甾烷异构化指数定量恢复油气盆地热演化史

本利用甾烷异构化指数随时间、温度变化规律、采用热指标反演拟合法建立了非线性，反演波动热流模型，分构造运动期模拟古热流。实现了甾烷异构化指数恢复油气盆地热演化的定量化。运用上述方法，对海拉尔盆地海参１井进行了热史模拟，得到了盆地源岩热演化的一般规律。     

未熟油与成熟油的混油实验及其应用

针对潜江凹陷一些断裂带、古剥蚀区存在不同成熟度油源混合的问题，选用该凹陷广33井未熟油与广11井成熟油进行了不同比例的混油实验。依据其实验结果，利用衡量原油成熟度最有效的指标C29甾烷的两个异构化参数值，科学地判断出潭口、代河油田未熟油与成熟油的混源比例大致为1：3和1：1，取得了满意的效果。     

FAMM技术在松辽盆地源岩成熟度评价中的应用

采用FAMM技术分析松辽盆地晚白垩世青一段优质烃源岩认为镜质体具有富氢特点,镜质体反射率受到的抑制程度为0.08％ ～0.21％,平均为0.12％.与此同时,建立了实测镜质体反射率与等效镜质体反射率的关系,指出利用实测镜质体反射率评价烃源岩时可能低估了其成熟度.该技术有助于正确恢复盆地的古地温史和热史,能够有效地指导石油勘探.     

原油中甾烷的生物降解模拟实验研究

通过喜氧细菌对原油的模拟生物降解实验,以及对模拟产物的饱和烃色谱—质谱分析,对原油饱和烃中规则甾烷和重排甾烷的降解作用进行了研究。研究结果显示,规则甾烷先于重排甾烷发生生物降解,甾烷降解由易到难的顺序为C₂7>C₂8>C₂9。在甾烷被大量降解前,20S/(20S+20R)(甾烷异构化作用)等生物标记化合物的成熟度指标基本无变化,但某些用于油源对比、母源和沉积环境研究的生物标记化合物参数可能会发生变化,如:规则甾烷/17α(H)-藿烷、C₂7-C₂8-C₂9甾烷、C₂7-C₂8-C₂9重排甾烷和重排甾烷/规则甾烷等。      

东海盆地西湖凹陷烃源岩成熟度厘定——FAMM分析的证据

镜质体反射率是评价烃源岩有机质成熟度的主要指标之一,已有研究表明,镜质体反射率（R_o）除受控于有机质热演化程度外,还受烃源岩有机质类型等因素的影响,镜质体富氢程度制约镜质体反射率的抑制程度,影响了R_o测值的准确性。多组分荧光变化（FAMM）技术可有效解决镜质体反射率的抑制问题。利用FAMM技术和镜质体反射率分析方法,对取自东海盆地西湖凹陷9口钻井的10件平湖组烃源岩样品进行了成熟度分析,结果显示样品的镜质体反射率存在不同程度的抑制,抑制校正值介于0.01%~0.25%,个别样品稍有增强现象。根据FAMM分析结果,以TWT1井为例,厘定了该井区平湖组烃源岩的成熟度,认为TWT1井区平湖组烃源岩的现今成熟度应处于0.90%~1.41%,而不是实测镜质体反射率分析结果显示的0.77%~1.21%。研究结果有助于合理评价平湖组烃源岩生烃潜力及油气资源潜力。     

溱潼凹陷低熟油生物标志物特征及成熟度浅析

溱潼凹陷低熟油分布于外斜坡的殷庄油田殷2井戴南组一段和苏183井泰州组一段、坡垒带茅山油田苏168井的阜宁组三段、断阶带的角墩子油田苏228井的戴南组一段和草舍油田苏120井的三垛组一段,具有高含蜡量、低含硫量、运动粘度和密度变化大的特点。该凹陷低熟油判识指标αααC₂₉甾烷20S/(20S+20R)和C₂₉甾烷αββ/(ααα+αββ)值分别为0.31和0.29;生物标志物甾烷异构化参数αααC₂₉甾烷20S/(20S+20R)为0.23～0.29,C₂₉甾烷αββ/(ααα+αββ)为0.24～0.28,重排甾烷含量很低。同时还检测到多种不稳定的生物标志物,包括5β(H)-粪甾烷系列,胡萝卜烷系列、脱羟基维生素E系列等。而较低的伽马蜡烷/C₃₀藿烷分布指数、小于0.5%的含硫量以及四环三萜烷中C₃₀～C₃₁羊毛甾烷的检出,充分反映源岩沉积于微咸-半咸水的沉积环境和母岩成熟度较低这一事实。     

晋县凹陷下第三系沙四段至孔一段甾烷高异构化程度及未熟油形成机理探讨

通过冀中地区晋县凹陷下第三系沙四段至孔一段14口井 30块样品的色谱质谱分析 ,鉴定出 15个系列182个生物标志物。研究不同沉积环境下生物标志物的组合特征及其地质意义 ,讨论该层段盐湖相烃源岩甾烷“熟化”现象的产生及未熟油的生成 ,认为 :①水介质化学条件的变化是决定晋县凹陷中南部该层段三角洲相沉积中生物标志物组合特征多样性的重要因素 ;②该层段盐湖相未熟沉积有机质中存在的甾烷“熟化”现象 ,是由于在咸化水介质化学条件下 ,ββ 构型甾烷由甾醇经甾烯中间产物的还原作用而生成这一生成机理所引起的 ;③ββ 构型甾烷既可能具有热力学效应 ,也可能具有沉积环境的指相意义 ;④从一些生物标志物的生成机理和演化途径看 ,该凹陷未熟油可能是在咸化程度较高的水介质条件下 ,低温生物化学反应或低温化学反应的产物     

PVT分馏实验中甾、萜烷分子的行为

为了解油气成藏过程中常见的降压和气洗作用对甾、萜烷分子组成的影响，开展了PVT模拟实验。测量和对比不同分馏阶段产物的结果表明：降压和气洗作用对原油及其形成的凝析油的甾、萜烷组成的影响有所不同，但多遵循一般的蒸发分馏作用规律，其影响程度主要取决于油藏的温度、压力条件；不同的降压和气洗过程可以在甾、萜烷分子参数的变化方面表现出来，不仅某些具成因意义的Ts／Tm和重排甾烷／规则甾烷等参数会受蒸发分馏作用的影响，其它一些具地球化学应用意义的参数(如C29异胆甾烷／胆甾烷等)也不同程度地受到影响，充分说明气洗和温压分馏效应不仅反映在轻烃和低分子化合物上，而且也反映在甾、萜烷分子结构上。上述认识可用于确定油气成藏的过程，也有利于科学使用常规油气地球化学指标。图1表1参13     

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古地温史模拟是含油气盆地数值模拟的重要组成部分，其目的是重建古地温的演化过程，为油气的生成史模拟提供关键的古地温场数据，目前古地温模拟有正，反演的两种方法，本文着重论述用镜质体反射率作为古地校对指标的反演模拟方法。其思路是：古地地温按热传导的基本公式进行计算，其中关键是古热流Ｑ的恢复；据Ｌｅｒｃｈｅ等的研究，古热流Ｑ与现今Ｑ０存在函数关系，于是问题转化为对函数式中β值的估计，它可用镜质体反射率等“     

海相烃源岩镜状体反射率测定方法在塔东地区的应用

有机质成熟度是评价烃源岩和油气演化的地球化学参数之一,沉积岩中镜质体反射率的分析测定对于油气发现具有重要意义。中国下古生界海相烃源岩地层有机质丰度低,演化程度高,缺乏典型的镜质体,因而常规的海相有机地球化学演化指标不适用。应用海相烃源岩镜状体反射率分析测定方法实验,然后将测定结果换算为等效的镜质体反射率,从而标定出海相烃源岩的有机质成熟度。应用此方法对塔里木盆地满加尔地区中下奥陶统—寒武系烃源岩进行了评价,并且恢复了古城地区和塔东隆起区的烃源岩成熟史。     

MATURITY-DEPENDENT GEOCHEMICAL MARKERS OF CRUDE PETROLEUMS FROM EGYPT

ABSTRACT

Maturity-dependent trends of a number of biomarker and nonbiomarker geochemical parameters were examined in crude oils from the Western Desert and the Gulf of Suez, Egypt. Molecular maturity assessments showed that all oils are at an advanced level of thermal maturity, and many ratios, such as CPI, hopane/hopane + moretane, C₃₁ 22S/22S + 22R hopanes and C₂₉ ααα-20S/20S + 20R steranes were almost identical and have reached their thermal equilibrium values. Changes in the Ts/Tm and C₂₉ ββ/(ββ + αα) steranes however, showed a more advanced level of thermal maturity for Umbaraka oil. On the other hand, correlations utilizing the nonbiomarkers API gravity, ΣV, Ni, sulfur content, sat/arom, and Ph/n-C₁₈ ratios did show more distinct differences and are consistent between the oils.     

烃源岩热模拟实验中重排藿烷类化合物变化特征及其意义

为了探索热演化程度对烃源岩中重排藿烷类化合物形成的影响及其地球化学意义,通过对渤海湾盆地PL-1井未成熟烃源岩样品进行热模拟实验研究,分析重排藿烷类化合物组成随热模拟实验温度变化特征以及重排藿烷参数与热演化程度的关系。在烃源岩的不同热演化阶段,重排藿烷类化合物变化特征不同。烃源岩热模拟实验250℃时的重排藿烷绝对浓度相对于烃源岩原样中的重排藿烷绝对浓度略有升高;250~400℃时的重排藿烷绝对浓度均逐渐降低。在热模拟实验中重排藿烷绝对浓度降低比例呈现出高成熟阶段>成熟阶段>低成熟阶段的规律;在300~400℃对应的成熟—高成熟阶段,化合物绝对浓度降低幅度呈现出17α（H）-藿烷 >18α（H）-新藿烷 >17α（H）-重排藿烷的特征。17α（H）-重排藿烷参数在低成熟—成熟阶段基本不变,在成熟—高成熟阶段逐渐增大。未成熟—低成熟阶段是重排藿烷类化合物形成的主要阶段,较高的热演化程度对重排藿烷的形成具有一定影响,重排藿烷参数可以作为烃源岩成熟—高成熟阶段有效的成熟度指标。     

北部湾盆地迈陈凹陷徐闻X1井生烃史

镜质体反射率是确定徐闻X1井烃源岩有机质成熟度的有效指标。依据单井分层数据和有关的地质基础数据，应用Basin Mod 1D盆地模拟软件重建了徐闻1井地层剖面的埋藏一热演化史，结果表明流沙港组烃源岩底部在涠州二段沉积期末进入生烃门限，在渐新世晚期整体进入生烃门限，流沙港组烃源岩有机质目前正处于生烃演化的高峰阶段。     

深部流体对原油中生物标志化合物的影响

分析、对比了饱和烃和生物标志物在深部热流体作用下的变化特征后指出,在深部流体热能的影响下,m($\sum{n}C_{21-}$)/m($\sum{n}{C_{22}}^{+}$) .m(Pr)/m(Ph)值增高,奇偶优势明显减弱,m(C₃₁藿烷)/m(C₃₀藿烷)和m(C₃₅藿烷)m(C₃₄藿烷)变小,m(C₂₇-C₂₉甾烷20S)/m[C₂₇-C₂₉甾烷(20S+20R)]和m(C₂₇-C₂₉甾烷ββ)/m[C₂₇-C₂₉甾烷(ββ+αα)]增大,芳烃类富集。若为富氢深部热流体,m($\sum{n}C_{21-}$)/m($\sum{n}{C_{22}}^{+}$)、m(Pr )/m(Ph)、m(Ts )/m(Ts+Tm)等也会失去指示成熟度和沉积环境的能力。在此基础上,初步提出了原油或烃源岩有机质受深部热流体改造的判识标志。     

A RAPID METHOD OF QUANTIFYING THE RESOLUTION LIMITS OF HEAT-FLOW ESTIMATES IN BASIN MODELS

Deterministic forward models are commonly used to quantify the processes accompanying basin evolution. Here, we describe a workflow for the rapid calibration of palaeo heat‐flow behaviour. The method determines the heat‐flow history which best matches the observed data, such as vitrinite reflectance, which is used to indicate the thermal maturity of a sedimentary rock. A limiting factor in determining the heat‐flow history is the ability of the algorithm used in the software for the maturity calculation to resolve information inherent in the measured data. Thermal maturation is controlled by the temperature gradient in the basin over time and is therefore greatly affected by maximum burial depth. Calibration, i.e. finding the thermal history model which best fits the observed data (e.g. vitrinite reflectance), can be a time‐consuming exercise. To shorten this process, a simple pseudo‐inverse model is used to convert the complex thermal behaviour obtained from a basin simulator into more simple behaviour, using a relatively simple equation. By comparing the calculated “simple” maturation trend with the observed data points using the suggested workflow, it becomes relatively straightforward to evaluate the range within which a best‐fit model will be found. Reverse mapping from the simple model to the complex behaviour results in precise values for the heat‐flow which can then be applied to the basin model. The goodness‐of‐fit between the modelled and observed data can be represented by the Mean Squared Residual (MSR) during the calibration process. This parameter shows the mean squared difference between all measured data and the respective predicted maturities. A minimum MSR value indicates the “best fit”. Case studies are presented of two wells in the Horn Graben, Danish North Sea. In both wells calibrating the basin model using a constant heat‐flow over time is not justified, and a more complex thermal history must be considered. The pseudo‐inverse method was therefore applied iteratively to investigate more complex heat‐flow histories. Neither in the observed maturity data nor in the recorded stratigraphy was there evidence for erosion which would have influenced the present‐day thermal maturity pattern, and heat‐flow and time were therefore the only variables investigated. The aim was to determine the simplest “best‐fit” heat‐flow history which could be resolved at the maximum resolution given by the measured maturity data. The conclusion was that basin models in which the predicted maturity of sedimentary rocks is calibrated solely against observed vitrinite reflectance data cannot provide information on the timing of anomalies in the heat‐flow history. The pseudo inverse method, however, allowed the simplest heat‐flow history that best fits the observed data to be found.     

ORGANIC GEOCHEMISTRY OF OIL AND NATURAL GAS IN THE WEST DIKIRNIS AND EL‐TAMAD FIELDS,ONSHORE NILE DELTA,EGYPT: INTERPRETATION OF POTENTIAL SOURCE ROCKS

Crude oil in the West Dikirnis field in the northern onshore Nile Delta, Egypt, occurs in the poorly‐sorted Miocene sandstones of the Qawasim Formation. The geochemical composition and source of this oil is investigated in this paper. The reservoir sandstones are overlain by mudstones in the upper part of the Qawasim Formation and in the overlying Pliocene Kafr El‐Sheikh Formation. However TOC and Rock‐Eval analyses of these mudstones indicate that they have little potential to generate hydrocarbons, and mudstone extracts show little similarity in terms of biomarker compositions to the reservoired oils. The oils at West Dikirnis are interpreted to have been derived from an Upper Cretaceous – Lower Tertiary terrigenous, clay‐rich source rock, and to have migrated up along steeply‐dipping faults to the Qawasim sandstones reservoir. This interpretation is supported by the high C₂₉/C₂₇ sterane, diasterane/sterane, hopane/sterane and oleanane/C₃₀ hopane ratios in the oils. Biomarker‐based maturity indicators (Ts/Tm, moretanes/hopanes and C₃₂ homohopanes S/S+R) suggest that oil expulsion occurred before the source rock reached peak maturity. Previous studies have shown that the Upper Cretaceous – Lower Tertiary source rock is widely distributed throughout the on‐ and offshore Nile Delta. A wet gas sample from the Messinian sandstones at El‐Tamad field, located near to West Dikirnis, was analysed to determine its molecular and isotopic composition. The presence of isotopically heavy δ¹³ methane, ethane and propane indicates a thermogenic origin for the gas which was cracked directly from a humic kerogen. A preliminary burial and thermal history model suggests that wet gas window maturities in the study area occur within the Jurassic succession, and the gas at El‐Tamad may therefore be derived from a source rock of Jurassic age.     

A METHOD FOR ANALYZING GEOTHERMAL GRADIENT HISTORIES USING THE STATISTICAL ASSESSMENT OF UNCERTAINTIES IN MATURITY MODELS

A major factor contributing to uncertainty in basin modelling is the determination of the parameters necessary to reconstruct the basin's thermal history. Thermal maturity modelling is widely used in basin modelling for assessing the exploration risk. Of the available models, the chemical kinetic model Easy%Ro has gained wide acceptance.
In this study, the thermal gradient at five wells in the Danish North Sea is calibrated against vitrinite reflectance using the Easy%Ro model coupled with an inverse scheme in order to perform sensitivity analysis and to assess the uncertainty. The mean squared residual (MSR) is used as a quantitative measure of mismatch between the modelled and measured reflectance values. A 90% confidence interval is constructed for the determined mean of the squared residuals to assess the uncertainty for the given level of confidence. The sensitivity of the Easy%Ro model to variations in the thermal gradient is investigated using the uncertainty associated with scatter in the calibration data. The best thermal gradient (minimum MSR) is obtained from the MSR curve for each well. The aim is to show how the reconstruction of the thermal gradient is related to the control data and the applied model.
The applied method helps not only to determine the average thermal gradient history of a basin, but also helps to investigate the quality of the calibration data and provides a quick assessment of the uncertainty and sensitivity of any parameter in a forward deterministic model.     

PETROLEUM GEOCHEMISTRY OF LATE CRETACEOUS AND EARLY TERTIARY SHALES PENETRATED BY THE AKUKWA-2 WELL IN THE ANAMBRA BASIN,SOUTHERN NIGERIA†

The concentration, type and thermal maturity of organic matter from the Imo Shale, Nkporo Shale and the upper parts of the Nkalagu Formation which were penetrated by the Akukwa-2 well are presented. The organic carbon content ranged from 0.4–3.5%. The kerogens from the various formations were of the humic and mixed varieties. Evidence from independent thermal maturity parameters (namely, average vitrinite reflectance (R₀%), T_max and transformation ratio from Rock-Eval, n-alkanes distribution pattern, and hopane “fingerprint”) combined to locate the top of the ‘oil window’ within the Nkporo Shale at a depth of approximately 2,000 m from the surface. This corresponds to a threshold temperature of circa 65°C. Sedimentary organic matter which is favourable for both gas and oil generation is therefore probably abundant in the Anambra basin. Hydrocarbon reservoirs are possibly located at relatively shallow depths where accumulations of heavy oils may also be expected.     

GEOCHEMICAL CHARACTERISTICS OF CRUDE OILS FROM THE SHARARA-C OIL FIELD,MURZUQ BASIN,SOUTHWESTERN LIBYA

Crude oil samples from the Sharara-C oil field (Concession NC-115, Murzuq Basin, SW Libya) were analysed by organic geochemical methods in order to infer the geochemical characteristics of their respective source rocks. Aromatic hydrocarbons were analysed by gas chromatography – mass spectrometry (GC-MS), and gas chromatography – tandem mass spectrometry (GC-MS-MS) was used to analyse saturated biomarkers. The Sharara-C oils are interpreted to have been generated by marine shales containing mixed terrigenous and marine organic materials deposited in an intermediate (suboxic) environment. Age-specific biomarker ratios indicated that the oils are older than Cretaceous, and maturation-related parameters pointed to their high thermal maturity. Consistent with previous studies, source rocks are inferred to be “hot” shales in the Lower Silurian Tanezzuft Formation. Almost all the parameter ratios calculated varied over a very narrow range, indicating that the investigated oils were compositionally similar. The only significant difference that was noted concerned the sterane/hopane ratios whose variation suggested that there was some variability in the composition of the source organic material. The organic geochemical parameters determined for the Sharara-C crude oils were compared with published data on other crude oils from Concession NC-115. Almost all the parameters agreed well with previously published data on oils from this part of the Murzuq Basin. The greatest deviation concerned the values of some of the maturity parameters. This tended to confirm the conclusions of previous studies concerning the presence of a number of distinct oil families and sub-families in the Sharara oil field area which are genetically related but which have different maturities.     

生物标志化合物热成熟度参数演化规律及意义——以Ⅲ型烃源岩HTHP生排烃热模拟液态烃产物为例

为了探究烃源岩不同热演化阶段生物标志化合物成熟度参数的演化规律及其专属指示意义。通过对辽河盆地桃10井Ⅲ型烃源岩进行HTHP生排烃热模拟实验,获取的液态烃产物饱和烃组分进行GC/MS分析,以模拟温度为成熟度标尺,检测出正构烷烃、类异戊二烯类烷烃、三环二萜烷、藿烷及甾烷系列中对热成熟度演化具有一定指示意义的生物标志化合物,并计算出参数指标。依据不同生物标志化合物对热作用的敏感程度不同,利用不同热敏感性的生标化合物比值指示热演化阶段。结果发现,随着模拟温度的升高,藿烷会受热作用影响形成三环萜烷,Tm会转化为Ts,20R型生物型异构体会向20S型地质异构体转化,所以∑三环萜烷／∑藿烷、Ts/Tm和C₃₁-藿烷22S／（22S+22R）参数对有机质热演化阶段可以起到较好的指示作用。而受热作用的差异性影响,参数C₂₄-四环萜烷／∑藿烷、C₃₀βα-莫烷／C₃₀αβ-藿烷和C₂₉-甾烷ββ／（αα+ββ）则在成熟至过成熟阶段具有更强的指示意义。由此可见,样品不同热演化阶段均有其最佳适用的生标参数组合,这为正确利用成熟度参数判识该地区烃源岩成熟度演化阶段提供了一定的理论依据。