Several of the design geopressured gas wells developed by the U.S. Department of Energy have produced small amounts of liquid hydrocarbons. At all wells, an unusual, aromatic gas condensate has been collected. This condensate differs dramatically from oil, containing predominantly light aromatic hydrocarbons, with subordinate cycloalkanes, branched alkanes, and normal alkanes. Two of the wells have also produced a paraffinic oil. We have analyzed hydrocarbon liquids produced from the Gladys McCall No. 1 well (Cameron Parish, Louisiana).

We have developed a computer program that models detailed phase relations in the system gas-oil-brine, and have used it to interpret the production of hydrocarbon liquids from Gladys McCall No. 1. We conclude that a single dispersed hydrocarbon phase was present within the producing formation, initially at some distance from the wellbore. The aromatic condensate represents the relatively water soluble hydrocarbons which dissolved in the brine. Prolonged production of brine from the well caused the hydrocarbon phase to move toward the well, ultimately leading to production of oil. Adsorption of of less volatile hydrocarbons on minerals and organic matter retarded their transport in the formation, producing some chromatographic separation of the hydrocarbons in the oil.

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