻井液的黏弹性变化。实验发现油基钻井液的网络结构是悬浮重晶石的骨架,在高速搅拌后,钻井液的网络结构被打散,在静止时结构开始恢复,损耗因子随着时间延长越来越小,意味着重晶石沉降的速率越来越小;性能不好的钻井液静置一段时间后黏度因子和弛豫时间发生下降,其结构开始失稳,此时可能导致严重的重晶石沉降问题;有机土和提切剂对钻井液的微观结构有明显的加强作用,当这种可以形成结构的材料达到一定浓度后,其结构恢复得更快。微流变学可以在微观角度来描述钻井液的结构变化过程,这对进一步研究和了解钻井液复杂的性能变化有重要的意义。

The changing process of the viscoelasticity of drilling fluid at static condition was studied using micro-rheology technology.Drilling fluids of different compositions were formulated and tested on their viscoelasticity with Rheolaser^(TM) after agitating at high shear speeds.Laboratory study found that it is the network formed in oil base drilling fluids that suspend barite particles.Oil base drilling fluid lost its network structure at high shear speeds and resumed the network if allowed to stand quiescent for enough time.The dissipation factor of the network,an indicator of the drilling fluid's ability to resume its original network structure,was decreasing with time,meaning that the settling speed of barite particles was becoming slower.Drilling fluids with poor behavior will lose part of their viscosity and relaxation time,leading to instability in their network structures and fast settling of barite particles.Organophilic clay and gelling agents having the ability to reinforce the micro structure of drilling fluid,when added to a certain amount,accelerate the resumption of the network in drilling fluid.Micro-rheology can be used to describe the changing process of the network formed in drilling fluid,and hence plays an important role in studying and understanding the complex performance changing of drilling fluid.