GEOCHEMICAL STUDIES OF CONDENSATE, GAS AND CORE SAMPLES DERIVED FROM GAS-CONDENSATE FIELDS IN THE MOYNKUM SAG (KAZAKHSTAN)

Abstract

. This paper presents the interpretations of geochemical studies of condensate, gas and core samples from five fields (Amangeldy, Anabay, Ayrakty, Sultankuduk and Zharkum,) of the Moyunkum sag to characterize source rocks and determine the genetic sources of condensates and gas. Based on the results of biomarker analysis, all condensates were generated from shaly lacustrine source rocks with terrigenous organic matter input. The thermal parameters of the biomarkers showed that the condensates of Amangeldy field possess the highest thermal maturity among the studied samples, which is also consistent with the results of the carbon isotopic composition of its gases. Different distributions of biomarkers in the condensates of Ayrakty, Amangeldy, and Zharkum fields may attest to their different genetic origins. All gases have a thermogenic genesis and were generated from a terrigenous source rock (kerogen type III). Ayrakty gases contain relatively high concentrations of nitrogen, although Amangeldy and Zharkum gases have similar nitrogen concentrations. The condensate of well № 4 Zharkum was found to have a different chemical composition indicating its genetic difference from the rest of the condensates of this field. According to the results of Rock-Eval pyrolysis, the studied samples relate to kerogen type III and some of them reached the zone of dry gas generation window, which is also consistent with the result of maceral analysis and Ro value of one sample (Anabai–2779m).