초록 ▼

Improved methods of drilling well bores utilizing foamed aqueous drilling fluids are provided. The methods basically comprise circulating an aqueous drilling fluid containing a single foaming and defoaming surfactant and a gas downwardly through a rotary drill pipe and drill bit connected thereto. W

Improved methods of drilling well bores utilizing foamed aqueous drilling fluids are provided. The methods basically comprise circulating an aqueous drilling fluid containing a single foaming and defoaming surfactant and a gas downwardly through a rotary drill pipe and drill bit connected thereto. Well bore cuttings generated by the drill bit are lifted to the surface by foam produced from the aqueous drilling fluid and gas. Upon reaching the surface, the foamed aqueous drilling fluid is defoamed whereby the cuttings and gas are removed therefrom and the aqueous drilling fluid is combined with additional foaming surfactant when needed and additional gas. The foaming and defoaming of the aqueous drilling fluid are accomplished by changing the pH of the aqueous drilling fluid from basic to acidic which causes the single foaming and defoaming surfactant to foam and defoam the aqueous drilling fluid.

대표청구항 ▼

1. In a method of drilling a well bore whereby an aqueous drilling fluid and a gas is circulated downwardly through a rotary drill pipe and a drill bit connected thereto and well bore cuttings generated by the drill bit are lifted to the surface by a foamed aqueous drilling fluid produced from the a

1. In a method of drilling a well bore whereby an aqueous drilling fluid and a gas is circulated downwardly through a rotary drill pipe and a drill bit connected thereto and well bore cuttings generated by the drill bit are lifted to the surface by a foamed aqueous drilling fluid produced from the aqueous drilling fluid and gas, the foamed aqueous drilling fluid is defoamed whereby the cuttings and gas are removed therefrom and the aqueous drilling fluid is recirculated, the improvement which comprises the steps of:(a) combining a gas and a single tertiary alkylamine ethoxylate foaming and defoaming surfactant with said aqueous drilling fluid, said surfactant causing said aqueous drilling fluid to foam at an aqueous drilling fluid pH of 10 or above and causing said aqueous drilling fluid to defoam at an aqueous drilling fluid pH of about 5 or below; (b) raising the pH of said aqueous drilling fluid produced in step (a) to about 10 or above when said aqueous drilling fluid is circulated downwardly through said drill pipe and said drill bit so that said aqueous drilling fluid is foamed and readily lifts said cuttings to the surface; (c) lowering the pH of said foamed aqueous drilling fluid to about 5 or below when said foamed aqueous drilling fluid and cuttings reach the surface so that said foamed aqueous drilling fluid is defoamed and said cuttings can be readily separated from said aqueous drilling fluid; and (d) separating said cuttings from said aqueous drilling fluid and repeating steps (a), (b) and (c) until said well bore is drilled to total depth.