Online Gas Analysis

Continuous mud gas loggings during drilling as well as offline mud gas sampling are standard techniques in oil and gas exploration, where they are used to test reservoir rocks for hydrocarbons while drilling.

Online Gas Monitoring at SAFOD


ICDP’s Online Gasmonitoring OLGA extends this technique for scientific drilling in hydrocarbon and non-hydrocarbon formations to sample and study the composition of crustal gases [1]. Online-Gasmonitoring of drilling mud is a three-step process, comprising:


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Gas extraction at the surface

Back at the surface, a portion of the circulating mud is admitted to a mud gas separator and gas dissolved in the drilling mud is extracted mechanically under slight vacuum. The separator is composed of a steel cylinder with an explosion-proof electrical motor on top that drives a stirring impeller mounted inside the cylinder. The gas separator is installed as close as possible to the outlet of the mudflow line, either in the "Possum belly" above the shaker screens or in the mud ditch, in oder to minimize air contamination and degassing of the drill mud before gas extraction. A small membrane pump is used to build up vacuum and to pump the extracted gas into a laboratory trailer, which should be installed not more than a few tens of meters away from the gas separator.

Sketch of the OLGA system