Supramolecular porous-based phase change material based on cucurbit[7]uril complexed amino-montmorillonite

Abstract

Under high-temperature conditions, drill bits, downhole guiding tools, etc. are susceptible to failure, so capturing and storing the heat energy generated is critical for efficient drilling. In this work, a porous material of cucurbit[7]uril (CB[7]) complexed amino-montmorillonite (NH2-MT) was proposed for the first time to encapsulate eutectic nitrate (NIT) to alleviate the high-temperature crisis in the drilling process. The results showed that the structural stability and anti-leakage performance of the supramolecular composite phase change materials (MAC@NIT) were significantly improved by the addition 0.25 g of CB[7], and the adsorption of Na+ and K+ by CB[7] was in the form of monolayer adsorption. The phase change temperature and structure of MAC@NIT-2 remained stable after 200 cycles, and the maximum change of latent heat of solid-liquid was only 3.96 J/g. The special cavity structure of CB[7] further enhanced the thermal conductivity of the MAC@NIT, up to 0.48 W/m·k, which was 20 % higher than the MT@NIT. The addition of MAC@NIT improves the stability of the drilling fluids by 15 %. Additionally, the temperature of the drilling fluids could be reduced by 4.3 °C at a low solid-solid latent heat value. In summary, this study provides ideas for developing ultra-deep oil and gas resources efficiently.