Role Of Bitumen Research Articles

Modes of occurrence of tungsten in coals: a review

Relevance. The necessity to know the conditions and forms of W concentration in coals for solving a number of scientific and engineering problems at complex development of coal deposits. Aim. Complex estimation of W modes of occurrence in coal for development of measures for rational ecologically safe use of coal. Methods. Correlation analysis, scanning electron microscopy, infrared spectroscopy, coal group analysis, inductively coupled plasma mass spectrometry, instrumental neutron activation analysis. Results and conclusions. The modes of occurrence of W in coal were studied by a complex of methods. In the majority of W-enriched coal deposits, a negative significant correlation of its content in coal and coal ash with ash yield was found, indicating its association with organic matter. Using the method of coal group composition analysis, it was found that the main carrier and concentrator of W in the studied lignite deposits is organic matter. The contribution of the mineral phase in general in W-rich coals and in coals with its normal content does not exceed 20%, usually less than 5%. These conclusions are also confirmed by infrared spectroscopy data, according to which no more than 15% of the metal in the samples studied is associated with mineral phases. The association of W with high molecular humic acids predominates. In anomalously W-enriched lignites, the humic acid phase represents 76 to 88% of the gross metal content. The role of bitumen and low-molecular-weight humic acids in the balance of W is marginal at their different levels in the coals. Mineral phases of W are not characteristic of coal. Nano-microinclusions of scheelite, wolframite, hubnerite and ferberite were recorded as isolated occurrences. The main mineral phases are associated with Fe and Mn hydroxides, in which W is presented as a trace element in the amount of 1–5% together with other elements (Ge, As, etc.). In more metamorphosed bituminous and anthracite coals, authigenic mineral formations were found, represented by tungstite, phyllotungstite, native W and complex Fe-Mn-Ca-W-O mineral phases.

Composite fatigue failure of cold recycled material mixtures: new insights into the role of bitumen and cement

Composite fatigue failure of cold recycled material mixtures: new insights into the role of bitumen and cement

Study of the Mechanical Behavior of Organic Matters Contained in Source Rocks: New Insights into the Role of Bitumen.

Assessment of mechanical properties of organic matters contained in unconventional formations is needed to understand the geomechanics of source rocks. The organic matters are part of the source rock matrix, and they are made of kerogen and bitumen. Although the literature has some studies addressing the properties of kerogen and bitumen, no apparent attempts were made to address the mechanical behavior of organic matters as a combination of both. Isolation of organic matters from the rocks for experimental assessments has some risks of altering the original properties because of their delicate nature and their existence as micro- and nanoconstituents. Some computational approaches such as molecular simulation can serve as an alternative platform for the purpose of delineating organic matter properties including the mechanical ones. This work implements available 3D molecular modeling of kerogen and bitumen with different ratios to mimic organic matters that can be investigated for the mechanical properties. Upon the recreation of different configurations of organic matters molecularly, mechanical parameters such Young’s, bulk, and shear constants, as well as the stress–strain relationship for the elastic and plastic deformations were extracted. The mechanical behavior was closely monitored before and after saturation with a number of gases that are commonly found in subsurface formations such as methane, carbon dioxide, and nitrogen. The results revealed that the organic matters had a mechanical behavior envelope similar to what were reported for organic-based materials such as polymers. Moreover, the structures containing bitumen exhibited larger values of Poisson’s ratio, indicating less likelihood of them to degrade upon applied stresses. The presented data substantiate the importance of accounting for both bitumen and kerogen in modeling the petrophysics and the mechanical behavior of the organic matters.

Role of bitumen and NSOs during the decomposition process of a lacustrine Type-II kerogen in semi-open pyrolysis system

The purpose of this work is to investigate the generation characteristics of bitumen, NSO compounds, oil, and HC compounds during the artificial maturation of a lacustrine Type-II kerogen (which has not been given enough attention before) in order to determine its decomposition process. The analysis is based on the data itself, on the premise of jumping out of the generally accepted sequential reaction model. By taking the kerogen of the Chang 7 shale as an example, seven parallel experiments, in the temperature range from 300 °C to 420 °C were conducted on newly designed temperature-based semi-open pyrolysis system. The overall products are classified into oil and bitumen according to their phase, the C15+ fractions are classified into C15+sat, C15+aro and NSOs based on chemical compositions, and the NSOs are further classified into n-pentane NSOs and DCM NSOs according to Behar et al., (2008) and (2010). Results show that large proportion of oil is not merely a result of thermal cracking of bitumen, but also directly from the decomposition of kerogen itself. Both C15+sat and C15+aro are generated as soon as kerogen starts to decompose. It is not until the initial productivity of kerogen is basically exhausted that NSOs become the main precursor of hydrocarbons. The comparison with Behar et al. [2008, organic geochemistry 39, 1–22] further reveals that, for Chang 7 kerogen, initial decomposition of kerogen generates much more HCs than DCM NSOs. These results contradict the sequential reaction model described as: kerogen → bitumen → oil or kerogen → NSOs → hydrocarbons. Instead, they confirm the “alternate pathway” mechanism proposed by Burnham et al. [ACS symposium, 1989] in which hydrocarbons can be formed immediately from kerogen in parallel with NSOs and the formation of the two species are controlled by bond-breaking reactions that are independent of each other. This study adds geochemical insights into the decomposition mechanism of lacustrine Type-II kerogen.

Genesis and role of bitumen in fracture development during early catagenesis

Bitumen-bearing fractures and vugs were investigated in the highly organic-rich Jordan oil shale (JOS) of Late Cretaceous–Eocene age, which has potential as a highly fractured, unconventional hydrocarbon play. Bitumen is present as macroscopically visible deposits, and as inclusions in the cement of abundant natural fractures and adjacent vugs. The frequency of bitumen occurrence in fractures closely correlates with total organic carbon (TOC) and burial depth. Petrographical and organic-geochemical analyses on bitumen samples extracted from fractures and their host-rock matrix show that the fracture-filling bitumen comprises indigenous low maturity hydrocarbons derived from the surrounding organic-rich oil shale and has not migrated from a deeper source. Maturity indicators imply that the oil shale is in the pre-oil generation stage of early catagenesis throughout the investigated area, but with a regional increase in thermal maturity from west to east as the result of greater maximum burial depth. Bitumen mobilization in the host rock was mainly controlled by vertical loading stress acting on the non-Newtonian bitumen phase in load-bearing configurations in the organic-rich matrix. Bitumen fractures were developed by hydraulic fracturing as the result of fluid overpressure in the organic matter. Overpressured bitumen has acted as a fracture driver, generating bitumen veins in both the organic-rich mudstones and the adjacent chert and silicified intervals. Supplementary material : A summary of core data and photographs of the fracture bitumen and matrix bitumen are available at https://doi.org/10.6084/m9.figshare.c.4602290 Thematic collection: This article is part of the Naturally Fractured Reservoirs collection available at: https://www.lyellcollection.org/cc/naturally-fractured-reservoirs

THE ROLE OF BITUMEN IN THE COPPER MINERALIZATION FORMATION IN TERRIGENOUS-VOLCANIC ROCKS

The role of bitumen in the copper mineralization formation was found by analysis of the native copper deposits formation of in Volhyn, China and USA (Michigan) have established. Described mineral assemblages indicate changes in geochemical conditions during the bitumen and copper mineralization formation. Tectonic processes, which occurred in the rift environment, created favorable conditions for the ore-bearing solutions migration. It can be assumed that the original copper and hydrocarbons transfer carried in the fluid, and copper and bitumen in the rocks were formed at the same time. Epigenetic process of copper deposition from solutions occurred as a result of the reduction process under the action of gases (Corg, CH4).

The role of bitumen in strata-bound copper deposit formation in the Copiapo area, Northern Chile

In northern Chile, between 27 and 33°S, there are numerous deposits where residual petroleum is associated with Cu-(Ag) mineralisation (the most famous being El Soldado). All of these deposits are hosted by Lower Cretaceous volcanic or volcanoclastic facies along the axis of a former backarc basin. This close relationship suggests that the generation, migration and emplacement of hydrocarbons in the Cretaceous volcanic units is a regional process, associated with the evolution of the Cretaceous backarc basin and points to the importance of pyrobitumen as an exploration tool for similar Cu–(Ag) deposits. The present work analyses four small strata-bound copper deposits located along a north–south belt approximately 10 km east of Copiapo in northern Chile. These deposits are typically hosted by pyrobitumen-rich andesitic volcanic to volcanoclastic rocks intercalated with the marine carbonate Pabellon Formation, the youngest formation within the Chanarcillo Group. The strong genetic and spatial relationships between the pyrobitumen-rich lavas and the mineral deposits allow us to define this volcanic belt as the Ocoita-Pabellon Metallotect. Two hydrothermal events can be distinguished based on the mineralogical, textural, fluid inclusion and isotope data of ore and gangue and on the optical properties of residual petroleum. During the early event, petroleum was mobilised from the source rocks into the primary and secondary porosity of the lavas by Fe-rich hydrothermal fluids, which precipitated pyrite as an early sulphide phase. The second event is characterised by Cu-rich hydrothermal fluids, which induced three successive sub-stages of Cu-sulphide precipitation. The hydrothermal fluids chemically and thermally altered the first-stage bitumen, transforming it into pyrobitumen. The present work documents similarities between the Ocoita-Pabellon Metallotect and the El Soldado ore deposit and emphasises important differences. In the El Soldado host rocks, a petroleum reservoir existed prior to the arrival of the mineralising hydrothermal fluids, the framboidal pyrite was formed by assistance of bacteria, the S of the Cu sulphides was inherited from the pyrite, and the fluid source was basin connate-metamorphic brine. In the Ocoita-Pabellon Metallotect, the hydrocarbons were mobilised into the host rocks by hydrothermal fluids; the pyrite is epigenetic, the δ34S values of pyrite and copper sulphides are very different, with distinctive light δ34S signature of Cu sulphides (δ34S between −44.7 and −17.9‰), and the calculated δ18O of hydrothermal fluids indicates the participation of meteoric water in the late phases of the hydrothermal system.