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陈勇
, 赵孟军
CHEN Yong, ZHAO Mengjun
中图分类号: P571
文献标识码: A
文章编号: 1006-7167(2017)05-0014-03
收稿日期: 2016-09-8
网络出版日期: 2017-05-20
版权声明: 2017 《实验室研究与探索》编辑部 《实验室研究与探索》编辑部 所有
基金资助:
作者简介:
作者简介:陈 勇(1976-),男,四川安岳人,博士,副教授,主要从事流体包裹体形成机制与分析方法方面研究。Tel.:0532-86981878; E-mail:yongchenzy@upc.edu.cn
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摘要
光谱分析技术在烃类包裹体分析中得到了广泛应用,但是不少研究结果表明单光谱技术在分析时存在局限性。针对该问题提出了采用荧光光谱、拉曼光谱和红外光谱技术联合分析储层烃类包裹体方法,该方法可以弥补单光谱分析技术的不足。通过对准噶尔盆地南缘霍-玛-吐构造带储层中烃类包裹体进行多光谱技术联合分析和应用,结果表明,多光谱技术可以实现互补,有利于给出更加可靠的油气成熟度信息。
关键词：
Abstract
Spectroscopic technology is widely used for analysis of hydrocarbon inclusions, but previous studies showed some limits of single spectroscopic method. We proposed multi-spectroscopic technology to analyze hydrocarbon inclusions in reservoirs, which combines with fluorescence spectrum, Raman spectrum, and infra-red spectrum. This method can make up shortage of single spectrum technology. This paper reported that multi-spectrum was used to study the maturity of oil in hydrocarbon inclusions from reservoir of Huo-Ma-Tu structure belt in southern Zhungaer basin. The results indicate that multi-spectrum can not only be a complementation for single spectrum, but also give more reliable information about maturity of oil in hydrocarbon inclusions.
Keywords：
烃类包裹体直接记录了油气活动有关的信息,因而在油气成藏研究中广泛应用[1-2]。光谱分析技术是烃类包裹体分析的一种常用方法,涉及荧光光谱、红外光谱和拉曼光谱等技术。荧光光谱技术在烃类包裹体研究中最常用,通常利用荧光颜色来大致判断油气成熟度,该方法简单便捷,但越来越多的研究表明该方法存在一些不确定性,如Liu等[3-4]曾指出荧光光谱判断油气成熟度时应当小心。显微红光谱技术也常用于油气包裹体分析,可以获得烃类分子的某些结构信息,但是该技术对烃类包裹体的尺寸要求较高,只有少数包裹体可以满足分析要求,往往由于缺乏标样而难以进行定量分析。拉曼光谱技术可以实现对较小的包裹体分析,但由于烃类包裹体往往具有很强荧光信号干扰,一般难以获得烃类的拉曼信息。尽管每种光谱分析技术都存在一定不足,但是3种技术联合使用可以在一定程度上达到互补的目的。本文以准噶尔盆地南缘(简称准南)霍-玛-吐构造带储层岩中的烃类包裹体为例,表明多种光谱技术联合有利于准确判定烃类包裹体中油气的成熟度。
正确区分油气成藏期次和各期油气的成熟度是油气成藏研究中的重要内容之一。准南霍-玛-吐构造带位于准噶尔盆地南缘,属于叠加型前陆盆地,前勘探显示良好的油气前景。紫泥泉子组为该区最重要的储层,岩性主要为细砂岩和粉砂岩,分选中等—较差,杂基含量较高。通过显微镜下仔细观察,表明储层中既发育有盐水包裹体又发育烃类包裹体,多数包裹体分布在石英和长石的微裂隙、加大边以及碳酸盐胶结物中,其中石英微裂隙中分布最多。次生盐水包裹体多沿裂隙或成群分布于石英和长石颗粒中,或在胶结物中以单个分布为主;烃类包裹体主要有气液两相包裹体和纯液相的单相包裹体两种类型,呈群体或单个分布。次生盐水包裹体个体总体较小,多在4~20 μm,形状以近椭圆和近圆形为主,不规则状包裹体也很常见,颜色透明,气液比在1%~5%;烃类包裹体较盐水包裹体大一些,多在8~40 μm,形状多为不规则,液相多为无色和淡褐色,气泡呈浅褐至深褐色,气液比变化较大,在3%~40%,主要集中在5%~15%。
对样品进行了岩相学和显微荧光观察,结合成岩序列,可以初步识别出两期烃类包裹体:第一期烃类包裹体主要分布矿物颗粒内部早期愈合的微裂隙和次生加大边中,透射光下呈褐色、浅褐色,室温下主要以纯液相及气液两相包裹体形式存在(见图1(g)、(i)、(k));第二期烃类包裹体主要分布在晚期硅质胶结物和亮晶方解石胶结物中,少量分布在穿过石英和长石颗粒边界的裂隙中,透射光下呈浅褐色-无色透明,室温下以纯气相及气液两相包裹体形式为主(见图1(a)、(c)、(e))。
荧光的颜色和强度与包裹体中有机组成的分子结构类型有密切关系。一般而言,纯饱和烃不发荧光,而含C=C共轭双键的不饱和烃类分子易发荧光。研究表明,随着油气演化程度(成熟度)的升高,油气包裹体的荧光颜色会呈现明显的递变规律[4-5],而且发出的荧光还可以反映液相烃类的密度,Goldstein等[6]指出低密度的液相油气的荧光波长较短,一般呈蓝光;而随着油气密度增大,其荧光波长增大,颜色转变为呈橘色和红色。由此可见,利用荧光显微镜观察烃类包裹体的荧光颜色与明暗程度,有助于鉴别不同期次油气演化阶段与成熟度[4]。目前还可以利用荧光光度计对荧光波长和强度进行定量分析。
为了解不同期次油气的成熟度,对样品中两期烃类包裹体在荧光显微镜下进行了紫外荧光分析,结果显示:第一期烃类包裹体主要发黄绿色荧光,如图1(h)、(j)、(l),反映了该期低成熟—成熟油充注;第二期烃类包裹体主要发蓝色—蓝白色荧光,如图1(b)、(d)、(f),反映了该期为高成熟油气充注。但是,仔细观察可以看到,第一期的烃类包裹体周围基本都发蓝色荧光,受第二期的油气干扰较大,稍不注意就会出现误判。为进一步确定油气成熟度,我们对部分烃类包裹体进行了显微红外光谱和拉曼光谱分析。
显微红外光谱可以获得包裹体中的简单分子机分子和大有机分子官能团的红外吸收特征,从而确定有机物的组成或结构特征,根据有机分子结构特征可以判断油气分子的大小和结构特征,进而推测油气成熟度。研究中通常利用烃类包裹体中有机物或基团的特征吸收峰特征比值来判断烃类包裹体中所含有机物的结构性质及演化过程和程度[7]。显微傅里叶变换红外光谱采用了近红外激光,可以消除因有机分子产生的荧光,且矿物基体的影响也较弱,成为无损鉴定有机包裹体的一种有效手段[8-10]。但显微红外光谱分析一般要求烃类包裹体大于15 μm,如果包裹体太小,很难获得有效信息。通过对红外光谱图分析,可计算CH2/CH3比值及CH4、CO2、烷烃的摩尔百分含量[8-9],一般认为,CH2/CH3比值越小,包裹体中有机质的成熟度越高[8-9]。甲烷含量可以由Pironon 等 [11]给出的公式来计算,但是由于缺少标样,国内很多实验室都无法实现。
为进一步确定烃类包裹体中油气的成熟度,对研究样品进行显微红外光谱分析,实验分析在中国石油勘探开发研究院石油地质实验中心完成,所用仪器为Nicolet 6700红外光谱仪,测试条件为:32倍镜头,NaCl窗片,透射光,检测范围4 000~4 00 cm-1。结果显示,霍-玛-吐构造带储层两期烃类包裹体的成熟度明显不同,如图2所示。第一期烃类包裹体中的油气成熟度较低,如图2(a)、(b)、(c)代表的储层烃类包裹体CH2/CH3分别是2.64、1.86、1.98;第二期烃类包裹体中的油气成熟度较高,如图2(d)、(e)、(f)代表的储层烃类包裹体CH2/CH3分别是1.07、0.92、1.3。从包裹体红外光谱分析特征可以看出,霍-玛-吐构造带确实存在2期不同成熟度的油气充注,证实了存在两期油气成藏过程和油气性质的差异性。
尽管对于大部分烃类包裹体来说,在拉曼测试时往往会因为发出荧光而难以获得拉曼信号,但对于一些不发荧光,在荧光显微镜下很难与盐水包裹体区分的气态烃包裹体,用拉曼分析具有优势。为了探讨石油组分中各类有机化合物的激光拉曼峰特征,张鼐等[12-13]曾测定了石油组分中正构烷烃、异构烷烃、环烷烃、芳烃、非烃和沥青质的激光拉曼光谱,并以此为依据对烃包裹体进行了分类。本次研究对研究区储层含烃流体包裹体进行了激光拉曼光谱分析,仪器为LabRam010,514.5 nm激光,共焦孔1 mm,狭缝400 μm,实验分析在中国石油大学地球科学与技术学院流体包裹体实验室完成。结果显示,两期油气包裹体的拉曼信号具有明显的差异,第一期烃类包裹体中的油气以饱和烃为主,未见芳烃的拉曼信号(图3(a)所示);而第二期烃类包裹体中的油气既含饱和烃又含有芳烃,芳烃的拉曼信号非常明显(图3(b)所示),结合烃源岩演化和油源对比,芳烃可能来自侏罗系煤系地层生烃产生的[14]。由于油气演化程度越高,碳含量也越高,烃分子会有脱氢聚碳的趋势,结果会导致芳烃含量升高。Matthias研究报道[15]芳烃可以作为油气成熟度指标。所以第二期油气出现芳烃结构,这也暗示油气成熟度变高。这与前面的显微红外分析结果是一致的,印证了两期油气成熟度的差异。由此可见,只要获得烃类包裹体的拉曼光谱信号,就可以得到组分的重要信息,可基于分子结构对油气差异进行判断。
荧光光谱分析是烃类包裹体成熟度判断最常用的技术,但是存在不确定性。结合显微红外光谱和拉曼光谱分析可以获得基于分子结构的信息,这有助于准确判断包裹体中油气成熟度。本文通过对霍-玛-吐构造带紫泥泉子组储层流体包裹体镜下观察、荧光、显微红外和拉曼光谱分析,判断本区存在两期不同成熟度的烃类包裹体,证实了两期油气成藏过程。第一期烃类包裹体发黄绿色荧光为主,CH2/CH3比值较低,主要含有饱和烃,油气成熟度较低;第二期烃类包裹体发蓝白色荧光,CH2/CH3比值较高,明显含有芳香烃,成熟度较高。通过实例研究证实,多光谱技术联合使用有助于排除单光谱技术的局限性,可以获得更多的有效信息,更加准确的判断油气成熟度,在以后的研究中应当重视。
The authors have declared that no competing interests exist.
| [1] |
|
| [2] |
油气和含油气包裹体及其在油气地质地球化学研究中的意义 [J].
本文在综合前人研究的基础上，结合笔者的工作经验，提出了一个实用的油气和含油气包裹体分类方案，详细论述了各类油气和含油气包裹体的相态、组成和均一温度特征。在同一油气藏，均一温度越高，油相包裹体中的气态烃和挥发份的含量也越高。依据油相包裹体的均一温度的变化及其与同生水溶液包裹体的均一温度的关系可以研究油气藏在充填过程中油气组成，特别是气态烃和挥发份含量的演变。进而可以研究油气藏的油源——生油岩的类型和热演化程度。本文评述了依据油相包裹体和同生水溶液包裹体ＰＶＴ相图推断其捕获温度和压力范围的有效性和局限性。最后讨论了各类油气和含油气包裹体的成因机制及其在油气地质和地球化学研究中的意义。
|
| [3] |
Cautions in the interpretation of petroleum fluid inclusion data in petroleum system analysis: Insight from spectroscopic analyses of natural and synthetic inclusions [J].DOI:10.1016/j.gexplo.2008.11.058 URL [本文引用: 1] 摘要
cautions in the interpretation of petroleum fluid inclusion data in petroleum system analysis: insight from spectroscopic analyses of natural and synthetic inclusions
|
| [4] |
油包裹体荧光颜色及其成熟度关系 [J].DOI:10.3321/j.issn:1000-2383.2008.01.012 URL [本文引用: 3] 摘要
近年来有机包裹体在石油地质领域中的广泛应用,为油气勘探与评价注入了新的活力.有机包裹体特别是油包裹体的荧光颜色是鉴定有机包裹体和指示油气成熟度的有效手段.本文在论述有机包裹体荧光机理的基础上,依据不同盆地样品的实验观测结果,从油包裹体荧光的强度、波长、颜色以及与有机包裹体同期的盐水包裹体的均一温度等关系进行分析,证明可以运用油包裹体荧光颜色和平均均一温度等综合指示油气的成熟度.
|
| [5] |
Assessing the maturity of oil trapped in fluid inclusions using molecular geochemistry data and visually-determined fluorescence colours [J].DOI:10.1016/S0883-2927(00)00051-2 URL [本文引用: 1] 摘要
The thermal maturity of oils extracted from inclusions and the fluorescence colours of oil-bearing fluid inclusions have been measured in 36 sandstone samples from Australasian oil fields. The inclusion oils were analysed using an off-line crushing technique followed by GC–MS. A maturity assessment was made for each inclusion oil using 25 molecular maturity ratios, including a newly defined dimethyldibenzothiophene ratio (DMDR). Each inclusion oil was placed in one of 4 maturity brackets, approximately equivalent to early, mid, peak and post oil generation windows. The fluorescence colours of oil inclusions were visually-discriminated into “blue”, “white” and “yellow plus orange” and their proportions estimated using point counting techniques. Sixteen samples have >85% of oil inclusions with blue fluorescence, whilst other samples have more variable fluorescence colours. One sample has 100% of oil inclusions with yellow plus orange fluorescence. The results show that samples containing mainly blue-fluorescing oil inclusions have thermal maturities anywhere within the oil window. In particular, the molecular geochemical data strongly suggests that oil inclusions with blue fluorescence can have relatively low maturities (calculated reflectance <0.65%), contrary to the widely applied assumption that blue fluorescence colours indicate high maturities. Samples containing mainly white-fluorescing oil inclusions have maturities anywhere within the oil window and cannot be distinguished using molecular geochemical parameters from samples containing mainly blue-fluorescing oil inclusions. Though few in number, samples with mainly yellow and orange-fluorescing oil inclusions tend to have maturities in the lower half of the oil window. The data presented strongly suggest that although the relationship between API gravity and the fluorescence properties of crude oils is well established, the extension of this relationship to the use of the fluorescence colours of oil inclusions as a qualitative thermal maturity guide is not justified. Fluorescence colour depends in the first instance on chemical composition, which is controlled not only by maturity but by several other processes. For example, inclusions in samples from below current or residual oil zones in the Timor Sea contain a high proportion of yellow- and orange-fluorescing oil inclusions compared to the overlying oil zones, which are dominated by blue-fluorescing oil inclusions. This observation is interpreted to be due to water washing causing molecular and gross fractionation of oils prior to trapping. Fractionation of the gross composition of oil during the inclusion trapping process may also be a significant controlling process on the fluorescence colours of oil inclusions, due to the preferential adsorption of polar compounds onto charged mineral surfaces. A trapping control is strongly supported by synthetic oil inclusion work. Care should be taken when interpreting the charge history of samples containing oil inclusions with mixed fluorescence colour populations, such as those from the Iagifu-7x well in the Papuan Basin. It is possible that the different colour populations represent a single oil charge, with oil inclusions trapped under slightly different conditions or at slightly different grain surfaces, rather than multiple migration events.
|
| [6] |
Systematics of fluid inclusions in diagenetic minerals [J].DOI:10.2110/scn.94.31 URL [本文引用: 1] 摘要
The past decade has revealed significant advantages to using fluid inclusions as a means of understanding the physical and chemical history of fluids in sedimentary basins, but it also has revealed important limitations which have required that a new approach must be employed to effectively use fluid inclusions. This book is divided into six sections: (1) what fluid inclusions are and what geologic history they are capable of recording; (2) basic phase equilibria that must be known to understand the behavior of pore fluids and fluid inclusions in nature; (3) the question of validity of using fluid inclusions as records of ancient diagenetic systems is dealt with in such a way that the questions commonly asked about the limitations of the technique are addressed; (4) hot to conduct a fluid inclusion study, a new petrographically based approach for conducting fluid inclusion research that is followed by methods that allow for the interpretation of compositions of pore fluids that existed in sedimentary rocks, and methods of geothermometry and geobarometry; (5) selected case histories that are designed specifically to give practice in evaluating fluid inclusion data from the diagenetic realm; and (6) a summary of the arsenal of analytical techniques that may be applied to fluid inclusions to develop additional constraints on fluid inclusion composition.
|
| [7] |
Application of Micro-FT-IR Spectroscopy to Individual Hydrocarbon Fluid Inclusion Analysis [J].DOI:10.1016/0009-2541(88)90722-X URL [本文引用: 1] 摘要
Infrared spectra of fluid inclusions are obtained with a Fourier transform infrared miscrospectrometer. The experimental conditions and the analytical use are discussed. Interferograms are recorded in the transmission mode. The quality of spectra is good for fluid inclusions with diameters larger than 30 μm, the spectral resolution being 4 cm611 and the recording time 200 s. Interferograms made of inclusions with diameters of less than 20 μm are reached in the same amount of time, but with worse spectral resolution. Infrared spectra are usually only suitable above 2000 cm611, because of the absorption of most of the inclusion-bearing host minerals, the thickness of which should never exceed 1 mm. This fact further limits their interpretation, as the inclusion composition is complex. However, complementary information can be obtained in the 4600-4000-cm611 range for hydrocarbon inclusions with a thickness that is larger than some tens of micrometers. This shows that it is necessary to use a detector which is as sensitive as possible towards high frequencies. A comparison of the current performances of infrared and Raman spectroscopies as analytical methods for investigating fluid inclusions is presented. The important improvement of better spatial resolution and the corresponding possibility of being able to characterize heterogeneities, in comparison to limitations with classical dispersive infrared spectrometry, are discussed. Methane, carbon dioxide, liquid water, aromatic ester, and linear or branched alkanes are identified in several samples. It is also possible to estimate the mean ratio of alkane CH2/CH3 groups. In some cases, the intensity of the absorptions indicates the inclusion effective thickness and the mole fraction ratio.
|
| [8] |
有机包裹体显微傅立叶红外光谱和荧光光谱测定及其意义 [J]. |
| [9] |
油气包裹体的显微红外光谱测试技术及应用矿物岩石 [J]. |
| [10] |
傅立叶变换红外光谱分析矿物有机包裹体的限制-基体吸收问题初探 [J].DOI:10.3321/j.issn:1000-2383.1998.03.006 URL [本文引用: 1] 摘要
应用显微傅立叶变换红外光谱（μＦＴＩＲ）分析矿物有机包裹体时存在一个令人关注的问题，即主矿物基体吸收．分析了基体吸收存在的原因，列举了石英和碳酸钙的基体吸收范围，介绍了基体吸收消除的方法和意义，指出可以利用石英基体吸收区的１７５０ｃｍ－１附近吸收谱带指认有机化合物的羰基．
|
| [11] |
FT-IR measurements of petroleum fluid inclusions:methane,n-alkanes,and carbon dioxide quantitative analysis [J].DOI:10.1046/j.1468-8123.2001.11002.x URL [本文引用: 1] 摘要
Abstract A recent advancement in petroleum geochemistry is to model fossil oil composition using microthermometric and volumetric data acquired from individual fluid inclusion analysis. Fourier transform infrared (FT-IR) microspectroscopy can record compositional information related to gas (CH 4 and CO 2 ) and alkane contents of petroleum inclusions. In this study, a quantitative procedure for FT-IR microspectrometry has been developed to obtain, from individual fluid inclusions, mol percentage concentrations of methane, alkanes and carbon dioxide as constraints to thermodynamic modelling. A petroleum inclusion in a sample from the Qu bec City Promontory nappe area was used as standard to record a reference spectrum of methane. The analytical procedure is based on the measurement of CH 4 /alkane and CH 4 /CO 2 band area ratios. CH 4 /alkane infrared band area ratio is obtained after spectral subtraction of the reference methane spectrum. This area ratio, affected by absolute absorption intensities of methane, methyl and methylene, provides a molar CH 4 /alkane ratio. Methyl/methylene ratio (CH 2 /CH 3 ) ratio is obtained following procedures established in previous work. CO 2 /CH 4 concentration ratio is estimated from relative absolute absorption intensities. Application to natural inclusions from different environments shows good correlation between FT-IR quantification and PIT (petroleum inclusion thermodynamic) modelling.
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| [12] |
石油中饱合烃类的喇曼特征 [J].DOI:10.3969/j.issn.1007-2802.2006.01.005 URL Magsci [本文引用: 1] 摘要
本文试通过一些饱合烃类标样的喇曼分析，总结出石油中饱和烷烃组分的最大喇曼特征是在2700～2970cm^-1区域有一系列强烈的喇曼效应，有三种情况：1）直链烷烃类是以-CH^3链基对称喇曼效应（约2872cm^-1）最强；2）带异构骨架链烷烃类是以-CH链基喇曼效应（约2911cm^-1）最强；3）环烷烃类是以-CH2链基对称喇曼效应（约2857cm^-1）最强。另外异构骨架在748cm^-1处有一强的喇曼效应，烷烃环基在804cm。处有一个强的喇曼效应。并发现不同的烃或烃混合物，若结构基团相同，喇曼谱图也相同；在混合烃组分（或烃类包裹体）的喇曼谱图中2905～2921cm^-1间喇曼峰应是-CH基团，而不能单作甲烷存在的证据。
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| [13] |
烃和烃类包裹体的拉曼特征 [J].DOI:10.3321/j.issn:1006-9267.2007.07.005 URL [本文引用: 1] 摘要
通过大量烃标样拉曼分析发现：饱和烃以甲基、亚甲基在2700-2970cm^-1区域有强烈的拉曼谱峰为特征;异构骨架在748cm^-1处有一强的拉曼效应;环六环在804cm^-1处有一个强的拉曼效应;苯环有二个拉曼特征峰（988,3058cm^-1±）,以988cm^-1±为主;己烯在1294,1635和2996cm^-1±有三个烯键（C=C）拉曼特征峰,以1635cm^-1±为主.论证了：（1）烃类的拉曼图与烃类的含碳个数无关,只与烃类分子结构和基团特征有关;（2）相同的烃类如正构烷烃类的拉曼光谱图相同;（3）不能简单地由烃类的特征峰来判断烃种类（如CH4,C2H6和C3H8）和某烃相对含量,尤其在混合烃类或烃类包裹体中.对比石油四大组分总的拉曼光谱图特征,将烃类包裹体的拉曼光谱图分成五种：饱和烃型拉曼光谱图、烷烃＋沥青型拉曼光谱图、沥青型拉曼光谱图、荧光型拉曼光谱图、甲烷型拉曼光谱图.据烃类包裹体的拉曼光谱图特征将烃类包裹体分成五大种类：高饱和烃（气或液）烃类包裹体、含沥青饱和烃（气或液）烃类包裹体、低饱和烃（气或液）烃类包裹体、沥青质（气或液）烃类包裹体、高甲烷盐水包裹体.
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| [14] |
准噶尔盆地南缘白垩系原油成藏特征 [J].DOI:10.3321/j.issn:0371-5736.2008.03.013 URL [本文引用: 1] 摘要
准噶尔盆地南缘地区的油气勘探与石油地质研究长期以来以二叠系和侏罗系含油气系统为主。本文在前人工作基础之上,从烃源岩、油源和油气运聚三方面,首次比较系统地剖析了本区的白垩系原油成藏特征。研究结果表明,白垩系烃源岩的生烃和油气聚集中心位于玛纳斯—呼图壁一带,烃源层系最大厚度可超过250m,有机质类型以Ⅰ—Ⅱ1型为主,在古近纪末进入成熟排烃阶段,是本区不可忽视的一套重要烃源岩。白垩系原油纵向上主要聚集于古近系安集海河组到白垩系吐谷鲁群储层流体系统,可能存在三期油气运聚,第一期在早更新世晚期,以流体系统内部的白垩系原油运聚成藏为主,第二期是在中更新世晚期至晚更新世早期,白垩系原油,以及成熟度相对较低的古近系原油在此流体系统内部发生混合,第三期在晚更新世末期,以油气(并以侏罗系天然气为主)在垂向上沿断层的调整为特征,最终形成了复杂的多源、多层系油气分布态势。综合认为,需要充分重视白垩系原油在本区的勘探和研究。
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| [15] |
Application of aromatic compounds as maturity indicators in source rocks and crude oils [J].DOI:10.1016/0264-8172(88)90003-7 URL [本文引用: 1] 摘要
Concentration ratios of aromatic compounds, such as naphthalenes, phenanthrenes, and dibenzothiophenes are at present attracting increasing attention as maturity indicators in sedimentary rocks and crude oils. Generally, these indicators rely either on an increase with maturity in the degree of alkylation of a given parent compound or a shift in the isomer distribution of alkyl-aromatic homologues towards thermally more stable isomers. A combination of both concepts in the Methylphenanthrene Index (MPI) resulted in an excellent maturity parameter, as demonstrated for rock extracts by an improved correlation with mean vitrinite reflectance ( R m) between 0.65 and 1.4%, i.e., in the zone of oil formation. In cases that R m measurements were ambiguous, this empirical relationship has proved useful in the calculation of theoretical vitrinite reflectance ( R c) values from the MPI. On the other hand, for potential petroleum source rocks reaching maturity at relatively low temperatures, the influence of the organic matter type on the aromatic distributions cannot be neglected. Consequently, organic facies effects should be taken into account in the interpretation of aromatic distributions of such source rocks and related crude oils. Since the impact of the organic facies is strongly reduced with increasing maturity, aromatic maturity parameters are particularly useful in the maturity evaluation of post-mature crude oils and condensates. In contrast to biological markers, substantially higher concentrations of the key alkyl-aromatics persist at elevated maturation levels. Thus, aromatic maturity parameters should be considered as versatile tools in organic maturation studies, and can complement established maturity indicators based on steranes and terpanes.
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