Maceral evolution of lacustrine shale and its effects on the development of organic pores during low mature to high mature stage:A case study from the Qingshankou Formation in northern Songliao Basin,northeast China

Organic matter(OM)hosted pores are crucial for the storage and migration of petroleum in shale reservoirs.Thermal maturity and macerals type are important factors controlling the development of pores therein.In this study,six lacustrine shale samples with different thermal maturities from the first member of the Qingshankou Formation in the Songliao Basin,of which vitrinite reflectance(R_(o))ranging from 0.58% to 1.43%,were selected for a comparative analysis.Scanning electron microscopy(SEM)and reflected light microscopy were combined to investigate the development of organic pores in different macerals during thermal maturation.The results show that alginite and liptodetrinite are the dominant primary macerals,followed by bituminite.Only a few primary organic pores developed in the alginite at the lowest maturity(R_(o)=0.58%).As a result of petroleum generation,oil-prone macerals began to transform to initial-oil solid bitumen at the early oil window(R_(o)=0.73%)and shrinkage cracks were observed.Initial-oil solid bitumen cracked to oil,gas and post-oil bitumen by primary cracking(R_(o)=0.98%).Moreover,solid bitumen(SB)was found to be the dominant OM when R_(o)>0.98%,which indicates that SB is the product of oil-prone macerals transformation.Many secondary bubble pores were observed on SB,which formed by gas release,while devolatilization cracks developed on migrated SB.Additionally,at the late oil window(Ro?1.16%),migrated SB filled the interparticle pore spaces.With further increase in temperature,the liquid oil underwent secondary cracking into pyrobitumen and gas,and spongy pores developed on the pyrobitumen at higher levels of maturity(Ro=1.43%),which formed when pyrobitumen cracked into gas.Vitrinite and inertinite are stable without any visible pores over the range of maturities,verifying their low petroleum generation potential.In addition,it was concluded that clay minerals could have a catalytic effect on the petroleum generation,which may explain why organicclay mixtures had more abundant pores than single OM particles.However,after R_(o)>0.98%,authigenic minerals occupied the organic pore spaces on the organic-clay mixtures,resulting in fewer pores compared to those observed in samples at the early to peak oil window.

Research on the maceral characteristics of Shenhua coal and efficient and directional direct coal liquefaction technology

In this research,molecular structure models were developed respectively for Shenhua coal vitrinite concentrates(SDV)and inertinite concentrates(SDI),on the basis of information on constitutional unit of Shenhau coal and elemental analysis results obtained from^(13)C-NMR analysis characterization,FTIR analysis characterization,X-ray diffraction XRD and XPS analysis characterization.It can be observed from characterization data and molecular structure models that the structure of SDV and SDI is dominated by aromatic hydrocarbon,with aromaticity of SDI higher than that of SDV;SDV mainly consists of small molecule basic structure unit,while SDI is largely made from macromolecular structure unit.Based on bond-level parameters of the molecular model,the research found through the autoclave experiment that vitrinite liquefaction process goes under thermodynamics control and inertinite liquefaction process under dynamics control.The research developed an efficient directional direct coal liquefaction technology based on the maceral characteristics of Shenhua coal,which can effectively improve oil yield and lower gas yield.

Paleo-fires and Atmospheric Oxygen Levels in the Latest Permian:Evidence from Maceral Compositions of Coals in Eastern Yunnan,Southern China

Inertinite maceral compositions of the Late Permian coals from three sections in the terrestrial and paralic settings of eastern Yunnan are analyzed in order to reveal the paleo-fire events and the atmospheric oxygen levels in the latest Permian. Although the macerals in the studied sections are generally dominated by vitrinite, the inertinite group makes up a considerable proportion. Its content increases upward from the beginning of the Late Permian to the coal seam near the Permian- Triassic boundary. Based on the microscopic features and the prevailing theory that inertinite is largely a by-product of paleo-fires, we suggest that the increasing upward trend of the inertinite abundance in the latest Permian could imply that the Late Permian peatland had suffered from frequent wildfires. Since ignition and burning depend on sufficient oxygen, a model-based calculation suggests that the 02 levels near the Wuchiapingian/Changhsingian boundary and the Permian-Triassic boundary are 27% and 28% respectively. This output adds supports to other discoveries made in the temporal marine and terrestrial sediments, and challenges the theories advocating hypoxia as a mechanism for the PermianTriassic boundary crisis.

Study on the pyrolysis behavior of Shendong Shangwan coal and its macerals concentrate

The pyrolysis characteristics of Shendong Shangwan coal and its macerals concentrate were investigated using thermogravimetry （TG） coupled with mass spectrometry （MS）. The evolved gases were analyzed online by MS spectroscopy. The results of TG/DTG （derivative thermogravimetry） show ths vitrinite concentrate has greater weight loss rate and higher volatile yield than the other two samples. More light hydrocarbons C1-C5 are released from the vitfinite concentrate than from the Shendong Shangwan coal and inertinite concentrated in the process of pyrolysis. Three samples have similar shape curves of evolved gases of C2~C5 with different intensities. When the pyrolysis temperature was lower than 418℃, the amount of C6H6 evolved in the process of pyrolysis of inertinite concentrated was higher than that of raw coal and vitrinite concentrate. As the temperature rising, the production rate of C6H6 increased. Below 672℃, C6H6 evolution rate of vitrinite concentrate was far greater than the other two samples; the main evolution temperature range of C7H8 was 400℃ to 700℃ for the three samples. The amount of HE and H20 released first increased and then decreased with the temperature increase while more H2 released for pyrolysis of inertinite concentrated and more H20 released for the pyrolysis of vitrinite concentrate.

Preparation and coking properties of coal maceral concentrates

The concentrates with different maceral contents were obtained from Kailuan coking coals with different coal ranks(Ro;ranvarying from 0.88%to 1.73%)by float–sink separation in lab.Then these concentrates were characterized by proximate analysis,ultimate analysis,petrography analysis and coking index determination.The results show that the vitrinite is characterized as nature of lower carbon content,higher hydrogen content,higher volatile matter and stronger caking property compared to inertinite.The relationships between variation rate of volatile matter and maximum volatile matter and coal ranks are identified,and a linear model is developed for fast determination of the maceral contents.Compared to inertinite-rich concentrate,the blending ratio of vitrinite-rich concentrate is increased by 13%,which is considered to be a potential technique based on maceral separation for expanding the coking coal resources.

Influence of microwave treatment under a hydrogen or methane atmosphere on the flotability of the macerals in Shenfu coals

The modification of Shenfu coals by a microwave treatment carried out under a hydrogen or a methane atmosphere, and the subsequent maceral separation by flotation, are described in this paper. The surface contact angle and the Zeta potential of the coal macerals were measured both with and without the treat- ment. The results show that the surface wettability of SFF (Shenfu Fusain) and SFV (Shenfu Vitrain) can be changed by the microwave treatment. An increase in the difference in surface wettability of SFF and SFV causes in a subsequent increase in the enrichment of inertinite and vitrinite. The results of the Zeta potential measurements show that the surface potentials of SFF and SFV are also changed by the treatment.

Explanation for peat-forming environments of coal seam 2 and 9^(-2)based on the maceral composition and aromatic compounds in the Xingtai coalfield,China

Maceral composition and aromatic compounds were determined on columnsamples to study the peat-forming environments of Permian coal seam 2 and Carboniferouscoal seam 9^(-2) from the Xingtai coalfield,China.The macerals were dominated by inertinitein seam 2 and by vitrinite in seam 9^(-2).Three maceral groups were selected as indicatorsof peat-forming environments.Two triangle diagrams were drawn based on the indicatorsto explicate the peat-forming environments of permian seam 2 and Carboniferousseam 9^(-2).The results indicate that the peat of carboniferous seam 9^(-2) formed dominantlyin wet swamps,whereas the peat of Permian seam 2 formed dominantly in dry swampsand open moor environments.

Flotation characteristics of Shenfu coal macerals

The flotation characteristics of Shenfu coal macerals was researched. Taking flotation recovery and enrichment of macerals as the evaluation objects, the influence of the agent dosage, pulp concentration, impeller speed and aeration rate on the separating effect was investigated. And the optimum process conditions of flotation were confirmed. The results show that the agent dosage, pulp concentration, impeller speed and aeration rate have a significant impact on flotation recovery and en- richment of macerals. The float recovery was 73.28% and enrichment ratio of vitrinite was 83.89% when CTAB dosage of 1.0 kg/t, pulp concentration of 100 g/L, impeller speed of 1 700 r/min and aeration rate of 0.25 m3/（m2·min） were used. The tailings yield was 60.30% and enrichment ratio of inertinite was 61.44% when CTAB dosage of 0.5 kg/t, pulp concentration of 100 g/L, impeller speed of I 700 r/min and aeration rate of 0.20 m3/（m2·min） were used.

Compositional and Structural Study of Macerals in Coals and Source Rocks Using SIMS

The authors applied the Secondary Ion Mass Spectrometry (SIMS) technique to the analysis of compositions and structures of vitrinites fusinites, fusinites bitumens and graptolites in the hydrocarbon source rocks with different maturities dscribed their SIMS spectral characteristics and found that different macerals have differnt spectra which, reflected the compositional and structural differences of macerals. Moreover, the change bod of parameter CH2+/CH3+ can be used for the evaluation of thermal evolution regularity of macerals in the hydrocarbon source rocks The study results show that the SIMS technique is a powerful means for microara analysis of macerals in coals and source rocks. It is certain that the study level of macerals can be raised by detailed study of SIMS results of SIMS results of macerals.

Geochemical characteristics of different maceral groups in the Huangxian Coal,China

In order to research how lignite is utilized, two coal samples of seams 2 and 4 were taken from the Huangxian Basin, China. The samples were separated into vitrinite, sporinite, and resinite. Geo-chemical and pyrolysis methods were used to analyse three maceral groups and two seam samples. The results indicate that the resinite and sporinite groups have higher extract yields, S1, S2, HI values, and pyrolysis compounds. These differences may shed light on the usage of the Huangxian lignite. Seam 2 pro- duces more gas and oil than seam 4 does because seam 2 contains more resinite and sporinite macerals.

Carbon monoxide adsorptive capability of low rank coal's maceral

The centrifugal separation with gravity experiment was made for getting every pure macerals like inertinite and vitrinite,and the isothermal adsorption tests of pure mac- eral are carried out at 30,40,50,55,60,65℃,respectively,after analyzing the proximate element and maceral of coal samples,which was aimed to study the CO adsorptive capa- bility of every maceral of low rank coal at difference temperature and pressure.The results show that the adsorption isotherm of CO can be described by Langmuir equation because it belongs to the Type I adsorption isotherm at low temperature(T≤50℃),and the tem- perature effect on coal adsorption is greater than of pressure in lower temperature and pressure area;what's more,the relationship is linear between the coal adsorption quantity of CO and the pressure at high temperature(T>50℃),it can be described by Henry equation(Q=KP),which increases with pressure.Both temperature and pressure has great influence on CO adsorptive capability of low rank coals,especially the temperature's effect is so very complex that the mechanism need to study further.At the same time,the volatile matter,inertinite,oxygen-function groups and negative functional groups are high popu- larly in low rank coal samples,especially,the content of hydroxide(-OH) has great influ- ence on CO adsorption in that the inertinite has stronger effect than vitrinite on adsorptive capability of low rank coal samples,the result is same to the research on CH4 adsorption.

Optimization of Baosteel's digital automatic analysis technique for maceral specification

Baosteel developed a digital automatic analysis technique for maceral specification in 2002. This analysis system combines digital image processing, graphics, databases, expert systems, artificial intelligence and other advanced technologies. After 6 years of application in coke production, the system proved itself successful in coal quality testing and coal blending guidance on maceral. However,during this long process, some inadequacies were found that impacted the precision and accuracy of the analysis. So ,in 2008 Baosteel began to work on improving the coal maceral analysis system. The improvements included the following：further upgrading and enhancing the analysis performance of microscopic images ;extending the gray levels to increase the reflectance measurement accuracy 64 times;changing the focus method and effectively eliminating the interference of halo. In addition, an improved image recognition method was adopted to make the extraction of vitrinite more accurate and a new model of coal constituent algorithm was added which can accurately determine the composition of maceral （exinite, vitrinite,inertinite）. Since these improvements were completed, the system has achieved higher automation, speed and accuracy, collected more information and performed more accurate maceral analysis for coke production. Meanwhile, the improved system has provided a reliable analytical basis for the further study on the relationship between coke quality and coal blending.

Organic petrographic and mineralogical composition of the No. 6 coal seam of the Soutpansberg Coalfield, South Africa: Insights into paleovegetation and depositional environment

This study investigates the paleodepositional conditions of the No.6 Seam of the Madzaringwe Formation in Makhado and Voorburg south area of the Soutpansberg Coalfield(Limpopo Province,South Africa)utilizing organic petrography and inorganic geochemical proxies.The coals are predominantly high-volatile bituminous B-A rank with high ash yields(avg.36.1 wt%),characterized by high-vitrinite(~41.5 vol%),moderate-to-high inertinite(9.8 vol%–33.7 vol%)and low liptinite(~2.3 vol%).The distribution of inertinite varies among different coal horizons(from bottom-lower to middle-upper),suggesting differential oxidation conditions and/or paleofire occurrence.Vitrinite-to-inertinite(V/I)ratio,tissue preservation–gelification index(TPI–GI),and groundwater–vegetation index(GWI–VI)plots,indicate that the peat-forming forest-swamp vegetation accumulated under mesotrophic-to-rheotrophic hydrological conditions.The presence of structured macerals(i.e.,telinite,collotelinite,fusinite,and semifusinite)suggests well-preserved plant tissues,whereas framboidal pyrite and sulphur content(0.24 wt%–2.16 wt%)point to brackish-water influence at the peat stage.The coals contain quartz,kaolinite,siderite,muscovite,dolomite,calcite,and pyrite minerals,most of which were likely sourced from felsic igneous rocks.The Al/(Al+Fe+Mn)and(Fe+Mn)/Ti ratios for the studied samples range between 0.24–0.97 and 0.57–70.10,respectively.The ratios,Al–Fe–Mn plot,and presence of massive botryoidal-type pyrite imply some influence of meteoric waters or fluids from hydrothermal activity post-deposition.Moreover,the chemical index of alteration(CIA:98.25–99.67),chemical index of weathering(CIW:92.04–97.66),and A–CN–K ternary diagram suggest inorganic matter suffered strong chemical weathering,indicating warm paleoclimatic conditions during the coal formation.

Hydrocarbon generation potential of Campano-Maastrichtian to Paleogene shales in the Benin Flank of the Anambra Basin,SW Nigeria

The hydrocarbon generation potential of the Campano-Maastrichtian to Paleogene shales from the Benin Flank(located in SW Nigeria)of the Anambra Basin,has been previously investigated mostly by studying outcrops and by relatively few subsurface data-based studies.Thus,it is expedient undertaking an assessment of the hydrocarbon generation potential of this frontier area from subsurface samples.Campano-Maastrichtian to Paleogene shale samples obtained from Egoli-1 borehole in the Benin Flank of the Anambra Basin are studied by means of HAWK programmed pyrolysis,organic petrography,and mineralogy(XRD),with the aim to explore the petroleum-generating potential and the thermal maturity.The obtained results display a significant variation of the TOC content ranging from very low(<0.5%)to significant(>5%),indicating poor to excellent oil potential based on S_(2)values under the condition,of course,the studied formations reached the oil window.The shales of the Nsukka and Imo Formations display lower petroleum-generating potential than these of the Mamu Formation.All the studied samples are dominated by gas-prone(type III)and inert(type IV)kerogens,with few displaying mixed II/III(oil-and gas-prone).The organic-petrography observations support partly the results of the HAWK programmed pyrolysis,as they reveal an organic-richer Mamu Formation in comparison to the Nsukka and Imo Formations;huminite/vitrinite particles(both indigenous and recycled)along with variable contents of liptinite(mostly alginite and bituminite)and inertinite macerals(mostly inertodetrinite)are hosted in the shales.The latter display a typical composition for fine-grained clastic sediments;mostly kaolinite,illite/montmorillonite,quartz,and subordinately,anatase.In terms of thermal maturity,huminite/vitrinite reflectance data points to immature stage;however,the occurrence of solid bitumens,displaying equivalent vitrinite reflectance values within the oil window,points to an active petroleum system in sequences deeper than the examined ones.

Depositional Model for Peat Swamp and Coal Facies Evolution Using Sedimentology, Coal Macerals, Geochemistry and Sequence Stratigraphy

As one of the most important source rocks and reservoirs of unconventional natural gas, the sedimentary environment and mode of peat swamp（the predecessor of coal seam） is important to the coal seam＇s spatial distribution, material composition, hydrocarbon generation potential, reservoir physical properties, etc. To reveal the depositional characteristics and history of environmental change in a terrestrial basin during a period of peat accumulation, the Middle Jurassic aged #7 coal from Gaoquan in the Qaidam Basin（NW China） was investigated using sedimentology, maceral composition, geochemistry and sequence stratigraphy. Based on identification of the sedimentary shoreline break belt, wave energy depletion point and position of wave base, the peat swamp system can be subdivided into（1） lakeside plain,（2） low energy lakeshore,（3） high energy lakeshore, and（4） shallow lake subfacies. A new method for determining coal facies is proposed based on the combination of environmental parameters including oxidation-reduction levels, energy conditions and the influence of terrigneous sediments. The evolution of the coal seam shows that peat was deposited mainly in the low energy lakeshore and lakeside plain subfacies. Five types of sequence stratigrpahic surface and two types of parasequence were identified. Forced lake regressions and normal lake regressions are attributed as the causes of sequence boundaries. The sequence stratigraphic framework comprises six sequences and corresponding system tracts, and the curve of base-level for each demonstrates a characteristic initial period of slow rising followed by fast rising and then returning to slow rising. A model indicating the relationship among base-level changes, coal facies evolution, and the environmental features in the swamp is proposed that shows the environmental features of the swamp were controlled by both base-level changes and coal facies. Accompanying depositional environment changes from a lakeside plain to lakeshore and shallow lake caused by increasing rate of base-level rise, water paleosalinity, acidity and the percentage of woody plants decrease, and the bog type alters from the low marsh to raised bog.

Experimental study and evaluation on hydrocarbon generation of macerals

Some typical coal and maceral samples are selected for oil and gas-generatingsystematic thermal simulation experiments, Rock-Eval, GC and GC-MS analyses. Results cause productivity curves of extracts and gaseous, light, liquid as well as total hydrocarbon. Effects of macerals and maturation on hydrocarbon productivities and compositions are synthetically discussed. Evaluation indexes and plan on coal-generated oil and gas in bituminous coal rank are suggested according to the data from experiments and analyses.

Laser-induced fluorescence of macerals in relation to its hydrogen richness

On the basis of results from conventional elemental analyses and a unique technique (FAMM? fluorescence alteration of multiple macerals), using a laser fluorescence microprobe, the fluorescence characteristics of various macerals are systematically related to hydrogen content. The amount of fluorescence from inertinite and vitrinite exponentially increases with H/C values. Although liptinite has high fluorescence and high H/C values, the relationship does not follow the same trend as defined for the other maceral groups. Because petroleum yields of a maceral mainly depend upon hydrogen richness, a correlation also exists between fluorescence, and gas to oil ratios from pyrolysis. Because individual organic entities are measured, the laser fluorescence microprobe has the benefit of accommodating heterogeneous organic matter in source rocks and enables determination of oil and gas yields of specific macerals.

THE HYDROCARBON-GENERATING TREND ANALYSIS OF MACERALS IN HYDROCARBON SOURCE ROCKS

The hydrocarbon-generating threshold and pattern of a source rock mainly depend on its constituents of macerals. Different kinds of macerals occurring in a source rock may have variable 'oil window ', especially the 'oil threshold'. In order to recognize the different hydrocarbon generation of macerals, organic petrology may be the only efficient method. In this note, the detailed fluorescence alteration patterns of macerals in the

Differences in geochemistry and hydrocarbon generation of sourcerock samples dominated by telalginite and lamalginite: A case study on the Permian saline lacustrine source rocks in the Jimusaer Sag, NW China

The Middle Permian Lucaogou Formation in Northwestern China mainly contains typical saline lacustrine oil shale.To study the differences in geochemistry and hydrocarbon generation of source-rock samples in Lucaogou Formation in Jimusaer Sag,57 core samples from two boreholes were analyzed herein by performing total organic carbon(TOC)analysis,RockeEval pyrolysis,and gas chromatographicemass spectrometry experiments on saturated hydrocarbons.The kinetics of oil generation were studied using two samples comprising typical maceral components.The results showed that the hydrocarbons produced by telalginite are relatively rich in pristane(Pr),phytane(Ph),b-carotane,high-carbon normal alkanes,and C29 regular steranes.Hydrocarbons produced by lamalginite contain a significantly higher content of C20 tricyclic terpanes(TT),C21TT,C24 tetracyclic terpanes(TeT),C29 norhopane,and C28 regular sterane.Based on the pyrolysis and biomarker compound parameters,telalginite has a higher conversion rate for hydrocarbons than lamalginite in the low-mature to mature stage,which is consistent with their kinetic analysis.Lamalginite source rock displays a much narrower distribution of activation energies than telalginite source rocks.Such narrower activation energy distribution effectively narrows the main stage of hydrocarbon generation.In addition,the activation energy distribution of lamalginite concentrated in the high-value interval,indicating the characteristics of the relatively lagging hydrocarbon generation of lamalginite.

Identification, evolution and geological indications of solid bitumen in shales: A case study of the first member of Cretaceous Qingshankou Formation in Songliao Basin, NE China

On the basis of sorting out current understanding of solid bitumen (SB) in shales and taking organic-rich shales in the first member of the Cretaceous Qingshankou Formation in the Songliao Basin as an example, the definition, classification, occurrence and evolution path of SB are systemtically studied, and the indicative significance of SB reflectance (Rob) on maturity and its influence on the development of reservoir space are discussed and summarized. The results show that the difference of primary maceral types is primarily responsible for the different evolution paths of SB. Most of the pre-oil bitumen is in-situ SB with only a small amount being of migrated SB, while most of the post-oil bitumen and pyrobitumen are migrated SB. From the immature to early oil maturity stage, bituminite, vitrinite, and inertinite can be distinguished from SB based on their optical characteristics under reflected light, and alginite can be differentiated from SB by their fluorescence characteristics. Under scanning electron microscope, in-situ SB and migrated SB can be effectively identified. Rob increases linearly with increasing vitrinite reflectance (Ro), as a result of a decrease of aliphatic structure and the enhancement of aromatization of SB. Within the oil window three types of secondary pores may develop in SB, including modified mineral pores, devolatilization cracks and bubble holes. At a high maturity stage spongy pores may develop in pyrobitumen. Scanning electron microscopy combined with in-situ SEM-Raman spectroscopy can further reveal the structral information of different types of SB, thus providing crucial data for understanding for understanding OM migration paths, dynamics, and distances at micro-scale.