Influence of (3–Aminopropyl) triethoxysilane on entrapped polypropylene at nanosilica composite for shale swelling and hydration inhibition

The unforgiving shale formations require special shale inhibitors to mitigate wellbore instability problems. (3–Aminopropyl) triethoxysilane polypropylene-nanosilica composite (PNSC + NH2) was evaluated in water-based drilling muds (WBDMs) as a clay swelling and hydration inhibitor. The size distribution, functional groups, morphology, and thermal stability of the PNSC + NH2 were studied. Rheological and filtrate volume tests were carried out to determine the influence of the PNSC + NH2 on WBDMs. The clay swelling inhibition performance of the PNSC + NH2 mud system was examined and compared with that of potassium chloride (KCl) and KCl + partially hydrolyzed polyacrylamide (KCl + HPAM) through clay swelling inhibition test, extended clay swelling inhibition test (inhibition longevity test), and BET analysis test. Four shale specimens were prepared with compactor cell for the measurement of clay swelling using the Linear Swell Meter. Drilling muds were examined on 16 mm thick-compacted shale pellets using the highest concentration of smectite. A shale rolling recovery test was conducted to determine the shale hydration-retardation. Results showed that the PNSC + NH2 particle has good dispersibility, with a size distribution predominantly distributed between 80 and 390 nm. The inclusion of 1.5w/v% PNSC + NH2 concentration enhanced the plastic viscosity and yield point of WBDM from 11 to 15 mPa s and 9–14 Pa, respectively. Also, it reduced the API filtrate volume of the WBDM from 10.2 to 7.8 ml. The clay swelling inhibition performance of the WBDM for 36 h showed 62% swelling and was reduced to 42% by KCl, 33% by KCl + HPAM, and 28% by PNSC + NH2. When the inhibition test was extended to 60 h, the swelling increased to 44% for KCl, 40% for KCl + HPAM, and 29% for PNSC + NH2 mud systems. These results revealed that the PNSC + NH2 has the best inhibition performance due to its ability to provide the greatest long-lasting inhibiting effect on the clay surface. When the shale cuttings with the various mud systems were subjected to 150 °C for 16 h in an ageing steel cell, the shale recovery rate at 1.5w/v% concentration confirmed that the PNSC + NH2 exhibited 75.3 wt%, while that of the base mud, KCl, and KCl + HPAM systems demonstrated 33.6, 58.4, and 63.1 wt%, respectively. The BET surface area of the shale reduced significantly by 52.3% with 1.5w/v% PNSC + NH2 from 14.72 to 7.02 m2/g. The wettability determination of the shale surface showed a contact angle of 36.8° which improved to 68.4° by 81.0% with 2.0w/v% PNSC + NH2 concentration. The application of PNSC + NH2 for clay swelling and hydration inhibition proved to be promising and could be effective for drilling shales