理想充填暂堵钻井液室内研究

钻井过程中,传统的暂堵方法主要是依据储集层的平均孔喉直径优选暂堵剂的颗粒尺寸,因此难以有效封堵对油气层渗透率贡献很大的那部分较大尺寸的孔喉.中高渗砂岩储集层一般具有渗透率分布范围广、孔隙度大和孔喉尺寸分布范围大的特点,且常以泥质胶结为主.中高渗砂岩储集层损害的主要机理是钻井液中固相颗粒和滤液的侵入以及黏土的水化膨胀和分散.在优化聚合物钻井液的基础上,采用了理想充填暂堵技术,用动态岩心污染实验仪进行了评价.实验结果表明,原有钻井液对岩心损害较为严重,优化后钻井液能明显提高岩心渗透率恢复值,进一步采用理想充填暂堵技术可以明显降低钻井液的动滤失量和最大突破压差,提高岩心渗透率恢复值,从而减轻储集层损害.图5表3参12

Laboratory study of ideal packing approach applying to high permeability sandstones

It is difficult for conventional temporary bridging methods to seal large pore throats which usually make the dominant contribution to permeability. The reason is that the particle size of conventional bridging agents is optimized depending on the median pore size of target formation. High-permeability sandstone reservoirs have such features as wide permeability distribution range, great porosity, argillaceous cement, and wide distribution range of pore throat sizes. The key factors of reservoir damage are invaded particles and filtrate of drilling fluids, as well as the hydrate expansion and dispersion of clay. The KPAM polymer drilling fluids are optimized, ideal packing approach is applied to the drilling fluids, and the instrument of dynamic fluid loss test is used to evaluate return permeability. The test results indicate that the ideal packing approach can reduce the dynamic fluid-loss, improve the return permeability, and reduce breakthrough pressure.