Reservoir properties of coal seams such as gas and water effective permeabilities and gas content, as well as spatial distributions thereof, affect the success of gas production and CO2-enhanced gas recovery (EGR) with simultaneous CO2 sequestration. These properties change during production and injection operations due to variations in reservoir pressure, matrix shrinkage/swelling, and water saturation

Coal mine gas originates from the gas emission zone (GEZ) of the mine, as well as the longwall face and pillars. Gas emissions are controlled directly at the sources using horizontal or vertical boreholes drilled from surface or from the entries in advance of mining, or it is captured from the fractured and caved zones (gob) using ventholes during mining. The rest of the gas, especially that gas that

This review examines new techniques and applications of organic petrography in source-rock reservoir petroleum systems that have occurred along with development of the global ‘shale revolution’ in energy resources. The review is limited to techniques and instrumentation that provide spatially resolved information, typically at or below microscales, for dispersed organic matter occurring in situ in

The impact of natural intra-deposit heating on the δ13C signature, organic geochemistry, and petrology of coal and coal-bearing rocks characterised by various degrees of coalification and palaeoenvironments in the Upper Silesian Coal Basin, Poland, is elaborated. Reconstruction of palaeofire performed by heating experiments up to 400 °C in open and semi-closed systems with different heating regimes

Vitrinite reflectance (VRo; %) generally is considered the most reliable technique to determine the thermal maturity of sedimentary rocks. However, it is a time-consuming process to collect reflectance (Ro; %) measurements and is subjective to the interpretation of each trained technician, who must be able to discern between vitrinite and solid bitumen and other organic matter types. Inadvertent misidentification

Middle Permian coal from the Yongan Coalfield, Fujian Province, China, with a maximum vitrinite reflectance (VRmax) of 5.33%–8.95%, indicating a typical meta-anthracite stage, enables the study of differential graphitization of macerals. The composition and optical properties of macerals were analyzed using optical (under non-polarized light, polarized light with gypsum test plate (1λ), and cross-polarized

In-source solid bitumen was found in some cracks within the calcareous concretion in an overmature (Rbitumen > 3.5%) black shale of the Lower Cambrian Niutitang Formation from Songtao, Guizhou, China. The solid bitumen (grain size >2 cm) concentrated in source rock, which was formed by the transformation of petroleum-like substances that have not been expelled from source rock. This provides a substitute

Methanotrophic bacteria (MB) are an important group of microorganisms, involved in the greenhouse gas (GHG) cycles. They are responsible for the utilization of methane, one of the main GHGs, which is released in large amounts (via biogenic and abiogenic processes) during coal formation. This study aimed to determine the main factors affecting the distribution of the MB in two lignite-bearing series

This paper describes a viable nanoindentation-enhanced technique for screening hydraulic fracturing fluid additives via quantifying the effects of rock-fluid interactions on the mechanical properties of a clay-rich shale. Big data nanoindentation testing was conducted on both the intact shale and counterparts hydrothermally treated by four fracturing fluids, including water, KCl solution, and two surfactants

The Surat Basin, which is a major eastern Australian Coal Seam Gas (CSG) reservoir, produces gas from its Middle to Late Jurassic sub-bituminous Walloon Coal Measures, and shows variability in initial reservoir permeability across the basin. For a given lithostatic stress, the presence of vitrinite group or telovitrinite macerals within the coal can influence the fracture abundance within the coal

This paper investigates the hyper-enrichments of molybdenum (Mo), uranium (U), and vanadium (V) in the lower Paleozoic, Alum Shale of Denmark, Sweden, Norway, and Estonia. Molybdenum and U are mainly associated with organic matter and the highest contents are found in the Furongian part of the Alum Shale. This Furongian hyper-enrichment of Mo and U commenced with the Steptoean Positive Carbon Isotope

The well log inversion has been widely applied to forecast coal texture distribution due to its effectiveness and low investment. However, most research missed the low resolution of well logging data caused by the “boundary effect”, which make it difficult to identify thin layers. Here a method to improve the vertical resolution of logging curves by Wavelet Transform was applied. The original logging

Hydraulic fracturing is an effective approach to improve the productivity of coalbed methane (CBM) reservoirs. However, during hydraulic fracturing and CBM production, massive coal fines are deposited on the surface of proppants, leading to a sharp reduction in fracture conductivity. Herein, the detachment of deposited coal fines, caused by single-phase water flow in proppant packs, was investigated

Measuring the degree of organic matter (OM) alteration caused by uranium (U) irradiation is important in the effective evaluation of the hydrocarbon potential and thermal maturity of U-rich source rocks. This study investigates OM alteration in the Baltoscandian U-rich, lower Paleozoic Alum shale obtained from three research wells in the thermally immature parts of eastern Sweden and western Estonia

The sedimentary succession of 51-m consisting of a thin coal seam (1 m) and oil shale with a marlstone and carbonate-mudstone matrix of the Lower Carboniferous (Viséan) Emma Fiord Formation located on the Grinnell Peninsula, Devon Island, Arctic Canada was examined. The techniques used include reflected light microscopy, and instrumental neutron activation analysis (INAA) for elemental concentration

Rock-Eval S2 and S4 curves are commonly used to interpret active source rocks. In this work we report the formation of unusual, uneven, spiky S2 pyrograms from Rock-Eval of manually isolated vitrain bands from Mvb and Lvb coals. The spikes and unevenness in the S2 curves for coking-vitrains are interpreted to form from the release of gases or bubbles bursting from the melt during the pyrolysis stage

The thermal maturity from the early Paleozoic strata in Northwestern Argentina was studied using reflected light microscopy and Rock-Eval analyses. The graptolites were collected from the Acoite and Lipeón formations, from the Los Colorados section, Cordillera Oriental, and the Huaytiquina, and Muñayoc sections, Puna highland, corresponding to the "Coquena" Formation and the Cochinoca-Escaya Magmatic-Sedimentary

Apatite may be a common accessory mineral in coal seams, but interpretation of its origins can vary from syndepositional mineral detritus, early precipitation during diagenesis, and post coalification precipitation and replacement from hydrothermal or other fluids. It is hypothesised that paragenesis is reflected in the modes of occurrence in different stratigraphic units of the Late Permian in the

The Cretaceous Garbutt Formation shale and crude oils from the Cretaceous Chinkeh Formation in Liard Basin were subjected to geochemical analysis including biomarker fingerprinting. The Chinkeh oils are sweet light oils with API gravity and geochemical markers typical for the late stage oil window maturity. The oils show good correlation to the Garbutt shale extracts for their sterane compositions

Gas drainage is a popular method used for preventing gas outbursts in coal seams. However, quantitative assessment of the drainage remains a challenging task. In this study, we conducted a seismic time-lapse monitoring study at the No. 15110 working face in the Sijiazhuang coal mine to evaluate the effectiveness of the gas drainage process. The result reveals that there is a remarkable difference in

This paper presents the first detailed organic geochemistry and petrography of the Lower Cretaceous tight reservoir units from the Valdemar Field, Danish Central Graben. The Tuxen and Sola formation chalks and the interbedded argillaceous Munk Marl Bed and Fischschiefer Member, respectively, contain thermally immature marine Type II kerogen, mainly algal liptinites, degraded bituminite and late-oil

Early Silurian black shales are widely deposited over the entire Yangtze platform and their origin are highly controversial. In order to identify the controlling factors of these black shales formation, the mineralogy and geochemistry of the Early Silurian organic-rich shales from the Yangtze Platform, South China, were investigated by using an optical microscopy, X-ray diffraction analysis, X-ray

This paper presents the application of a thermal-hydraulic-chemical model to simulate (1) a laboratory small-scale borehole combustion experiment using high-ash-content coal and (2) an ex-situ large-scale UCG experiment using low-moisture-content hard coal. The focus was to study temperature development, syngas composition, pore structure alteration of coal, and cavity growth pertinent to the UCG process

Although the geochemical and mineralogical characteristics and provenance of Permian-Triassic boundary (PTB) widespread volcanic ashes from southern China have been well investigated, the volcanic ashes just prior to the end-Permian mass extinction (EPME) have rarely been studied. This paper presents the mineralogical and geochemical compositions of volcanic ashes from the latest Permian coal-bearing

Sodium Hypochlorite (NaClO) oxidation has been reported as a promising method for coal seam permeability enhancement and extracting valuable hydrocarbons from coal. Different coal macerals, particularly vitrinite and inertinite behave differently in NaClO with varying reaction extent exhibited. The reasons for variability are not completely understood. This study aims to reveal the controlling factors

The Harmancık Basin, in the north-easternmost Miocene graben in western Anatolia, hosts a 12.6-m-thick coal seam located in the Keles coalfield, in which coals are being exploited by open-cast mining methods. Syngenetic clinoptilolite/heulandite-type zeolite formation in the upper part of coal seam and carbonaceous clayey diatomite as a roof rock have been identified for the first time, and the palaeoenviromental

Nonlinear stress-strain behavior and failure envelopes are critical rock mechanical data for gas reservoir evaluation and development, especially when the basic rock properties are measured under actual reservoir conditions that include pore pressure. For coalbed methane (CBM) reservoirs, the mechanical properties of coal may be different under actual reservoir conditions because the in situ coal is

Moisture in shales under reservoir conditions adversely affects gas adsorption and nanoporosity and is also likely to impact on the contribution that kerogen makes to the methane adsorption capacity. To investigate these phenomena, two over mature shales from the Wufeng-Longmaxi Formation, south of the Sichuan basin, and their kerogens isolated by demineralisation were investigated dry and at 95% relative

The factors controlling Re-Os systematics and potential for geochronology in organic-rich sedimentary rocks deposited in fully terrestrial to paralic environments are not well understood. Here we present Re-Os, bulk pyrolysis and sulfur data for coals and coaly mudstones from the Late Cretaceous Rakopi and North Cape, Paleocene Farewell and Eocene Mangahewa formations, Taranaki Basin, New Zealand,

Is the signature of the original plant communities preserved in coal, or is that signature overprinted by depositional and diagenetic processes? To address this question, Pennsylvanian coals from the Illinois and Appalachian basins were compared to Cretaceous, Paleocene, and Eocene coals of comparable coalification levels as shown by vitrinite reflectance. Three reflectance intervals—0.52–0.55, 0.58–0

This paper introduces the development of a new predictive model in support of proppant injection in naturally fractured coal seam gas (CSG) reservoirs. In the proposed model, the finite element method (FEM) is used for the prediction of proppant embedment and elastoplastic deformation of the coal. The lattice Boltzmann method (LBM) is applied to the modelling of fluid flow through propped fractures

Results are presented on the relationships between the vitrinite reflectance VRo, the Tmax temperatures determined with Rock-Eval pyrolysis, and the smectite (S) indices representing the percentage of smectite in the mixed-layer illite-smectite (I/S) from claystones. Samples locations are recovered from the Polish part of the Outer Carpathian fold-and-thrust belt. Organic indices show thermal maturities

Samples for inclusion analysis were collected to investigate reasons for carbon isotope rollover in the Yan'an gas field (YAGF). Homogenization temperature of fluid inclusions, constituents and carbon isotope of gases in fluid inclusions were measured. Geochemical parameters of gas in wells and fluid inclusions in the northern gas fields (NGF) and YAGF were compared. The results show that geochemical

Water sorption provides a great approach to understand water-shale interaction. In this research, water sorption isotherms of fourteen Wufeng-Longmaxi shale samples collected from the eastern Sichuan Basin of China were generated and then interpreted by classical sorption models. The sorption behavior of water and its relationship with pore structure, organic/inorganic composition, and temperature

Synthetic coal ash bearing 560 ppm europium oxide, blended with aluminum phosphate, was heat treated above its melting temperature and crystal evolutions with respect to europium concentration under controlled cooling were studied. The sample in a boat crucible was subjected to a temperature gradient of 100 °C across it to cause zone refining effects on crystallization behaviors in the melt (slag)

The study of coals affected by magmatic intrusions is important from a geological point of view, in order to understand how heat and magmatic fluids could affect the organic and inorganic fractions as well as the properties of the coals. These fluids may lead to an enrichment of trace elements and heavy metals of environmental concern or serve as unconventional sources of critical elements. Therefore

The Cretaceous Hue Shale is a condensed mudstone section of the Brookian sequence with type II and type III kerogen, and it is one of the major source rocks that fill the world-class conventional oil fields on the North Slope, Alaska. The bottom section of the Hue Shale is referred to as Gamma Ray Zone (GRZ) or Highly Radioactive Zone (HRZ) and believed to be the most organic-rich section. The thermal

Amorphous organic matter (AOM or bituminite) is a major oil-prone liptinite maceral in black shales that can be classified into two main types: low-reflectance AOM and micrinized AOM. In this study, we investigated the petrographic and chemical structure characteristics of these two types of AOM and discussed their origin based on 15 marine black shale samples from the Illinois Basin, including 5 samples

Coal mining in China is continually increasing, and the associated emitted coal mine dust is of growing environmental and occupational concern. In this study, deposited coal mine dust (DD) was analysed in three different regions of an active, highly-volatile bituminous open-pit coal mine in the Xingjian Province, Northwest of China: coal working fronts, tailings handling sites, and road traffic sites

The coal-hosted Ge deposit (Early Cretaceous) at Wulantuga, Inner Mongolia, northern China, is one of the largest Ge deposits in the world. Although the origin, modes of occurrence, and spatial distribution of Ge in this deposit have been investigated by several studies, the provenance and pathways of Ge from the source to the deposit are largely unknown. In this study, we investigated the 87Sr/86Sr

Occasionally, distinctive plant fragment (PF)-concentrated sandstone beds are found in the turbiditic sequence of the Miocene Kawabata Formation (Yubari, central Hokkaido, Japan) deposited in a foredeep basin. Sedimentological and organic geochemical analyses were carried out on the PF-concentrated sandstone bed to investigate the transport and depositional processes of the abundant PFs in the basin

Airfall volcanic ash deposited in the form of tuff layers is widely distributed in oil-shale bearing basins in western Liaoning Province, northeast China. In order to investigate the impacts of volcanic ash on algal productivity and the formation of organic-rich oil shales, the organic petrology and organic geochemistry of lacustrine sediments of the Lower Cretaceous Jiufotang Formation were investigated

An essential but missing component in our understanding of microbial interactions leading to coal bed methane (CBM) formation lies in the relationship between coal and coal-adhering microorganisms. Here, we explored the influence of surface physico-chemistry on the microbial cell attachment on coal, utilising a known coal-oxidising bacterium P. fluorescens Pf-5 as a model. Based on the interfacial

Raman spectroscopy has been applied in numerous sedimentary formations to infer thermal maturity of mostly Type-II kerogen in organic-rich mudrocks. Robust correlations have been established between the Raman spectroscopic signal and vitrinite reflectance equivalents (%VRE) of the organic matter. Herein, traditional evaluation methods, organic petrography and geochemistry, were applied in addition

Upper Jurassic Naokelekan Formation, being part of the intercepted strata of the well-known Miran oilfield in Kurdistan region of Northern Iraq, has been previously extensively evaluated as a potential/effective source rock, mainly by means of organic geochemistry. In the present study, a total of 60 samples were collected from four Naokelekan Fm. outcrops, those of Banik, Galy-Derash, Barsarin and

Lacustrine oil shale is an important unconventional energy source in China. Previous exploration has mainly focused on stable deep lake deposits, whereas lacustrine oil shale layers in unstable sedimentary settings, which are widely distributed in Cretaceous strata, having received little research attention. The present paper is focused on the Aptian Jiufotang Formation in the Beipiao Basin. In order

A suite of six naturally graphitized coals were separated by density-gradient centrifugation (DGC). The density profiles of anthracite and meta-anthracite samples show an average density increase from 1.50 g/mL to 1.93 g/mL with increased rank. Components of partially graphitized coals were separated into two distinct density peaks: a low-density peak at ~1.82 g/mL, and a high-density peak at ~2.0 g/mL;

A comprehensive geochemical and petrographic study was performed on 23 clay-rich shale samples collected from 18 wells drilled in the mid-western part of the Ordos Basin to investigate the characteristics and thermal maturity of organic matter as well as the paleo-depositional environment of the Chang 7 Member within the Triassic Yanchang Formation. The samples are characterized by moderate to very

Mining-induced microseismicity is widely considered as a result of slippage of pre-existing critically stressed fractures caused by stress perturbations around an advancing face. An in-depth analysis of the recorded microseismicity associated with longwall top coal caving mining at Coal Mine Velenje in Slovenia has been previously carried out and reported by the authors. It has been concluded that

Gas and water geochemistry in the No.2 coal reservoir of the Yanchuannan CBM block in the southeastern Ordos basin reflects a complex interaction of tectonic, hydrodynamic, thermogenic, and biogenic processes. Stable isotope and component analyses of gas and water samples from the No. 2 coal seam of 17 CBM wells were performed to determine the correlations between stable isotopes of gases and co-produced

The stable isotopic (δ34S, δ18O, δ2H) composition of mine waters has been examined from coal and metal mines, of varying depth, in Spain (Asturias), the UK (north Derbyshire/Yorkshire) and Poland (Bytom, Upper Silesia). δ18O and δ2H data confirm a meteoric origin for all waters. The mine waters have elevated sulphate concentrations relative to recent meteorically-derived groundwaters and have elevated

Three Miocene-age coal seams - a lower seam (kM2, subbituminous), a middle seam (kM3, subbituminous), and an upper seam (kP1, lignite) - in the Kınık coalfield, located in the southwesternmost part of the Soma Basin in western Turkey, and factors controlling mesoporosity and microporosity characteristics, were investigated using low-pressure N2 and CO2 adsorption techniques, respectively. In addition

Globally, there is significant economic interest in shale gas as a hydrocarbon resource. The success of unconventional shale gas exploration in the United State of America (USA) has raised interests for potential shale gas development in the Karoo Basin of South Africa. The Karoo Basin technically recoverable shale gas resource is estimated to be 13 Tcf, with 19–23 Tcf recoverable free gas. Due to