关键词: 超低渗透钻井液, 防塌机理, 承压性能, 油层保护, 井壁稳定性

Abstract:

The different experiments were used to investigate the interaction mechanisms of ultra-low permeable drilling fluid for stabilizing the borehole wall in microcosmic and macroscopic aspects,including visible sand-bed penetration,pressure transportation,adsorption,SEM,high resolution microscope and pressurization of mud microstructure.It was found that the ultra-low permeable agent YHS-1 could be rapidly adsorbed on the borehole wall,and the adsorption capacity of the agent was great.The results of SEM and high-resolution microscope experiments showed that YHS-1 could form a tight micelle membrane between the surface of borehole wall and the front of mud cake.The tight micelle membrane could enter the shallow rocks and be easily removed.The shale inhabitation and pressure transmission experiments confirmed that the drilling fluid system could effectively reduce the transmission rate of pore pressure,inhibit the expansion of shale particles and also effectively prevent borehole wall from collapse.The soft micelle membrane could form a thin non-permeable sealing layer,which could distinctly enhance the pressurization performance of drilled formation.The ultra-low permeable drilling fluid has good performances,such as reservoir protection,stabilization of borehole wall and obvious leak resistance.

Key words: ultra-low permeable drilling fluid, anti-collapse mechanism, pressurization performance, oil reservoir protection, borehole wall stability