Page 195 - Geochemical Remote Sensing of The Sub-Surface

172 V.T. Jones, M.D. Matthews and D.M. Richers

Fig. 5-24. Crosspiots of the compositions of gases from offshore Louisiana: (a) well gases
throughout the area; (b) marine sniffer gases throughout the area; (c) marine sniffer gases from a
gas area; (d) marine sniffer gases from an oil area.

Headspace gas

A headspace sampling technique is commonly employed for the analysis of canned
samples from drilling returns and from shallow sediments. In this technique a controlled
volume of sediment is placed in a can or jar filled with a measured volume of degassed
brine. The can is sealed and a measured volume of brine is displaced with nitrogen to
create a known volume headspace. The can is then allowed to come to equilibrium. The
concentration of light gases can then be measured by syringe injection of a headspace
sample into a gas chromatograph equipped with an flame ionisation detector.