Rate Of Hydrocarbon Generation Research Articles

Assessment of the oil and gas potential of the eastern edge of the Northern Ustyurt using new geophysical data

Purpose. Detailed substantiation of the geological structure of the eastern edge of the Northern Ustyurt, clarification of modern geological and geophysical data, as well as highlighting the mainstages of evaluating the results of exploration work to confirm the oil and gas potential and subsequent exploitation of the fields. Methodology. The authors used the following scientific methods: generalization – to systematize scientific provisions; analogy and comparison – to characterize deflection in different periods; analysis and synthesis – to substantiate geological and geophysical data; algorithmmization – to determine conceptual provisions regarding the assessment of the oil and gas bearing capacity of the trough. Findings. In order to achieve the goals, the indicators of oil and gas capacity in the areas of the eastern side of the Northern Ustyurt of different geological ages were substantiated. The geological and geophysical features of the basin dating back to 2010 compared to modern refinement of geological data were characterized. The productive and unproductive structures of the eastern side of the Northern Ustyurt are characterized, taking into account the showing of oil and gas based on deposits of different geological ages. The importance of conducting geological exploration and creating corresponding cartographic materials is justified, followed by the design of predictive graphical models, geological sections, and a detailed plan of the territory. Originality. The influence of high hydro carbon generation rates on the further identification of “oil windows” has been substantiated for the first time. The hierarchical levels of predicting the oil and gas content of the trough are identified. The necessity of improving the mechanisms for assessing oil and gas content is substantiated. Practical value. The substantiation of the features of the assessment of the oil and gas content of the of the eastern edge of the Northern Ustyurt, which should be based on forecasting promising areas of prospecting, is the key to distinguishing between productive and unproductive objects, determining their real scale and directing investment flow precisely to promising areas with minimal environmental and economic losses.

The implication of kinetics characteristics of modern organisms for the hydrocarbon generation evolution of organic matter components in the lacustrine source rocks: A case study of the Dongying Formation from the Bozhong Sag, Bohai Bay Basin

The hydrocarbon generation evolution characteristics of lacustrine source rocks are crucial for understanding hydrocarbon resources. In this research, we focus on the mudstone found in the third member of the Paleogene Dongying Formation (E3d3) within the Bozhong Sag of the Bohai Bay Basin as a case study. An analysis of the discrepancy in geochemical characteristics and kinetic parameters was carried out by utilizing the modern organisms (pine pollen and benthic algae) analogies to the organic matter (OM) components (Pinaceae sporopollen and benthic algae amorphous). Furthermore, the bulk hydrocarbon evolution of the Dongying Formation mudstones was further discussed in combination with a water-added sealing thermal simulation experiment and basin simulation. Our findings indicate that the pine pollen and benthic algae have higher OM abundance compared to the E3d3 mudstones, and their OM types are both Ⅱ1-Ⅱ2, which possess excellent potential for oil generation. In contrast, the E3d3 mudstones are predominantly in the low mature to mature thermal evolution stage. When we compare hydrocarbon generation rates and transformation ratios using Rock-Eval pyrolysis, it becomes evident that modern organisms are more prone to generate large amounts of hydrocarbons even at a low mature stage. The kinetic parameters of pine pollen are notably higher compared to those of benthic algae and the E3d3 mudstone samples. In parallel first-order reactions, the activation energy obtained by the single-frequency factor model (SFFP model) displays a narrow distribution range, while the activation energy distribution range of the multi-frequency factor model (MFFP model) is broader. The MFFP model focuses more on the variations of hydrocarbon kinetic parameters throughout the entire process, which is more in conformity with the actual geological process. The enclosed thermal simulation experiment and basin simulation analysis unveil the presence of two distinct phases of hydrocarbon generation within the Dongying Formation. Furthermore, it becomes evident that abundant benthic algae and Pinaceae sporopollen components play vital roles in both of these phases. In conclusion, the method of applying modern organisms to analogize the hydrocarbon generation evolution characteristics of the parent components of lacustrine source rocks seems feasible. Meanwhile, the Dongying Formation in the Bozhong Sag also possesses broad exploration prospects for hydrocarbon resources.

How did submarine volcanic eruptions interact with organic matter to favour hydrocarbon generation in the Bohai Bay Basin, China?

ABSTRACT Based on the geological and geochemical analysis of volcanic rock and their surrounding rocks, combined with palaeontological data and hydrocarbon generation thermal simulation experiments, the mechanism of the impact of volcanic eruptions on the formation of organic matter and hydrocarbon generation in the Dongying Depression is investigated. According to the results, underwater volcanic eruptions play a significant role in promoting biological eruptions and water stratification by introducing heat, minerals, and metal elements. The formation of the basalt source rock symbiotic association went through three evolutionary stages, which were underwater eruption, late eruption, and normal sedimentation. These stages have influenced the generation of hydrocarbons from organic matter in the following ways: (1) The organic acid released from the source rock dissolves the adjacent basalt, and the transitional metal elements in the basalt become activated and enter the source rock, which catalyses the hydrocarbon generation from the source rock. (2) Alteration of olivine in basalt releases hydrogen, improving hydrocarbon generation efficiency of source rock. (3) The existence of a large number of carbonates improves the hydrocarbon generation rate and efficiency of source rocks and reduces the hydrocarbon generation threshold of source rocks.

Fluid Charging and Paleo‐pressure Evolution in the Ledong Slope Zone of the Yinggehai Basin, South China Sea

AbstractLarge numbers of gas reservoirs have been discovered in overpressure basins. Fluid charging has a close relationship with paleo‐pressure evolution, affecting the migration of gas reservoirs. To study fluid charging and the related pressure system, we analyzed burial histories and fluid inclusion (PVTx) simulations and conducted basin modeling of the Ledong Slope Zone in the Yinggehai Basin as an example. On the basis of fluid‐inclusion assemblages (FIAs), homogenization temperature (Th), final melting temperature (Tm, ice) and Raman spectroscopy in fluid inclusions, there are three stages of fluid charging: during the first and second stage, methane‐dominated fluid was charged at 2.2–1.7 Ma and 1.7–0.9 Ma, respectively. In the third stage, CO2‐rich hydrothermal fluid was charged since 0.9 Ma. It could be concluded from the well‐logging data that the disequilibrium compaction in the Yinggehai Fm., along with the fluid expansion and clay diagenesis in the Huangliu and Meishan formations, resulted in the overpressure in the Ledong slope zone. The evolution of paleo‐pressure was affected by the sedimentation rate of the Yinggehai Fm., as well as the hydrocarbon generation rate. Additionally, the Ledong Slope Zone is less affected by diapir activity than the nearby diapir area. Based on fluid inclusions, paleo‐pressure, basin modeling and geological background, the gas migration history of the Ledong Slope Zone can be divided into four stages: in the first stage, excess pressure was formed around 5 Ma; from 2.2 to 1.7 Ma, there was a reduction in the charging of hydrocarbon fluid and steadily increasing excess pressure; during the 1.7–0.9 Ma period a large amount of hydrocarbon was generated, excess pressure increasing significantly and hydraulic fractures forming in mudstones, With gas reservoirs developing in structural highs; since 0.9 Ma, CO2‐rich hydrothermal fluid accumulated in reservoirs adjacent to faults and the pressure coefficient remained stable. The research results are helpful in the study of fluid migration and accumulation mechanisms in overpressure basins.

Hydrocarbon accumulation model influenced by “three elements (source-storage-preservation)” in lacustrine shale reservoir-A case study of Chang 7 shale in Yan’an area, Ordos Basin

The organic-rich shales of the Chang 7 Member in the Yan’an Formation of the Yan’an area, Ordos Basin is a hot spot for lacustrine shale gas exploration. In this paper, taking the Chang 7 Member shale in the Yan’an area as an example, the main controlling factors of lacustrine shale gas accumulation and the prediction of “sweet spots” are systematically carried out. The results show that the Yanchang Formation shale has the complete gas generating conditions. Shale gas accumulation requires three necessary accumulation elements, namely gas source, reservoir and good preservation conditions. The dynamic hydrocarbon generation process of the Chang 7 shale reservoirs is established according to the thermal simulation experiments of hydrocarbon generation, and the mechanism of catalytic degradation and gas generation in the Chang 7 Member under the background of low thermal evolution degree is revealed. The enriched authigenic pyrite can catalyze the hydrocarbon generation of organic matter with low activation energy, thereby increasing the hydrocarbon generation rates in the low-mature-mature stage. Different types of pores at different scales (2–100 nm) form a multi-scale complex pore network. Free gas and dissolved gas are enriched in laminar micro-scale pores, and adsorbed gas is enriched in nano-scale pores of thick shales, and silty laminates can improve the physical properties of the reservoir. This is because the laminar structure has better hydrocarbon generation conditions and is favorable for the migration of oil and gas molecules. The thickness of the lacustrine shale in the Chang 7 Member is between 40 and 120 m, which has exceeded the effective hydrocarbon expulsion thickness limit (8–12 m). At the end of the Early Cretaceous, the excess pressure of the Chang 7 shale was above 3 MPa. At present, horizontal wells with a daily gas production of more than 50,000 cubic meters are distributed in areas with high excess pressures during the maximum burial depth.

Differences and origins of hydrocarbon generation characteristics between mudstone and shale in the Seventh Member of the Yanchang Formation, Ordos Basin, China

Organic-rich black shale and dark-grey mudstone are widespread in the Seventh Member of the Yanchang Formation, Ordos Basin. There are obviously differences in geochemical characteristics and hydrocarbon generation potential between black shale and dark-grey mudstone. Based on the detailed organic geochemical examination, this paper reveals the differences in hydrocarbon generation processes and characteristics (activation energy and conversion rate of hydrocarbon generation) between dark-grey mudstone and black shale and the causes for the differences. Black shale is characterized by moderate to very high total organic carbon (TOC) contents (5.08%–39.39%) and its kerogen type belongs to type II1 and type I. Dark-grey mudstone has a characteristic of low to moderate TOC contents (0.64%–7.35%) and its kerogen types are mainly composed of type II2 and type II1. The hydrocarbon generation activation energy of black shale mainly oscillates around 250–310 KJ/mol, and the corresponding hydrocarbon generation threshold is high (the simulated temperature is 400 °C). The process of hydrocarbon generation is characterized by fast conversion rate and short cycle. By contrast, the hydrocarbon generation activation energy of dark-grey mudstone has a wide range (170–360 KJ/mol), and the corresponding hydrocarbon generation threshold is low (the simulated temperature is 230 °C). The process of hydrocarbon generation is characterized by slow conversion rate and long cycle. The difference of hydrocarbon generation process and characteristics between black shale and dark-grey mudstone is mainly affected by macerals composition and organic matter source. The organic matter of black shale mainly originated from algae, and its macerals was mainly composed of alginite. The organic matter of dark-grey mudstone mainly originated from the mixture of algae and terrestrial higher plants (conifers), and its macerals was mainly composed of vitrinite, liptodetrinite and inertinite. The complex macerals composition and organic matter source make the activation energy distribution of dark-grey mudstone more dispersed than that of black shale. In addition, affected by the macerals (e.g sporinite and resinite) with low activation energy from terrestrial higher plants, the activation energy of dark-grey mudstone containing sporinite and resinite in the macerals is lower than black shale. Therefore, the dark-grey mudstone containing algae and terrestrial higher plants corresponds to low hydrocarbon generation threshold, slow conversion rate and long hydrocarbon generation cycle. The black shale containing a large number of algae corresponds to high hydrocarbon generation threshold, fast conversion rate and short hydrocarbon generation cycle. Moreover, the conversion rate of black shale containing radioactive elements and more clay minerals is higher than that of dark-grey mudstone.

Source rock properties and kerogen decomposition kinetics of Eocene shales from petroliferous Barmer basin, western Rajasthan, India

Hydrocarbon exploration and production are going on in Barmer basin (Rajasthan, India) for more than a decade. The potential source rocks are of Paleocene – Eocene age, and Mesozoic siltstones form the reservoirs. The western and central portions of the Rajasthan basin are characterised by extensive lignite formations, which can be promising for artificial transformation to oil and gas. We study the source rock properties, depositional environments and hydrocarbon generation potential of the Paleogene lignitic shales of the Giral lignite mine and the Cretaceous Sarnu siltstones for their source and reservoir rock potentiality. The total organic carbon content (TOC) of the Giral samples range between 0.76 and 49.83 wt% and the thermal maturity, as reflected by the pyrolysis Tmax, lies between 412 and 468 °C. Sarnoo siltstones, on the other hand, have a very low TOC ranging from 0.02 to 0.08 wt% and a Tmax of 320–608 °C. The higher TOC and a lower oxygen index (OI) of Giral lignites and shaly lignites indicate the prevalence of a reducing depositional environment. Bulk organic geochemical parameters involving kerogen pyrolysis and thermal degradation kinetics indicate a more promising hydrocarbon generation potential in the lignite than shales, which, however exhibits higher thermal maturity of organic matter. Giral lignites as well as shales show dominantly Type-III heterogeneous kerogen, which is sourced from terrestrial organic matter. This is also corroborated by a broader distribution of activation energy derived from the thermal decomposition of the kerogen. The kerogen transformation ratio (KTR) and the hydrocarbon generation rate (HGR) suggest a considerably earlier and quicker kerogen transformation. Samples from the Sarnoo area offer no significant information on the source rock characteristics, due to their lean organic nature. However, lignites and shaly lignites of the Giral mine are identified as excellent candidates for their suitability towards easy conversion into hydrocarbon products through artificial techniques.

Error correction of vitrinite reflectance in matured black shales: A machine learning approach

Vitrinite reflectance (Ro) analysis is a maturity indication parameter for oil or gas prone source rocks in evaluating hydrocarbon potentials. As a result of challenges in Ro calculations from pyrolysis, finding a way to estimate the maturity of source rocks has been an interesting subject for researchers. The is a current need to improve the Ro calculated from the temperature at which the maximum rate of hydrocarbon generation occurs (Tmax) in matured shale formations. As this will go a long way to accelerate decision making and help avoid excessive expenditure costs on maturity determination for source rock samples while saving time. After the application of the conventional multiple linear regression analysis, the present study employed machine learning methods of random forest (RF), decision tree (DT), gradient boosting machine (GBM), ensembles and bagger (EnB), and multivariate adaptive regression splines (MARS) models for improving the calculated Ro of matured black shales. Oxygen index (OI), the amount of carbon dioxide produced during pyrolysis of kerogen (S3), and vitrinite reflectance measurement (Ro) were used as inputs to estimate the error margin between the calculated vitrinite reflectance and measured vitrinite reflectance. The predictions from the models were then summed with the calculated vitrinite reflectance to produce an improved vitrinite reflectance measurement. The model that generated the most improved vitrinite reflectance measurement, thus, having the least amount of statistical error was selected. EnB achieved the highest accuracy with a correlation coefficient (R) of 0.82 and coefficient of determination (R2) of 0.67 for the improved Ro model. Therefore, a conclusion can be drawn from the results that EnB can adequately improve the Ro of matured rocks through error correction.

Hydrocarbon generation and expulsion quantification and contribution of multiple source rocks to hydrocarbon accumulation in Yanchang Formation, Ordos Basin, China

There are several sets of source rocks in the Yanchang Formation of Mesozoic in the Ordos Basin. At present, Chang 7 source rock is considered to be the main source rock of the Yanchang Formation, although there are no evaluation methods for hydrocarbon generation and expulsion of other source rocks, as well as the hydrocarbon accumulation contribution of source rocks. Utilizing basin simulation and based on a large number of basic geological data and exploration results, the geological body model and thermal history model are established to carry out simulation research on hydrocarbon generation, expulsion, and accumulation of multi-source layers in the Yanchang Formation under geological constraints. The results show that the conversion rate of hydrocarbon generation of each source rock in the Yanchang Formation is mainly distributed in the range of 45%–75%, indicating that the formation still has significant hydrocarbon generation potential and has the geological conditions for in-situ exploitation of shale oil. At present, accumulative hydrocarbon generation is 123.3 × 109 t while hydrocarbon expulsion is 90 × 109 t, with heavy hydrocarbons of C14+ dominating. The Early Cretaceous had the highest concentration of hydrocarbon generation and expulsion, accounting for 68%–82% of total hydrocarbon generation and expulsion. The simulation of hydrocarbon accumulation revealed that before the deposition of the Cretaceous, only a limited amount of hydrocarbon charging occurred in each layer of the Yanchang Formation, with the early Cretaceous being the key period of hydrocarbon charging and accumulation. The “near-source accumulation” characterizes the upper and lower hydrocarbon source layers, and the basin simulation results are in good agreement with proven oil reservoirs and predicted oil reservoir distribution ranges. The study proposed for the first time that the “Chang 7 source rock make major contribution to multi-layer reservoir” mode could be modified to “proximal hydrocarbon accumulation from diverse source rock” mode to stimulate shale oil production and potential layer exploration in the Yanchang Formation of Mesozoic in the Ordos Basin.

Source Rock Evaluation and Hydrocarbon Generation Model of a Permian Alkaline Lakes—A Case Study of the Fengcheng Formation in the Mahu Sag, Junggar Basin

The alkaline lake source rocks of the Fengcheng Formation are developed in the Mahu Sag of the Junggar Basin. Different from traditional continental fresh water and saltwater lake source rocks, alkaline lake source rocks lack targeted evaluation criteria, and it is unknown whether their hydrocarbon generation models are consistent with traditional models. Therefore, in the present study, evaluation standards and hydrocarbon generation models of alkaline lake source rocks are discussed based on geological and organic geochemical data and a systematic summary of the geochemical characteristics of the Fengcheng Formation source rocks. The Fengcheng Formation source rocks are mainly diamictite with mixed argillaceous rock and dolomite; most total organic carbon (TOC) values range from 0.2–1.4%; and the kerogen is primarily oil-prone type II, reaching low- to high-maturity stages. Based on the types of organic matter in source rocks and the relationships between organic matter abundance parameters, the evaluation standard of alkaline lake source rocks is proposed. The Fengcheng Formation is mainly composed of good to excellent source rocks (55.5%) with high hydrocarbon generation potential. The single-peak hydrocarbon generation model of the Fengcheng Formation is similar to that of traditional freshwater or saltwater lakes, with a high hydrocarbon generation rate, two to five times that of the traditional model; its main particularity is in the formation of naphthenic crude oil from the kerogen of bacteria and algae. A new understanding of the hydrocarbon generation potential and model of alkaline lake source rocks in the Fengcheng Formation can provide support for tight oil and shale oil exploration in the Mahu Sag.

Thermal Behavior and Characteristics of Functional Groups on Lignite Secondary Oxidation

ABSTRACT At present, the thermal behavior of lignite and the reaction process of functional groups during secondary oxidation have not been accurately explained. Therefore, the macro thermal behavior and micro characteristics of spontaneous combustion of lignite during secondary oxidation were studied. Coal samples were pre-oxidized to 80 °C, 120 °C, 160 °C, and 200 °C (labeled as raw coal, C-80, C-120, C-160, and C-200, respectively). A thermogravimetric (TG) analyzer and Fourier-Transform Infrared (FTIR) spectrometer were used. The results showed that the high adsorption temperature T1 and critical temperature T2 of C-80 were higher than those of raw coal by 4.41 °C and 11.07 °C, respectively. They indicated that pre-oxidation inhibited the low-temperature oxidation process. The active temperature T4 gradually decreased from C-80 to lower than that of raw coal. The T4 of C-200 was about 20 °C lower than that of raw coal, proving that pre-oxidation accelerated oxygen absorption and the weight-gaining process. The activation energy of pre-oxidized coal samples was significantly lower than that of raw coal samples. The C-80 and C-120 samples had the lowest activation energies: 114.542 kJ/mol and 114.539 kJ/mol, respectively. The content of free hydroxyl groups in pre-oxidized coal samples decreased in general. At C-120, the aliphatic hydrocarbon generation rate significantly increased, and the percentage of peak area continued to increase. During secondary oxidation of C-120 coal samples, various absorption peaks gradually enhanced. Consequently, C-120 was more prone to spontaneous combustion during secondary oxidation.

Thermal maturity modelling for the pre-Miocene source rocks in Ras Garra area, Suez rift Basin, Egypt

The main potential source rocks in the Ras Garra area of the Suez rift Basin are thought to be the pre-Miocene formations, Duwi, Esna, and Thebes, from the oldest to youngest. The total organic carbon content (TOC) ranges from 6.0 to 7.0 wt %, suggesting very good hydrocarbon generative potential. The hydrogen index (HI) ranges from 600 to 700 mg HC/g TOC and the kerogen is of type I/II. Burial and thermal maturity modelling indicates that the pre-Miocene source rocks started the oil generation as early mature stage in Langhian (14.3 Ma), and mid-mature stage in Pleistocene (2.4 Ma). The early mature stage is characterized by the depth to maturity of 1400 m, burial maximum temperature up to 87 °C and vitrinite reflectance (VR) up to 0.7% Ro. The mid-mature stage is characterized by the depth to maturity of 3007 m, burial maximum temperature up to 120 °C and vitrinite reflectance up to 0.75% Ro. The hydrocarbon generation and expulsion history is divided into two phases and Duwi source rock passed the second phase of hydrocarbon generation, and expulsion with transformation ratio (TR) of 29%. From 0.8 Ma until the present, the hydrocarbon generation and expulsion rates have been increased and the generated and expelled hydrocarbons are mainly oil with minor gases. The results show that the most important factor affecting the maturity of the source rocks and hydrocarbon generation and expulsion rates is the durations of early and mid-mature stages.

The Rock-Eval Pyrolysis and Hydrocarbon Generation Kinetic of Four Coal Samples from Different Areas, China

Rock-Eval pyrolysis and hydrocarbon generation kinetic are effective and extensive methods to evaluate source rock. In this study, we chose four coal samples from different areas in China including Fuxing, Guangyuan, Fushun and Taiyuanzu. The results show that Fushun has the highest hydrocarbon generation capacity (399-427mg/g), the lowest dominant activation energy (47Kcal/mol) and frequency factor (1.32*1012/s), which has the highest transformation ratio at different heating rates. It is easy to evaluate the hydrocarbon potential of Fushun. But Fuxing, Guangyuan and Taiyuanzu have different frequency factors and activation energies. In the multiple frequency factors (MFF) model, it is difficult to evaluate hydrocarbon potential by activation energies when frequency factors are different. This study evaluates hydrocarbon potential by comparing transformation ratio at universal and geological heating rate. This is because transformation ratio is a comprehensive result of frequency factor and activation energy. In addition, different heating rates affect the hydrocarbon generation rate of coal samples, the hydrocarbon generation rate is positive with heating rates. For example, the hydrocarbon generation rate of Fushun at 5, 25°C/min are 0.0013 and 0.0051 mg/g.s1. And the temperature difference (AT) of main hydrocarbon generation period heated at 3°C/my and 5, 15, 25°C/min are different, which are 21-52 and 53-99°C.

Modelling reaction and diffusion in a wax-filled hollow cylindrical pellet of Fischer Tropsch catalyst

Previous modelling of fixed-bed, Fischer-Tropsch (FT) reactors has demonstrated the advantages relative to spherical pellets of using cylindrical and shaped pellets to provide improved transport attributes under conditions relevant to industrial operation. However, mass transport models have focussed on the investigation of transport within pellets with spherical symmetry, whilst detailed investigations of more complex shapes have not been undertaken. Here, a pseudo-isothermal, steady-state, two-dimensional model was investigated for catalyst pellets of cylindrical form, both solid and hollow. A cobalt-based catalyst was considered at conditions where the rate of condensable hydrocarbon generation is large enough to result in the accumulation of liquid hydrocarbons in the pores of a catalyst. It was found that effectiveness factors were bounded by those of sphere and slab above and below Thiele moduli of ∼0.75 and ∼1.15, respectively, for the conditions examined, with the effectiveness factors exceeding those of both sphere and slab models between these moduli. Here, comparisons were made on the basis of the characteristic diffusion length, the catalyst particle’s volume divided by its external surface area. However, values of the FT chain growth parameter, α, between these values of Thiele modulus were lower than those of both sphere and slab geometry, and thus under these conditions hollow cylinders gave the greatest methane selectivity.

Research of domanic source rock by pyrolytic gas chromatography-mass spectrometry method

We applied new novel approach based on pyrolytic gas chromatography-mass spectrometry technology (Py-GCMS) developed by Frontier Lab company (Japan) in order to get the same data as it can be acquired by using conventional core analyzer. Experimental part describes the detailed measurement procedure, temperature program and outcomes acquired by using IFP 160000 as a standard sample. We have managed to demonstrate accuracy and reproducibility of tests for the domanic source rock samples and its kerogen extracted respectively. In results of this analytical challenge we were able to get pyrograms providing the S1 (free hydrocarbons), S2 (potential hydrocarbons), Tmax (temperature at which the maximum rate of hydrocarbon generation is reached) information with level of confidence we usually could see doing conventional core analyzer tests. Some important conclusions regarding petroleum generation and thermal maturity have been made. S1 and S2 significantly decrease for kerogen samples with Tmax growth at the same time. Moreover mass spectra data of core samples pyrolizates can be collected easily to detect certain groups of compounds. Sulfur-containing compounds temperature extracted by Py-GCMS can be measured for example. Py-GCMS technology fully comply with mainstream analytical protocol for whole-rock or kerogen analysis and even more, Py-GCMS has a lot of advantages against conventional approach providing us additional valuable information about a sample.

Geochemical characteristics and hydrocarbon generation potential of the first member of Shahejie Formation (E2s1) source rocks in the Dongpu Depression, East China

The Dongpu Depression, containing huge amounts of hydrocarbons, is a typical petroliferous province in the Bohai Bay Basin, east China. As one set of the main source rocks, the first member of Shahejie Formation (E2s1) shows huge exploration potential with approximately 0.83 × 108 t resources remaining to be discovered. However, the geochemical characteristics and thermal evolution history of E2s1 source rocks have still not been determined. In this study, the sedimentary features were firstly analysed based on the geological data. Then the organic matter abundance, kerogen type, and thermal maturity of E2s1 source rocks in the present day were evaluated according to the Rock‐Eval pyrolysis, micro‐components of kerogen, total organic carbon (TOC), and vitrinite reflectance analysis. Furthermore, the evolution of thermal history and hydrocarbon generation was determined using the PetroMod procedure. The results show that dark mudstones and salt rocks were well developed in E2s1, which are propitious for organic matter to grow and preserve. E2s1 source rocks contain abundant organic matter and moderate to good generative source rock potential. E2s1 source rocks mainly consist of Type II kerogen and have entered early to maturation stage for hydrocarbon generation. Due to the limited buried depth, E2s1 source rocks only attained lower thermal maturity and generated finite hydrocarbons. The initial rapid subsidence and the second rift after uplift erosion resulted in the higher geo‐temperature at the end of E3d and the present day. Corresponding to the geo‐temperature evolution, there are two stages of hydrocarbon generation for E2s1 source rocks: The first stage was in the late E3d period, and the late stage was from the late Neogene to the present day. Moreover, the hydrocarbon generation rate and quantity of the late stage are much higher than the first stage, indicating the major hydrocarbon generation stage. Due to the limited hydrocarbon generation capacity, oils generated from E2s1 source rocks are low maturity; thus, it cannot migrate for a long distance and only accumulated around the sag belts.

The effect of pressure and hydrocarbon expulsion on hydrocarbon generation during pyrolyzing of continental type-III kerogen source rocks

In order to define the roles of water and lithostatic pressure in petroleum formation of continental type-III kerogen source rocks, semi-closed hydrous pyrolysis experiments were conducted under with 50–1200 bar water pressure and 125–2000 bar lithostatic pressure at 480 °C. Our results will be of great benefit to the exploration of shale gas and deep petroleum in China. Increasing water pressure from 50 to 325 bar did not affect the yields of gaseous hydrocarbons, oil and bitumen, but increasing water pressure leads the more oil and less gaseous hydrocarbons from continental type-III kerogen in the 325–1200 bar water pressure range under semi-closed conditions. The decreasing yields of gaseous hydrocarbons, dryness of gaseous hydrocarbons and primary hydrogen together confirm that increasing water pressure promotes the primary reaction but decreases the cracking rate of oil. The decreasing values of S2, HI and H/C in the pyrolysed samples confirm that high water pressure can increase the efficiency of hydrocarbon generation from continental type-III kerogen, while the maturation of kerogen correspondingly increases as shown by increasing values of VR and Tmax. In the 125–625 bar lithostatic pressure range, oil cracking and primary reaction of type-III kerogen may have contributed to the decreasing effect of hydrocarbon expulsion. The increasing hydrogen and gaseous hydrocarbon yields also confirm that the cracking of oil is enhanced within this pressure range. The decreasing trends of oil and gaseous hydrocarbon yields indicate that hydrocarbon generation rate was reduced by the high lithostatic pressure in the 625–2000 bar pressure range. The increasing values of S2, HI and H/C, and decreasing values of VR and Tmax of pyrolysed samples confirm the retardation effect of highlithostatic pressure on the efficiency of hydrocarbon generation and maturation. In addition, the results also indicate that expelling hydrocarbons strongly promotes further hydrocarbon generation and retards the cracking of oil from continental type-III kerogen in source rocks.

Petroleum system modeling of the East Coast Basin, Hawke Bay, New Zealand

This study evaluates the petroleum prospectivity of the East Coast Basin, an element of the Hikurangi convergent margin of New Zealand. The basin tectonic environment changed from a dormant convergent margin to convergent margin around the early Miocene, likely causing a decrease in the basin thermal regime. Two end-member paleoheat flow scenarios were used to evaluate thermal maturation of two key source rocks, the Waipawa Black Shale and Whangai Formation, based on calibration to six wells across the basin using vitrinite–inertinite reflectance and fluorescence analysis, as well as Rock-Eval Tmax (the temperature at which the maximum rate of hydrocarbon generation occurs during pyrolysis analysis), thermal alteration index, apatite fission track analysis, and present-day temperatures. This study finds that paleobasal heat flow ranged between 40 and 55 mW/m−2 and decreased to 30 mW/m−2 between 15 and 5 Ma, as bracketed by the two end-member heat flow scenarios. The heat flow scenarios were applied to a palinspastically reconstructed basin and petroleum system model across Hawke Bay. We find that the two distinct heat flow scenarios cause a 3–6.5 m.y. difference in the relative timing of hydrocarbon generation across the basin. Structural events in the basin associated with convergent margin tectonics act as the main control on the timing of generation. Modeling results show transformation of kerogen to hydrocarbons began between early and late Miocene for both source rocks depending on the structural regime in the basin. The structural control on source rock maturation highlights the need for robust palinspastic reconstructions in addition to paleothermometric data to evaluate the petroleum prospectivity of convergent margin basins.

Structural transformations and hydrocarbon generation of low-rank coal (vitrinite) during slow heating pyrolysis

To explore the liquefaction behaviors of low-rank coal vitrinite, the transformations accompanying vitrinite pyrolysis were examined at 10°C per hour between 350 and 520°C. Structural characterization was every 10°C for FTIR and every 20–30°C for 13C NMR and chemical analysis. The gaseous yield of C1–C5 was evaluated by gas chromatography (GC). From the transformations, identified by these various techniques, the structural evolution at this heating rate generally occurred in three distinct stages: 350–390, 410–470, and >490°C. There was a linear increase of 1fa (FTIR-determined aromaticity) between 410 and 470°C. The hydroxyl content decreased while the aro-OH signal increased at temperatures <440°C. There was a slow increase of 1fa during the 490–520°C. The ratio of aromatic bridge carbon to aromatic peripheral carbon (xBP) is an indicator for the size of the basic structural size (BSU). The xBP of vitrinite (0.21) was similar to naphthalene (xBP=0.20) and smaller than the value for anthracene (xBP=0.28). At 440 and 510°C, the xBP is 0.28 and 0.32 respectively, corresponding to anthracene or phenanthrene (xBP=0.31), but <pyrene (xBP=0.37). The increasing xBP demonstrates the aromatization as the slow pyrolysis process continues. There was a significant reduction in the oxygen content between 350 and 390°C, then the content slowly increases between 390 and 430°C (due to preferential loss of hydrocarbons), and finally with a slow reduction >430°C. When >470°C, FTIR data indicated that much of the oxygen was in ether form. The highest contribution of OH (FTIR), the highest C1–C5 hydrocarbon generation rates, and a transition in the aliphatic carbon occurs at 380, 470, and 510°C. The temperature programmed pyrolysis work here is of interest in coal utilization processes where there is a slow-heating rate.

The influence of water on the thermal simulation experiment of hydrocarbon generation and expulsion

ABSTRACTThermal simulation experiment of hydrocarbon generation and expulsion is an important method for the study of source rock evolution. The role played by water in organic material evolution was clarified by summarizing the effect of water on different pyrolysis systems. According to the results, the hydrous experiment has a better hydrocarbon generation rate than the anhydrous experiment in the closed system. In the semi-open system, high-pressure water vapor has good effect to gas generation, while near-critical water (NCW) improves the oil and total hydrocarbon productive rate. So, it is inferred that NCW improves the conversion of kerogen to hydrocarbon reactions, and increases the dissolving capacity of hydrocarbons.