Abstract: A method for the circulation of gas when drilling or working a well. The method includes the step of pressurizing at least two chambers of a multi-chambered accumulator with inert gas. The chambers of the multi-chambered accumulator are operatively connected to one another and individually or in combination isolatable from each other. The method also includes isolating at least one chamber of the accumulator that has been pressurized with inert gas such that during drilling or working the well the isolated chamber remains pressurized with gas that has not been mixed with well gas returns. Pressurized gas is extracted from one or more of the non-isolated chambers of the accumulator and injected into the well. At least a portion of the gas returns from the well is collected, compressed and delivered to at least one of the non-isolated chambers of the multi-chamber accumulator.