A NEW SCHEME FOR THE FORMATION AND CLASSIFICATION OF BITUMENS

This paper discusses models of bitumen formation. Most liquid bitumens are formed during the middle stages of catagenesis (between approx. Ro equivalents of 0.4 and 1.15, respectively). "Progressive" naphthide formation is a process whereby organic matter and its derivatives gradually pass through a number of stages of alteration — three stages are generally recognized. By contrast , "regressive" naphthide formation is a "superimposed" process, involving microbial alteration and biochemical oxidation.
In addition to the above two general processes, three other, less important schemes of naphthide formation are recognised:
"Pyrodestructive bitumogenesis" results in the formation of "naphthoids"; these are bitumens generated close to an intruded heat source, which causes thermal destruction of organic matter.
"Dynamic-hydrothermal bitumogenesis" results in the generation of a complex group of bitumens, known as "naphthido-naphthoids", which are formed under conditions of dynamic metamorphism and hydrothermal activity accompanied by metasomatism.
Thirdly, the process of "phase-migrational" bitumogenesis results in the formation of two groups of bitumens: "asphaltenites" and "beta-asphaltenites".
This paper summarizes the Author's views on bitumen formation, based on new geological and geochemical data.     

PETROLEUM POTENTIAL, THERMAL MATURITY AND THE OIL WINDOW OF OIL SHALES AND COALS IN CENOZOIC RIFT BASINS, CENTRAL AND NORTHERN THAILAND

Oil shales and coals occur in Cenozoic rift basins in central and northern Thailand. Thermally immature outcrops of these rocks may constitute analogues for source rocks which have generated oil in several of these rift basins. A total of 56 oil shale and coal samples were collected from eight different basins and analysed in detail in this study. The samples were analysed for their content of total organic carbon (TOC) and elemental composition. Source rock quality was determined by Rock‐Eval pyrolysis. Reflected light microscopy was used to analyse the organic matter (maceral) composition of the rocks, and the thermal maturity was determined by vitrinite reflectance (VR) measurements. In addition to the 56 samples, VR measurements were carried out in three wells from two oil‐producing basins and VR gradients were constructed. Rock‐Eval screening data from one of the wells is also presented. The oil shales were deposited in freshwater (to brackish) lakes with a high preservation potential (TOC contents up to 44.18 wt%). They contain abundant lamalginite and principally algal‐derived fluorescing amorphous organic matter followed by liptodetrinite and telalginite (Botryococcus‐type). Huminite may be present in subordinate amounts. The coals are completely dominated by huminite and were formed in freshwater mires. VR values from 0.38 to 0.47%R_o show that the exposed coals are thermally immature. VR values from the associated oil shales are suppressed by 0.11 to 0.28%R_o. The oil shales have H/C ratios >1.43, and Hydrogen Index (HI) values are generally >400 mg HC/g TOC and may reach 704 mg HC/ gTOC. In general, the coals have H/C ratios between about 0.80 and 0.90, and the HI values vary considerably from approximately 50 to 300 mg HC/gTOC. The HI_max of the coals, which represent the true source rock potential, range from ～160 to 310 mg HC/g TOC indicating a potential for oil/gas and oil generation. The steep VR curves from the oil‐producing basins reflect high geothermal gradients of ～62°C/km and ～92°C/km. The depth to the top oil window for the oil shales at a VR of ～0.70%R_o is determined to be between ～1100 m and 1800 m depending on the geothermal gradient. The kerogen composition of the oil shales and the high geothermal gradients result in narrow oil windows, possibly spanning only ～300 to 400 m in the warmest basins. The effective oil window of the coals is estimated to start from ～0.82 to 0.98%R_o and burial depths of ～1300 to 1400 m (～92°C/km) and ～2100 to 2300 m (～62°C/km) are necessary for efficient oil expulsion to occur.     

西北侏罗系煤成油研究中的煤田地质学方法

运用煤田地质学方法分析、研究了西北侏罗系盆地的煤沼沉积环境演化类型(以下简称煤沼演化类型),划分出:①没有发育湖相建造;②含煤建造上覆缺失湖相建造;③具有完整湖平面变化旋四层序的三种煤沼演化类型;研究了西北侏罗系含煤盆地,尤其是第二和第三煤沼演化类型的煤显微组分组成和烃源岩的成熟度特征.根据西北侏罗系含煤盆地煤成油田形成和分布规律,依据煤沼演化类型、盆地沉积构造背景、有机岩组成特征等条件,提出了天山及其以北和塔里木周缘和祁连山两侧山前的前陆盆地等同沉积构造活动性较强的盆地是西北侏罗系煤成油勘探的有利区域,发育第一和第二煤沼演化类型的盆地及其伊犁和三塘湖盆地没有找到煤成油田的可能的看法.     

GEOLOGIC TIME AS A PARAMETER IN ORGANIC METAMORPHISM AND VITRINITE REFLECTANCE AS AN ABSOLUTE PALEOGEOTHERMOMETER

Substantial published and unpublished data contradict accepted laws of organic metamorphism. Significant amounts of C₁₅₊ hydrocarbons and kerogen with significant generation potential exist in sediments which have been buried at high temperatures for long periods of geologic time. Graphite formation and greenschist metamorphism do not occur at model-predicted burial times and temperatures. Maturation levels for sediments with long (up to 240 million years) burial times are much lower than expected, and conversely, higher than expected for sediments with short (2 million years) burial times. The threshold of intense petroleum generation is not detectable in Plio-Miocene sediments at minimum temperatures of 160° C. Literature examination reveals that the only solid documentation of time as a controlling parameter in organic metamorphism is in the works of Karweil (1955), Lopatin (1971) and Connan (1974). Scrutiny of these authors' study areas reveals that all have had moderate to extreme paleogeothermal gradients from incipient and aborted rifting, extrusive and intrusive igneous activity, hydrothermal activity, orogenesis and/or uplift and erosion. Levels of organic metamorphism attributed to geologic time by the above authors are better explained by high paleogeothermal gradients resulting from major geologic activity. Mean vitrinite reflectance (R_O) data have been compiled from different sedimentary basins currently at or near maximum geothermal gradients with sediment burial times ranging from 2–240 million years. The R_O data from these basins show a strong correlation (r = 0.97) of increase in R, with increase in temperature. These same data show no correlation of increasing Ro with increasing burial times for any temperature interval. R, data from sedimentary basins affected by high-temperature geothermal systems with heating times of only 1,000–10,000 years overlie R, data from these petroleum-bearing sedimentary basins with burial (heating) times of 2–240 million years. Contrary to accepted thought, there is no evidence from the natural system that petroleum generation-maturation reactions have first-order reaction kinetics. By contrast, a substantial body of evidence from petroleum generation-maturation laboratory studies carried out in closed water- wet systems show that these reactions are characterized by multiple-order reaction kinetics. Geologically older sediments clearly tend to be more organically mature than younger sediments at the same burial temperatures. However, this correlation ismorea reflection that older sediments have had a greater chance of being affected by a major geologic event with an accompanying high heat flow. The major conclusions of this paper are that: (1) geologic time has no observable effect on organic metamorphism; (2) vitrinite reflectance can be used as an absolute paleogeothermorneter; and (3) the accepted models of organic metamorphism at the very least need substantial revision.     

Specifics of the hydrocarbon and trace-element composition of oils and condensates from shallow-water marine deposits

Using the data for the oil fields of the Southern Caspian (Azerbaijan, Western Turkmenistan, Georgia) and Northern Caucasian-Mangyshlak (Ciscaucasia) oil-and-gas bearing basins (OGB) as an example, the investigational results for immature oils and condensates generated by the organic matter (OM) of both shallow marine and coastal-deltaic facies have been summarized. The physicochemical properties and the hydrocarbon and trace-element compositions of oils and condensates have been considered and their key features have been revealed. It has been shown that these oil and condensate parameters are related to the composition of the source OM and the multistage character of its transformation. In other words, the whole variety of geological processes pertaining to the burial and transformation of the original, oil-generating source OM is reflected in the geochemical features of oils and condensates, thereby giving another important and convincing piece of evidence for the organic origin of oil.     

原始有机质丰度的恢复及其意义

本文利用能反映有机质(碳)量随成熟度和有机质类型而变化的热模拟实验数据和松辽盆地泥岩岩体质量随埋深(成熟度)而变化的实际观测数据,通过逐步回归分析将原始有机碳(C~0)丰度定量地表述为不溶残碳(D_K)、有机质类型(KTI)和成熟度(R_0)的函数,达到了定量恢复原始有机质丰度的目的。在松辽盆地初步应用,效果比较理想,并可以近似地应用于其它盆地。     

海拉尔盆地乌尔逊及贝尔凹陷烃源岩有机质丰度的恢复

在综合分析已有有机质丰度恢复方法的基础上,对各种方法进行了系统的分类,并综合对比了各种方法的优缺点及适用条件,认为热解模拟实验方法是一种相对较好的有机质丰度恢复方法.利用该方法对海拉尔盆地乌尔逊凹陷和贝尔凹陷的5套源岩的有机碳进行了恢复,并对资源量进行了校正.结果表明:乌尔逊凹陷和贝尔凹陷的有机碳恢复系数分别在1.10~1.32和1.03~1.18之间,各套源岩的恢复系数并不一致;恢复后的总资源量增加了1.86×108t.不难看出,有机质丰度的恢复对于含油气盆地评价,具有十分重要的意义.对于源岩演化程度相对较高的沉积盆地进行评价,尤其应该重视有机质丰度恢复研究.      

Geochemical features of low-mature lacustrine oils of China

Data on the physicochemical properties and the hydrocarbon and trace-element compositions of hydrocarbon fluids from various oil and gas basins in China have been analyzed and summarized. The distribution of a wide range of hydrocarbon biomarkers in crude oils has been correlated with the salinity of lacustrine sediments. The variety of facies that characterize the burial and transformation of the original hydrocarbon-generating organic matter is reflected in particular features of oil composition. The parameters identified are recommended for geochemical correlation of crude oils with rock organic matter and for prediction of the physicochemical properties or the hydrocarbon and trace-element compositions of oil accumulations.     

中国陆相湖盆致密油成藏主控因素综述

致密油是指致密储层中的石油聚集,储层主要为致密砂岩和碳酸盐岩2大类,覆压渗透率多小于0.1×10-3μm2,一般无自然产能,需经技术改造方能获工业油流。我国主要发育陆相湖盆致密油藏,通过对比研究分析发现,发育优质烃源岩、存在"甜点区"、具备成藏原动力、近源聚集是我国陆相致密油成藏的主要条件。我国陆相致密油主要发育2类优质烃源岩:Ⅰ类烃源岩有机质类型好、丰度高,有机质成熟度高,生烃潜力大;Ⅱ类烃源岩生烃转化率较高。发育致密砂岩和碳酸盐岩2类储层,储层具有较强的非均质性,横向不连续,垂向叠置分布。生烃增压是我国陆相致密油成藏的主要原动力,强大的源储压差驱替生成的石油向紧邻优质烃源岩的致密储层中持续充注;其中,微裂缝沟通、微—纳米孔发育是致密油运移聚集的关键。微—纳米孔发育增大了致密储层的有效储集空间,微裂缝沟通为致密油的运移聚集提供了有效通道。我国陆相致密油资源丰富,初步预测其有利勘探面积约16×104km2,地质资源量约(160~200)×108t,有利勘探领域主要分布在鄂尔多斯、准噶尔、松辽、渤海湾、柴达木、四川等盆地。     

有机碳测井评价方法在断陷盆地中的应用

1. Introduction The total organic carbon content (TOC) is estimated traditionally by measuring cores, cuttings or sidewall cores in laboratory with source rock evaluation instruments. Limited by the number of rock samples, the experimental results are not…     

ORGANIC FACIES VARIATIONS AND HYDROCARBON GENERATION POTENTIAL OF PERMIAN GONDWANA GROUP COALS AND ASSOCIATED SEDIMENTS,BARAPUKURIA AND DIGHIPARA BASINS,NW BANGLADESH

In the Barapukuria and Dighipara coal basins, NW Bangladesh, the Basement Complex is overlain by the coal‐bearing Permian Gondwana Group. In the present study, 36 core samples collected from five boreholes in these two basins were analysed using organic geochemical and organic petrological methods. Based on the results of biomarker analyses (TIC, m/z 191 and m/z 217 fragmentograms) and maceral composition (proportions of vitrinite, liptinite, inertinite), three organic facies were identified: coals, carbargillites and mudstones. Together with other evidence, cross‐plots of HI versus T_max and Pr/nC₁₇ versus Ph/nC₁₈ indicate that the coals, as expected, were dominated by terrestrial organic matter (OM). The carbargillites contained a mixture of terrestrial and probable Type II aquatic OM, and the mudstones contained mostly terrestrial OM. Accordingly the coals, carbargillites and mudstones are interpreted to have been deposited in swamp‐dominated environments in a delta‐plain setting which was subject, in the case of carbargillites, to periodic flooding. Suboxic conditions were indicated by very high Pr/Ph ratios and a high content of inertinite macerals. All the samples analysed were immature or early mature for hydrocarbon generation, as indicated by mean vitrinite reflectance (%R_o) of 0.60–0.81%, Rock‐Eval T_max of 430–439°C, and biomarker ratios (hopane C₃₂ 22S/(22S+22R)) of 0.57–0.60. Carbargillites showed potential for both liquid and gaseous hydrocarbon generation; coals were mainly gas‐prone with minor liquid hydrocarbon potential; and mudstones were dominantly gas‐prone. The oil‐prone nature of the samples was attributed to the presence of resinite, cutinite, bituminite and fluorescent vitrinite. The presence of exsudatinite within crack networks, solid bitumen and oil droplets as well as bituminite at early oil‐window maturities suggests that the organic matter may have expelled some hydrocarbons.     

中国西北地区侏罗纪煤系油气形成（之三）

西北地区侏罗纪煤系中主要成烃显微组分是孢子体、角质体、藻类体、沥青质体、碎屑类脂体和基质镜质体等，木栓质体和树脂体等早期成烃组分含量极低。侏罗纪煤系有机质成烃演化特征与一般湖相有机质稍有差异，但基本上仍然遵循一般有机质热降解成熟生油模式，主要生油阶段的Ｒｏ值为０．７％～１．２％，生油高峰Ｒｏ值约为０．９５％。目前西北地区侏罗纪煤系烃源岩Ｒｏ值一般为０．４％～１．３％，多数地区成熟度较低，在山前深坳陷地区成熟度较高，烃源岩Ｒｏ值大于０．７％，进入大量生油阶段，西北地区主要煤系含油气盆地油气田均分布于这些地区，烃源岩成熟度对油气田形成有明显的控制作用。西北地区侏罗系有利的生烃区域基本分布在侏罗纪是沉降、沉积中心而后续埋藏又较深的山前坳陷。图４表１参４５（王孝陵摘）     

电测井资料在生油岩评价中的应用

本丈主要利用电测井资料对生油岩类型、有机质成熟度和烃类生成进行判断,从而为生油岩评价开辟了新途径.通过对辽河外围盆地张强地区有机质成熟度初步判断,收到了良好的效果,展示了测井资料在生油岩评价中的广阔前景.      

潮水盆地和民和盆地中侏罗统青土井组煤系烃源岩有机地球化学特征及其意义

随着非常规油气资源开采技术进步以及勘探范围日益扩大,煤系烃源岩日益获得重视。潮水盆地和民和盆地作为甘肃陇中、河西地区的典型侏罗系含煤沉积代表,其生烃能力及其差异性特征研究相对欠缺,为此对两地区煤系烃源岩展开综合有机地球化学参数特征及其对比研究。生物标志物特征指示:潮水盆地青土井组煤系烃源岩有机质来源以混合输入为主,处于低熟-成熟阶段,沉积环境上段为弱氧化-弱还原滨、浅湖相,下段为弱咸化半深湖-深湖相,出现高伽马蜡烷优势,指示水体出现分层现象;民和盆地窑街组煤系烃源岩有机质来源上段以低等水生生物输入为主,下段为陆相高等植物优势输入,有机质处于低熟-成熟阶段,沉积环境倾向于典型沼泽相煤系沉积。有机质丰度和类型数据揭示:潮水盆地烃源岩有机质类型主要为Ⅱ型;民和盆地烃源岩有机质类型Ⅰ型、Ⅱ型及Ⅲ型均有出现。综合分析各项有机地球化学参数,指示潮水盆地和民和盆地均具有一定生烃潜力,相对来说以低等水生生物输入为主的民和盆地煤系烃源岩可能具有相对较大的生液态烃潜力。     

南沙海域新生代构造运动特征

根据南沙海域丰富的地球物理资料和调查结果 ,对南沙海域各盆地区域不整合面及与之对应的构造运动的特征进行了探讨 ,认为自中生代末期以来本区发生过 4次重要的构造运动 :礼乐运动、西卫运动、南海运动和南沙运动 ,它们对南沙海域盆地的形成、沉积和构造演化起到了重要的控制作用。礼乐运动和西卫运动主要表现为拉张性质 ,礼乐运动造成盆地初始裂离、断陷 ,西卫运动使盆地断陷、断拗加剧 ;南海运动使盆地由断拗逐渐转化为拗陷 ;南沙运动主要表现为挤压性质 ,该时期所形成的构造圈闭是油气勘探的主要目标     

蒸发岩发育特征及其对大油气田形成的影响

蒸发岩广泛发育于全球各含油气盆地之中,其发育分布特征与世界大油气田的形成和分布有着密切的关系。通过对全球气候条件、海平面相对变化以及各类型盆地进行研究,分析了蒸发岩的发育特征,盆地内部的限制性洼地、相对停滞的水体以及干旱炎热的气候等共同制约着蒸发岩的形成与分布。通过对蒸发岩封盖能力、热导率以及非能干性的研究,结合东西伯利亚、坎波斯以及扎格罗斯等盆地中大油气田实例,分析了蒸发岩层对大油气田形成的影响。蒸发岩的致密性作为盖层有效地封盖了下伏油气,其热导率又有利于保持温度均衡,使得有机质能够更为彻底地转化;蒸发岩的非能干性使其易于发生滑脱变形,导致上覆储集层裂缝系统发育,极大地改善了其储集性能;蒸发岩强烈变形还可以形成盐构造,为油气聚集形成新的圈闭;蒸发岩的发育在时间上和空间上都制约着全球大油气田的形成与分布。随着油气勘探的不断深入,将会发现越来越多的与蒸发岩有关的大油气田。     

盆地地球物理初探

应用地球物理信息并结合地质资料进行盆地实体的构造发育史、沉降堆积史及其所受的各种动力作用等方面的研究是盆地地球物理工作的主要内容。该项工作是以勘探地球物理为主要手段获得的岩石圈内部地球物理数据,通过人-机交互联合解释(数学正反演计算),探讨岩石圈深部的构造物理特征、热状态分布状况、动力学条件等深部地质因素与盆地的形成、发展、消亡(或被改造)之间的关系。提出盆地成因的构造地球物理模型,为进行盆地的各种地质模型定量动态模拟,求得油气远景评价提供地球物理背景。      

中国东部中小型断陷盆地陆相页岩气成藏潜力分析——以阜新盆地为例

中国东部地区发育大量的中生代中小型断陷盆地,盆地内陆相富有机质泥页岩沉积厚度大,白垩纪的火山活动加快了区内页岩中所含有机质的成熟,为页岩气成藏提供了有利的先决条件。为了分析上述断陷盆地陆相页岩气的成藏潜力,以阜新盆地为例,根据最新的钻井资料、岩心和岩屑测试数据,重点分析并评价了该区富有机质页岩厚度、展布、总有机碳含量(TOC)、烃源岩有机质热演化成熟度(Ro)、储集能力和可压性等6项成藏要素,进一步结合页岩储层的特征,研究了该区陆相页岩气的成藏潜力并提出了下一步勘探开发的建议。研究结果表明:?我国东部中小型断陷盆地陆相页岩具有储层总厚度大、TOC高和热成熟度适中等3项页岩气成藏的有利条件,以及页岩储层厚度横向变化大、储集能力偏低和可改造性偏差等3项不利条件;?陆相页岩TOC高(平均值为5.4%),在中生代火山活动的作用下有机质热演化程度较高(Ro1.2%),位于生气窗内,页岩气成藏具备优越的物质基础;?海相页岩气开发所采用的水平井多段压裂技术在陆相页岩气开发中的效果值得商榷,应积极探索陆相页岩气直井纵向多层立体开发技术;(4)较之于海相页岩气,陆相页岩气单井产量更低,故需要加强断陷盆地陆相页岩气单井经济产能评价工作。结论认为,我国东部断陷盆地多与阜新盆地类似,具备页岩气成藏的物质基础,是陆相页岩气勘探突破的新方向;下一步勘探的重点是找到高储集能力区、落实易改造层段。     

含油气盆地中膏盐岩层对油气成藏的重要影响

多数盆地的膏盐岩为蒸发成因,部分地区则为深部热卤水作用的产物.研究表明:膏盐岩的形成环境(主要是陆相湖盆蒸发环境)有利于有机质的保存,为油气生成提供物质保障.深部热卤水作用致使深部热流体上侵,将提高烃源岩的油气转化效率以及为无机油气藏的形成提供了条件.膏盐岩能使其下部地层保持较高的孔隙度并且形成次生孔裂隙(但也可堵塞下部地层原生孔隙),同时本身也可成为油气的运移通道或储集空间,是其下部异常高压系统得以形成的重要条件,有利于油气藏的保存.膏盐层可以单独封盖油气,也可与断层联合封堵,具有很好的封盖能力.膏盐层对其上、下地层的区域构造样式产生影响,也限定了油气运移的途径和聚集层位.     

沉积盆地热历史重建研究进展与挑战

系统介绍了沉积盆地热历史研究方法的现状和进展。沉积盆地热史重建方法主要包括古温标方法和地球动力学方法两大类，前者主要是从盆地的尺度来进行研究，后者则是从岩石圈的尺度来研究盆地的热历史。古温标方法主要包括了有机质成熟度指标和低温热年代学参数，由于可以通过实测数据来检验模拟结果，因而被认为是研究精度较高且切实可行的方法；实际工作中，一般采用多种古温标耦合反演热历史以提高模拟结果的精度和可靠性。针对多期构造演化盆地，可以结合多种古温标耦合反演和地球动力学正演方法进行相互补充和验证，从而实现定量恢复古老盆地复杂热历史。同时，盆地热史在研究构造抬升作用下的页岩气保存、盆山构造—热演化耦合作用等方面提供了重要的方法技术。目前，针对深层—超深层、海相层系和古老层系的热史重建仍存在诸多问题和挑战。