Study and Performance Evaluation of a Glycerol-Based Drilling Fluid System with Strong Inhibition and High Lubricity

To address the problems of oil-based drilling fluid, such as environmental pollution, complex environmentaltreatment process and impact on logging quality, a glycerol-based drilling fluid suitable for strong water sensitive strata was developed for low-carbon alcohols strong inhibition, high lubricity and miscibility with water in any ratio. The swelling rate of bentonite in low-carbon alcohols solution for 24 h was investigated, and glycerol was selected as the optimal inhibition lubricant. The higher the volume fraction of glycerol, the better the inhibition, lubricity and viscosity of glycerol solution. In order to reduce alcohol consumption and further improve the inhibition, a glycerol-based drilling fluid system was formed by using 30% glycerol mixed with 5% KCl. The results of the performance evaluation show that the inhibition and lubricity of glycerol-based drilling fluid system are similar to those of oil-based drilling fluid, with temperature resistance of 140 ℃ and antipollution of NaCl, CaCl₂ and drill cuttings. After six months of storage, the drilling fluid has achieved stable performance and can be reused. The inhibition and lubricity of drilling fluid can be further improved by increasing the dosage of glycerol. Glycerol-based drilling fluids can be used in strong water-sensitive stratum or with high requirement of lubricity. It shows a great application potential and this study also provides a development trend in environmental friendly drilling fluids.