基于四参数流变模式的套管下放速度分析

Casing running speed analysis based on four-parameter rheological model

固井下套管作业中,井底压力平衡与波动压力的大小密切相关。套管下放速度是影响波动压力的主要因素,因此确定合理的套管下放速度,对安全固井具有重要的意义。基于下套管工况,以先进的四参数流变模式为基础,利用窄槽模型,根据井筒流体流动的连续性和相应的边界条件,得出窄槽模型下的环空流量,以此流量与常规模型下得到的流量相等为条件,建立套管最大安全下放速度计算模型。模型验证结果显示,该模型计算的套管安全下放速度与实例井套管下放速度误差在10%以内,表明该计算模型具有一定的精度,可以为现场固井下套管作业提供参考。

During the casing running for cementing, the bottom hole pressure （BHP） balance is closely related to the surge pres-sure. The casing running speed is a major factor infuencing the surge pressure. Therefore, it is essential for safe cementing to ascertain a rational casing running speed. Depending on the casing running conditions, and based on the advanced four-parameter rheological model, a narrow trough model was adopted to obtain the annular fow rate in accordance with the fuid fow continuity in wellbore and corresponding boundary conditions. Then, supposing the obtained fow rate is equal to the fow rate obtained from conventional model, a model for computing the maximal safe casing running speed was established. The verifcation results show that the safe casing running speed obtained by the model only has a less than 10% error to that measured in an actual well. This indicates that the computation model is accurate to certain extent, and it can provide references for the casing running operation on site.