东营凹陷博兴洼陷石油生成、运移和聚集史数值模拟

渤海湾盆地东营凹陷博兴洼陷烃源岩为沙河街组三段中、下亚段和沙河街组四段上亚段暗色泥岩,原油探明地质储量主要集中在沙三段和沙四段砂岩储层中。在恢复东营凹陷博兴洼陷热史的基础上,对烃源岩段成熟史、生排烃史和油气聚集史特征进行了模拟。结果表明:①至少存在两期原油的生、排烃过程,第一期为30~25Ma,第二期为16~0Ma,特别是距今5Ma(馆陶组沉积末期)以来,石油大量生成并排出形成现今的油气分布格局,而现今主力烃源岩段仍处于大量生油阶段;②沙四段原油的生成量和聚集量都明显大于沙三段,说明主力烃源岩段的生、排烃特征对原油纵向分布具有一定控制作用;③在沙三中、下亚段和沙四上亚段共划出7个距离源区较近的有利油气聚集区,而缓坡带虽处于油气低势区,有利于油气的聚集,但烃源岩成熟度低,并且来自于洼陷区的原油受博兴断裂带阻隔,导致博兴缓坡带油气聚集量小。

Numerical simulation of hydrocarbon generation, migration and accumulation in the Boxing sag, Dongying Depression, Jiyang Subbasin

The dark shale rich in organic matter in the middle and lower parts of Member 3(Es³)and the upper part of Member 4(Es⁴)of the Shahejie Formation are the source rocks in the Boxing sag of the Dongying depression.The measured geologic reserves are mainly discovered in the sandstones of the Es³ and Es⁴.Based on a reconstruction of thermal history of the sag,the researchers simulated the source rock thermal maturation history and hydrocarbon generation,migration and accumulation histories.The findings are listed as the following:①There are at least two periods of hydrocarbon generation and expulsion with the first period lasting from 30Ma to 25Ma and the second ranging from 16Ma to 0Ma.of the second period,the most important time is from 5Ma(the end of deposition of the Guantao Formation)to the present,during which large amount of oil were generated and distributed the way we see today,and the major source rocks are supposed to be still generating oil at pre-sent;②The amount of oil generated and accumulated in the Es⁴ member is significantly bigger than those in the Es³ member,indicating the hydrocarbon generation and expulsion process of the main source rocks controlled the vertical crude oil distribution to a certain extent.③Seven favorable oil plays are identified near the main source rocks according to the simulation.Although the gentle slope in the Boxing sag is located in the lower oil-potential area and is favorable for oil migration and accumulation,the maturity of source rocks at the slope area is low and the oil migration from the lower area is blocked by the Boxing fault zone,resulting in the relatively small amount of oil accumulated in the slope.