准噶尔盆地北三台凸起石炭系沉凝灰岩生烃潜力分析

Analysis of Hydrocarbon Potential of Carboniferous Tuffite in Beisantai Swell,Junggar Basin

为明确准噶尔盆地北三台凸起石炭系烃源岩的生烃潜力,利用岩石热解、碳同位素和生物标志化合物等地球化学参数,对研究区石炭系沉凝灰岩和暗色泥岩的有机质丰度、类型、成熟度及分布特征进行了对比分析,在此基础上,进行了油源对比分析。结果表明,石炭系暗色泥岩和沉凝灰岩都有较高的有机质丰度,有机质类型以Ⅱ2—Ⅲ型为主,并且都进入了可以大量生烃的成熟阶段。沉凝灰岩主要发育于北三台凸起中部,厚度大,是一套中等—好的烃源岩;暗色泥岩则厚度小,这可能是限制暗色泥岩成为主力烃源岩的主要原因。油源对比分析发现,西泉3油藏石炭系原油来自于石炭系沉凝灰岩,进一步说明这套沉凝灰岩具有生烃和排烃能力,是一套有效烃源岩。

To identify hydrocarbon potential of the Carboniferous source rocks in Beisantai swell of Junggar basin, abundance, type, maturity and distribution of organic matter in Carboniferous tuffite and dark shale in the study area are correlated and analyzed on the basis of geochemical parameters such as rock pyrolysis, carbon isotope and biomarkers, etc., based on which oil-source correlation and analysis are carried out. The result shows that the Carboniferous tuffite and dark shale have relatively high organic matter abundance with organic matter type dominated by Type Ⅱ2-Ⅲ that have entered into the matured phase of large amount of oil and gas generation. The tuffite mainly occurs in the central Beisantai swell and is a set of thick and moderate-good quality source rocks. The dark shale is of less thickness, which may constrain the rock to be the key source rock. The results of oil-source correlation and analysis also exhibit that the oil in Xiquan-3 reservoir is sourced from the Carboniferous tuffite, which can further verify the capability of hydrocarbon generation and expulsion of this tuffite as effective source rocks.