吐哈油田抗盐水泥浆固井技术研究与应用

吐哈油田的雁木西、神泉、葡北等地区含多段盐膏层,均属可溶性和可塑性地层,易溶解、水化膨胀,造成井径不规则或形成大小井眼,若发生塑性流动,将会使套管受到不均质载荷,引起套管变形,影响油井寿命,给固井带来诸多难题。通过对水泥浆体系配方的优选和性能的研究,开发出了抗盐水泥浆体系。该水泥浆具有抗盐性好、低失水、稠化和凝结时间短、稠化时间可调节范围大、与早强剂等外加剂配伍性好、流动性好、易达到紊流顶替、浆体稳定、强度高等特点。现场应用表明,抗盐水泥浆体系既保证了盐膏层固井的施工安全,又提高了固井质量,特别是解决了第二界面的固井质量问题,为油田的持续改造奠定了良好的基础。

Research and Application of Salt-resisting Cement Slurry in Tuha Oilfield

There are sets of salt-gypsum beds in Yanmuxi, Shenquan and Pubei blocks of Tuha Oilfield. The salt-gypsum beds are characterized by being water soluble and plastic. They are easy to dissolve, hydrate and swell in contact with water, resulting in irregular borehole and plastic flow. Plastic flow of the salt-gypsum beds may generate heterogeneous stresses on casings, causing them to deform and hence negatively affect the service life of an oil well. Based on the optimization of the cement slurry formulation and study on cement slurry properties, a salt-resisting cement slurry was developed. The new cement slurry was salt-resistant and had a low fluid loss. Other advantages include; the thickening time and setting time were short, the thickening time could be adjusted in a wide range, the slurry was compatible with other additives such as early strength agents, it had good flow properties, it was easy to achieve turbulent-flow displacement, and so on. Field application showed that the cement slurry not only satisfied the needs for safe operation in salt-gypsum formations, it also improved the cementing quality, especially in cementing quality of the second interface (the interface between cement and formation).