Experimental Investigation of the Effects of Size and Concentration of Nanoparticles on Shale Stability

This paper presents the experimental investigation of the effects of size and concentration of nanoparticles on shale instability. Nanoparticles are added to conventional water-based drilling fluid and are tested on shale to test for its stability. Stability here means the shale will not disintegrate into pieces when in contact with water as the cuttings will cause downhole completion to stuck. Nanoparticles with different sizes and concentrations are used in this experiment to see their effects in providing the best nano-based drilling fluid to enhance shale stability. Shale dispersion is a process by which shale cuttings disintegrate into smaller size usually described as fines. Dispersion of shale cuttings occur when it is in contact with water. It contributes to the wellbore instability as the cuttings have tendency to cause downhole completion stuck. Shale’s dispersive abilities vary depending on the fluid in contact with it. A fluid will successfully inhibit dispersion by preventing the shale from breaking into smaller pieces. In this project, dispersion test were performed to investigate the inhibitive properties of the prepared drilling fluid with the shale samples. The drilling fluid’s ability to maintain the cuttings integrity was analyzed. Thus, at the end of this project, a sample of drilling fluid with good inhibitive property will be concluded. To come out with the correct fluid, the author has used nanoparticle as the inhibitive agent. This is due to its small size, which is said to be effective in plugging the shale pore throat. When nanoparticle successfully plugged the pore, the shale will regain its strength and have fewer tendencies to disintegrate into smaller size. Two different sizes of nanoparticle will be tested in the experiment to check which size is more suitable to plug the shale pore throat. Different concentration of nano-based fluid also been used to determine the correct concentration for the inhibitive properties to be effective. Hot rolled dispersion test has been conducted for this project. Six drilling fluid formulations with different concentration added with different size of nanoparticle have been used. The shale cuttings was hot rolled together with the drilling fluid in a roller oven for 16 hours at 66⁰ C. Based from the hypothesis, shale stability could be reduced to the maximum if it is being hot rolled in 10 wt % and 10-15 nm nanoparticle added nano-based fluid. From the experiment, it is proved that shale dispersion could be reduced in higher nano-based concentration. However, the result does not give convincing value to test for the size variations.