A deep insight into the structural characteristics of Yilan oil shale kerogen through selective oxidation

The structural characteristics of oil shale are important to its application.In this work,a deep insight into the structural characteristics of Yilan oil shale kerogen(YLK)was studied using alkali-oxygen oxidation at different times and ruthenium ion catalyzed oxidation(RICO).The results indicate that YLK is gradually converted to humic acids(HAs),water-soluble acids(WSAs),carboxylic acids(CAs),CO_(2)and H_(2)O.^(13)C NMR analyses of YLK,residues and HAs indicate that C-O bonds,especially C_(ar)-O bonds of YLK,are easily cleaved.The condensed aromatic rings and long alkyl chains are difficult to be oxidized during the oxidation process.With increasing oxidation time,the molar fraction of aromatic bridgehead carbon(Xb)of YLK and the residues increases from 0.174 to 0.201,and that of HAs increases from 0.225 to 0.267.The result indicates that the aromatic structures of YLK are composed of 1-ring aromatic clusters(26.5%),2-ring aromatic clusters(67.1%)and 3 or more-ring aromatic clusters(6.4%).Also,the average methylene chain(Cn)of YLK and the residues increases from 2.0 to 5.1,and that of HAs increases from 1.3 to 2.7,indicating that the alkyl chain length is not average but has a distribution.2.5%methylene carbons exist as long n-alkyl chains in the alkyl side chains groups(SCGs)on the aromatic rings in YLK.The carbon number of SCGs ranges from 5 to 22,and C_(15)and C_(17)are predominant.3.8%methylene carbons exist as alkyl bridges linkages(BLs)connecting aromatic rings in YLK.The carbon number of BLs connecting aromatic rings ranges from 6 to 19,and C_(8)is predominant.Because of the existence of above long n-alkyl chains,93.7%methylene carbons in YLK exist as alkyl chains with an average length of 1.84.

Effects of acid treatments on Moroccan Tarfaya oil shale and pyrolysis of oil shale and their kerogen

In this study,the kerogen of oil shale from Moroccan Tarfaya deposits was isolated and the changes in the initial organic matter during the removal of the mineral matrix were examined.Chloroform extraction of the oil shale increases the intensity of the peaks in the X-ray diffractograms.Infrared spectra and X-ray diffractograms reveal the presence of mineral,calcite,quartz,kaolinite,and pyrite in the mineral matrix of the oil shale.Hydrochloric and hydrofluoric acids dissolution do not alter the organic matter.The nonisothermal weight loss measurements indicate that thermal decomposition of the isolated kerogen can be described by first-order reaction.A single kinetic expression is valid over the temperature range of kerogen pyrolysis between 433K and 873K.Furthermore,the results indicate that the removal of mineral matter causes a decrease in the activation energies of the pyrolysis reactions of oil shale.

Distribution and geochemical significance of trace elements in shale rocks and their residual kerogens

There is a dearth of information about the distribution of trace elements in kerogen from shale rocks despite several reports on trace element composition in many shale samples. In this study, trace elements in shale rocks and their residual kerogens were determined by inductively coupled plasma–mass spectrometry. The results from this study show redox-sensitive elements relatively concentrated in the kerogens as compared to the shales. This may be primarily due to the adsorption and complexation ability of kerogen, which enables enrichment in Ni, Co, Cu, and Zn. For the rare earth elements(REEs),distinct distribution characteristics were observed for shales dominated by terrigenous minerals and their kerogen counterparts. However, shales with less input of terrigenous minerals showed similar REE distribution patterns to their residual kerogen. It is speculated that the distribution patterns of the REEs in shales and kerogens may be sourcerelated.

Molecular Structure of Kerogen in the Longmaxi Shale: Insights from Solid State NMR, FT-IR, XRD and HRTEM

Kerogen plays an important role in shale gas adsorption,desorption and diffusion.Therefore,it is necessary to characterize the molecular structure of kerogen.In this study,four kerogen samples were isolated from the organic-rich shale of the Longmaxi Formation.Raman spectroscopy was used to determine the maturity of these kerogen samples.Highresolution transmission electron microscopy(HRTEM),13 C nuclear magnetic resonance(13 C NMR),X-ray diffraction(XRD)and Fourier transform infrared(FT-IR)spectroscopy were conducted to characterize the molecular structure of the shale samples.The results demonstrate that VReqv of these kerogen samples vary from 2.3%to 2.8%,suggesting that all the kerogen samples are in the dry gas window.The macromolecular carbon skeleton of the Longmaxi Formation kerogen is mainly aromatic(fa’=0.56).In addition,the aromatic structural units are mainly composed of naphthalene(23%),anthracene(23%)and phenanthrene(29%).However,the aliphatic structure of the kerogen macromolecules is relatively low(fal*+falH=0.08),which is presumed to be distributed in the form of methyl and short aliphatic chains at the edge of the aromatic units.The oxygen-containing functional groups in the macromolecules are mainly present in the form of carbonyl groups(fac=0.23)and hydroxyl groups or ether groups(falO=0.13).The crystallite structural parameters of kerogen,including the stacking height(Lc=22.84?),average lateral size(La=29.29?)and interlayer spacing(d002=3.43?),are close to the aromatic structural parameters of anthracite or overmature kerogen.High-resolution transmission electron microscopy reveals that the aromatic structure is well oriented,and more than 65%of the diffractive aromatic layers are concentrated in the main direction.Due to the continuous deep burial,the longer aliphatic chains and oxygen-containing functional groups in the kerogen are substantially depleted.However,the ductility and stacking degree of the aromatic structure increases during thermal evolution.This study provides quantitative information on the molecular structure of kerogen samples based on multiple research methods,which may contribute to an improved understanding of the organic pores in black shale.

Type Ⅰ kerogen-rich oil shale from the Democratic Republic of the Congo: mineralogical description and pyrolysis kinetics

The Democratic Republic of the Congo holds important reserves of oil shale which is still under geological status.Herein,the characterization and pyrolysis kinetics of typeⅠkerogen-rich oil shale of the western Central Kongo(CK)were investigated.X-ray diffraction,Fourier-transform infrared spectroscopy and thermal analysis(TG/DTA)showed that CK oil shale exhibits a siliceous mineral matrix with a consistent organic matter rich in aliphatic chains.The pyrolysis behavior of kerogen revealed the presence of a single mass loss between 300 and 550°C,estimated at 12.5%and attributed to the oil production stage.Non-isothermal kinetics was performed by determining the activation energy using the iterative isoconversional model-free methods and exhibits a constant value with E=211.5±4.7 kJ mol.1.The most probable kinetic model describing the kerogen pyrolysis mechanism was obtained using the Coats–Redfern and Arrhenius plot methods.The results showed a unique kinetic triplet confirming the nature of kerogen,predominantly typeⅠand reinforcing the previously reported geochemical characteristics of the CK oil shale.Besides,the calculation of thermodynamic parameters(ΔH~*,ΔS~*andΔG~*)corresponding to the pyrolysis of typeⅠkerogen revealed that the process is non-spontaneous,in agreement with DTA experiments.

加强油源岩沉积成岩成油模拟实验研究

干酪根热降解生油学说源于油页岩高温热解生成“人造石油”的生产实践,其理论内涵是凡富含干酪根的岩石,经高温热解后其所含的干酪根都可以生成“人造石油”。应用该学说的高温热解实验方法,可以评价油页岩的品质及其热解生成“人造石油”的潜力,因此仅适用于油页岩的评价研究。但该学说的倡导者却认为油页岩和油源岩都是能生成石油的岩石,如果埋藏较浅时就称为油页岩,如果埋藏较深时就是油源岩,因此干酪根热降解生油学说同样适用于油源岩。这种观点并没有被美欧等国家所认可,但遗憾的是,在改革开放之初不甚了解国外同行对该学说如何评价的情况下,中国的石油地质家不仅全盘接受了该学说,而且推广应用了40多年。为彻底改变这种被动局面,唯一可行的就是通过油源岩沉积成岩成油模拟实验,研究油源岩中可溶有机质的生油问题和评价方法。

中国南方高成熟泥页岩有机质微观特征研究

页岩有机质孔隙对页岩气勘探开发有着重要的指示作用,对页岩气生成及运移机理的认知有着重要意义,是研究人员关注的焦点问题。本文采用自然断面制样方法,利用扫描电镜对中国南方高成熟泥页岩进行观察研究发现,有机质主要以三种形态存在于页岩中,一种是细微的颗粒状,微粒尺寸约10~100 nm,与周围矿物界限不明显;一种是呈块状,尺寸多超过10μm,断口表面光滑;一种是部分保留生物形态的有机质,从数量而言以前两种为主。结合有机质成因及特征,作者对其进行分类:第一种为干酪根,第二种为沥青,第三种为生物碎屑。干酪根和沥青中都可能生成孔隙,干酪根内孔隙尺寸较小,形态不规则,沥青中的孔隙尺寸较大,呈气泡状,孔壁较圆滑。因为在泥页岩中干酪根占比比固体沥青多,而且高成熟度的页岩中干酪根中普遍发育孔隙,沥青中较少发育孔隙,所以干酪根孔隙是有机质孔隙的主体。

页岩干酪根平均分子结构模型的构建方法

页岩中的主要有机成分是干酪根。一个真实的干酪根分子结构模型是利用分子动力学研究页岩有机质微观性质的基础。前人多建立二维干酪根模型,对三维干酪根结构模型的建立较少。因此,很有必要介绍一种建立页岩干酪根的三维分子结构模型的详细步骤。笔者等基于构建出的南堡页岩干酪根的二维分子结构模型,利用分子动力学模拟的手段,根据干酪根的密度.

松辽盆地古龙页岩油储层干酪根的有机元素组成及其N元素的地球化学意义

对青山口组页岩的317件干酪根样品进行了工业、元素及能谱分析,对样品进行两次校正,引入合理评价干酪根C、H、O、N的指标C_(cc)、H_(cc)、O_(cc)、N_(cc)概念。研究结果显示:古龙凹陷青山口组泥页岩Ⅰ型干酪根具有较高的H_(cc)、N_(cc)和很低的O_(cc),而Ⅲ型干酪根的O_(cc)则较高,H_(cc)、N_(cc)较低。Ⅱ干酪根的H_(cc)和N_(cc)低于Ⅰ型干酪根,而高于Ⅲ型干酪根;Ⅱ干酪根的O_(cc)高于Ⅰ型和Ⅲ型干酪根。N_(cc)主要以有机官能团(NH3+)方式存在的于黏土的F-F纳缝中,而不是存在于黏土晶胞间的无机N(NH4)。微量元素研究表明,古龙青山口组页岩油储层沉积时经历了十几次干旱咸水环境,因为咸水环境有利于形成黏土的F-F凝聚,使发育有NH3+官能团的有机质被吸附在黏土片的F-F纳缝之间。随着深度的增加,N_(cc)的克分子量增加速率是C_(cc)克分子量增加速率的0.96~2.04倍,在青山口组1300~2550m深度内青一段干酪根的N_(cc)含量明显比上部的干酪根相对高,主要原因与下部青一段藻类较富集有关,其次与H_(cc)的快速脱落而使N_(cc)相对富集有关,间接地揭示了青一段生烃能力较上部强。通过研究N_(cc)可以间接地知道古环境中的咸度、黏土的孔隙类型及其干酪根的来源。经过论证,O_(cc)和N_(cc)越大,页岩的封存性也就越好,含油气性也越好。因此,O_(cc)和N_(cc)值可以作为判别页岩油发育程度的指标。古龙页岩油储层的N_(cc)和O_(cc)的研究可以提供一些重要的沉积环境、地球化学、黏土结构、干酪根有机质类型和成岩成储及成藏等信息,应该受到重视。

Kerogen Kinetic Distributions and Simulations Provide Insights into Petroleum Transformation Fraction (TF) Profiles of Organic-Rich Shales

Two hundred and fifty single first-order Arrhenius reactions are simulated to generate S2 pyrograms at three heating rates 25,15,and 5°C·min-1.The activation energy(E)and pre-exponential factor(A)of the reactions simulated follow a long-established trend of those variable values displayed by shales and kerogens.The characteristics of the transformation fraction(TF)profiles(product generation window temperatures)of the simulated single reactions are compared to the TF profiles of recorded shale pyrograms generated by multiple reactions with different E-A values lying near the defined E-A trend.Important similarities and differences are observed between the TF profile values of the two datasets.The similarities support the spread of E-A values involved in shale pyrogram best fits.The differences are most likely explained by the complexity of the multiple kerogen first-order and second-order reactions contributing to the recorded shale pyrograms versus the simplicity and crispness of the single first-order reactions simulated.The results also justify the validity of using the previously described“variable E-A pyrogram-fitting method”of multi-heating-rate shale pyrograms enabling optimizers to choose multiple reactions from an unlimited range of E-A values.In contrast,further doubt is cast on the validity of the constant-A pyrogram-fitting method used by the Easy%Ro technique,in that a distribution of reactions with a single A value is unlikely to represent the complex variety of kerogen macerals observed in shale formations.TF profiles generated by the variable E-A pyrogram-fitting method lie close to the established E-A trend and are likely to provide more realistic TF generation window temperatures than TF profiles generated by the constant-A pyrogram-fitting method.

电磁加热协同纳米颗粒低成熟度陆相页岩油热解实验研究

我国中—低成熟度页岩油储量巨大,是缓解能源供需矛盾的重要非常规资源(郑瑞辉等,2023)。低成熟度页岩油在储层中以固态干酪根形式赋存,目前缺乏高效的开发技术手段。电磁加热不受页岩储层低孔、低渗的影响,能够作用于干酪根将其热解为油气。笔者等以低成熟度陆相页岩为对象并提取干酪根样品,系统开展电磁加热协同纳米催化干酪根热解实验研究.

A rock physics model for the characterization of organic-rich shale from elastic properties

Kerogen content and kerogen porosity play a significant role in elastic properties of organic-rich shales. We construct a rock physics model for organic-rich shales to quantify the effect of kerogen content and kerogen porosity using the Kuster and Toks6z theory and the selfconsistent approximation method. Rock physics modeling results show that with the increase of kerogen content and kerogen-related porosity, the velocity and density of shales decrease, and the effect of kerogen porosity becomes more obvious only for higher kerogen content. We also find that the Poisson＇s ratio of the shale is not sensitive to kerogen porosity for the case of gas saturation. Finally, for the seismic reflection responses of an organic-rich shale layer, forward modeling results indicate the fifth type AVO re- sponses which correspond to a negative intercept and a positive gradient. The absolute values of intercept and gradient increase with kerogen content and kerogen porosity, and present predictable variations associated with velocities and density.

Characterization and beneficiation of the Egyptian black shale for possible extraction of organic matter

The present paper focuses on obtaining concentrate enriched with organic matter that could be suitable for a retorting process from black shale; this is black shale from the Safaga area on the Red Sea Coast.X-ray diffraction and optical polarising microscope are used in evaluating black shale minerals. Attrition scrubbing and flotation were conducted for enrichment of organic matter in the black shale sample.Mineralogical studies revealed that black shale samples contain bituminous calcareous clay stone, quartz,apatite and pyrite. Rabah mine black shale contains 28% organic matter. The results of the different separation techniques indicate that attrition and flotation techniques successively enriched the organic matter in the black shale. The organic matter could be enriched in the black shale and obtained a concentrate with 59% assaying and 85% recovery.

深层页岩干酪根纳米孔隙中甲烷微观赋存特征

深层页岩储层甲烷高温高压条件下的赋存特征是准确评估页岩气储量的关键。首先,基于深层页岩龙马溪组干酪根分子结构单元,构建干酪根不同形状和孔径的纳米孔隙分子模型;然后,采用巨正则蒙特卡洛和分子动力学耦合方法,开展甲烷赋存模拟,分析压力、温度、孔径和孔隙形状对甲烷赋存量的影响规律;最后,研究甲烷微观赋存机理,分析甲烷微观分布特征、甲烷-壁面微观作用特征以及甲烷优先吸附位。研究表明:在深层高压条件下,甲烷过剩吸附量和溶解量受温度影响较小;随温度升高,甲烷绝对吸着量和游离气体量减少;干酪根介孔孔径对甲烷吸附气和溶解气量基本无影响,孔径引起的总气体量变化主要由游离气贡献;与圆管孔相比,狭缝孔中甲烷总气体量更大,但过剩吸附量较少;甲烷分子优先吸附于干酪根结构上的噻吩位点。研究结果为深层页岩气储量评估提供了理论依据。

Geochemical Study of Oil Shales Sargelo Formation in Kuh-e Kaino Section (Northern Masjed-Soleiman), Iran

Oil (bituminous) shales source rocks with variable amounts of solid kerogen type II are the conditions for changing the oil that is not provided for them. Each of these shales affected in temperature about 150 to 170 gallons of oil produced. Therefore by reducing hydrocarbon resources, it can be a good energy source for the future. To study the geochemistry of this shale, one section of outcrops in the Kuh-e Kaino (Northern Khozestan) was selected which was located in the central Zagros. Chemical analysis and thin sections were prepared from samples of carbonate shale. These deposits with a thickness of 115 m of the Lower Jurassic formations Neyriz and Sargelo relative age and their relationship are gradual and interfinger. The upper border after an erosional unconformity, Fahliyan Formation of Lower Cretaceous age on them covered. Analysis results show that the percentage of organic matter this shales in Kuh-e Kainois is equivalent to 8.44 percent. The index has gained economic value of metal elements Sr, V, Ba, Ni, and also has economic value. Bituminous materials formed stabilize in shaley source rock of Sargelo formation, but not with continuous deposition on them, as a result of temperature and pressure not increasing and immature kerogen. The causes of this event are as follows: the basin tectonic condition, Stratigraphy position and faults activity in the basin.

龙马溪组页岩干酪根表征初探及干酪根吸附特征研究

吸附气是页岩气赋存在页岩中的主要方式之一,而且吸附气是页岩气后期产量的主要来源。吸附气主要赋存在页岩有机质干酪根和黏土矿物中,而有机质干酪根中吸附比例较大。因此,研究页岩有机质干酪根的特征及其吸附机理对页岩气开发有重要作用。以四川盆地龙马溪组页岩干酪根为研究对象,通过固体核磁共振谱分析实验、傅里叶变换红外光谱(FTIR)分析实验、X射线光电子能谱(XPS)实验相结合的方法表征干酪根的微观结构,构建了干酪根的分子结构模型。利用磁悬浮重量法实验、巨正则系综蒙特卡洛(GCMC)和分子动力学(MD)的分子模拟方法,分析CH_(4)在龙马溪组页岩干酪根的吸附机理及特征。研究结果表明:龙马溪组页岩实验样品干酪根的分子式为C_(237)H_(219)O_(21)N_(5)S_(4);CH_(4)在干酪根中的超额吸附量随着压力的增加先升高后降低;相同孔径和压力条件下,随着温度的升高,CH_(4)的超额吸附量和总气量逐渐变小;干酪根中的C原子和S原子是造成CH_(4)吸附的主要原因;靠近干酪根孔壁的CH_(4)呈现吸附态,远离干酪根孔壁的CH_(4)呈现游离态,随着孔径的增加,CH_(4)密度的两峰之间的距离逐渐变宽,峰值逐渐下降。

川东北地区自流井组页岩有机地球化学特征及油气勘探意义

为查明陆相页岩烃源特征及生油气潜力,采用有机碳含量(TOC)、镜质体反射率(Ro)、有机岩石学、干酪根碳同位素及族组分碳同位素测定等多种测试方法,开展川东北不同地区自流井组页岩有机地球化学特征及对比研究,明确主要地化参数特征及差异,并重点探讨有机质类型的研究对页岩油气勘探的意义。研究结果表明:自流井组东岳庙段与大安寨段页岩w(TOC)主要介于0.5%~2.0%,平均值>1.2%,有机显微组分以镜质体、丝质体为主,其次为固体沥青及微粒体,Ⅱ1、Ⅱ2及Ⅲ型有机质均有发育,以Ⅱ2型为主,有机质处于成熟-高成熟阶段,具备较好的页岩油气勘探潜力;川东涪陵地区东岳庙段东一亚段页岩有机质类型纵向上频繁变化,向上东二亚段—东三亚段页岩干酪根碳同位素存在倒转变轻现象,推测与运移烃混入有关,并提出页岩层段纵向上有机质类型变化的精细确定,有助于判识不同层段生烃能力与有机质孔发育程度的差异。

页岩油在干酪根中吸附行为的分子动力学模拟与启示

有机质及其相关孔隙吸附行为的研究对于揭示页岩油赋存状态与机理有重要意义。不同于以往采用石墨烯模型代替有机质的方法,研究采用真实的干酪根分子模型(Ⅱ-C型),基于GAFF(general Amber force field)力场模拟了有机孔内页岩油多组分体系下的吸附行为。结果表明:(1)与石墨烯仅能模拟壁面吸附不同,干酪根对页岩油具有吸附和吸收双重作用:壁面上存在页岩油竞争吸附,以极性和重质组分吸附为主,而骨架中则存在页岩油组分吸收现象,小分子迁移距离较远。页岩油在干酪根壁面上的吸附和在骨架中的迁移受控于页岩油与干酪根相互作用能的强弱及分子大小,重质组分表现出“强吸附-弱吸收”、轻质组分呈“弱吸附-强吸收”的特征。(2)页岩油组分的吸收使得干酪根骨架和孔隙发生变化,表现出新孔隙的形成、原有孔隙的扩大和部分塌陷。干酪根的塑性对吸收页岩油进而膨胀起重要作用,干酪根塑性较强时(干酪根成熟度低),页岩油更容易被吸收从而引发明显的干酪根骨架膨胀,反之,干酪根膨胀较弱。(3)温度增加会促进干酪根骨架吸收芳香烃分子萘和非极性分子甲酸、乙醇以及噻吩,降低干酪根壁面的吸附作用,同时有利于饱和烃类分子的脱附。压力对页岩油在干酪根中的吸附和吸收影响不明显。研究利用真实的干酪根分子模型,首次创新性地模拟了干酪根吸附和吸收页岩油组分的现象,对于客观揭示页岩油在干酪根中赋存状态及赋存机理具有重要帮助。

中—低成熟度页岩油原位转化对储集层的改造能力

中国中—低成熟度页岩油资源丰富,原位转化潜力巨大。为评价中—低成熟度页岩油原位转化对储集层的改造能力,对鄂尔多斯盆地延长组长7段和准噶尔盆地吉木萨尔凹陷芦草沟组2种典型中—低成熟度页岩开展了原位加热实验。利用核磁共振测试、立式光学显微镜观测、计算机断层扫描和脉冲衰减气体渗透率测量等,实时监测了原位转化中纳米孔隙、热解裂缝以及孔隙度和渗透率在高温高压下的动态变化。干酪根热解引起的热解裂缝与生烃增压效应,是微观结构和储集层物性显著改善的关键。当温度超过400℃的阈值后,随着干酪根热解和烃类热膨胀,页岩内部裂缝网络的延伸度、密度、复杂性和连通性均显著提高,大量直径在2~50nm的次生孔隙占据孔隙结构的主导地位。原位应力下,2种页岩孔隙度可分别增加至3.65倍和2.73倍,渗透率可分别增加至624.09倍和418.37倍。渗透率在高温阶段比低温阶段表现出更强的应力敏感性。原位应力越低,干酪根含量越高的页岩储集层,原位转化的改造能力越高,储集层热破裂和热增渗能力也越高。

干酪根组成结构及其热解生油特性的红外光谱研究

对五种不同地区油页岩中干酪根进行了固体KBr压片红外吸收光谱分析，并通过曲线分峰拟合建立了干酪根中脂肪烃区域结构参数的定量测定方法。利用TG—FrIR联用分析技术对干酪根在20℃／min升温速率下热解挥发分析出组分在线定性分析，得到了脂肪烃结构参数随热裂解过程的反应特性及变化规律。研究表明，油页岩中干酪根由脂肪烃结构、芳香烃结构和含氧等官能团三部分组成。脂肪烃结构相对含量为18．5％-78．2％，并均以含长链亚甲基结构为主。随着演化程度的加深，干酪根中脂肪烃含量逐渐减少，生油能力也不断降低。干酪根热分解主要发生在350—520℃，520℃后热失重现象趋于平缓，在此温度下各样品残余半焦的质量分数为19．5％～52．2％。在线红外分析结果表明，干酪根热裂解过程中先析出游离水，随后发生解聚和脱水反应，主要的烷基侧链不断脱落、环化及含氧基团逐渐断裂生成各种烷烃类、羧酸类、醇类和醛类等物质，直至形成更加稳定的类石墨态结构。