Previous studies have shown that the Eocene oil shale sequences in the Green River Basin contain long-period astronomical age information.The fine-scale chronological characteristics of the oil shale laminae remain la...Previous studies have shown that the Eocene oil shale sequences in the Green River Basin contain long-period astronomical age information.The fine-scale chronological characteristics of the oil shale laminae remain largely unexplored.We selected finely laminated oil shales formed in deep-water environments characterized by stable water column stratification as the primary focus of this study,using microscopy and micro-area X-ray fluorescence(μ-XRF)techniques.By integrating high-resolution elemental data with timeseries analysis,we identified significant periodic signals associated with solar activity(Hale and Schwabe cycles)and ENSO.The results indicate that the alternations of light and dark laminae in the Green River Formation oil shale correspond to alternating dry and wet climate regimes:the light laminae are dominated by carbonate minerals,reflecting drier and milder conditions,while the dark laminae are enriched in terrigenous clastics and organic matter,indicating periods of increased precipitation and warmer temperatures.The detected periodicities(23.5 years,13.3 years and 5.8 years)are highly consistent with modern observations,demonstrating that the lower Eocene Green River oil shale effectively records short-term solar activity and climate variability.Furthermore,our findings confirm that a persistent"permanent El Niño"state did not develop under Early Eocene greenhouse conditions,providing a refined chronological framework for highresolution paleoclimate studies during greenhouse intervals.展开更多
In the context of convection-heating-based in situ oil shale retorting,fractures serve as primary pathways for fluid migration and product extraction.This study investigates the permeability and microstructural evolut...In the context of convection-heating-based in situ oil shale retorting,fractures serve as primary pathways for fluid migration and product extraction.This study investigates the permeability and microstructural evolution of oil shale during water vapor injection in single-fracture and no-fracture scenarios.Three types of oil shale are investigated:intact oil shale,oil shale with a single straight crack,and oil shale with a single hydraulic crack.With increasing water vapor temperature,the permeabilities of the intact oil shale and oil shale with a fractured crack exhibit a trend of initial increase,followed by a decrease,and then a subsequent increase.However,the permeability of oil shale with a single straight crack consistently increases and exceeds that of oil shale with a fractured crack.The temperaturedependent permeability changes in fractured oil shale-a slight decrease in fracture cracks and a gradual increase in straight cracks-mainly occur in the range of 300℃-350℃.The permeability of oil shale with a straight crack is approximately three times that of oil shale with a fractured crack.This is attributed to the retention of viscous asphaltene and the frictional resistance caused by the rough fracture structure.For the oil shale with a single crack,the crack permeability has a dominant influence on the overall permeability of the rock.The contribution of the permeability of the straight crack exceeds 94.6%,while that of the permeability of the fractured crack is greater than 86.1%.The disparity in the contribution of these two crack structures is evident at 350℃-550℃.展开更多
Simulation of thermal-reactive-compositional flow processes is fundamental to the thermal recovery of ultra-heavy hydrocarbon resources,and a typical oilfield practice is the in-situ conversion process(ICP)implemented...Simulation of thermal-reactive-compositional flow processes is fundamental to the thermal recovery of ultra-heavy hydrocarbon resources,and a typical oilfield practice is the in-situ conversion process(ICP)implemented in oil shale exploitation.However,accurately capturing the intricate flow dynamics of ICP requires a large number of fine-scale grid-blocks,which renders ICP simulations computationally expensive.Apart from that,plenty of oil shale reservoirs contain natural fractures or require hydraulic fracturing to enhance fluid mobility,creating further challenges in modeling pyrolysis reactions in both rock matrices and fractures.Targeted at the above issues,this work proposes a novel dual-model dualgrid upscaling(DDU)method specifically designed for solid-based thermal-reactive-compositional flow simulations in fractured porous media.Unlike existing upscaling techniques,the DDU method incorporates the upscaling of fracture grids using the embedded discrete fracture modeling(EDFM)approach and introduces a new concept of simplified models to approximate fine-scale results,which are used to correct reaction rates in coarse-scale grids.This method uniquely achieves efficient upscaling for both matrix and fracture grids,supports both open-source and commercial simulation platforms without modifying source codes,and is validated through 3D ICP models with natural fractures.The results indicate that the application of the DDU method can provide a close match with the fine-scale simulation results.Moreover,the DDU method has drastically improved the computational efficiency and speeded up the fine-scale simulation by 396-963 times.Therefore,the proposed DDU method has achieved marked computational savings while maintaining high simulation accuracy,which is significant for the development efficiency and production forecasting of oil shale reservoirs.展开更多
The increasing demand for unconventional oil and gas resources,especially oil shale,has highlighted the urgent need to develop rapid and accurate strata characterization methods.This paper is the first case and examin...The increasing demand for unconventional oil and gas resources,especially oil shale,has highlighted the urgent need to develop rapid and accurate strata characterization methods.This paper is the first case and examines the drilling process monitoring(DPM)method as a digital,accurate,cost-effective method to characterize oil shale reservoirs in the Ordos Basin,China.The digital DPM method provides real-time in situ testing of the relative variation in rock mechanical strength along the drill bit depth.Furthermore,it can give a refined rock quality designation based on the DPM zoning result(RQD(V_(DPM)))and a strength-grade characterization at the site.Oil shale has high heterogeneity and low strata strength.The digital results are further compared and verified with manual logging,cored samples,and digital panoramic borehole cameras.The findings highlight the innovative potential of the DPM method in identifying the zones of oil shale reservoir along the drill bit depth.The digital results provide a better understanding of the oil shale in Tongchuan and the potential for future oil shale exploration in other regions.展开更多
This paper presents new geological and geochemical data from the Shuanghu area in northern Tibet, which recorded the Early Toarcian Oceanic Anoxic Event. The stratigraphic succession in the Shuanghu area consists most...This paper presents new geological and geochemical data from the Shuanghu area in northern Tibet, which recorded the Early Toarcian Oceanic Anoxic Event. The stratigraphic succession in the Shuanghu area consists mostly of grey to dark-colored alternating oil shales, marls and mudstones. Ammonite beds are found at the top of the Shuanghu oil shale section, which are principally of early Toarcian age, roughly within the Harplocearas falciferrum Zone. Therefore, the oil shale strata at Shuanghu can be correlated with early Toarcian black shales distributing extensively in the European epicontinental seas that contain the records of an Oceanic Anoxic Event. Sedimentary organic matter of laminated shale anomalously rich in organic carbon across the Shuanghu area is characterized by high organic carbon contents, ranging from 1.8% to 26.1%. The carbon isotope curve displays the δ 13C values of the kerogen (δ 13Ckerogen) fluctuating from –26.22 to –23.53‰ PDB with a positive excursion close to 2.17‰, which, albeit significantly smaller, may also have been associated with other Early Toarcian Oceanic Anoxic Events (OAEs) in Europe. The organic atomic C/N ratios range between 6 and 43, and the curve of C/N ratios is consistent with that of the δ 13Ckerogen values. The biological assemblage, characterized by scarcity of benthic organisms and bloom of calcareous nannofossils (coccoliths), reveals high biological productivity in the surface water and an unfavorable environment for the benthic fauna in the bottom water during the Oceanic Anoxic Event. On the basis of organic geochemistry and characteristics of the biological assemblage, this study suggests that the carbon-isotope excursion is caused by the changes of sea level and productivity, and that the black shale deposition, especially oil shales, is related to the bloom and high productivity of coccoliths.展开更多
Pyrolysis characteristics of a North Korean oil shale and its pyrolysates were investigated in this paper. The pyrolysis experiments were conducted below 600 ℃ at a heating rate of 10, 15, 20 and 25 ℃/min, respectiv...Pyrolysis characteristics of a North Korean oil shale and its pyrolysates were investigated in this paper. The pyrolysis experiments were conducted below 600 ℃ at a heating rate of 10, 15, 20 and 25 ℃/min, respectively. The kinetics data were calculated using both integral and differential methods with the assumption of first order kinetics. The results show that the averaged oil content of the North Korean oil shale is about 12.1 wt% and its heat value is 13,400 kJ/kg. The oil yields at different retorting temperatures show that the higher the retorting temperature the greater the oil and retorting gas yields. The optimal retorting temperature for the North Korean oil shale is about 500 ℃. The properties of the North Korean shale oil including density, viscosity, flash point and freezing point are found to be relatively low compared with those of shale oil from FuShun, China. The gasoline fraction, diesel fraction and heavy oil fraction account for 11.5 wt%, 41.5 wt% and 47 wt%, respectively. The major pyrolysis gases are ca4 （the most abundant）, H2, CO2, H2S, CO, and C2-C5 hydrocarbons. The heat value of retorting gas is more than 900 kJ/mol, and the retorting gas has high sulfur content.展开更多
Na-A zeolite was synthesized using oil shale ash （OSA）, which is a solid by-product of oil shale proc- essing. The samples were characterized by various techniques, such as scanning electron microscopy, X-ray diffra...Na-A zeolite was synthesized using oil shale ash （OSA）, which is a solid by-product of oil shale proc- essing. The samples were characterized by various techniques, such as scanning electron microscopy, X-ray diffrac- tion and Brunaner Emmet Teller method. The batch isothermal equilibrium adsorption experiments were performed to evaluate the ability of Na-A zeolite for removal of Cu （II） from aqueous solutions. The effects of operating pa- rameters, such as concentration of copper solutions, adsorbent dosages, pH value of solutions and temperature, on the adsorption efficiency were investigated. The equilibrium adsorption data were fitted with Langmuir and Freundlich models. The maximum adsorption capacity of Na-A zeolite obtained from the Langmuir adsorption iso- therm is 156.7 mg.g-t of Cu （lI）. The increase of pH level in the adsorption process suggests that the uptake of heavy metals on the zeolite follows an ion exchange mechanism. The batch kinetic data fit the pseudo-second order equation well. The thermodynamic parameters, such as changes in Gibbs free energy （AG）, enthalpy （AH） and en- tropy （AS）, are used to predict the nature of the adsorption process. The negative AG values at different tempera- tures confirm that the adsorption processes are spontaneous.展开更多
The marine oil shales of the Qiangtang Basin, northern Tibet, exposed in the Biluo Co, Tuonamu, Shenglihe and Changsheshan areas are believed to be important petroleum source rocks. This work comprehensively analyzed ...The marine oil shales of the Qiangtang Basin, northern Tibet, exposed in the Biluo Co, Tuonamu, Shenglihe and Changsheshan areas are believed to be important petroleum source rocks. This work comprehensively analyzed the carbon isotopes, trace elements, and calcareous nannofosills, ammonites and bivalves of the Biluo Co section in the Qiangtang Basin. The organic carbon isotopes show a positive excursion close to 2.17‰（relative to PDB）, which, albeit significantly smaller, may also be associated with other Early Toarcian Oceanic Anoxic Events（T-OAE） in the European epicontinental seas and the Tethyan continental margins. Coinciding with the Early Toarcian transgression, the oxygen deficiency in bottom water had led to dysoxic-anoxic conditions and deposition of black shales lacking benthic fauna. Under such condition, the redox-sensitive trace metals such as Mo, V, Ni, Cr, and U were enriched, in conjunction with high planktonic productivity of Watznaueriaceae calcareous nannofossils. Comparison of the results with the records of chemo-and biostratigraphy, as well as the palaeogeography during the Early Jurassic suggests that the anoxia linked to the Early Toarcian oceanic anoxic event was mainly caused by the high surface water temperature, sea-level rise and an increase of surface water productivity.展开更多
Based on the element geochemistry and biomarkers of the oil shale from the Chang 7 sub-unit in the southern Ordos Basin,the depositional conditions and organic source of the oil shale are discussed.Biomarkers analyses...Based on the element geochemistry and biomarkers of the oil shale from the Chang 7 sub-unit in the southern Ordos Basin,the depositional conditions and organic source of the oil shale are discussed.Biomarkers analyses show that the oil shale has a homologous organic matter source,with a mix of plankton and advanced plants.U/Th and V/Ni ratios suggest that the redox condition is dominated by a reducing condition,and the degree of anoxia in the Tongchuan area is higher than that of the Xunyi area.Sr/Ba ratios illustrate that the oil shale is deposited in fresh water and the paleosalinity in the Tongchuan area is slightly higher.Fe/Ti ratios imply that the Tongchuan area underwent obvious hydrothermal fluid activities.Sr/Cu ratios show warm and humid paleoclimate in both areas.As assessed by(La/Yb)NASC,the deposition rate in the Tongchuan area is relatively lower.Fe/Co and Th/U ratios suggest that the paleo-water-depth in the Tongchuan area is deeper.The source rock could have the advance plants source,which must have close relationship with the Qinling orogeny.Comparing the paleoenvironment,the Tongchuan area has better depositional conditions,and is the key oil shale exploration area in the southern Ordos Basin.展开更多
Using trace elements to reconstruct paleoenvironment is a current hot topic in geochemistry. Through analytical tests of oil yield, ash yield, calorific value, total sulfur, major elements, trace elements, and X-ray d...Using trace elements to reconstruct paleoenvironment is a current hot topic in geochemistry. Through analytical tests of oil yield, ash yield, calorific value, total sulfur, major elements, trace elements, and X-ray diffraction, the quality, mineral content, occurrence mode of elements, and paleoenvironment of the Zhangjiatan oil shale of the Triassic Yanchang Formation in the southern Ordos Basin were studied. The analyses revealed relatively high oil yield(average 6.63%) and medium quality. The mineral content in the oil shale was mainly clay minerals,quartz, feldspar, and pyrite; an illite–smectite mixed layer comprised the major proportion of clay minerals. Compared with marine oil shale in China, the Zhangjiatan oil shale had higher contents of quartz, feldspar, and clay minerals, and lower calcite content. Silica was mainly in quartz and Fe was associated with organic matter, which is different from marine oil shale. The form of calcium varied. Cluster analyses indicated that Fe, Cu, U, V, Zn, As,Cs, Cd, Mo, Ga, Pb, Co, Ni, Cr, Sc, P, and Mn are associated with organic matter while Ca, Na, Sr, Ba, Si, Zr, K,Al, B, Mg, and Ti are mostly terrigenous. Sr/Cu, Ba/Al, V/(V+ Ni), U/Th, AU, and δU of oil shale samples suggest the paleoclimate was warm and humid, paleoproductivity of the lake was relatively high during deposition of the shale—which mainly occurred in fresh water—and the paleo-redox condition was dominated by reducing conditions. Fe/Ti ratios of the oil shale samples suggest clear hydrothermal influence in the eastern portion of the study area and less conspicuous hydrothermal influence in the western portion.展开更多
A study of reaction mechanisms and chemical kinetics of pressurized pyrolysis of Chinese Liushuhe oil shale in the presence of water were conducted using an autoclave for simulating and modeling in-situ underground th...A study of reaction mechanisms and chemical kinetics of pressurized pyrolysis of Chinese Liushuhe oil shale in the presence of water were conducted using an autoclave for simulating and modeling in-situ underground thermal degradation.It was found that the oil shale was first pyrolyzed to form pyrobitumen,shale oil,shale gas and residue,then the pyrobitumen was further pyrolyzed to form more shale oil,shale gas,and residue.It means that there are two consecutive and parallel reactions.With increasing temperature,the pyrobitumen yield,as intermediate,first reached a maximum,then decreased to approximately zero.The kinetics results show that both these reactions are first order.The activation energy of pyrobitumen formation from oil shale is lower than that of shale oil formation from pyrobitumen.展开更多
Thermo-gravimetric-analysis(TGA) was used to analyze the combustion characteristics of an oil shale and semi-cokes prepared from it.The effect of prior pyrolysis and TGA heating rate on the combustion process was stud...Thermo-gravimetric-analysis(TGA) was used to analyze the combustion characteristics of an oil shale and semi-cokes prepared from it.The effect of prior pyrolysis and TGA heating rate on the combustion process was studied.Prior pyrolysis affects the initial temperature of mass loss and the ignition temperature.The ignition temperature increases as the volatile content of the sample decreases.TG/DTG curves obtained at different heating rates show that heating rate has little effect on ignition temperature.But the peak of combustion shifts to higher temperatures as the heating rate is increased.The Coats-Redfern integration method was employed to find the combustion-reaction kinetic parameters for the burning of oil shale and oil shale semi-coke.展开更多
The autothermic pyrolysis in-situ conversion process (ATS) consumes latent heat of residual organic matter after kerogen pyrolysis by oxidation reaction, and it has the advantages of low development cost and exploitat...The autothermic pyrolysis in-situ conversion process (ATS) consumes latent heat of residual organic matter after kerogen pyrolysis by oxidation reaction, and it has the advantages of low development cost and exploitation of deep oil shale resources. However, the heating mechanism and the characteristic of different reaction zones are still unclear. In this study, an ATS numerical simulation model was proposed for the development of oil shale, which considers the pyrolysis of kerogen, high-temperature oxidation, and low-temperature oxidation. Based on the above model, the mechanism of the ATS was analyzed and the effects of preheating temperature, O_(2) content, and injection rate on recovery factor and energy efficiency were studied. The results showed that the ATS in the formation can be divided into five characteristic zones by evolution of the oil and O_(2) distribution, and the solid organic matter, including residue zone, autothermic zone, pyrolysis zone, preheating zone, and original zone. Energy efficiency was much higher for the ATS than for the high-temperature nitrogen injection in-situ conversion process (HNICP). There is a threshold value of the preheating temperature, the oil content, and the injection rate during the ATS, which is 400 °C, 0.18, and 1100 m3/day, respectively, in this study.展开更多
As an important unconventional resource, oil shale has received widespread attention. The oil shale of the Chang 7 oil layer from Triassic Yanchang Formation in Ordos Basin represents the typical lacustrine oil shale ...As an important unconventional resource, oil shale has received widespread attention. The oil shale of the Chang 7 oil layer from Triassic Yanchang Formation in Ordos Basin represents the typical lacustrine oil shale in China. Based on analyzing trace elements and oil yield from boreholes samples, characteristics and paleo-sedi- mentary environments of oil shale and relationship between paleo-sedimentary environment and oil yield were studied. With favorable quality, oil yield of oil shale varies from 1.4% to 9.1%. Geochemical data indicate that the paleo-redox condition of oil shale＇s reducing condition from analyses of V/Cr, V/（V ＋ Ni）, U/Th, δU, and authi genic uranium. Equivalent Boron, Sp, and Sr/Ba illustrate that paleosalinity of oil shale is dominated by fresh water. The paleoclimate of oil shale is warm and humid by calculating the chemical index of alteration and Sr/Cu. Fe/Ti and （Fe ＋ Mn）/Ti all explain that there were hot water activities during the sedimentary period of oil shale. In terms of Zr/Rb, paleohydrodynamics of oil shale is weak. By means of Co abundance and U/Th, paleo-water-depth of oil shale is from 17.30 to 157.26 m, reflecting sedimentary environment which is mainly in semi deep-deep lake facies. Correlation analyses between oil yield and six paleoenvironmental factors show that the oil yield of oil shale is mainly controlled by paleo-redox conditions, paleoclimate, hot water activities, and depth of water.Paleosalinity and paleohydrodynamics have an inconspicuous influence on oil yield.展开更多
As an unconventional resource, oil shale possesses abundant reserves and significant potential for industrial applications. The rational and efficient development of oil shale resources holds immense importance in red...As an unconventional resource, oil shale possesses abundant reserves and significant potential for industrial applications. The rational and efficient development of oil shale resources holds immense importance in reducing national energy demand. In-situ catalytic technology, characterized by its high efficiency, low pollution, and minimal energy consumption, represents a key direction for future oil shale development. This paper provides a comprehensive review of research progress in in-situ oil shale mining technology, oil shale pyrolysis catalysts, the pyrolysis mechanism of kerogen, and the compatibility of different heating processes and catalysts. Furthermore, the paper proposes future research directions and prospects for oil shale in-situ catalytic technology, including reservoir modification, highefficiency catalyst synthesis, injection processes, and high-efficiency heating technology. These insights serve as valuable technical references for the advancement of oil shale in-situ catalytic technology.展开更多
Fushun oil shale(FOS) was subjected to thermal dissolution(TD) under different conditions. The results show that the optimal solvent, temperature, time, and ratio of solvent to FOS are ethanol, 300 °C, 2 h, and 5...Fushun oil shale(FOS) was subjected to thermal dissolution(TD) under different conditions. The results show that the optimal solvent, temperature, time, and ratio of solvent to FOS are ethanol, 300 °C, 2 h, and 5 ml·g^(-1),respectively and the corresponding yield of the soluble portion(SP) is 32.2%(daf), which is much higher than the oil content of FOS(ca. 6%), suggesting that TD in ethanol is an excellent way to extract organics from FOS.According to 3 direct analyses, aliphatic moieties in FOS are the most abundant followed by C\\O-containing moieties and each cluster in FOS has 3 conjugated aromatic rings on average with fewer substituents. According to the analysis with a gas chromatograph/mass spectrometer, alkanes are predominant in all the SPs. A number of alkenes were identified in the SPs from the TD, while none of the alkenes were detected in acetone-SP obtained at room temperature, implying that the TD can destroy the π-π and intertwining interactions between alkenes and macromolecular structures in FOS. Moreover, a small amount of alkyl-substituted phenols and alkoxysubstituted phenols were detected in ethanol-SP from the TD, which could be the products from ethanolyzing the macromolecular moiety of FOS.展开更多
The Pabdeh Formation represents organic matter enrichment in some oil fields,which can be considered a source rock.This study is based on the Rock–Eval,Iatroscan,and electron microscopy imaging results before and aft...The Pabdeh Formation represents organic matter enrichment in some oil fields,which can be considered a source rock.This study is based on the Rock–Eval,Iatroscan,and electron microscopy imaging results before and after heating the samples.We discovered this immature shale that undergoes burial and diagenesis,in which organic matter is converted into hydro-carbons.Primary migration is the process that transports hydrocarbons in the source rock.We investigated this phenomenon by developing a model that simulates hydrocarbon generation and fluid pressure during kerogen-to-hydrocarbon conversion.Microfractures initially formed at the tip/edge of kerogen and were filled with hydrocarbons,but as catagenesis progressed,the pressure caused by the volume increase of kerogen decreased due to hydrocarbon release.The transformation of solid kerogen into low-density bitumen/oil increased the pressure,leading to the development of damage zones in the source rock.The Pabdeh Formation’s small porethroats hindered effective expulsion,causing an increase in pore fluid pressure inside the initial microfractures.The stress accumulated due to hydrocarbon production,reaching the rock’s fracture strength,further contributed to damage zone development.During the expansion process,microfractures preferentially grew in low-strength pathways such as lithology changes,laminae boundaries,and pre-existing microfractures.When the porous pressure created by each kerogen overlapped,individual microfractures interconnected,forming a network of microfractures within the source rock.This research sheds light on the complex interplay between temperature,hydrocarbon generation,and the development of expulsion fractures in the Pabdeh Formation,providing valuable insights for understanding and optimizing hydrocarbon extraction in similar geological settings.展开更多
Red mud-fly ash based cementitious material mixed with different contents of oil shale calcined at 700 ℃ is investigated in this paper. The effect of active Si and A1 content on the solidification of Na＋ during the ...Red mud-fly ash based cementitious material mixed with different contents of oil shale calcined at 700 ℃ is investigated in this paper. The effect of active Si and A1 content on the solidification of Na＋ during the hydration process is determined by using X-ray diffraction （XRD）, 27A1 and 29Si magic-angle-spinning nuclear magnetic resonance （MAS-NMR）, infrared （IR）, scanning electronic microscopy （SEM） and X-ray photoelectron spectroscopy （XPS）. It is shown that the content of oil shale has a remarkable effect on the solidified content of Na＋. The hydration process generates a highly reactive intermediate gel phase formed by co-polymerisation of individual alumina and silicate species. This kind of gel is primarily considered as 3D framework of Si04 and A104 tetrahedra interlinked by the shared oxygen atoms randomly. The negative charges and four-coordinated A1 inside the network are mainly charge-balanced by Na＋. The solidifying mechanism of Na＋ is greatly attributed to the forming of this kind of gel.展开更多
In-situ upgrading by heating is feasible for low-maturity shale oil,where the pore space dynamically evolves.We characterize this response for a heated substrate concurrently imaged by SEM.We systematically follow the...In-situ upgrading by heating is feasible for low-maturity shale oil,where the pore space dynamically evolves.We characterize this response for a heated substrate concurrently imaged by SEM.We systematically follow the evolution of pore quantity,size(length,width and cross-sectional area),orientation,shape(aspect ratio,roundness and solidity)and their anisotropy—interpreted by machine learning.Results indicate that heating generates new pores in both organic matter and inorganic minerals.However,the newly formed pores are smaller than the original pores and thus reduce average lengths and widths of the bedding-parallel pore system.Conversely,the average pore lengths and widths are increased in the bedding-perpendicular direction.Besides,heating increases the cross-sectional area of pores in low-maturity oil shales,where this growth tendency fluctuates at<300℃ but becomes steady at>300℃.In addition,the orientation and shape of the newly-formed heating-induced pores follow the habit of the original pores and follow the initial probability distributions of pore orientation and shape.Herein,limited anisotropy is detected in pore direction and shape,indicating similar modes of evolution both bedding-parallel and bedding-normal.We propose a straightforward but robust model to describe evolution of pore system in low-maturity oil shales during heating.展开更多
The Huadian Basin is an oil shale-bearing basin located in northeastern China. Thirteen oil shale layers deposited in this basin, and the characteristics of oil shale are different among these oil shale layers. Based ...The Huadian Basin is an oil shale-bearing basin located in northeastern China. Thirteen oil shale layers deposited in this basin, and the characteristics of oil shale are different among these oil shale layers. Based on the core observation and microscope identification, using the organic and inor- ganic data from borehole HD3 and outcrops, the formation conditions of different grade oil shale have been evaluated. Based on measuring oil yield （OY in short） of an oil shale to determine its grade, this paper classifies the oil shale as high grade （OY〉10%）, medium grade （10%〉OY〉5%） and low grade （5%〉OY〉3.5%）. The high grade oil shale is mainly in brown or dark brown, and the bulk density ranges from 1.59 to 1.81 g/cm3. The results of X-ray diffraction indicate the content of carbonate min- erals is 28.0%. The HI （hydrogen index）-Tmax, HI-OI （oxygen index） and S2-TOC （total organic carbon） diagrams indicate the kerogen types are I and II1. The high grade oil shale generally formed in the rela- tively arid paleoclimate, deposited in the brackish water, dysoxic environment, when the bioprodctivity is extremely high, and the information is mainly from the inorganic parameters diagrams of chemical index of alteration （CIA）, Sr/Ba and V/（V＋Ni）. The medium grade oil shale mainly shows grey-black or black-brown color and the bulk density ranges from 1.87 to 2.08 g/cm^3. The average content of carbon- ate minerals is 16.4%, far less than high grade oil shale and the kerogen type is mainly IIm. The inor- ganic parameters diagrams reflect the medium grade oil shale generally formed in the less humid pa- leoclimate, deposited in the brackish water, dysoxic to anoxic environment, when the bioproductivity is medium. The color of low grade oil shale is major in grey-black or dark grey and the bulk density ranges from 2.00 to 2.15 g/cm^3. The average content of carbonate minerals is sharply decreased and the kerogen type is mainly II1. The inorganic parameters diagrams indicate the low grade oil shale gener- ally formed in the relatively humid paleoclimate, deposited in the freshwater to brackish water, anoxic environment, when the bioproductivity is relatively low. Comprehensive study suggest the increasing precipitation caused by a relatively humid paleoclimate resulted in decreasing oxygen concentration and salinity in the bottom water, restrained the salinity stratification, and tended to form the low grade oil shale. The strong evaporation leading to relatively arid paleoclimate resulted in increasing oxygen concentration and salinity in the bottom water, and promoted the salinity stratification. The area with well preservation conditions caused by the relative high sedimentary rate and salinity stratification are favorable to high grade oil shale deposit. In summary, the bioproductivity and the paleoclimate are the main factors controlling the oil shale grade in the Huadian Basin, when the bioproductivity is relatively high and the paleoclimate is relatively arid, it is prone to form the high grade oil shale. However the low grade oil shale developed in the low bioproductivity and relatively humid paleoclimate.展开更多
基金Supported by National Natural Science Foundation of China(Nos.42372125 and 41772092)。
文摘Previous studies have shown that the Eocene oil shale sequences in the Green River Basin contain long-period astronomical age information.The fine-scale chronological characteristics of the oil shale laminae remain largely unexplored.We selected finely laminated oil shales formed in deep-water environments characterized by stable water column stratification as the primary focus of this study,using microscopy and micro-area X-ray fluorescence(μ-XRF)techniques.By integrating high-resolution elemental data with timeseries analysis,we identified significant periodic signals associated with solar activity(Hale and Schwabe cycles)and ENSO.The results indicate that the alternations of light and dark laminae in the Green River Formation oil shale correspond to alternating dry and wet climate regimes:the light laminae are dominated by carbonate minerals,reflecting drier and milder conditions,while the dark laminae are enriched in terrigenous clastics and organic matter,indicating periods of increased precipitation and warmer temperatures.The detected periodicities(23.5 years,13.3 years and 5.8 years)are highly consistent with modern observations,demonstrating that the lower Eocene Green River oil shale effectively records short-term solar activity and climate variability.Furthermore,our findings confirm that a persistent"permanent El Niño"state did not develop under Early Eocene greenhouse conditions,providing a refined chronological framework for highresolution paleoclimate studies during greenhouse intervals.
基金funded by the Open Research Fund of the State Key Laboratory for Fine Exploration and Intelligent Development of Coal Resources,China University of Mining and Technology(Grant No.SKLCRSM23KF018)the National Natural Science Foundation of China(Grant No.52104144)the National Key R&D Program of China(Grant No.2019YFA0705501).
文摘In the context of convection-heating-based in situ oil shale retorting,fractures serve as primary pathways for fluid migration and product extraction.This study investigates the permeability and microstructural evolution of oil shale during water vapor injection in single-fracture and no-fracture scenarios.Three types of oil shale are investigated:intact oil shale,oil shale with a single straight crack,and oil shale with a single hydraulic crack.With increasing water vapor temperature,the permeabilities of the intact oil shale and oil shale with a fractured crack exhibit a trend of initial increase,followed by a decrease,and then a subsequent increase.However,the permeability of oil shale with a single straight crack consistently increases and exceeds that of oil shale with a fractured crack.The temperaturedependent permeability changes in fractured oil shale-a slight decrease in fracture cracks and a gradual increase in straight cracks-mainly occur in the range of 300℃-350℃.The permeability of oil shale with a straight crack is approximately three times that of oil shale with a fractured crack.This is attributed to the retention of viscous asphaltene and the frictional resistance caused by the rough fracture structure.For the oil shale with a single crack,the crack permeability has a dominant influence on the overall permeability of the rock.The contribution of the permeability of the straight crack exceeds 94.6%,while that of the permeability of the fractured crack is greater than 86.1%.The disparity in the contribution of these two crack structures is evident at 350℃-550℃.
基金the financial support from the National Science Foundation of China(No.52374063 and No.52204065)the Natural Science Foundation of Shandong Province,China(No.ZR2023ME049 and No.ZR2021JQ18)the Fundamental Research Funds for the Central Universities,China(24CX06017A)。
文摘Simulation of thermal-reactive-compositional flow processes is fundamental to the thermal recovery of ultra-heavy hydrocarbon resources,and a typical oilfield practice is the in-situ conversion process(ICP)implemented in oil shale exploitation.However,accurately capturing the intricate flow dynamics of ICP requires a large number of fine-scale grid-blocks,which renders ICP simulations computationally expensive.Apart from that,plenty of oil shale reservoirs contain natural fractures or require hydraulic fracturing to enhance fluid mobility,creating further challenges in modeling pyrolysis reactions in both rock matrices and fractures.Targeted at the above issues,this work proposes a novel dual-model dualgrid upscaling(DDU)method specifically designed for solid-based thermal-reactive-compositional flow simulations in fractured porous media.Unlike existing upscaling techniques,the DDU method incorporates the upscaling of fracture grids using the embedded discrete fracture modeling(EDFM)approach and introduces a new concept of simplified models to approximate fine-scale results,which are used to correct reaction rates in coarse-scale grids.This method uniquely achieves efficient upscaling for both matrix and fracture grids,supports both open-source and commercial simulation platforms without modifying source codes,and is validated through 3D ICP models with natural fractures.The results indicate that the application of the DDU method can provide a close match with the fine-scale simulation results.Moreover,the DDU method has drastically improved the computational efficiency and speeded up the fine-scale simulation by 396-963 times.Therefore,the proposed DDU method has achieved marked computational savings while maintaining high simulation accuracy,which is significant for the development efficiency and production forecasting of oil shale reservoirs.
基金supported by grants from the Research Grant Council of the Hong Kong Special Administrative Region,China(Grant No.HKU 7137/03E)the National Natural Science Foundation of China(Grant No.41977248)the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDB10030100).
文摘The increasing demand for unconventional oil and gas resources,especially oil shale,has highlighted the urgent need to develop rapid and accurate strata characterization methods.This paper is the first case and examines the drilling process monitoring(DPM)method as a digital,accurate,cost-effective method to characterize oil shale reservoirs in the Ordos Basin,China.The digital DPM method provides real-time in situ testing of the relative variation in rock mechanical strength along the drill bit depth.Furthermore,it can give a refined rock quality designation based on the DPM zoning result(RQD(V_(DPM)))and a strength-grade characterization at the site.Oil shale has high heterogeneity and low strata strength.The digital results are further compared and verified with manual logging,cored samples,and digital panoramic borehole cameras.The findings highlight the innovative potential of the DPM method in identifying the zones of oil shale reservoir along the drill bit depth.The digital results provide a better understanding of the oil shale in Tongchuan and the potential for future oil shale exploration in other regions.
文摘This paper presents new geological and geochemical data from the Shuanghu area in northern Tibet, which recorded the Early Toarcian Oceanic Anoxic Event. The stratigraphic succession in the Shuanghu area consists mostly of grey to dark-colored alternating oil shales, marls and mudstones. Ammonite beds are found at the top of the Shuanghu oil shale section, which are principally of early Toarcian age, roughly within the Harplocearas falciferrum Zone. Therefore, the oil shale strata at Shuanghu can be correlated with early Toarcian black shales distributing extensively in the European epicontinental seas that contain the records of an Oceanic Anoxic Event. Sedimentary organic matter of laminated shale anomalously rich in organic carbon across the Shuanghu area is characterized by high organic carbon contents, ranging from 1.8% to 26.1%. The carbon isotope curve displays the δ 13C values of the kerogen (δ 13Ckerogen) fluctuating from –26.22 to –23.53‰ PDB with a positive excursion close to 2.17‰, which, albeit significantly smaller, may also have been associated with other Early Toarcian Oceanic Anoxic Events (OAEs) in Europe. The organic atomic C/N ratios range between 6 and 43, and the curve of C/N ratios is consistent with that of the δ 13Ckerogen values. The biological assemblage, characterized by scarcity of benthic organisms and bloom of calcareous nannofossils (coccoliths), reveals high biological productivity in the surface water and an unfavorable environment for the benthic fauna in the bottom water during the Oceanic Anoxic Event. On the basis of organic geochemistry and characteristics of the biological assemblage, this study suggests that the carbon-isotope excursion is caused by the changes of sea level and productivity, and that the black shale deposition, especially oil shales, is related to the bloom and high productivity of coccoliths.
基金the National Basic Research Program of China (973 programs, No. 2014CB744302)Taishan Scholar Constructive Engineering Foundation of Shandong province, China (No. ts20120518)
文摘Pyrolysis characteristics of a North Korean oil shale and its pyrolysates were investigated in this paper. The pyrolysis experiments were conducted below 600 ℃ at a heating rate of 10, 15, 20 and 25 ℃/min, respectively. The kinetics data were calculated using both integral and differential methods with the assumption of first order kinetics. The results show that the averaged oil content of the North Korean oil shale is about 12.1 wt% and its heat value is 13,400 kJ/kg. The oil yields at different retorting temperatures show that the higher the retorting temperature the greater the oil and retorting gas yields. The optimal retorting temperature for the North Korean oil shale is about 500 ℃. The properties of the North Korean shale oil including density, viscosity, flash point and freezing point are found to be relatively low compared with those of shale oil from FuShun, China. The gasoline fraction, diesel fraction and heavy oil fraction account for 11.5 wt%, 41.5 wt% and 47 wt%, respectively. The major pyrolysis gases are ca4 （the most abundant）, H2, CO2, H2S, CO, and C2-C5 hydrocarbons. The heat value of retorting gas is more than 900 kJ/mol, and the retorting gas has high sulfur content.
基金Supported by the National Innovative Projects with Cooperation in terms of Production,Study and Research(OSR-05)the National Science and Technology Major Projects(2008ZX05018-005)
文摘Na-A zeolite was synthesized using oil shale ash （OSA）, which is a solid by-product of oil shale proc- essing. The samples were characterized by various techniques, such as scanning electron microscopy, X-ray diffrac- tion and Brunaner Emmet Teller method. The batch isothermal equilibrium adsorption experiments were performed to evaluate the ability of Na-A zeolite for removal of Cu （II） from aqueous solutions. The effects of operating pa- rameters, such as concentration of copper solutions, adsorbent dosages, pH value of solutions and temperature, on the adsorption efficiency were investigated. The equilibrium adsorption data were fitted with Langmuir and Freundlich models. The maximum adsorption capacity of Na-A zeolite obtained from the Langmuir adsorption iso- therm is 156.7 mg.g-t of Cu （lI）. The increase of pH level in the adsorption process suggests that the uptake of heavy metals on the zeolite follows an ion exchange mechanism. The batch kinetic data fit the pseudo-second order equation well. The thermodynamic parameters, such as changes in Gibbs free energy （AG）, enthalpy （AH） and en- tropy （AS）, are used to predict the nature of the adsorption process. The negative AG values at different tempera- tures confirm that the adsorption processes are spontaneous.
基金supported by the National Natural Science Foundation of China(grants No.41102066,41572095 and 41572089)Opening Foundation of the State Key Laboratory of Ore Deposit Geochemistry,Institute of Geochemistry,Chinese Academy of Sciences(grant No.201008)State Key Laboratory of Marine Geology,Tongji University(grant No.MGK1703)
文摘The marine oil shales of the Qiangtang Basin, northern Tibet, exposed in the Biluo Co, Tuonamu, Shenglihe and Changsheshan areas are believed to be important petroleum source rocks. This work comprehensively analyzed the carbon isotopes, trace elements, and calcareous nannofosills, ammonites and bivalves of the Biluo Co section in the Qiangtang Basin. The organic carbon isotopes show a positive excursion close to 2.17‰（relative to PDB）, which, albeit significantly smaller, may also be associated with other Early Toarcian Oceanic Anoxic Events（T-OAE） in the European epicontinental seas and the Tethyan continental margins. Coinciding with the Early Toarcian transgression, the oxygen deficiency in bottom water had led to dysoxic-anoxic conditions and deposition of black shales lacking benthic fauna. Under such condition, the redox-sensitive trace metals such as Mo, V, Ni, Cr, and U were enriched, in conjunction with high planktonic productivity of Watznaueriaceae calcareous nannofossils. Comparison of the results with the records of chemo-and biostratigraphy, as well as the palaeogeography during the Early Jurassic suggests that the anoxia linked to the Early Toarcian oceanic anoxic event was mainly caused by the high surface water temperature, sea-level rise and an increase of surface water productivity.
基金Projects(41173055,41772118)supported by the National Natural Science Foundation of China
文摘Based on the element geochemistry and biomarkers of the oil shale from the Chang 7 sub-unit in the southern Ordos Basin,the depositional conditions and organic source of the oil shale are discussed.Biomarkers analyses show that the oil shale has a homologous organic matter source,with a mix of plankton and advanced plants.U/Th and V/Ni ratios suggest that the redox condition is dominated by a reducing condition,and the degree of anoxia in the Tongchuan area is higher than that of the Xunyi area.Sr/Ba ratios illustrate that the oil shale is deposited in fresh water and the paleosalinity in the Tongchuan area is slightly higher.Fe/Ti ratios imply that the Tongchuan area underwent obvious hydrothermal fluid activities.Sr/Cu ratios show warm and humid paleoclimate in both areas.As assessed by(La/Yb)NASC,the deposition rate in the Tongchuan area is relatively lower.Fe/Co and Th/U ratios suggest that the paleo-water-depth in the Tongchuan area is deeper.The source rock could have the advance plants source,which must have close relationship with the Qinling orogeny.Comparing the paleoenvironment,the Tongchuan area has better depositional conditions,and is the key oil shale exploration area in the southern Ordos Basin.
基金supported by funding from the National Natural Science Foundation of China (No.41173055)the Fundamental Research Funds for the Central Universities (No.310827172101)
文摘Using trace elements to reconstruct paleoenvironment is a current hot topic in geochemistry. Through analytical tests of oil yield, ash yield, calorific value, total sulfur, major elements, trace elements, and X-ray diffraction, the quality, mineral content, occurrence mode of elements, and paleoenvironment of the Zhangjiatan oil shale of the Triassic Yanchang Formation in the southern Ordos Basin were studied. The analyses revealed relatively high oil yield(average 6.63%) and medium quality. The mineral content in the oil shale was mainly clay minerals,quartz, feldspar, and pyrite; an illite–smectite mixed layer comprised the major proportion of clay minerals. Compared with marine oil shale in China, the Zhangjiatan oil shale had higher contents of quartz, feldspar, and clay minerals, and lower calcite content. Silica was mainly in quartz and Fe was associated with organic matter, which is different from marine oil shale. The form of calcium varied. Cluster analyses indicated that Fe, Cu, U, V, Zn, As,Cs, Cd, Mo, Ga, Pb, Co, Ni, Cr, Sc, P, and Mn are associated with organic matter while Ca, Na, Sr, Ba, Si, Zr, K,Al, B, Mg, and Ti are mostly terrigenous. Sr/Cu, Ba/Al, V/(V+ Ni), U/Th, AU, and δU of oil shale samples suggest the paleoclimate was warm and humid, paleoproductivity of the lake was relatively high during deposition of the shale—which mainly occurred in fresh water—and the paleo-redox condition was dominated by reducing conditions. Fe/Ti ratios of the oil shale samples suggest clear hydrothermal influence in the eastern portion of the study area and less conspicuous hydrothermal influence in the western portion.
基金financial support from the National Science and Technology Major Project of China(Grant No. 2008ZX05018)Taishan Scholar Constructive Engineering Foundation of Shandong province(No. ts20120518)
文摘A study of reaction mechanisms and chemical kinetics of pressurized pyrolysis of Chinese Liushuhe oil shale in the presence of water were conducted using an autoclave for simulating and modeling in-situ underground thermal degradation.It was found that the oil shale was first pyrolyzed to form pyrobitumen,shale oil,shale gas and residue,then the pyrobitumen was further pyrolyzed to form more shale oil,shale gas,and residue.It means that there are two consecutive and parallel reactions.With increasing temperature,the pyrobitumen yield,as intermediate,first reached a maximum,then decreased to approximately zero.The kinetics results show that both these reactions are first order.The activation energy of pyrobitumen formation from oil shale is lower than that of shale oil formation from pyrobitumen.
基金Project CPEUKF08-04 support by the Key Laboratory of Coal Processing and Efficient Utilization, Ministry of Education of China
文摘Thermo-gravimetric-analysis(TGA) was used to analyze the combustion characteristics of an oil shale and semi-cokes prepared from it.The effect of prior pyrolysis and TGA heating rate on the combustion process was studied.Prior pyrolysis affects the initial temperature of mass loss and the ignition temperature.The ignition temperature increases as the volatile content of the sample decreases.TG/DTG curves obtained at different heating rates show that heating rate has little effect on ignition temperature.But the peak of combustion shifts to higher temperatures as the heating rate is increased.The Coats-Redfern integration method was employed to find the combustion-reaction kinetic parameters for the burning of oil shale and oil shale semi-coke.
基金financial support offered by the National Key R&D Program of China(Grant No.2019YFA0705502,Grant No.2019YFA0705501)the National Natural Science Fund Project of China(Grant No.4210020395)+1 种基金the China Postdoctoral Science Foundation(Grant No.2021M700053)Technology Development Plan Project of Jilin Province(Grant No.20200201219JC).
文摘The autothermic pyrolysis in-situ conversion process (ATS) consumes latent heat of residual organic matter after kerogen pyrolysis by oxidation reaction, and it has the advantages of low development cost and exploitation of deep oil shale resources. However, the heating mechanism and the characteristic of different reaction zones are still unclear. In this study, an ATS numerical simulation model was proposed for the development of oil shale, which considers the pyrolysis of kerogen, high-temperature oxidation, and low-temperature oxidation. Based on the above model, the mechanism of the ATS was analyzed and the effects of preheating temperature, O_(2) content, and injection rate on recovery factor and energy efficiency were studied. The results showed that the ATS in the formation can be divided into five characteristic zones by evolution of the oil and O_(2) distribution, and the solid organic matter, including residue zone, autothermic zone, pyrolysis zone, preheating zone, and original zone. Energy efficiency was much higher for the ATS than for the high-temperature nitrogen injection in-situ conversion process (HNICP). There is a threshold value of the preheating temperature, the oil content, and the injection rate during the ATS, which is 400 °C, 0.18, and 1100 m3/day, respectively, in this study.
基金supported with funding from the National Natural Science Foundation of China (No. 41173055)the Fundamental Research Funds for the Central Universities (No. 310827172101)
文摘As an important unconventional resource, oil shale has received widespread attention. The oil shale of the Chang 7 oil layer from Triassic Yanchang Formation in Ordos Basin represents the typical lacustrine oil shale in China. Based on analyzing trace elements and oil yield from boreholes samples, characteristics and paleo-sedi- mentary environments of oil shale and relationship between paleo-sedimentary environment and oil yield were studied. With favorable quality, oil yield of oil shale varies from 1.4% to 9.1%. Geochemical data indicate that the paleo-redox condition of oil shale＇s reducing condition from analyses of V/Cr, V/（V ＋ Ni）, U/Th, δU, and authi genic uranium. Equivalent Boron, Sp, and Sr/Ba illustrate that paleosalinity of oil shale is dominated by fresh water. The paleoclimate of oil shale is warm and humid by calculating the chemical index of alteration and Sr/Cu. Fe/Ti and （Fe ＋ Mn）/Ti all explain that there were hot water activities during the sedimentary period of oil shale. In terms of Zr/Rb, paleohydrodynamics of oil shale is weak. By means of Co abundance and U/Th, paleo-water-depth of oil shale is from 17.30 to 157.26 m, reflecting sedimentary environment which is mainly in semi deep-deep lake facies. Correlation analyses between oil yield and six paleoenvironmental factors show that the oil yield of oil shale is mainly controlled by paleo-redox conditions, paleoclimate, hot water activities, and depth of water.Paleosalinity and paleohydrodynamics have an inconspicuous influence on oil yield.
基金financially supported by the National Natural Science Foundation of China(52174047)Sinopec Project(P21063-3)。
文摘As an unconventional resource, oil shale possesses abundant reserves and significant potential for industrial applications. The rational and efficient development of oil shale resources holds immense importance in reducing national energy demand. In-situ catalytic technology, characterized by its high efficiency, low pollution, and minimal energy consumption, represents a key direction for future oil shale development. This paper provides a comprehensive review of research progress in in-situ oil shale mining technology, oil shale pyrolysis catalysts, the pyrolysis mechanism of kerogen, and the compatibility of different heating processes and catalysts. Furthermore, the paper proposes future research directions and prospects for oil shale in-situ catalytic technology, including reservoir modification, highefficiency catalyst synthesis, injection processes, and high-efficiency heating technology. These insights serve as valuable technical references for the advancement of oil shale in-situ catalytic technology.
基金Supported by the Fundamental Research Funds for the Central Universities(2017BSCXB27)the Research and the Postgraduate Research&Practice Innovation Program of Jiangsu Province(KYCX17_1507)
文摘Fushun oil shale(FOS) was subjected to thermal dissolution(TD) under different conditions. The results show that the optimal solvent, temperature, time, and ratio of solvent to FOS are ethanol, 300 °C, 2 h, and 5 ml·g^(-1),respectively and the corresponding yield of the soluble portion(SP) is 32.2%(daf), which is much higher than the oil content of FOS(ca. 6%), suggesting that TD in ethanol is an excellent way to extract organics from FOS.According to 3 direct analyses, aliphatic moieties in FOS are the most abundant followed by C\\O-containing moieties and each cluster in FOS has 3 conjugated aromatic rings on average with fewer substituents. According to the analysis with a gas chromatograph/mass spectrometer, alkanes are predominant in all the SPs. A number of alkenes were identified in the SPs from the TD, while none of the alkenes were detected in acetone-SP obtained at room temperature, implying that the TD can destroy the π-π and intertwining interactions between alkenes and macromolecular structures in FOS. Moreover, a small amount of alkyl-substituted phenols and alkoxysubstituted phenols were detected in ethanol-SP from the TD, which could be the products from ethanolyzing the macromolecular moiety of FOS.
文摘The Pabdeh Formation represents organic matter enrichment in some oil fields,which can be considered a source rock.This study is based on the Rock–Eval,Iatroscan,and electron microscopy imaging results before and after heating the samples.We discovered this immature shale that undergoes burial and diagenesis,in which organic matter is converted into hydro-carbons.Primary migration is the process that transports hydrocarbons in the source rock.We investigated this phenomenon by developing a model that simulates hydrocarbon generation and fluid pressure during kerogen-to-hydrocarbon conversion.Microfractures initially formed at the tip/edge of kerogen and were filled with hydrocarbons,but as catagenesis progressed,the pressure caused by the volume increase of kerogen decreased due to hydrocarbon release.The transformation of solid kerogen into low-density bitumen/oil increased the pressure,leading to the development of damage zones in the source rock.The Pabdeh Formation’s small porethroats hindered effective expulsion,causing an increase in pore fluid pressure inside the initial microfractures.The stress accumulated due to hydrocarbon production,reaching the rock’s fracture strength,further contributed to damage zone development.During the expansion process,microfractures preferentially grew in low-strength pathways such as lithology changes,laminae boundaries,and pre-existing microfractures.When the porous pressure created by each kerogen overlapped,individual microfractures interconnected,forming a network of microfractures within the source rock.This research sheds light on the complex interplay between temperature,hydrocarbon generation,and the development of expulsion fractures in the Pabdeh Formation,providing valuable insights for understanding and optimizing hydrocarbon extraction in similar geological settings.
基金the National Natural Science Foundation of China(Nos.51034008 and 51104008)the China Postdoctoral Science Foundation Funded Project(No.20100480202)+1 种基金the Research Fund for the Doctoral Program of Higher Education of China(No.20100006120010)the Fundamental Research Funds for the Central Universities of China (No.FRF-TP-12-026A)
文摘Red mud-fly ash based cementitious material mixed with different contents of oil shale calcined at 700 ℃ is investigated in this paper. The effect of active Si and A1 content on the solidification of Na＋ during the hydration process is determined by using X-ray diffraction （XRD）, 27A1 and 29Si magic-angle-spinning nuclear magnetic resonance （MAS-NMR）, infrared （IR）, scanning electronic microscopy （SEM） and X-ray photoelectron spectroscopy （XPS）. It is shown that the content of oil shale has a remarkable effect on the solidified content of Na＋. The hydration process generates a highly reactive intermediate gel phase formed by co-polymerisation of individual alumina and silicate species. This kind of gel is primarily considered as 3D framework of Si04 and A104 tetrahedra interlinked by the shared oxygen atoms randomly. The negative charges and four-coordinated A1 inside the network are mainly charge-balanced by Na＋. The solidifying mechanism of Na＋ is greatly attributed to the forming of this kind of gel.
基金financially supported by the National Key Research and Development Program of China(Grant No.2022YFE0129800)the National Natural Science Foundation of China(Grant No.42202204)。
文摘In-situ upgrading by heating is feasible for low-maturity shale oil,where the pore space dynamically evolves.We characterize this response for a heated substrate concurrently imaged by SEM.We systematically follow the evolution of pore quantity,size(length,width and cross-sectional area),orientation,shape(aspect ratio,roundness and solidity)and their anisotropy—interpreted by machine learning.Results indicate that heating generates new pores in both organic matter and inorganic minerals.However,the newly formed pores are smaller than the original pores and thus reduce average lengths and widths of the bedding-parallel pore system.Conversely,the average pore lengths and widths are increased in the bedding-perpendicular direction.Besides,heating increases the cross-sectional area of pores in low-maturity oil shales,where this growth tendency fluctuates at<300℃ but becomes steady at>300℃.In addition,the orientation and shape of the newly-formed heating-induced pores follow the habit of the original pores and follow the initial probability distributions of pore orientation and shape.Herein,limited anisotropy is detected in pore direction and shape,indicating similar modes of evolution both bedding-parallel and bedding-normal.We propose a straightforward but robust model to describe evolution of pore system in low-maturity oil shales during heating.
基金financially supported by the Ministry of Land Resources National Department Public Benefit Research Foundation(No.201211051-04)the National Natural Science Foundation of China(No.41302075)+2 种基金the Specialized Research Fund for the Doctoral Program of Higher Education(No.20110061110050)the Graduate Innovation Fund of Jilin University(No.2014027)the support of the Opening Foundation of Key Laboratory for Oil Shale and Paragenetic Energy Minerals,Jilin Province
文摘The Huadian Basin is an oil shale-bearing basin located in northeastern China. Thirteen oil shale layers deposited in this basin, and the characteristics of oil shale are different among these oil shale layers. Based on the core observation and microscope identification, using the organic and inor- ganic data from borehole HD3 and outcrops, the formation conditions of different grade oil shale have been evaluated. Based on measuring oil yield （OY in short） of an oil shale to determine its grade, this paper classifies the oil shale as high grade （OY〉10%）, medium grade （10%〉OY〉5%） and low grade （5%〉OY〉3.5%）. The high grade oil shale is mainly in brown or dark brown, and the bulk density ranges from 1.59 to 1.81 g/cm3. The results of X-ray diffraction indicate the content of carbonate min- erals is 28.0%. The HI （hydrogen index）-Tmax, HI-OI （oxygen index） and S2-TOC （total organic carbon） diagrams indicate the kerogen types are I and II1. The high grade oil shale generally formed in the rela- tively arid paleoclimate, deposited in the brackish water, dysoxic environment, when the bioprodctivity is extremely high, and the information is mainly from the inorganic parameters diagrams of chemical index of alteration （CIA）, Sr/Ba and V/（V＋Ni）. The medium grade oil shale mainly shows grey-black or black-brown color and the bulk density ranges from 1.87 to 2.08 g/cm^3. The average content of carbon- ate minerals is 16.4%, far less than high grade oil shale and the kerogen type is mainly IIm. The inor- ganic parameters diagrams reflect the medium grade oil shale generally formed in the less humid pa- leoclimate, deposited in the brackish water, dysoxic to anoxic environment, when the bioproductivity is medium. The color of low grade oil shale is major in grey-black or dark grey and the bulk density ranges from 2.00 to 2.15 g/cm^3. The average content of carbonate minerals is sharply decreased and the kerogen type is mainly II1. The inorganic parameters diagrams indicate the low grade oil shale gener- ally formed in the relatively humid paleoclimate, deposited in the freshwater to brackish water, anoxic environment, when the bioproductivity is relatively low. Comprehensive study suggest the increasing precipitation caused by a relatively humid paleoclimate resulted in decreasing oxygen concentration and salinity in the bottom water, restrained the salinity stratification, and tended to form the low grade oil shale. The strong evaporation leading to relatively arid paleoclimate resulted in increasing oxygen concentration and salinity in the bottom water, and promoted the salinity stratification. The area with well preservation conditions caused by the relative high sedimentary rate and salinity stratification are favorable to high grade oil shale deposit. In summary, the bioproductivity and the paleoclimate are the main factors controlling the oil shale grade in the Huadian Basin, when the bioproductivity is relatively high and the paleoclimate is relatively arid, it is prone to form the high grade oil shale. However the low grade oil shale developed in the low bioproductivity and relatively humid paleoclimate.
