A METHOD FOR MEASURING COALBED METHANE CONTENT IN COAL STRATA WITHOUT THE LOSS OF THE GAS

摘要

This paper describes an invented method for direct measurement of coalbed methane content in situ. In contrast to known procedures, this method does not need to place a rock or drilling cuts into an airtight canister, and does not involve sealing of the hole. Moreover, the new method is monitoring methane content in situ continuously and synchronously during drilling the hole not losing any portion of the gas. These positive features are a sequel of new approach based on injection of known portion of neutral gas into the hole. Methane content was determined from concentration of the mixture 'methane-neutral gas' at the hole's mouth. New method is applicable for commercial recovery application of coalbed methane and forecast of dangerous gas and coal bursts. FLAC3D computer simulation helped to investigate dynamics of methane outflow from the hole to account for the effect of drilling speed on the rate of gas emanation.