陆相断陷盆地成烃与成藏关系研究

【作者】 刘庆；

【导师】 沈忠民； 张林晔；

【作者基本信息】 成都理工大学 ， 矿产普查与勘探， 2005， 博士

【摘要】 本文借鉴含油气系统理论成因论的思想方法,针对陆相断陷盆地高勘探程度阶段勘探重点向隐蔽油气藏转移的情况,以东营凹陷为例,综合运用地质和地球化学手段,从宏观和微观、有机与无机结合的角度,系统研究了不同烃源岩的发育、成烃过程、油气生成运移的机制,分析了成烃与成藏各地质要素的组合关系和时空演化特点,指出了新的勘探方向,主要成果如下: 根据层序结构特征、古生物组合及微量元素含量等的变化,剖析了Es₄^上—Es₂^下湖盆类型的演变,提出Es₄^上和Es₃^下亚段为均衡补偿湖相盆地沉积,Es₃^中亚段为过补偿湖相盆地沉积,并且以此为基础分析了各层段烃源岩发育的特点及主要控制因素,划分了沉积相,建立了沉积相模式。 系统研究了不同烃源岩的微观特征、有机质与无机矿物的接触关系以及固体有机质的赋存方式,探讨了烃源岩中“富集有机质”和“分散有机质”形成的机制。总结了不同层段烃源岩的地球化学特征和非均质性差异,提出了东营凹陷优质烃源岩的判定标准,总结了其主要判识标志特点,追踪了Es₄^上和Es₃^下亚段优质烃源岩的平面和空间展布。 建立了不同层段烃源岩的自然演化地球化学剖面,系统分析了生烃过程的差异性及其原因,划分了生烃阶段。 系统研究了有机粘土复合体和干酪根的表面化学特征随埋深的变化以及对排烃的指示意义。 根据烃源岩残余油饱和度分析,确定了不同烃源岩的有效排烃门限,提出Es₄^上烃源岩大规模排油深度为2600m,对应着突变压实阶段的后期,Es₃^下亚段大规模排油深度在3200m左右,对应着紧密压实阶段。在突破压力模拟实验和微观结构研究的基础上,剖析了烃源岩物性特征的差异,明确了生烃超压是微裂隙形成的主要机制,提出了优质烃源岩的排烃模式,分析了烃源岩的埋藏史和排烃史。 通过对不同构造带典型油田的解剖,总结了东营凹陷成藏的特点和规律:目前已找到的原油主要来自Es₄^上和Es₃^下优质烃源岩,Es₄^上亚段烃源岩对油藏的贡献大于Es₃^下亚段,前者由洼陷带到盆地边缘相对贡献逐渐加大,而后者则主要在洼陷带成藏:通源断层是油气运移的重要通道:Es₄^上亚段生成的油气存在两期重要的成藏过程,而Es₃^下亚段以晚期成藏为主;区内存在三种基本成烃与成藏组合,已探明油气以源上型为主。在此基础上指出了今后的勘探方向。更多还原

【Abstract】 Dongying Depression is a Mesozoic-Neozoic terrestrial rift basin with abundant petroleum in the east of China. After 40 years of exploration, the basin has reached medium to intensed exploration stages. The main exploration targets gradually change from structural traps to subtle traps such as the stratigraphic traps, lithologic traps. The exploration became more and more difficult. Now how to improve the exploration efficiency is the key issue in nowadays study.Combined with geochemistry and geology means, first we have a systematic study of source rocks formation, oil generation, migration in both macroscopic and microscopic view, then analyze the source and accumulation process of a series of typical oilfield in different tectonic belts, sum up the relationships between hydrocarbon occurrence and petroleum accumulation, and suggest some favorable targets for future exploration. The following are the main points and views:1. Integrative studies of sequence stratigraphy, lithology association, paleontology and trace elements characteristics suggest the lake basin types are changing during Es4u- ES2l. Es4u and ES3l are dominated by balanced-filled type deposition, while ES3m is dominated by over-filled type sediment. The lake basins evolution is manifested by changes in sedimentary characteristics. Es4U and ES3l consist of a series of transgressive-regressive parasequences with well-developed sedimentary rhythmicity. It indicates the climate-driven lake level fluctuations are common. Excellent source rocks finely laminated and lacking bioturbation are well developed in these two units. It suggests the lake water has relatively persistent stratification and the bottom water is anoxic which inhibit the colonizing of benthic organism. Contrast to the underlying two stratigraphy units, ES3m is predominant by massiveness mudstones and silty mudstones with lower organic abundance, no clear rhythmic characteristics and no lamination or indistinct lamination. These features show that the climate-driven water level is not so strong, the lake water has good circulation and lacks persistent stratification, and the bottom water is venticulated.2. In microscopic scale, excellent source rocks (mainly distributed in Es4U and ES3l) are also well laminated and are dominated by enriched organic matter, which often forms continual organic matter network. Detailed investigations uncover four types of laminae (including carbonate laminae, clay mineral laminae, organic laminaeand pyrite laminae). In contrast, poor to mediate source rocks (mainly distributed in Es3m) are poorly laminated and dominated by disseminated organic matter.3. Source rocks of different units are investigated for their geochemistry difference in organic richness, organic matter type, and biomarker characteristics. Then the criterion for the excellent source rocks is suggested with a total organic carbon of 3.0%. According to the relatively high resistance log characteristics, excellent source rocks from Es4U and ES31 are traced and mapped.4. Based on the organic geochemistry analysis of core samples, three source rocks evolutionary profiles (Es4U, ES31 and Es3m) are set up. It shows source rocks of Es4U deposited in saline to brackish environment generate hydrocarbons in relatively shallow depths than fresh to brackish source rocks of ES31. The differences also manifest by the chemical dynamic parameters and the chemical structure features of the organic matter.5. Surface geochemistry characteristics of organic-mineral complexities and kerogen from different source rocks, including the specific area surfaces, pore structure, surface energy, etc. are investigated for their evolution path with burial.6. According to the natural geochemistry section and natural remnant oil saturation analysis, the effective hydrocarbon expulsion thresholds of different source rocks are determined. The critical depth for Es4U to expel hydrocarbons in large amount is about 2600m, which are corresponding to late abrupt compaction stage, but for ES31 it is at least 3000m, which are corresponding to tight compaction stage. Combined with burial history, surface geochemistry of kerogen and organic-minerals complexities, micro-fabric features and breakthrough pressure experiments, we put forward a lateral migration model for excellent source rocks.7. Synthetically reservoir geology analysis (oil, water and pressure) and oil source correlation indicate that the oils are sourced mainly from the Es4U and ES31 excellent source rocks in Dongying Depression.8. Seven typical oilfields, including Sheng-tuo oilfield, Dong-xin oilfield, Niu-zhuang oilfield, Liang-jia-lou oilfield, Wang-jia-gang oilfield and Ba-mian-he oilfield, which are located in different tectonic belts are investigated for the source-reservoir relationship and accumulation process. The following are the elementary rules: (1) Most of the oils sourced from ES31 are discovered in the sag zone, and the contribution of ES31 decreases from the sag center to the sag margin. In contrast, the contribution of Es4U increases from the sag zone to the slope zone and更多还原