Proppant plays a critical role in the exploitation of oil and gas, especially in the development of nonconventional oil and gas resources. Proppants are small spheres that have adequate strength to withstand high closure stresses to keep cracks open; therefore, hydrocarbon flows smoothly into the wellbore. However, traditional proppants are prone to settling in hydraulic fracturing operations, which seriously affects the operation effect. To this end, ultralow-weight proppants have been extensively employed in the petroleum industry. One of the widespread forms of ultralow-weight proppant application in the oil and gas industry is related to light density. Ultralow-weight proppants will provide substantial flow paths with a considerably high propped surface area and remarkably reduce fine generation and scaling. This paper presents a comprehensive review of over 50 papers published in the past several decades on ultralow-weight proppants. The purpose of this study is to provide an overview of the current ultralow-weight proppant development status in raw materials, manufacturing process, performance characteristics, hydrophobic and lipophilic capabilities, and field application to promote the research of new ultralow-weight proppants. Lastly, this study analyzes the current challenges and emphasizes the development direction of fractured proppants.

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With the ratification of the Paris Agreement at the Paris Climate Conference, reducing carbon emissions has become a global interest. Coal is one of the main industries causing carbon emissions; thus, quantifying carbon emissions from coal mining is an important step in reducing these emissions. Firstly, based on the life cycle idea, in this paper, we define the Carbon Emission Boundary of the fully mechanized coal mining method. Secondly, the carbon emission accounting model (B-R model) of fully mechanized coal mining is established, which includes the total amount of carbon emissions and the carbon emissions of each mining link during the mining process. The Fifth-II mining area of the Jinda Coal Mine in Tengzhou City is taken as an example. We collect the relevant data on carbon emissions in the mining process of the Jinda Coal Mine, and the B-R model is used to obtain the carbon emissions in the mining process of this mining area. Finally, the feasibility of the B-R model is further verified according to the international authoritative carbon emission IPCC calculation method and the China Coal Production Enterprises Greenhouse Gas Emissions Accounting Methodology and Reporting Guide. The results show that the B-R model in this paper is feasible and that the greatest amount of carbon emissions arises from the coal breaking link and coal transportation, which provides a basis for other coal mines to calculate carbon emissions. The B-R model lays a foundation for coal mines to formulate a carbon emission reduction system.

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