High Total Organic Content Research Articles

Hydrogen adsorption kinetics in organic-Rich shale reservoir rocks for seasonal geological storage

The geo-storage of hydrogen (H2) is essential for advancing a robust and industrial-scale H2-based economy. The efficient H2 storage in a geological formation depends on the presence of a secure and impermeable caprock, such as a shale formation. However, the existing literature lacks information on the kinetics of H2 adsorption in actual shale formations with diverse organic contents and mineral compositions. Therefore, the kinetics of H2 adsorption in organic-rich shale samples from a Jordanian oil (JO) source rock formation are experimentally investigated herein at various temperatures (193, 273, 303, and 333 K) and two equilibrium pressures (15 and 45 bar) by using a volumetric method. The impact of mineral compositions and total organic content (TOC) on H2 adsorption is studied using two samples with distinct mineralogy and TOC values. Thermodynamic calculations are performed, and common adsorption models are used to analyze the experimental data. The results indicate that the H2 adsorption rate increases with pressure and decreases with temperature, being characterized by an initial rapid adsorption phase followed by a slower adsorption period as the uptake of H2 approaches equilibrium. More interestingly, the rate of H2 adsorption is higher in the sample with a high TOC and a richer composition of carbonate minerals. Both the applied adsorption isotherm models and adsorption kinetics models fit the experimental data remarkably well, thereby indicating their suitability for analyzing the kinetics of H2 adsorption in the JO shale. The unipore model matches the H2 kinetics data well, with R2 > 0.91. The H2 diffusion coefficient increases with pressure and temperature, where the H2 diffusion in shale accelerates with thermal motion intensity. This study provides fundamental insights into the adsorption kinetics of H2 and is expected to assist in implementing an industrial H2-based economy.

Is it necessary to increase the maize planting density in China?

Increasing the maize planting density is considered a potential approach for increasing the grain yield in China, but there is no consensus regarding its yield-increasing effect and the influence of specific factors. Thus, we established a database (2721 pairs of data from 187 publications) to quantify the effects of increasing the maize planting density on the phenotypic traits and yield, to determine an appropriate maize planting density for each planting area, and to quantify the effects of environmental factors and agricultural imputs on the outcomes of increasing the planting density. We found that increasing the planting density increased the individual competition among maize plants, with negative effects on their growth, but the grain yield increased by 11.18–13.43 % due to the increased population biomass. Using the database, we found large differences in the optimal density and peak grain yield among maize planting areas, and the factors that caused these differences were analyzed based on subgroup analysis. Field management practices significantly influenced the outcomes of increasing the planting density. In particular, higher agricultural inputs (irrigation amount, and nitrogen and phosphorus application rates) enhanced the positive effect of increasing plant density on the optimal plant density and peak grain yield. In addition, the effects of increasing the planting density were significantly influenced by environmental (climate and soil) factors. When the mean annual temperature was 7–14°C and the mean annual precipitation was 400–800 mm, the yield and maximum peak yield were highest in relatively fertile (high total nitrogen, available nitrogen, and soil organic matter contents) and neutral (pH 6–8) soils. Our results highlight the need to increase the current maize planting density and provide a scientific basis for determining reasonable planting densities for different maize growing areas in China.

Factors controlling organic matter accumulation in the Longmaxi Formation shale, Changning area, South Sichuan Basin

Based on total organic content (TOC) tests and major-trace element test data, this study examined organic matter accumulation and controlling factors of the Longmaxi Formation shale in the Changning area, southern Sichuan Basin. The results showed that (1) TOC content of the Long11 submember (S1l11) shale was between 0.46% and 8.35%. Vertically, TOC revealed a ‘sandwich cake’ pattern with a high TOC content concentrated in the 1st layers of Long11 submember (S1l11–1) and 3rd layers of Long11 submember (S1l11–3) and a lower TOC content in the 2nd layers of Long11 submember (S1l11–2) and 4th layers of Long11 submember (S1l11–4). Spatial distribution of TOC showed variations and migration in S1l11. (2) S1l11 shale TOC showed a logarithmic correlation with sedimentary environment index, negative correlation with terrigenous influx, and complex correlation with paleoproductivity. (3) Factors controlling organic matter accumulation were mainly redox conditions, followed by paleoproductivity and terrigenous input in Changning area. When the paleoproductivity index (Babio) was less than 2200 μg/g, the redox conditions was the controlling factor of organic matter accumulation. On the contrary, it is ultrahigh paleoproductivity. Vertically, organic matter accumulation mode evolved from “preservation conditions” to “productivity–preservation conditions synergy mode” to “productivity mode”. (4) An anoxic condition was the basis of organic matter accumulation. Medium–high paleoproductivity was the key to organic matter accumulation. These study results are expected to contribute to shale gas exploration and development.

Quantitative Characteristics of Micro Bedding Fractures in the Wufeng–Longmaxi Formation Based on High-Resolution Map Imaging Technology

The study of microfractures in shale is mainly based on qualitative description. Conversely, quantitative description of the parameters of shale microfractures can provide a quantitative basis for shale fracture characterization and shale physical properties. Nine shale reservoir samples of the Wufeng–Longmaxi Formation in the Jiaoshiba area were studied, using the backscattered two-dimensional multiscale resolution imaging technology, combined with high-resolution map imaging technology (MAPS), and thousands of images were obtained using scanning electron microscopy. Gray image analysis was used to extract microfracture information from images (2 × 2 cm multiresolution). The “maximum circle method” was used to calculate the length and aperture characteristics of the fractures. Parameters such as the area of the bedding fractures, the surface rate of the fractures, and the linear density of the fractures were obtained by the integration of apertures. The fracture length was between 2~7 mm, the aperture was between 1~6 μm, the linear density was between 1~6/m and the surface rate was 1%. The bedding fractures do not contribute much to the porosity of the shale reservoir; however, shale reservoirs with high porosity have a high development of bedding fractures and good permeability. The development of a bedding fracture is controlled by the lithology within shale reservoirs. Different types of lithology contain different bedding fractures, but they have a certain regularity. Moreover, the content of organic matter and TOC (total organic content) in the shale reservoir control the development of a bedding fracture, where a high organic and TOC content are accompanied by a high number of fractures.

Evaluation of bioenergy production and material flow in treating Japanese concentrated Johkasou sludge using high-solid anaerobic membrane bioreactor based on one-year operation

The treatment of waste sludge generated from on-site wastewater treatment facilities (Johkasou) applied extensively in Japan is a key concern. In this study, a high-solid anaerobic membrane bioreactor (AnMBR) was continuously operated throughout a year to investigate the bioenergy production, material flow and seasonal impacts of concentrated Johkasou sludge (CJoS). The CJoS has higher carbon-to-nitrogen ratio and lipid fraction, but less proteins than waste activated sludge (WAS). The biogas yield of CJoS by AnMBR ranged from 0.47 to 0.52 L/g-VSfed, which was higher than the anaerobic digestion of WAS and lower than mixed sewage sludge from centralized wastewater treatment facilities. The greatest biogas production rate was observed during summer (0.63 L/L/d), owing to the high total organic and solid content. However, winter CJoS had the highest biogas yield and carbon conversion rate owing to the conservation of soluble organic matter in low temperature and high digestibility. The material flow results revealed that 46.5–52.4% total COD and 50.2–58.0% carbon was converted to biogas. The energy recovery rates ranged from 8.69 to 9.96 kJ/g-VSfed and the system energy self-sufficiency rates ranged from 1.92 to 3.02. The optimal dewaterability of digested sludge was achieved when polyamidine flocculant dosage was 30 mg/g-MLSS and the corresponding sludge specific resistance to filtration was 2.26 × 1012 m/kg. The results demonstrated that AnMBR yielded high energy conversion efficiency without co-digestion and pretreatment processing.

Unconventional shale gas potential of lower visean organic-rich formations in Glynsko-Solohivskyi petroleum region

Exploration of unconventional gas resources in Ukraine is highly relevant and important for achievement energy independence of Ukraine and Europe. Production of current oil & gas fields and alternative energy resources are not able to cover our needs nowadays. Now we can not fully fill these gaps by energy resources. In this article geological environments, age, mineralogy composition and maturity of unconventional shale and carbonate gas reservoirs of Lower Visean in one of the biggest field of Dnipro-Donets Basin (DDB) were studied. The hydrocarbon potential of two main target horizons V-23 and V-24-25 by using integrated approach of analyzing available core analysis data were performed. The results of the geochemical analysis show that the maturity level of shale of the Rudov beds (V-23) appear in oil window (Ro~0.8%) which can generate oil in the early mature phase. Visean carbonates (V-24-25) have the similar level of maturity - (Ro~0.77%). Target rocks are characterized by high total organic content (TOC): average values vary from 2% for organic-rich carbonates to 5.6% for shales which indicates relatively good to excellent source rock generative potential. According to X-ray diffraction analyses (XRD) of black shale formation domination of silica minerals (54.6%), calcite and clays (25.6%) with minor amounts of albite, feldspar and pyrite were observed. Carbonate platform V-24-25 logically is characterized by much higher calcite content of 52.2 % with low amount of dolomite – 5.5%. Quite high quartz content is also observed – average value is of about 30.7%. Clay minerals are not identified in every sample, but average values are of about 18.9%, pyrite content – 6.8%. It shows that Visean target formation of Glynsko-Solohivsky Petroleum region is characterized by anoxic environment. This data verified that V-23 and V-24-25 horizons are the brittle formations and favorable for multistage fracking. Thin section analysis confirms our results from mineralogical point of view. The presence of fractures in core samples is additional indicator for hydraulic fracturing and producing gas from such unconventional reservoirs. As a conclusion, the Lower Visean organic-rich formations V-23 and V-24-25 from Glynsko-Solohivsky Petroleum region are mature, are characterized by a high content of organic carbon, have enough thickness (30-120 m) and large areal extent. They should be regarded as a potential shale gas target.

Applications of Differential Effective Medium (DEM)-Driven Correlations to Estimate Elastic Properties of Jafurah Tuwaiq Mountain Formation (TMF)

Organic-rich mud rocks are being developed on a large scale worldwide, including in the Middle East. The Jurassic Tuwaiq Mountain Formation (TMF) in the Jafurah Basin is a potential world-class unconventional play. Based on a petrophysical evaluation of the Jafurah basin, the TMF exhibits exceptional and unconventional gas characteristics, such as a high total organic content (TOC) and low clay content. Additionally, the TMF is in the appropriate maturity window, indicating that it has reached the required level of thermal maturity to generate hydrocarbons. Plans for the development of the Jafurah unconventional field use multistage hydraulic fracturing technology. The elastic properties of the shale formation, particularly its Young’s modulus and Poisson’s ratio, dictate how the rock responds to stress and deformation. These properties strongly impact the growth of hydraulic fractures in shale formations. Without a comprehensive understanding of the elastic properties, predicting the bulk mechanical response of the target zones and surrounding layers would be challenging. Therefore, this study aims to predict the elastic characteristics of the Jafurah shale play considering the variations in carbonate facies, the kerogen volume fraction, and the pore’s geometry. Petrophysical and XRD data were used to estimate the elastic properties of various tiers (geological units) of the TMF (Tiers 1, 2, and 3). Inclusion-based, differential effective medium (DEM) rock physics models were used to estimate the formation’s elastic and velocity properties as a function of the kerogen volume fraction and the pore’s geometry. The results showed that the Young’s modulus as well as the mineral and elastic brittleness indices increase as the volume fraction of calcite increases. At the same time, they decrease due to intensified clay and kerogen volumes. The effect of the TMF’s elastic parameters on the rock brittleness behavior was also investigated by considering the formation’s mineralogy, as well as clay and kerogen contents. The results led to the development of physics-based correlations of the mineral brittleness index as function of the Young’s modulus and Poisson’s ratio for various tiers of the TMF.

The Impact of Formation Anisotropy and Stresses on Fractural Geometry—A Case Study in Jafurah’s Tuwaiq Mountain Formation (TMF), Saudi Arabia

Multi-stage hydraulic fracturing (MsHF) is the main technology to improve hydrocarbon recovery from shale plays. Associated with their rich organic contents and laminated depositional environments, shales exhibit transverse isotropic (TI) characteristics. In several cases, the lamination planes are horizontal in shale formations with a symmetric axis that are vertical to the bedding plane; hence, shale formations are known as transverse isotropic vertical (TIV) rocks. Ignoring the TIV nature of shale formations leads to erroneous estimates of in situ stresses and consequently to inefficient designs of fractural geometry, which negatively affects the ultimate recovery. The goal of this study is to investigate the effects of TIV medium characteristics on fractural geometry, spacing, and stress shadow development in the Jurassic Tuwaiq Mountain formation (TMF) in the Jafurah basin, which is a potential unconventional world-class play. This formation is the main source for prolific Jurassic oil reservoirs in Saudi Arabia. On the basis of a petrophysical evaluation in the Jafurah basin, TMF exhibited exceptional unconventional gas characteristics, such as high total organic content (TOC) and low clay content, and it was in the proper maturity window for oil and gas generation. The unconventional Jafurah field covers a large area that is comparable to the size of the Eagle Ford shale play in South Texas, and it is planned for development through multi-stage hydraulic fracturing technology. In this study, analytical modeling was performed to estimate the fractural geometry and in situ stresses in the anisotropic medium. The results show that the Young’s modulus anisotropy had a noticeable impact on fractural width, whereas the impact of Poisson’s ratio was minimal. Moreover, we investigated the impact of stress anisotropy and other rock properties on the stress shadow, and found that a large stress anisotropy could result in fractures being positioned close to one another or theoretically without minimal fractural spacing concerns. Additionally, we estimated the fractural aspect ratio in different propagation regimes and observed that the highest aspect ratio had occurred in the fractural toughness-dominated regime. This study also compares the elastic properties and confirms that TMF exhibited greater anisotropic properties than those of Eagle Ford. These findings have practical implications for field operations, particularly with regard to the fractural geometry and proppant placement.

Effect of varying thickness properties of the slow release fertilizer films on morphology, biodegradability, urea release, soil health, and plant growth.

Green biomass is a renewable and biodegradable material that has the potential use to trap urea to develop a high-efficiency urea fertilizer for crops' better performance. Current work examined the morphology, chemical composition, biodegradability, urea release, soil health, and plant growth effects of the SRF films subjected to changes in the thickness of 0.27, 0.54, and 1.03 mm. The morphology was examined by Scanning Electron Microscopy, chemical composition was analyzed by Infrared Spectroscopy, and biodegradability was assessed through evolved CO2 and CH4 quantified through Gas Chromatography. The chloroform fumigation technique was used for microbial growth assessment in the soil. The soil pH and redox potential were also measured using a specific probe. CHNS analyzer was used to calculate the total carbon and total nitrogen of the soil. A plant growth experiment was conducted on the Wheat plant (Triticum sativum). The thinner the films, the more they supported the growth and penetration of the soil's microorganisms mainly the species of fungus possibly due to the presence of lignin in films. The fingerprint regions of the infrared spectrum of SRF films showed all films in soil changed in their chemical composition due to biodegradation but the increase in the thickness possibly provides resistance to the films' losses. The higher thickness of the film delayed the rate and time for biodegradation and the release of methane gas in the soil. The 1.03 mm film (47% in 56 days) and 0.54 mm film (35% in 91 days) showed the slowest biodegradability as compared to the 0.27 mm film with the highest losses (60% in 35 days). The slow urea release is more affected by the increase in thickness. The Korsymer Pappas model with release exponent value of < 0.5 explained the release from the SRF films followed the quasi-fickian diffusion and also reduced the diffusion coefficient for urea. An increase in the pH and decrease in the redox potential of the soil is correlated with higher total organic content and total nitrogen in the soil in response to amending SRF films with variable thickness. Growth of the wheat plant showed the highest average plant length, leaf area index and grain per plant in response to the increase in the film's thickness. This work developed an important knowledge to enhance the efficiency of film encapsulated urea that can better slow the urea release if the thickness is optimized.

A calculation model for shale reservoir matrix apparent permeability considering different shale lithofacies through 2D digital core

Permeability is an important parameter affecting shale gas development. Shale has strong heterogeneity, and the permeabilities of the shale matrices in different lithofacies vary significantly. To study the seepage ability of shale matrices, the seepage of gas in the shale matrices of different lithofacies was simulated, the permeabilities of the shale matrices of different lithofacies were calculated, and the results were corrected according to the slippage and diffusion effect of shale gas. The calculation results show that the seepage capacities of clay shale with high total organic content and siliceous shale with high total organic content are stronger than those of other shale lithofacies. Finally, based on the permeability and proportion of different lithofacies, a calculation model of the apparent permeability of a shale reservoir considering different shale lithofacies was established. The calculation model of the apparent permeability of the shale reservoir matrix overcomes the spatial limitation of conventional methods. The calculation model can not only intuitively show the control effects of different shale lithofacies on reservoir permeability, but also master the seepage capacity of shale reservoirs in the research block as a whole. The model provides a theoretical basis for the design of shale gas development programmes.

Geochemical study of Mississippian to Pennsylvanian Namurian Shale in the Namur Synclinorium and Campine Basin (Belgium and S-Netherlands): Implication for paleo-redox reconstruction and organic matter characteristics

The Variscan foreland basin in Belgium and the Netherlands (Namur Synclinorium and Campine Basin) possesses potential targets for shale gas exploration based on the presence of Mississippian to Pennsylvanian Namurian black shales. Organic carbon and nitrogen contents and isotope data, major and trace element analysis, petrographic analysis, Rock-Eval pyrolysis, and basin modeling were carried out on a large sample set from 5 wells in the above-mentioned study area. Carbonate-dominated, silica-dominated, and quartz-rich mudstones with dominant type II kerogen were deposited within distal positions close to the basin floor while clay-rich, carbonate-rich, and silt-rich mudstones with mixed type II and III kerogens reflect depositional conditions at more proximal positions close to the basin margin. Sedimentary rocks were deposited in redox-stratified marine environments. Oxygen depleted environments occurred during the early Namurian A age, especially at distal depositional positions in contrast to elevated oxygenated environments during the late Namurian A age, especially at more proximal positions. From distal positions to proximal positions, redox conditions changed from mainly euxinic to anoxic conditions with some dysoxic episodes to mainly anoxic to dysoxic conditions with a few oxic episodes. The variation in δ15Nbulk values in the Namur Synclinorium suggests that N2-fixation dominated in anoxic environments during the early Namurian A age while nitrification, denitrification, and anammox in the water column dominated in anoxic to dysoxic environments with oxic episodes during the late Namurian A age. In the Campine Basin, denitrification and anammox dominated in anoxic to dysoxic environments during the early Namurian A age while N2-fixation dominated in anoxic environments at distal positions and nitrification dominated in dysoxic to oxic environments at proximal positions during the late Namurian A age. Namurian A mudstones are overmature with higher maturity in the Campine Basin than in the Namur Synclinorium. They display low potential for petroleum and gas generation based on Rock-Eval results. Basin modeling results indicate that the thermal maturity of Namurian A mudstones already reached its main phase of dry gas generation with overmature conditions during the Pennsylvanian in the Namur Synclinorium and the southern Campine Basin. In the northern Campine Basin corresponding to a depositional setting further away from the Variscan mountains, however, these sedimentary rocks became overmature during the Jurassic. Conversion of all type II kerogen to petroleum and dry gas occurred during increasing burial depth and thermal maturity. This left only overmature, hydrogen-poor kerogen remaining in the mudstones. The western Namur Synclinorium is regarded as the most prospective exploration area with high gas generation and storage potential as well as good hydraulic fracturing potential in terms of very high total organic matter content, large shale thickness, and high amount of brittle mineral contents. The Campine Basin is a secondary target with more limited gas generation and storage capacity, based on the moderate to high total organic matter content, the limited thickness of the mudstone interval, and limited brittle mineral contents.

Stable isotope record of Triceratops from a mass accumulation (Lance Formation, Wyoming, USA) provides insights into Triceratops behaviour and ecology

Our understanding of Late Cretaceous dinosaur ecosystems from North America has considerably improved through stable isotope analyses on fossil bones and teeth. Oxygen and carbon stable isotopic compositions of structurally-bound carbonate in these fossil apatites are commonly used to infer variations of ingested water and food sources, which are in turn related to environmental and climatic conditions. Incremental isotopic records potentially provide insights into seasonality and migratory behaviour. So far, these reconstructions are based on vertebrate remains from spatiotemporally diverse datasets. Here, we present oxygen (δ18O) and carbon (δ13C) isotopic records from a large, spatially and temporally well-constrained, Triceratops bonebed from the Upper Maastrichtian Lance Formation (eastern Wyoming. USA). These isotopic compositions allow to elucidate the palaeoecology of these large herbivores and their ecosystem in detail, as well as their habitat use, diet and possible migration. The δ18O signature from incrementally sampled Triceratops teeth reveal relatively low intra-tooth variation (average 1.3 ‰), comparable to contemporaneous dinosaur species as well as modern herbivorous mammals. Average δ13C values (−5.4 ‰) are somewhat higher than for modern C3 plant grazers, and hint towards complex interactions during carbon uptake by non-avian herbivorous dinosaurs. Calculated δ18O of drinking water (−14.8 ‰) combined with the local sedimentology of fine-grained siliciclastic deposits with high total organic and low carbonate contents strongly suggest a freshwater environment. Additionally, the combined average δ18O and δ13C Triceratops isotope signatures indicate a living environment intermediate between inland forests and coastal floodplains, expanding on earlier theories of ornithischian niche partitioning. Our robust dataset provides meaningful tests of habitat and palaeoecological hypotheses for Triceratops, and highlights the application of spatiotemporally well-constrained fossil remains.

Transitional shale quality and exploration potential: A case study from the Lower Carboniferous Jiusi Formation in northwest Weining, China

The organic-rich shale of the early Carboniferous Jiusi Formation in the Weining area, Southwestern China, has large geological gas reserves, making the Jiusi Formation another target after the Ordovician-Silurian marine shale in South China. The complex superposition of multi-stage tectonic phases since the Himalayan paroxysmal phase has induced a series of controversies in the sedimentology of the Jiui Formation, as only a few drillings were executed. In order to better understand the development potential of the shale associated with the Jiui Formation, five outcrops and a well (YS302) were studied, clarifying the sedimentary evolution of the formation, while two 2D seismic sections were used to analyze the regional structural styles. The result shows that the Jiusi Formation was significantly influenced by the synsedimentary extension of the northwestern margin of the Yadu-Ziyun-Luodian Fault, with the depositional center of the Jiusi Formation extending to well YS302 along a NW direction and asymmetrically thinning in a NE–SW direction. Fifteen lithofacies and three facies associations were identified, from tidal or delta settings to lagoon environments, finally turning into platform facies at the base of the Shangsi Formation. According to the geochemical analysis of 27 core samples and 37 outcrop samples, as well as the well YS302 logging interpretation result. The transitional Jiusi shale in the Weining area has a strong heterogeneity, with high total organic content (TOC) values being mostly provided by the surrounding coal seams. XRD analyses show that the minerals of the transitional shale are dominated by a high clay content (42 wt%). The content of water-sensitive minerals in Jiusi shale is also relatively high, with clay minerals dominated by an illite/smectite mixture (52.8%). When compared with the commercially developed Ordovician-Silurian marine shale, the Jiusi transitional shale shows relatively poor quality, related to dense bioturbation and terrestrial input affecting the preservation of organic matter. Therefore, the evaluation standard for marine shale is difficult to apply to the transitional Jiusi shale. The cumulative thickness of shale in YS302 worthy of shale gas development is nearly 100 m. Meanwhile, considering that the transitional shales are often interlayered with coal, the shale gas and coalbed methane can be developed together.

GENERATION AND MATURATION OF HYDROCARBONS IN CEPU AREA, CENTRAL JAVA

Production from the Cepu area occurs from the Tuban and Kawengan Formations. Studies of organie richness and thermal maturity of thirty eight comventional core sanples from four wells penetrating the units by use of Rock-esal pyrolysis method reveal that a high total organic content (0.30%) occurs in part of the Tuban Formation whereas a low total organie content (0.170.07%) is observed in the Kawengan Formation. Thermal maturity range is immature to maature with T-max ranging from 339°C to 435°C with the mature stage being confined to the Tuban Formation. The main kerogen type is structured kerogen (type III), with limited occurrence of unstructured kerogen (type II).Those results muggest that generution of gas occurred probably in the Tuban Fomation, vertically mi- grated and trapped at relatively shallow depths. It also implies that the more mature source-beds with marine kerogen could be found in the deeper sedimentary

Elastic properties and pore structure characterization of selected shales in the sungai Perlis beds, Terengganu, Peninsular Malaysia

Studied drill core of the Sungai Perlis Beds in the Terengganu State, Peninsular Malaysia, consists of a diverse suite of organic rich shale lithofacies at various subsurface depths. Lithofacies were delineated on the basis bedding thickness, mineralogy, and organic richness carried out by X-ray diffraction and (XRD) total organic content (TOC) analysis. Field-emission scanning electron microscopy (FE-SEM) analysis was carried out to identify the pore structure, range of pore sizes and mineral arrangement within each lithofacies unit Elastic geomechanical properties (Young’s modulus and Poisson’s ratio) were measured on core samples from each lithofacies unit using static and dynamic approaches. The identified lithofacies include moderate TOC massive argillaceous shale (MTOCMAS), high TOC massive argillaceous shale (HTOCMAS) and high TOC massive siliceous shale (HTOCMSS). FE-SEM analysis shows that pores in all the lithofacies are mostly intergranular, associated with phyllosilicate minerals, and ranges from <1 micrometer to approximately 8 micrometer. Static and dynamic elastic properties measurement shows that shale lithofacies having a high content of phyllosilicate minerals has a lower Young’s modulus and a high Poisson’s ratio value while lithofacies rich in brittle minerals has a higher Young’s modulus and a low Poisson’s ratio value. A good correlation exists between mineralogical brittleness index of the lithofacies and their plane strain modulus. The plane strain modulus is found higher in lithofacies having abundance of brittle minerals in the matrix suggesting that the high TOC massive siliceous shale (HTOCMSS) would preferably allow formation of dense hydraulic fractures, as observed in the CT scan analysis of triaxially fractured specimen, compared to argillaceous shale lithofacies.

Native and alien poplar plantations are important habitats for terrestrial orchids

Poplar monocultures are some of the most common short-rotation coppices. While they are most often considered of low environmental value, they have recently gained recognition for their multifaceted role in ecological engineering, such as carbon sinks, soil remediators or green energy producers. Nonetheless, the biodiversity of poplar plantations remains little known and largely overlooked. Here we conducted a systematic botanical survey of 232 poplar plantations within the Pannonian ecoregion (central Europe) in order to assess their plant diversity, with particular focus on terrestrial orchids. Our results highlight that almost 60% of poplar monocultures harbour terrestrial orchids, some with several thousand specimens. Overall, we documented the occurrence of 15 species of terrestrial orchids in the surveyed plantations, including taxa with limited distributions and a threatened conservation status. For instance, we report numerous new populations of Epipactis bugacenis and E. tallosii in poplar plantations, suggesting that the majority of these taxa occur in poplar monocultures within Hungary. We analysed and highlight soil chemistry and plantation characteristics that predict the occurrence and species richness of terrestrial orchids in poplar monocultures. The probability of orchids being present is highest in older and larger poplar plantations, characterized by high total organic matter content and high soil pH. We conclude that plantations of native and alien poplar harbour valuable plant communities, including terrestrial orchids and other vascular plants of significant conservation importance. Using the knowledge generated here, we recommend delaying or partial harvest of poplar plantations to increase their conservation potential.

Multidisciplinary analysis of hydraulic stimulation and production effects within the Niobrara and Codell reservoirs, Wattenberg Field, Colorado — Part 1: Baseline reservoir conditions

In the Wattenberg Field, the Reservoir Characterization Project at the Colorado School of Mines and Occidental Petroleum Corporation (Oxy) (formerly the Anadarko Petroleum Corporation) collected time-lapse seismic data for characterization of changes in the reservoir caused by hydraulic fracturing and production in the Niobrara Formation and Codell Sandstone member of the Carlile Formation. We have acquired three multicomponent seismic surveys to understand the dynamic reservoir changes caused by hydraulic fracturing and production of 11 horizontal wells within a 1 mi2section (the Wishbone Section). The time-lapse seismic survey acquisition occurred immediately after the wells were drilled, another survey after stimulation, and a third survey after two years of production. In addition, we integrate core, petrophysical properties, fault and fracture characteristics, as well as P-wave seismic data to illustrate reservoir properties prior to simulation and production. Core analysis indicates extensive amounts of bioturbation in zones of high total organic content (TOC). Petrophysical analysis of logs and core samples indicates that chalk intervals have high amounts of TOC (&gt;2%) and the lowest amount of clay in the reservoir interval. Core petrophysical characterization included X-ray diffraction analysis, mercury intrusion capillary pressure, N2gas adsorption, and field emission scanning electron microscopy. Reservoir fractures follow four regional orientations, and chalk facies contain higher fracture density than marl facies. Integration of these data assist in enhanced well targeting and reservoir simulation.

Fine-grained rock fabric facies classification and its control on shale oil accumulation: a case study from the Paleogene Kong 2 Member, Bohai Bay Basin

Lacustrine shale oil resources in China are abundant, with remarkable exploration breakthroughs being achieved. Compared to marine shale oil in North America, efficient exploration of lacustrine shale oil is more difficult; thus, selecting favorable layer and optimization zone for horizontal wells is more important. In this study, based on systematic coring of approximately 500 m fine-grained deposits of the Kong 2 Member, combining laboratory tests and log data, source rock geochemistry and reservoir physical properties, the favorable rock fabric facies for oil accumulation was analyzed and classified. First, the dominant lithologic facies, organic facies, and bed combination facies were determined based on mineral composition from logging, total organic content (TOC), and sedimentary structure. Secondly, 10 fabric facies were classified by combining these three facies, with 4 fabric facies were found to have high TOC content, high total hydrocarbon, and strong fluorescence features, indicating good shale oil enrichment. Thirdly, the distribution of the upon good fabric facies was identified to be located at the top of the Kong 2 Member, with evidences of seismic resistivity inversion, thermal maturity, structure depth, and strata thickness. And the favorable facies were found to be stably distributed lateral at the area of about 100 km2. High oil flow has been detected at this layer within this area by several wells, including horizontal wells. The exploratory study of fabric facies classification and evaluation provides a new research idea for lacustrine shale oil exploration and effectively promotes breakthroughs in lacustrine shale oil exploration in Bohai Bay Basin.

Examining the relationship between Tmax and vitrinite reflectance: An empirical comparison between thermal maturity indicators

For over 40 years Rock-eval pyrolysis data have been used to assess thermal maturity and source rock potential. There have been many published equations representing the transformation of Tmax to vitrinite reflectance (Ro) equivalence, but there has not been an attempt to investigate the empirical relationship using a large dataset. In this study, 33,732 approximately coincident measurements from 903 publications were utilized to test the applicability and practicality of Tmax, hydrogen index (HI), and production index (PI) as thermal maturity indicators. Additional sample metadata (sample type, lithology, organofacies, sample age, and other Rock-eval pyrolysis parameters) were also evaluated to ascertain if there were parameters that more frequently led to higher confidence measurements.There was a positive correlation between Tmax and Ro, but there is considerable scatter in the data. A stronger trend was revealed in the mean, median, and mode values for each Tmax versus Ro pair that can be represented by the equation Ro = (0.013 x Tmax) - 5.0 with a R2 value of 0.22, which may be an improvement upon previously published equations. There was a breakdown in the correlation between Tmax and Ro at the beginning of the dry gas window (Ro values ~1.5; Tmax ~500 °C), which was not unexpected since the S2 peak significantly decreases through the wet gas window. Tmax-derived thermal maturity estimates are therefore most reliable between the values of ~430 °C and ~500 °C. It was also observed that coals with high total organic content (TOC) and S2 values had the least amount of data scatter among the different source rock organofacies. This may be due to the higher initial S2 values and these samples having a more prominent S2 peak allowing them to yield more reliable Tmax determinations.

Bulk pyrolysis and biomarker fingerprints of Late Cretaceous Galhak Shale Formation in the northern Melut Basin, Sudan: implications on lacustrine oil-source rock

Organic-rich shale samples from the Late Cretaceous Galhak Formation were collected from one well location in the northern Melut Basin, Sudan, and analyzed by integrated organic geochemical and microscopic techniques. The study investigates the nature and preservation conditions of the organic facies and their relevance to petroleum resource potential. Judging from the high total organic contents (total organic carbon (TOC) > 2%), the analyzed Galhak shales are organically rich and include favorable source rocks. The organic richness in these shale sediments may be attributed to enhance the preservation of organic matter under suboxic conditions as implied from the n-alkanes and isoprenoid biomarkers. Biological markers, including of n-alkanes, isoprenoids, terpanes, and steranes, further suggest that the Galhak shale sediments were deposited in a relatively fresh lacustrine environment and received largely aquatic organic matter of plankton and bacteria with little terrestrial plant input. An abundance of aquatic-derived organic matter is consistent with types I and II kerogen as indicated by high Rock-Eval HI values of more than 400 mg HC/g TOC. The hydrogen-rich kerogen types I and II in the analyzed samples suggests an oil-prone source. According to the optical and geochemical maturity indicators, the organic matter in the Galhak oil shale is thermally immature; thus, they have not reached sufficient oil-window maturity for commercial oil generation. Therefore, the deeper parts of the Melut Basin, where the Galhak Formation reached high mature of peak-oil generation window, are recommended for further petroleum exploration and production.