消泡剂X60L对油井水泥净浆物理力学性能及微观结构影响的实验研究

Experimental study on the effect of defoamer X60L on the physical and mechanical properties and microstructure of net slurry of oil well cement

摘要:

固井水泥浆制备过程中,超高的拌浆速度容易引入气泡,导致水泥浆难以配制到正确密度,进而会对浆体性能和水泥环的密封完整性产生不利影响。本文以脂类消泡剂X60L为例,探究不同掺量的X60L消泡剂(0%、0.5%、1%、1.5%)对油井水泥抗压强度的影响。结合热重分析、X射线衍射分析、X射线计算机断层扫描测试和扫描电子显微镜测试,掌握水泥浆微观结构变化规律,明确消泡剂对水泥浆的作用机制。研究结果表明,水泥石的抗压强度呈现先增加后降低的趋势,而孔隙率则呈现先降低后增加的趋势。当消泡剂掺量为0.5%时,水泥石具有最低的孔隙率和最高的抗压强度。水泥石孔隙率越大,抗压强度越小,抗压强度和孔隙率呈明显负相关,且符合Schiller函数(R2^=0.98)。消泡剂的掺入并不会改变油井水泥的矿物成分和水化产物,消泡剂主要通过降低气泡的表面张力,使气泡难以维持从而破碎。但随着消泡剂掺量的增加,过多的消泡剂反而会阻碍水与水泥的接触,抑制水泥水化,并引入 “消泡剂孔”,使得水泥石的孔隙率增大,抗压强度减小。

Abstract:

In the process of cementing mud slurry preparation, ultra-high mixing speeds tend to introduce air bubbles, resulting in difficulties in formulating the cement slurry to the correct density, which in turn can adversely affect the slurry properties and the sealing integrity of the cement ring. In this paper, we take the lipid-based defoamer X60L as an example to investigate the effects of different dosages of X60L defoamer (0%, 0.5%, 1%, and 1.5%) on the compressive strength of oil well cement. Combined with thermogravimetric analysis, X-ray diffraction analysis, X-ray computed tomography test and scanning electron microscope test, we can grasp the changing law of microstructure of cement paste and clarify the mechanism of defoamer"s action on cement paste. The research results show that the compressive strength of cementite shows a trend of increasing first and then decreasing, while the porosity shows a trend of decreasing first and then increasing. Cementite has the lowest porosity and the highest compressive strength when the defoamer dosage is 0.5%. The larger the porosity of cement stone, the smaller the compressive strength, and the compressive strength and porosity were obviously negatively correlated and conformed to Schiller"s function (R²=0.98). The incorporation of defoamer does not change the mineral composition and hydration products of oil well cement, and the defoamer mainly reduces the surface tension of the bubbles, which makes it difficult to maintain the bubbles and thus break them. However, with the increase of defoamer dosage, too much defoamer will hinder the contact between water and cement, inhibit the hydration of cement, and introduce ‘defoamer holes’, so that the porosity of cement stone increases and the compressive strength decreases.