The Experimental Study on a New Type Low Temperature Water- based Composite Alcohol Drilling Fluid

Based on the characteristics of gas hydrate bearing permafrost in western China, and the application of alcohols drilling fluid, the performances of composite alcohol drilling fluid composed by polyethylene glycol and propylene glycol at low temperatures were comprehensively studied in this paper. The results show that the composite alcohol drilling fluid has a reasonable density, good low-temperature rheology, lubricity, shale hydration inhibition and hydrate formation inhibition, which can effectively inhibit shale expansion in a long time, and prevent hydrate formation from a small amount of free gas released from gas hydrate decomposition around the wellbore in the circulation of drilling fluid. Therefore, the composite alcohol drilling fluid has great significance for safe and high efficiency drilling in the permafrost gas hydrate bearing formation.