In this paper, the study focuses on the evolution mechanism underlying stress concentration formation in oil and gas transmission pipelines when subjected to various factors such as medium internal pressure and material property deterioration. It seeks to explore the relationship between the law of existing magnetism and stress changes induced by geomagnetism within these pipelines, as well as to develop a stress detection methodology. Theoretical models are compared and analyzed for the magnetic behavior under both unidirectional and complex stress conditions within oil and gas pipelines. Simulations are performed to assess the magnetic signal distribution across the pipeline wall, yielding insights into the behavior concerning the change law of magnetic flux signals under complex stress. In addition, a test platform is constructed to facilitate stress and magnetic flux testing on a model of an X80 pipeline exhibiting varying degrees of damage. These experiments aim to validate the theoretical stress detection model based on observed magnetic field changes. The results demonstrate a positive correlation between the existing magnetic flux signal and the applied stress, with a roughly linear relationship. This research establishes the feasibility of utilizing the existing magnetic flux signal to detect stress distribution within oil and gas pipelines.
Capturing carbon dioxide produced by chemical plants and storing it in the oil reservoir can not only supplement the formation energy of the oil reservoir, but also improve the recovery rate. Based on the actual situation of the associated gas in the CO2 injection area of an oilfield, this paper summarizes the influence of each main component on the two phase points of the associated gas through simulation calculations, and provides a theoretical basis for the setting of boundary conditions when the associated gas containing hydrocarbon impurities is reinjected. Studies have shown that as the content of light or heavy hydrocarbons increases, a two-phase zone will gradually appear. As the methane content increases, the temperature of the two-phase point gradually decreases, while propane, butane, pentane and hexane are the opposite. Compared with the pure carbon dioxide phase diagram, the two-phase point of the mixed gas containing methane enters the liquid phase region of carbon dioxide. The two phase points containing propane, butane, pentane and hexane move in the gas phase region of carbon dioxide. In particular, ethane has a small effect on the physical properties of associated gas, and when only ethane and carbon dioxide are contained, the two-phase point of the mixed gas has a low temperature and low pressure abnormal point. If the associated gas is directly reinjected, the pressure needs to be greater than 9.5 MPa to ensure that CO2 is pressurized to a supercritical state.
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