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During the Meishucun period of the Early Cambrian, a large-scale phosphorus formation event occurred on the Upper Yangtze platform. As the product of this event, the sedimentary environment and formation mechanism of phosphorite remains elusive. In order to better understand the sedimentary environment and formation mechanism of phosphorite enrichment, we investigated the geochemical characteristics of phosphorite in Maidiping Formation of Lower Cambrian in Huangjiaping area of Mabian County. The results show that: ΣREE has significant positive correlation with P2O5, and (La/Yb)N and (La/Sm)N ratio are 0.98 ~ 1.61 and 0.93 ~ 1.39, indicating that REE enrichment is affected by early diagenetic adsorption, and the phosphorite retains the original fractionation characteristics of REE. Obvious negative Ce anomalies (average Ce/Ce* is 0.44) and the absence of framboid pyrite in the phosphorite indicating that the phosphorite were deposited under oxic/dysoxic conditions. The high Y/Ho ratio (mean 65) is consistent with the Y/Ho ratio of modern oxygen-containing seawater, indicating that phosphorite is derived from the original oxic seawater. The weak negative Eu anomaly (Eu/Eu* mean value is 0.9) indicates that the formation of phosphorite is not affected by hydrothermal activity. The REE distribution pattern is “hat type”, indicating that the formation of phosphorite is controlled by Fe-redox pump at sea-sediment interface. In combination with the above findings and combined with the highly stratified redox ocean structure and the intensive upwelling in the early Cambrian, the phosphate released during the redox of FeOOH was transported into the shallow water. In the shallow underground burial, phosphate is enriched by biodegradation and reductive release of FeOOH, and finally phosphate and Ca2+ are combined to form apatite, which is continuously enriched and ore-forming.

Despite the abundance of shale-oil and tight-oil reserves in the Fengcheng Formation within the Mahu Sag, exploration and development efforts for both types of reservoir are still in their early stages. A comprehensive examination and comparison of the pore structures of these reservoirs can establish rational classification and evaluation criteria. However, there is a dearth of comparative analyses focusing on the pore structures of shale-oil and tight-oil reservoirs within the Fengcheng Formation. This study addresses this gap by systematically analyzing and comparing the pore structures of these reservoirs using various techniques such as X-ray diffraction (XRD), scanning electron microscopy (SEM), low-temperature nitrogen adsorption, and mercury intrusion capillary pressure experiments (MICP). The results show that the shale oil within the Fengcheng Formation exhibits a higher content of carbonic acid compared to the tight-oil samples. Furthermore, it demonstrates smaller displacement pressure and median pressure, a larger sorting coefficient, and superior permeability in contrast to tight oil. Notably, the shale oil within the Fengcheng Formation is characterized by abundant striated layer structures and micro-fractures, which significantly contribute to the microstructural disparities between shale-oil and tight-oil reservoirs. These differences in microstructures between shale oil and tight oil within the Fengcheng Formation in the Mahu Sag region delineate distinct criteria for evaluating sweet spots in shale-oil and tight-oil reservoirs.

Although the aging asphalt and its regeneration were researched by many researchers, the poor low-temperature performance of regenerating asphalt has still not been solved yet. In this project, the composite technology of regeneration and modification will be used to solve the problem mentioned above. Through the investigation and analysis on the composite mechanism of regeneration and modification for aging asphalt, the objective of the project attempts to explore a method for the synchronized recovery of high- and low-temperature performance of aging asphalt. The research results show that the single regenerating technology cannot fully recover the low-temperature performance of aging asphalt, and the composite technology of regeneration and modification can make the performance of aging asphalt recovery well. The indexes of aging asphalt after composite regeneration and modification have been recovered, which are better than the indexes of 90# asphalt (25°C penetration is 80–100/0.1 mm) and close with the indexes of styrene-butadiene-styrene (SBS) modified asphalt. The project has demonstrated that the composite technology of regeneration and modification can make the high- and low-temperature performance of aging asphalt recovery well. The research results can obtain better economic and social benefits.