辽东湾断陷与下辽河坳陷油气成藏条件及油气分布特征的差异性分析

通过综合对比分析,发现辽东湾断陷和下辽河坳陷油气成藏条件和油气分布规律存在差异:①两个地区都发育沙三段主力烃源岩,但下辽河西部凹陷和大民屯凹陷还发育沙四段主力烃源岩;②辽东湾断陷储集层成因类型较单一,下辽河坳陷多样化;③与下辽河坳陷相比,辽东湾砂体不发育,断层少,输导条件欠佳;④辽东湾已发现的圈闭类型较单一,以构造圈闭为主,单纯的岩性圈闭发现较少,而下辽河坳陷内发育各种类型的构造、地层和岩性圈闭;⑤辽东湾断陷和下辽河坳陷都具备良好的区域盖层条件和保存条件;⑥辽东湾断陷原油探明储量主要分布在东营组,而下辽河坳陷原油探明储量主要分布在沙河街组;⑦辽东湾断陷现今找到的大中型油气田多位于辽西低凸起主断棱带上,而下辽河坳陷在斜坡带、陡坡带及深陷区均有大型油气田发现,具有“整凹含油”的特点.以上对比分析对于进一步预测辽东湾地区油气勘探开发潜力具有重要意义.

Contrast of hydrocarbon accumulation conditions and hydrocarbon distributions between Liaodong Bay Fault Depression and Xialiaohe Depression

Either Liaodong Bay Fault Depression or Xialiaohe Depression both is a part of Bohai Bay Basin,and they have similar tectonic evolution history and sedimentary history.However,there is great difference between their proven reserves.It is found that there are differences between hydrocarbon accumulation conditions and hydrocarbon distributions of two depressions based on the detailed comparison and analysis of their source rocks,reservoirs,seals,passage systems,traps,conserved conditions and distributions of the pools.The following seven main conclusions can be drawn:(1)The main hydrocarbon source rocks in these two depressions are in Sha-3 Formation,but there is also main hydrocarbon source rock.in Sha-4 Formation of Xialiaohe Depression.(2)Liaodong Bay Depression has individual genetic type of reservoir,but Xialiaohe Depression has various genetic types of reservoir.(3)Compared with Xialiaohe Depression,sandbody develops worse,there are fewer faults and worse passage system in Liaodong Bay Depression.(4)There are mainly structural pools in Liaodong Bay Depression,while there are structural pools,stratigraphic pools and lithological pools in Xialiaohe Depression.(5)There are good regional seal and conservation conditions in these two depressions.(6)The proven reserves of Liaodong Bay Depression mainly distributes in Dongying Formation,while that of Xialiaohe Depression mainly distributes in Shahejie Formation.(7)The most of large-medium oil/gas fields in Liaodong Bay Depression mainly lie in Liaoxi uplift,and larger pools are not discovered in slope belt and deeper sag;while in Xialiaohe Depression,the hydrocarbon accumulation belts lie in slope,steep slope,uplift and central structural belt,which indicates that hydrocarbon distributes in whole depression.