ABSTRACT

A brief discussion of prior mud logging methods is given, followed by the requisite for the quantitative measurement of hydrocarbon constituent gases in the mud stream and drill cuttings. A description of the various spectroscopic tools, principle of operation, and adaptability to logging requirements is presented; included are infra-red cells, mass spectorometry, and gas chromotrography. Examples of gas anomalies are presented which are descriptive of gas, gas-condensate, and oil productive horizons. The fundamentals of anomalies interpretation, and the use of the method as an evaluation and exploratory tool is discussed.

Advantages claimed for the method are material increase in gas detection sensitivity tending to preclude reservoir penetration without show; full quantitative recording range from detectability to maximum concentration, thus elimination of show loss due to high gas content; selective recording of specific hydrocarbons which prevents false show testing; and quantitative and qualitative constituent gas analysis providing the basis for interpretation of fluid flow, that is, gas, condensate, or oil.

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