Thermal Simulation Experiments Research Articles

Prediction and Prevention of Cracks in Free-Cutting Stainless Steel Bar Forming

A three high planetary mill is used to produce bismuth-containing stainless-steel bars with high production efficiency. However, due to the influence of bismuth metal properties, the selection of processing parameters must be optimized to avoid the generation of cracking in the bar core. To solve this contradiction and find a suitable processing zone, the thermal simulation experiment of bismuth-containing stainless-steel material was carried out first to determine the constitutive relationship of the material. Three-roll planetary rolling experiments were carried out to determine the crack-producing region. Based on the Brozzo ductile fracture criterion, the fracture threshold of bismuth-containing austenitic stainless-steel bars in three-roll planetary rolling was determined by the finite element (FE) simulation. Five key process parameters were selected, with five factors and four levels of the orthogonal test designed. Through FE simulations, the possibility of cracking of stainless-steel bars with bismuth austenites in different technologic conditions was judged, and a set of optimal technologic parameters was obtained. Based on range analysis, the influence of various process parameters on bar cracking was discussed. Then, based on the dynamic material model and Murty criterion, the processing map of free-cutting austenitic stainless containing bismuth was established. It was found that the optimum process parameters were consistent with the processable range of the hot-working chart. Finally, the field rolling was carried out with the optimum process parameters, showing that there was no crack in the bar.

Characterization of a Lacustrine Shale Reservoir and the Evolution of its Nanopores: A Case Study of the Upper Cretaceous Qingshankou Formation in the Songliao Basin, Northeastern China

AbstractThe Songliao Basin is one of the most important petroliferous basins in northern China. With a recent gradual decline in conventional oil production in the basin, the exploration and development of unconventional resources are becoming increasingly urgent. The Qingshankou Formation consists of typical Upper Cretaceous continental strata, and represents a promising and practical replacement resource for shale oil in the Songliao Basin. Previous studies have shown that low‐mature to mature Qingshankou shale mainly preserves type I and type II1 organic matter, with relatively high total organic carbon (TOC) content. It is estimated that there is a great potential to explore for shale oil resources in the Qingshankou Formation in this basin. However, not enough systematic research has been conducted on pore characteristics and their main controlling factors in this lacustrine shale reservoir. In this study, 19 Qingshankou shales from two wells drilled in the study area were tested and analyzed for mineral composition, pore distribution and feature evolution using X‐ray diffraction (XRD), scanning electron microscopy (SEM), low‐pressure nitrogen gas adsorption (N2‐GA), and thermal simulation experiments. The XRD results show that clay, quartz, and feldspar are the dominant mineral constituents of Qingshankou shale. The clay minerals are mostly illite/smectite mixed layers with a mean content of 83.5%, followed by illite, chlorite, and kaolinite. There are abundant deposits of clay‐rich shale in the Qingshankou Formation in the study area, within which many mineral and organic matter pores were observed using SEM. Mineral pores contribute the most to shale porosity; specifically, clay mineral pores and carbonate pores comprise most of the mineral pores in the shale. Among the three types of organic matter pores, type B is more dominant the other two. Pores with diameters greater than 10 nm supply the main pore volume; most are half‐open slits and wedge‐shaped pores. The total pore volume had no obvious linear relationship with TOC content, but had some degree of positive correlation with the content of quartz + feldspar and clay minerals respectively. However, it was negatively correlated with carbonate mineral content. The specific surface area of the pores is negatively related to TOC content, average pore diameter, and carbonate mineral content. Moreover, it had a somewhat positive correlation with clay mineral content and no clear linear relationship with the content of quartz + feldspar. With increases in maturity, there was also an increase in the number of carbonate mineral dissolution pores and organic matter pores, average pore diameter, and pore volume, whereas there was a decrease in specific surface area of the pores. Generally, the Qingshankou shale is at a low‐mature to mature stage with a TOC content of more than 1.0%, and could be as thick as 250 m in the study area. Pores with diameters of more than 10 nm are well‐developed in the shale. This research illustrates that there are favorable conditions for shale oil occurrence and enrichment in the Qingshankou shale in the study area.

Experimental simulation study on the influence of diagenetic water medium on sedimentary n-alkanes and their respective hydrogen isotopes

In order to understand the influence of the diagenetic water medium on the hydrogen isotope of sedimentary n-alkanes, thermal simulation experiments were carried out involving the initial peat under the addition of alkaline saltwater, acidic freshwater and peat alone condition. The generated n-alkanes were analyzed in terms of molecule composition and hydrogen isotopic composition of individual n-alkanes. The results show that the addition of water had a significant effect on n-alkane nC21−/nC22+ ratio, ACL value and Pr/Ph ratio. The n-alkanes display significant heavier hydrogen isotopic composition from the alkaline saltwater added experiments, but obvious lighter hydrogen isotopic composition from the acidic freshwater added experiments. The difference of the average δD value of n-alkanes between the saltwater and freshwater experiments ranged from 6‰ to 73‰, and maximum difference occurred from the experiments of 350 °C. The exchange of inorganic hydrogen in water and organic hydrogen was more intensive in the acidic freshwater experiments than that in the alkaline saltwater experiments. The average δD value of n-alkanes generated under the participation of saltwater and freshwater media appear to be higher heavier along with the increase in experimental temperature. Also, the average δD value of n-alkanes generated from the saltwater added experiments was always higher than that from the freshwater added experiments. The correlations among the δD composition of n-alkanes generated under different condition were established. These results provide information to understand of the genesis of sedimentary n-alkanes formed under the participation of diverse diagenetic water media at various stages of maturity.

Improvement of Longitudinal Performance Uniformity of Hot-Rolled Coils for Cold-Rolled DP980 Steel

Cold-rolled DP980 steel is widely used in the automobile industry. Hot-rolled coil is the raw material of cold-rolled DP980 steel, the head and tail parts of which are usually obviously stronger than the body part. The objective of this study is to improve the longitudinal performance uniformity of hot-rolled coils. The material properties of this steel, such as the dynamic continuous cooling transformation, the influence of the cooling mode before coiling, the cooling rate during coil cooling on the microstructure, and mechanical properties of cold-rolled DP980 steel were investigated through thermal simulation experiments and hot rolling experiments. Meanwhile, the temperature field of hot-rolled coil was analyzed using ABAQUS software, which was used to survey the cause of the longitudinal performance fluctuations of hot-rolled coils, combined with an investigation of the aforementioned material properties. The results illustrate that the average cooling rate of the head and tail parts are higher than that of the body part during coil cooling, which causes the longitudinal performance fluctuation of hot-rolled coils. Based on the temperature field of hot-rolled coil, obtained by FEM, the parameters of the U-shaped cooling process were optimized and used in industrial applications.

An Investigation into the Dynamic Recrystallization (DRX) Behavior and Processing Map of 33Cr23Ni8Mn3N Based on an Artificial Neural Network (ANN).

Based on an 33Cr23Ni8Mn3N thermal simulation experiment, the application of an artificial neural network (ANN) in thermomechanical processing was studied. Based on the experimental data, a microstructure evolution model and constitutive equation of 33Cr23Ni8Mn3N heat-resistant steel were established. Stress, dynamic recrystallization (DRX) fraction, and DRX grain size were predicted. These models were evaluated by a variety of statistical indicators to determine that these models would work well if applied in predicting microstructure evolution and that they have high precision. Then, based on the weight of the ANN model, the sensitivity of the input parameters was analyzed to achieve an optimized ANN model. Based on the most widely used sensitivity analysis (SA) method (the Garson method), the input parameters were analyzed. The results show that the most important factor for the microstructure of 33Cr23Ni8Mn3N is the strain rate (). For the control of the microstructure, the control of the is preferred. ANN was applied to the development of processing map. The feasibility of the ANN processing map on austenitic heat-resistant steel was verified by experiments. The results show that the ANN processing map is basically consistent with processing map based on experimental data. The trained ANN model was implanted into finite element simulation software and tested. The test results show that the ANN model can accurately expand the data volume to achieve high precision simulation results.

Generation and expulsion process of the Chang 7 oil shale in the Ordos Basin based on temperature-based semi-open pyrolysis: Implications for in-situ conversion process

There is a substantial amount of oil shale resources in the seventh member of the Triassic Yanchang Formation (abbreviated as Chang 7) in the Ordos Basin, and its geological and geochemical characteristics are highly suitable for in-situ conversion process (ICP). A comprehensive characterization of its hydrocarbon generation, expulsion and retention features will help determine the optimum conditions for future field tests. However, typical thermal simulation experiments based on either open-system or closed-system are not applicable to provide data to construct the models. Therefore, in this study, eight parallel thermal simulation experiments, which were based on the newly designed temperature-based semi-open pyrolysis experiments were performed on the Chang 7 oil shale. The yields (including cumulative yields and net incremental yields) and compositional characteristics of the expelled oil, expelled gas, and retained oil were analyzed. Results show that the hydrocarbon expulsion has a coupling relationship with hydrocarbon generation that can be divided into four stages: (1) Slow hydrocarbon generation stage (300–320 °C, 0.53–0.55 %Ro). Minimal amounts of oil and gas are generated in this stage. The hydrocarbon expulsion efficiency increases rapidly. (2) Quick oil-generation stage (320–380 °C, 0.55–1.09 %Ro). The fast cracking of kerogen and thermal bitumen generates a large amount of oil. The hydrocarbon expulsion efficiency remains relatively stable. (3) The secondary oil cracking and quick gas-generation stage (380–420 °C, 1.09–1.66 %Ro). The oil yield begins to decrease after reaching its maximum and a large amount of hydrocarbon gas is generated. The oil generation capability of kerogen is basically exhausted. The hydrocarbon expulsion efficiency and gas/oil ratio increase rapidly at this stage. (4) The heavy hydrocarbon gas cracking stage (after 420 °C, 1.66 %Ro). The oil yield continues to decline, accompanied by the onset decline in the gas yield (except methane). At this time, the hydrocarbon expulsion efficiency continues to increase but at a rather low speed. Under the experimental conditions in this study, 1.24–1.66% Ro is considered a favorable thermal maturity interval, in which maximum oil production with relatively light components can be obtained and the hydrocarbon gas is abundant.

Numerical and Experimental Analysis of Rotating Backward Extrusion as a New SPD Process

Rotating backward extrusion (RBE) as a new severe plastic deformation technique is a continuous process to produce cylindrical tubes with fine grains and superior properties. In this study, the RBE process with an open punch was applied to the AZ80 alloy at 653 K, and the deformation mechanisms and the microstructure evolution were examined by the finite element method (FEM) and thermal simulation experiment. The results showed that the effective strain of the RBE process was higher than that of the conventional backward extrusion (CBE) process, and the strain increased with revolutions increasing. The strain improvement of the RBE process was related to the large cumulative plastic deformation imposed by the continuous rotation of the open punch. Furthermore, the extrusion load was reduced significantly in the RBE process comparing with the CBE process, due to the change of friction stress and stress state of the materials. And the maximum load reduction of the FEM and experiment was 47.33% and 31.6%, respectively. The average grain size of the RBE sample could be reduced by up to 90% in the region A at 30 N compared with the CBE sample. The maximum increase in microhardness of the RBE sample relative to the CBE sample was 23% at 30 N in the region A. Therefore, the grain refinement and mechanical properties of the materials can be substantially improved by the RBE process.

低熟富有机质泥页岩热模拟排出油饱和烃地球化学特征

低熟富有机质泥页岩热模拟排出油饱和烃地球化学特征

Thermal Simulation and Sonoporation Experiment Based on a Focused Ultrasonic System

This paper aims at analyzing ultrasonic thermal effect and sonoporation based on a focused ultrasonic experiment system. The numerical analysis, about cavitaion conditions and ultrasonic thermal effect using the coupling model of pressure acoustic and bioheat transfer, were given, in which the temperature rise trend is identical to the conclusion in the literature [2]. According to the simulation analysis of ultrasonic thermal effect, temperature rise is approximately 18.5K near the focal spot with Ultrasonic radiation for 60s, which had little effect on 293T cell viability. In the acoustic chemical experiment, 293T cell viability is about 85% at 60s of the ultrasound irradiation, which was observed by 200× fluorescence microscope. The cell states of survival and abnormal was observed and analyzed in the sonoporation experiment at 60s of ultrasonic time.

Geochemical Characteristics of Released Organic Matters by Acid Decomposition of Hydrocarbon Source Rocks from Different Sedimentary Basins

It has been acknowledged that carbonate was identified as the source rocks of a series of oil-gas fields worldwide. For evaluating the carbonate source rocks, total organic carbon (TOC) contents act as an important indicator. However, the acid solution, which has been generated during conventional TOC measurements, contain organic matters. Hence, the released organic matters in acid solution during carbonate decomposition may lead to underestimate the hydorcarbon generation potential. In this study, rock-eval pyrolysis technique was applied to bulk rock and residue after acid treatment. Meanwhile, the organic matters in acid solution were measured by Gas Chromatography-Mass Spectrometer (GC-MS) to investigate the geochemical characteristics. In addition, the hydrocarbon generation and alteration of TOC contents of released organic matters by acid treatment were studied by hydrous pyrolysis experiments. The results show that the acid solution contains organic compounds, including n-alkanes, saturated fatty acids and fatty acid methyl esters. Meanwhile, total organic carbon (TOC) contents and hydrocarbon generation potential (S1+S2) significantly decrease for bulk rocks after acid treatment in low maturity samples. Moreover, organic CO2 (S3) decreased after treating of acid, revealing that acidolysis process can affect and release organic matters containing oxygen-bearing functional groups. The S1, S2, S3, and TOC loss are positive correlation with the proportion of rock loss during acidolysis, indicating that the organic matters in acid solution are associated with carbonate minerals. The organic fractions may exist as adsorption state on the surface of carbonate minerals and (or) exist as organic acid salts. Moreover, the thermal simulation experiments reveal that the organic matter in acid solution, which is not recovered by the conventional measurement approach, could contribute to hydrocarbon generation.

Study on Microstructure Control of X80 Pipeline Steel and Precipitation of Nb Element

In this paper, X80 grade test steel was trial-produced in the laboratory, the mechanical properties, microstructure and precipitate morphology of the trial-produced test steel were analyzed and studied, and the precipitation law of Nb element in high-grade pipeline steel was studied by thermal simulation method. The results show that the X80 grade test steel has excellent mechanical properties, yield strength of 660 MPa, tensile strength of 720MPa and yield ratio of 0.91. The impact energy is greater than 295 under -20°C test conditions and the cross-section rate of the DWTT fiber reached 90% under -15°C test conditions, and the test results completely meet the API.5L standard requirements. By the thermal simulation experiment, it is found that the precipitation process of Nb particles in the test steel is the nucleation growth process of controlled by diffusion. The tip temperature of the PTT curve is about 900°C, and the Nb element in the test steel is found at 810°C by solid solubility calculation can be completely precipitated.

Engineering Design of an Active-Passive Combined Thermal Control Technology for an Aerial Optoelectronic Platform.

In order to ensure the imaging performance of the aerial optoelectronic platform system in low temperature environment, an active-passive combined thermal control technology was studied. A thermal control finite element model of the aerial optoelectronic platform was established. Additionally, thermal control simulation analysis and experiments under extreme conditions were carried out respectively. The simulation and experimental results showed that the temperature level of the primary mirror is improved above 25 °C by the proposed thermal control technology effectively, meanwhile the temperature gradient of the primary and secondary mirrors are less than 5 °C. The successful implementation of this active-passive combined thermal control technology provides a technical support for the precision thermal control of aerial optoelectronic platforms.

Study of the closure temperature of (U-Th)/He in detrital zircon obtained from natural evolution samples

Zircon (U-Th)/He thermochronometry was used as an effective indicator to study the thermal history of deep sedimentary basins with high temperatures. Zircon He ages and closure temperatures are very important parameters. In this paper, detrital zircon He closure temperature was studied by establishing the evolutionary pattern between zircon He ages and burial depth of borehole samples obtained from the Cenozoic strata in the Bohai Bay and Tarim basins, which have different thermal settings. The results show that the zircon He closure temperature of natural evolution samples is 200°C, which is higher than the temperature obtained from thermal simulation experiments (183°C). The temperature range of 140–200°C corresponds to the zircon helium partial retention zone. By properly understanding zircon He closure temperatures, zircon (U-Th)/He thermochronometry can provide a correct explanation of the He ages, and significant guidance in the study of the evolution of source rocks and the process of hydrocarbon accumulation in deep sedimentary basins.

Continuous Cooling Transformation Diagram, Microstructures, and Properties of the Simulated Coarse-Grain Heat-Affected Zone in a Low-Carbon Bainite E550 Steel

In order to provide important guidance for controlling and obtaining the optimal microstructures and mechanical properties of a welded joint, the continuous cooling transformation diagram of a new low-carbon Nb-microalloyed bainite E550 steel in a simulated coarse-grain heat-affected zone (CGHAZ) has been constructed by thermal dilatation method in this paper. The welding thermal simulation experiments were conducted on a Gleeble-3800 thermo-mechanical simulator. The corresponding microstructure was observed by a LEICA DM2700M. The Vickers hardness (HV) and the impact toughness at −40 °C were measured according to the ASTM E384 standard and the ASTM E2298 standard, respectively. The experimental results may indicate that the intermediate temperature phase transformation of the whole bainite can occur in a wide range of cooling rates of 2–20 °C/s. In the scope of cooling rates 2–20 °C/s, the microstructure of the heat-affected zone (HAZ) mainly consists of lath bainite and granular bainite. Moreover, the proportion of lath bainite increased and granular bainite decreased as the cooling rate increasing. There is a spot of lath martensite in the microstructure of HAZ when the cooling rate is above 20 °C/s. The Vickers hardness increases gradually with the increasing of the cooling rate, and the maximum hardness is 323 HV10. When the cooling time from 800 °C to 500 °C (t8/5) is 5–15 s, it presents excellent −40 °C impact toughness (273–286 J) of the CGHAZ beyond the base material (163 J).

Pore characteristics and evolution of Wufeng–Longmaxi Fms shale gas reservoirs in the basin-margin transition zone of SE Chongqing

At present, researches on the pore evolution of shale reservoir and its evolution mechanism are still at such a groping stage that a consensus has not yet reached. Based on core analysis and thermal simulation experiments, the pore types, pore structures and pore-size change rules of shale gas reservoirs of Upper Ordovician Wufeng–Lower Silurian Longmaxi Fms in the southeastern (SE) Sichuan Basin and its basin-margin transition zone (hereinafter referred to as the basin-margin transition zone of SE Chongqing) were studied by means of argon ion polishing–scanning electron microscopy (SEM) and atomic force microscopy. Then, the evolution characteristics of organic pores were discussed, and the influence of associated minerals on pore evolution was analyzed. Finally, a pore evolution model for the shale gas reservoirs in this area was established. And the following research results were obtained. First, three types of reservoir spaces are mainly developed in the high-quality shale reservoirs of Wufeng–Longmaxi Fms in this area, including fracture, inorganic pore and organic pore. And the organic pores provide the primary reservoir space of shale gas, which can be divided into four categories, i.e., amorphous kerogen pores, structured kerogen pores, asphaltene pores and paleontology fossil pores. Second, organic contracted fractures are related to the contraction of organic matters, first appearing on one side of the organic matters and then becomes wider and wider with the increase of temperatures. Third, organic pores are mostly the “spongy” pores distributed densely inside the organic matters. When Ro is in the range of 1.56–3.50%, macropores and mesopores are dominant. And when Ro exceeds 3.50%, macropores decrease while mesopores and micropores increase. Fourth, the types of organic matters and the content of associated minerals (e.g. clay minerals, siliceous particles and pyrite) play an important role in the development of pores. In conclusion, the pore evolution law of Wufeng–Longmaxi shale in the basin-margin transition zone of SE Chongqing is that with the increase of burial depth, inorganic porosity decreases significantly, organic porosity increases first and then decreases, and the total porosity shows a change trend of decreasing first, then increasing and finally decreasing continuously.

Pore evolution characteristics of Chinese marine shale in the thermal simulation experiment and the enlightenment for gas shale evaluation in South China

Although there are many similarities between the shale of Cambrian Qiongzhusi Formation and Ordovician Wufeng Formation–Silurian Longmaxi Formation in South China, including total organic carbon content (TOC) and thickness, the drilling results of shale gas exploration are very different. One of the reasons is the difference of the nano-pores number developed in organic matter between them. In order to reveal the causes, the black shale of Upper Proterozoic Xiamaling Formation in North China, which is similar to the marine source rock in Sichuan basin, was selected for the thermal simulation experiment, and the pore size and volume of the samples before and after the experiment were acquired by scanning electron microscopy (SEM) and nitrogen adsorption isotherm measurement. Through the SEM photographs, we found that the sizes of the organic pores in algae, dispersed organic matter and organic matter associated with clay minerals get bigger with the increasing maturity. The total pore volume, micro-pore volume and meso-pore volume of the shale acquired by nitrogen adsorption isotherm measurement increase with the increasing maturity, too. However, under the overburden pressure, micro-pore volume decreases at high maturity stage, indicating the pores in organic matter might be compressed. It is considered that the pore volume in organic matter of the shale of Qiongzhusi Formation might be compacted under greater confining pressure, which may be the reason why the pore structures of the two sets of marine shale in South China are different.

Determination of critical parameters for evaluating coal measure shale gas in China

Coal measure shale is one of the most abundant types of marine-continental shales in China. Two sets of typical coal measure shales in China are developed in the Shanxi Formation (Ordos Basin) and in the Longtan Formation (Guizhou Province). In this study, thermal simulation, rock pyrolysis, and X-ray diffraction experiments were used to analyze four coal measure shale samples collected from typical areas of China. Based on the study of hydrocarbon generation process of the samples, the lower limits of thermal maturity (Ro) of favorable and target areas for coal measure shale were ∼1.8% and 2.5%, respectively. The threshold Ro value of oil generation in coal measure shale was preliminarily inferred to be 0.6%. The gaseous hydrocarbon production per unit of S1+S2, after the gas generation threshold, was linearly and positively correlated with Ro. The lower limits of total organic carbon (TOC), corresponding to the favorable and target areas, were ∼2.45 wt% and 2.84 wt%, respectively. Combined with X-ray diffraction experiments, the diagenetic stage and the hydrocarbon generation model of coal measure shale were established and could be divided into four evolutionary stages. The results of this study have direct scientific and practical significance for the evaluation of gas content and selection of areas in China for the extraction of coal measure shale.

Geochemical differences of pyrolysis gas of various coal-bearing source rocks and its application in the Sulige gas field, Ordos Basin, China

In order to study the gas generation process of different coaly source rocks, thermal simulation experiments were performed on coal, dark mudstone, and carbonaceous mudstone. Additionally, a series of geochemical analysis including chemical composition, carbon and hydrocarbon isotope composition, as well as light hydrocarbon analysis on thermal simulation gas were also carried out in this study. It revealed that coal has the highest gas production rate; in addition, it yields a large amount of CO2 gas in the early stage of the simulation experiment. The carbon and hydrocarbon isotope of the coal thermal simulation gas is slightly heavier than that of coaly mudstone and carbon mudstone gas. Prior to reaching 500 °C, the carbon and hydrogen isotopes of these three kinds of gas became lighter and higher with the increase of temperature, but after 500 °C, they became lighter all throughout. Carbon isotope series reversal is observed in this process. The coal thermal simulation gas has the highest content of benzene, toluene, and 2,3-methylpentane. This study specified three highlights on the Sulige gas field: (1) CO2, formed in the early stage of hydrocarbon generation, may have a direct relationship with the reservoir densification in the Sulige gas field. (2) According to the analysis of light hydrocarbon, coal should be the dominant contributor to the accumulation of the Sulige natural gas. However, the contribution of coaly mudstone and carbon mudstone should not be ignored.

Compositional Characterization of Expelled and Residual Oils in the Source Rocks from Oil Generation-Expulsion Thermal Simulation Experiments.

Petroleum generation–expulsion thermal simulation experiments on a low-maturity type I source rock were carried out. The composition of hydrocarbons and heteroatom-containing compounds in both expelled and residual oils was characterized by electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry and gas chromatography-mass spectrometry. A thorough analysis of fractionation effects was presented between expelled and residual oils. The oil composition strongly depended on the pyrolysis temperature. A significant difference in the molecular composition was found between expelled and residual oils at various pyrolysis temperatures. The difference in maturity for expelled and residual oils could be revealed clearly by the difference in the molecular composition of heteroatom-containing compounds. Carboxylic acids in the residual oil cracked quickly with the pyrolysis temperature above 350 °C (% Ro = 1.0) but part of them would survive if they were expelled out of the source rock timely. The variations between the relative abundance of oxygen compounds and nitrogen compounds indicated that the thermostability of oxygen-containing nitrogen compounds was lower than that of neutral nitrogen compounds. The variation trends in double bond equivalents and carbon number distributions of O1, O2, and N1 class species were similar. The aromaticity of heteroatom-containing polar species increased with maturity.

Organic geochemical characteristics and hydrocarbon generation simulation of shallow sediments in Shaobo Lake, Eastern China

We selected the two Holocene shallow surface sediments (depths of 1.42–1.48 and 1.56–1.62 m) of Shaobo Lake in Yangzhou City, Jiangsu Province, China, to analyze the geochemical characteristics and hydrocarbon generation ability of organic matter (OM) from its raw state to the formation of kerogen. We have used the Rock-Eval (RE) VI, low-temperature hydrous pyrolysis, and macerals identified under microscopy to test the whole-rock samples, as well as gas chromatography-mass spectrometry and gas chromatography analysis of the pyrolysis oil and pyrolysis gas. The results indicate that the surface sediments had poor to fair gas-prone hydrocarbon generation potential and that the type of insoluble OM was III-IV. The macerals were dominantly vitrinite, followed by sapropelic amorphogen. Bulk geochemistry data and biomarker compositions indicated that the studied samples deposited in a lacustrine environment with suboxic to anoxic conditions and OM of mixed plankton, bacterial, and land plant origin. RE data and the biomarker index suggested that unheated and thermally simulated samples were from immaturity to just entering the maturity stage. Under the thermal simulation conditions of 250°C–450°C, a peak of pyrolysis oil appeared at 300°C, and the yield increased slowly after 350°C. At 300°C, the hydrocarbon gas (C1–C5) began to produce. As the simulated temperature increased, the yield (in volume) of the hydrocarbon gas increased exponentially and the methane content was also gradually enriched. In general, thermal simulation experiments indicated that the OM could generate slight hydrocarbon from the death of living organisms to early diagenesis.