钻井液和泥页岩间的传递作用对井壁稳定的影响

AN INFLUENCE OF THE TRANSFER FUNCTION BETWEEN DRILLING FLUID AND MUD SHALES ON BOREHOLE WALL STABILITY

钻井液和泥页岩接触后必然会发生一系列复杂的传递和相互作用，分析研究它们间的传递和相互作用及其对井眼稳定性的影响有助于认识泥页岩井壁失稳的机理，有助于设计新的和完善旧的防塌钻井液体系，从而更好地解决泥页岩井段井壁失稳问题。在分析钻井液和泥页岩间的传递作用及其机理的基础上，详细分析了传递作用对井壁稳定的影响。认为钻井液和泥页岩间通过扩散、对流和渗透三种机理而发生水分子和溶质的传递，水力压差和化学势差是主要的驱动力由化学势差产生的渗透压力的驱动具有瞬变特征。钻井液和泥页岩间的传递作用通过改变页岩与流体间相互作用、改变地层孔隙压力，改变近井壁页岩含水量和胶结完整性等途径而影响井壁稳定。

While the drilling fluid is in contact with the mud shales,a series of complicated transfer and interaction will happen.To analyze them and their influence on borehole stability is conducible to recognizing the mechanism of causing the mud shale wall instability,to designing the new sloughingprevention drilling fluid system and to improving the original one,so as to solve the problem about the mud shale wall instability.On the basis of analyzing the transfer function between drilling fluid and mud shales and its mechanism,the influence of the transfer function on the borehole wall stability is discussed in detail.It is considered that the water molecule and solute transfer between drilling fluid and mud shales occurs by means of three mechanisms as diffusion,advection and osmose;the hydraulic pressure difference and chemical potential energy difference are the major driving forces;and the osmotic pressure derived from the chemical potential energy difference is of a transient nature.The borehole wall stability can be influenced by the transfer function between drilling fluid and mud shales through these ways of changing the interaction between shales and pore fluid,the formation pore pressure and the water content and cementation integrity of the shales near borehole wall.