Method and apparatus for detecting gas conveyed by drilling fluids

摘要

A method of detecting gas conveyed in a drilling fluid (M) returning from a well (26), which method comprises the steps of: (a) extracting gas from said drilling fluid (M); (b) transmitting infra-red radiation through said gas; and (c) detecting with a detector (50) infra-red red radiation that has passed through said gas and providing an output signal representative thereof; characterised by the step of: (d) examining the intensity of a portion of the infra-red spectrum within a range of approximately 3.1žm and 3.6žm to estimate whether or not said gas comprises any light or heavy hydrocarbons.