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Shale oil and gas are currently the major fields of unconventional hydrocarbon exploration and development. The Fengcheng Formation (FF) shale in the Mahu Sag of the Junggar Basin is an alkaline lacustrine organic-rich shale with an extremely prospective shale oil potential. However, its strong heterogeneity and complex pore structure greatly influence the development of shale oil. It is significant to investigate the pore and geochemical characteristics of shale reservoirs for shale oil extraction. In this study, the pore structure and geochemical characteristics of FF have been investigated using core analysis, Rock-Eval pyrolysis, X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), mercury injection capillary pressure (MICP), low-temperature gas adsorption (LTGA), and X-ray computed tomography (X-ray CT). The results show that the shale of FF has moderate organic matter abundance, and the kerogen is mainly of Type II, which is now at the peak of oil generation. Shale minerals are mainly composed of carbonate (dolomite and calcite) and siliceous (quartz and feldspar) minerals, with extremely low clay mineral content. The pore types are mainly intergranular pores (inter-P), intragranular pores (intra-P), and microfractures associated with mineral particles. The pore space is contributed predominantly by micropores of 0.5–1.2 nm and mesopores of 10–50 nm, whereas macropores are underdeveloped. The pores are mostly ink bottle- and slit-shaped, and the pore connectivity is relatively poor. The pore development of shale in the FF is influenced by organic matter abundance, thermal maturity, mineral composition, etc. Organic matter content (TOC), thermal maturity (Ro), and carbonate minerals have a positive effect on pore development, and the pore volume (PV) increases with TOC, Ro, and carbonate minerals. While clay minerals show a negative effect, the PV decreases with clay minerals. Additionally, the influence of the clay mineral content on the pore morphology of shale should not be ignored. This study investigates the pore structure and geochemical characteristics of the alkaline lacustrine shale of FF in Mahu Sag, which is significant to deepen the understanding of alkaline lacustrine shale and to improve the production of shale oil. [ABSTRACT FROM AUTHOR]

• ASHP assisted solar heating system consisting of LFPSC coupled dual-source heat pump. • The performance and economic benefits of the LFPSC-ASHP system are revealed. • Sensitivity analysis of dynamic payback period of LFPSC-ASHP heating system. • Prove the feasibility of LFPSC-ASHP system for heating in cold regions of China. In rural areas of China, clean energy heating in winter is important for coal replacement. Winter temperatures in northwest China are usually below 0°Celsius and the heating season lasts for a long time, which is a huge expense for local residents. Solar energy, air source heat pumps(ASHP), and other energy-saving technologies are known to be effective in reducing heating expenses. However, due to the intermittent and unstable nature of solar energy itself, relying on solar heating is difficult to ensure stable heating and is certainly not economical. ASHP adds a financial burden to local residents due to the relatively high cost of winter heating. In response to the above problems, a new idea of ASHP coupled with solar energy for stable heating is proposed, and a large flat plate solar collector-air source heat pump(LFPSC-ASHP) heating system was established in Green Village, Lanzhou City. Experimental and simulation studies were conducted for this system to reveal the performance and economic benefits of the system for the heating season in three modes: solar collector heating, solar heat pump heating, and air source heat pump heating. The results show that the ASHP-assisted solar heating system is a great technical and economical improvement over the use of solar collectors or ASHP heating throughout the heating season. The LFPSC-ASHP system can continuously and stably heat the target building and has excellent economic and environmental benefits. In the operation of the whole heating season, the average collector efficiency of LFPSC is 0.42, the average COP of solar heat pump heating season is 3.75, and the average COP of ASHP heating season is 2.94. The solar fraction of the system in the whole heating season is 31.8 %, and the system energy efficiency ratio is 3.08. The system can save 7,690.5 CNY by running the whole heating season with a dynamic payback period of 6.58 years. ​Sensitivity analysis of the dynamic payback period shows that lower coal prices extend the dynamic payback period, while lower electricity prices and system costs reduce it. The primary energy saving rate of the system in the whole heating season is 67.5 %. The system can conserve 4,700.06 kg of standard coal in a whole heating season, which is equivalent to a reduction of 12,323.55 kg of CO 2. [ABSTRACT FROM AUTHOR]

Carbonate petroliferous basins usually develop fault-reservoir composite migration pathway systems. Accurate estimates of transport efficiency are important for locating oil and gas prospects, which is of considerable interest to oil explorers. The Cambrian Longwangmiao Formation in the Moxi–Gaoshiti area in the Sichuan Basin, the largest single monoblock gas accumulation in China with complicated migration pathway systems, was selected as an example to demonstrate the method. Using a combination of geologic, statistical, experimental data analyses, and quantitative characterization, a quantitative method for calculating the fault-reservoir composite transport efficiency is established for the first time. The results show that fault-reservoir composite migration pathway systems control the hydrocarbon accumulation. The analysis of data from 17 drilling wells using this method indicated a strong correlation between well productivity and composite transport efficiency, and the matching degree of actual and predicted results was as high as 83%. The best locations for oil and gas exploration are near areas with a high composite transport efficiency. Project planners can quickly find oil and gas prospects by matching calculated composite transport efficiencies to observed petroleum occurrences in a basin to avoid costly drilling mistakes. The method will have wide application in other carbonate basins around the world. • The fault-reservoir composite migration pathway controls hydrocarbon accumulation. • Quantitatively method for the composite transport efficiency is first established. • Composite transport efficiency is useful for location of oil and gas prospects. • Prospects for future drilling in the Moxi-Gaoshiti area of China are recommended. [ABSTRACT FROM AUTHOR]

Lacustrine shale oil resources are abundant and play important roles in maintaining a sustainable economy. The uncertainty in the movable oil content of organic-rich shales with strong heterogeneity is the greatest risk in their exploration. Various methods exist for movable oil content evaluation, but they present many challenges, especially insufficient accuracy, complicated test procedures, high costs, and limited application. In this study, an extensive review of the theories, techniques, and methods of movable oil content evaluation and their merits and demerits for lacustrine shales were conducted. Then, taking the lacustrine shale of the Paleogene Shahejie Formation (50.5–33 Ma) of the Dongpu Depression, Bohai Bay Basin, as an example, the multi-step Rock-Eval pyrolysis method combined with light hydrocarbon calibration was utilized to evaluate the movable oil content Subsequently, key factors controlling movable oil content were investigated, including organic matter richness, type, and thermal maturity, quartz content, clay mineral content, pore volume, and specific surface area. Both the systematic cluster analysis results and regression standardization coefficients indicate that the total organic carbon content, pore volume, and specific surface area are the main controls on movable oil content. Finally, a quantitative estimation model for movable oil content was established and validated using a statistical product and service solutions modeling. This study improves the understanding of shale oil enrichment laws and provides a novel and practical quantitative model for movable oil content estimation in lacustrine organic-rich shales across the world. [ABSTRACT FROM AUTHOR]