从有机质生烃角度分析北大港构造带东翼深层天然气勘探潜力

Analysis of deep gas exploration potential in the east part of Beidagang formation on the basis of the hydrocarbon-generating theory

北大港构造带东翼紧邻歧口凹陷,是歧口凹陷油气运移的有利指向区.岐口凹陷有机质类型主要为腐泥型,埋深大,演化程度高,凹陷中心沙三段烃源岩成熟度达到2.5%,已到高—过成熟阶段,应有大量的高熟天然气和原油裂解气生成.北大港构造带东翼目前发现的油气都是成熟阶段的产物,后期高—过成熟阶段的产物没有运移到中浅层.分析烃源岩特征、油气成熟度、天然气类型及构造特征.结果表明:烃源岩成熟阶段生成的原油在构造深层聚集,后因断裂沟通,一部分运移到浅层成藏,另一部分继续在深部储集物性较好的构造和砂体中富集,随演化程度不断加深,原油裂解成气.

The east of Beidagang structure belt is the most favorable exploration area of oil and gas from the Qikou sag.In Qikou sag,the main type of the kerogen is from Ⅰ to Ⅱ1.The Ro of the Es3 in the sag has reached 2.5%,which reached to high or past matured stage of kerogen and should have much past-matured gas produced.By analyzing the features of source rock,oil,gas and structure,it is pointed out that the oil and gas found in the reservoirs near to the sag is matured products,no high or past matured oil-gas has been found so far,the reason is that the blocking of the fault and the high pressured seal limited the migration of the high-past matured oil and gas from the deep to the shallow.The good sand and strap have been found in the deep of the sag,so the oil produced during oil generation peak can be accumulated in them,and cracked to gas in the high-past matured stage.