且深1井盐层尾管超高温高密度固井水泥浆技术

Extra-High Temperature High Density Cement Slurry for Cementing Liners through Salt Formation in Well Qieshen-1

且深1井是中石化西北油田分公司部署在塔里木盆地塔中地区的一口风险探井,四开中途完钻井深8745.00 m,井底静止温度196℃。针对且深1井四开固井面临的高温、高压、高盐、小间隙和全油基钻井液难驱替等诸多技术难题,围绕水泥浆体系的强度衰退、沉降稳定性、流变性能、稠化时间4个方面展开研究。通过引入富铝材料抑制强度衰退,优选不同粒径加重材料、硅粉调控沉降稳定性,配合耐超高温降失水剂、复配缓凝剂、聚醚-羧酸类分散剂综合调控水泥浆各项性能,设计出一套耐温200℃,密度高达2.3 g/cm^(3)的超高温高密度抗盐水泥浆体系。该水泥浆体系性能稳定,API失水量为44 mL,流性指数n大于0.7,稠化时间线性可调,高温沉降稳定性为0.01 g/cm^(3),1 d和28 d的抗压强度分别为19.2 MPa和27.1 MPa,未见衰退迹象。结合驱油型加重前置液体系和其它固井技术措施,且深1井固井施工顺利。

The well Qieshen-1 is an exploration well deployed by Sinopec in block Tazhong in Tarim Basin.The well was drilled to a depth of 8,745.00 m in four intervals,with static bottom hole temperature being 196℃.Technical difficulties such as high temperature,high pressure,salt formation,narrow clearance between the wall of the hole and the casing string as well as difficulties in displacing the whole-oil based drilling fluid were encountered in cementing the casing string in the fourth interval.To deal with these difficulties,studies were conducted on the strength decay of the set cement and the settling stability,rheology and thickening time of the cement slurry.A saltwater resistant high density(Max.density 2.3 g/cm^(3))cement slurry that is stable at 230℃was developed as a result of the study.Using aluminum-rich materials in the cement slurry,the decay of the strength of the set cement is inhibited.The settling stability of the cement slurry is improved by selecting weighting materials of different particle sizes,and silica fume.Other additives,such as high temperature filter loss reducers,compounded retarders and polyether-carboxylic acid dispersants were used to adjust the properties of the cement slurry to the required levels.Laboratory experiments show that the API filtration rate of the cement slurry is 44 mL,the flow index n is greater than 0.7,the thickening time is linearly adjustable,the high temperature settling stability is 0.01 g/cm^(3),and the 1 d and 28 d compressive strengths of the set cement are 192.MPa and 27.1 MPa respectively,with no signs of strength decay observed.With the use of oil displacing weighted prepad fluid and the adoption of other well cementing techniques,the well Queshen-1 was successfully cemented.