川渝地区“三高”气田超深井固井隔离液应用实践

钻井液和水泥浆的理化性质存在本质差异,超深井固井作业时,二者极易发生化学污染,不但影响顶替效率,而且危及固井施工安全,这在"三高"(高压、高含硫、高危)气田超深井固井作业中尤为突出。为此,针对上述问题,提出了超深井固井隔离液的设计原则和配制工艺,并对相容性实验以及现场施工关键技术进行了深入研究和总结,现场固井实践认为:①隔离液的使用是保障"三高"气田超深井固井作业安全和提高顶替效率的重要举措;②应对隔离液的沉降稳定性与钻井液、水泥浆的化学兼容性予以充分重视,确保隔离液不沉降,对水泥浆的稠化时间无不良影响,防止发生井下复杂情况;③前后隔离液防污染技术可有效防止尾管固井工程事故的发生。隔离液的正确使用可有效地防止化学污染、保证固井作业安全和提高顶替效率。

Application of spacer fluid for cementing ultra-deep walls in Sichuan and Chongqing "three highs" gas fields

Drilling fluid and cement slurry are totally different in physicochemical properties; however, during cementing, if they mix, chemical contamination will easily occur, which will not only affect the displacement efficiency, but also jeopardize the cementing construction, especially during the cementing of ultra deep wells in "three highs" (high pressure, high sulfur content and high risk) gas fields. Thus, in view of these above mentioned problems, design principles and disposition processing are presented for cementing spacer in ultra deep wells, and in depth investigation and summary are made for compatibility tests and key techniques on site construction. The on site cementing practices show that: ①the application of spacer is an important guarantee to improve the displacement efficiency and ensure the cementing safety for ultra deep wells in "three highs" gas fields; ②the settlement stability of the spacer and the chemical compatibility of drilling fluid and cement slurry should be paid full attention to in order to make sure the unsettlement of the spacer and no bad effect on the densification time for the slurry, thus, to avoid complicated downhole accidents; ③the formation damage prevention by use of spacer fluids in succession can effectively prevent the liner from cementing engineering accidents. The proper use of spacer fluid can effectively avoid chemical contamination, ensure the cementing safety, and improve displacement efficiency.