engleski

Diamondoid Hydrocarbons as Maturity Indicators for Condensates from Drava Depression, Croatia

Diamondoid hydrocarbons have been investigated in gas-condensate reservoir from Drava Depression, Croatian part of Pannonian Basin, in order to define thermal maturity of condensates. This fields are largest gas and gas-condensate fields in Croatia - Molve, Kalinovac and Stari Gradac, located in the northern part of Drava Depression. The complex structural, lithological and stratigraphical features of this area resulted in specific physical characteristic of finding hydrocarbons fluids. Origin and maturity parameters of condensate were investigated and correlated based on gas chromatography (GC) and gas chromatography-mass spectrometry (GC/MS) techniques. Based on GC analysis of gasoline fraction as well as “whole” condensate fraction, it is assumed that the hydrocarbons are either produced by mixing condensate with dry methane or as a result of different post-generative process. Diamondoids are generally more stable than any other hydrocarbon class in geological samples and once formed, are resistant to alteration processes like biodegradation and maturation. Because of these properties, diamondoids have been used in evaluating geochemistry process like biodegradation and thermal maturity of high maturity crude oils and condensates. Diamondoid hydrocarbons were determined using gas chromatography-mass spectrometry in different concentrations. The value of diamondoid based maturity parametars, like methydiamantane index 40-50% indicate high level of thermal maturity corresponding to vitrinite reflectance 1.1-1.6%. No biodegradation is observed in any of these samples as shown by high value of API gravity, absence of UCM and methydiamantane/diamantine index.

dimondoids, maturity, condensate

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