南华北盆地黄口凹陷构造形成演化及油气勘探前景

The structure evolution and hydrocarbon potential in Huangkou sag, southern Nort h China basin.

黄口凹陷是南华北盆地的油气远景区之一。平衡剖面研究成果表明其具有复合叠加盆地结构 ,太古界—早元古界结晶基底和古生界克拉通盆地沉积构成盆地的双层基底 ,中、新生界是盆地的主要沉积盖层。凹陷的形成与演化大致经历了 6个时期 :挤压拗陷期(J—K11)、剪切拉张初始裂陷期 (K21)、抬升剥蚀期 (K2 —E1)、剪切拉张裂陷扩张期 (E2 —E13)、裂陷消亡期 (E23)和区域坳陷期 (Q +N)。在构造研究的基础上 ,运用BASIMIS盆地模拟研究成果 ,综合分析凹陷的含油气系统 ,认为成熟烃源岩主要是石炭 二叠系煤系泥岩和上侏罗统—下白垩统湖相泥岩 ,下古生界 (寒武系—中奥陶统 )海相碳酸盐岩也是潜在的烃源岩 ;青山组和下第三系砂岩是主要储集层 ;盖层条件较好。油气生运聚期与圈闭形成期匹配良好 ,有利于原生油气藏的形成。由于该区经历了加里东期、海西期、印支期、燕山期和喜山期等多期构造运动 ,油气藏的后期保存条件是决定油气能否富集的至关重要因素。

Huangkou sag is one of the region with hydrocarbon potential in southern North China basin. The study of b alanced cross section indicates that its structure has the characteristics of a composite superposition basin. Its double basements are Archaeozoic and Lower Pr oterozoic crystalline basement and Paleozoic cratonic basin sedimentary rocks. T he infill of the sag mainly i ncludes Mesozoic and Cenozoic systems. The process of the sag formation and evol ution can be divided into six stages approximately: compressive depression ( J K 1 1), shear extensional initial rifting (K 2 1), uplift denudation (K 2 E 1), shear extensional rift expansion (E 2 E 1 3), rift ending (E 2 3 ) and regional depression (Q+N). Based on the structure study, the petroleum sys tem in the sag has been analyzed synthetically with the BASIMIS. The major matur e source rocks are Car boniferous Permian coal measure mudstone and Upper Jurassic Lower Cretaceous lacustrine facies mudstone. Lower Paleozoic marine carbonate is also the potenti al source rocks. Qingshan Formation and Lower Eogene sandstones are the main res e rvoir rocks. The sag also has good cap rocks. The time of the hydrocarbon genera tion migration accumulation matched perfectly with the formation periods of th e traps, which contributed to the formation of the primary hydrocarbon reservoir . Since the sag had experienced Caledonian, Hercynian, Indosinian, Yanshan and H imalayan movements, the later preservation conditions of the reservoirs are the critical factor to determine the hydrocarbon enrichment. It is forecasted that t he central west part of the sag is a favorable area for oil and gas exploration .