Experiments on integrated solidification and cementation of the cement-formation interface using the Mud Cake to Agglomerated Cake (MTA) method

Abstract

Based on the scientific concept of Mud Cake to Agglomerated Cake (MTA), the integrated solidification and cementation of materials at the cement-formation interface was studied by mechanical evaluation, microstructure analysis (XRD, TG and ESEM), and fluid dissolution tests. The results of the mechanical evaluation show that compared with the existing method of MTC, the bond strength of the cement-formation interface increased by 37.81% (increasing up to 1 606.31% with longer curing time) with the MTA method. The results of microstructural analysis show that the synchronous hydration and hardening reaction between the mud cake and cement slurry occurred locally, and a little CSH(I) (calcium silicate hydrate) gel and heulandite gel formed. The results of fluid dissolution tests show that the mud cake in a finished sample made by the old method was dissolved and became a turbid drilling fluidr after it was immersed in water for 28 days. However, based on the MTA method, the agglomerated cake and hardened cement paste bonded together. The agglomerated cake was not dissolved and the water remained clear. All the above results corroborate two facts, one is that the mud cake has converted to agglomerated cake, the other is that the cement-formation interface has solidified and cemented integrally. 摘要: 基于泥饼仿地成凝饼的科学构想，采用力学性能评价（如胶结强度）、微观结构分析（如X射线粉末衍射分析、热失重分析、环境扫描电子显微镜分析）和流体溶蚀实验等方法对MTA方法固井二界面整体固化胶结进行了实验研究。研究结果表明：随着养护时间的延长，用MTA方法得到的固井二界面胶结强度较目前提高了37.81%～1 606.31%；泥饼与水泥浆发生了局部的同步水化硬化反应，且生成了少量的团状水化硅酸钙（CSH(Ⅰ)）凝胶和片沸石类凝胶，显示固井二界面整体固化胶结；流体溶蚀实验表明，采用目前方法，养护成型的样品浸泡28 d后，泥饼还原成了浑浊的稀钻井液，而用MTA方法得到的凝饼与水泥硬化体已胶结为一体，且凝饼未被溶蚀，表现为杯内流体仍清澈。这印证了两个事实：一是泥饼仿地成了凝饼，二是固井二界面已整体固化胶结。 Key words: cement-formation interface, Mud Cake to Agglomerated Cake (MTA), MTA method, integrated solidification and cementation, experimental evidence