粉煤灰-微硅-水泥三元复合低密度充填水泥浆在页岩油水平井的应用

为提高页岩油水平井上部固井质量,通过浆体稳定性差异反向优化颗粒配比,采用碱石灰和硫酸镁制备新型水化激活剂,结合²⁹Si NMR进行反应程度定量分析,开发了一种粉煤灰-微硅-水泥三元复合低密度充填水泥浆,并开展了五口井的工程试验。结果表明,粉煤灰和微硅的最佳加量分别为40%、35%(质量分数),碱石灰与硫酸镁的配比为3∶1(质量比)时组成的激活剂效果最好,可将油井水泥的反应剩余量降低29.59%,粉煤灰的反应剩余量降低68.61%,常温下3 d、7 d抗压强度分别提升129%和92%,三元复合体系的失水、游离液、稠化时间等均能满足固井充填需求,现场应用表明固井合格井段占比超过90%,体系具有良好的应用前景。

Application of Fly Ash-Micro Silicon-Cement Ternary Composite Low Density Filling Cement Slurry in Shale Oil Horizontal Wells

In order to improve the cementing and filling effects of the upper part of shale oil horizontal wells, the settlement stability evaluation method was used to design the particle ratio scheme with equal particle size, which can simulate the actual temperature and pressure conditions underground. And a new hydration activator that is suitable for the normal and low temperature environment was developed with alkali lime and magnesium sulfate. In conclusion, a ternary low density filling cement slurry composed of fly ash, micro silicon, and cement was created by the ²⁹Si NMR quantitative analysis, and it was carried out in 5 shale oil horizontal wells of Yanchang oilfield. The results show that the cement slurry is the most stable when the optimum dosage of fly ash and micro silicon is 40% and 35% (mass fraction), and the activator works best when the mass ratio of alkali lime to magnesium sulfate is 3∶1. All the above reduce the residual amount of cement by 29.59% and fly ash by 68.61%, and increase the 3 d and 7 d compressive strength of low density cement slurry at room temperature by 129% and 92%, respectively. In addition, the water loss, water precipitation and thickening time of the ternary composite system totally meet the needs of cementing and filling. The application of 5 wells shows that the qualified sections account for more than 90%, and the cement slurry has good application prospect and large-scale popularization potential.