库车山前井防漏固井方法技术研究

Technology for Lost Circulation Control during Well Cementing in Piedmont Wells

由于塔里木油田库车山前地区目的层深、地质条件复杂,导致该地区的井在固井过程中时常发生漏失事故,严重影响固井质量。基于此问题,对整个固井期间产生激动压力的原因进行分析。通过研究钻井液性能、环空间隙、钻具和套管下放速度、排量以及井浆流变性能对激动压力的影响,得出环空间隙越小激动压力越大,建议不得小于20mm;降低钻井液屈服值能减小破坏胶凝结构产生的激动压力;提出了更为合理的套管下放速度计算模型以及提升循环排量频率的概念和控制方法 ;调整井浆的流变性能可以有效降低施工中产生的摩阻,并依此提出了注替排量的计算模型。现场应用表明,该套防漏固井方法对库车山前地区井的防漏设计有指导意义。

Complex formation in the Kuche piedmont structure in Tarim Basin had led to frequent lost circulation, which in turn resulted in poor well cementing job. Factors affecting lost circulation are analyzed, including drilling fluid property, clearance between casing string and borehole wall, running speed of drill string and casing string and pump rate, all factors affecting surge pressure. The clearance between drill string/casing string and borehole wall should not be less than 20 mm. Decrease in the yield point of drilling fluid reduces the surge pressure produced when gel structure of the drilling fluid is broken. A better model is presented for better determination of the running speed of drill string/casing string. A concept of increasing the frequency of pump rate is presented together with the control method. By improving the rheology of the drilling fluid, friction in running drill string/casing string can be reduced. The technology presented in this paper provides a guidance to the lost circulation control design for wells drilled in thepiedmont structure in Kuche Country, Xinjiang.