QHD32-6-3井明化镇组原油非均质性及其石油地质意义

原油甾、萜烷的分布表明 ,QHD32 6 3井明化镇组不同油组的原油来自相同生烃层系 ,但各油组原油色谱特征及芳烃系列化合物组成具有明显的差别。色谱特征的差异主要是第 2期油气的不均衡充注造成的。NmⅠ 油组原油正构烷烃与 2 5 降藿烷共存 ,说明本油组油藏接受了 2期原油注入 ,早期注入的原油遭受了生物降解 ,而后又接受了后期热演化程度较高原油的注入 ;NmⅡ 和NmⅣ 油组原油正构烷烃的缺失及 2 5 降藿烷的检出 ,表明其也遭受了强烈的生物降解 ,但第 2期油气对NmⅡ 和NmⅣ 油组没有影响。芳烃化合物组成的差异是由于各油组生物降解的程度不同所致。NmⅡ油组原油强烈的生物降解与水体的活动有关 ,由此推测其油藏可能为底水油藏 ,而不是以往所认为的边水油藏。

Minghuazhen oil heterogeneity in QHD32-6-3 well and its significance in petroleum geology

The distribution of steranes and terpanes in oil from Minghuazhen Formation in QHD32?6?3 well has shown that all oil layers have the same source rocks, but are quite different in gas chromatograms and aromatic compositions. The chromatogram differences may mainly result from an inhomogeneous charge of second phase hydrocarbon. The coexistence of n_alkane with 25_norhopanes in oil from NmI layer indicates that there are charges of second phase oil. In other words, the early charged oil has subjected to a severe biodegradation, and then a charge of higher matured oil occurs in NmI layer. Absence of n_alkane and occurrence of 25_norhopanes in oil from NmII and NmIV layers may imply that these layers also have a severe biodegradation, but no effects of second phase hydrocarbon. The difference in aromatic compositions could be caused by differential biodegradations in different oil layers, and the severe biodegradation in NmII layer may be related to the oxygenated water activities. Therefore, the NmII layer can be deduced as an edge_water reservoir, instead of a basal_water reservoir considered before.