关键词: 深部巨厚盐层, 损伤机理, 扩容损伤边界, 井壁稳定性, 钻井液密度, 设计方法

Abstract: In order to prevent stick accidents caused from plastic deformation of salt-bed creep during drilling,the density of drilling fluids in salt formation is commonly calculated using the established constitutive equation and the parameters obtained from experiments,which cannot meet the real requirement of drilling fluid.A new approach for controlling the dilatancy damage and deformation at the nearside of borehole was presented and used to calculate the density of drilling fluid for deep big-thickness salt formation.The acoustic emission signal generated from salt rock damage and deformation was analyzed in laboratory to determine the dilatancy border in the damaged salt-formation.The borehole of deep salt formation is stable only when the octahedral shear stress is below the dilatancy boundary.A comparison of the density of drilling fluid designed by the new method with that of the real drilling indicates that the density window for designing drilling fluids can be simply and effectively applied in the course of drilling in the big-thickness salt formations.

Key words: deep big-thickness salt formation, damage mechanism, dilatancy damage border, borehole stability, density of drilling fluids, design method