The carbon storage service of terrestrial ecosystems has an veritable impact on the global carbon cycle and, in turn, on global climate change. Hence, both assessing and predicting the impact of land use changes on carbon storage are necessary to reduce carbon emissions and mitigate climate change. Therefore, using integrated valuation of ecosystem services and tradeoffs (InVEST) model with remote sensing data, this study systematically analyzes the land use/cover change (LUCC) and the carbon storage response characteristics of land types in Henan Province, China in the 1990–2020 period. The study also uses patch-generating land use simulation (PLUS) model to predict the LUCC and carbon storage in Henan Province from 2023 to 2050 under different scenarios, including Business as Usual (BAU), Ecological Conservation (EC), and Urban Development (UD) scenarios. The following results are noted: (1) The LUCC mainly comprises the conversion of farmland to construction land. Presently, Henan Province's carbon storage is found to have decreased by 339.72 Tg due to LUCC, which is characterized as "high in the west and low in the east." (2) Regarding the three aforementioned scenarios, the province's construction land is predicted to increase to its greatest extent under the UD scenario. Under the EC scenario, its woodland and farmland areas will be effectively protected. Therefore, the highest level of carbon reserves will likely be found in the EC scenario, followed by that in the BAU scenario, while the lowest level of carbon reserves should be seen in the UD scenario. The carbon reserves of Henan Province in 2050 will be 312.07 Tg, 233.43 Tg, and 394.49 Tg lower than that in 2020 under the BAU, EC, and UD scenarios, respectively. In sum, this study provides the scientific basis of the decisions aimed at the facilitation of low-carbon development, the optimal utilization of land spaces, and the development of an ecological civilization in Henan Province.
Summary Fracturing is the necessary means of tight oil development, and the most common fracturing fluid is slickwater. However, the Loess Plateau of the Ordos Basin in China is seriously short of water resources. Therefore, the tight oil development in this area by hydraulic fracturing is extremely costly and environmentally unfriendly. In this paper, a new method using supercritical carbon dioxide (CO2) (ScCO2) as the prefracturing energized fluid is applied in hydraulic fracturing. This method can give full play to the dual advantages of ScCO2 characteristics and mixed-water fracturing technology while saving water resources at the same time. On the other hand, this method can reduce reservoir damage, change rock microstructure, and significantly increase oil production, which is a development method with broad application potential. In this work, the main mechanism, the system-energy enhancement, and flowback efficiency of ScCO2 as the prefracturing energized fluid were investigated. First, the microscopic mechanism of ScCO2 was studied, and the effects of ScCO2 on pores and rock minerals were analyzed by nuclear-magnetic-resonance (NMR) test, X-ray-diffraction (XRD) analysis, and scanning-electron-microscope (SEM) experiments. Second, the high-pressure chamber-reaction experiment was conducted to study the interaction mechanism between ScCO2 and live oil under formation conditions, and quantitively describe the change of high-pressure physical properties of live oil after ScCO2 injection. Then, the numerical-simulation method was applied to analyze the distribution and existence state of ScCO2, as well as the changes of live-oil density, viscosity, and composition in different stages during the full-cycle fracturing process. Finally, four injection modes of ScCO2-injection core-laboratory experiments were designed to compare the performance of ScCO2 and slickwater in terms of energy enhancement and flowback efficiency, then optimize the optimal CO2-injection mode and the optimal injection amount of CO2 slug. The results show that ScCO2 can dissolve calcite and clay minerals (illite and chlorite) to generate pores with sizes in the range of 0.1 to 10 µm, which is the main reason for the porosity and permeability increases. Besides, the generated secondary clay minerals and dispersion of previously cemented rock particles will block the pores. ScCO2 injection increases the saturation pressure, expansion coefficient, volume coefficient, density, and compressibility of crude oil, which are the main mechanisms of energy increase and oil-production enhancement. After analyzing the four different injection-mode tests, the optimal one is to first inject CO2 and then inject slickwater. The CO2 slug has the optimal value, which is 0.5 pore volume (PV) in this paper. In this paper, the main mechanisms of using ScCO2 as the prefracturing energized fluid are illuminated. Experimental studies have proved the pressure increase, production enhancement, and flowback potential of CO2 prefracturing. The application of this method is of great significance to the protection of water resources and the improvement of the fracturing effect.
'/%3e%3cuse xlink:href='%23a' transform='rotate(23.036 .093 25.536)'/%3e%3cuse xlink:href='%23a' transform='rotate(45.87 1.273 16.18)'/%3e%3cuse xlink:href='%23a' transform='rotate(69.945 .996 12.078)'/%3e%3cuse xlink:href='%23a' transform='rotate(20.66 -19.689 31.932)'/%3e%3c/svg%3e)