论文部分内容阅读
顶替效率及界面稳定性是海上大位移井固井顶替能否成功的关键因素。应用计算流体力学理论,结合南海一口大位移井固井基础资料,通过数值模拟得到了水泥浆流变性以及不同井眼情况对固井顶替效率的影响规律。计算结果表明:增大水泥浆稠度系数,顶替效率增加;增大水泥浆流性系数,顶替效率减小;固井顶替效率随着屈服应力增加先增大后降低,最终趋于稳定;固井时水泥浆的流性指数不宜过高,n值应控制在0.6以内;稠度系数应大于1.5Pa·sn,不应超过3Pa·sn;屈服应力在10~18Pa的范围区间,有利于水泥浆顶替钻井液。偏心度对界面稳定性影响很大,建议将偏心度控制在0.5以内;使用套管扶正器,界面的稳定性明显改善,优选出最佳刚性扶正器旋流角为60°;套管屈曲对界面稳定性的影响显著,使环空界面的顶替效率明显降低。
Substitution efficiency and interface stability are the key factors in the success of offshore cementing displacement wells. Based on the CFD theory and the cementing data of a large displacement well in the South China Sea, the rheological properties of cement slurry and the influence of different wellbore conditions on displacement efficiency of cementing are obtained by numerical simulation. The calculated results show that increasing the consistency coefficient of cement slurry increases displacement efficiency; increasing fluidity coefficient of cement slurry decreases replacement efficiency; displacement efficiency of cementing increases first and then decreases with the increase of yield stress, finally stabilizes; cementing When the flow index of the slurry should not be too high, n value should be controlled within 0.6; consistency coefficient should be greater than 1.5Pa · sn, should not exceed 3Pa · sn; yield stress in the range of 10 ~ 18Pa, is conducive to the replacement of cement slurry Drilling fluid. The eccentricity has a great influence on the stability of the interface. It is suggested that the eccentricity should be controlled within 0.5. With the casing centralizer, the stability of the interface is obviously improved. The optimum rigidizer centralizer swirl angle is 60 °. The influence of interface stability is significant, so the replacement efficiency of annulus interface is obviously reduced.