碳酸钙晶须对油井水泥增强抗收缩机理及应用

Mechanism of Calcium Carbonate Whisker Enhancing Cement's Resistance to Contraction and Its Application

为了解决因水泥石韧性不足与体积收缩而引发的水泥环完整性破坏的问题,考察了碳酸钙晶须对油井水泥的力学性能、体积收缩与综合性能的影响。在油井水泥中分别掺入0、1%、2%、3%、4%碳酸钙晶须,测试1、3、7、14、28 d时的抗折强度、抗压强度、体积收缩率与水泥浆的综合性能。结果显示,养护28 d后,掺入3%碳酸钙晶须的水泥石比未掺入碳酸钙晶须的水泥石,抗压强度增加36%,抗折强度增加33.67%,体积线收缩率减小82.97%,碳酸钙晶须的加入会减少水泥浆的稠化时间,增加流动阻力,但综合性能依然满足固井作业的要求。

Perforation, acidizing and fracturing operations often cause damage to the integrity of cement sheath. Volumetric contraction of cement during hydration process always produces micro fissures and micro annulus, forming channeling path for channeling between formations, which in some cases may cause oil and gas to channel to the surface. These problems are brought about by the lack of toughness of set cement and the volumetric contraction of cement slurry during hydration. In laboratory studies, calcium carbonate whisker was added to cement slurry at 0, 1%, 2%, 3% and 4%, respectively, and the flexural strengths, compressive strengths, rate of volumetric contraction, and the overall properties of the set cement at 1, 3, 7, 14 and 28 days, respectively, were measured. Compared with cement slurry without treatment of calcium carbonate whisker, cement slurries treated with 3% calcium carbonate whisker, after aging for 28 days, had compressive strength increased by 36%, flexural strength increased by 33.67%, and volumetric contraction reduced by 82.97%. The overall properties of the cement slurry also satisfied the need for well cementing.