Department of Petroleum Engineering, Petroleum University of Technology, Ahwaz, Iran
Fluid invasion from water-based drilling mud (WBDM) into the shale formations causes swelling, high pressure zone near the wellbore wall, and eventually wellbore instability problems during drilling operations. For the stability of the wellbore, physical plugging of nanoscale pore throats could be considered as a logical approach toward avoiding the fluid invasion into the shale formation. This paper reports the effect of silica nanoparticles (NPs) as a physical sealing agent on the water invasion into Kazhdumi shale. To this end, pressure penetration apparatus was implemented. Typical WBDM in contact with Kazhdumi shale at different concentrations of NPs with different sizes was studied. The results indicated that the addition of NPs to the WBDM decreased water invasion into Kazhdumi shale. WBDM having 10 wt.% of 25 nm NPs reduced fluid invasion up to 72.76%.