Experimental Research of Gas Hydrate Drilling Fluids Using Polyethylene Glycol as an Inhibitor

Low temperature is the key for maintaining the wellbore stability of the gas hydrate well and for ensuring the safety in the well. In this article, the characteristics of drilling in the permafrost containing gas hydrates are analyzed initially. And later, the relative properties and the inhibitory mechanisms of the polyethylene glycol and the hydrate inhibitor of the drilling fluids ensuring drilling safety are discussed. On the basis of these, the effects of the molecular weight and the content of the polyethylene glycol, and its interaction with the salts on the performances of the four groups of drilling fluids under low temperature are mainly analyzed. The results of these analyses show that for the relative drilling fluid system, the 5% content of polyethylene glycol with a molecular weight of 10 000 combined with 15% NaCl+5% KCl or 20% NaCl is suitable.