Graphene-enhanced wellbore cement: improving cement performance in the construction of geothermal wellbores

摘要

Graphene is a 21st Century super material that continues to break the ceiling in the materials world, and in this study, we investigate the impact of graphene on properties of wellbore cement and how it may impact its performance. The wellbore cement is a less known composite of Portland cement than widely used concrete, but it often endures much harsher subsurface conditions, mainly high temperature, and pressure. The objective of this study is to add natural high-grade graphene with carbon content ～92.8 wt% and natural oxygen of ～7.0%, different from graphene oxide (carbon ranges from 41.5-72.6 wt% and Oxygen 17.7 to 52.3), to wellbore cement and assess its effects on hydration products and microstructural properties. Electron microscopy was used to determine the structure and morphology of graphene and EDS to assess the chemical content and its impact of graphene on cement hydration products. 0.1% and less of graphene was added to class H cement (16.4 ppg enhanced) in preparation of cement core samples that were cured for 21 days, at 90°C, and 95%RH. Microstructural characterization was performed on fractured and polished surfaces. Results indicate graphene cement porosity reduction by 4.5% and permeability decrease by 35% with 0.05%woc of graphene, with also 0.1%woc increasing cement shear strength by 20% compared to neat cement, 0%woc graphene.