北塘凹陷古近系烃源岩特征及热演化史模拟

Thermal Evolution Modeling and Characteristic of Source Rock of Paleogene in Beitang Sag

根据大量的烃源岩地球化学数据,分析了北塘凹陷古近系烃源岩的地球化学特征,从有机碳含量（TOC）、氯仿沥青＂A＂、总烃含量、S1＋S2、有机质类型和成熟度（Ro）等方面对古近系烃源岩进行了系统分析,结果表明北塘凹陷东三段、沙一段和沙三段是本区的烃源岩层段,其中沙三段烃源岩生烃指标最好,是本区的主力烃源岩层段.烃源岩的模拟结果表明：（1）北塘凹陷的烃源岩门限深度为2 390 m,门限温度为94.2℃,进入生烃门限的时间约为2528 Ma;（2）北塘凹陷沙三段的现今地层温度为140160℃,Ro达0.9%1.4%,正处于生油高峰期;沙一、二段的现今地层温度为100140℃,Ro达到了0.75%1.0%左右,已进入中等成熟阶段;东营组的现今地层温度为80100℃,Ro为0.45%0.75%,处于低-中等成熟阶段.

Based on large quantity of organic geochemistry data,the geochemistry characteristics are systematically analyzed on organic carbonate content（TOC）,chloroform bitumen ＂A＂,overall hydrocarbon content,S1＋S2,organic matter types and maturity（Ro%） and so on.It shows that the Dong 3 Member,Sha 1 Member and Sha 3 Member are the main oil source beds of Beitang sag,especially,Sha 3 Member is the best in source rock quality.The model results indicate that（1） The depth of oil generative threshold is about 2 390 m,and the temperature is about 94.2 ℃,and the time entering on the oil generative threshold is from 25 Ma to 28 Ma in Beitang sag;（2） The present-day temperature of Sha 3 Layer is 140-160 ℃,the present-day Ro ranges between 0.9%-1.4%,It is in its peak of oil generation.The temperature of Sha 1＋2 Layer is 100-140 ℃,the Ro ranged between 0.75%-1.0%,which suggests that it is in the middle-maturity at present.The present-day temperature of Dongying Layer is 80-100 ℃,the present-day Ro ranges between 0.45%-0.75%,which indicates that the present-day source rocks are in low maturation.