Characterization and evaluation of oil shale based on terahertz spectroscopy: A review

Oil shale is a fine-grained sedimentary rock rich in organic kerogen,which is a national strategic reserve resource and supplementary energy and shale oil and pyrolysis gas can be obtained through carbonization and pyrolysis.Due to the diversity of main components in oil shale and the complexity of the occurrence relationship between organic matter and minerals,the current understanding of the oil generation potential of oil shale and the dy-namic process of organic matter pyrolysis is still unclear,leading to the relatively backward level of its devel-opment technology.The development of new theories and methods for efficient utilization of oil shale resources has great strategic significance.The rotation and vibration frequency of macromolecules in oil shale occur in the terahertz(THz)band,so the THz optical parameters of oil shale can reflect the physical properties of kerogen.In this review,the experimental work progress in THz spectroscopy for characterization and evaluation of oil shale is provided.Oil shale is high anisotropic,resulting that the anisotropy in THz optical parameters strongly depends on the oil yield which is an effective selection for evaluating the oil yield to avoid the problem of environmental pollution in traditional detection.The heterogeneous distributions of organics on the oil shale surface,e.g.,the existence of kerogen-rich and kerogen-poor areas,was evaluated by THz amplitude imaging.In addition,the thermal THz analysis technology was developed to determine the pyrolysis process of kerogen and establish the pyrolysis model of kerogen,and the optimization of oil shale pyrolysis process was realized using THz parameters.Moreover,kerogen in oil shale displays a characteristic absorption peak in the THz range,which provides a new insight into the research of kerogen in the micro and nano scale.The pyrolysis oil shale at high temperature absorbs THz radiation strongly due to the decomposition of pyrite in oil shale.These recent works suggest that THz spectroscopy can realize rapid and non-contact detection of oil shale.At last,we propose the prospects and challenges of the THz technology in future as a new method for optimizing oil shale processing technology and improving the utilization efficiency of oil shale.

Terahertz-dependent evaluation of water content in high-water-cut crude oil using additive-manufactured samplers

The evaluation of water content in crude oil is of significance to petroleum exploration and transportation.Terahertz(THz) waves are sensitive to fluctuations in the dipole moment of water.However,due to the strong absorption of water in the THz range,it is difficult for the THz spectrum to determine high water content with the common sampler.In this research,micron-grade samplers for THz detection were designed and manufactured using additive manufacturing(AM) technology.Oil-water mixtures with water content from 1.8%to 90.6%were measured with the THz-TDS system using sample cells.In addition,a detailed analysis was performed of the relationships among THz parameters such as signal peak,time delay,and refractive index as well as absorption coefficient and high water content(>60%).Results suggest that the combination of THz spectroscopy and AM technique is effective for water content evaluation in crude oil and can be further applied in the petroleum industry.

Real-time monitoring the formation and decomposition processes of methane hydrate with THz spectroscopy

Gas hydrates are crystalline clathrate compounds comprised of hydrogen-bonded water cavities,consisting of guest molecules trapped in a lattice of polyhedral water cages under elevated pressures and low temperatures[1].The structures of the gas hydrates are closely related to the types and sizes of the guest species,and three distinct structures,including cubic structure-Ⅰ(sⅠ),cubic structure-Ⅱ(sⅡ),and hexagonal structure-H(sH),are known to form[2].Being expected as a kind of future energy resource,natural

Thermal spallation in rock revealed by ultraviolet laser-induced voltage

In the petroleum industry, perforation plays an important role in the exploitation of oil and gas and a considerable number of studies have been conducted with the objective of improving the recovery rates of oil and gas (1,2)Lasers have been used to drill holes in a wide variety of rock types with the advantages of feasibility, cost, benefits, and environmental impact as determined by the Gas Technology Institute [1].

Characterizing the rock geological time by terahertz spectrum

In the field of geology,it is necessary to get the information about the rock geological time,which includes absolute geologic age and relative geologic age .Tracing the evolutionary history of the earth is one of the research tasks of earth science.Time,space,material and motivation are the basic elements for studying geological processes and enviromnental evolution,and time is the basis for studying geological problems.A clear understanding of the interaction between the above elements will be able to clearly make sure the evolution of the earth and the conditions of rock formation.Nowadays,it is urgent to get the geochronological data of rocks for wide range comparison,so as to study the evolution trend and development rule of the earth's crust .

Application of THz technology in oil and gas optics

Fossil fuels currently satisfy^88%of China's energy demands.Oil-gas,known as the hydrocarbon occurred from various types of underground strata,is the most significant part of primary energy sources.Problems in oil-gas exploration,transportation and petrochemical affect the economic viability of the petroleum industry.Recently,the increasing complexity of stratigraphic condition and the fall in oil prices has made the situation more critical.Thus,questing for

Terahertz-dependent PM2.5 monitoring and grading in the atmosphere

Rapid industrialization and economic development have led to serious pollution in the form of fine particulate matter(PM2.5,particulate matter with a diameter of less than 2.5 μm). In China, PM2.5 has been one of the most debated topics in councils of government and issues of public concern. Terahertz(THz) radiation was employed to measure the PM2.5 in the atmosphere from September 2014 to April 2015 in Beijing. Comparison of the PM2.5 level from the website with THz absorbance revealed a significant phenomenon: THz radiation can be used to monitor PM2.5 in the atmosphere. During Asia-Pacific Economic Cooperation(APEC) 2014, "APEC Blue" was also recorded in a THz system. The relationship between absorbance and PM2.5 demonstrates that THz radiation is an effective selection for air pollution grading. Based on the absorbance spectra, the elemental compositions were studied by two-dimensional correlation spectroscopy(2 DCOS) in conjunction with X-ray fluorescence.Several single absorption peaks were revealed and caused by sulphate from coal combustion, vehicle exhaust emissions and secondary reactions. Furthermore, mathematical algorithms, such as the BPANN and SVM, can process the THz absorbance data and greatly improve the precision of the estimation of PM2.5 mass. Our results suggest that THz spectroscopy can not only reveal the component information for pollution source determination, but quantitatively monitor the PM2.5 content for pollution level evaluation. Therefore, the use of THz radiation is a new method for future air pollution monitoring and grading systems.

Non-contacting characterization of oil-gas interface with terahertz wave

Dear Editors,The interface of oil and gas has been a key issue in the process of oil and gas storage and transportation,which is a preparatory work to improve the transport efficiency and prevent oil and gas leaks.There are many methods to characterize the interface of oil and gas,such as the ultrasonic transducers and multi-electrode capacitance level sensors.Recently,the ap-

Characterizing the rock perforation process by laser-induced voltage response

In the petroleum industry,the exploitation of oil and gas is necessarily achieved by perforation,and a considerable number of research studies have been conducted with the objective of improving the recovery rates of oil and gas[1,2].New perforation methods are urgently needed to accelerate the development of energy resources.Drilling rock by laser is a non-contact process that can be used to drill holes in

Identifying PM2.5 samples collected in different environment by using terahertz time-domain spectroscopy

Particulate matter with the diameter of less than 2.5 μm （PM2.5） is the most important causation of air pollution. In this study, PM2.5 samples were collected in three different environment including ordinary atmo- spheric environment, lampblack environment and the environment with an air conditioning exhaust fan, and analyzed by using terahertz time-domain spectroscopy （THz-TDS）. The linear regression analysis and the principal component analysis （PCA） are used to identify PM2.5 samples collected in different environment. The results indicate that combining THz-TDS with statistical methods can serve as a contactless and efficient approach to identify air pollutants in different environment.