选择性渗透水泥石

分析了欠平衡钻进井眼的固井、产层堵漏和油层防砂开采作业中存在的问题，提出了解决这些问题的思路和选择性渗透水泥石的概念。选择性渗透水泥石不仅具有选择渗透性，而且具有选择相渗透性，它主要由水、水泥颗粒、增孔剂颗粒、连通剂和相渗剂等添加剂组成，增孔剂主要作用是增加水泥石的空隙度，连通剂主要作用是连通增孔剂、水泥颗粒之间的空隙，相渗剂主要作用是增加体系的相渗能力。选择性渗透水泥浆具有强的触变性，使水泥浆进入地层裂缝和孔隙中后，由于形成较大胶凝强度，阻止水泥浆的流动，减小漏失深度；该体系固相含量高，固相颗粒粒径分布范围宽，使其在较大裂缝和孔隙中多颗粒架桥的概率增大，封堵性增强；水泥石抗压强度较高，能满足某些特殊井固井、油井堵水、产层堵漏、油层防砂工艺的要求；水泥石具有很好的堵水输油性能，无论是单相渗流，还是两相同时渗流，油相的渗透性均好于水相的渗透性。

Cement of selective permeability

By analyzing the problems exist in cementing, lost circulation plugging, and sand control production, methods for solving these problems, together with the conception of selective permeable cement are presented. The selective permeable cement is featured not only on the selective permeability, but phase-selective permeability also, and it is composed of water, cement grains, pore-enhancing grains, communicating agent and phase-permeability enhancing agent, etc. Pore-enhancing agent is used to improve the porosity of cement, and connecting agent is used to communicate the pores between cement and pore-enhan- cing grains, while phase-permeability enhancing agent is mainly used to improve the permeability of the system. As its distinguished thixotropic behavior, when the cement slurry enter into formation fractures and pores, high gelling strength is formed, and this stops the flow of cement slurry and minimize lost circulation. Due to the high solids content and wide range of solids granularity distribution of this system, the probability of multi-grain bridging in the larger fractures and pores increases, and its plugging capacity also improves; in addition, the higher compressing resistance of the cement rock could meet the requirements of cementing in some special wells, oil well water blocking, production formation plugging and sand controlling. The cement rock also has good water blocking and crude transportation capacity, no matter it is single-phase permeable flow or two phase permeable flow simultaneously, the permeability of oil phase is always higher than that of the water phase.