国外水基钻井液半透膜的研究概述

介绍了近年来国外对水基钻井液半透膜效应机理的研究成果，以及在此基础上对钻井液体系进行的研究讨论。认为，孔隙压力扩散是导致井壁失稳的根本原因，孔隙压力扩散的快慢取决于泥页岩的渗透性、弹性和钻井液与井壁之间物理化学作用等边界条件。通常情况下，渗透率越低，压力增长越慢。只有膜效率高的钻井液体系才能有效控制和延缓孔隙压力的扩散，进而维护井壁的稳定。提高水基钻井液半透膜效率的措施为：①封堵裂缝和高渗透泥页岩的孔隙；②超低剪切条件下增加液相粘度；③降低钻井液活度；④改善泥页岩膜的理想性。并以此为标准，对各类钻井液进行了系统研究，结果发现：MEG钻井液、甲酸盐钻井液、聚合醇钻井液和硅酸盐钻井液具有良好的抑制性和发展前景。

Review of study on semi-permeable membrane of water-based drilling fluid abroad

Study on mechanisms of semi-permeable membrane elticiency ot water-based drilling fiuidd in recent years abroad is presented and some drilling fluid systems are discussed based on the results.It is considered that pore pressure diffusion is an essential reason of wellbore instability, and the diffusion rate depends on mudstone permeability, elasticity and physics/chemistry environments between drilling fluids and borehole wall.In general, pressure increases slowly with permeability decreasing, and only a drilling fluid system with high membrane efficiency can effectively control and delay the pore pressure diffusion.The measures to improve semi-permeable membrane efficiency of water-based drilling fluid are following; a.plugging fracture and high permeable mudstone pore; b.increasing liquid viscosity in condition of ultra-low shearing force; c.reducing drilling fluid activity; d.improving shale membrane performances.All drilling fluid systems have been investigated based on the above measures and results showed that such drilling fluids as MEG, formate, polyol and silicate systems have good inhibition and considerable application prospect.