新型防塌钻井液体系在苏丹六区储层的应用

Application of a new anti-sloughing drilling fluid system in the Block 6 of Sudan

针对苏丹油田六区储层钻井过程中易于发生井壁失稳、扩径、缩径、取心效率低及起下钻阻卡等井下事故问题,结合苏丹六区储层岩性、孔隙、孔喉及渗透率的特点,基于"理想充填理论"和成膜技术,对具有不同粒径的暂堵剂产品按一定比例进行合理的复配组合,形成了1种新型低伤害防塌钻井液体系,并应用于苏丹六区。实验结果表明,原用钻井液对岩心损害较为严重,新型钻井液所用处理剂均对环境无污染,处理剂没有荧光,钻屑具较好代表性,且容易清洗,能明显提高岩心渗透率恢复值,且可降低钻井液的动滤失量,能有效阻止钻井液中固相颗粒和滤液侵入油气层,满足苏丹六区安全、快速、经济钻井的要求,在钻遇Aradeiba页岩地层过程中得到了成功的应用,具有十分理想的储层保护效果。

Downhole accidents such as borehole instability,hole enlargement,hole shrinkage,low coring efficiency and tripping problem are often seen during drilling process in the Block 6 of Sudan. Based on 'ideal packing theory' and membrane-forming technology,a new low damage anti-sloughing drilling fluid system has been developed and applied in the Block 6 of Sudan by blending temporary plugging agents of different grain sizes in certain proportion according to reservoir lithology,aperture,pore throat and permeability. Experiment result shows that the original drilling fluid has severely damaged the core; the new drilling fluid uses treatment agents uncontaminated to environment and without fluorescence,and the cuttings are better representative and easy to clean. The new drilling fluid can significantly improve the return permeability of core sample,reduce the dynamic filtration rate,effectively prevent solid particles and filtrate from entering reservoir,and meet the requirements of safe,fast and economic drilling in the Block 6,Sudan. This new drilling fluid system has been successfully used in drilling the Aradeiba shale formation and achieved very satisfactory effect of reservoir protection.