Concentrations Of Hydrocarbon Gases Research Articles

DEVELOPMENT OF A PORTABLE MOTOR VEHICLE EMISSION TEST SYSTEM BASED ON ARDUINO WITH ANDROID INTERFACE

This study takes a comprehensive approach by proposing the design of an innovative emission test tool for motorized vehicles. The primary objective of this tool's design is to establish an alternative emission testing apparatus based on Arduino AT-Mega 2560, proficient in capturing vehicle exhaust emissions. The underlying methodology involves an in-depth investigation of various components, including the MQ2 and MQ7 sensors, microcontrollers, and supplementary sensors. This meticulous observational process aims to unravel the fundamental principles that govern the functionality of these components. Subsequently, the study advances to the prototyping phase, manifesting in the creation of an Android-based emission test system. This system capitalizes on the integration of Arduino programming and App Inventor technology. The integrated system is devised to facilitate sensor data acquisition. The empirical results of the tests indicate that the developed tool effectively measures hydrocarbon gas and carbon monoxide gas concentrations, yielding readings of 6.31% and 3.73%, respectively, under engine conditions ranging from 1500 to 3000 rpm with error in regions 1.4% and 5.1% compared to a commercial instrument. However, during the testing phase, certain challenges surfaced. Notably, the presence of water particles within the tool, coupled with the generation of heat due to the accommodated exhaust gases, increased the temperature within the tool's enclosure. Consequently, the sensors' temperature escalated, resulting in erratic sensor behavior and unstable readings. Nonetheless, a significant advantage of the proposed tool lies in its real-time data visualization capability, which is particularly accessible through Android smartphones. This feature enhances the immediacy of test results, facilitating prompt analysis and decision-making. In conclusion, this study lays the groundwork for an innovative emission testing tool that demonstrates promise in addressing the air quality degradation stemming from vehicular emissions.

Optimization of a Marker Gas for Analyzing and Predicting the Spontaneous Combustion Period of Coking Coal

The adequate assessment of the spontaneous combustion and oxidation characteristics of coking coal can help to reduce its spontaneous combustion potential. In this study, the natural ignition period of the Hex coking coal seam at Ping Coal was calculated based on the programmed-temperature-rise test and the thermal property parameters measured during the spontaneous combustion of the coal. Typical gas concentrations were measured at different oxygen concentrations and coal particle sizes to investigate the changes in the oxygen, carbon–oxygen, and hydrocarbon gas concentrations during the low-temperature oxidation of the coking coal and to determine the indicator gases at different oxidation stages. The following results were obtained: The minimum critical oxygen concentration required for spontaneous ignition was 8%, and fire prevention measures should be implemented below 200 °C. When the temperature of the coal sample reaches 50–60 °C, the rates of CO and CO2 production increase, and when the temperature of the coal sample reaches 100–120 °C, the spontaneous combustion and oxidation of the coal generates alkane gas, in which the coal particle size has a negligible effect on the concentration of each generated gas. CO and C2H4 were selected as the indicator gases for different coking coal oxidation stages, and C2H6 and the C2H4/C2H6 ratio were used as secondary indicators to assist in the analysis. Utilizing the enhanced mathematical model for the shortest spontaneous combustion period of coal seams, in conjunction with a programmed-temperature test device, experimental calculations were conducted to determine the adiabatic spontaneous combustion period. The results indicate that the natural ignition period for the Hex coking coal seam at Ping Coal is approximately 60 days, representing a brief timeframe, and the coal seam is characterized by a high risk of spontaneous combustion.

Field investigation of the transport and attenuation of fugitive methane in shallow groundwater around an oil and gas well with gas migration

‘Fugitive’ or ‘stray’ gas migration from deeper formations due to well bore integrity failure has prompted concern regarding environmental impacts. Unintended methane (CH4) migration can increase greenhouse gas emissions and affect groundwater quality in the critical zone. Although the CH4 transport in shallow aquifers has been investigated at experimental injection sites, no intensive groundwater studies have been published around an oil and gas well that has been leaking for a significant period of time. In this field study, groundwater samples were collected from sixteen groundwater monitoring wells (1.25 m below ground surface) installed around a suspended oil and gas well with decadal scale gas migration (estimated ~0.2 m3/day). Stray CH4 distribution and preferential pathways in the shallow groundwater zone were evaluated though high-resolution profiling of equivalent concentrations of hydrocarbon gases (C1-C6; >85 % CH4 at the study site) and bulk formation electrical conductivity to 6.0 m below ground surface. The highest dissolved CH4 concentration (0.074 mmol/L or 1.18 mg/L) in groundwater (1.25 m bgs) was observed immediately downgradient (1.25 m) of the oil and gas well head. Similarly, high-resolution profiling data also revealed the occurrence of relatively high CH4 concentrations in shallow groundwater along the groundwater flow direction and below fine-grained layers up to 10 m distance from the well head. Microbial DNA analysis from groundwater showed significant community shifts, with the highest relative abundance and diversity of methanotrophs observed in the vicinity of the oil and gas well. This study supports findings from experimental injection and laboratory studies, which also found that significant CH4 transport i) dominantly occurs in the groundwater flow direction, and ii) laterally as free phase below fine-grained layers. The occurrence of CH4 concentrations below saturation after more than two decades of gas migration suggests limited impacts have occurred in the shallow subsurface investigated.

Determination of intermolecular and intramolecular isotopic compositions of low-abundance gaseous hydrocarbons using an online hydrocarbon gas concentration method

The stable isotopic composition of natural gas can be used to identify its origin and source. However, low concentrations of gaseous hydrocarbons in high-mature natural and shale gases hinder accurate determination of their compound- and position-specific isotopic compositions. In this study, an online C2+ hydrocarbon gas concentration system combined with gas chromatography–isotope ratio mass spectrometry (GC–IRMS) or gas chromatography–pyrolysis–gas chromatography–isotope ratio mass spectrometry (GC–Py–GC–IRMS) was developed to determine compound- and position-specific isotopic compositions of low-abundance gaseous hydrocarbons. The lower limit of the gas concentration required for isotope ratio determination using the online concentration system is 0.001% (0.003%) for compound-specific carbon (hydrogen) isotopes and 0.005% for position-specific carbon isotopes and is thus applicable to most natural gas samples. The online concentration technique does not cause significant isotopic fractionation effects, and the combination with GC–IRMS and GC–Py–GC–IRMS can accurately and precisely determine the compound-specific δ13C and δD values of low-content C2+ gaseous hydrocarbons and the position-specific δ13C values (δ13Ca, δ13Cb, and SP values) of propane in low-content propane samples, respectively. The application of our method to two natural gas samples from the Ordos and Sichuan basins further confirms that the online concentration method allows simple and rapid determination of the compound- and position-specific isotopic compositions of low-abundance gaseous hydrocarbons.

Improved SVR based on CARS and BAS for hydrocarbon concentration detection

As one of the main means of discovering and evaluating oil and gas reservoirs, gas logging technology plays an irreplaceable role in oil and gas reservoir exploration. However, with the increasing complexity of oil and gas reservoir exploration, gas logging technology has gradually shifted from chromatographic gas logging to infrared spectral gas logging. Infrared spectroscopy logging technology can not only quickly analyze the content of hydrocarbon components in formation fluids, but also has the advantages of no pollution, high detection efficiency, and accurate analysis. However, there are many types of hydrocarbon gases in formation fluids and a wide range of concentration ranges. How to ensure that infrared spectroscopy can accurately measure the content of hydrocarbon gases is an urgent problem to be solved. To solve this problem, this paper proposes the beetle antennae search algorithm (BAS) combined with the competitive adaptive reweighted sampling (CARS) to improve the SVR for modeling. Firstly, the characteristic wavelength points of the sample set are obtained by CARS, and then the parameters of SVR are optimized by BAS, and then the corresponding high, medium and low concentration prediction models are established. The experimental results show that the accuracy and efficiency of the proposed CARS-BAS-SVR method in the quantitative analysis of hydrocarbon gas components are better than those of the traditional method. Its prediction accuracy for low-concentration hydrocarbon gases is greatly improved, and the overall average error is less than 1‰. It effectively improves the detection accuracy of infrared spectroscopy logging technology, and provides support for the further promotion of infrared spectroscopy in gas logging.

Experimental investigation on the pyrolysis process and product distribution characteristics of organic-rich shale via supercritical water

Low-medium maturity organic-rich shale reservoirs have garnered increasing attention due to their enormous oil and gas generation potential. In this study, the pyrolysis conversion process and product distribution characteristics of shale core samples via supercritical water (SCW) were investigated. The yield of shale oil increased from 4.5 wt% at 385 °C to 15.13 wt% at 425 °C, with the maximum formation rate of shale oil ranging from temperatures of 405 °C to 425 °C. The thermal bitumen reached 15.11 wt% at 405 °C before rapidly decreasing to 3.2 wt% at 425 °C. In the pyrolysis process of shale cores via SCW, the intermediate thermal bitumen produced by thermal cracking of kerogen was retained in the cores and continued to be decomposed into shale oil and gas with the increase of SCW temperature. Simultaneously, a large number of pores were formed in the core matrix due to the massive decomposition of kerogen and thermal bitumen. The increase in SCW temperature greatly decreased the heavy components as well as increased the light components in shale oil. Additionally, aliphatic hydrocarbon cracking or Diels-Alder type aromatization reactions resulted in an increase in aromatic hydrocarbons and a decrease in the H/C atomic ratio of shale oil. Raising SCW temperature increased the content of C2-C5 hydrocarbon gases and the alkenes/alkanes ratio, which was related to the secondary cracking. The important findings of the pyrolysis conversion process and product distribution characteristics of shale cores via SCW not only enrich the theoretical basis in this area, but also provide strong support for the use of SCW in the in-situ conversion of low-medium maturity organic-rich shale reservoirs.

The relationship of lithological and thermobarogeochemical factors in fluid-active zones: A casestudy of the Krasnodonetsky district of Eastern Donbass

The distance of natural gas reservoirs from the country’s industrial centers, the irregularity of spreading of the reserves, the increased costs of gas production and supply, all contribute to the involvement of local and nonconventional resources in various-type production. Coal methane extraction in Eastern Donbass is a goal in this regard. The research included the field study of fluid-active methane-rich zones in coal seams in Eastern Donbass, as well as the lithological and thermobarogeochemical analyses of coal samples. The gas saturation of rocks was correlated with the material composition of deposits. The results of the work can be formulated as follows. Terrigenous rock sediments of age С27 feature the increased content of hydrocarbon gases. Most of methane is localized in the roof of commercialthickness coal seams overlaid with thin clayey shales, siltstones and sandstones of the scoured surface. The scoured-surface sandstone in the coal seam roof has good reservoir properties. The increased fluid permeability of rocks is due to cleavage, which is most intense in heterogeneous strata in the axial parts of small folds. The fluid-saturated zones in coal seams in terrigenous rocks of С27 age at a depth of 240–260 and 320–360 m contain signs of hydrothermal veined mineralization represented by pyrite, dickite, quartz and calcite. These fluidization zones feature high content of gases in coal seams (up to 40–42 m3/t) and enclosing rocks (up to 10–12 m3/t), which points at high prospects for the extraction of hydrocarbon gases from these zones.The study was carried out under the state contract with the Southern Scientific Center, Russian Academy of Sciences, State Registration No. 122020100352-6.

Emission Characteristics of Higher-Molecular-Weight Gases During the Oxidation of Bituminous Coals

ABSTRACT To explore the application prospects of higher-molecular-weight gases (HMWGs) in forecasting coal spontaneous combustion (CSC), the emission characteristics of HMWGs during the oxidation of seven bituminous coals with different degrees of metamorphism were studied using gas chromatography. By analyzing the gas samples released from the oxidation of experimental samples, a total of 20 HMWGs with hydrocarbons as the main component was detected. The concentration of HMWGs changed regularly during the oxidation of experimental samples. The concentrations of most representative hydrocarbon gases increased significantly with increasing temperature but plateaued or even decreased when the temperature exceeded about 210°C. The relationship between HMWG production and the metamorphic degree indicators was nonlinear. The volatile matter content and vitrinite reflectance of coal cannot be used directly to evaluate HMWG production. The initial appearance temperatures of HMWGs during the oxidation of different coal samples also varied. The accuracy of CSC forecasting technology can be significantly improved if HMWGs are used as complementary index gases to forecast the different development stages of bituminous CSC.

FEATURES OF THE DISTRIBUTION OF HYDROCARBON GASES IN THE BOTTOM SEDIMENTS OF THE KARKINITSKAYA BAY

Problem Description and Purpose of the Study. Interest over the past fifty years in the Black Sea shelf has increased as a part of the earth’s crust, which includes oil and gas reserves. This is due to the accumulation of various geological and geophysical information about the structure of the basin`s sedimentary cover, which indicates the processes of generation, migration, and the presence of hydrocarbon accumulation zones within the Black Sea. The study is aimed at geochemical prospecting signs, namely the consequences of the impact of fluidogenic flows recorded in the bottom sediments of the Karkinitsky Bay. Data & Methods. To solve the tasks set, the study uses the method of analyzing and interpreting gas chromatography data at a site located on the Black Sea shelf, at the mouth of the Karkinitsky Bay, in the promising Schmidt and Karkinitskaya areas. This study will show how to identify possible hydrocarbon deposits on the Black Sea shelf, using geochemical data. Consideration of the formation of hydrocarbons was focused on fluidogenesis. Results. Analysis of the obtained data showed that among the hydrocarbon gases, in addition to methane (which is the most quantitatively), there are homologues to pentane, inclusive, and alkenes to propylene. The maps constructed for all gases convincingly showed the abnormal content of hydrocarbon gases within the study area. In addition, among alkanes, there is a tendency to the effect of gas rectification, manifested in the zonal circumference of located anomalies, which were identified in the schematic contours of the degassing pipe. The ratio of schematic degassing pipes to productive deposits indicates the possibility of formation of deposits in the peripheral parts of degassing pipes. This shows that the detection of degassing pipes by geochemical methods is a reliable prospecting indicator of a productive deposit.

Evaluation of Neoproterozoic source rock potential in SE Pakistan and adjacent Bikaner–Nagaur Basin India

Discoveries of heavy crude oil in the Neoproterozoic rocks (Infracambrian rock sequence) from the Bikaner-Nagaur Basin of India emphasize the significance of studying and exploring the Neoproterozoic source rock potential in the southeastern part of Pakistan. This study evaluates the potential of the source rock in the Infracambrian rock sequence (Salt Range Formation) based on surface geochemical surveys, Rock–Eval pyrolysis, source biomarkers, geophysical characterization, and seismic inversion using machine learning for maturity index estimation. Core samples of Infracambrian rock were extracted for Rock–Eval pyrolysis and biomarker characterization. Additionally, 81 geomicrobial soil and gas samples were collected from the surface to explore the petroleum system and potential source rocks in the subsurface. Advanced interpretation techniques were used to investigate the origin and concentration of hydrocarbon gases at the surface, including Rock–Eval pyrolysis, thermal maturity, source biomarkers, and the environment of deposition of organic matter. The results show that the investigated samples are characterized by restricted marine clay devoid of sedimentary carbonate facies with thermal maturity in the early stage of the oil generation window. The seismic inverted maturity index profile demonstrates a reasonable correlation of thermal maturity with the biomarkers and Rock–Eval pyrolysis. Further scrutiny of the surface geochemical samples confirms the presence of higher concentrations of thermogenic C2–C4 hydrocarbons in the vicinity of anticlinal structures, suggesting the existence of an effective migration path along deep-seated faults to the surface. This study concludes that the Infracambrian rocks on the eastern flank of Pakistan are thicker, thermally mature, and have deep-seated structural closures, indicating a greater probability of heavy and light oil in this area than in the Bikaner–Nagaur Basin, India.

Hydrocarbon Gases in Seafloor Sediments of the Edge Shelf Zone of the East Siberian Sea and Adjacent Part of the Arctic Ocean

The continental margins of the East Siberian Sea and Arctic Ocean are among the Earth’s most inaccessible marine environments for hydrocarbon research due to the almost year-round presence of ice cover. Despite this, limited preliminary assessments which have been carried out to date have all yielded some indication of high oil and gas production potential in these regions. This article presents the results of gas-geochemical studies of seafloor sediments of the East Siberian Sea, obtained in three expeditions onboard the R/V “Akademik Lavrentiev” in 2008 (LV45), 2016 (LV77), and 2020 (LV90). The composition of sorbed hydrocarbon gases in seafloor sediments was analyzed. In addition, the stable isotopic composition of carbon was determined for CH4, C2H6, and CO2 in gases, which were desorbed from marine sediments. The sediments were also analyzed for organic matter content. Despite the absence of observable gas seepage directly into the water column, at some stations, increased concentrations of methane and hydrocarbon gases were encountered, indicating the widespread predominance of thermogenically derived gases. We present a hydrocarbon classification system which delineates eight identifiable sources of regional gas occurrences (coal gas, igneous rocks, solid bitumen, condensate-gas, gas-condensate, oil gas, gas oil, and oil gases). A stable isotopic analysis of carbon in CH4, C2H6, and CO2 indicates varying degrees of mixing between a shallow, early-kerogen gas source and a deeper mantle carbon source in some areas of the study.

Petrophysical Characterization and Gas Accumulation of Wufeng-Longmaxi Shale Reservoir in Eastern Margin of Sichuan Basin, SW China

Shale gas plays a significant role in meeting the increasing demand of energy resources, which enables the exploration and exploitation of gas from shale reservoir to be emphasized gradually. Aiming to serve a more responsible and efficient shale gas development, for example, to guide the hydraulic/nonaqueous fracturing operation, this work organized a comprehensive assessment on the petrophysical characterization and gas accumulation of the Upper Ordovician Wufeng-Lower Silurian Longmaxi shale reservoir (abbreviated as WL shale). Results indicate that the WL shale in Well-YC4 contains three third-order sequences (SS1-lower WL, SS2-middle WL, and SS3-upper WL), and each sequence contains a transgressive system tract (TST) and a high-stand system tract (HST), according to the logging information. Meanwhile, the SS1, SS2, and SS3 experienced variable sedimentary environment—with different relatively oxygenic and hydrodynamics. And the bottom section (SS1 and SS2) has a soft great brittle index (BI) value than the upper section (SS3), suggesting the bottom WL shale is better suited for hydraulic fracturing than the upper section. Besides, the organic matter indicates the WL shale has a decent hydrocarbon generation ability, and the thermal evolution degree is also conducive to the full generation of shale gas. The gas content of WL shale ranges in the scope of 0.76 m3/t~2.38 m3/t, in which CH4 is the primary composition and occupies 95.51%~99.36%, and the content of heavy hydrocarbon gases is limited. Besides, the drying coefficient indicates the dry gas is the dominate molecular composition in the gas content of WL shale. Hopefully, this work is instructive to a certain extent for the researchers and engineers who are working on WL shale gas in Sichuan basin.

Influence of oil structures on the component composition of free gases of potash reservoirs at the BPPU-4 mine field of PJSC “Uralkali”

The influence of oil structures on the content of heavy hydrocarbon gases in the component composition of free gases in the rocks of the overlying silvinite formations is considered. There is an assumption about the influence of reef formations on the overlying sedimentary deposits and the development of sub-vertical cracks, through which heavy hydrocarbon gases can penetrate into the overlying potash layers. The aim of the study is to study the relationship between the nature of the distribution of heavy hydrocarbon gases and geological disturbances and the subsequent prediction of the gas-dynamic situation during the development of potash reservoirs. The method consists of drilling holes into the roof of the mine, sealing the hole with a sealer, and then taking gas from the sealed part to the sampler and analyzing it on a gas chromatograph. The highest values of heavy hydrocarbon gases were determined for the Bc, AБ and KpII formations at the BPPU-4 mine field of PJSC Uralkali.

Effect of Electrode Plates on the Engine Performance and Gas Emissions of a Four-Stroke Petrol Engine

The effectiveness generation of HHO gas depends on the characteristic of the electrode plates. This research aims to investigate the effect of the HHO gas generator produced through the water electrolysis technique. The effect of several controlled factors, such as the number, distance, and area of electrode plates used in the water electrolysis process to produce HHO gas, were studied and analyzed using a factorial full design approach (RBFAD). Stainless Steel of 1 mm thickness has been chosen as an electrode plate material. A single-cylinder four-stroke S.I. engine was used as the test engine. The engine was tested at 16 different setups where the engine speed and exhaust emission of carbon monoxide (CO) and hydrocarbon (HC) gasses were recorded. The statistical significance of these controlled factors contributing to the engine performance and exhaust emission has been established with the analysis of variance. It was found that the number of plates that interacted with a large area of electrode plate is a significant factor that caused an increase in engine speed on an average of 26%, an average reduction in CO by 43%, and a decrease in HC gas by 42%. In conclusion, the higher number of electrode plates and a higher electrode plate area produced more HHO gas that yields completed internal combustion. Thus, it can enhance the engine speed and reduces the CO and HC gas content in exhaust emissions.

Features of the composition of gas sorbed in the rocks of the upper part of the sedimentary cover section

The topicality of the article is determined by the insufficient reliability of geochemical oil and gas exploration data for the localization of petroliferous geological objects. Geochemical surveys are carried out to mapping hydrocarbon anomalies caused by vertical migration of fluid from hydrocarbon deposits. Practice shows that not all anomalies in the content of hydrocarbons in the near-surface environment are related to the oil-bearing capacity of a given subsoil area. Therefore, when interpreting the data of geochemical oil and gas prospecting surveys, it is necessary to take into account not only quantitative indicators (namely, content of hydrocarbon gases on the surface), but also the composition of the gas sorbed by the near-surface substrate. The purpose of the article is to determine the composition of the dissipated gases in the rocks of the upper part of the section, to reveal the inter-component relationships, and, on this basis, to determine the genesis of each gas component sorbed by the rocks of the upper part of the section. To solve this problem, statistical processing of data on the component content of gas from core degassing of shallow (up to 30 m) wells drilled in the petroliferous territory of the north of Western Siberia was carried out. The obtained results confirmed the genetic heterogeneity of dissipated hydrocarbons and inorganic gases in the upper part of the sedimentary cover.

Smolder behavior and emissions byproducts of aircraft composite coupons

Carbon fiber composites are a staple in aircraft manufacturing due to their enhanced physical properties and reduced mass compared to metal alloys. In the event of a mishap where these composites are subject to high heat, such as in a fire, resin char and carbon fibers in composites have been shown to oxidize and smolder. The smolder properties and emissions byproducts of aircraft composites are not well understood. In the present study, carbon fiber composites with two polymeric resin systems, epoxy and bismaleimide (BMI), were burned via cone calorimeter at three heat fluxes (35, 50, 85 kW/m2) and allowed to smolder for 30 min after the flame self-extinguished. The cone calorimeter measured parameters describing fire properties during combustion, while polycyclic aromatic hydrocarbon (PAH) and combustion gas concentrations within composite emissions were measured by commercially available instruments and cone calorimetry. Heat release rate, combustion gases, and mass loss rates all increased with heat flux for both composite resin systems. BMI composites emitted more PAHs than epoxy composites. These results suggest that higher heat flux correlates with increased composite decomposition and emissions during flaming combustion and smoldering, and that BMI composites pose a higher risk to produce PAHs and carbon monoxide during smolder than epoxy composites.

Overheating and discharge fault identification for novel three-element mixed oil–paper insulation system based on new characteristic gas combination parameters

To support the safe operation of the novel three-element mixed insulation oil (TEMO) transformer, gas generation behaviors of the TEMO oil–paper insulation system under overheating faults and discharge faults were investigated. Results show that that the content of H2 and C2H6 generated by TEMO–paper insulation system is much higher than that in conventional mineral oil (MO)–paper insulation system under different overheating temperatures. Under partial discharge fault, the content of H2 dissolved in oil changes distinctly, while the content of C2H2 also increases with the discharge time. Under surface flashover breakdown, AC breakdown and lightning impulse breakdown fault, the content of H2 and C2H2 changes greatly compared to other gases, while the concentration of total hydrocarbon gases in TEMO–paper insulation system is smaller than that in MO–paper insulating system after the same breakdown times. The diagnosis model of overheating and discharge faults for the TEMO–paper insulation system was proposed based on the oil dissolved gas analysis, while H2, C2H2 and C2H4 were chosen as the characteristic gases and the boundary settings were determined. The verified result for the low-temperature overheating, lightning impulse and surface flashover fault for the TEMO–paper insulation system presents that the new diagnosis model is effective.

Geochemical characteristics, genetic types, and source of natural gas in the Sinian Dengying Formation, Sichuan Basin, China

The Sinian Dengying Formation is a key target for deep oil and gas exploration in the Sichuan Basin, China. Natural gas was mainly distributed in the Ziyang–Weiyuan area (ZWA) and the Gaoshiti–Moxi area (GMA). At present, the genetic types and sources of natural gas are still unclear and controversial. The chemical composition, stable carbon isotopes, and biomarkers were used to analyze geochemical characteristics, genetic types, and gas–source relations. The results showed that the composition and content of hydrocarbon gas in the ZWA and GMA were similar. Natural gas was a typical dry gas with an average dry coefficient (C1/C1+) of 0.9991, which reflected higher methane (CH4) content and lower heavy hydrocarbon gas (C2+) content. For nonhydrocarbon gas, CO2 (0.01%–26.34%), N2 (0.03%–24.95%), H2S (0.10%–3.19%), and He (0.01%–0.37%) were mainly distributed. Compared with the GMA, the ZWA was characterized by higher N2 content and lower CO2 content. Although the carbon isotopes had not been reversed, the values of δ13C2–δ13C1 were different between the ZWA and GMA, with the GMA having the higher value. The assemblage relation between the natural gas composition and carbon isotopes indicated that the natural gas type was dominated by oil-cracking gas. Mud-shale in the high maturity stage of thermal evolution greatly influenced on the content of N2 and He. H2S mainly belonged to thermochemical sulfate reduction (TSR), and most of CO2 was formed by deep carbonate metamorphism and TSR. The gas–source relation showed that natural gas in the ZWA was derived from the Cambrian Qiongzhusi Formation and that the gas in the GMA mainly originated from the Sinian Dengying Formation and the Cambrian Qiongzhusi Formation. The established hydrocarbon generation model indicated that the Sinian Dengying Formation is potentially gas-rich.

Simulation Study of Hydrocarbon Generation Characteristics in Siliceous Rock

Late Triassic-early Jurassic silica rocks are widely developed in Northeast China. To evaluate the silica rock hydrocarbon generating capacity, we have simulated the hydrocarbon evolution process by thermal simulation experiments and analyzed the hydrocarbon generation characteristics. The experiments were carried out at six temperature points 250, 270, 290, 310, 330, and 350°C, and the content of the gaseous and liquid products was measured. The experiments results showed that the organic-rich siliceous rocks are characterized by a relatively high hydrocarbon-generating capacity. The gaseous products are generated at different temperatures, while natural gas is mainly generated when the peak period of oil generation is completed. Natural gas includes hydrocarbon and non-hydrocarbon gases. Hydrocarbon gases include methane, ethane, propane, butane, pentane, and other heavy hydrocarbon gases. Non-hydrocarbon gases include hydrogen, nitrogen, carbon monoxide, and carbon dioxide. Carbon dioxide is the main component of the gas products, followed by hydrogen, methane, nitrogen, and other gases, but the total content of other gases is extremely low. Carbon dioxide generated during all stages of the oil generation process accounts for the vast majority, but in geological conditions, it will eventually be consumed by hydration. Nitrogen is mainly produced in the early stage. The content of hydrogen and hydrocarbon gases increases with increase in temperature, but hydrogen is usually depleted in the actual reservoir due to its strong chemical activity.

ГЕОДИНАМІКА

Purpose. Our research main purpose is to demonstrate the use of entropy maximization method for calculating the geochemical system composition, which consist of solid and gaseous organic substances. Changing the geodynamic situation is the driving force of elements redistribution between compounds in such systems. According to thermodynamic apparatus the main factors influencing this redistribution are pressure, temperature and the initial number of elements. Methods. Gibbs energy minimizing, maximizing the entropy, independent chemical reactions constants, Lagrange's method of undetermined multipliers, Newton–Raphson iterative method. It is well known that the fossilized organic matter, which is mainly represented by many types of kerogen, is an irregular polymer with structure, which cannot be described definitely. To calculate the equilibrium in the kerogen/gas system and obtain reliable results, it is necessary to apply a new model, without using the model structures of kerogen. We have proposed and described in detail a method of applying the Jaynes' formalism and maximizing entropy method to calculate the change in the composition of the kerogen/gas system with geodynamic regimes changing. Software in the Excel macros form and a compiled dynamic library, written in Visual Basic language, was created for calculations. Results. To verify the reliability of the proposed method and algorithm, we calculated the composition of the geochemical system, consisting of type II kerogen, methane to pentane hydrocarbons (including isomers), carbon dioxide, water and hydrogen sulfide. The calculation result is the molar fractions of hydrocarbon components and additive groups that make up kerogen, for different depths of the earth's crust. The calculations were performed for three heat fluxes: 40, 75 and 100 mW/m2, lithostatic pressure taken in account. Scientific novelty. It is established that the geodynamic situation changing in a complex way affects the distribution of elements between gases and kerogen in a closed thermodynamic system; modeling the kerogen/gas system behavior by method of entropy maximization provides results that do not contradict to study the structure of type II kerogen at different stages of maturity; the character of changes in the concentrations of hydrocarbon gases in equilibrium with type II kerogen indicates the inconsistency of the "oil window" hypothesis with the postulates of equilibrium thermodynamics. Practical significance. The entropy maximization method can be successfully used to calculate the composition of various geochemical systems consisting of organic compounds. The method is suitable for determining chemical composition of the irregular polymers, such as kerogen, bitumen, humic, in equilibrium with organic and inorganic gases and liquids.