Geochemical Characteristics and Hydrocarbon Accumulation Mechanism of Mixed Oils in Subei Basin

Abstract

Abstract: Oils in Jinhu sag are characterized by the typical immature-low mature, and some compounds with low thermal stability are identified. Carbon number preference index, odd-even predominance and hopane maturity show little difference of maturity between the oils. But the variation of sterane isomerisation parameter and source analysis indicates hat four migration and accumulation patterns with different maturities can be classified. Quantitative analysis shows that different percentage of immature oils is mixed with normal oils in Jinhu sag. The condensate associated with natural gas in Yancheng sag suggests both similarity and difference with lacustrine oils and marine oils. The light compositions of condensate are presented high mature, while the middle compositions assume immature to low mature and the heavy compositions show mature. The pattern of hydrocarbon accumulation with sources in lower strata and reservoirs in upper ones allows the mature oils to be scrubbed by the high mature gas, which appears the special feature of gas condensate.

Key words: Subei basin, oil source correlation, geochemistry, maturity, mixed base crude

CLC Number:

TE112.1

CHEN Qing-chun, CHANG Xiang-chun, GUO Hai-hua, PANG Ling-yun, SONG Zhen-xiang. Geochemical Characteristics and Hydrocarbon Accumulation Mechanism of Mixed Oils in Subei Basin[J]. Xinjiang Petroleum Geology, 2007, 28(5): 545-548.

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