KCl/NaCl/CPI复合盐阳离子聚合物钻井液在南海大斜度井段中的应用

为改善南海东部惠州25-8油田大斜度井因泥岩水化造浆而引起的井壁失稳和钻井液增稠影响携砂的问题,在现有成熟PLUS/KCl钻井液的基础上开展复合盐阳离子聚合物钻井液研究,对钻井液配方进行了优化,评价了优化后钻井液的流变性、抑制性、封堵性和润滑性,并在惠州油田进行了现场应用。结果表明,复合盐阳离子聚合物钻井液配方中,无机盐类抑制剂KCl和NaCl的适宜加量为3%和12%、有机阳离子聚合物抑制剂PF-CPI适宜的加量为2.0%。该钻井液抑制性强,防膨率高达93.32%,钻屑回收率87.56%;受到钻屑侵污后的钻井液流变性能波动小,仍具有较低的黏度和合适的切力,有利于大斜度井携砂;封堵性和润滑性均优于PLUS/KCl钻井液体系。现场应用2口井,钻井液流变性良好,平均起下钻速度提高,钻井过程顺利,无复杂情况发生。复合盐阳离子聚合物钻井液可改善南海大斜度井起下钻阻卡的问题。

Application of Cationic Polymer Drilling Fluid Containing KCl/NaCl/CPI Composite Salts in Highly-deviated Well of the South China Sea

In order to improve the wellbore instability caused by mudstone hydration and slurry-making in Huizhou 25-8 oilfield in the eastern South China Sea,and the sand-carrying problem affected by the thickening of drilling fluid,the development of composite salt cationic polymer drilling fluid was carried out on the basis of existing mature PLUS/KCl drilling fluid research.The formula of drilling fluid was optimized,and the rheology,inhibition,plugging and lubricity of the optimized drilling fluid were evaluated.Finally,it was applied in Huizhou oilfield.The results showed that in the formula of composite salt cationic polymer drilling fluid,the appropriate dosage of inorganic salt inhibitor,such as KCl and NaCl was 3%and 12%,and that of organic cationic polymer inhibitor PF-CPI was 2.0%.The drilling fluid had strong inhibitory property,whose anti-swelling rate was as high as 93.32%,and the drill cutting recovery rate was 87.56%.The rheological properties of the drilling fluid after being invaded by drill cutting fluctuated little.The drilling fluid still had a low viscosity and suitable cutting force,which was beneficial to carry sand in highly deviated wells.Furthermore,the plugging property and lubricity of this drilling fluid were better than that of PLUS/KCl drilling fluid system.When the drilling fluid was applied in two wells on site,the rheology was good,the average tripping speed increased,and the drilling process was smooth without complication.The composite salt cationic polymer drilling fluid could improve the stuck problem of drilling in highly deviated well in the South China Sea.