南海北部边缘盆地泥底辟及泥火山特征及其与油气运聚关系

泥底辟与泥火山成因机制相同,发育演化特征相似,但最终地质形态及存在形式有所差异.通过深入分析南海西北部莺歌海盆地泥底辟与东北部台西南盆地泥火山发育展布特点及伴生天然气地球化学特征,指出莺歌海盆地泥底辟主要分布于盆地中部的莺歌海深大凹陷,且沿盆地NW方向呈五行雁行式排列,泥底辟发育演化具有明显的低密、低速和异常高温超压的特点;而台西南盆地泥火山主要展布于南部凹陷陆坡深水区和台湾陆上台南-高雄地区,陆上泥火山多沿深大断裂带分布,地面形态特征类似火山形态,多具有喷口,海域泥火山的海底形态亦与其相似,但研究程度较低.泥底辟及泥火山伴生烃类天然气成因类型较多,但以成熟-高熟煤型烃类气为主;伴生的非烃气CO₂和N₂丰富,但以无机壳源型CO₂为主.泥底辟及泥火山的泥源层均为中新世及上新世海相坳陷沉积的巨厚泥页岩,本身即具生烃潜力,其成熟生烃及其与泥底辟/泥火山运聚通道和底辟伴生构造的良好配置,则构成了其独特的泥底辟/泥火山油气运聚成藏系统,进而控制了这种“泥底辟/泥火山型油气藏”的分布.      

莺歌海盆地泥底辟发育演化与油气运聚机制

第三系泥底辟是莺歌海盆地非常独特的地质体，其发育演化与烃类及流体的生、排、运、聚以及塑性泥的流动，均存在直接的成因联系。泥底辟是一个独立、完整的油气生、运、聚体系，或即油气运聚的封闭箱或封存箱，其烃类及流体运聚和塑性泥质物的流动均与该封闭体系（封闭箱）顶封闭层的形成与破坏密切相关，亦即顶封层的破裂刺穿与保存完整与否，直接控制了烃类及流体的运聚机制及模式和塑性泥的流动方式与形态特征。籍此，总结出两种不同的油气运聚机制及模式。     

丽水-椒江凹陷新生代构造应力场数值模拟与油气运聚关系探讨

根据前人对东海丽水-椒江凹陷地质研究成果和最新资料,指出新生代的丽水-椒江凹陷主要处于张性应力场中,应力场是控制该区油气运聚的主要因素。采用Maxwell粘弹性模型,对新生代古构造应力场进行了数值模拟。模拟结果表明瓯江运动期,丽水-椒江凹陷处于一种右旋拉张环境;玉泉期的丽水-椒江凹陷处于一种比较稳定的弱拉张环境。研究表明丽水西次凹LS36-1-1井以西,MYF-1井以南的缓坡带是比较有利的油气勘探区域。灵峰凸起带因为应力值偏高有可能导致运移到此处的油气已经沿断层逸散或者被破坏。     

四川盆地晚三叠世动力学特征及与油气运聚的关系

晚三叠世是四川盆地形成演化的起点,其地层是油气勘探的一个重要目标层。通过对四川盆地晚三叠世动力学特征的分析,建立其动力学模型（构造应力（叠加）场模型）,采用有限单元法进行模拟,其结果显示,四川盆地晚三叠世构造应力条件以ＮＷ—ＳＥ方向的挤压占主导。构造动力是油气运聚的驱动力,驱使油气运移的动力来自构造应力场,通过模拟认为,四川盆地晚三叠世构造应力场形成的圈闭为模拟计算的最大应力值２．０～４．０ＭＰａ之间的区域。     

长岭断陷龙凤山地区断裂与油气运聚的关系

长岭断陷龙凤山地区具有“下生上储、他源成藏”特征,明确断裂与油气运聚的关系对指导其油气勘探具有重要意义.在分析断裂静态特征的基础上,分别定量评价断裂的活动性、封闭性以及断-盖配置关系,并提出了评价断-盖配置有效性的“SGR下限”法(SGR全称是Shale Gouge Ratio),结合油气藏静态分布特征,探讨了断裂对油气差异聚集的控制作用.研究结果表明,第1期油气成藏早中期,断裂可大规模输导油气;第1期晚期及第2期油气成藏时,主干反向断裂形成的封闭“走廊”空间为油气提供聚集场所.应用“SGR下限”法,认为营Ⅲ砂组断-盖配置关系较好,为油气提供良好的保存条件.断裂控烃作用体现在3个方面,断裂的活动性控制了油气不同时期的垂向运移规模,断裂的封闭差异性控制了油气富集程度,断-盖配置关系控制了油气的富集层系.      

长白山天池及邻区次生火山灾害类型、分布及其与火山地质的关系

基于对长白山天池及邻区火山地质和次生火山灾害的编图结果,从岩性、断裂、地形地貌和水系等方面,分析火山喷出物的地质特征与这些火山物质所导致的次生火山灾害之间的相关性。研究表明,崩塌发生在柱状节理发育的硬质岩中,多期火山喷发以及伴生的地震活动剥蚀掏空坚硬岩层间的松散堆积体,使岩体失稳发生崩塌,局部陡崖地貌在地震影响下亦会发生崩塌灾害。软质岩和松散堆积体受流水侵蚀,河谷下切,河流两岸斜坡前缘形成开阔的滑动空间,火山地震引起山体变形,斜坡岩体结构遭到破坏发生滑坡灾害。火山先期喷出的碎屑物和崩塌滑坡产生的碎石是火山泥石流的重要物质来源,火山喷发或强地震引发的洪水灾害以及地形地貌对火山泥石流的形成、搬运和分布范围起关键性作用。     

准噶尔盆地陆梁隆起不整合面与油气运聚关系

准噶尔盆地陆梁隆起不整合面十分发育,且与油气运聚关系非常密切：二叠系、三叠系底不整合面是该区侏罗纪末成藏的主控因素,侏罗系底不整合面是深部油气进入该系的有利通道,而白垩系底不整合面又是油气顺利从侏罗系进入白垩系的必要条件。研究区的不整合面有褶皱、断褶、超覆、削截、平行5种类型,各种类型的不整合面对研究区油气运聚作用也有着差异,其中断褶不整合面对油气的垂向运移与聚集作用最大,是研究区最为典型的油气成藏方式。不整合面的分布具有差异性、继承性、迁移性,三性对油气的演化和分配有着影响作用。     

松辽盆地东岭区块油气运聚特征及成藏主控因素研究

为了使东岭区块油气勘探早日获得突破,本次研究以成盆、成烃和成藏理论为指导,采用有效烃源岩评价、沉积微相分析以及流体包裹体分析等技术和方法,综合研究分析了松辽盆地东岭区块油气成藏条件,提出了有利勘探区带和目标.     

冀中坳陷束鹿凹陷潜山不整合特征与油气运聚模式

本文从冀中坳陷束鹿凹陷潜山顶面不整合接触类型及分布规律、结构特征及输导类型出发,精细刻画了不整合面之下半风化岩石层的垂向岩溶分带特征。在此基础上对典型剖面烃源岩热演化、油气运移进行模拟,建立了研究区潜山油气的运聚模式。结果表明,束鹿凹陷潜山顶面不整合包括4种接触类型、5种结构模式,具有3种输导类型,其中斜坡区和洼槽区西部以侧向型为主,斜坡区局部构造高点与洼中隆为侧向+圈闭型,凸起区以侧向+垂向型为主。不整合面之下半风化岩石孔缝洞体系发育,垂向上可划分为表层岩溶带、垂直渗流带以及三个水平潜流带,具有多期岩溶旋回特征。潜山顶部发育的垂直渗流带是油气沿不整合面运移的主力输导层,而内幕发育的多期水平潜流带是油气向内幕运移的潜在通道。深、浅部烃源岩热演化的差异以及与薄层砾岩是否接触导致了斜坡区与洼中隆潜山油气充注的差异,形成了斜坡区晚期薄层砾岩高效中转、不整合侧向运移、水平潜流带向内幕输导、顺向断层向上输导、反向断层圈闭成藏的油气运聚模式。     

Mathematical model of accumulation of gas hydrates associated with deep-sea mud volcanoes

Doklady Earth Sciences - A new model that can account for accumulations of gas hydrates associated with submarine mud volcanoes and based on the available data on these gas hydrates is proposed....     

Gases in Taiwan mud volcanoes: Chemical composition,methane carbon isotopes,and gas fluxes

Mud volcanoes are important pathways for CH₄ emission from deep buried sediments; however, the importance of gas fluxes have hitherto been neglected in atmospheric source budget considerations. In this study, gas fluxes have been monitored to examine the stability of their chemical compositions and fluxes spatially, and stable C isotopic ratios of CH₄ were determined, for several mud volcanoes on land in Taiwan. The major gas components are CH₄ (>90%), “air” (i.e. N₂ + O₂ + Ar, 1–5%) and CO₂ (1–5%) and these associated gas fluxes varied slightly at different mud volcanoes in southwestern Taiwan. The Hsiao-kun-shui (HKS) mud volcano emits the highest CH₄ concentration (CH₄ > 97%). On the other hand, the Chung-lun mud volcano (CL) shows CO₂ up to 85%, and much lower CH₄ content (<37%). High CH₄ content (>90%) with low CO₂ (<0.2%) are detected in the mud volcano gases collected in eastern Taiwan. It is suggestive that these gases are mostly of thermogenic origin based on C₁ (methane)/C₂ (ethane) + C₃ (propane) and δ¹³C_CH4 results, with the exception of mud volcanoes situated along the Gu-ting-keng (GTK) anticline axis showing unique biogenic characteristics. Only small CH₄ concentration variations, <2%, were detected in four on-site short term field-monitoring experiments, at Yue-shi-jie A, B, Kun-shui-ping and Lo-shan A. Preliminary estimation of CH₄ emission fluxes for mud volcanoes on land in Taiwan fall in a range between 980 and 2010 tons annually. If soil diffusion were taken into account, the total amount of mud volcano CH₄ could contribute up to 10% of total natural CH₄ emissions in Taiwan.     

Active mud volcanoes on- and offshore eastern Makran, Pakistan

To study the activity, source and driving force of the venting of fluidized mud in the coastal Makran, we carried out reconnaissance surveys of two active onshore mud volcano fields (Chandragup and Jebel-u-Ghurab) and of a newly born (March 1999) offshore mud volcano (Malan Island). All studied on- and offshore mud volcanoes line up along one southwest/northeast-trending structural lineament, the axis of the Dhak Anticline. Isotopic data point to a bacterial origin of the gas (mainly methane). Mixed benthic foraminiferal faunas and calcareous nannofloras suggest that the source level of the extruded mud is at a sub-surface depth of 2-3 km. Observed mud discharge varied between 0 and 1.4 m³ h^-1 and gas discharge rates between negligible amounts to 1 m³ s^-1. Mud temperatures in the crater lake of Chandragup I are near-ambient temperatures. They rise slightly (Б.5°C) during episodes of modest mud outflow. An area of 160,000 m³ of soft mud was vigorously extruded from the sea floor at a water depth of 10 m within days after 15 March 1999, forming Malan Island. The island was destroyed within a few months after its birth by deep-reaching wave action during the SW monsoon. This was possibly aided by local subsidence of the mud volcano structure due to the volume loss following rapid degassing and mud extrusion.     

Distribution and characters of the mud diapirs and mud volcanoes off southwest Taiwan

In order to identify the mud diapirs and mud volcanoes off SW Taiwan, we have examined ∼1500 km long MCS profiles and related marine geophysical data. Our results show ten quasi-linear mud diapirs, oriented NNE–SSW to N–S directions. Thirteen mud volcanoes are identified from the multibeam bathymetric data. These mud volcanoes generally occur on tops of the diapiric structures. Moreover, the active mud flow tracks out of mud volcanoes MV1, MV3 and MV6 are observed through the high backscatter intensity stripes on the sidescan sonar images. The heights of the cone-shaped mud volcanoes range from 65 m to 345 m, and the diameters at base from 680 m to 4100 m. These mud volcanoes have abrupt slopes between 5.3° and 13.6°, implying the mudflow is active and highly viscous. In contrast, the flat crests of mud volcanoes are due to relative lower-viscosity flows. The larger cone-shaped mud volcanoes located at deeper water depths could be related to a longer eruption history. The formation of mud diapirs and volcanoes in the study area are ascribed to the overpressure in sedimentary layers, compressional tectonic forces and gas-bearing fluids. Especially, the gas-bearing fluid plays an important role in enhancing the intrusion after the diapirism as a large amount of gas expulsions is observed. The morphology of the upper Kaoping Slope is mainly controlled by mud diapiric intrusions.     

Gases of mud volcanoes in the Copper River Basin,Alaska

The gases emitted from mud volcanoes in the Copper River Basin of Alaska fall into two distinct types which are not mixed during vertical migration. The gases in the eastern volcanoes are nearly pure carbon dioxide, whereas the western ones contain methane and nitrogen and almost no carbon dioxide. Chemical and carbon isotopic compositions suggest the carbon dioxide rich gases originated by solution of limestones and that methane rich gases probably formed by thermal decomposition of coals.Permafrost may be a strong factor in separating the Copper River Basin gases. Extending downward for several hundred feet, the permafrost would prevent shallow lateral migration and focus the energy of the gas into occasional mud volcano vents. Soil gas analyses show rapidly decreasing amounts of the methane to about 150 m and of carbon dioxide to about 20–40 m away from the mud volcano pools. Isotopic variations of these natural methane and carbon dioxide gases, which are not intermixed, indicate that calculations of formation temperatures based on δ¹³C ratios cannot be used generally.     

Calculating depth of deposition and volume of gas expelled during eruptions of mud volcanoes in southern Sakhalin

The geological structure of mud volcanoes in southern Sakhalin is stated briefly. Character of eruptions and opinions on the mechanism of the origin of eruptions are described, as well as approximate estimations of depths of occurrence of the gas deposit and the volume of exploding gas. – Authors.     

藏北羌塘中部首次发现泥火山

青藏高原羌塘中部戈木错新生代盆地首次发现大量泥火山,少数泥火山喷发物中有含沥青脉的岩石。区内泥火山群出露在第四纪沉积物之上,明显受新构造断裂活动的控制。喷发物中含沥青脉岩石泥火山的发现说明羌塘中部曾经发生过大规模的油气运聚活动,沥青脉赋存在古近纪唢呐湖组湖相灰岩的层间裂隙中,为层间缝型沥青脉。泥火山喷出物中含沥青脉岩石的发现说明羌塘新生代沉积盆地具有良好的油气前景。