北部湾盆地地温异常影响因素探讨

北部湾盆地地温场的不均一性除与基岩埋深有一定关系外,在很大程度上与活动热流体有关。含油气钻孔或含油气构造带大多分布在地温梯度和热流值较高的部位。压实作用及烃的生成所产生的压力促使热流体沿同生断裂以“幕式喷发”的方式发生运移,而流体所携带的巨大热量却不受盖层和构造圈闭等因素的影响向上传递,从而导致在地表(海底)形成高热流异常。     

塔里木盆地克拉2气田储层流体包裹体与油气成藏研究

储层流体包裹体研究是认识油气运移、油气成藏的有效方法之一.通过对塔里木盆地克拉2气田克拉201井储层流体包裹体的系统取样研究,得到储层流体包裹体的四组均一温度:75～105℃,120～135℃,155～175℃,200～250℃.其中前三组与油气成藏有关,第四组及更高的温度可能与地下的热液活动有关.结合沉积埋藏史和热史的恢复,认为克拉2气田的成藏时间为11～2.5 Ma之间,即康村组至库车组沉积初期开始,到库车组遭受抬升剥蚀时停止.推测来自地下的高温热液可能对气藏起过重要的改造作用.     

南海南部陆缘地质流体类型及其油气成藏意义

南海南部陆缘蕴藏着非常丰富的油气资源。为了解南海南部陆缘流体活动系统以及与油气藏之间的关系,以高精度2D地震资料为基础,对南海南部陆缘流体活动系统的类型、地震反射特征、以及对油气成藏的意义开展了研究。在南海南部陆缘发现了多种流体活动系统,包括:泥底辟/泥火山、气烟囱、管状通道、与构造断层相关的流体活动系统。这些流体活动系统具有不同的地震反射特征,常常出现含气强振幅异常带、弱振幅杂乱反射带以及"下拉"或者"上拱"地震反射形态等流体活动系统的标志特征。流体活动系统受到构造运动和沉积因素的影响,并且与深部高温高压塑性流体密切相关,流体活动系统优先发育在地层薄弱部位。流体活动系统及所伴生的断裂和裂隙常常作为油气富集区的运输通道;并且流体活动系统所运移的强溶蚀性流体和深部热液流体有利于油气储层的形成,特别是对于碳酸盐岩储层的改造尤为明显。因此,流体活动系统不仅能作为油气运移通道,也可以改善储层,对油气成藏具有重要意义。     

Impact of single inclined faults on the fluid flow and heat transport: results from 3-D finite element simulations

The impact of inclined faults on the hydrothermal field is assessed by adding simplified structural settings to synthetic models. This study is innovative in carrying out numerical simulations because it integrates the real 3-D nature of flow influenced by a fault in a porous medium, thereby providing a useful tool for complex geothermal modelling. The 3-D simulations for the coupled fluid flow and heat transport processes are based on the finite element method. In the model, one geological layer is dissected by a dipping fault. Sensitivity analyses are conducted to quantify the effects of the fault’s transmissivity on the fluid flow and thermal field. Different fault models are compared with a model where no fault is present to evaluate the effect of varying fault transmissivity. The results show that faults have a significant impact on the hydrothermal field. Varying either the fault zone width or the fault permeability will result in relevant differences in the pressure, velocity and temperature field. A linear relationship between fault zone width and fluid velocity is found, indicating that velocities increase with decreasing widths. The faults act as preferential pathways for advective heat transport in case of highly transmissive faults, whereas almost no fluid may be transported through poorly transmissive faults.     

塔中地区深部流体活动及其对油气成藏的热作用

利用塔中地区钻井岩心、分析化验、地震等资料,系统地分析了深部流体活动机制及其对油气成藏的热作用。通过奥陶系岩石热液矿化蚀变、古地温异常及CO₂无机成因气与储层包裹体测温等研究后认为：深部流体通过地震、火山或其它各种通道,如断裂、不整合面等向浅部运移;深部流体提高生烃量及生烃速率,而且降低烃源岩中残余有机质含量,影响有效烃源岩评价;深部流体对油气储层的影响,既有热液方解石充填的破坏性,又有热液溶蚀、热液次生矿物带的建设性;深部流体在向上运移的过程中形成异常高压, 为油气二次运移提供动力。深部流体对天然气形成的热作用、储层改造与成藏动力学方面,不仅在能量上,而且在物质上都对油气藏的形成和演化起到重要影响,并使塔中地区奥陶系油气成因更加复杂化。     

“岩浆热场”说及其成矿意义(上)

文中首先介绍了岩浆热场的沿革,指出"岩浆热场"并不是一个新概念,很早已出现在文献中了。常识告诉我们,炽热的岩浆侵位必定在周围形成一个热场,这就是岩浆热场。国外在19世纪晚期即对岩浆热场有比较深入的研究。罗文积和陈家清早在20世纪90年代(1997)就明确表述了对"岩浆热场"的认识,并给予精彩的阐述,他们是"岩浆热场"学说的先行者。文中简要介绍了地热场的概念,讨论了岩石的热力学性质、热传导形式、影响热流和地温分布的各种可能的因素。而"岩浆热场"指的是:在一个很短的时间内,在一个局部的地区出现的岩浆活动,使该区域地热梯度相对周边地区明显的上升,使之形成一个局部区域的热场。热场的规模很小,通常只离岩体几米或几公里。热异常和等温线是垂直分布的,叠加在地热场之上。并介绍了岩浆热场的基本特征。岩浆热场与地热场的热的来源不同,热的分布不同,地温梯度不同,热场规模不同,持续的时间不同,热与流体的关系不同以及研究方法不同等。岩浆热场说是建立在岩浆物理性质和岩浆动力学基础上的,它依赖于对岩浆的形成、侵位、冷却、固结及其对围岩的影响等知识的了解。牵涉到岩浆的温度、压力、黏度、密度、流变等基本问题。文中着重讨论了岩浆对围岩的热效应和岩浆热场中的流体等问题。岩浆热场最重要的意义是,它是流体赖以上升的通道。文中还概略讨论了流体和成矿流体来自哪里?流体是怎样上升的?热场中流体是怎样对流循环的?热液双向汇聚成矿理论等。     

岩浆热场与热液多金属成矿作用

岩浆热场指的是很短时间内一个局部地区出现的岩浆活动使该区域地热梯度明显上升,形成局部区域的瞬间热场。热场的规模通常很小,离岩体约几米至几千米。范围、规模和形状与侵入体的温度、成分、形态、大小、侵入深度以及流体、构造、围岩性质等有关。岩浆热场最重要的意义在于它是流体赖以上升的场所。岩浆热场不同于地热场的一个重要区别是,岩浆热场往往伴有流体的活动,是流体循环、上升、汲取地壳中有用金属元素的场所。文中讨论了岩浆热场与热液多金属成矿之间的关系,讨论了岩浆热场在岩浆热液矿床、热泉型矿床、热水沉积矿床以及变质热液矿床成矿过程中的作用。岩浆热场对于热液多金属成矿作用的影响是非常明显的,它从一个新的角度解释了成矿为什么是多金属、多成因、多来源等问题。文中强调指出,岩浆热场说解释了为什么大规模岩浆活动与大规模成矿作用密切相关,指出大规模岩浆活动产生的热效应不是1+1=2,而是1+12的效果。即它可以在一个局部范围内把岩浆热场从一个开放体系变为封闭体系,在这个封闭体系内,固岩可以达到更高的温度,热可以持续更长的时间,促进热场范围内流体的对流循环,使流体可以从围岩中汲取尽可能多的有用金属元素,起到单个岩浆无法比拟的效果。许多大型一超大型的多金属矿床即可能与这种作用有关。从热场说角度来看,大规模岩浆活动的成矿潜力几乎是无可限量的。文中还讨论了岩浆热场说的原理及应用中存在的问题,指出岩浆热场说与成矿的关系非常值得关注,它也许可以改变目前对成矿作用的某些固有认识,开拓出一个新领域。     

Seismic characteristics and mechanism of fluid flow structures in the central depression of Qiongdongnan basin,northern margin of South China Sea

ABSTRACT

Understanding fluid flow structures in a rifted basin may enhance our knowledge of their origination and evolution. Through geochemical analysis and seismic interpretation, different fluid flow features are identified in the central depression of Qiongdongnan basin, northern South China Sea. These structures include mud diapir, gas chimney, hydrothermal pipes, faults, blowout pipes, and associated extrusions. Mud diapirs are primarily located on the slope belts, whereas gas chimneys are on the basement highs in the southwest of the study area. Their distribution appears closely controlled by tectonic stress field and overpressure, the later is caused by hydrocarbon generation and compaction disequilibrium. High sediment overloading, weak post-rift tectonic activity, and high average geothermal gradient may contribute to the compaction disequilibrium. The occurrence of gas chimneys on the basement high suggests that lateral transportation and relief of overpressure is a significant factor. Distribution of broad hydrothermal pipes is related with the thinning continental crust and pre-existing boundary faults in the central depression. They are probably attributed to intruded sills dissolution and were caused by hydrothermal fluids vertically. Geochemical data from gas reservoirs analysis indicates that mud diapirs and gas chimneys are critical pathways for thermogenic gases, whereas hydrothermal pipes and part of the faults may act as pathways of both thermogenic and inorganic gases. The blowout pipes mainly occur in the northwestern central depression near the continental slope, where fluid flows ascend gradually from a series of Pliocene-current prograding wedge-formed units with a hydraulic fracture in shallow. Hundreds of seafloor pockmarks and mounds associated with blowout pipes located above the NE-SW elongated Pliocene-Quaternary slope-break belts. These extrusive structures indicate that fluids ascend through blowout pipes and were expelled at the present seabed. Our results indicate that fluid flow structures are probably responsible for fluid activities and must be taken into account when assessing the hydrocarbon potential, geologic hazard, and benthic ecosystem.     

Composition and origin of hydrothermal petroleum and associated lipids in the sulfide deposits of the Rainbow field (Mid-Atlantic Ridge at 36°N)

The lipid components in hydrothermal sulfide deposits from the Rainbow vent field (Mid-Atlantic Ridge at 36°N) were studied by gas chromatography/mass spectrometry. The Rainbow vent field is one of two known active hydrothermal systems related to abyssal circulation, where high-temperature fluids are formed during serpentinization of ultrabasic crustal rocks. The major amount of the extractable organic matter from the sulfides consists of normal and branched alkanes, UCM, PAHs, terpenoids, and fatty acids. The branched alkanes are comprised of unique gem-diethylalkane series, possibly from sulfide oxidizing bacteria, and biphytanes from archaea. The characteristic lipid and biomarker compounds found in the hydrothermal samples support a predominantly biological origin of the bitumens from the thermal transformation of the biomass of microorganisms (bacteria and archea) and minor macrofauna of this vent field. A search for molecular evidence for abiogenic thermocatalytic synthesis of organic compounds was negative. However, methane in the hydrothermal fluids and possibly a minor amount of the alkanes in the sulfides may be of an abiogenic origin in the Rainbow vent field.     

热液汉体泵吸上浸管流动力学模拟及其预测意义

地球流体相在各种地质过程中的行为和作用,是地球物质科学的核心课题。通过对山西义兴寨脉状金矿热液流体上侵动力学的模拟计算证明,构造泵吸驱动的矿液流动具有有压管流的性质,并探索引入柏努利方程对其流动状态进行描述。论证了地质流体因其性质和所处地质环境的不同,可划分为多孔介质中的渗流和较宽阔裂隙中的管流（流动）两种。赋 于地壳中深部或由岩浆冷却分异形成的成矿流体,在张前性断裂活动中,主要由构造泵吸机制驱使     

DF1-1底辟区构造应力场及渗流场演化的数值模拟研究

DF1-1底辟区是莺歌海盆地内超压流体最活跃的地带之一.超压流体的活动直接受控于构造应力及其形成的不同类型的断裂和裂隙构成的输导系统.从底辟区大规模流体垂向活动以及幕式活动的特征来看, 流体流动的动力主要是由于垂向压差的存在以及渗流场变化引起的局部应力场(包括热应力场) 的作用所致.在详细研究底辟区的构造及流体活动关系的基础上, 对底辟区构造应力场及渗流场的演化进行了模拟.结果显示: 构造运动引起的应力场决定了DF1-1底辟区油气沿主要断裂系走向迁移的总趋势, 在底辟区流体从底辟的两侧向其中心运移, 由底辟体中向上运移为主; 高压流体产生的热应力控制局部应力场状况及油气运移方向, 驱动流体向底辟体顶部运移, 当热应力值过大时有可能改变应力场状况以及油气运移总趋势.      

地壳中流体的大规模流动系统及其成矿意义

地壳中的水量相当于海洋体积的水量,已确定的水溶液活动深度可达２０ｋｍ,根据驱动力的不同,地壳中主要存在三大流动系统,即重力,浮力和应力驱动系统。本文评述了当前国际上有关大规模流体运移研究扩要进展和发展趋势,介绍了有关流动系统的模式和运动机制,并简要论述了其成矿意义。文章指出,目前区域古流体场地球化学背景问题已成为区域规律和热液成矿理论中一个不容回避的关键课题,地壳中大规模流动系统将成为今后地质流体研究的重要方向之一。     

热液流体泵吸上侵管流动力学模拟及其预测意义

地球流体相在各种地质过程中的行为和作用 ,是地球物质科学的核心课题。通过对山西义兴寨脉状金矿热液流体上侵动力学的模拟计算证明 ,构造泵吸驱动的矿液流动具有有压管流的性质 ,并探索引入柏努利方程对其流动状态进行描述。论证了地质流体因其性质和所处地质环境的不同 ,可划分为多孔介质中的渗流和较宽阔裂隙中的管流 (流动 )两种。赋存于地壳中深部或由岩浆冷却分异形成的成矿流体 ,在张剪性断裂活动中 ,主要由构造泵吸机制驱使其上侵成矿。热液在相对封闭 (未喷出地表 )的较宽阔的断裂系统中受应力驱动上侵流动 ,其性质接近于流体力学中的有压管流 ,可以用柏努利方程进行描述。推导出了描述热液管流上侵动力学特征的柏努利方程关系式 ,表明热液的流速与所处构造压力差、流体的性质 (温度和密度等 ) ,以及流动通道的结构特征有关。对义兴寨脉状金矿进行的计算结果证明 ,热液上侵流速场的空间变化与金矿化分布格局相吻合 ,流体的高流速地段指示含矿石英脉密集区 ,因此具有成矿预测意义。针对热液管流上侵过程建立的动力学总方程中 ,每一个变量都有明确的地质意义 ,并可以在矿区实际测量 ;绘制的几组理论关系曲线有助于具体分析各种地质和地球化学条件对成矿的控制作用。     

Two dimensional fluid flow models at two gas hydrate sites offshore southwestern Taiwan

Fluid migration patterns are important for understanding gas hydrate and hydrocarbon systems. However, conducting experiments on or below the seafloor is difficult because crustal fluid flow rates are usually very slow, so long term observations are needed. Temperature can be used as a good tracer for studying fluid flows. Temperatures derived from bottom-simulating reflectors (BSRs) might help to understand fluid migration patterns in shallow marine sediments. In this study, we studied 2D fluid flow patterns in two potential gas hydrate provinces offshore southwestern Taiwan: the Yung-An Ridge in the active margin and Formosa Ridge in the passive margin. We used 2D bathymetry, average seafloor temperatures and regional geothermal gradients measured by thermal probes, as constraints to construct 2D theoretical conductive temperature fields using finite element methods. We then compared the BSR-based temperature with the theoretical conductive temperature field. The results show a temperature discrepancy attributed to advective heat transfer due to fluid migration. For the Yung-An Ridge, the BSR-based temperatures are about 2 °C higher than the model: Especially in (1) near a fault zone, (2) under the eastern flank where there are strong seismic reflectors in a pseudo-3D seismic dataset, and (3) near a fissure zone. For the Formosa Ridge, our results showed a distinct decrease in temperatures around the southern peak of the ridge, where an active gas plume was found. BSR-based temperatures predict on average 2 °C lower than the model. At these two sites, the shallow temperature fields are strongly affected by 2D bathymetry. However, new insights regarding fluid flow patterns can be obtained using this model approach.     

塔里木盆地西北缘奥陶系碳酸盐岩中两种来源热流体的地质与地球化学证据

塔里木盆地西北缘西克尔-巴楚-柯坪地区处于巴楚-柯坪断隆带活动区,构造活动强烈.该区出露的中下奥陶统鹰山组发育大量的热液蚀变现象,既有溶蚀形成的大小孔洞、疏松灰岩层,也有各类充填的脉体,如萤石矿、硫磺石膏矿等.通过野外露头观察和采样,并对受热流体作用的样品进行了包裹体测温测盐、微量元素和硫同位素分析.结果显示研究区主要有两种流体来源:岩浆热液和地层热液.研究表明:(1)岩浆热液主要影响研究区南西段,形成萤石、重晶石、方铅矿等矿物,流体包裹体盐度低(0.5％ ～7.5％ NaCleqv)、均一化温度相对较高(142 ～ 283℃);地层热液作用范围则主要位于研究区北东段,生成白云石、方解石、石英等矿物,流体包裹体盐度高(16％ ～ 23.3％ NaCleqv)、均一化温度低(70～ 138℃);而研究区中段同时受到两种来源热液的混合作用,包裹体盐度(7.5％～18.3％ NaCleqv)和均一化温度(142 ～ 163℃)介于前两者之间;(2)热液硬石膏、硫磺的硫同位素富含32S,δ4S平均为-9.57％,说明硬石膏是H2S气体与灰岩反应的产物,硫化氢很可能来自有机物的热裂解.     

粤北盆地流体系统及其矿化特征

盆地构造演化流体系统矿化作用是当代矿床学研究的新课题。盆地演化过程 ,压实流体系统温度场、动力场和地球化学场可以通过地质研究和数字模拟来重塑。粤北晚古生代沉积盆地存在 3种类型的矿化流体。大宝山型流体与岩浆热动力作用有关 ,形成海底火山热液沉积多金属矿床 ;凡口型流体与深部建造的循环热液有关 ,形成中低温海底热泉喷溢沉积铅锌银汞矿床 ;红岩型流体与盆地成岩压实水有关 ,形成低温单一黄铁矿矿床。红岩地区盆地压实流体系统在盆缘古隆起地段形成红岩型黄铁矿矿带的同时 ,还形成特征的白云岩化作用。白云岩产状和组构、白云石“亮边”和“雾心”特征及地球化学特征表明 ,红岩型诸矿床的成因与盆地沉积物压实过程形成的流体有关     

Fluid inclusion evidence for barbotage and its role in gold deposition at the Darasun goldfield (Eastern Transbaykalia,Russia)

“Barbotage” is a process of gas penetration through a layer of liquid as a flow of dispersed small gas bubbles. Barbotage is widely used in technology particularly due to its high coefficients of interphase energy and material transfer. It promotes the heat- and mass-exchange processes as well as the chemical interactions in gas-liquid systems. Upon investigation of the fluid regime at the magmatic-hydrothermal system of Darasun goldfield (Eastern Transbaikalia, Russia) we have found evidences of barbotage as an effective mechanism resulting in the formation of vein gold deposits. In spite of the fact that early associations of gold ores in the Darasun goldfield deposits were formed from a heterogeneous fluid, their histograms of fluid salinity distributions are quite different. These differences can be explained by including into the ore-forming process the stage at which the vapour phase generated by boiling rose up as a stream of small bubbles. The corresponding scheme of the formation of the Darasun goldfield hydrothermal ore-bearing system is proposed and discussed. The possibility to use gallium fractionation and the fluid salinity distribution in hydrothermal systems as the indicators of barbotage participation in hydrothermal ore-forming processes is evaluated.     

粤北晚古生代盆地压实流体的性状

盆地构造演化、流体系统、矿化作用是当代矿床学研究的新课题。盆地演化过程中,压实流体系统温度场、动力场和地球化学场可以通过地质研究和数字模拟来重塑。粤北晚古生代沉积盆地存在三种类型的矿化流体。大宝山型流体与岩浆热动力作用有关,形成海底火山热液沉积多金属矿床;凡口型流体与深部建造的循环热液有关,形成中低温海底热泉喷溢沉积铅锌银汞矿床;红岩型流体与盆地成岩压实水有关,形成低温单一黄铁矿矿床。粤北晚古生代盆地沉积物主要由透水性较好的粗碎屑物质和碳酸盐组成,沉积建造厚度较薄,数字模拟结果表明,盆地压实流体系统难以形成较高的地热储和流体势,不可能形成自身的突发喷溢。但在同生断裂作用引导下,流体在沉积层的特殊部位汇聚形成红岩型低温黄铁矿矿床。     

Thermo-hydro-mechanical modeling of fracturing porous media with two-phase fluid flow using X-FEM technique

In this paper, a fully coupled thermo-hydro-mechanical model is presented for two-phase fluid flow and heat transfer in fractured/fracturing porous media using the extended finite element method. In the fractured porous medium, the traction, heat, and mass transfer between the fracture space and the surrounding media are coupled. The wetting and nonwetting fluid phases are water and gas, which are assumed to be immiscible, and no phase-change is considered. The system of coupled equations consists of the linear momentum balance of solid phase, wetting and nonwetting fluid continuities, and thermal energy conservation. The main variables used to solve the system of equations are solid phase displacement, wetting fluid pressure, capillary pressure, and temperature. The fracture is assumed to impose the strong discontinuity in the displacement field and weak discontinuities in the fluid pressure, capillary pressure, and temperature fields. The mode I fracture propagation is employed using a cohesive fracture model. Finally, several numerical examples are solved to illustrate the capability of the proposed computational algorithm. It is shown that the effect of thermal expansion on the effective stress can influence the rate of fracture propagation and the injection pressure in hydraulic fracturing process. Moreover, the effect of thermal loading is investigated properly on fracture opening and fluids flow in unsaturated porous media, and the convective heat transfer within the fracture is captured successfully. It is shown how the proposed computational model is capable of modeling the fully coupled thermal fracture propagation in unsaturated porous media.     

东营凹陷热流体活动及其对水-岩相互作用的影响

从气体地球化学、有机质热变、包裹体均一温度、古地温梯度、成岩矿物、重金属元素和岩浆活动等方面证实了东营凹陷发生了大量的热流体活动.热流体主要沿活动性较强的深大断裂运移至浅部, 并以侧向强迫对流为主, 同时具有多期次活动的特点.热流体通过改变温度场和地温梯度以及带入一些无机物质, 导致水-岩相互作用强度和类型的差异.