前寒武纪——早古生代沉积岩显微组分分类、成因及演化

前寒武纪—早古生代沉积岩时代古老、生源简单,但有机显微组分面貌却很复杂。通过对大量国内外自然演化和人工熟化系列样品的观察和分析,基于生源、成因、沉积转化及热成熟作用4个主控因素,提出将古老沉积岩的显微组分划分为类镜质组、腐泥组、固体沥青组、动物有机碎屑组和惰质组。低成熟的古老海相烃源岩的显微组分组成以层状藻类体、沥青质体和矿物沥青基质为主;高-过成熟的古老海相烃源岩的显微组分组成以源内固体沥青为主;笔石表皮体常见于五峰组-龙马溪组页岩,是其中有机质的重要组成部分。进一步分析了其中最具特征且以往易被忽视的显微组分的成因,前寒武纪样品中类镜质组颗粒的成因可能为早期成岩过程低等水生生物遭受微生物降解所形成;源内固体沥青为经一次运移残留在烃源岩内的可溶有机质裂解后的固体残留物或者腐泥组残余干酪根吸收同化可溶有机质后的热演化固相产物。通过自然演化系列样品和热模拟样品的综合研究,明确了中国高-过成熟的前寒武纪、寒武纪和奥陶纪—志留纪含笔石页岩有机质的“前世”分别类似于中元古代下马岭组、寒武纪Alum页岩和奥陶纪含笔石Alum页岩有机质的“今生”,提出笔石表皮体、类镜质组颗粒和源内固体沥青反射率都可以用于表征前寒武纪—早古生代海相烃源岩有机质热演化程度。

沉积盆地超深层有机-无机复合生烃机理及地质模式

全球范围内超深层油气的不断发现,对经典的生烃理论提出了挑战,外源氢加入的有机-无机复合生烃过程引起了广泛关注。基于地质观察统计数据,分子氢在沉积盆地中分布广泛,形成机制复杂。在地质环境中,水和水-岩反应、深部流体等途径产生的无机氢是最主要的外部氢源。可控加氢模拟实验揭示了沉积盆地的氢逸度水平是调控烃类产物生成的重要因素之一,并且干酪根的加氢裂解是沉积盆地中易于发生的生烃过程。外源氢介入生烃过程的前提是环境氢逸度大于沉积有机质本身的氢逸度,其有效范围受生烃母质化学组成和结构的制约,约起始于生油高峰之后,约终止于沉积有机质H/C=0.3之时。亦即,有机-无机复合生烃作用是沉积盆地超深层生烃的有效途径。在其有效发生的范围内,油气资源类型依然由生烃母质类型(化学组成和结构)、成熟度和受热历史等因素决定,具有明显的阶段性和不同于经典理论的生烃模式。外源氢的参与,在成熟阶段可小幅度提升生油产率;在高—过成熟阶段可显著增加天然气产率;在高成熟阶段,加氢脱烷基作用最大可增加50%的轻质油/凝析油产率;在过成熟阶段,加氢脱甲基-开环作用最大可增加约5倍甲烷产率。有机-无机复合生烃模式的确立,丰富了传统生烃理论的内涵,奠定了超深层油气生成的理论基础,拓展了油气勘探的视野。

华北北部中元古界下马岭组页岩有机岩石学研究

华北北部中元古界下马岭组页岩是中国最古老的海相烃源岩之一,生源简单,有机质丰度高且成熟度低,但目前仍缺少对其显微组分面貌和成因的详细研究。通过有机岩石学方法,研究了下马岭组页岩中显微组分的组成、特征及其成因。结果表明,下马岭组页岩中显微组分组成较复杂,包括沥青质体、层状藻类体、类镜质组颗粒、矿物沥青基质和沥青铀钍矿。在显微镜下观察到类镜质组颗粒、沥青质体和层状藻类体存在光性过渡变化,它们的随机反射率呈现出逐渐减小的趋势,荧光逐渐增强。这种光性的过渡变化与它们的成因紧密相关。随着缺氧微生物降解作用的逐渐增强,层状藻类体会逐步降解形成沥青质体和类镜质组颗粒。有机质遭受放射性矿物颗粒的离子辐射聚合作用后形成沥青铀钍矿,其中放射性矿物颗粒主要为独居石和钍石。放射性矿物颗粒的热辐射对有机质成熟度有一定的影响,但是影响范围较小。

Status quo of soil petroleum contamination and evolution of bioremediation

Along with the rapid development of oil industries internationally,petroleum prospecting and exploitation activities are growing intensively.Especially in China,with the fastest economic growth in the world and shortage of petroleum resources,we are leading the practices of petroleum deep exploitation.Obviously,the risk of damage to the natural environment from these activities is high.Oil contamination in soils and groundwater is becoming a big issue along with pesticide pollution,which makes organic pollution prevention and control （OPPC） much more complex.In this paper,based on recent research on oil-contaminated soil at home and abroad,we make comments on the remediation technologies for polluted soil,emphasizing bioremediation techniques and degradation mechanisms in order to push forward research into bound organic pollution prevention and control （OPPC）,especially in China.

Pore Characteristics and Factors Controlling Lacustrine Shales from the Upper Cretaceous Qingshankou Formation of the Songliao Basin,Northeast China:A Study Combining SEM,Low-temperature Gas Adsorption and MICP Experiments

To investigate pore characteristics and the factors controlling lacustrine shales,geochemical,mineralogical and petrophysical experiments were performed on 23 shale samples from the Qingshankou Formation of the Songliao Basin,China.A comparison of mercury injection capillary pressure(MICP)and low-temperature N2 adsorption pore-size distribution showed that MICP has a higher pore-size distribution(PSD)line in its overlapping pore diameter range,which may be elevated by the higher pressure of MICP.Therefore,in the overlapping range,low-temperature N2 adsorption data were preferred in pore characterization.Negative correlations were observed between pore volumes and TOC content,indicating organic matter pores are not well-developed in the studied samples.This may be related to their low grade of maturity and type I kerogens.There existed negative relationships between pore volumes and S1,which illustrated that liquid hydrocarbons occupied some pore space.Micropore volume had a better correlation with S1 than mesopore and macropore volumes,which suggests that liquid hydrocarbons preferentially occur in micropores.No obvious relationships between pore volumes and quartz or feldspar were observed,while pore volumes increased with the increasing clay mineral content.These relationships indicate that intraparticle pores in clay minerals represent the principal pore type.

A GC×GC-ToFMS Investigation of the Unresolved Complex Mixture and Associated Biomarkers in Biodegraded Petroleum

Heavy biodegraded crude oils have larger numbers of coeluting compounds than nonbiodegraded oils, and they are typically not resolved with conventional gas chromatography（GC）. This unresolved complex mixture（UCM） has been investigated using comprehensive two-dimensional gas chromatography–time-of-flight mass spectrometry（GC×GC-To FMS） within a set of biodegraded petroleums derived from distinct sedimentary basins, including northwestern Sichuan（Neoproterozoic, marine）, Tarim（Early Paleozoic, marine）, Bohai Bay（Eocene, saline/brackish） and Pearl River Mouth（Eocene, freshwater）. In general, the hydrocarbons that constitute the UCM in petroleum saturate fractions can be classified into three catalogues based on the distributions of resolved compounds on two dimensional chromatograms. Group 1 is composed mainly of normal and branched alkanes, isoprenoid alkanes and monocyclic alkanes; Group 2 comprises primarily terpanes ranging from two to five rings, and Group 3 is dominated by monoaromatic hydrocarbons such as tetralins and monoaromatic steranes. In addition, the UCM is source dependent and varies between oil populations. i.e., the UCM of petroleum derived from Precambrian and Early Paleozoic marine, Eocene saline/brackish and freshwater source rocks is specifically rich in higher homologues of A-norsteranes, series of 1,1,3-trimethyl-2-alkylcyclohexanes（carotenoid-derived alkanes）, and tetralin and indane compounds, respectively.

Differential Thermal Regimes of the Tarim and Sichuan Basins in China:Implications for Hydrocarbon Generation and Conservation

The uncertainty surrounding the thermal regimes of the ultra-deep strata in the Tarim and Sichuan basins,China,is unfavorable for further hydrocarbon exploration.This study summarizes and contrasts the present-day and paleo heat flow,geothermal gradient and deep formation temperatures of the Tarim and Sichuan basins.The average heat flow of the Tarim and Sichuan basins are 42.5±7.6 mW/m^(2)and 53.8±7.6 mW/m^(2),respectively,reflecting the characteristics of’cold’and’warm’basins.The geothermal gradient with unified depths of 0-5,000 m,0-6,000 m and 0-7,000 m in the Tarim Basin are 21.6±2.9℃/km,20.5±2.8℃/km and 19.6±2.8℃/km,respectively,while the geothermal gradient with unified depths of 0-5,000 m,0-6,000 m and 0-7,000 m in the Sichuan Basin are 21.9±2.3℃/km,22.1±2.5℃/km and23.3±2.4℃/km respectively.The differential change of the geothermal gradient between the Tarim and Sichuan basins with depth probably results from the rock thermal conductivity and heat production rate.The formation temperatures at depths of 6,000 m,7,000 m,8,000 m,9,000 m and 10,000 m in the Tarim Basin are 80℃-190℃,90℃-220℃,100℃-230℃,110℃-240℃and 120℃-250℃,respectively,while the formation temperatures at depths of 6,000 m,7,000 m,8,000 m and 9,000 m in the Sichuan Basin are 120℃-200℃,140℃-210℃,160℃-260℃and 180℃-280℃,respectively.The horizontal distribution pattern of the ultra-deep formation temperatures in the Tarim and Sichuan basins is mainly affected by the basement relief,fault activity and hydrothermal upwelling.The thermal modeling revealed that the paleo-heat flow in the interior of the Tarim Basin decreased since the early Cambrian with an early Permian abrupt peak,while that in the Sichuan Basin experienced three stages of steady state from Cambrian to early Permian,rapidly rising at the end of the early Permian and declining since the late Permian.The thermal regime of the Sichuan Basin was always higher than that of the Tarim Basin,which results in differential oil and gas generation and conservation in the ultra-deep ancient strata.This study not only promotes theoretical development in the exploration of ultra-deep geothermal fields,but also plays an important role in determining the maturation phase of the ultra-deep source rocks and the occurrence state of hydrocarbons in the Tarim and Sichuan basins.

Combination and superimposition of source kitchens and their effects on hydrocarbon accumulation in the hinterland of the Junggar Basin,west China

In the hinterland of the Junggar Basin, there are multiple depressions with multiple sets of source rocks. Therefore, the conditions of hydrocarbon sources are complex, and the geochemical characteristics and sources of hydrocarbon vary in different structural belts. The evolution of the Che- Mo palaeohigh affected the formation of hydrocarbon source kitchens and hydrocarbon migration. We studied the combination and superimposition of hydrocarbon source kitchens, using as an example the hinterland of the Junggar Basin （including the Yongjin, Zhengshacun, Moxizhuang and Luliang uplift areas）. The study was based on geochemical analyses of crude oil and fluid inclusions, and the histories of tectonic evolution and hydrocarbon generation. The results indicated that before the Paleogene there were two hydrocarbon-generating depressions： the Western Well Penl depression and the Changji depression on the south and north sides of the Che-Mo palaeohigh, respectively. The Permian source kitchen had been generating hydrocarbon continuously since Triassic and reached high maturity stage in the Cretaceous period. After Paleogene, the adjustment of the Che-Mo palaeohigh led to the subsidence of the Changji depression and the Jurassic source rocks reached mature stage and became the main source kitchens. However, the Jurassic source rocks in the Western Well Penl depression were still in a low maturity stage and did not generate oil because of the adjustment of tectonic movements. As a result, in the central and southern parts of the Junggar Basin, Jurassic source rocks generated oil, but in the Luliang uplift, the crude oil was from the Permian source rocks in the Western Well Penl depression and the Jurassic source rocks did not contribute. The crude oil in the central Zhengshacun-Moxizhuang belt was from the Permian source rocks in two depressions, and partially from the Jurassic source rocks. The crude oil in the Luliang uplift was from the source rocks of the lower Permian Fengcheng Formation and middle Permian Wuerhe Formation, which is characterized by superimposition of two sets of source kitchens and three accumulation stages. The crude oil in the Yongjin tectonic belt was from the lower Permian, middle Permian and Jurassic source rocks, which is characterized by superimposition of three sets of source kitchens and two accumulation stages. The crude oil in the Zhengshacun tectonic belt was from a combination of source kitchens of lower Permian and middle Permian in the Western Well Penl depression in the early stage and from the superimposition of Jurassic source rocks in the Changji depression in the late stage.

New progress and future prospects of CBM exploration and development in China

Efforts to speed up China's coal bed methane (CBM) exploration developments related to production safety, optimization of energy structures, prevention of energy waste and reduction of greenhouse gas emissions are all of great significance. In order to strengthen CBM exploration and development in China and to encourage increased growth in the CBM industry, we firstly give a general overview of the recent technological innovations and other developments in CBM exploration in the U.S., Canada and other countries. Using this background information as the starting point, we further present observations and analyses of CBM exploration and development, preferential policies, technical support and implications of R&D for CBM development in China. The results show that the problems related to CBM exploration technology development and lack of a complete set of management policies are still the major issues slowing down the growth of domestic CBM industry. Development of resource exploration and technology, R&D and establishment of favorable government policy to support the industry and the creation of a relevant information platform, etc. are finally recommended.

Geochemistry of source rocks in the Es_3 and Es_4 members in the Shahejie Formation of the Western Depression, Liaohe Oilfield, China

The Western Depression of the Liaohe Basin is the major exploration area of the Liaohe Oilfield, and its main source rocks consist of the third and fourth members of the Shahejie Formation (Es3 and Es4). These source rocks are widely distributed in the depression, with semi-deep lake and fan delta as the main sedimentary facies, brown oil shale and black gray-dark gray mudstone as the main rocks, and a total thickness of 270-1450 m. The kerogens are mainly of the types I and IIA, and partly of the type IIB and least of the type III. The Ro values range from 0.4%-0.8%, indicating an evolution stage from immature to mature. The maturity of Es4 source rocks is rela-tively high, reaching the early mature stage, but their distribution and thickness are lower than those of Es3. Besides, according to biomarker analysis, it is thought that the source rocks of Es3 and Es4 are characterized by mixed input, and most of the source rocks were formed in the brackish water-saline and strongly oxygen-free environment. Fur-thermore, the Qingshui, Niuxintuo and Chenjia sags are believed to possess greater potential for hydrocarbon gen-eration and expulsion, for they are source rocks with a larger thickness, have higher organic carbon contents, belong to better organic matter types and possess higher maturities.

The geochemical characteristics and genetic types of crude oils in the western depression of the Liaohe Basin,China

The physical properties and group compositions of crude oils in the western depression of the Liaohe Basin possess such characteristics as to increase gradually in density, viscosity and wax contents, and decrease in saturated hydrocarbon and non-hydrocarbon and bitumen contents from the deep level to the shallow level and from the center of the depression to its boundary. Saturated hydrocarbons have various spectra, such as single peak and double peak patterns, front peak and rear peak patterns, and smooth peak and serated peak patterns, as well as the chromatograms of biodegraded n-alkanes. The ratios of Pr/Ph in crude oils from the southern part of the depression are generally higher than those in the northern part. The distribution of regular steranes C27-C29 is predominantly of the ramp type, and only a few samples have relatively high C28 contents in the southern part of the depression. As viewed from their physical properties and geochemical characteristics, crude oils in the study area can be divided into two types (I and II) based on oil-generating sources and sedimentary environments, and then further divided into three sub-types (Ia, Ib and Ic:IIa, IIb and IIIc, respectively) based on their degrees of maturation and secondary transformation. This will provide the reliable basis for oil-source correlation and petroleum exploration and prediction.

Model and methods for comprehensive measurement of the low-carbon status of China's oil and gas enterprises

This paper establishes a model that would allow China＇s oil and gas enterprises to scientifically evaluate and measure their low-carbon level and status. It considers various characteristics of China＇s oil and gas enterprises and the implications of low-carbon development, and is based on an overall analysis of factors that influence the reduction of carbon emissions. In view of low-carbon economic theories and the general principles of an evaluation index system, a comprehensive system for measuring the low-carbon status of China＇s oil and gas enterprises has been developed. This measurement system is comprised of four main criteria （energy structure, energy utilization, carbon emissions and utilization, and low carbon management） as well as thirty indexes. By the Delphi method and the analytical hierarchy process （AHP）, the weight of the rules hierarchy and indexes hierarchy were determined. The standardized indexes were then integrated using a linear weighted sum formula, and a comprehensive formula for index measurement was established. Taking into account the status of low- carbon development in the petroleum and petrochemical industry at home and abroad, an evaluation criterion is proposed comprising four levels： ideal low-carbon, economical low-carbon, medium-carbon and high-carbon, whose values were organized within the settings of [0, 1].

Existence and implications of hop-17(21)-enes in the lower Cretaceous of the Saihantala Sag, Erlian Basin, China

C31- to C35-hop-17（21）-enes are identified by gas chromatography-mass spectrometry （GC-MS） analysis to exist as double isomers in most samples of the Aershan Formation and members 1 and 2 of the Tenggeer Formation from well SH3. Comprehensive organic geochemistry and organic petrology study indicates that algae and bacteria are the main biological source of lower Cretaceous sediments in the Saihantala Sag, and this is in accordance with the existence of hop-17（21）-enes. The similar distributions of hop-17（21）-enes and hopanes of these samples indicate that hop-17（21）-enes were transformed into hopanes through hydrogenation during diagenesis processes. The existence of hop-17（21）-enes means that not only the formation of organic matter is related to an anoxic environment and a biological source of algae and bacteria, but also hop-17（21）-enes are direct indicators of hydrocarbon rock at an immature to low-maturity stage. High hydrocarbon conversion ratio, algae and bacteria source and a high abundance of organic matter suggest that the Saihantala Sag has the potential to generate immature to low-maturity oil, which may be of great significance for oil exploration in the Erlian Basin.

Correlation of burial organic carbon and paleoproductivity in the Mesoproterozoic Hongshuizhuang Formation, northern North China

In general, total organic carbon (TOC) is directly used as a proxy for paleoproductivity, however, it is not only affected by paleoproductivity, but also controlled by redox conditions and terrigenous detrital matter influx. Major and trace elements were analysed with the purpose of investigating the redox potential and paleoproductivity during deposition of the Hongshuizhuang Formation. In the present study, C-S relationship, V/Cr ratio and Mo concentration indicate that the dolomites were deposited in oxic environments, however, most of the black shales were accumulated in euxinic environments. P/Ti values in the Hongshuizhuang samples can be compared with those in the Japanese Ubara Permian-Triassic section which were regarded to be deposited under a moderate to high paleoproductivity. Ba/Al values are slightly lower than that of the laminated sediments from the continental margins of Central California (CCAL) which were thought to be accumulated under a high paleoproductivity. These results indicate that the paleoproductivity was moderate to high during deposition of the Hongshuizhuang Formation. Burial organic carbon shows positive correlations with V/Cr and Mo, but shows only weakly or no correlation with P/Ti and Ba/Al, respectively, suggesting that although the paleoproductivity was moderate to high during deposition of the Hongshuizhuang Formation, its organic-rich sediments were predominantly controlled by redox conditions and had no direct relationship with paleoproductivity.

Chemical kinetics study of hydrocarbon regeneration from organic matter in carbonate source rocks and its significance

In the comparison research of hydrocarbon regeneration, a low maturity carbonate source rock is heated to different temperatures in a gold tube to obtain a series of samples with different maturities. Then, the heated samples, before and after extraction, are subjected to Rock-Eval pyrolysis through a thermal simulation of hydrocarbon regeneration in order to inspect pyrolysis characteristics and probe into the characteristics of the chemical kinetics of each sample. The results indicate that, whether hy- drocarbon regeneration peak is delayed or advanced, the potential of hydrocarbon regeneration is closely related to the expulsion amount and breakdown maturity of primary hydrocarbon generation. After extraction, the average activation energy of artificially maturated samples increases with the in- creasing maturity, but the chemical kinetic properties of un-extracted samples decrease. The calibrated chemical kinetic models that describe extracted and un-extracted samples are applied to the Bohai Bay and the Songliao Basin, and the results indicate that the combination of the two models can explain some contradictory conclusions previously reported. These results also facilitate the quantitative evaluation of the amount of hydrocarbon regeneration by the chemical kinetic method.

Definition and sturcture characteristics of pores in mylonitized organic-rich shales

Gas shales with a high gas content were drilled in the Lower Cambrian Lujiaping Formation in the northeastern Sichuan Basin,close to the Chengkou Fault in the Dabashan arc-like thrust fold belt.The equivalent vitrinite reflectance values of organic matters are over 4.0%Ro.The pore structures of the shales were investigated based on microscopy,field emission scanning electron microscopy(FESEM)observations,and low temperature N2 adsorption analysis.The study suggests that cleavages,comprising clay minerals mixed up with organic matter and other insoluble residues,were developed in the rock layers.The clay minerals are directionally arranged,displaying a mylonitized texture.Abundant nanometer-size organic matter and clay mineral particles are well mixed in the cleavage domains,which developed the mylonitized pore system that consists of nanometer-size intergranular pore spaces,aggregate pore spaces in clay mineral flakes and pore network.This mylonitized pore system has high specific surface area,high methane adsorption capacity,and high capillary pressure,which collectively contributes to the preservation of shale gas in such a complex tectonic area.The discovery of the mylonitized pore structure in organic-rich shales may reveal a new mechanism of shale gas enrichment in complex tectonic areas with over-mature organic matter in the northeastern part of Sichuan Basin.

Simulation experiments on the reaction system of CH_4-MgSO_4-H_2O

H2S-rich gas in carbonate reservoirs is usually attributed to thermochemical sulfate reduction (TSR). In this paper, thermal simulation experiments on the reaction system of CH4-MgSO4-H2O were carried out using autoclave at 425℃―525℃. The threshold temperature for initiating TSR is much lower than our previous studies (550 ℃ ). Properties of the reaction products were analyzed by microcoulometry, gas-chromatography (GC), Fourier transform-infrared spectrometry (FT-IR) and X-ray diffraction (XRD) methods. Thermodynamics and reaction kinetics of TSR processes were investigated on the basis of the experimental data. The results show that thermochemical reduction of magnesium sulfate with methane can proceed spontaneously to produce magnesium oxide, hydrogen sulfur, and carbon diox-ide as the main products, and high temperature is thermodynamically favorable to the reaction. Ac-cording to the reaction model, the calculated activation energy of TSR is 101.894 kJ/mol, which is lower than that by most previous studies. Mg2+ may have played a role of catalytic action in the process of TSR. The elementary steps of TSR and reaction mechanism were discussed tentatively. The study can provide important information on the explanation of geochemical depth limit for natural gas and on the generation of high H2S gas in deep carbonates reservoirs.

Identification of acephenanthrylene and aceanthrylene in aerosol and its environmental implication

Acephenanthrylene and aceanthrylene in aromatic fraction of aerosols were identified by means of online hydrogenation gas chromatography mass spectrometry(GCMS). Compared aerosols from vari- ous sources, acephenanthrylene and aceanthrylene were ubiquitously present in urban aerosol. High concentration of acephenanthrylene and aceanthrylene were found in agricultural biomass and coal combustion particles. However, it is difficult to detect in exhaust from gasoline and diesel engine, dustfall, waste water, soil, and sediment. Combustion emissions were considered the major source of acephenanthrylene and aceanthrylene, which can be used as a potential molecular marker for the source pollution in urban aerosols.