地聚物基油气井固泥材料

地聚物是一类由碱激发剂和胶凝材料制备而成的、由SiO₄和AlO₄四面体单元组成的具有三维立体网状结构的无机聚合物材料。该类材料具有力学性能优异、与无机基材黏结强度高和流动性良好等特点。针对油气井中残余的泥饼导致水泥浆无法有效黏结“固井二界面”的问题，通过添加偏高岭土MK与油井钻井液中的黏土同构地聚物达成油井固泥效果。通过水玻璃和偏高岭土制备了低黏度、高渗透率的地聚物基固泥材料。该地聚物基固泥材料的玻璃模数为1.5，MK添加量为2.5%，其在常压和高压环境下均能渗入泥饼；经90 ℃固化10 h后泥饼的抗压强度分别为3.0 MPa和1.0 MPa；同时，固化后的泥饼能提高固井二界面的胶结性能，“地层-水泥”界面和“套管-水泥”界面的胶结强度分别为0.6和1.0 MPa。X射线衍射分析结果表明，MK的加入虽然无法改变最终固化后泥饼的结晶性能，但适量加入MK能提高胶凝材料的含量，从而进一步提高固化后泥饼的抗压强度和胶结强度。 

A Geopolymer Based Oil and Gas Well Cementing Material

Geopolymer is a kind of inorganic polymer made from alkali activator and gel material. It has a 3D network structure formed by SiO₄ and AlO₄ tetrahedra. Geopolymer has excellent mechanical performance, high bonding strength with inorganic substrate and good mobility. In oil and gas well cementing, the mud cakes remained on the borehole wall cause poor cementation of the cement sheath with the borehole wall. To solve this problem, metakaolin (MK) was added to form a geopolymer with the clays in the drilling fluid to improve the quality of well cementing operation. Using water glass and MK (at a concentration of 2.5%), a geopolymer based well cementing material with low viscosity and high porosity was developed. The glass modulus (M) of the geopolymer was 1.5, and it can effectively penetrate mud cakes at both normal and high pressures. After being solidified at 90 ℃ for 10 hours, the compressive strengths of the mud cake were 3.0 MPa and 1.0 MPa, respectively. Meanwhile, the solidified mud cakes can enhance the bonding strength of the cement sheath with the borehole wall, the bonding strengths of the “borehole wall – cement sheath” interface and the “casing – cement sheath” interface were 0.6 MPa and 1.0 MPa, respectively. XRD analysis revealed that although the addition of MK cannot change the crystallization property of the mud cakes after final solidification, it to some extent increases the concentrations of the gel materials in the mud cakes, which further increases the compressive strength and bonding strength of the solidified mud cakes.