Investigating the influence of rutile-Tio2 and MWCNTs composite on shale swelling and mechanical properties

Abstract

Efficiency of drilling fluid is the foremost step in the success of any drilling activity. Real-time surveillance of the properties of a drilling mud significantly impacts the efficiency and wellbore integrity. In this article, a crystal structure of TiO₂ explicitly rutile was composited with multi-walled carbon nanotubes (MWCNTs). The limitations associated with TiO₂ and MWCNTs such as high energy gap, rapid kinetics, agglomeration and dispersion substantially reduces once they are linked together, which eventually impacts the stability and properties of drilling fluid. Nevertheless, the specific crystal structure of TiO₂ demonstrates inherent shortcoming stemming from its structural characteristics. To test the efficacy of the particles in the drilling mud, five mud samples with concentration of nanoparticles ranges between 0.35 and 3.5 g were prepared and investigated for the shale stability. These five samples were tested on the most problematic Ranikot shale gathered deep down from the Indus Basin. Excessive moisture content in the shale was the main factor that contributes heavily to the severe wellbore instability issues. According to the study results, it was observed that MWCNTs/rutile-TiO₂ exhibited higher fluid loss volume. Moreover, MWCNTs/rutile-TiO₂ mud started to dephase at a rapid pace, and completely loses its stability within 6 h of experimentation. The crystal structure of rutile, specifically its large grain size and low porosity, contribute to a decrease in surface area, thereby destabilizing the system. Furthermore, when the Ranikot shale pellets were exposed to MWCNTs/rutile-TiO₂ mud in immersion testing, they were either completely broken down in pieces or suffered significantly from cracks and fracture. In addition, sample in linear dynamic swell meter also demonstrated high water intake with higher swelling behavior of 14.1% after 24 h. Also, the shale dissolved point was achieved at the 16 h of experiment. An earlier shale dissolved point will create problems like stuck pipe, caving, washouts and high cutting concentration within the wellbore. This will eventually impact the equivalent circulating density within the borehole.