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Abstract

Described herein are a method and apparatus for analyzing a gas sample that is conveyed in a drilling fluid, and a method and apparatus for liberating gases from drilling fluid. The gas sample contains one or more of methane, ethane, propane, and butane; optionally, the gas sample may also contain pentane. The gas sample is first liberated from the drilling fluid, following which it is irradiated with infrared radiation in the near-infrared range. Absorption spectra resulting from absorption of the infrared radiation by the one or more of methane, ethane, propane and butane is simultaneously detected. From the absorption spectra, the composition of the gas sample can be determined. The composition includes a concentration of any one or more of the methane, ethane, propane and butane. Linearity of absorption is increased by using relatively short wavelength infrared radiation centred on, for example, about 1.70 μm, which can increase the accuracy of and reduce the computational intensity of the calculations utilized to determine the composition of the gas sample. Within the near-infrared range, radiation having a wavelength from about 1.55 μm to 1.85 μm can be used. Gases can be liberated from the drilling fluid using a gas trap. The gas trap can be powered using a brushless DC motor, and alternatively or additionally drilling fluid from a sample enclosure of the gas trap can exit via a bubbler enclosure of the gas trap. The brushless DC motor is a relatively efficiency and compact motor that can be used with the gas trap, and is advantageous over convention AC induction and air motor motors. Having drilling fluid exit the sample enclosure through the bubbler enclosure is advantageous in that it helps to make the footprint of the gas trap relatively small.

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First Claim