磨溪-高石梯构造超深定向井固井水泥浆技术

磨溪-高石梯构造下部地层尾管固井面临固井质量差的难题,主要表现为:大斜度、水平井顶替效率不高,平均仅为92.7%;尾管封固段长,环空间隙小,固井候凝易出现气窜;钻井液、隔离液和水泥浆的密度及流变性能匹配性差;上部井段油气水活跃,易发生油气水窜。以工区工程地质特征为基础,优选出适用于高温高压大温差且气层发育条件下的宽温带缓凝剂和高温降失水剂,并以此为基础研发出了适用于高温高压大温差条件下的防窜水泥浆体系,该体系在高温165℃养护24 h和低温65℃养护24 h的抗压强度能达到29.5 MPa和14.0 MPa以上。同时,在大温差、水泥浆体系在保证水泥浆胶结良好的情况下(地层压力梯度小于2.0),能有效防止气窜发生,具有良好的抗温稳定性和防窜性能。现场应用表明,固井质量优良率提高约30%,评价合格率提高超过50%,固井后无一口井发生气窜或气测异常。该技术能够显著提高磨溪-高石梯工区的尾管封固质量,为龙王庙气田的安全经济高效开发提供保障。

Cement slurry optimization for ultra-deep directional well in Moxi-Gaoshiti structure

Liner cementing engineer is faced with problem of poor cementing quality in lower part of Moxi-Gaoshiti structure,which has features of lower displacement efficiency of deviated and horizontal wells with an average of 92.7%;gas invasion occurs easily during waiting on cemented due to long sealing section of liner and small annulus clearance;the compatibility of density and rheology of drilling fluid,isolation fluid and cement slurry is poor;the upper well section is active and prone to oil-gas-water channeling which leads to gas-water invasion challenges.In this paper,based on the engineering geological characteristics of the area,the wide temperate retarder and high temperature water reducing agent are optimized,which have high temperature,high pressure and large temperature difference under the condition of gas reservoirs development,and on this basis,the anti-channeling cement slurry system is developed,which is suitable for high temperature and high pressure and large temperature difference conditions.The slurry compressive strength can reach more than 14 MPa to 29.5 MPa by curing within 24 h under 165℃and 65℃,and at the same time,the slurry has good anti-temperature stability and anti-channeling performance under large temperature difference.The slurry can also effectively prevent the gas channeling under the condition of good cementing quality(formation pressure gradient is less than 2.0).After field application,the rate of excellent and good cementing quality has increases by approximate 30%,and the rate of qualified evaluation increases by more than 50%.The high temperature,high density and large temperature difference anti-channeling cement slurry can significantly improve sealing quality of liner casing in the Moxi-Gaoshiti area,which provided guarantee for the safe,economical and efficient development of Longwangmiao gas field.