Coupling mechanism of mineralization and hydrocarbon-forming in hydrothermal convection system: An example from Longtoushan Sn-polymetal deposit, Dachang

Longtoushan Sn-polymetal deposit is a large-scale deposit of high-tenor. The ore-bodies occur in reef limestone of middle Devonian. There is much anthraxolite in reef limestone and ore-bodies. The anthraxolite is the postmature result of oil-gas’ thermal metamorphism. The close relationship of anthraxolite and Sn-polymetal deposit reveals the space-time relation between oil-gas evolution and Sn-polymetal mineralization. Sulfur isotope of Longtoushan deposit is close to oil’s sulfur in Devonian, which indicates obvious relationship between the sulfur’s source of deposit and oil-gas’ activity. The forming of Longtoushan deposit relates to exhalative-sedimentary mineralization in Devonian. Because of the favorable hydrocarbon-forming condition of Longtoushan reef and surrounding basin facies’ black shale and peat, coupling of ore-formation and hydrocarbon-forming occurs in seabed’s hydrothermal convection. The distributing of ore-forming elements indicates the presence of hydrothermal convection system. The thermal fluid containing organic matters conduces to Sn-polymetal elements’ activation and transfer, and provides catalyzing condition to the transforming from SO ₄ ²⁻ to S²⁻. The erosion action of brine containing organic acid to reef limestone induces the growing of crannies and karst’s caverns, which provides advantageous space to Sn-polymetal mineralization. The heat source of mineralization provides thermocatalysis condition to hydrocarbon-forming. When the circulatory fluid containing oil-gas enters the high-temperature region(>150°C), the oil-gas is decomposed and anthraxolite comes into being. Foundation item: Project(20030533012) supported by Specialized Research Fund for the Doctoral Program of Higher Education     

青藏高原羌塘盆地有机相展布与成烃模式

青藏高原羌塘盆地中生界海相J_3s,J_3x,J₃b和J_3x4套主要烃源层的成烃生物主要为宏观藻类。J_3s和J₃b烃源层主要发育Ⅱ₁和Ⅱ₂有机相,J_3x烃源层主要发育Ⅱ₁,Ⅱ₂和木本有机相,均从盆地或坳陷中部向盆地东北部逐渐变差;T_3x烃源层各类有机相均有发育,从盆地或坳陷南、北部的Ⅰ或Ⅱ₁有机相向中央隆起区逐渐过渡为木本有机相。羌塘盆地中部多正处于成熟中晚期,侏罗系Ⅱ₁有机相是最有利的生油相带区;北羌塘坳陷中西部多处于高成熟阶段,侏罗系Ⅱ₁有机相是有利的凝析油或轻质油气相带区;羌塘盆地T_3xⅡ₁有机相已经处于过成熟,是有利的生气相带区。      

现河庄地区泥岩裂缝主控因素分析与油气成藏

将济阳坳陷东营凹陷现河庄油田泥质岩储层的裂缝类型分为6类,研究了泥岩裂缝识别特征,分析了泥岩裂缝的主控因素是构造应力和异常压力,并且还受到沉积相带、储层岩性、岩层厚度等因素影响。现河庄油田泥岩裂缝形成于馆陶组沉积早期,正好与烃源岩大规模生、排烃期相匹配,形成了泥岩裂缝油气藏。     

柴达木盆地北缘中、下侏罗统烃源岩生烃潜力

通过对柴达木盆地北缘中、下侏罗统烃源岩地球化学特征的详细对比分析表明,中侏罗统的沉积范围大于下侏罗统,且水体更深,构成了更大范围的连通湖盆。中侏罗统烃源岩生烃母质中的藻类体丰度较下侏罗统烃源岩的高,而角质体含量相对较低。据此,中侏罗统烃源岩的有机质类型好于下侏罗统烃源岩。但根据现今残余烃源岩的分布和有机质丰度特征,下侏罗统烃源岩的生烃基础却好于中侏罗统,前者在生烃凹陷区目前已进入高过成熟演化阶段（R _o >2.0%）,而后者在不同构造单元以差异热演化为特征。综合对比分析认为,两套烃源岩均具有良好的生烃潜力,在今后的油气勘探和地质研究中,应将两套烃源岩置于同等重要位置。     

Coupling mechanism of mineralization and hydrocarbon-forming in hydrothermal convection system: An example from Longtoushan Sn-polymetal deposit, Dachang

Longtoushan Sn-polymetal deposit is a large-scale deposit of high-tenor. The ore-bodies occur in reef limestone of middle Devonian. There is much anthraxolite in reef limestone and ore-bodies. The anthraxolite is the postmature result of oil-gas' thermal metamorphism. The close relationship of anthraxolite and Sn-polymetal deposit reveals the space-time relation between oil-gas evolution and Sn-polymetal mineralization. Sulfur isotope of Longtoushan deposit is close to oil's sulfur in Devonian, which indicates obvious relationship between the sulfur's source of deposit and oil-gas' activity. The forming of Longtoushan deposit relates to exhalative-sedimentary mineralization in Devonian. Because of the favorable hydrocarbon-forming condition of Longtoushan reef and surrounding basin facies' black shale and peat, coupling of ore-formation and hydrocarbon-forming occurs in seabed's hydrothermal convection. The distributing of ore-forming elements indicates the presence of hydrothermal convection system. The thermal fluid containing organic matters conduces to Sn-polymetal elements' activation and transfer, and provides catalyzing condition to the transforming from SO42- to S2-. The erosion action of brine containing organic acid to reef limestone induces the growing of crannies and karst's caverns, which provides advantageous space to Sn-polymetal mineralization. The heat source of mineralization provides thermocatalysis condition to hydrocarbon-forming. When the circulatory fluid containing oil-gas enters the high-temperature region(＞150 ℃ ), the oil-gas is decomposed and anthraxolite comes into being.     

异常高压对烃源岩成烃机理和油气运聚成藏的影响

流体异常高压控制着烃源岩的成烃机理和油气运聚成藏。超压促进沙四上亚段富硫烃源岩的生烃,而对贫硫的沙三中下亚段烃源岩生烃起抑制作用。因而沙四上亚段烃源岩早生、早排、成熟度较低,生成的油气充注凹陷外围及上部圈闭;沙三中下亚段烃源岩晚生、晚排、成熟度较高,生成的油气充注凹陷内部及下部圈闭。流体异常高压还能形成油气运聚的通道。所以,隐蔽输导体系的预测是今后岩性油气藏勘探的关键。      

东濮凹陷优质烃源岩生烃演化机理

复杂构造条件下蒸发成因咸化湖盆优质烃源岩的生烃演化机理,是目前有机地球化学研究最为关注的问题之一。为探索这一问题,文中以东濮凹陷为例,在分析烃源岩地球化学特征的基础上,开展了不同流体介质条件下优质烃源岩成烃生物组成和有限空间生烃热模拟等研究。结果表明:生烃过程受地层水矿化度和有机质生物来源的双重控制,咸水环境优质烃源岩最为发育,有机质来源于颗石藻、蓝藻和沟鞭藻等多种藻类的贡献,显微结构呈纹层状互层,生烃时间早,生烃周期长,液态烃产率高,具有5个生烃阶段;淡水环境优质烃源岩极少,有机质来源于绿藻和高等植物的贡献,生烃时间晚,液态烃产率低,气态烃产率高,仅具有3个生烃阶段;半咸水环境优质烃源岩的有机质主要来源于沟鞭藻,优质烃源岩发育概率、生烃时间、液态烃产率介于咸水环境和淡水环境烃源岩之间,具有3个生烃阶段。     

海相改造残留盆地的地质特征和勘探前景

中国前新生界海相地层很发育,其油气资源潜量丰富,但目前探明程度和勘探成功率很低。其根本原因在于它们普遍经历过多期改造,具有改造残留盆地的性质。主要的改造方式有抬升剥蚀、构造变形和深埋等,具体受盆地在各期构造运动中所处的大地构造背景控制,如被前陆盆地或裂谷盆地所叠加,整体抬升转化成为高原或高地,以及由于冲断褶皱而转化为断褶带甚至于造山带等。海相改造残留盆地具有复杂的成藏动力学过程和油气系统。其最重要的油气成藏特点有 :(1)多期成藏,形成复杂油气系统,油气藏高度分散;(2)晚期(喜马拉雅期)成藏,明显受喜马拉雅运动控制。因此在油气勘探中要以正确认识和描述地质特征的非均一性为关键,以油气的生、运、散、聚成藏动力学过程为主线,从各种地质要素的相互作用的发展演化历史的角度开展研究。海相改造残留盆地勘探前景广阔,必将成为我国 2 1世纪油气勘探的主战场。