辽中凹陷古近系烃源岩特征及有机质丰度控制因素

Characteristics of Palaeogene Hydrocarbon Source Rocks and Controls on Its Organic Matter Abundance in Liaozhong Sag

根据烃源岩地球化学特征、岩石学特征和沉积学特征,分别从有机质丰度、类型、成熟度等方面综合评价了渤海湾盆地辽中凹陷古近系沙河街组、东营组三段和东营组二段下亚段的富有机质泥岩,并分析其生烃能力。同时研究构造沉降、沉积速率、稀释效应以及沉积相等对有机质丰度的控制作用。结果表明,富含藻类、快速沉降,并且泥岩厚度占地层总厚度比例高的沙河街组三段烃源岩在辽中凹陷南洼和中洼有机质丰度高,北洼有机质丰度为中等,有机质类型整体为Ⅱ型,生烃潜力大。热沉降阶段发育的沙河街组一段和二段烃源岩有机质丰度表现为高—最高,有机质类型为Ⅰ型和Ⅱ型,整体表现为低成熟—成熟。伸展张裂陷阶段快速沉降的东营组三段烃源岩在南洼和中洼有机质丰度高,北洼表现为中等,有机质类型以Ⅱ1型和Ⅱ2型为主,整体表现为未成熟—低成熟。东营组二段下亚段整体"稀释效应"比较明显所以有机质丰度不高,整体表现为未成熟—低成熟。

According to the characteristics of geochemistry, petrology and sedimentology, the paper evaluates the organic matter-rich mud-stones in the Paleogene Shahejie formation, Ed3 and the lower Ed2 from organic matter abundance, type and maturity, and analyzes their hy-drocarbon potential, repectively. Meanwhile, the paper studies the controls of structural subsidence, sedimentary rate, dilutive effect andsedimentary facies on organic matter abundance. The result shows that the organic matter abundance of Es3 source rocks which is featuredwith rich algae, rapid subsidence and high ratio of mudstone thickness to gross thickness is relatively high in the southern and middle Liao-zhong sag, moderate in the northern sag. The organic matters are mostly Type Ⅱ with large hydrocarbon potential. The source rocks of Es1 and Es2developed during thermal subsidence stage have high-highest organic matter abundance with the organic matter of Type Ⅰ and Ⅱ,and being low mature-mature. The source rocks of Ed3 which was rapidly deposited during extensional rifting stge have relatively high or-ganic matter abundance in the southern and middle Liaozhong sag, moderate in the northern sag. The organic matters are dominated byTypeⅡ1and Ⅱ2, being immature-low mature. The dilutive effect of the lower Ed2 is obvious so that the organic matter abundance is nothigh, indicating the source rocks in the lower Ed2 being immature-low mature.