Journal of Petroleum Geology, vol. 19(2), April 1996, pp. 227-234
©Copyright 1996. Scientific Press, U.K. All rights reserved.
CHARACTERISATION OF LOW MOLECULAR WEIGHT
HYDROCARBONS IN FLUID INCLUSIONS FROM FRACTURE-FILLING ANHYDRITE IN THE SOUTHERN NORTH SEA
GASFIELDS
B. McNeil*
Studies of crushing crystals while viewing them under a microscope (
"stage-crushing" studies) were carried out on fracture filling anhydrites from
the Vulcan and Vanguard gasfields in the UK sector of the southern North Sea. These
studies were performed after the appearance of clathrate solids during microthermometric
freezing experiments which indicated the presence of a gas component within the
inclusions. After several attempts at a very difficult analytical technique, a series of
photographs were taken of the process whereby the vapour phase in the inclusions expanded.
This indicated, the existence of a gas under pressure in the inclusions. Gas
chromatographic studies suggested the dominance of methane, and that the overall component
is comparable to that of the southern North Sea gas reservoirs.
