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Abstract: The Application of Semi-Permeable Membrane Technology in the Measurement of Hydrocarbon Gases in Drilling Fluids


The paper describes the technology of using semi-permeable membranes to measure the amount of hydrocarbon gases entrained in the drilling fluid. The membrane technology signifies a new generation of mud logging devices that measure either single main component (C1), or individual gas components using chromatography. Experimental data is presented from the analysis of dissolved hydrocarbons (C1-C5) in various drilling fluids (fresh water, water base, oil base, invert emulsion and mineral oils). The new technology is based on a physical principle of the partial pressure differential of hydrocarbon gases across the membrane wall. This has several benefits over classical techniques of gas sampling such as mechanical agitation (gas trap) or stills (steam or microwave). These include improved linearity, easy calibration to determine percent dissolved gas by volume, better extraction of heavier components (C3 to C5) with a superior ratiometric relation to the actual composition, faster response time and improved depth resolution.The probe can be installed anywhere in the surface circulation system leading to several new application such as air drilling, underbalanced drilling, differential mud logging (suction and flow line installation) and monitoring of degasser efficiency. The semi-permeable membrane has great potential to advance gas measurement technology in drilling fluids permitting installation flexibility and allowing application in areas where conventional gas sampling falls short. Direct quantitative measurements of gas in mud and the ability to calibrate directly in the fluid used also contribute to the value of this technique.

AAPG Search and Discovery Article #90911©2000 AAPG Pacific Section and Western Region Society of Petroleum Engineers, Long Beach, California